|Publication number||US2878020 A|
|Publication date||Mar 17, 1959|
|Filing date||Dec 16, 1949|
|Priority date||Dec 16, 1949|
|Publication number||US 2878020 A, US 2878020A, US-A-2878020, US2878020 A, US2878020A|
|Inventors||Robinson Roy H|
|Original Assignee||Robinson Roy H|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (27), Referenced by (52), Classifications (15)|
|External Links: USPTO, USPTO Assignment, Espacenet|
March 17, 1959 R. H. RoislNsoN 2,373,020
RAcxE'rs For: BATTING GAMES Filed Dec. 16, 1949 3 Sheets-Sheet J7A um M..
IN V EN TOR.
March 17, 1959 R. H. ROBINSON 2,878,020
RACKETS FOR BATTING GAMES Filed Dec. 16, 1949 5 Sheets-Sheet 2 Fi .14 21 y? 44 4; 22 7 z 44 P17448 Z917 12 March 17, 1959 R. H. ROBINSON l 2,878,020
` RAcKE'Ts FOR. BATTING GAMES Filed Dec. 16 1949 3 Sheets-Sheet 5 United States Patent fic 21,878,020 Patented Mar. 17, 19519 RACKEI FOR BATTING GAMES Roy H. Robinson, Chicago, Ill. Application December 16, 1949, Serial No. 133,423y i 26 Claims. (Cl. 273-73) The purpose of the invention is to provide an improved racket for tennis, badminton, squash and kindred t co-pending application No. 492,914, tiled June 30, 1943 (which matured into Patent No. 2,593,714, issued April 22, 1952), as applied to my racket frame construction. This application is a continuation-in-part of my prior application Serial No. 492,914.
One of the primary objects of my invention is to provide means for resisting torque in racket frames and the torsional stresses set up by ball impacts and particularly to resist such strains arising in a frame employing my unique inturned arch disclosed in my aforesaid application Serial No. 545,630.
A further object is to provide special means for more effectively applying my unique racket head shape, with its inturned arch, to the popular laminated wood frame construction common to present-day racket construction, and makesame more effective. f n
A further purpose is to eliminate the deadness found in the outer portions of racket heads and so produce more equally resilient return of the ball from such points as compared with the central and lower portions of the head.
A further objective is to enhance the resilience in my uniquely functioning outer nturned arch construction and provide against delaminating stresses which 4are set up in and adjacent this arch, particularly in relation to laminated frames embodying wood and subject to enlargement and distortion from atmospheric moisture absorption.
A further objective is to avoid the uneven distortion arising in orthodox wood frames from the dissimilar slotting required on the opposite sides of the head framing for the necessary protection of the Stringing, resulting in one side of the head frame being weaker than the other, with unbalanced resistance to the heavy Stringing pressure causing the frame eventually to warp to an unsymmetrical shape.
A further objective is to provide a new manner of laminating a frame and to better provide for stresses in all directions and more effectively hold the laminations together.
Further objectives are to simplify the manufacturing, minimize its cost and introduce new materials into the frame and novelly dispose and combine samekto great advantage and for new functional purposes.
With the above `and other objects in view, the invention consists of certain novel combinations h and arrangements of parts, the' relation of which will be more thoroughly Z established in the following description particularly emphasizing and pointing out the same.
In the accompanying drawings:
Fig. 1 is a front elevation of a racket built in accordance with my invention.
Fig. 2 is a side elevation of the racket of Fig. l.
Fig. 3 is a fragmentary diagrammatic View of the underside of the outer end of the frame of a racket having such a general shape as that of Fig. 1 and indicating the approximate pattern of checking in the lacquer finish resulting from stressing the frame in play.
Fig. 4 is a similar fragmentary diagrammatic view of the top side of the lower portion of the frame of Fig. 1, above the throat, likewise indicating the stress pattern of the checking of the lacquer at that point.
Fig. 5 is a diagrammatic side elevation of a racket frame indicating, in exaggerated form, the resultant shape of a frame of this type when distorted by torsional stresses, when not properly built to resist same.
Fig. 6 is a diagrammatic side elevation showing the approximate arrangement of the grainlongitudinally -in wood reinforcements applied to the frame in Fig. l.
Fig. 7 is a fragmentary plan view of a tubular reinforcement forming part of a laminated frame, Fig. 1, with a portion cut away.
Fig. 8 is a fragmentary plan view of a strip of alternate reinforcement for the frame of Fig. 1, with portions cut away.
Fig. 9 is a fragmentary plan view of reinforcement similar to that of Fig. 8 when made up in curved form to conform to the faces of the racket frame, and with portions cut away.
Fig. lO is a fragmentary plan view of a modified form of reinforcement in lieu of that of Fig. 8, and with portions cut away.
Fig. l1 is a diagrammatic frame cross section, indicating in principle the cross sectional area of a normal laminated wood frame of orthodox construction as compared with the reduced area made possible when modified to conform to applicants stronger frame construction, as in Fig. 1, for example.
Fig. 12 is a fragmentary cross section-al perspective view of the frame of Fig. l, taken on line 12-12.
Fig. 12a is a perspective view of the throat wedge of the frame of Fig. 1, and indicating the preferred grain A direction in each of its laminations as made in glued 3- ply wood construction.
Fig. 12b is a fragmentary cross sectional view of the frame of Fig. l, taken at the throat on the line 12b-12b. Fig. 12C is a fragmentary cross sectional perspective View showing an alternate form of the frame of Fig. l2
with the overlay laminations having extending edges forming a protective channel for the strings and increasing frame strength.
Fig. 13 is a fragmentary plan view of the laminated face reinforcements on the opposite faces of the throat area, etc., of the frame of Fig. 1 and with portions cut away.
Fig. 14 is a fragmentary enlarged front elevation of the outer end of the frame of Fig. 1, and with portions cut away.
Fig. 15 is a fragmentary plan view of the frame portion of Fig. 14, with portions cut away.
Fig. 16 is a sectional perspective view, taken on line 16-16 of Fig. 14, and with portions cut away.
Fig. 17 is a sectional perspective view, taken on the line 17 17 of Fig. 14.
ment extending under the arch soit perspective view, taken on line portions cut away.
Fig. 20 is a fragmentary front elevation of a modied form of the racket of Fig. l.
Fig. 21 is a perspective view of the reinforcing member adhesively bonded to the soiiit of the arch at the outer end of the racket frameof Fig. 20. i
Fig. 22 is a fragmentary plan view of the laminated face reinforcement forming the opposite faces of the frame of Fig. 20 in its lower portion, and with portions cut away.
Fig. 23 is a fragmentary plan view of a modified form of laminated face reinforcement similar to that of Figs. 13 and 22, and with portions cutaway.
Fig. 24 is a fragmentary sectional perspective view of a modified form of frame construction and particularly with reference to a modified means of string protection.
Fig. 25 is a fragmentary plan view of the outer string protective strip of the frame of Fig. 24 and the lay-out for the string slots at the outer extremity of the frame with particular 'reference to avoiding the customary frame distortion accompanying orthodox slotting.
Fig. 26 is a perspective View of a modified reinforcing member in lieu of that of Fig. 2l together with fragmentary portions of cantilever lamination frame construction adhesively bonded under same.
Fig. 27 is a front elevation of an alternative form of reinforcement for the ends of my inturned arched frame and indicating its relation to the frame in dotted lines in connection with being adhesively bonded thereto.
Fig. 28 is a plan view of the reinforcement of Fig. 27 and in relation to said frame.
Figs. 29 and 30 are fragmentary front elevations of modified forms of the frame end similar to Fig. 14.
Figs. 31 to 42, inclusive are fragmentary sectional perspective views of modified forms of frame construction taken transversely of the frame, or perspective views (3l, 33 and 35) of assemblage of material preparatory to press forming, and press forming indicated in Fig. 32 with sectional perspective of frame section.
Fig. 43 is a plan view of a racket forming and integrating press for the frame of Fig. l and the like, with portions cut away and showing means for pre-stretching filament reinforcing.
Fig. 44 is a fragmentary cross sectional view of the press for shaping and adhesively bonding and compressing the outer opposed filament face laminations on the pre-formed edgewise laminated core for the frame of Fig. l and the like, shown in cross section in the press. Referring in detail to the drawings, Figs. l and 2 represent a tennis racket formed with my uniquely shaped head disclosed in my co-pending application, Serial No. 545,630, combining my acorn-shaped head with my inturned arch 2 at its outer extremity. The racket has the width of its head at this outer extremity narrowed in Yrelation toits broader base at the throat as formed by the sharply out-turning shoulders 3 of the frame, this unique form being in distinct contrast to the conventional oval rackets now in general use and having equally distinct advantages over same which have been emphasized in said co-pending application. In Figs. l and 2, I have adapted this novelly shaped frame to the Wood laminated frame construction in general use at the present time but with novel changes in this laminatedconstruction itself which greatly improve it for any of the present-day oval type rackets and still more particularly for my own novel head shape.
In studying the reaction in play of experimental rackets of this novel shape made up with ordinary laminated wood frames, I have made careful examination of the lacquer finish ou a frame to discover a definite pattern of checking in the lacquer after play which discloses important facts as regards the stressing affecting the frame and the resistance which should` be given the frame to best resist and resiliently react to same. This pattern of checking, and so stressing, is diagrammatically indicated in Figs. 3 and 4. Fig. shows what is so regis-- tered on the inside of the frame at the outer extremity and Fig. 4 on the inside of the frame at the inner extremity, in approximate patterns, and in relation to the central axis lines A-A and B-B respectively. One of the particular purposes of my invention is to reinforce the racket frame in relation to this checking pattern and with a counter pattern of high tensile-strength filaments which will cross the disclosed checks, preferably at approximately right angles thereto and so provide direct resistance to these disclosed and so registered stresses which the frame has to meet, as proven by my check record.
A glance at the diagrammatic patterns of Figs. 3 and 4 will disclose the fact that the dominant stresses to be contended with are torsional, as proven by the checks being almost all diagonal 5, with only a few checks 6 on the sofiit of the inturned arch 2 being at right angles to the longitudinal axis of the frame 1a. It will be noted that the intensity of the stressing or the frequency of the check lines increases approaching the central axis of the head at the outer extremity and the inner extremity of same but that directly above the throat portion, approaching B-B from either side, these lines fade out, doubtless due to the added strength of the solid throat. Other than that the torsional checking is registered with a much greater frequency and closeness 0f lines 5 at the base of the head while as the sides of the head are approached from the opposite extremities A--A and B-B, the check lines grow less numerous, are spaced farther apart and practically disappear by the time the middle portion of the head is reached. In addition, longitudinal splits occur in the frame wood at the base of the head, as'indicated by lines 6a, indicating a tendency of the stressed frame to shear at this point, again indieating the necessity of diagonal shear reinforcement which I propose to meet with my diagonally disposed filaments at these points of weakness and heavy stressing. It will be seen that ball impacts on the Stringing 7 tend to twist and turn the racket head inside-out, so to speak, with an inwardly revolving movement. It is to be particularly noted that in the present-day laminated Wood racket frames no provision has been made against this dominating stress, so proven by my checking patterns; that instead of providing diagonal reinforcement to resist this torque and shear, the grain and fibers of wood laminations encircling the head, almost without exception, all extend longitudinally of the frame and in no case are they arranged diagonally. My invention aims to correct this important deficiency in these laminated wood frames. Such provision is still more important with regard to my uniquely shaped head with its inturned arch as it will be found that if this head is not properly constructed to meet the torque and twisting of the frame when tightly strung, it may tend to distort by twisting on its central longitudinal axis in the head, as indicated in exaggerated form in Fig. 5. The frame of Fig. 1 is designed to avoid such distortion. It will also be understood that my inturned arch 2 is likewise designed to prevent the elongation difficulty long presented by pres'ent oval heads. The heavy pressure of the transverse strings as well as that occasioned by the enlargement of the head with moisture absorption cause the outward pointing end of these oval heads to distort or collapse outward with the attendant narrowing and elongating of the head. This is resisted by a few central longitudinal strings which become stretched and overstressed in this badly balanced construction found in all oval type rackets. In contrast my inturned arch 2 brings these elongating pressures to a dead center and tends to spring inward instead. With the highly resilient properties and resistance to set which I build into this arch 2, as will be detailed, it is combined with the very taut Stringing rmly anchored thereto to shoot the ball in T returning same. This, it will be seen, results from the arch bending slightly inwardly with the ball impact onl the strings, then instantly and violently rebounding outward, this occurring coincidently with inward and outward action on the part of the out-turned side arches 4. In this action, the ball must linger slightly longer on the strings as they are drawn across same in stroking, so putting more st or spin on the ball. In an oval head, on the contrary, the out-turned end arch fights against the two out-turned side arches with ball impact on the strings, tending to neutralize same and prevent the bow action of applicants novel frame, just described.
