US 3523378 A
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Description (OCR text may contain errors)
Aug. 11., 1970 Filed A ril 10. 1968 w.. MITCHELL E AL SLIPPERS 4 Sheets-Sheet 1 INALEE 5 K%%f W JAMES G. MITCHELL Aug 11, 1970 w. rrc ETAl; 3,523,378
I SLIPPERS 4 Sheets-Sheet Filed April 10. I968 M/VE/WORS INALEE G.MITCHEL..L JAMES G.MITCHELL ymfi/ FIGS Aug. 11,1970 w, rr ETAL 3,523,373 I SLIPPERS Filed April 10, 1968 I 4 Sheets-Sheet 4 INVENTORS H2 WINALEE 5. MITCHELL JAMES c. MITCHELL BY flm? ATTORNEY 3,523,378 SLIPPERS Wmalee G. Mitchell and James G. Mitchell, both of 205 Farnsworth Road, Water-ville, Ohio 43566 Filed Apr. 10, 1968, Ser. No. 720,016 The portion of the term of the patent subsequent to Feb. 11, 1986, has been disclaimer] Int. Cl. A43b 3/10 US. Cl. 362.5 4 Claims ABSTRACT OF THE DISCLOSURE Slippers having an upper joined to a lower blank of elastomeric sheeting material which increases in width but the marginal edges thereof taper inwardly and upwardly toward the heel where the left and right sides are joined in a heel seam which is at least partly forwardly inclined. Also, a method of making such slippers including the steps of simultaneously cutting and bonding an upper with a lower blank having lateral edges which, in the rearward direction are from about parallel to divergent, folding the lower blank on about its longitudinal axis and bonding the folded left and right sides together along a heel seam which is at least partly forwardly inclined.
RELATED APPLICATIONS This application discloses subject matter which is common to it and to our prior copending applications Ser. No. 451,181, filed Apr. 27, 1965, and 634,426 filed Apr. 24, 1967.
BACKGROUND AND OBJECTS Heretofore there has been a need for strong, sanitary and inexpensive footwear and for efiicient methods of manufacturing it. This need has been met to a substantial extent by the footwear and production methods disclosed in our US. Pat. 3,238,079. Plastic slippers fabricated in accordance with the teachings of that patent are enjoying widespread and steadily increasing commercial use where paper slippers (or none at all) were used previously. Considering the thin guage of plastic foam sheeting which must be used to permit economical pricing, and the fact that the slippers are held in place on the wearers foot, in part, by internal elastic tension in the plastic foam material, they display a surprising degree of resistance to tearing while in use. This is particularly true of slippers made in small and medium sizes andto a lesser extent of larger silppers. However, in the case of the largest men's sizes some difiiculties have been experienced.
With the retention of the slippers in place on the wearers foot depending as its does on the stretching of the plastic material, the slippers must be of smaller dimensions than the size of the foot for which they are intended. It has been found however that when slippers intended for the largest sizes of feet are made small enough to provide the requisite internal tenison to keep them in place, they do not provide sufficient coverage of the wearers heel, and when made large enough to adequately cover the heel are not stretched sufliciently to keep them securely in place. Accordingly a need remains for improvements in plastic slippers and methods of making them which make available both adequate coverage for the wearers heel and satisfactory retention qualities.
It is a principal object of this invention to fulfill this need. Other objects of the invention will be apparent to those skilled in the art from the following description of our footwear and method inventions and certain nonlimiting embodiments thereof.
United States Patent 'ice BRIEF SUMMARY OF THE INVENTION The foregoing object can be met with a slipper comprising an upper attached to a sole or lower blank of elastomeric sheet material, the marginal edges of which taper upwardly and inwardly at points successively closer to the heel. At the heel, the left and right sides of the lower blank join one another in a generally upright seam which is at least partly forwardly inclined for gripping the wearers heel. This seam and such other seams as may be required to join the upper to the lower blank may be based upon any effective method of joinder, such as sewing, cementing, thermal sealing, induction sealing and the like. The term elastomeric is intended to include any material, natural or synthetic, characterized by flexibility and stretchy elasticity, and is preferably, though by no means essentially, spongy; that is, the material preferably includes cellular structure. A preferred example of such a spongy material is open-celled polyurethane foam, a synthetic elastomeric material which may be produced by blowing a' polyester resin with a diisocyanate compound. Such materials are readily available commercially in sheet form from a number of suppliers and are readily amenable to the various methods of joinder described in our US. Pat. 3,238,079, the disclosure of which is hereby incorporated by reference.
