GB2183536A - Moulding plastics foam footwear sole - Google Patents

Abstract

A footwear sole (3) incorporates a flexible prefabricated cushion piece (6) adhesively attached to the ball portion of the sole. The cushion piece has apertures (7) which attach it to pegs (5) on an upper mould portion (1). After introduction of foam into the mould, opening of the latter detaches the cushion piece (6) from the mould portion (1), leaving the cushion piece (6) embedded in the sole. <IMAGE>

Description

SPECIFICATION Plastics foam footwear sole Footwear soles consisting ofpolyurethanefoamsys- tems are becoming constantly more widespread owing to their good durability and lowweight. In order that footwear retains at least to a large extent its original shape even after many years of wear, the foam systems in known polyurethane soles are adjusted sothatthey are relatively hard in order, asfaras possible, to avoid long-term deformations of the sole and also to achieve the highest possible scuff resist ance.With the relatively hard adjustment ofthe foam systems, however, the comfort in wear of the footwear necessarily suffers, especially in the area of the balls ofthefeet because atthat pointthewalking sole is designed so that it is relatively thin.

The object of the invention is to provide a footwear sole consisting of a plastics, preferably polyurethane, foam system that has an increased comfort in wear and is suitable especially for comfort shoes and for health shoes. The invention also provides a method of making such a shoe sole.

According to the invention, this problem is solved byadhesivelyfoaming into the sole material in the ball portion of the shoe sole a flexible cushion piece of large surface area that has at its free upperface elements for detachable fastening to a mould tool priortothe moulding ofthe sole by the use of said tool.

In comparison with customary, so-called cushion soles in which a flexible foam cushion is manually inserted into a recess in the ball region ofthe sole, the sole according to the invention has the advan tageofsubstantiallysimplified manufacture and reli ablefixing ofthecushion pieceoflargesurfacearea with the sole. In such soles consisting of polyurethane foam systems, it is importantforthe manufacturing process to be as simple and cost-effective as possible sincethe possible uses of such soles for different types offootwear depend to a constantly in- creasing extent on the price of the sole. The cushion pieces or inserts used according to the invention are designed in the shape of half-soles and consist of a soft high-expansion foam.

To manufacture a sole by the method ofthe invention, the prefabricated cushion piece is accurately positioned, before the sole mould is closed, on a mould tool and preferably the uppertoolthereof which is intheform of a cover, the cushion piece being adequatelyfirmly attached to this upper tool with the aid ofthefastening elements. Afterthe closed mould has been filled with the liquid polyurethane system,the rising foam surroundsthe cushion piece so firmly that when the mould isop- ened the cushion piece detaches itself from the upper tool thereof and remainsinthesolewhich thus formes a so-called composite moulding.

A preferred possibility for the accurate positioning of the cushion insert within the sole is distinguished bythefactthatthefastening elements are designed in the form of holes which extend completely, or only partially, transversely through the cushion piece.

There are provided on the lower face of the upper tool pegs in an arrangement and numbercor- responding to the holes, onto which pegs the cushion piece is pushed with its holes. The dimensions of the holes in the cushion piece and ofthe pegs are so adapted to one another as to achieve a fit that is sufficiently firm for positioning the cushion piece during the movements of the upper tool and thefoaming operation; atthe same time, it is ensu- red, however, that when the mould is opened after hardening of the sole, the cushion piece is nottorn out ofthe composite sole by the upper mould nor damaged in any other manner.

In an especially advantageous design ofthefootwear sole, the ball-cushion insert has the shape of a half-sole having an approximately flat lower face from which an edge portion inclined inwardly atan acute angle rises and passes via a distinctive edge intotheupperfaceofthecushion piece,theupper face being curved according to the shape of the foot or flat. In this upperface, slightly spaced from the transition edge, the holes are arranged in the form of a ring and extend to the lowerface ofthe cushion insert orterminate shortly before it.The inwardly inclined edge face is covered during the foaming operation by the formation of an edge lip of sole material, which results not only in the advantage of an improved fixing of position of the cushion insert in the sole material, but also in improved confort in wear, because the deformations of the sole underthe vertical pressure loads occurring during wear in these edge zones of the cushion piece altergradually, and not abruptly. The distinctive edge between the in clined edge faces and the upperface ofthe cushion piece brings about a close fit of the cushion piece against the uppertool and prevents the penetration of sole material between the upper face ofthe cushion pieceandthe uppertool.