A further fault common to tennis rackets in general, to which thisinvention is further directed, is a weakness or deadness with ball returns from the outer portions of the head. As contrasted to a sound and strong return of the ball from the central and lower portions of the head, a weaker or dead return will often be felt on returns from points further out. To provide against this deadness in the outer portion of the racket and also further provide means for resisting torque and the twisting movements suggested in Fig. 5, including cross-bonding the longitudinally disposed laminations of the frame, I novelly provide members 9 of Fig. 1, which are adhesively bonded on the opposite faces of the frame. The
position of these members 9 may be varied to some de-l gree, upward or downward of the frame as may be found most effective for any frame, but these members are so located as to strengthen the outer portions of the head frame by trussing same out to a greater thickness,
' the members 9 being tapered to a thick belly in the central portion as noted. They may be formed of any suitable material or combination of materials, wood, plastic, filaments, etc. In the present instance, however, I make these of wood, cut and shaped so that, as diagrammatically indicated in Fig. 6, the grain and wood fibers extend uncut along the full outer length thereof or at least approximate such a purpose so far as the shaping makes feasible. This can be roughly accomplished by cutting the wood while in bent position or bending same to a at gluing back after cutting the back to a curved or angular line, etc. The members can be bent, as with steaming, to the curving outlines of the head, and should be, to keep the grain extending longitudinally and continuously for tensile strength. These members 9, it
will also be understood, can be advantageously applied to any oval or other wood frame as well as to my novel frame of Fig. l and the like.
When desired, as in the case of Fig. 1, I also reinforce the inturned arch 2 and the adjacent outturned arches 8 with similarly imposed overlay laminations 11 bonded on the opposite faces of the frame, as will be more clearly illustrated in Fig. 14. With moldable mate` rials, such as plastic and the like, these reinforcements 9 and 11 can be pre-formed to the exact shape of the racket frame. In some cases the members 9 and 11 may be formed and applied as and in one continuous piece, extending from one side ycontinuously about the end of the frame to the other side. In molded material, this is a simple matter. With wood or stamped material, however, combinations of forming or waste of material may make this less desirable.
In addition to the above, the frame of Fig. l, and as a notable feature of this invention, departs radically from standard laminated wood racket construction as practiced. It will be understood that in the latter case the frame is formed of a multiple ply of wood laminations bonded together edgewise to the plane of the Stringing except for some reinforcement generally added at the base of the head. The wood laminations have their grain extending lengthwise of the frame, except in rare cases, and are cut and finished to form the complete thickness of the head frame (measured at right angles to the plane of the Stringing) except so far as the portion adjacent the throat is concerned. By contrast, in my construction I cut the bonded wood laminations forming the frame to a thickness much less than 'itiA the aforesaid as well as much less than the final thickness of the frame about the head. I then build the head frame thickness up by bonding face laminations extending around the head as a Whole or for the most part, disposed crosswise of the edgewise laminations, and so at an angle thereto, and on the opposite faces of the edgewise formed frame. This novel racket frame construction, with the wood and other laminations in the two distinctly different planes, provides great advantage in strength after the manner of a box girder so to speak, and particularly for resisting the bending stresses applied at right angles to the plane of the Stringing and at the same time the tremendous pull of the high tensioned Stringing in the plane of the Stringing while at the same time strongly bonding the wood laminations together across their longitudinally disposed joints to resist delaminations, longitudinal shear, and the notable torsion already discussed. Also, because of these edgewise and thus core laminations being cut much thinner for the frame, as noted, it will be seen that where laminated frames are made in multiple by the well known lblock method where the veneer laminations are made up in a formed block and the block then sawed into a multiple of individual frames, a correspondingly greater number of frames will be obtained from each such block because of this reduced thickness of the frame with regard to these edgewise laminations. Similarly, with the other method of making up frames individually, correspondingly narrower strips of wood or veneer are made possible for the work.
In forming the frame of Fig. 1 with this novel construction I also employ novel laminations for these crosswise or face laminations encircling the head, while these laminations can also be made of Wood which is bent by steaming methods to the shape of the head and then sliced up to the proper veneer thicknesses, or of various other materials and such as are moldable to the shape, as plastics, etc., I provide still more unique laminations, particularly designed to meet, among other things, the shear, torsion and twist disclosed in connection with Figs. 3, 4 and 5. For this purpose I employ a braided tube 13, formed with high tensile-strength filaments of glass which are coated with adhesive, the tube being filled with other glass filaments 14, preferably continuous throughout the length of the tube, and similarly coated with adhesive. These filled tubesform the lamination 12, Fig. 7. The laminations 12 are applied to the opposed faces of the edgewise wood laminations ofthe frame, which have been previously glued up, and while the adhesive coating on the glass filaments is in an uncured state, and are then mol-ded to same under pressure as shown in Fig. l2 and elsewhere. It should be particularly noted that the filled tube laminations in the unhardened state are thoroughly pliable and because of the diagonal disposition of the tube filaments are readily and freely adapted to the shape of the frame at any and all points and can be given varied widths and thicknesses at different points of the frame as de` sired, the loose filaments 14 filling the tube being also free to adjust themselves readily to such changing form at any point. It will be seen that because of the diagonal orientation of the tube filaments I also providel high tensile-strength diagonal reinforcements about the frame to counter and resist the torsional and shearing strains already so fully explained. At the same time the continuous longitudinal filaments 14 providethe strong reinforcement and resilience, longitudinally of the frame, for resisting the various bending stresses to which the frame is subjected.
When the reinforcing members 9 and/ or 11 are included, as in Fig. l, the face laminations 12 are molded directly over and to same. Where such is the case, the high tensile-strength filaments 14 are so strutted out from the frame ycore edgewise laminations at such points, therebyl providingexceptionally increased strength to resistthe bending stresses, eliminate deadness and greatly enhance the resilience of the frame and the inturned arch 2. When the members 9 and/or 11 are not included, the laminations 12 are molded vdirectly to the edgewise core laminations at such points and the others where intermediate insertions are not included. The lamination 12 has its opposite ends either abutted 13 at the throat on the central axis B-B or overlapped so that the ends extend any desired distance on the opposite sides thereof to further reinforce the frame at this point as may be preferred. Alternately the joint may be made on the arch 2 if the ends are there overlapped in symmetrical relation to the axis A-A so as to reinforce the frame end on the arch 2.
Figs. 8 and 9 show alternate uses of the tubular laminations 12 by first combining same with a facing or facings to which they are adhesively bonded to provide a preformed unit, the straight unit being 1S and the curving one, Vfollowing the outline of the racket head, being 16. The facing laminations, 17 and 18, and 19 and 2t), may be of any suitable material but in this instance I employ vulcanized bre or fish paper which is strongly bonded with preferably a thermosetting adhesive such as Bakelite or phenol-formaldehyde in a press under heat and pressure as required. This sheet fibre can be of any desired thickness and color. lts outer surface, after the strips are finally bonded, provides excellent bonding surfaces for further gluing, whereas the hard glassy surface of the nally formed and hardened unit 12, if used by itself, presents a more dificult and uncertain gluing surface when bonding same later with other laminations or portions of a racket assemblage. This is important Where rackets are made in shops not employing hot press or their equivalent means for bonding and` where it facilitates assemblage and production to employ the glass filament reinforcement in a form already made up, as with 15 and 16, secure much higher pressures in bonding same, and be sure of a safe bond throughout between the glass elements and the wood laminations.
When such substitution is made for the face laminations 12 of Fig. l, using the lamination 16 of Fig. 9, the strips of fibre or face material 2t) and 19 are stamped or cut o'ut to follow the contour of the racket head as indicated. To avoid Waste, in stamping out the fibre for this purpose, spaced apart joints as 19a and 2da can be made, these being staggered in relation to each other in bonding, the unit 12, however, forming a continuous member in the sandwich so formed. After final bonding in a press in which the elements 2t), 12 and 19 are assembled in superimposed relation, the complete preformed element 16 is glued or adhesively bonded-in duplicateone on each of the opposed faces of the edgewise laminated framecore of the racket head and in lieu of the laminations 12 in Fig. 1, this being accomplished in a suitably shaped head form and subsequent to the edgewise core having first been glued up and surfaced for properly bonding to these laminations 16 (after the manner of Fig. 44).
Fig. shows an alternate form of laminated unit 21 which can be used when desired in place of or 12 of Figs. 8 and 7, respectively. In this case sheets of vulcanized fibre or other suitable material are adhesively bonded together with glass fibre or other high tensilestrength filaments interposed, as shown. In this way both longitudinal and diagonally disposed tensile reinforcement is procured without the braided tube 13 of Figs. 7 and 8. It should be understood that it has not been found feasible to Weave glass filaments in a diagonal or braided weave except in tube form. In lieu thereof, I dispose rectangularly woven glass cloth diagonally, as 23, in the sheet assemblage and longitudinally orientated filaments in-unwoven or woven form, as 25, between the fibre sheets 21a, 2lb and 21C. The glass filaments throughout are coated with preferably thermosetting adhesive, which is likewise the case withregard tosFigs. 7, 8 and9, and the laminated sheet' assemblage finally cured and well bonded under pressure, to which high pressure hydraulic presses arev well adapted, the same as in making the vulcanized sheet fibre itself. Thereafter this laminated stock can be stamped out tov form the strips of Fig. 10 with excellent exterior bonding surfaces for gluing same in an assemblage with the wood laminations of the racket frame.
The edgewise laminated core construction of the frame of Fig. l is disclosed in Fig. l2 and subsequent Figs. 16, 17 and 18. While other materials may be used in lieu thereof, l make the core laminations, in this instance, as shown in Fig. l2 (21d, 22, 23, 24, 25 and 26) of selected woods or a combination of different woods. Any desired number of laminations may, of course be ernployed. The tensile reinforcement 12 is interposed in the assemblage between the wood laminations 21d-22 and 25-26, respectively, as indicated. While other highstrength fibers may be used in my tensile filaments in Figs. 7-10, etc., the glass filaments are much preferred because of their very remarkable properties and high strength-weight ratio aswell as their immunity to moisture absorption and their dimensional stability. As the glass is itself an abrasive material, I overlay the glass laminations 12 with protective wood layers 21d and 26 where the Stringing 7 may have a direct bearing under high tension on the edges of the Stringing holes 7a, at the same time placing the glass reinforcement 12 as close as possible to the outer surfaces of the framing to provide a maximum of stress resistance in the frame cross section. These outer laminations 21d and 26 are of strong selected hard wood, such as second growth white ash or hickory. rfhe inner'laminations 22--25, however, being as they are, housed in on the four sides of the frame section by the strong glass laminations 12, are preferably of wood of lower density so as to so offset the higher specific gravity of the glass elements. It should be understood that the inner face lamination 15 is the inlay reinforcement occurring only at the throat and extending up the sides of the head framing for a desired distance, as indicated in Fig. l, and above that point the lamination 26 is the outside and string bearing face for the inside of the frame. 15 is in itself a multiple ply of 17, 12 and 13 as shown in Fig. 8 and with its diagonal glass filaments of 12 pro-- vides this additional strong resistance to the torsion stresses and shearing at the throat end of the head disclosed in Fig. 4 as indicated by 5' and 6a. The other two edgewise laminations 12 further provide against this torque at this point and throughout the frame, extending as they do, continuously about the head and down the handle, except in modified forms where, when dictated by weight, or cost considerations, etc., portions of same may be omitted. I make such arrangements by retaining the elements 12 at the outer end of the head only, along with 15 at the inner end of the head, thereby providing torsional resistance at the heavily stressed areas of Figs. 3 and 4;- or I may extend the inner lamination 12, next to 26, merely around the head portion and not down the shaft While omitting the outer lamination 12, next to 21a', or retaining same only at the outer end of the frame to reinforce the arches 8-2-8 and adjacent thereto. Other similar modifications may be made to provide different models, weights, balances etc., as may be preferred.
After the edgewise laminations of the frame are assembled, formed and adhesively bonded together along with the throat wedge 27, whether by forming frames individually or sawing or slicing same from a glued block assemblage, the edge faces are sanded, if necessary and prepared for bonding with the face laminations 12 which are adhesively molded to the opposite faces of same. The edges of the outer laminations, as 21 and 15, or 26 as the case may be at certain points of the frame, are first, however beveled 28, or rabbetted, so that in the molded bonding and final shaping of the face laminations 12, the latter will have their edges extended and formedvabout the edges ofthe edgewise laminated core unit. The latter will so be firmly gripped and bonded against later delamination, not only by the stresses of stringing and play but likewise and particularly from moisture absorption and expansion, it being noted that the glass filaments so gripping the wood laminations and across their ply joints are unaffected by this moisture.