Generally speaking, the method we have invented involves a series of steps, including: bringing a first layer of heat-scalable elastomeric material and a substantially wider second layer of heat-scalable elastomeric material into face-to-face relationship with one edge of each layer being substantially aligned with one edge of the other to provide in said second layer a covered portion which is in face-to-face relationship with the first layer and an exposed portion which is not in face-to-face relationship with the first layer; in a first bonding operation, uniting said layers to form therein the toe portion of a slipper by subjecting the first layer and the covered portion of the second layer to sufiicient heat and pressure to form a heat-sealed bond between them in a first narrow region having two branches extending away from said substantially aligned edges and spaced apart from one another by approximately the width of the toe and instep of a human foot of predetermined size; while still under the pressure' bf said first bonding operation, cutting the material of the first and second layers along the first narrow region; cutting the exposed portion of the second layer along lines extending from the ends of said branches in a direction away from the aligned edges of the layers to form a blank having its longitudinal axis extending away from the said aligned edges and separating the blank from the remainder of the material of said layers; folding the material of the exposed portion of the second layer inthe blank on either side of the longitudinal axis thereof into face-to-face relationship in a plane generally perpendicular to the first narow region; and, in a second bonding operation, forming the heel of a slipper by subjecting the folded exposed portion of the second layer to sufficient heat and pressure to form a heat-sealed bond in a second narrow region which is spaced longitudinally of said blank from said first layer and is in a plane generally perpendicular to said first region.
Although the terms first layer and second layer may in some contexts connote two separate pieces of material, these terms are used herein not only with that connotation in mind, but also to refer to diiferent portions of the same piece of material which has been folded upon itself to form two or more layers.
Heat-scalable material refers to any supple synthetic polymeric web which may be bonded to itself and to other materials by coalescence or melting together under the action of pressure and heat, whether induced thermally or electronically.
When it is stated that edges of the layers are substantially aligned, it is not required that these edges exactly coincide or even be precisely parallel, although such is definitely preferred from the stand-point of production efiiciency and avoiding waste of material; it is sufii cient if the edges be approximately parallel and adjacent to one another.
The face-to-face relationship referred to above does not require the layers to contact one another over their entire adjacent surfaces. For instance, the layers may be closely adjacent to one another but separated prior to bonding by a layer of thin, loosely woven cloth or scrim material through which the heat-sealable materials of the respective layers may flow during the bonding operation to form a seal, thus enveloping and bonding the cloth or scrim material in the seal between the layers and enabling it to serve as a liner in the finished slipper. Thus, it is apparent also that the method as stated above comprehends the formation of slippers having two or more layers of one or more different materials. The usual practice however will be to employ a single kind of synthetic polymer foam webbing material in a construction which includes just a first and second layer, except that the first layer may, for strengthening and/or decorative purposes be folded upon itself in a manner to be described hereinafter.
The extent to which the second layer is wider than the first is dependent upon how much of the wearers instep it is desired to have covered by the slipper, and how much waste can be tolerated in the manufacturing process. Generally, the second layer will be about 1.5 to about times as wide as the first layer, measured between the first and second regions.
The two branches of the first narrow region refer to those portions of the heat seal between the first and second layers which extend respectively along the right and left sides of the toe portion of the slipper. These branches may meet in the manner of the arms of a V if a pointed toe is desired or may meet in the manner of the arms of a U or any other suitable manner.
The aforesaid first and second regions may be continuous or discontinuous, as it is known to produce heat seals which are continuous or which are closely adjacent increments of sealed material longitudinally interspersed with unsealed or only partially sealed material. When the first and second layers are of different colors, this provides a vari-colored seal of pleasing appearance.
Although the cutting of the blank should take place while the first region is still under the pressure of the bonding operation, this should not be construed as requiring that the bond should be complete at the time cutting takes place. The cutting may occur before, during or after formation of the bond. The term cutting is intended to be construed broadly to cover cutting, shearing, tearing and generally any other suitable mode of separating the blank from the remaining portions (e.g. waste) of the first and second layers. The cutting along the first narrow region may be performed along the outer edge of the region, or even within the region, in which event part of the seam remains with the blank and the remainder goes with the waste. This cutting operation is best though not essentially--performed simultaneously with the cutting of the exposed portion of the second layer to complete the cutting of the blank in one operation.
