US 3912268 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
United States Patent [191 Robinson [451 Oct. 14, 1975 GAME RACKET  Inventor: Mark L. Robinson, Newburyport,
 Assignee: Acro, Inc., Stoneham, Mass.
 Filed: Feb. 19, 1974  Appl. No.: 443,394
 US. Cl. 273/73 H  Int. Cl. A63B 49/12  Field of Search.... 273/73 R, 73 C, 73 D, 73 E,
273/73 G, 73 H, 73 J  References Cited UNITED STATES PATENTS 1,452,803 4/1923 Harris 273/73 H 1,862,581 6/1932 Robinson.... 273/73 H 2,171,223 8/1939 Robinson.... 273/73 H 2,456,023 12/1948 Rosenbalm 273/73 H X 3,540,728 11/1970 Palmer 273/73 H 3,633,910 l/1972 Spenle 273/73 J 3,664,669 5/1972 Latham et a1 273/73 H X FOREIGN PATENTS OR APPLICATIONS 1,578,059 8/1969 France 273/73 G Primary Examiner-Richard J. Apley Attorney, Agent, or FirmCharles Hieken; Jerry Cohen  ABSTRACT An aluminum g ame racket comprises a continuous extruded channel bent to form head, throat and handle portions of the racket. Opposed, parallel, closely spaced legs of the channel forming the handle portion are spanned by a lateral strut assembly comprising a steel wire tied to the opposing legs via wire end holders to prevent leg separation and enhance the torsional and bending characteristics of the racket as a whole while limiting the induction of creep strain or strut loosening by repeated impacts on the racket head.
11 Claims, 3 Drawing Figures US. Patent 0ct.14,1975 3,912,268
GAME RACKET BACKGROUND OF THE INVENTION The present invention relates in general to game rackets and more particularly concerns a novel game racket having high specific stiffness, particularly torsional and bending rigidity, consistent with the excellent playing characteristics of aluminum rackets such as the Smasher and Seamless brand rackets and ease and economy of manufacture of the latter rackets. These rackets are described in U.S. Pat. Nos. 3,664,669 and 3,625,512.
It isan important object of this invention to provide a game racket with high specific stiffness, particularly torsional and bending rigidity. A
It is a further object of the invention to enhance the playing life of the racket consistent with the preceding object.
It is a further object of the invention to extend the playing life of game rackets used by players of limited skill consistent with one or more of the preceding objects.
It is a further object of the invention to provide a game racket with excellent playing characteristics consistent with one or more of the preceding objects.
It is a further object of the invention to provide a game racket that is relatively easy and inexpensive to fabricate and especially suitable for manufacture by automatic techniques consistent with one or more of the preceding objects.
It is a further object of the invention to maximize the use of lightweight materials such as extruded aluminum, or other suitable materials, consistent with one or more of the preceding objects.
It is a further object of the invention to achieve one or more of the preceding objects while absorbing shock without reducing touch control and enabling the player to hit the ball off center without feeling vibration stresses and torsional strains.
It is a further object of the invention to achieve one or more of the preceding objects with a racket characterized by good balance.
SUMMARY OF THE INVENTION According to the invention, a game racket comprises head and handle portions and a lateral strut assembly extending between opposed elongated legs which together define at least part of the handle. The assembly comprises a tension member, a pair of tension member holders locked onto the opposing legs and holding ends of the tension member in mechanically locked but metallurgically unbonded engagement for preventing leg separation. The .holding members comprise back-toback outwardly facing channels with respective channel bases separated from each other by a distance I which is less than half of the leg-to-leg separation distance in the handle. The tension member, preferably a rod or wire of material having at least twice the endurance limit of the racket material, extends through passages in said channel bases and is preferably secured by having its ends bent within said channels. The channels have side walls and extended lengths of their passages for the tension member to provide substantial bearing surface against the tension member for transmission of torsional and bending stresses.
This lateral strut assembly may be compared with a unitary lateral strut such as the frictionally engaged,
one-piece beam of dogbone form found in the commercially available Seamless brand model AR-2 racket or the welded in dogbone struts used in some commer- 'cially available rackets. The above described multi-part strut assembly, when substituted for the unitary strut of the AR-2 racket, increases the rackets resistance to unusually high bending and torsional stresses on the lateral strut. The multi-part assembly absorbs these high loadings centrally rather than peripherally as in the unitary strut construction and, it is believed, thereby has less tendency than a unitary strut to work loose from the handle forming legs. The problem of weld breakage which sometimes occurs in the welded or dogbone rackets is entirely avoided.
The multi-part lateral strut assembly flexes under the unusually high loading condition of a hard impact but exhibits the same apparent rigidity as the unitary strut under more moderate loadings. Such flexure avoids the buildup of stresses to elastic limits or other conditions of permanent deformation at the channel overhangs in the framing metal strip. Typically, the flexure of the racket handle is from three to five degrees in response to a hard hit. The flexure is consistent with good playability of the racket. The moment required to bend the tension member is less than the moment required to bend the holding members.