In order to protect the Stringing exposed on the outer rim of the racket head against abrasion and injury from ground strokes, etc., as is found necessary in tennis rackets, I further novelly mold these cross or face laminations 12 so that around the outer half of the head, or for a desired distance, the edges of 12 are protruded outward on the outer edge of the frame, as 12a of Fig. l2c so as to thereby form a recessed groove in which the Stringing 7 lies and is properly protected. This arrangement is important for an oval frame but is still more important for the frame of Fig. 1 with its inturned arch 2 in preventing unbalanced distortion in the tightly strung racket head. In the ordinary wood frames, which are of oval type, the aforesaid string protection is provided by cutting in sinkage slots where the Stringing lies on the face of the outer rim. In Stringing a racket these slots have to be different on the opposite sides of the head with respect to the central axis and as they are cut diagonally across the grain, as is well known, they weaken the frame and to different degrees on these opposite sides, thus causing the frame in its unbalanced and non-symmetrical condition to tend to warp outward on the weakened side or corner of the frame, as the frame ages. In the frame of Fig. 1, the warping action is different, as suggested by Fig. 5, and so it is of prime importance to eliminate this present un-balance found in orthodox frames, the more particularly in the frame of this invention. This is facilely accomplished by the molding of the laminations 12 which is further disclosed in Figs. 14-18. Attention should also be called to the fact that in those portions of the head where the element 15 is employed, as in Fig. 12, its outer face member 17 protects the Stringing from direct abrasive bearing on the inner glass iilament member 12 of same where the Stringing holes occur.
In Fig. 11 is indicated diagrammatically the manner in which the cross sectional area of the frame is reduced by my construction so as to greatly reduce air resistance in hitting with the racket. This is made possible by the use of the laminations 12 which are many times the strength of wood laminations as used in orthodox Wood rackets, the glass filaments, 13 and 14 of 12 (as indicated in Fig. 7), having strengths ranging between 100,000 and 200,000 p. s. i., as compared with medium steel at 50,000 p. s. i. and wood with but a fraction of such tensile strength. Thus, if the normal cross sectional dimensions of the orthodox wood frame are represented by 29 and 30, the edgewise thickness of the laminations, as 29, is reduced to the thickness 31. To this core is then added the two relatively thin face laminations 12, thus giving a total iinished thickness of only 32 which is substantially less than the orthodox 29. Similarly, with the inclusion of the laminations 12 in the edgewise assemblage, the normal face Width of the orthodox frame indicated as 30, is reduced to 33 by reason of the much greater strength of the edgewise disposed fiberglas laminations 12. It will be understood that while the designation fiberglas employed in the specification refers to the trade-marked material known as Fiberglas, conventional fiber glass, or glass iiber material forming glass threads or the like, now widely manufactured, may be used. Fig. 11 is intended to diagrammatically disclose the above in principle, only, and not necessarily in exact dimensions.
The inner lamination 26, which is a very important one in developing my novel and maximum resilience in the frame and my induced reactions to ball impacts, serves in the compression capacity of cantilevers terminating on either side of and adjacent the sollit of the arch 2 which in its functioning performs high tensile duties. Lamination 26 may be glued up with the other edgewise laminations 12-21 and designed to extend with same down the full length of the racket frame to the handle termination. However, in this instance, and particularly to still further enhance the resilient reaction, I merely extend 26 as a hoop-like inner rim around the inside of the head, instead of down the handle shaft. This also has the advantage of permitting the use of shorter and often more eX- pensive material and particularly material or choice woods which are only available in shorter lengths or can be had economically only from short Waste or scrap. Yew and Osage Orange wood are such materials of highly resilient properties but very expensive in longer lengths of good quality. Further advantage of this can be taken by jointing the rim 26 on axis B-B at the throat, otherwise it can be extended around the head in one piece. High compression plastic is also a particularly desirable material for 26. 26 can be, and in this case of Fig. l, is further reinforced by the inlay lamination 15, of Fig. 8, glued to the outer face of same, as shown, in the lower portion of the head. In this instance, 26 and 15 may be glued into the head frame after the edgewise laminations and the throat wedge 27 have first been glued together, all at one and the same time, and before the crossWise laminations 12 are bonded on this edgewise core. Also all the edgewise laminations, including 26, along with the two opposed face laminations 12 may be glued together in a single simultaneous gluing operation. A very important feature of the gluing in of 26, together with 15, is that the head frame is rst distorted outward at-the sides as C-C and the end as D by applied force, as indicated by the direction arrows at those points, and to the proper predetermined degree. 26 may be pre-shaped as with steaming in the case of Wood, but in any case its upper ends preferably extend outward so as to require pressing or snapping inward per arrow E in placing same Within the distorted frame for the gluing of same and likewise 15. After the glue is thoroughly set, the distorting pressure on the frame at C-C and D is removed and the frame allowed to retract toward its normal position. In this way the wood laminations of the frame core assume normal position or approach to same with little fiber stress While 26 and 15 coincidentally become pre-stressed and compressed so as to be highly sensitive, resistant and reactive to distortion of the frame inward at C--Cl and D as results when the ball impacts on the Stringing in play. This is particularly important in connection with the cantilever ends of 26 which are designed to resiliently resist the depression of arch 2 with the ball impact, and with the aforesaid pre-setting, and kick upward violently in reaction to this bending and compressing impact, and in supplementing unison with the tension reaction of the arch 2. A resilient plastic of high compression strength is accordingly a preferred material for 26 and the samey for the laminations 17 and 18 of the unit 15. The lamination 12 to which 26 is glued should preferably be provided with a thin fibre facing, 12 in Fig. 12, when the edgewise core is first glued up so as to provide a good gluing surface for bonding 26 to. When 26 is alternately extended down the handle shaft instead, however, and is so glued up simultaneously with the other edgewise core laminations, this fibre facing 12 can be omitted. It should also be noted that the cross facing laminations 12 which are glued on the edgewise formed core frame as already noted, are also preferably so glued in place when the frame is slightly expanded outward at D with 26 so bonded in place until the bonding of the faces 12 is fully set and the frame then released. In this way these liberglas faces remain likewise preset to give greater resistance and spring action to the 8-2-8 arch structure and with less iiber strain on the weaker wood laminations of the frame core with the inward bending of the arch 2. Also it should be noted that in lighter or simpler frames, the lamination 26 may be formed with the structure of 15 (Fig. 8) and 15 omitted if desired from the frame of Fig. 1 where it forms the lower inlay reinforcement'of'the' head frame, 26, alone, so serving in a dual capacity. The outer cantilever ends of 26 which have been glued in whilethe frame end has been temporarily distorted outward at D, and so compressed inward with the removal of this distorting force, are subsequently forced still further inward by forcing the arch 2 slightly inward at D in conjunction with my preferred method of stn'nging the frame as brought out in my pending application Ser. No. 545,630 already referred to. In this way both the arch 2 and the cantilevers 26 are pre-set and loaded to give the ball return a maximum kick Other features which will be later brought out still further enhance this.
Continuing with regard to the construction of the throat and lower portion of the frame of Fig. 1, the V- like -throat portion between the frame members on opposite sides may be formed with a solid wedge filling same in the customary manner. In this instance, however, I prefer to lighten the head at this point, lower the balance and produce greater Whip and resiliency by gluing in the uniquely shaped wedge 27 as shown in Figs. 1, 12a and 12b. This novel wedge provides a strong and readily glued bearing between the opposed frame members, yet still leaves a hollow V portion 34 inside the throat in its lower portion. This chamber 34 is covered over by the face plate-like members 35 which extend up over 27 to which they are glued along with the frame members and taper off on both sides under the face laminations 12. The face laminations 12, in turn, have their abutting or overlapping ends at the throat outwardly covered by a cover and reinforcing lamination 36 formed of vulcanized iibre or other suitable material, when desired, which further reinforces the base of the head against the torsional twisting inward of the frame to which rackets are prone. Where greater shaft strength is desired, the thin reinforcing face plates 35 can extend down same to terminate at the end of the handle but in this instance l terminate same with the V-shaped end 35 below the throat as shown, thereby economizing in this more expensive material, reducing weight and providing a further bending and stress relieving area below same and between it and the tapering handle forming overlay 1c above the handle 1d. The intermediate and so exposed frame Shanks 1b have the strut wedge 38 between them and this can be made of mahogany or other suitably ornamental wood. An ornamental and structural holding band 37, of suitable material, is preferably added at the base of the throat. The plates 35 are constructed to put extra resilience and strength into the throat area and are preformed preferably of 3 ply as shown in Fig. 13. The outer face is av thin layer 35a of strong resilient plastic of high compression strength; the inner core 35b is fiberglass in one or more ply and preferably with filaments extending vertically and horizontally either in woven cloth or unwoven formation, all of course coated with the customary adhesive; the inside lamination 35C, of the ply, is also plastic like 35a but thinner, preferably, to minimize Weight and provides a good outer gluing surface for bonding to the frame to which it is adhesively bonded. Other materials may be alternately used for either or both 35a and 35C, as for example vulcanized paper or sh paper, and for 35h high tensile-strength nylon or fortisan laments for the glass bers. When desired, the outer member 35a may be omitted and the tiberglas, which in its hardened adhesive matrix is quite ornamental, made the exposed outer face. lt will be understood that the preformed plates 35 are normally cut from mass production sheets formed under heat and high pressure with hydraulic presses giving same great strength not so attainable in shop gluing, yet providing good gluing surfaces for incorporation in the racket frame which a liberglas matrix itself, when preformed, does not so readily or securely provide.
In. view of the greater strength presented by the strongly shaped base formed by my acorn-shaped head,
as compared with the orthodox oval type rackets, and particularly when formed as herein with my liberglas construction, I furthermore, when greater whip is desired, graduate the thickness of frame about the throat by sanding it down prior to gluing on the plates 35', reducing same to a minimum thickness at the point 39, as indicated in somewhat exaggerated form in Fig. 2, from the upper points adjacent the ends of 36 and from the lower point adjacent the band 37 (Fig. 1). Alternately and in lieu of this, the plates 35 themselves may be provided with graduated thickness to accomplish a similar end and the frame Shanks of 1a, in such case, left without graduated thickness at this point. l also preferably provide a holding tie 39 of glass fiber cord or filaments with adhesive coating, molded to and about the throat at the thinnest point or area 39, as shown, under the heat and pressure required for polymerizing. This provides a still greater holding strength at this hinge point for the plates 35 against the bending moments developed in hitting the ball and so still further augments the resilient reaction of the plates thereto.
Figures 14 to 19 show in larger scale the construction of the outer extremity of the racket head of the Figs. 1 and 2, and particularly with regard to the vitally important arches 8 2-8. It will be noted, Fig. 14, that the outturned arches 8 formed in conjunction with the inturned arch 2 are widened in face depth and so strengthened by insert members 46 glued in the laminated frame construction and formed of strong compression material either wood or suitable plastic composition. On the soflit of these arches 8 and abutting the sot of arch 2, the cantilever and compression lamination 26 ends to permit the high tensile-strength glass lilaments of the tensile lamination 12 to take over and provide the vital spring soint of the inturned arch 2 and resist with their unique physical properties and superstrength, the tremendous breaking stresses centered on this point. While other strong iibers such as nylon, Fortisan, etc., may be employed, none of these provide all the essentials or an equal strength. Of vital importance is the fact that the glass filaments will not take a set, or stretch, creep, or fatigue, substantially, nor absorb moisture and change size and length thereby. All of these requirements are needed for the proper and permanent functioning of the spring arch 2 in its tensioning reaction and resistance to the very great string pressures brought to bear on it, and it must not take a 5st, as does Wood by itself. To better meet its duties, the berglas soit lamination 12 of arch 2 is preferably reinforced with additional glass filaments extending through the arches 8-2-8. These are shown in Fig. 19 as unidirectional longitudinally disposed layers 41 and 42, stitched 43, or otherwise secured, on to the iberglas braided tube 13. Unidirectional or equivalent woven berglas tape or cloth can also be used for 41 and 42 as dictated by convenience. As shown in Fig. 12, etc., the frame face laminations 12, in being molded on the edgewise core laminations of the frame, have their readily adjustable and changeable shape broadened or narrowed at the different points, and with corresponding and resultant changes in thickness. Full advantage is taken of this to provide the frame with changing structure at different points to meet its changing stresses, functions and duties at the different points. Thus on the arches 8 which are severely stressed in conjunction with the bending action of the inturned arch 2, or by any enlargement of the frame from moisture absorption, the widening of the face laminations 12 greatly strengthens same and coincidently the so extended and projected edges 12a form a protective channel for the Stringing 7 (Figs. 16-18) for preventing abrasion of same from ground strokes etc., at the outer portions of the head. Midway down the frame this protection being no longer required, 12 is then kept ush with the vresistance to the heavy Aby the so broadened cantilever arches 8.
vasr'spec frame on the outer side and instead extended inwardly to cover the extra thickness of the added lamination 15 from thereon down (Figs. 1 and 12). In presentday wood frames, the Stringing lacking the protection here provided by 12, has to be sunk in slots in the wood `whlch not only weaken the frame by cutting diagonally lacross the longitudinal wood fibers but also cause it to distort as the slotting channels have to be different on the opposite sides of the frame and so offer unbalanced pressure of the Stringing which calls for 50 to 70 pounds pressure on each string, As shown in Figs. 14 and 16, the shape of the inturned arch 2, itself, provides protection for the strings at the central portion thereof so 12 in its molding is accordingly gradually brought fiush again with the frame on the outer side and correspondingly thickened so as to so strengthen the arch where the frame becomes narrower at this point as shown in Figs. 14 and 15. The arch 2 is so given more :dexibility by thinning, yet its strength so maintained, and it is staunchly supported at its ends These arches 8-2-8 preferably have their heavily stressed laminations tied together and are further reinforced by bands yor wrappings 44, formed of adhesive coated glass filaments molded on the frame under heat and pressure and preferably after the frame is already glued up. vThese reinforcings 44 are preferably located so as to l'come between the strings as shown in Figs. 14-15 so as not to interfere with same when possible and where spanning the sunken channel formed by the edges 12a rest on cross filler blocks 45 glued in with same and further cross bracing the frame and 12a. As the glass filaments are immune to water absorption, these cross bands 44 hold the wood laminations together and against strong delaminating tendencies at these points both from the play action of this unique frame and the wood swelling in moist weather. As further shown, Fig. 15, the arches 8 2-8 are further strengthened, in addition to the face laminations 12, by the reinforcing cross laminations 11, spanning the edgewise laminations and graduated to increased thickness at the center of arch 2 to strengthen same. This also provides special resistance to the twisting stresses met with in the frame as indicated in Fig. 5.