The lines along which the exposed portion is cut pref erably diverge from one another as they extend away from the toe portion. Experiments have shown that the lines may converge some, but as the angle of convergence increases, the height and therefore the gripping capabilities of the heel are reduced. Therefore, it is preferred that the angle between the aforesaid lines he in the range of about 0 to about 90.
4 BRIEF DESCRIPTION OF THE DRAWINGS Illustrative, non-limiting preferred embodiments of the present footwear and method inventions are depicted in the accompanying drawings, in which:
FIGS. 1 through 3 are side, front and rear elevations (non-wearing position) of a novel slipper corresponding with the invention;
FIGS. 4 and 5 are perspective (wearing position) and top plan (non-wearing position) views of the aforementioned slipper;
FIG. 6 is a partly sectional schematic illustration of a method by which plastic slippers may be produced;
FIGS. 7 and 8 are sectional views taken along section lines 7-7 and 88, respectively, in FIG. 6;
FIG. 9 is an enlarged detailed view of a portion of FIG. 6;
FIG. 10 is a top plan view of a fragment of the material used in the process as it appears when clenched in the die shown in FIG. 9;
FIG. 11 is a perspective view of apparatus for forming the heel seam and of the lower blank folded for insertion therein; and
FIG. 12. is a showing of the slipper after withdrawal from the apparatus of FIG. 11, the material removed by such apparatus being shown in phantom outline.
DESCRIPTION OF PREFERRED EMBODIMENTS (1) Slipper The non-limiting illustrative embodiment of a slipper shown in FIGS. 1-5 includes an upper 20 having a foldedover portion 21 at its rear edge 22. The folded-over portion 21 provides extra strength, but may be omitted. In such case, edge 22 need not be straight and may have various decorative outlines, such as wavy, curved or serrated.
The sole or lower blank 23 is joined to the upper along a seam of fused material 24 such as is formed by a thermal heat-sealing and cutting procedure and apparatus of the type hereinafter described. For convenient description, the lower blank is referred to hereinafter as having a toe or covered portion 26-which is that portion which coincides with and is covered by the upperand a rear or exposed portion 27which includes all of the lower blank to the rear of rear edge 22 of the upper. The toe portion of the lower blank, and the upper are generally horizontally disposed and have a width and a shape which are generally conformable to those of a human foot, but the shape may be varied freely in accordance with the dictates of convenience and fashion. When the upper is provided, with a folded-over portion 21, it is beneficial to have that portion joined to the remainder of the upper and to the lower in seam 24 as shown in FIGS. 1-5. In any event, the rear edge 22 of the upper extends from one lateral edge 28 to the other lateral edge 29 of the lower blank and is free of attachment to said blank except at said lateral edges, thereby providing a sort of pocket for insertion of the wearers toes, which pocket may be open, closed, rounded fiat or pointed at the toes, as desired. The longitudinal position of rear edge 22 may be moved forward or backward as desired so long as adequate room for insertion of the wearers foot and satisfactory coverage of the toes are provided.
In accordance with the preferred embodiment of the invention, the lower blank 23 has a rearwardly divergent Width; that is, the width of the material in the blank, measured flat, increases when measured perpendicular to the longitudinal axis of the slipper at a plurality of points successively closer to the heel. Such divergency may exist only in the exposed portion of the lower or in both the exposed portion and covered portion, the latter being the preferred mode which is disclosed herein. The angle of divergence, measured between the marginal edges of the flattened lower blank, should be substantial, e.g. at least about 10. Angles of divergence of about 10 to about 45 are preferred, with an angle of about l8-20 being considered best. Larger angles can be used, but the amount of waste material produced in the making of the slippers increases as the angle is increased. Thus, when we state that the contemplated range of the angle of divergence is from about 10 to about 90, there is no intention of ruling out larger angles. About' 90 is recited merely as the angle beyond which the economic penalty associated with widening the angle of divergence is believed sufficiently great as to make any further increase undesirable from the stand-point of efiicient manufacturing practice.