The balance of the racket structure is preferably of the type comprising a continuous aluminum extrusion of channel form bent to form head, throat and handle portions of the racket with a bridge member in the throat having a similar channel form. The channels of the handle, throat and head portions are continuous to allow sliding and insertion of string receiving members therethrough, all as described in said U.S. Pat. No. 3,664,669. Preferably, the racket forming channel has a pair of inwardly extending walls therein between its upper and lower side walls constructed and arranged to spread corresponding upper and lower walls of the string receiving means as further described in U.S. Pat. No. 3,664,669.
The multipart lateral strut assembly comprises a pair of aluminum dogs with projections slidable in the upper and lower tracks formed within each of the channels and clearing the central track formed therein between the two central walls. The bent ends of the tension member extend parallel to the direction of racket handle elongation in said central track of the opposing handle forming legs.
Numerous other objects, features and advantages of the invention will become apparent from the following specification when read in connection with the accompanying drawing in which:
BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an isometric view of a game racket according to a preferred embodiment of the present invention, a portion of one leg of the racket handle being cut away to more clearly show the lateral strut assembly in the handle;
FIGS. 2 and 3 are bottom and side views, respectively, of the multipart lateral strut assembly included in the FIG. 1 game racket, portions of both of the figures being sectioned.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS With reference now to the drawing and more particularly FIG. 1 thereof, there is shown a game racket 10 comprising a head portion 12, throat portion 14 and handle portion 16 terminating in a grip 18. A single continuous aluminum extrusion of channel form is bent to form the entire racket frame. The channel opens inwardly throughout the frame. The handle portion comprises parallel legs 20 and 22 of the frame. The legs are closely spaced within one half to two inches, preferably 1 inch apart. A bridge member 24 seats in and is secured to a throat portion 14 of the racket. String receivers 26 are locked within the channel frame in the head portion 12 and bridge portion 24 to provide tension support for strings 28. The string receivers are insertable into the framing channel at grip end 18 of the handle and slidable into the head positions.
A multipart lateral strut assembly is axially located within the half of the handle closer to the throat (and away from the grip end 18). The assembly comprises holding members 30 and 32 which are slidable within the channels of legs 20 and 22, respectively. A tension member 34 comprising a piano wire of high carbon, cold drawn steel extends between the holding members 30 and 32. The wires endurance limit is 60 to 80 percent of its yield strength (about 180,000 psi). The endurance limit of the aluminum alloy used for the channel legs and holding members is about 7,000 psi or about l/6th of yield strength. Endurance limit, also known as fatigue limit, is the highest stress that a material can withstand for an infinite 73 of cycles of stress application and release without breaking.
The lateral strut assembly is preassembled outside the racket by passing wire 34 through holes in members 30 and 32 and bending exposed ends 34E of wire 34 nearly flat against members 32 with a to outward splay which causes the ends to touch base wall(s) 25 of the channel legs. This arrangement forms a spring clip holding the assembly in place with a good fit while accommodating tolerance accumulations in the handle and lateral strut assembly. The members 30 and 32 may be slidingly inserted into the channels of legs and 22, respectively, moved into axial position and locked by friction or crimping adjacent channel structure. The holders 30 and 32 are mechanically locked within channels 20 and 22, respectively, by overhanging sidewalls described below. The bent ends 34E of wire 34 lock the wire and holders 30 and 32 into the arrangement thereof shown in the drawing. Therefore, the wire prevents the legs 20 and 22 from separating.
Referring now to FIGS. 2-3, the lateral strut assembly is shown in greater detail and in relation to one of the handle forming channel legs 20, it being understood that the relation of holding member 32 to leg 22, (not shown) would be the same as that of holding member 30 to leg 20. Similarly, the detailed components of holding member 30 described below are similar to those of holding member 32.
The leg 20 forms an inwardly facing channel with upper and lower overhanging sidewalls 21 and 23 and a channel base wall and inwardly extending central walls 27. Member has an outwardly facing elongated groove 306 in its base with a base wall 33 and side walls 31. The base wall 33 has a further circular relief 35 for accommodating the bent end of wire 34. The
central portion of wire 34 passes through a hole 36.
The central wall 27 of leg 20, together with base wall 33 of member 30, form an outwardly facing channel 37. The side walls 27 of such channels, together with the long length of hole 36 in member 30, transmit bending and torsional stresses to wire 34. These stresses are therefore absorbed centrally rather than peripherally and have less tendency to loosen the tight engagement of member 30 in leg 20 [or of member 32 in leg 22] over the course of racket usage.