A particularly important feature of Figs. 1 and 14 is the positioning of the edgewise lamination 12 so that it forms the soffit of the heavily tensioned arch 2 on its tension side, then turns upward on either side to effect a more Vertical and so more effective tensile resistance by the glass filaments and then continues on to reinforce the cantilevers 26 and fillers 40 on the upper or tension side thereof. Correspondingly the other and upper lamination 12 cornes in the upper portions of the arches 8 to so reinforce same on their tension side and is anchored down by the centrally placed bands 44 in the sinkage of arch 2 so as to develop a maximum resistance to the tension stresses in the top of the heavily stressed arches 8. The lower lamination 12, in its turning upward from the sofiit of 2 also provides resistance to shear stresses developing in such a span. I further enhance the resilience and strength of arch 2 and avoid over-stressing the wood fibers therein by throwing the tension load in the arches 8-2-8, and 2 in particular, largely on the strong tensile laminations 12 or their equivalents. Toward this end, I preferably pre-shape, as with the customary steaming process, the edgewise wood laminations, as 21d (Fig. 12), to the shape of the racket head, or the arches 8-2-8, or in any case the inturned arch 2, prior to gluing same together. I further, preferably, then, in conjunction with assembling these laminations in the press-form, properly prepared for gluing together and with the other laminations as the tensile edgewise laminations 12 and also 26 when desired, force the sofiit of the material at arch 2 slightly ,outward of the head D (Fig. 1) or as indicated in some- "14 what diagrammatic and exaggerated form as 52' in Fig. 20, and in this temporarily outwardly tensed position glue the assemblage permanently together before removing same from the form. Thereupon, the preshaped laminations tend to return to their former deflection in arch 2. Thereafter, as already noted, I preferably force arch 2 slightly further inward of the head in conjunction with the Stringing of the racket and firmly anchoring Stringing under high tension thereto. This all results in bringing the strong tension members, as 12, into resilient action while not over-stressing the weaker wood fibers. It has been found that the glass filaments in a laminated structure can develop a tensile strength of 120,000 p. s. i. with a stretch of only 3%. It is the quick recovery of arch 2, as with this stretched tensile reinforcement which drives the ball the harder and faster. In this connection it may be noted that the diagonally disposed filaments of the braided casing 13 (Fig. 7) of 12 form a stress distributing intermediary tending to spread over a larger wood area, and gradually,
the direct pull of the longitudinal filaments 14 in action and thereby reduce fatigue and rupture in the wood bers to which 12 is glued and which are required to work with the non-stretching glass filaments of much greater resistance, etc. The same tensioning and removal of slack in filaments 14 of upper edgewise lamination 12 similarly tensions the arches 8 to their supplementing action with inturned arch 2. Further tensioning is provided for as will be noted in connection with Fig. 43. In cheaper rackets the above pre-steam-shaping can be omitted, and instead the wood laminations can be bent and glued together to the racket shape and forming the arch 2, and, thereafter, the tensile laminations, as 12, glued to said Wood laminations while the so-forrned arch 2 is temporarily distorted outward of the head.
A further means of developing the tensile and quick spring action in the 8--2-8 arches of my frame is shown in Figs. 20 and 21. Fig. 20 is a modified form of the racket of Fig. 1 and has a special reinforcement 46 adhesively and mechanically bonded to the inner side of the arches 8 2-8 to form a strong spring-like kicker to still further accelerate the ball return by this resilient arch structure. The element 46 is preferably formed with a backing 47 of highly resilient plastic with high compressive strength which is molded or adhesively bonded to a tensile lamination 48 of glass filaments and with a facing .49 likewise of resilient high compression plastic, all said members being well integrated by proper bonding. These elements 46 can be formed as individual units with mass molding techniques or can be produced in sheet form from which the units are stamped or cut. The high tensile-strength reinforcement 48 is formed as 12 of Fig. 7 with longitudinally extending filaments or can be unidirectional cloth or equivalent, particularly if 46 is produced in multiple sheet form. The iiberglas wall 48 is importantly shaped and, similarly to the bottom lamination 12 of Fig. 14, it dips from the upper portion of the two side outturned arches (as 8) downward to the bottom of the central inturned arch (as 2). Each of the three arches is so provided as shown with a thicker plastic wall on its compression side. 46 is formed in its initial shape, whether by molding or/and machining or otherwise, to the dotted outline 5t) with the tail ends 51 extending widely outward and the central arch less depressed downward than in its final shape, as shown. After the racket frame 1 is formed with the arch structure 8-2-8, the inturned arch 2 is pressed slightly outward as indicated by the dotted lines 52 of Fig. 20 so as to conform to the more flattened top form 52 of 46 except with regard to the extending ends of tails 51. 46 is then firmly glued under pressure to the soiiit of the arches 8 2-8 in conjunction with which the wider extending tails 51 are forced inward so as to come within and press hard in compressed position against the sides of the frame 1. These tails are preferably formed with small sharp studs or spike points 51a which press into the frame and bond mechanically therewith in addition to the gluing. If the frame contracts, as with ball impact on the strings, the tails under compression so anchor and hold 46 in place all the more securely, so insuring it from being loosened. After the gluing has sul'liciently set, the temporarily applied outward pressure is removed from the arch 2 and the frame and 46 allowed to press back toward normal position again and so that 4S of 46 is forced into tension and the slack removed while the wood iibers of 2 remain substantially unstressed or as originally formed or approaching same, 46 accordingly assuming something of its final form of Fig. 21. When the racket is subsequently strung under strong pressure, the arch 2 is preferably forced, in conjunction therewith, to a slightly deeper inward curve and so tensioned or cocked to receive and return the ball impacting on the strings. By reason of the aforesaid procedure the weaker or wood laminations of the arch in such inal position have their liber stress kept within safe limitations while the much stronger glass libers forming the tension member in the bottom of the arch (they may be covered with a thin iilm of the plastic bottom 49 if desired) are given a much higher but still safe stress for them to provide the quick recovery and spring action required of the arch which is further accelerated by the action of the compressed tails 51 forced further inward of the head by the sides of the frame which contract momentarily inward with the ball pull on the cross Stringing. In this action, it will be seen that the spring reinforcement 48 of the two next arches (as 3) is forced inward from both ends so contracting these arches each to a smaller radius, as in winding and so tensioning a clock spring. This produces a violent expanding reaction along with that of the inner arch portion (as 2) following the ball impact on the Stringing.
When desired and to reinforce still further the arches 8 on their tension side, i. e. the top or outer side, I also bond the tensile reinforcement 53 on the outside of the end of the frame as shown in Fig. 20. This is also done while the frame 1 is pressed outward at the end to receive 46 as described. 53 is formed of the structure of Fig. 8 although any desirable tensile reinforcement may be likewise employed. 53 is so also stretched to become pre-tensioned with 46 after the gluing and the release of the frame end from its temporary outward distortion. As 53, so bonded to the frame, serves in a tensile capacity on the top of the two outturned arches 8 and in turn in a compression capacity on the top of the inturned arch 2, I preferably, in employing the strip of Fig. 8 for this purpose, see that 17 and 18 thereof, and particularly the outer layer 17, have good compression values. Preferably a suitable molded plastic or secondly a suitable vulcanized iibre can be so selected for the purpose, it being understood that 18 is such as to provide a good gluing surface on its exterior for securely bonding same to the racket frame. The outer strip 17 can be slotted for string protection where necessary and in such manner, as described elsewhere, for avoiding the old-time frame distortion, and should be sufliciently hard to resist the wear and tear of ground abrasion to which the end of a racket is subjected.
Referring further to Fig. 2U, in this modified form of the frame of Fig. l the two face and crosswise laminations 54, corresponding to 12 of Fig. l, do not in this instance completely circle the frame as in Fig. l but instead terminate above the throat thereby lightening this heavier portion of the frame as found in the throat and shoulder area of orthodox frames and giving more whip and flexibility at this point. Meeting 54 at its lower ends 54a (which can be located at higher or lower points on the frame as preferred for ditierent requirements) and covering the remaining shoulder and throat areas and in this instance extending down the shaft and handle, are the face plate-like members 55, corresponding to 3570i Fig. 1
1d and adhesively bonded to the opposite faces of the racket Iframe. 55, as shown in Fig. 22, has a lamination 55a of liberglas or glass filaments in one or more ply, adhesively coated and bonded under heat and pressure, as with hydraulic presses to the backing SSb which as in the similar structure of 35, Fig. 13, is thin resilient homogeneous plastic or vulcanized fibre or lishpaper such as will provide a secure gluing surface for the subsequent bonding of these face plates to the frame 1 of Fig. 20 in its completion. For lightening the frame as Well as providing visual exposure of the highly ornamental liberglas, an outer lamination as 35o of 3S, is here omitted but can of course be included when desired, the same as can a ply similar to that of Fig. l0 in lieu of 55. The glass filaments may be present in either woven or unwoven arrangement. These filaments 55C, of the layer 55a, are however preferably orientated, as shown, parallel and at right angles to the longitudinal axis of the frame (as is also the case in 35 of Fig. 1) so as to present maximum and direct resistance on the one hand to the bending stress of the frame in play, which l iind is further disclosed by lacquer checking on the shoulder faces at substantially right angles to the longitudinal axis of the frame, as would be expected. On the other hand the crosswise extending iilaments directly resist the impact stressing which tends to revolve the frame inward (twist it inside-out) and particularly across the top of the throat so as to strongly reinforce the important wedge construction disclosed herein. rlhe thickness of 55 can be quite thin or gauged up to heavier ply according to frame requirements. While the throat may be of standard solid wedge construction, I here in this lightened frame construction employ my novel wedge 27 similar to 27 of Fig. l, which, when of wood, l preferably make of three ply construction as shown with 27, Fig. 12a, particularly on account of being cutaway and stressed vertically and horizontally. In this case I also for still further lightness and increased whip action cut apertures in the two face plates 55 to conform to the throat aperture 34 as shown. At the same time an unusually strong and safely integrated throat structure is provided by reason of the strong face plates S5 which substantially cross bond and bind and hold' all the several core members of the throat section together While presenting a lightened and highly resilient structure not heretofore offered in rackets. The inherent strength of the shoulder-throat curve brought about by my acorn. head shape in resisting inward collapse as compared with the weaker orthodox oval head makes it possible to omit the extension of my face laminations SLi at the base of the head where oval frames have in contrast to be heavily reinforced. This simpliiies the sanding and finishing work at the throat and avoids cutting into the highly ornamental surface of the pressed liberglas 55a which is prone to happen where superimposed wood overlays have to be so finished as present in the orthodox wood oval frames. Referring further to the face laminations 54 and the matter of their application to the frame core, these as shown in Fig. 2-0 use the structure of Fig. 9 with the top layer 19, however, omitted to lighten the frame. 19 may be included for protection andfurther strength when so desired, or the structure of Fig. 7 or Fig. l0 similarly employed for 54. Also when desired for permitting greater flexibility or less weight in the arch `2, S4 may be terminated on both sides of the arch 2 instead of crossing same in one piece. While optional, these two face laminations 54 are preferably adhesively bonded to the frame core after the arch reinforcement 46 (and similarly 53 when used) has been bonded in place. For greater stiffness in arch 2, in this connection, this gluing on of the two faces (54) is also done while ythe frame l' is temporarily distorted outward to lines 52', as already described. In such case these face members are preastretched when arch 2 is then brought back to its original normal position or still further tensioned inwardinthe Stringing process. On the other hand, when less stiffness is desired in arch 2, the laminations 54 can be bonded on the frame core after same has been returned to normal position from its temporary outward distortion. They can also be made to overlap or cover the edges of 46 and 53, or not, as preferred. The core of the frame 1 can be made as 1a in Fig. 1 or can be greatly varied while still being finally completed with the various features of Fig. 20. Where my frames are built for badminton and do not meet the heavy impacts of tennis, they are lightly built to weights around 5 ounces instead of approximately 12 to.151/2 ounces as in tennis and to particularly emphasize whip which is of prime consideration in badminton rackets. For this purpose the plate covering of the throat and shoulder area instead of being that of Fig. 22 and employing the heavier glass filaments can be made as in Fig. 23 where a core of resilient elastic rubber sheet 55e is adhesively bonded between two thin vulcanized fishpaper facings 55d and 55)c in pre-fabrication in a press, these facings so providing the necessary protection and the gluing surface for bonding to the frame core members, the frame also being made with more whip, when Wanted, with the thinning 39 of Figs. 1-2.