It is a feature of the invention that there is, in the rear portion of blank 23, a tapering inwardly and upwardly of the lateral edges 28 and 29 toward a vertical plane 30 (FIG. 3) which passes through the slipper about at its longitudinal axis. The material of the exposed portion of the lower bends upward as it passes through this plane with the radius of curvature in the bend gradually increasing (while the slipper is not being worn) at points along the axis successively closer to the heel. At the extreme rear of the exposed portion the left 33 and right 34 sides of the lower blank join and are bonded with one another along a heel seam 31. A portion 32 of this seam is inclined forwardly to grip the wearers heel. The remainder of the seam may incline backwardly or forwardly to provide a smooth-fitting heel or various decorative effects. Preferably, the heel seam 31 is in the form of a smooth curve which, at. its lower end, lies approximately tangent to the bottom of the lower blank, and at its upper end, intersects the marginal edges 28 and 29 at an acute angle, said angle being measured with the slipper folded along its longitudinal axis with the inner surfaces of sides 33 and 34 in face-to-face contact.
The slipper of the herein disclosed preferred embodiment is further characterized in that the lower blank 23 extends as a single, continuous layer of elastomer foam material from one marginal edge to theother, so that one and the same piece of material serves as the sole, sides and heel of the slipper. Because said layer is preferably formed into a heel portion by a generally upright single seam which unites the material on the left side of the longitudinal axis of the slipper to that on the right, the sides and rear of the slipper can be formed from the folded blank in a single operation without the necessity of any horizontal seaming, as is required in most conventional shoe, slipper and moccasin configurations.
In a commercial embodiment of the herein described slipper, the radius of curvature of the leading edge of the toe portion is about 2". The angle of divergence of the lateral marginal edges of the upper and lower, measured with the lower blank flattened against a planar surface, is about 18-20. The upper, measured from the front to the rear edge, at the longest point, is about long. The folded over portion is about 2" long. The width of the upper, measured along its rear edge is about 5%". The over-all length of the slipper, measured along its longitudinal axis is about 12". The radius of curvature of the heel seam is about 4 /2".
Persons skilled in the art will readily recognize that slippers of the above-described type may readily be fabricated by hand or by machine and by a variety of methods. However, We have found that they can be manufactured with particular efficiency by the method of the present invention, an illustrative preferred embodiment of which will be described below.
(.2) Method A preferred embodiment of the above-described method is best illustrated in FIG. 6, wherein a first strip or layer of thermoplastic, heat-sealable polyurethane open or closed cell foam 40, preferably the former, is removed from its storage roll 38 and advanced by rollers 62 to a folding station 81. The advancing strip of foam material 40 first strikes the upright angular element 82 and approximately of the width of the material is raised in an upright, angular relationship to the advancing main portion of strip 40 as shown in FIG. 7. Immediately thereafter, the upright portion 40A is folded over upon the main portion of strip 40 as illustrated in FIG. 8. This folding is accomplished by the use of form 83, and once established, the advancing strip itself tends to serve as its own guide means to provide a double layered advancing strip of material, the double layer extending approximately Va the width of the advancing strip.
Simultaneously, a second strip or layer 48 of the same material is advanced from storage roll 47 by guide rollers 84 and 85, and is brought into face-to-face contact with the double-layered strip 40 at feed rollers 58 and 59. The second strip 48 may be cellular or non-cellular, although foam material is definitely preferred, since a more comfortable slipper will result. Alternatively, the first sheet may be non-cellular material and the second cellular. It is also possible to provide a double sole in the slipper. For instance, the upper would be either of cellular or non-cellular material and the lower would be in two layers, one of foam, the other of non-cellular material. There would be no departure from the present invention in making such modifications, since the substitution of cel lular material for non-cellular material or the replace ment of a single strip of one kind or the other with two strips, one of each kind, would not alter the sequence or relationship of the essential steps in our process. Therefore, although we will proceed with a description which refers to both the first and second strips as being of foam material, no intention to exclude any of the above modifications or others should be inferred.
The strips 40, 40A and 4-8 are preferably advanced through cutting and sealing station 86 incrementally. That is, their advancement occurs in a series of successive, left-to-right longitudinal movements of equal length, each movement being followed by a short period in which the strip is stationary. The cutting and sealing station functions each time the material comes to rest, resulting in the formation of a series of slipper blanks that are spaced apart from one another along the strip of material. However, those skilled in the art will readily recognize that the above method may be practiced with a variety of equipment and in different modes. Thus the material may be advanced relatively continuously with the fabricating steps being preformed by flying punches, cutters and dyes. Or, in the preferred embodiment, as previously indicated, material may be advanced incrementally as illustrated in FIG. 6.