Exemplary embodiments ofthe shoe sole according to the invention are explained in detail below with reference to the drawings.

Figure 1 shows, in longitudinal section, a finished sole immediately after manufacture, the mould tools being open; Figure2 shows, in cross-section,two cushion piece portions of different height; Figure 3 shows a plan view of the cushion piece portions according to Figure 2; and Figure4shows, in cross-section, a different cushion piece foamed into a walking sole.

Figure 1 shows a sole mouldforfoaming a polyurethane shoe sole, which mould comprises an uppertool and a lowertool 2. To manufacture a shoe sole 3, shown in longitudinal section between the two open moulds 1 and 2, the two mould tools 1 and 2 are closed by a relative movement and the liquid foam system is introduced via supply channels (not shown) into the mould space in which, by the known reactions of its components, it foams up until the entire mould space is completely filled. On the lower face of the uppertool 1 there are secured in the rear region pegs or profiles 4 in the shape of truncated cones and in the front ball regionthere are secured pegs 5.When the uppertool is open priorto the moulding operation, there is pushed onto these pegs 5 a prefabricated cushion piece 6 shown in Figures 2 and 3 and consisting ofa high-expansion foam, as is shown in Figure 1 by a dot-dash line. Forthis purpose, there are provided in the cushion piece a plura litvofholes7 in an arrangement corresponding to the pegs,the diameter of which holes is app roximately 30% smallerthan the diameter of the pegs 5. When the cushion piece is pushed on,the pegs 5 enter the holes 7 in the cushion piece 6 and hole the latter, owing to the differences in diameter, with a clamping fit securely but detachably to the uppertool.The lower tool 2 has an upper recess 8for accommodating the uppertool 1 and adjoining this recess a space 9 which extends downwards and, when the tools 1 and 2 are closed,formsthe mould space for the formation ofthe shoe sole.

The shoe sole 3 shown in longitudinal section in Figure 1 consists of a polyurethanefoam system,the hardness and inherent stability of which are adjusted according to the particular shoe type. In the rear portion ofthe sole there are distinctive recesses 10, the shape of which corresponds to that of the lugs 4 on the upper tool and which define stud-like elevations 11 of polyurethane material. The distinctive recesses l0can,accordingtoonedesign oftheshoesole shown in Figure 1, be filled also with flexible highexpansion foam inserts of corresponding shape which can be connected to one another by intermediate pieces (not shown) and thus form an en tirelyintegral component.This componentcan, sim ilarly to the ball-cushion piece, also be detachably fastened to the, in that case flat, lowerface ofthe uppertool by means of pegs 5 so that during the foaming process a permanent, rigid connection is achieved between these inserts and the sole material.

The ball-cushion pieces have advantageouslythe shape shown in Figures 2 to 4which is adapted approximatelyto the shape ofthe front portion ofthe sole. Accordingly to Figure 2, the cushion piece has flatupperandlowerfacesl2and l3andinwardly inclined edgefaces 14. In the higher embodiment of the cushion piece shown in the righthand side of Figures 2 and 3, there is a widened inclined edge face 14 which, in its lower portion, passes into a perpendicular edge 15. This inclined edge face 14 of the cushion piece 6 forms the fastening edge X1 or X2 of the sole.Between the inclined edge face 14 and the fiat upperface 12 ofthe cushion piece 6 there is a distinctive transition edge 16 which prevents the polyurethane sole material from pebetrating into the intermediate space between the upper face ofthe cushion piece and the lowerface ofthe uppertool 1 during the foaming operation. In the region ofthe fastening edge X1; X2, which in the finished sole is covered at the top by a correspondingly projecting lip-shaped lug 17 (see Figures 1 and 2), there is a pressure resistance in the vertical direction that diminishes continuouslyfrom the outer edge of the sole to the inner ball region, by means of which the comfort in wear of a shoe provided with the shoe sole according to the invention is increased and pressure points are avoided.By altering the inclination ofthe edge face 1 4the width of the fastening edge X can be ntiuenced and adapted to the requirements ofthe particulartype of shoe.