In Fig. 24 is shown an alternate arrangement of cornbining the cross face laminations as 12, and here designated 56, of reinforcing the frame and providing the protection necessary for the strings, and in a different manner. The frame core 5'7 can be of any construction but in this typical frame section is shown as a five ply of edgewise bonded wood laminations, which also because of being encased with highly reinforced outside laminations may be of very light wood of less than the strength normally applied to frame construction. Red cedar, willow, yellow poplar, spruce, etc., are amoung such woods available. Such a core is glued up with outer laminations 58 and 59 which are located and built to carry a large portion of the stress load, and for that purpose have a core lamination of high tensile-strength glass filaments being of the construction of Fig. 8 or my modified equivalents. The `face lamination 59a of 59 is preferably of suitable plastic of strong compression strength and protects the strings piercing the frame from within the head from direct bearing seat on the somewhat abrasive fiberglas of the core 12 while the inner lamination 591; is thinner than 59a and preferably of thin vulcanized fiber to provide a good and reliable gluing surface for bonding the pre-formed 59 to the wood core 57, or the plastic can also be used and in greater thickness if its valuable contributions are so desired. The pre-formed plied strip 58 is of similar construction to 59. The outer lamination 58a, of plastic or vulcanized bre, can here be thinner than 58b, if preferred, as the strings may not receive as much abrasive action on this outward seat, and the inner lamination 58b may be vulcanized fibre or the plastic, the same as 59h. In contrast, however, 58 still further includes another outer face member 58e, primarily included for string protection against ground stroke abrasion and without slotting into 58a or the core of glass filaments 12 to so weaken same or bring the strings to a direct abrasive bearing on the glass surface of 12. 58r.` may be of any suitable material and vulcanized bre may also be used for this. The slots 7b, as indicated in Fig. 24, for the Stringing 7 are preferably stamped in the libre strip before bonding same to the balance of 58 with adhesive in pre-fabricating the latter. In this way, the usual cutting of the slots and holes as normally done in a wood racket, can be greatly sirnplified. The readily stamped 58e so provides a templet on the glued up frame for subsequently` boring the so located holes 7a through the core of the frame. As it has been found preferable ,in racket making to bore these holes and cut the string slots by hand rather than with complicated and expensive machines, it will be appreciated how the pre-stamped strip 58e when embodied in the frame .greatly facilitatesthis operation in addition to serving to provide the string protection required. 58e is also offset in being glued to 58 as a result of being cut to a narrower width so as to form corner rabbets 58d for receiving the face cross laminations 56. Similarly 59 has its edges beveled or rabbeted on the corners 59C to receive same. Thus after the edgewise frame core, including 58 and 59 has been glued up and edge-finished for receiving the crosswise face laminations 56, which are preferably of the form of 12, Figs. 7, 1 and l2, these are bonded to same as already described for Fig. 1 and, at the corners 58d and 59e, molded about the -frame core, as noted, so as to make an attractive stream-lined frame and at the same time bind the edgewise core members together and against delamination so prevalent in laminated wood frames. At the same time the strings remain protected and without bringing about unbalanced distortion as in orthodox wood frames. This is accomplished by the manner of stamping out 58e as diagrammatically indicated in Fig. 25, with regard to the outer extremity of the racket frame where the trouble noted normally exists. In my stamping, the central holes 60 on opposite sides of the frames central axis A-A are followed symmetrically on both sides by the slottings 61, followed in turn by the long channel slots 62 on one side and 63 on the opposite side. These points 62 and 63 are the ones Where standard Stringing, as heretofore,rrequires quite dissimilar slotting in a wood frame in relation to each other. One side is weakened more than the other, thereby, with subsequent distortion of the frame under string pressure made imminent, as previously discussed. By stamping the two long channel slots 62 and 63 down the center of 58e, this normally unbalanced weakening and cross cutting irregularly of the woods longitudinalv fibers in orthodox frames is so done away with while the irregular formation ofthe standard stringing can still be carried out within the channeled recesses 62`and 63. One of these channels must be slightly longer than the other but this is of no great importance. After the channels 62 and 63, follow again the regular slottings as 64 on both sides of the head until the middle portion of the racket is reached and slotting can be dispensed with. It should also be noted that the diagonally placed slottings, as 61 and 64, can instead be placed in straight alignment with my construction of 58 which cross-ties the wood frame from splitting longitudinally. In a wood frame with the wood grain all extending longitudinally, this cannot Vbe safely ventured, even though the diagonal slotting severs the valuable outer wood fibers across the frame. My diagonally woven glass filaments of 12, in themselves, obviate such necessity, providing, as they so do, non-splitting cores in the two outer composite lamina. tions 58 and 59.
Fig. 26 is a modified form of reinforcement for the outer arch 2, similar to 46 of Fig. 2l but of simpler form. This is made individually or cut from sheets made up with the three layers 66, 67 and 68. 66 is preferably a strong resilient layer of plastic bonded on 67 which is composed of the adhesively coated liberglas, as heretofore, and including longitudinal filaments extending lengthwise of 65. Bonded therewith on its lower surface is a thin lamination of fish-paper or vulcanized libre, providing a good outer gluing surface for bonding with the cantilever lamination 26 as indicated, and preferably omitted on the sofiit of arch 2, between the opposed extremities 26 of the lamination or laminations 26. The opposed ends 69 of 65 are tapered away, ,the upper lamination 66 of plastic or other suit,
`able material being either so molded in forming or subsequently machined to such shape. The whole integrated unit 65 is designed to provide a strong spring reacting reinforcement for the arch 2, or rather the arch group 8-2-8 for which purpose it is adhesively bonded to the frame as 1 (or 1a) as in the .case of 46 ofFig. 21. VV Similarly to 50 of the latter, it is formedwith its end sj69 sopextended upward that they haveto be :come
pressed and snapped into place tothe nal shape of Fig. 26`in being adhesively bonded into the frame as in Fig. 20X;v The samevapplies to the arch 2, etc., which is first formed to the lines of 52 of Fig. 2O (the temporarily sprung position of frame 1') then later properly stressed in being brought to permanent position as in Fig. 26 after the manner already described. The further spring action is provided in Fig. 26 with the inner rim lamination 26 (as in Figs. 1, 14) which can be adhesively bonded to'65 by virtue of the gluing surface provided for that purpose by the lamination 68. In such case 26 is likewise sprung into position and tensioned 'as already described, being glued into the frame after 65 is positioned, and preferably simultaneously with the gluingof 65 to the frame. The element 46 of Fig. 21 can be similarly combined with 26 in the frame when so wanted.
In Figs. 27-28 is shown another alternate spring device for actuating the arch structure 8-2-8 with great resiliency and reinforcing same. The skeletonized elcment 70 is formed for this purpose to the upward dotted shape 70' and with the arch 2 conforming to the outward temporarily sprung line of the frame 1', shown dotted 52. As in the previous similar elements the ends or tails 71 are sprung inward in adhesively bonding 70 to the frame 1' (shown in dotted position) and the `end spikes 71a press into and mechanically bond to the frame in addition to the adhesive bonding to same ofl the element 70. After the adhesive has nally set, the arch 2 is drawn inward, as indicated, in conjunction With Weaving the stringing 7 into the Stringing holes in the frame under high tension. In this connection it will beseen that 70 is skeletonized with the apertures, as 72, so keeping its cutting edges `away from the stringing passing through same, as shown in dotted line, and the weight of 70 also so reduced to a minimum while still maintaining a strong resilient structure in which the outer bands 74 and 75 are strutted apart by the cross ties 73. With thin `gauge steel alloy, such as chrome steel, properly heat treated and tempered, a strong resilient spring may be had with little additional weight added to the frame. Other material may also be used, however, for 70, including a plastic or resinv lamina formed with glass filaments extending longitudinally as part of a fabric, or otherwise, it being remembered that the glass filaments will not take a set which is of prime importance in the permanent and resilient working of the arches 8-2-8. If 70 is of metal, special bonding adhesives or cements are available for securely bonding same to the frame. lf 70v is a berglas lamina or' other formed material which may present a questionable gluing surface, then a thin bre inner facing may be bonded on 70 in its original press pre-fabrication which will give the desirable gluing surface for joining to the frame as in the previous descriptions.
In Figs. 29 and 30 are shown some additional or alternate features for the frame extremity of Fig. 14. In Fig. 29, the frame 1a is provided not only with the compression and thickening reinforcements 40 in the lower portion of the arches 8, as in Fig. 14, but in addition includes a similar compression insert 40' in the top of the arch 2, as indicated. Thus 40 and 40' strengthen the three important reacting arches 8 2--8 and also dispose the tensile laminations 12 in position to provide a more elective pull as regards each of these arches. The effectiveness of this tension resistance is further secured and enhanced by the envelopes or binding 76 and 77 securely bonding these laminated arches together at the three strategic points and reinforcing same both against delamination and failure. 76 and 77, the same as 44 of Fig. 14 are casings preferably of glass laments in a resin or plastic matrix cast under suitable heat and pressure on the frame at these points, the glass, of course being immune to moisture absorption which is highly important in the functioning of these casings.
. 20l NylonA is another good ber for the purpose but not as strong. The auxiliary spring, reinforcing elements of Figs. 21, 26 and 27 may also be added to the frames of Figs. 29 and 30. Fig. 30 does not include the inserts 40 and 40' inthe arches 8-2--8, and in addition to the berglas laminations 12 in the frame structure, as in Fig. 14, includes additional similar tensile reinforcement added to 12 inboth the top and bottom portions of the arches 8-2--8,v as indicated, 78 and 79, to enhance their functioning. In addition thereto, when wanted, a continuous tensile wrapping 80, as shown in dotted line, similar to 44 and preferably employing glass filaments, is cast about and encases the frame along the arches Figs. 31-42 indicate, somewhat diagramatically, modied forms of my racket frame structure and their making, employing my glass and other tensile lament structures similar to Figs. 7 and 1, etc., to meet the torsion stresses disclosed by Figs. 3 and 4 and provide further highly novel frames of unique structure and qualities made possible by these lament structures both with and without wood laminations. Great strength and resilience,` dimensional stability and lightness of weight and low air resistance with small frame cross-sections are so made possible with the unrivaled properties of the glass lilaments in particular and the high fatigue resistance offered by same. The laments or bers forming the structures are coated with theproper adhesives in all cases, and porous bers, as distinct from glass, may be also impregnated to more or less degree.
Re. Figs. 31 and 32, in Fig. 32 is shown a cross section of the racket frame in which my laments are arranged in strategic formation to meet the torsional and likewise the bending stresses, the frame being pressure molded with its body formed from the simple flexible and pliable assemblage shown diagrammatically in Fig. 31. For such purpose, my berglas braided tube structure, herein numbered 81, in any desired number of tube ply or thicknesses (in this case two, 81a and SIb) one drawn within the other, has a ber core lling. This core can be variously composed but preferably when a solid frame is wanted is formed with a core 82 of strong but lighter Weight and cheaper ber, as for example sisal, bow hemp, manila hemp or other desirable fibrous material, either in straight loose or braided form, or as a twisted rope. About the core 82 is arranged an outer layer 83 of stronger and longitudinally disposed laments, preferably glass, and the core assemblage so arranged is drawn into the tubular member 81 while in a straight length. To the outer opposed sides of the tube 81 are attached, as by sewing or tacking 86, two twisted cords 84 and 85. These are of light-weight inexpensive bte, as jute, sisal or the like for forming unabrasive seats and bearings as protection against the abrasive glass fibers for the Stringing when the frame is subsequently molded in hardened form. Because of the diagonal arrangement of the tube filaments of 81 and the loose or twisted orientation of the other bers or filaments longitudinally, the tubular element 81 with its llings and cord attachments is highly pliable and adaptable to curved forming with simple finger-placing in the racket form prior to its molding therein and the hardening or polymerization of the adhesive, coating and embedding the various fibers. Thus, in its uncured stage, it is laid in the racket molding form about a central head form (not shown in Fig. 32) on the base platen 87 and thereafter pressedagainst same by the outer circumventing expandible uid pressure tube 90 made of rubber or other suitable material operating between an outer form wall 89 and an inner face shaping member 91 which can be pre-shaped out of thin sheet metal, molded plastic, rubber or'equivalents. Suitable uid pressure (with heat when wanted) is applied in 90, in its initially collapsed position, after 81 and any additional frame parts to be glued to same, such as throat or handle wedges, etc., are properly assembled in the form and the latter closed with the top covering plate or platen 88 which extends over the assemblage throughout. It will be understood that 81 iS extended to form the head, handle shaft and handle base, corresponding to the frame laminations as in Fig. l. In the pressure molding 8l is compressed and reshaped after the manner indicated in Fig. 32 and the cords 84 and 85 pressed into the body of 81 as indicated to provide the string bearings, the holes 7a, for which, are drilled into the formed frame after its removal from the mold, after the adhesive hardening process has been properly completed. The member 34 is so disposed in the groove molded into the frame for the proper protection of the Stringing on the outer edge of the frame as indicated. As a result of the above a Strong resilient light-weight frame can be formed with a notably Strategic location and orientation of the strong glass fibers and with a strong but light-weight core. The frame iS preferably made to the form of Fig. 1 or 20 but can likewise be made to the conventional oval type or other shapes as wanted. Aside from particularly providing against the torsional Stresses as indicated in Figs. 3 and 4, the frame does away with the necessity and difficulty of bending stiff wood laminations met with in common racket construction, as well as the notable deciencies inherent in wood While the unrivaled properties of glass fibers are capitalized to great advantage and by their particular positioning with regard to the frame cross section.