At the cutting and sealing station 86, there is a stationary lower sealing die '67 having an upwardly disposed horizontal die face 51 as illustrated in FIGS. 6 and 9. This die is provided with a heating element 53 by means of which the die face 51 can be raised to the fusion temperature of the thermoplastic foam material in strips 40 (including 40A) and 48. Directly above die face 51 and in registry therewith is a substantially identical downwardly disposed horizontal die face 50 of upper sealing die 66 as illustrated in FIGS. 6 and 9. Die 66 is provided with heating elements 52, similar to heating elements 53.
Unlike lower die 67, upper die 66 reciprocates vertically. By means of any suitable reciprocating motor means 57, the upper die 66 is pressed firmly into contact with the strip 40 and 40A each time it comes to rest and is retracted before the material begins to move again. Thus, during those periods when the strips 40 (including 40A) and 48 are stationary, they are compressed for a time between the dies 66 and 67.
A shearing-type cutter 56 is associated with the upper die 66. As will be noted from FIG. 9, the cutter is fitted closely about the entire periphery of die 66. Because the die 66 and 67 have vertical walls and meet in substantially perfect registry, the cutter 56 can separate the material clenched in the die from that lying outside of it.
In order to more fully disclose how the cutting and sealing operation may be carried out, reference is now made to the enlarged figure, FIG. 9, showing additional details of the cutting and sealing station schematically represented inFIG.-6.
As show in FIG. 9, the cutter 56 is generally in the shape of an inverted box which partially encloses upper die 66. The cutter includes a base portion 70 attached to the motor means 57. Side walls 69 depend from base 70, and a hardened cutting insert 56 is secured in the lower edge of side Wall 69. This insert 56 conforms to the exterior surface of die walls 75 and 76 of the upper and lower dies 66 and 67 and surrounds the upper die. The upper die is suspended within the cutter assembly with the aid of bolts 7l1 which pass through holes 72 in cutter base 70, and threadedly engage the upper die backing members 73. The bolts 71 have heads 74 which hang on the upper surface of the backing member. Springs 55 are 'wound about the bolts between base 70 and the upper die backing member. The function of these springs will become apparent as the description unfolds.
The normal condition of the dies, that is, their condition while the strips 40, 40A and 48 are advancing, is open. The dies normally have sufficient clearance between them to permit the full thickness of the strips or layers 40 (including 40A) and 48 to advance between them without catching. The stroke of the press actually exceeds the aforementioned clearance to the extent necessary to drive the cutter insert 56 at least partially below the surface'of lower die face 51. However, since the springs 55 are interposed between the cutter base and the upper die, and because the cutter insert normally rides above upper die face 50, upper die 66 must come to rest and the springs 55 must be compressed to a significant extent before the cutter insert 56 drops below the lower die face 51.
When the strips 40 and 48 come to rest, the upper die closes down onto the lower die. The size and strength of the springs 55 are sufficiently great to insure that as the press closes, those portions of strips 40 and 48 which are between the die faces 50 and 51 will be substantially and completely crushed therebetween, before the springs 55 yield to any significant extent under the pressure from motor 57. Thus, effective operation of the cutter is prevented until the strips are thoroughly immobilized by being clenched between the die faces. FIG. 9 illustrates that point in the operation of the cutter die assembly when the foam material is collapsed but just before the springs yield.
The condition of the strips 40 and 48 when clenched in the dies is further illustrated in FIG. 10. This figure shows the material from the top with the upper die removed. The aligned edges of strips 40 and 48 are indicated by reference numerals 110 and 111 respectively. First, second and third hatched areas 112, 113 and 114, hatched with inclined lines, and fourth, fifth and sixth hatched areas 115, 116 and 117, hatched with vertical lines, represent the areas of the layers compressed between die faces 50 and 51. Hatched area 112 is the top of a narrow region 64 (FIG. 9) in which the die faces fully collapse the elastomeric foam for coalesing and thermally bonding them with one another. A vertical clearance (e.g. 0.020") is provided between those portions of the die faces above and below hatched areas 115, 116 and 117, so that the dies will not fully collapse the exposed portion of lower layer 48 in these areas. The clearance is provided merely by relieving (making upper die higher and lower die lower) by 0.010" in the indicated areas. Adjacent hatched areas 113 and 114, the die faces are at the same elevation as the adjacent area 112, for the purpose of-helping to keep the relieved portions of the die in parallel-planar relationship.