Dimensional relationships among the parts of the embodiment of FIGS. l3 are typically:
D (the spacing between channels, i.e., between bases of the channel legs of the handle) 0.915 in.,
S (spacing between holding members) 0.165, and more generally, sufficiently wide to allow flexure but sufficiently short so that at least half the length 2X S between channel bases is occupied by surfaces of the holding members bearing against wire 34,
X (bearing length of hole(s) 36) 0.258 to 0.278 inches,
relief 35 is circular and has a radius of 0.063 in. centered outside the recess,
and height portions H and H extending upwardly and downwardly from wire 34 are preferably equal to each other and greater than the length A of the bent end(s) of wire 34.
Wire 34 may have a .120 inch diameter and hole(s) 36 may have a 0. -0. 1 30 diameter and are centered within the thickness dimension of the handle. The bent ends of wire 34 bear against walls 25.
The balance and weight of the racket are essentially the same as the Seamless AR-2.
There has been disclosed a game racket which retains excellent playing characteristics and balance and ease of assembly and manufacture at low cost despite frequent hard, off-center hits. Stresses are taken up by allowing flexure of a central tension member with high fatique strength which affords a sufficiently large elastic range for this purpose without significant weight penalty.
It is evident that those skilled in the art may now make numerous uses and modifications of and departures from the specific embodiments described herein without departing from the inventive concepts. For example, the channel construction within the handle legs may be varied and/or limited to the handle portion having the strut assembly. Various other forms of holding member and unbonded, mechanically locked engagement thereof to the legs may be employed. The legs themselves may be constructed to serve as holding means. The strut may be a ribbon instead of a wire. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in or possessed by the apparatus and techniques herein disclosed and limited solely by the spirit and scope of the appended claims.
What is claimed is:
1. A game racket comprising,
means defining a racket head,
means defining an elongated racket handle and comprising spaced, essentially parallel, elongated handle legs which oppose each other across a lateral space of /2 to 2 inches,
means defining a racket throat between said head and handle,
means defining a handle grip portion,
means defining a lateral strut assembly extending between said handle legs and located on said handle between said throat and said grip and comprising a thin tension member for holding said handle legs against separation from each other under conditions of racket loading and transmitting torsional and bending stresses from leg to leg, and
plural separate and spaced apart means for engaging ends of said tension member to said legs in mechanically locked but unbonded engagement allowing flexural movement within said handle, each of said legs having an outwardly facing surface portion,
said outwardly facing surface portions of said legs being essentially parallel to each other,
said engaging means comprising portions which engage the handle legs at said outwardly facing surface portions,
the material of the tension member having a higher endurance limit than the handle material.
2. A game racket in accordance with claim 1 wherein the cross sectional shapes of said legs form opposed, inwardly opening channels with bases and overhanging sidewalls, and wherein said engaging means comprise a pair of holding members mechanically locked within said channels by the overhanging side walls thereof.
3. A game racket in accordance with claim 2 wherein said holding members have long holes running substantially the full length of said holding members in a line essentially at right angles to the handle length direction and crossing both handle legs with internal surfaces bearing against said tension member over a length portion thereof which comprises at least half the spacing between handle legs.
4. A game racket in accordance with claim 1 wherein said thin tension member is essentially centered within the thickness dimension of said handle.
5. A game racket in accordance with claim 1 wherein said thin tension member is a wire.
6. A game racket comprising,
frame means having opposed legs defining together the frame of a head portion, a throat portion and an elongated handle portion,
the cross-sectional shape of said frame means having at least part thereof curved in an arcuate shape to form a channel on the inside of the arc,
said channel being bounded on one side by the inner wall of said frame and having upper and lower grooves formed by upper and lower overhanging walls of said frame to means in each of said head, throat and handle portions forming an essentially continuous track,
means defining a lateral strut assembly extending between said legs and comprising a tension wire for holding the legs against separation from each other under conditions of racket loading, and 5 means for engaging ends of said tension wire to said opposing legs in mechanically locked but unbonded engagement, said engaging means comprising a pair of plural separate and spaced apart holding blocks which are contoured to mechanically lock within the upper and lower grooves of said channel track in sliding engagement therewith forming sleeves containing spaced parts of said wire,
said blocks being located in opposing relation to each other within confronting channel sections in the half of the handle nearest the racket throat.
7. A game racket in accordance with claim 6 and further comprising,
string support means substantially filling said inside channel of said head portion and having a hollow string receiving portion for receiving a game racket string.
8. A game racket in accordance with claim 7 and further comprising,
bridge means located adjacent to the lower portion of said head portion and removably engaged therewith for keeping both legs of said frame means apart and in fixed relationship and to help define a racket head,
said bridge means having an inner channel to define together with the channeling of said frame head portion a complete closed loop of channeling around the racket head.
35 9. A game racket in accordance with claim 8 and further comprising,
a number of said string support means in contiguous relationship about said head portion slidingly engaged in said bridge channel.
10. A game racket in accordance with claim 9 and further comprising,
racket strings in the hollow string receiving portions of said string support means.
11. A game racket in accordance with claim 6 wherein ends of said tension wire are bent substantially towards the blocks and splayed out against the inner wall of said frame between said upper and lower grooves thereof so that the wire forms a spring clip.