Figs. 33 and 34 show a similar but modified construction and a hollow tubular frame form in place of the solid core of that of Fig. 32. A tube 93 of pliable rubber or the like or a suitable thin film wall, has a rope or Similar core 92 inserted in same to form a mandrel on which, while in the straight, is drawn a tubular member 96 consisting of one or more braided tubes, preferably formed with glass filaments or fiberglas About this is placed a covering wall 95 of longitudinally disposed tensile filaments, again preferably glass although for lighter weight or less expensive frames other Strong fibers, such as already suggested, may be used. This so mandrelmounted assemblage is disposed within an outer covering 94 consisting of one or more braided tubes preferably of glass filaments, either by drawing same into the tubes or braiding Same about such a core. The fibers of 94, 95 and 96, which are to serve in structural capacity are coated with the adhesive at Such point in the operation as is preferred, likewise the string bearing strips 9S and 99 corresponding, respectively, to 84 and 8S of Figs. 31-32. As in the previous case, this bearing can be either flexibly attached to the tube assemblage or properly located in the mold form so as to adhesively bond to the frame tube in the pressure molding of the frame. A strip of suitable pliable material may be used for this bearing in lieu of the fiber cord in all cases, or it may be only flexible rather than highly moldable throughout, as for example a strip of vulcanized fibre. An additional edge member 97 (as distinct from Figs. '3l-32) is also included although this may be omitted when desired. This is preformed and provides an outer shell facing for the outer edge of the racket, at least for the head portion or a desired length thereof. This is made out of high strength, resilient plastic or other suitable material, preferably preformed to the contour of the frame and placed in the form similarly to 91 of Fig. 32. In contrast, however, 97 becomes adhesively integrated to 96 to form a permanent part of the racket frame and toward that end, when necessary, has its inner and bonding surface coated with adhesive prior to being placed in the form whereas 91 is an operative member of the form only and has its face which contacts the frame material protected with anti-adhesive material or other customary protection for Such end. 97 can also be formed of high tensile strength steel allo'yl or other metal or of adhesive coated glass or other strong fibers as a pre-molded unit. After the molding of the frame is completed, the tube 96 has been given, along with its contents, etc., its final shape with a cross section after the manner of Fig. 34. The rope mandrel core 92 is pulled out of the inner tube 93 to provide the hollow chamber 100. To facilitate such removal it is possible, if necessary, to have same in two pieces meeting at the outer center of the head frame and furthermore to coat 92 with a suitable lubricant. be done while 96 is still in straight position. Thereafter, 93 is inflated and subjected to internal fluid pressure (heated when desired). This fluid pressure can be relied upon by itself for the final forming of the tube 96 and its accompanying assemblage in a suitable confining form Without the aid of an exterior fluid pressure tube as of Fig. 3'2, or the two can operate concurrently, both from within and without. In this way a very strong but light frame cross section with its hollow center 100 may be had. The outer edge-facing shell 97 protects the matrix embedded glass fibers of 94 against ground wear and injury aside from providing additional strength, resilience and decorative enhancement. A suitable nonabrasive and Slightly cushioning strip 98, such as chrome, leather or other desirable material is preferably glued in the protective channel formed by the shape of 97 which protects the Stringing where passing between the stringing holes 7a. u
In Figs. 35-36 is Shown another modified arrangement of my fiber filled braided tubes and the frame section so produced. Therein, 101 and 103 are braided tubes of one or more ply, as desired, and preferably again of glass filaments. These tubes are placed on the outer sides of another and central braided tube 102, likewise of oneor more ply or wall thicknesses. The tube 102, however, is braided with strong but non-abrasive fibers, as distinct from glass, such as sisal or the like. The tubes 101 and 103 have a filling consisting of top and bottom glass filament cords 104 and 104 respectively, which are separated by longitudinal tensile filaments 105. In lighter weight frames or of less strength these may be of sisal or other strong vegetable or synthetic filaments of desired lightness but in the strongest and heavier frames glass filaments are preferred for 105, or a mixture of glass and the lighter fibers may be employed. In contrast, however, the non-abrasive central tube 102 is filled with longitudinally disposed non-abrasive fibers 01' material rather than glass fibers. Such suitable fibrous material may include the strong manufactured filaments known as nylon and another Fortisan, or the cheaper vegetable fibers or mixtures of several Such. Positioned as shown in Fig. 35, the tubes as filled are assembled together as .indicated and secured together as with diagonal stitching 107 (which readily adapts itself to the subsequent curving of the tubes) and in this form can be freely flexed and inserted in the racket receiving form as in the similar previously described cases. To provide greater resilience in the finally molded and hardened frame pressed in the form and particularly its resilient arches the high tensile-strength fiberglas cords 104' are preferably pre-stretched or tensioned in the form prior to the molding operation (which can be done after the manner subsequently described with Fig. 43). This is particularly important with regard to the inturned arch 2 (as in Figs. l and 20) where T04 lie in the important and tensile sofht of Same. It should also be noted that these four high tensile-strength cords 104 and 104 are carefully located in my structure at the four corners of the frame Section so as to provide the maximum of strength and in all directions in accordance with well known engineering laws and resist with great advantage the bending Stresses to which the frame is subjected by the blows at right angles to the plane of the Stringing as well as the stress of the high tensioned Stringing against the frame in the plane of the Stringing. It should also be observed that the holes 7a for the racket Stringing are drilled throughout in the central tubular lamination 102 and therefore entirely in non-abrasive material, so combining Its removal may preferably most eeetively the high strength glass iilaments in the frame without abrasive danger and in most simple manner.
Fig. 37 shows another simple modified form of the frame section in this instance produced by employing my tube element 108 of any desired number of ply or walls of the tubular braided glass laments with my interior filling and with exterior string seats molded into same. The filling of 108 herein consists of the spaced apart high tensile strength cords 109 and 109 of glass iilaments strutted apart by a web member, in this case formed by pre-gluing together as in a press a central light-weight cellular core 110 of expanded plastic, such as cellular cellulose acetate known as Strux, or equivalent, with facings 111 of high tensile-strength glass iiber tape, with unidirectional longitudinal filaments preferably in preponderance, and outer facings 112 of thin vulcanized fibre or iishpaper glued to same to provide outer surfaces of good glue bonding character for later bonding with 108, which the preformed glass ber matrix body does not provide in itself or with the same surety. This pre-glued and pressed composite strip with its light-weight core and high-strength outer facing is placed between the cords 109 and 109' so as to strut same apart and the group so drawn into the braided tubular element 108. The nonabrasive string bearing strips 113 and 114 are then attached to or combined with 108 after the manner of Fig. 3l or properly located in the racket mold for such purpose and the adhesive coated elements as heretofore explained are shaped and bonded together in the mold form to provide the racket frame and a typical cross section as shown. The string bearings 113 and 114, instead of being formed of fibrous cords, may be of pre-formed strong plastic or wood, either being preferably here ernployed as pre-shaped strips. The light strong cross section of Fig. 37 is particularly suitable for light-weight badminton rackets but can also be used for the tennis and other racket frames. It should be noted that the Strux cores 110 by themselves could not be bent to the form of the racket without snapping at various points of curvature but by applicants combining these with their facings of glass and/or fibre while glued up in the straight, it is then possible to bend same as wanted without this diiculty.
In Fig. 38 is shown another alternate form of frame section employing two of my tubular elements similar to that of Fig. 37 and in further novel combination. The outer braided glass lilament tubular element 116 is filled with the opposed .tensile fiberglas cords 117 strutted apart by the band or wall 118 of longitudinal glass fila- .i
ments while the similar tubular element for the inner edge of the head framing is iilled with the glass filament cords 117' and wall 118, 117 being preferably prestretched after the manner of 104' of Fig. 35. A strong I beam shape is given the filled tubes 115 and 116 in the f racket pressure molding by embedding in them of the relatively light-weight strips 119 and 120, and 121 and 122, respectively. The inner filler strips 119 and 121 can be of expanded plastic, as Strux, or light balsa wood or stronger heavier wood or other suitable material as desired. The outer and string support strips 120 and 122 can be the same as 113 and 114 of Fig. 37 and made to add structural support and resilience to the frame when so desired. Between the two opposed and filled tubular 'elements 115 and 116, there are one or more laminations, in this case two, 123 and 124, adhesively bonded thereto in the molding of the frame. These can be good structural Wood or other material. The entire assemblage is adhesively united in the press similarly to the others.
Fig. 39 `presents another alternate racket frame section where a strong light-weight and a tubular frame is secured with my braided tube structure after the manner of Figs. 33-34. The braided glass filament tube 125 in any desired number of plyhere shown in two suh,
'12511 and 125bis formedfwith a hollow core 126 by A the means of a temporary pliable mandrel core 92 in Fig. 33 and a rubber or other temporary tube as 93 of Fig. 33, both of which in this case have been withdrawn-the permanent tube structure 125a-125b being molded with expanding uid pressure applied within the temporarily employed core tube similar to l93 after the mandrel core, as 92, has been withdrawn, and adhesively bonded to and between the outer preformed edge laminations 127 and 128. These can be formed of strong resilient plastic or plastic laminas with fibers of high tensile strength Such as nylon, Fortisan or vegetable fibers, or structural wood of desired weight and strength may be used. The strips are preferably hollow backed 129, as shown, or scoriated or provided with other mechanically interlocking or bonding means for engagement with the walls 125 which are adhesively bonded therewith in the molding and hardening of the yadhesive covered fibers or filaments, the strips being first positioned in the slot of the molding forrn with 125 placed between them. ln lieu of a rope or similar mandrel core as 92, and in the case of either Figs. 33 or 39 or the like, other removable core material Such as low melting metal preparations used for such purposes, or contained oil or other fluids may be so employed and later removed. After the frame is molded and removed from the form, the Stringing holes 7a are drilled, passing through 127 and 128, 127 being provided at the proper points with a groove or slots for string protection from ground abrasion. When desired this frame can also be made solid by providing a permanent core in 125 after the manner of 82, Figs. 31-32.
In Fig. 40 another such core filled frame section is shown. The outer tubular braided wall or walls 130 are filled after the manner of 81 of Fig. 31 and the outer string bearing strips and 136 (similar to 84 and 85) attached thereto or properly positioned in the rmolding form. The filling of 130 consists of a core 134 of longitudinally disposed fibers in twisted or braided rope form or merely bunched and combined with uncured adhesive prior to the pressure molding of the frame. On the opposite sides of this core material are placed the additional braided and filled tube elements 132. Each of these two tubes has a glass ber cord 131 at the top and another 131' at the bottom strutted apart by longitudinally disposed filaments 133 of Vglass or alternately lighter bers or a mixture of both. The inside high tensile-strength cords 131 can be stretched or pre-tensioned as elsewhere described when desired. When this assemblage with its adhesive coated fibers is molded, as heretofore, an exceptionally strong frame cross section as shown in Fig. 40 results with the strong corners, similar to Fig. 36.