The collapsing of the layers 40 and 48 in region 64 under area 112, and the transmission of heat to the layers at a controlled temperature for a predetermined time interval (e.g. 500 F. for about /1 second) unites the layers to form the toe portion of a Slipper in the lower blank. The region 64 may be regarded as including two branches 119 and 120 extending away from aligned edges and 111 of the layers on either side of the axis 121 of the lower blank.
In accordance with the present embodiment of the invention, there is only one layer (48) of material under areas 115 and 116 and thus no need to bond anything together. However, where there are to be two lower layers, such as when the sole of the slipper is to comprise for instance a layer of impervious polymeric film as the sole and a layer of elastomeric foam as a cushion insole, it could be desirable to omit the relieving of the die faces in areas so as to unite the edges of the sole and insole. In any event, whether those portions of the die faces corresponding to areas 115 and 116 are relieved or not, they serve to immobilize the adjacent material of the layer or layers to facilitate the cutting operation.
The cutter 56 (FIG. 9), which extends all the way around the upper die, moves downward to sever the material within the die from that outside the die. The line of cutting is indicated by dashed line 122 in FIG. 10. The cutting line extends around the outer edge of the first region 64, passing through both layers 40 and the covered portion of layer 48. The cutting line or lines 122 extend from the ends of the two branches 119 and 120 of region 64 in a direction away from the aligned edges 110 and 111 of layers 40 and 48, thus traversing the lower layer 48 and then extending parallel and adjacent to the opposite edge 123 of the layer 48 and meeting at the "rear 124 of the blank. The cutting is preferably performed outside the region, as shown herein. However, as already indicated, cutting and sealing devices are known, such as those including a cutting wire centered along the face of a sealing die, which cut within the bonded region, and the use of such would not constitute a departure from the spirit of the invention.
Once both the cutting and sealing have been accomplished, the upper die retracts by reversal of motor 57. As the dies open, the strips of thermoplastic material again advance, and the completed slipper blank 63 leaves the press and is separated from the remaining portions of strips 40 and 48 as best illustrated in FIG. 6. These remaining portions constitute the waste products of the present method. It will be noted from FIG. 6 that some waste is left behind in the lower or second strip 48 adjacent the heel end of the blank 63. Some waste should also be left adjacent the toe, so that there is waste adjacent both the toe and heel ends of the blank. This allows the progression mechanism, to be described later, to withdraw the waste evenly from the cutting and sealing operation.
Each time the strips 40 and 48 come to rest, the abovedescribed successive steps of closing the dies, forming a seal, cutting away waste material, opening the dies, further advancing the material, and bringing the material to rest are repeated again and again on a continuous basis.
An optional added feature of the cutter and die assembly depicted in FIG. 9 is a pair of spring mounted plates 77, secured inside dies 66 and 67 respectively with the aid of bolts 78. The bolts 78 threadedly engage the aforesaid plates and pass through holes 79 in the die 66 and 67 and in their respective backing members 73 and 80. Between each of the dies in respective plate members are secured coil springs 87 which are wound about the bolt 78 in which are slightly less compressable than the elastromeric foam material.
When each of the dies are open, each of the plate members 77 protrudes slightly from its die. When the die closes down upon the strips 40, 40A and 48, the spring loaded plates exert pressure on the foam material encircled by the die faces 50 and 51, although not compressing the latter material to the same extent as the material in the region 64. As a consequence of the relatively tight grip on the material and the somewhat indirect and loose contact with the heating elements 52 and 53 and die backing members 73 and 80, the plates 77 do not cause any bonding between the strips of thermoplastic foam material which is between them. Consequently, their sole function when the press is closed is to immobilize the material. In returning to their protruding condition when the die is open, the plates will wrest free the slipper and the waste material in the event that they stick to either of the dies thus facilitating their removal.