As is clearespeciallyfrom Figures 2 to 4, the holes 7 in the cushion piece 6 are arranged in the form of a ring slightly spaced from the upper edge 16, their diameter being approximately 30% smallerthan that ofthe pegs 5 secured in the uppertool 1. When the cushion piece is pushed onto these pegs, there is therefore a clamping fit which ensures a sufficiently accurate and reliable positioning and fixing ofthe cushion piece, atthe same time the upperface 12 of the cushion piece 6 being heldtightlyagainstthe lowerface of the uppertool in orderto preventthe penetration of polyurethane material between these two surface during the foaming process.As is clear from Figure 3, in addition to the outer holes arranged in the form of a ring it may be advantageous to provide holes also in the central portion ofthe cushion piece and to provide corresponding pegs 5 in the uppertool. These holes 7 can either be manufactured by punching and are then through holes orthey are formed during the manufacture ofthe cushion piece by pegs attached to the cushion mould, in this case it being possible forthe holes to be blind bores. In the case of through holes there is an additional fixing of the cushion element by polyurethane material that penetrates into these holes from below during the foaming operation andfillsthem.

In the embodiment according to Figure 4the heig ht or thickness of the wal I of the cushion piece 6 on the external ball side 18 is clearlysmallerthan that on the internal ball side 19. When foaming this cushion piece 6 into the walking sole, this results in a lowerwalking zone layer 20thatis inclined from the outside atthetoptothe inside atthe bottom, asa result of which the natural rolling movementofthe wearer's foot is conveyed from the ball ofthesmall toe to the ball ofthe largetoe.

As shown, the cushion insert preferably extends overthe entire load-bearing sole width in the ball region, it being possibleforthe lower portion, projecting as a result ofthe inclined edge faces 14, ofthe cushion piece 6to extend underthe internal edge of the sole edge 21, as shown in Figures 1 and 4.

Claims (12)

1. A footwear sole of plastics foam, including a flexible cushion piece of large surface area adhesivelyfoamed into the sole material in the ball portion of the shoe sole,the free upperface of thecushion piece having elements for detachable fastening to a mould tool priorto a sole moulding operation employing said tool.

2. AsoleaccordingtoClaim1,whereinsaidel- ements ofthe cushion piece are holes.

3. Asole according to Claim 1 or Claim 2,wherein the cushion piece has upwardly and inwardly inclined edgefaceswhich are covered atthe top by lipshaped lugs of the sole material, and the holes are arranged in the form of a ring with slight horizontal spacing from the distinctive transition edge of the in clined edgefacesto the upperface of the cushion piece

4. A sole according to any one of Claims 1 to 3, wherein the cushion piece is of graduallyvarying height.

5. Asole according to any one of Claims 1 to4, whereinthefrontedge portion ofthecushion piece projecting downwards extends to or just before the edge of the sole.

6. A sole according to any one of Claims 1 to 5, wherein there are provided at least in the heel portion behind the cushion insert, distinctive recesses and stud-like elevations.

7. A sole according to Claim 6, wherein further flexible cushion pieces are secured in the recesses.

8. A sole according to any one ofthe preceding claimswhereinthecushion piece is inthe app- ropriate shape of a half sole.

9. A according to any one ofthe preceding claims wherein said plastics foam is polyurethane.

10. A footwear sole of plastics foam, substantially as hereinbefore described with reference to Figures 1 to 3 or Figure 1 to 3 as modified by Figure 4 of the accompanying drawings.

11. A method of making a footwear sole of plastics foam according to any one ofthe preceding claims, comprising releasably attaching to a mould tool a prefabricated cushion piece, closing the mould form a moulding cavitycontaining the cushion piece, introducing liquid plastics foam into the cavity so as to at least partially surround the cushion piece, and opening the mould to detach the cushion piece from said tool and thereby leave the cushion piece to form acomposite mouldingwiththeremainderof the sole.

12. A method of making a footwear sole of plastics foam substantially as hereinbefore described.