Fig. 4l shows another modied form of great strength in relation to weight, the racket frame so formed having two hollow tubular cores 144 extending throughout its length along with the four strongly reinforced corners. The outer shell is formed by the braided glass filament tubular element 137 in one or more thicknesses and within this are inserted the filling members as in the previous similar cases. In the two outer corners are the glass fiber cords 140 and correspondingly on the two inner corners are the similar cords 140' extending longitudinally throughout the length of the racket frame, as do the two opposed inner tubular members which are also Ipreferably of braided glass laments although other klighter fibers can be used for same. Between these two opposed tubes (both of which can have a plurality of wall layers when desired), the tube 137 is partitioned by longitudinally extending laminations of any desired number, in this case three, 141, 142 and 143, while on the outside are the Stringing bearing non-abrasive cords or strips 138 and 139 as heretofore described, through which the Stringing holes 7a are drilled after the frame is press molded and the various fibers or filaments and laminations adhesively bonded throughout to form the Z integrated racket frame as previously detailed. The central partition laminations can be of any suitable material or materials but in this instance, in order to provide both lightness and strength, 141 and 143 are of glass filaments in form giving at least a preponderance of longitudinal strength while the core lamination 142 is of expanded plastic, as Strux, and to facilitate the bending of same to the racket head contours in the loose assemblage, this has thin fibre or fishpaper facings 142 pre-glued to its opposed faces as indicated. When wanted, diagonal stitch tacking (as 107 of Fig. 35) is passed through 137 and these partition laminations, also including 138 and 139 as preferred, holding 137 in two tubular divisions. It will be understood that when the inner tubular members 145 are inserted in 137 along with the other member elements, the core chambers 144 are occupied by the core mandrel and covering tube (for interior liuid pressure in the press forming of the frame), the same as 92 and 93 in Fig. 33, or their equivalents already described. The finished frame section of Fig. 41 is shown with these withdrawn, this being done at the desired time in the assemblage, preferably while the filled 137 is in the straight. However, the forming tubes `as 93 can be left permanently in the frame, particularly if formed of thin film, the frame being formed after the manner of Fig. 170 of my co-pending application Serial No. 492,914, above referred to.
Fig. 42 Shows another alternate racket frame section with the containing tubular element 146 of braided glass filaments and in walls of one or more thicknesses provided with a filling including a plurality of transverse laminations. The outer corners are occupied by longitudinally disposed tensile fibers 149, preferably glass, inserted in the filling of the tube as twisted cords or as merely 'hunched filaments which are conformed in the pressure molding later to the molded form as noted. The inner corners are occupied by similar filaments 149. interposed between 149 and 149 are, in order, 150 composed of one or more thicknesses, two shown here, of tape of strong tensile fibers, preferably glass, with emphaSis on longitudinal strength. Woven tape of the unidirectional type can be so used to advantage but regularly Woven tape can be employed. This bears on a lamination 151 of wood, the grain of which preferably extends longitudinally of the tube and frame. Next is a lamination 152 of light-weight or low specific gravity (expanded plastic Strux being a suitable material for same), with its two bearing faces having thin vulcanized fibre or fishpaper 157 pre-glued to Same as heretofore described. This is similarly followed -by the laminations 153 of wood, 154 of Strux, 155 of ywood and 156 of the tensile tape the same las 150. 153 and 155 have their grain preferably longitudinally disposed though in some instances it may be desired to run the grain of the central lamination 153 crosswise of the frame section instead. 154 has the fibre facings 157, the same as 152. In assemblage, the various laminations have their faces coated with the adhesive as required for complete integration in the subsequent press molding, the various filaments or fibers being of course likewise coated as in all previous instances.
This tube filling of laminations and filaments is assembledV in the straight and drawn into the tubular element 146. If necessary to facilitate this end and avoid edges catching in the braided outer tube casing, a tubular wrapping or covering of cellophane or the like can be applied about the filling before drawing same into 146. If cellophane is so employed, this can `be withdrawn after the filling has been placed in 146, but if instead Ia film or sheet with a good adhesive bonding surface is employed, this can be left in with the filling if preferred. The filled tube 146 also has the Stringing support cords or strips 147 and 14S combined with it, as heretofore. The mold form in which 146 is placed and molded into the racket frame, as heretofore, is shaped to give Ia cross section in the head such as indicated in Fig. 42 and with the pressing in of the outer string support 147 and the protective-groove in which it lies preferably forcing a slight curvature into the filling laminations as indicated. This gives a stronger resistance to collapse of the frame with the strong string pressure in the head and a more resilient support of the Stringing woven through the stringing holes 7a which are drilled through the molded and adhesively integratedA frame after its removal from the molding press. As in others of the previous varied frame sections, 146 can also have an outer protective and resilient cover shell, as 97 of Fig. 34, also provided and included in this molding and adhesive integrating of the racket frame.
Fig. 43 indicates the manner of adhesively bonding together the edgewise laminations of the fratrie of Fig. 1 iand the like, in a press. The press, as indicated and corresponding to 87-91 of Fig. 32 (with other portions not shown in the latter), includes a base platen 159 with formed recess 159' for receiving the frame assemblage' and fluid pressure tube 161, all of which are enclosed lby the upper cover platen 158 corresponding to 88 of Fig. 32, which can hinge 158 on 159 and be held tightly on same by its own weight or by any clamping or locking means when necessary. The edgewise laminations of the frame 1a are so held in the recess of the form and in the head portion lbetween a center head form 160 and an outer thin forming strip 162 of thin metal, plastic or otherv siutable material which is properly pre-shaped or molded to the desired form and functions, as does 91 in Fig. v32, onv the face of the pressure tube 161, corresponding to 90 of Fig. 32. The throat wedge 27 and handle wedge 38, with their intended gluing surfaces properly coated with the bonding adhesive, are also properly positioned in the press lform along with the longitudinal frame laminations for the edgewise core, yall of which are of course properly coated with the necessary adhesive for bonding and integrating the frame throughout. After the assemblage is completed and the press closed with 158, suitable fluid pressure is introduced` at the intake 161a of 161 as controlled by the valve 161b, the pressure fluid so entering Va T form and proceeding simultaneously from the outer extremity along both sides of the head framing and out through the tube outlets at the handle end 161C. In this way the on-coming iiuid pressure entering 161a tends to force the loose and curving laminations of the frame 1a forward from the outer extremity to the handle end, so avoiding trapped bulges of the laminations which would tend to occur, however slight the degree, if the fluid pressure instead entered from the handle end or ends. The laminations resting in the recess form 159 are free, as they are being compacted, to be pressed forward at the handle end by the fluid pressure, the recess 159 being provided with continued open space at that-end for permitting or facilitating such forward movement of the laminations. A further feature is provided at the handle end of the press for pre-stretching or tensioning the glass or other tensile filaments 14 of the edgewise laminations 12. These sets offilaments are extended outward at the handle end and the pairs of same from each side of the frame or handle shank are clamped, tied or otherwise suitably held together at their ends 14', as indicated, so as to anchor around upright anchor pins 166 at the end of a yoke or clevis 164 which is held and pivots on an anchor pin 165 which connects with a tension registering gauge 163 which is drawn away from the press platen by the operative screw 167. By this latter means the filaments 14 can be stretched while in their assemblage in the press to the proper pre-determined tension as registered by the gauge 163. This is done in connection with the application of the iiuid pressure, either before, at the same time as, or after the pressure is in the tube, as may be found best, but in any case the filaments are thus tightened before the adhesive surrounding them and coating the various elements of the assemblage is cured and hardened. After the polymerization or hardening has aifspao been properly completed, the fluidgpressure isremoved and lthe racket, so glued throughout, is removed from the press form which has of course been provided with the customary protection against adhering to the racket frame, such as coatings of cellophane or other protective lm for keeping the form free. The next step is that of applying, molding and adhesively lbonding the lface cross laminations 12 to the edgewise formed frame core which is subsequently accomplished after the manner indicated inFig. 44. A very desirable manner of employing the fluid pressure, above, is to have the platen press enclosed in a vacuum case or have the opposed platens join airtight so as to provide a vacuum box in themselves from which the pressure tube intake and outlets extend and means provided for evacuating the air in the press so arranged. In this way, after 4assemblage is complete and the press closed, the interior air is removed from the assemblage and press interior while the atmospheric pressure is allowed to enter at 16111, in accordance with well known procedure. When so depending on atmospheric pressure, suitable contact or low pressure adhesives are of course employed but higher than atmospheric pressures can still be used in 161 while still vacuuming the press which insures a still better bonding and compressing together of the assemblage elements and removal of air pockets. Where heat is required for a particular adhesive, this can be supplied in the regular way land with heated duid in 1 61 and! or heated platens or by high-frequency dielectric heating, etc.
In Fig. 44 is indicated the manner in which the cross face laminations 12 are molded to the edgewise laminated head frame core as of Fig. l, the cross section of `the racket frame being taken at a point beyond the termination of the reinforcement 15 and so composed of the remaining laminations 21, 12, 22-25, 12-12' and 26 as disposed in Fig. 12. The press in which this gluing and molding is done follows the general layout of the head portion of Fig. 43 and includes a bottom platen 168, an inner head form 169, an vouter form 171, a fluid pressure tube 172, operating against the latter on the outer side and against a shaping strip 173 with a projecting groove forming strip 173' on the inner or frame side, 171 to 173 inclusive, of course extending around the outer perimeter of the entire frame or at least the head portion and 173 extending as far as the string protecting groove, formed thereby in the molding of the face laminations 12, if desired. At the bottom of the molding slot formed by the press elements in which the previously glued up edgewise frame core is placed, is another pressure molding tube 174 operating between the base platen 168 and a molding strip 174 for properly shaping the lower face lamination 12 in bonding the latter to the frame core. Similarly, at the top is another pressure molding tube 175 which operates at its bottom against the molding strip 175' for shaping the upper face lamination 12 which is placed in the mold on top of 12 after same has been placed on the frame core which is introduced into the press on top of the lower face lamination 12 after the latter has been placed on top of 174. Both the upper and lower laminations 12 have their filaments coated with adhesive in the uncured stage, or not the finally cured stage at this point of the operation. When the press is so filled it is closed and locked with the top platen 170. The forming fluid pressure is then applied, first through 172 to tighten up the sides of the mold against the assemblage and then the fluid is applied simultaneously in 174 and 175 so as to shape, mold and compress the faces 12 onto the frame core and adhesively bond same together with the polymerization or hardening of the adhesive employed. The lower pressure tube 174 may be dispensed with and the pressure provided for both top and bottom by 175 but more even pressure on both the opposed fades will be assured hy the use of the two tubes which are so preferred. It is also possibleY to employ the same press 28 for performing the operations of both Figs. 43 and 44 by combining the features of the two presses in one when desired and in such case it is also possible to do both operations of gluing the core members and applying the face cross laminations to same simultaneously in one gluing operation, if preferred. When the edgewise core is first glued together in a separate operation,'it ordinarily would have its two faces sanded before gluing on the two face laminations but when using a pliable and readily molded filament body such as 12 which can so accommodate itself to irregularities in edges of the frame core laminations, it is possible to eliminate all or part of such sanding in many instances, by reason thereof. Also, because of the bias disposition of the filaments of the casings (13 of Fig. 7), the latter are readily layed around and adapted to the curving head shape of the frame core when placed in the press slot therewith. After the molding and adhesive bonding operation is completed in the press, the integrated frame, which has been properly protected from adhesion to the press mold, is removed therefrom. With careful and skillfully handled molding there should be required little if any dressing or sanding thereafterin contrast to orthodox frame gluing. The Stringing holes are drilled in the frame which is then given any desired lacquer or other finish if necessary. It should also be understood that while in Fig. l the facings 12 extend around the circumference of the racket head they may also or alternatively extend down the throat sides and handle shanks 1b so far as and when so desired-or they may be omitted from portions of the head frame where desired and as in thecase of Fig. 20.
1t should be further noted and particularly in connection with the pre-stretching or tensioning of the glass filaments 14 of the edgewise laminations 12 by means of 167 of Fig. 43, that this is in addition to or auxiliary -to the tensioning also given these filaments when and if they are glued into the frame when the frame or frame assemblage is temporarily distorted outward, particularly with regard to the inturned arch 2, as previously outlined. This will be taken into consideration in determining the degree of pressure applied with 167. Of course either one of the tensioning means may be omitted and reliance placed on one alone. Where a pre-glued type of tensile reinforcement as 15 of Fig. 8 is used in place of 12 of Fig. 7 for the edgewise laminations 12, the pre-tensioning as by 167 cannot be employed although, in accordance with recognized practice, the prefabricated lamina may have glass filaments bonded while in tension therein, or in the case of 15 of Fig. 8 my tensile filaments 14 may be drawn and stretched within the tube 13 in the pre-fabrication `of 15 by tensioning means similar to 167 employed in Fig. 43. Also it will be noted that whereas the face laminations 12, because of their horizontal position cannot have their filaments 14 tensioned by 167 or similar means Without pulling out of position particularly in the vital arches 8-'-2-8, nevertheless do have both their filaments 14 and those of the tube 13 stretched or tensioned by being glued to the edgewise laminations while the latter are distorted outward temporarily in the arch 2, etc., while the gluing or adhesive bonding is being perfected. The same applies to 16 of Fig. 9 when same is used alternatively for the face laminations of Fig. 1 in lieu of 12 of Fig. 7.