In order to practice our method and apparatus of the character described above, it is necessary to utilize some form of automatic mechanism for advancing material through punching, sealing, and cutting stations. Any effective means for engaging the strips and moving them incrementally at the same controlled rate and over the same controlled distance may be used to provide the force for advancing the material. It is desirable that the force be applied directly to the strips both ahead of and beyond the sealing and severing operation. This result can be obtained with the aid of any transport means which acts throughout some portion of the length of the strips, which portion traverses the cutting and sealing operation. Alternately means acting upon the strips at spaced points both ahead of and beyond the cutting and sealing station may be used. For instance, in the present embodiment (FIG. 6), the means acting upon the strips at spaced points both ahead of and beyond the cutting and sealing rollers is a set of rollers. The set includes two pairs of rollers, a first pair 58 and 59 ahead of said station and the second pair 60 and 61 beyond said station. All of the rollers are driven by one common or several synchronous driving means 125, so that each pair acts at the same rate, with the same amount of force and moves the material through the same distance as the other. The rollers 62, 84 and 85 may also be tied into the driving system if desired.
A complete system will also include suitable means for synchronizing the operation of the motor 57 with the work-advancing mechanism. The main objective is to insure that the cutter-sealer mechanism will contact the material only when it is at rest. This objective can be easily obtained through the use of electric rotary switchtype timer clocks or electronic sequence timers, hydraulic pumps, solenoid valves, limit switches and control apparatus with which those skilled in the art are already familiar. Therefore they have merely been indicated schematically in the drawing.
The blank produced in accordance with the procedure depicted in FIGS. 6 through is folded by hand along its longitudinal axis so that the outer ends 91 and 92 of the lower blank are in registration with one another. The folded blank is then moved by hand in the direction of the arrow in FIG. 11 into the cutting and sealing mechanism 90. Guide rods 93, 94 enable the operator of sealing and cutting station 90 to quickly and accurately position the slipper blank within the cutting and sealing station by providing horizontal and vertical registration for the slipper blank.
Cutting and sealing die 95 is formed on die plate 96 and meets in registration with a similarly formed die (not shown) mounted on die plate 97. The two dies are in perfect registry with each other, and provide the contoured shape for the rear of the slipper illustrated in FIG. 12. Guide rods 93 and 94 perform the dual function of guiding the slipper blank into registry with the die surfaces and guiding die plate 96 during its reciprocal motion.
After the operator has inserted the slipper blank into cutting and sealing station 90, hydraulic ram 97 is activated by suitable controls to move die plate 96 laterally on guide rods 93 and 94 into contact and registration with its mating die surface mounted on die plate 97. In doing so, die 95 and the corresponding die on plate 97 crush portions of the slipper blank therebetween. Die plates 96 and 97 are heated by any suitable means such as an electric resistance heater (not shown), and the sealing takes place when the elastomeric material is crushed together in a second region 98 and absorbs sufficient heat from the dies to coalesce and form a bond. This coalescence is ideally carried to the point that for the most part the cellular structure of the material between the die faces is virtually destroyed, leaving behind a pliable, non-cellular seam in region 98 which is illustrated in FIG. 12. Bonding of the strips does not occur to any significant extent outside of region 98 because of the poor heat conductivity of the plastic foam.
Die and its matching die on plate 97 may be formed with cutting edges thereon as illustrated at 99. When die plate 96 advances toward die plate 97, the cutting edge 99, and the adjacent cutting edge mounted on the die of plate 97, meet in registry and the force generated by hydraulic ram 97 severs the material along the trailing edges of the dies while region 98 is being heat sealed. Upon completion of the cutting and sealing operation, which is normally a matter of a few seconds or fractions thereof, the hydraulic ram is retracted by means of a suitable control. Hydraulic ram 97 is powered in and powered out by the application of hydraulic pressure through hydraulic inputs 100 and 101. It should be understood however that a pneumatic ram could be utilized as effectively as a hydraulic ram, and an electric solenoid or other reciprocating motor could also be substituted. It should also be pointed out, that although in the preferred embodiment, both the opening and closing of die plates 96 is under the control of the operator, the operation is preferably made semiautomatic by provision of an automatic return of the die plates to open position after a predetermined time interval, thus causing the sealing station to function with a lesser chance of error in the sealing interval.
Although in the preferred embodiment, die plate 96 is the only moveable part of the dies, it should be understood that a mechanism with floating dye plates or one with a moveable die and a separate moving shearing mechanism, as previously described for the first cutting and sealing station, could be employed. The latter is somewhat more complex but may possibly function more dependably than the combined cutting and sealing die faces 99. Alternately, both die plates 96 and 97 could be advanced to a center position.