It should be also noted that in the coating of the filaments of 12 and the like with the bonding adhesive that only the requisite and not an excessive amount of adhesive be retained thereon and in the assemblage. Toward this end, I preferably insert the filaments 14 in the tube 13 (forming 12) and submerge same in a tank bath of the liquid adhesive after its being and While exposed to a vacuum which removes the air and forces vthe adhesive throughout the assemblage which in turn passes through a series of alternate vertical and horizontal pairs of rollers, or equivalent, in the bath, so that the uid is distributed thoroughly through the mass. The excess adhesive fluid is then removed as 12 passes through a nal pair of roller wringers above the bath in leaving the latter. Glass filaments, having no porosity, do not as readily retain uncured adhesive as do vegetable or porous fibers. Accordingly, when necessary or desired, I mix throughout or with the bundle of glass filaments i4 of l2, some strong vegetable or porous bers, as sisal for example, in proper proportions which can also be varied for lightening of weight where such is also a consideration. `As the fluid adhesive impregnates pores of these porous tigers, this is taken advantage of so that in the final press forming, as in Figs. 43 and 44, a proper excess amount of adhesive carried in pores of the porous libers can be squeezed out onto adjacent glass lilaments or through the assemblage so assuring better coating and `bonding of same in the final structure. Such fiber mixtures, proportioned to suit, I also use in the lighter-weight rackets in any or all parts when and as desired. Throughout the frame the materials employed may be greatly varied in substance and in combination without departing from my invention. Throughout the drawings it will be understood that glue lines are represented as the contact line of adjoining laminations and parts that are integrated in the structure by adhesive and the bers or filaments are indicated as in their adhesive coated contour. No attempt is made to depict accurately, fully or otherwise, allowance for compression of the materials and in different directions which will or may occur in the molding and adhesive integrating which will vary with the nature of the materials employed, etc., and must be properly provided for in each respective case in the design of molds, dimensioning, etc. The assemblage and forming procedure may also be greatly varied and modified as well as the shapes.
Thus, while l have shown and described my invention in a preferred form, l am aware that various changes and modications may be made therein without departing from the principles of the invention, the scope of which may be determined by reference to the appended claims.
I claim as my invention:
l. A racket frame having a curvilinear head portion subject to torsional and shearing stresses and designed to hold tight Stringing under pressure and including a plurality of elongated laminations, including at least one wood strip, bonded with an adhesive substance to the exterior of a longitudinally extending tubular element including elongated tensile filaments combined with adhesive and in braided formation and so as to particularly provide substantial structural reinforcement against torsional and shearing stresses and extending along said head portion at least at a point subject to such stressing.
2. A racket frame having a curvilinear head portion subject to torsional and flexural stresses and including as a structural part thereof at least one longitudinally extending braided tubular element, formed with tensile material of high tensile strength, and a plurality of individually formed, longitudinally extending structural tensile filaments separate therefrom but contained therein and bonded with a hardened adhesive substance to said tubular element', said tubular element and said tensile laments extending along said head portion at least at a point subject to said stresses.
3. A racket frame having a curvilinear head portion subject to torsional and shearing stresses and including at least one longitudinally extending braided tubular structural element disposed to resist such stresses and support under pressure tight Stringing which is vulnerable to abrasion and including tensile filaments, at least some of which are of an abrasive nature, coated with a hardened adhesive substance and at least one elongated strip of substantially noni-abrasive material adhesively bonded to said element and interposed between same and said Stringing.
4. A racket frame including in the outer half of the head opposed laminations strutted apart by a plurality of edgewise laminations disposed at an angle to same, said opposed laminations forming humps on the frame with at least the greater portion of the peak of the hump disposed outward from the central transverse axis of the head.
5. A laminated racket frame having a curvilinear head portion subject to distortion and flexural stresses and having opposed longitudinally extending structural face overlays strutted apart by a core adhesively bonded therewith and between same, said overlays being channel-shaped in cross-section so as to thereby more strongly resist the ilexing of the racket and securely embrace the core within said channels and so also better resist distortion of the head portion and splitting of the core.
6. A resilient racket head frame forming an enclosing head portion for receiving Stringing therein under strong tension and including at least one inturned string-supporting arch with at least one strong tensile reinforcing lamination including longitudinally extending glass fibers adhesively bonded in said frame and inturned arch portion and with its liber structure in such stress relation therewith as results when effecting said bonding while at least a portion of said inturned arch is temporarily distorted outward of the head and at least a portion of said reinforcing lamination, designed to form a strong tensile reinforcement for said inturned arch, is distorted inward of the head so that when said portion of said arch and said portion of said reinforcing lamination, after being so adhesively bonded together in the above described stress relationship, are bent further inward of the head in stringing or in play, said reinforcing lamination is more highly stressed in tension than said portion of said arch.
7. A resilient racket frame having a curvilinear head portion designed to hold tight stringing under pressure and having an inturned arch at its outer extremity particularly subject to distortion, said arch being reinforced against said stresses by thickening of the frame along surfaces of said arch and the head at the same time so strengthened to resist the normal tendency of the head to hinge inward on the rackets central longitudinal axis with ball impact on the Stringing.
8. A racket frame subject to tiexural, shearing and torsional stresses and including a plurality of spaced-apart, exteriorly positioned laminations disposed at a zone subject to such stresses connected by interposed elongated structural filaments of high tensile strength and coated with a hardened adhesive substance, certain of said ila,
ments being disposed in braided tubular formation and particularly providing against shearing and torsional stresses and being in combination with other unbraided filaments particularly providing against iiexural stresses, said filaments and laminations being bonded together by a hardened adhesive substance.
9. A racket frame subject to flexural, shearing and torsional stresses and including at least one longitudinally extending, exteriorly exposed lamination disposed at a zone subject to said stresses bonded with an adhesive substance to strong tensile structural filaments coated with an adhesive substance and disposed in helical tubular formation designed to resist shearing and torsional stresses, and extending in opposite diagonal directions.
10. A racket frame subject to tiexural, shearing and torsional stresses and including at least one longitudinally extending non-metallic lamination disposed at a zone subject to such stresses bonded with a hardened adhesive substance to elongated glass ilaments coated with a hardened adhesive substance and disposed in helical tubular formation designed to resist shearing and torsional stresses.
1l. -'A racket frame having a curvilinear head portion subject" to torsional and shearing stresses and including a lplurality.,olf; longitudinally extending thin walled tubular ..ele ments, each comprising elongatedstructural filaments 31 of strong tensile material coated with a hardened adhesive substance and disposed in helical formation to resist, and at a zonesubject to, said stresses, said elements being bonded together by a hardened adhesive substance and extending along at least a substantial portion of said head.
12. A racket frame having a curvilinear head portion including at least one elongated textile structural tube with filaments disposed diagonally to the longitudinal axis thereof in combination with a separate structural layer comprising a multitude of small, elongated tensile elements designed to resist longitudinal flexural stresses, said filaments and said elements being at a zone subject to said stresses and being coated and bonded together with an adhesive substance, and said tube being designed to resist torsional and shearing stresses to which said head is sub- 'ected.
] 13. A racket frame having a curvilinear head portion subject to shearing and torsional stresses and including at least one elongated structural textile tubular element formed with elongated structural tensile laments at a zone subject to said stresses and disposed in helical formation and a plurality of small, elongated structural tensile filaments grouped within said element, the various laments being bonded together by a hardened adhesive substance and at least some of said filaments being so held in tensioned condition.
'- 14. A racket frame having a curvilinear head portion and including at least one non-metallic, light-weight, longitudinally extending core portion enclosed by elongated structural tensile filaments disposed in helical tubular formation at a zone subject to shearing and torsion with larnents crossing each other in opposite diagonal directions, said core portion and said filaments being bonded together by a hardened adhesive substance.
15. A racket frame having a curvilinear head portion designed to hold under pressure tight Stringing vulnerable to abrasion and including a plurality of longitudinally disposed structural braided tubes including strong elongated tensile filaments, said tubes having substantially non-abrasive material interposed between them designed to receive Stringing holes and support said Stringing and said filaments being bonded together and to said material by a hardened adhesive substance.
16. A racket frame having Ka curvilinear head portion with an inturned arch in its outer extremity designed to spring inward of the head when the frame is strung and in play and a highly resilient, spring-like, arched lamination bonded with an adhesive substance to the soit of said inturned arch, said lamination having a plurality of small projecting points formed therewith as an integral part thereof which project into said frame in such manner that as said inturned arch springs inward the grip of said points and their pressure into said frame is increased. 17. A racket frame having a curvilinear head portion subject to torsional and shearing stresses in addition to exural stressing and including opposed longitudinally extending structural laminations disposed at a zone subject to said stresses comprising braided tubular elements formed with strong elongated structural tensile filaments v`in` braided formation and containing other strong longiudinally disposed structural tensile filaments therein, said laments being coated and bonded together by a hardened *adhesive substance.
' glia/"A racket frame including filaments of material offliigh tensile strength, including glass, extending conltinuously the entire length of the frame and under tennsion and with the opposed ends of said filaments terminating in the handle end of the -frame and with both the opposed ends of the laments held with the same equally drawn tension by a hardened adhesive substance.
19. A racket frame including at least one lamination reinforcing the sides of the head portion along its inner perimeter and substantially spaced away from the neutral axis of the frame and terminating as cantilevers with the opposed ends curving toward each other and terminating in the outer end of the racket head in combination with, abutting against the soit of, and serving to help support, an inturned arch formed between same and tending to spring inward of the head with string pressure.
20. A racket frame including laminations reinforcing the sides of the head portion for at least a substantial length thereof along its inner perimeter and substantially spaced away from the neutral axis of the frame and terminating as cantilevers with opposed ends curving toward each other and terminating in the outer end of the racket head in combination with, abutting against the soiiit of, and serving to help support, an inturned arch formed between same and tending to spring inward of the head with string pressure.
2l. A racket frame including cantilever portions in the head framing and terminating in the outer end and on the inner perimeter thereof, said cantilever portions including material of substantially higher tensile strength bonded to the tension side thereof and in combination with an interposed inturned arch which tends to spring inward of the head with string pressure.
22. A racket frame including cantilever portions in the head framing and terminating in spaced apart relation in the outer end thereof and substantially inward of the head in relation to the neutral axis of said frame, said portions -being under tension so that their outer terminating ends normally tend to spring outward of the head in cornbination with and serving to help support an inturned arch extending between same and tending to spring inward of the head with string pressure.
23. A racket frame including cantilever portions in the head framing and terminating in spaced apart relation in the outer end thereof and along its inner side, said portions being reinforced on their tension side with material of substantially higher tensile strength and said material also forming a lamination of the frame spanning the gap between the outer terminal ends of said portions and in combination with an inturned arch spanning between said cantilever portions and tending to spring inward of the head with string pressure.
24. A racket frame having a curvilinear head portion subject to torsional, shearing and flexural stresses and including at least one tubular element formed with lbraided tensile filaments extending substantially around the head and forming a container for a multitude of tensile laments disposed therein, the various la'ments being held by a hardened adhesive.
25. A racket frame including in the outer half of the head opposed humps on the faces of the frame with at least the greater portion of the peak of the hump disposed outward frorn the central transverse axis of the head.
26. A racket frame subject to extreme torsional, ilexural, shearing and delaminating stresses and including longitudinally extending laminations disposed at a zone subject to such stresses with their opposed faces adhesively joined together and having at least some of the sojoined laminations cross-bonded together diagonally across their edges by elongated glass filaments extending in helical formation as a substantial structural element of said frame and coated, reinforced and bonded to said edges by a hardened adhesive substance.
References Cited in the le of this patent UNITED STATES PATENTS 823,028 Brown June 12, 1906 1,532,991 De Meza Apr. 7, 1925 1,621,746 Morten Mar. 22, 1927 1,637,583 Norton Aug. 2, 1927 1,921,616 Hall Aug. 8, 1933 (Other references on following page) 33 UNITED STATES PATENTS Robinson Oct. 10, 1933 Nash Nov. 27, 1934 Davis Oct. 11, 1938 Le Compte et a1 Nov. 12, 1940 Le Compte May 5, 1942 Hall May 12, 1942 Andreef Nov. 30, 1943 Geerlings et al. Mar. 5, 1946 Rheinfrank Ian. 14, 1947 Collins Sept. 30, 1947 Rodgers etal. Oct. 30, 1951 34 Francis July 8, 1952 Robinson Jan. 27, 1953 FOREIGN PATENTS Australia Aug. 10, 19.01 Great Britain Nov. 24, 1924 France Apr. 28, 1928 Great Britain Oct. 18, 1928 France Nov. 5, 1930 Australia Apr. 11, 1934 Australia May 4, 1938 Great Britain Feb. 7, 1947 Great Britain Aug. 3, 1949
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|U.S. Classification||473/535, 156/91, 138/141, 156/172, 156/285, 87/6, 156/190, 156/247, 138/145|
|International Classification||A63B49/02, A63B49/10|
|Cooperative Classification||A63B49/10, A63B2049/103, A63B2049/0211|