The above preferred embodiment illustrated how the invention may readily be practiced with thermal heat sealing apparatus. Our invention may also be practiced with electronic sealing apparatus. These two types of apparatus, although they are both thermal in a sense are distinguishable with regard to the matter of applying the heat to the work. In thermal sealing apparatus, the heat is transferred solely by direct conduction of heat units from a preheated dye directly to the material which the dye contacts under pressure. US Pat. 2,425,388 is an example of this type.
In the so-called electronic type of apparatus, the heat is developed in the material at least in part by subjecting the material to a high frequency alternating field. An example of this type is found in US. Pat. 2,796,913. Electronic apparatus customarily includes auxiliary heating means of the thermal type. In such a case the heat is applied to the material partly by conduction and partly by induction. For example, see US. Pat. 3,026,233.
During the sealing operations of the present method, the foam material is squeezed down by any suitable compression means to a fraction of its uncompressed thickness in the region(s) where the sealing takes place. Any effective means of compressing the material may be used. In the case of thermal sealing equipment, the member that transmits both pressure and heat to the material is ordinarily a metal-faced dye corresponding to the shape of the desired seam. In electronic equipment the members between which the sheets of foam are squeezed often comprise a die which is formed basically of metal that has a facing of fiberglass-reinforced heat resistant polymer backed up by a layer of elastomeric material intermediate the metal and the facing.
The severing or cutting operations may take place while the work is in the grasp of the compression means or after it is released therefrom, the former mode of operation being preferred. The cutting means of both steps may be manual or mechanical, the latter being preferred for reasons of uniformity of operation, Speed and economy. Among the available alternate mechanical shearing means are the ones illustrated above and various shearing dies, cutting dies and cutting wires. Some of the alternate cutting means are illustrated in U.S. Pats. 3,015,601, 3,025,206 and 2,425,388.
From the above description of our methods, it is clear that they are sufliciently versatile to be practiced in a variety of types of equipment, only a few preferred representatives of which have been mentioned. Those skilled in the art will readily adapt this method to types of apparatus not disclosed herein without departing from the steps described herein. The present method has the advantage of producing slippers with a minimum of handling of materials during and prior to production. It can be performed at a great rate of speed with a high degree of product uniformity and few rejects. It is readily adaptable to machinery in which gauged arrangements of sealing mechanisms and severing means are used to turn out a plurality of slippers for each cycle of machine operation.
Having described not only novel articles of manufacture and methods but also apparatus for carrying out said methods, we wish it to be understood that our methods are not restricted to the particular design of slipper disclosed herein, nor is our slipper invention required to be manufactured by the methods of manufacture disclosed herein, except to the extent that such restrictions are clearly expressed in the appended claims. Therefore it should be understood Where a certain step is recited in the appended method claims, reference should not be made to the specification for the purpose of introducing limitations germain to the products or exemplary apparatus disclosed herein and vice versa.
12 What is claimed is:
1. An article of footwear comprising: a sole member of elastomeric sheet material having a toe portion, a heel portion, and marginal edges extending from said toe portion to said heel portion; an upper member attached to said toe portion by seams extending generally horizontally along said upper member and said marginal edges; said marginal edges of said sole member tapering upwardly and inwardly at points progressively further from said toe portion; said upwardly and inwardly tapering portions of said sole member defining the left and right sides of the heel portion of said footwear; said upwardly tapering portions of said sole member being joined together at the heel of said footwear in a generally upright seam which is at least partly forwardly inclined.
2. An article of footwear as claimed in claim 1 wherein said upper member further comprises a second layer of elastomeric sheet material folded upon itself to form a reinforced portion along its rearward edge.
3. An article of footwear as claimed in claim 1 wherein said upper member is attached to said sole member by means of a heat seal.
4. An article of footwear as claimed in claim 1 wherein elastomeric material is an open-celled polyurethane foam produced by blowing a polyester resin with a diisocyanate compound.
References Cited UNITED STATES PATENTS 2,038,844 4/1936 Le Dorf 3610 2,463,296 3/1949 Moore 3610 2,803,894 8/1957 Morgan 36-9 X 2,952,926 9/1960 Laven 36-10 X 2,971,278 2/1961 Scholl 36-9 3,299,540 1/1967 Scholl 368.1 3,426,454 2/1969 Mitchell et a1. 362.5
ALFRED R. GUEST, Primary Examiner U.S. Cl. X.R. 36-10