EP0043369B1 - Shoe sole and method of making the same - Google Patents

Description

The invention relates to a sole for shoes, consisting of at least one essentially rigid rear part and of a flexible front part connected to this rear part approximately in the ball area, at least one of the two parts consisting of plastic. The term "sole" is used to refer to shoe soles with or without an outsole that also form the footbed, but also insoles, insoles and insoles that are only loosely inserted into a shoe.

Known rigid soles have the advantage that they support the foot in an orthopedic manner. Wood is primarily used as the material for rigid soles, here also plywood or pressed wood, but cork, leather fiber materials and plastics can also be used, provided they have the required strength.

A disadvantage of such completely rigid and therefore non-bendable soles is that the stiffness of the soles in the ball area is a hindrance to the rolling movement of the foot when walking and can also be harmful to health under certain circumstances. In order to avoid this disadvantage, soles have already been proposed which consist of an essentially rigid rear part and of a flexible front part connected to this rear part approximately in the ball area (FR-A-2420934). In the known soles of this type, however, it is difficult to establish a permanent connection between the substantially rigid rear part and the flexible front part, since precisely this connection point is subject to permanent bending stresses when using shoes provided with such soles. It has been shown that conventional adhesive connections are not able to cope with these bending stresses and that, therefore, after a certain time the sole at the connection point tends to tear and the shoe provided with such a sole becomes unusable.

The object of the present invention is to avoid this disadvantage and to create a sole in which a permanent connection between the essentially rigid rear part and the flexible front part is ensured. The invention is based on a sole of the type described in the introduction and essentially consists in the fact that one of the two parts, preferably the rear part, consists of a material having a cell structure, the cells of this part mostly being partially open at the connecting surface, and that the other of the two parts, preferably the flexible front part, is formed from a plastic connected to the first-mentioned part by foaming. The fact that one of the two parts has a cell structure with cells that are at least partially open on the connecting surface with the other part ensures that when this other part is foamed during the foaming process, the not yet cured foam material penetrates into the open cells on the connecting surface and solidifies there in such a way that a mechanical connection is established between the two parts, which can withstand even the heaviest loads.

According to a further feature of the invention, the part having the cell structure can consist of a polymer having a cell structure, of wood, optionally of wood arranged in layers, of cork, optionally of cork arranged in layers and / or of combinations of these materials arranged in layers. If this part having the cell structure is formed from polymers and if the foamed part also consists of such polymers, a chemical connection takes place in addition to the mechanical connection between the two parts by the chemical reaction between the polymers. If wood or cork is used for the part having the cell structure and the foamed part is made of polyurethane, as is the case according to a preferred embodiment of the invention, there is also one in addition to the mechanical connection due to the material penetrating the open cells chemical connection instead, since the wood or cork contain OH groups, which chemically bond with the isocyanate groups of the polyurethane. Bending tests on soles according to the invention have shown that the connection between the essentially rigid rear part and the flexible front part also withstands a very large number of bending stresses.

According to a further feature of the invention, the front part can protrude over the rear part on its underside and can be provided with an extension which at least partially extends along the rear part and is foamed on the underside thereof and which is integrally formed with the front part. In such an embodiment, the connection between the front part and the rear part takes place not only along the connecting surface where the front part and the rear part touch each other, but also via the projection which is formed in one piece with the front part and which is foamed on the underside of the rear part, so that the strength this connection is thereby further enlarged. In addition, such an embodiment has the advantage that, according to a further feature of the invention, the protruding area of the front part and the attachment foamed on the rear part can form the outsole, so that the fastening of a separate outsole is not necessary.

According to the invention, the essentially rigid rear part can be provided with fillers, in particular if it consists of a polymer. According to the invention, these fillers can be wooden parts, cork parts and / or leather parts, in particular leather fiber materials, that is, substances that also have a cell structure. The use of such fillers not only saves on polymeric material, but these fillers also stiffen and reinforce the essentially rigid rear part and it is possible to achieve a special appearance of the surface of this rear part with these fillers. However, for example, it is also possible, according to the invention, to form the fillers from very small bubbles, the thin shell of which consists of elastic vinylidene chloride copolymer and / or vinyl chloride copolymer and whose hollow core contains a gas, preferably air. In such a case, it is not necessary to form the essentially rigid rear part from foamed polymers which have a cell structure as a result of the foaming, but instead a cell structure is created by embedding the bubbles in the polymers, so that the same effect is achieved as when using foamed polymers.

It is particularly advantageous if, according to the invention, the essentially rigid rear part consists of rigid polyurethane foamed in a mold. In this case, a predominantly open-cell structure is created, i.e. the cells formed are connected to one another so that the material forming the flexible front part can penetrate deeply into the cells of the essentially rigid rear part and therefore a very firm mechanical connection is achieved. However, the essentially rigid rear part made of foamable and optionally filled with homopolymers, copolymers and copolymers with a hardness of more than 60 Shore D, such as e.g. Polyvinyl chloride or polystyrene exist. Such materials have a predominantly closed-cell structure, i.e. the cells formed are largely not connected to one another, but due to the large number of cells, a good mechanical connection to the flexible front part can also be produced here.

According to a development of the invention, the flexible front part consists of foamed polymers with a hardness of 26 to 98 Shore A, preferably from 45 to 78 Shore A, and with a density of 0.3 to 0.95, preferably from 0.45 to 0 , 78. In such a case, polymers can be used for both the substantially rigid rear part and for the flexible front part, in addition to the mechanical connection which is brought about by the material penetrating into the open cells of one part when the other part is foamed achieve a chemical bond by chemical reaction between the polymers.

If the essentially rigid rear part of the sole is made of wood, which conveys a pleasant walking sensation, whereby the moisture-regulating effect of the wood is added as an additional advantage, while the flexible advantage is made of plastic, this is often perceived as unpleasant because the plastic has these special properties of the Wood does not have. To avoid this disadvantage, according to a further feature of the invention, the top of at least the front part can be provided with a cover, for example made of plywood, cork or leather.

In order to ensure a good connection between the substantially rigid rear part and the flexible front part even when the connection is made only via the connecting surface with which the advantage is directly adjacent to the rear part, this connecting surface of the front part has an indentation according to a further feature of the invention and is preferably concave. This not only increases the connection area compared to a plane connection surface, but also ensures a smooth transition between the essentially rigid rear part and the flexible front part, in particular if, according to a further feature of the invention, the edge areas of the connection surface of the front part are tangential merge into the top and / or bottom of the rear part. At the top of the sole in particular, such a stepless transition is very important for a comfortable fit.

A further improvement in the connection between the essentially rigid rear part and the flexible front part can be achieved by projecting at least one projection in the central region of the connecting surface of the front part, which protrudes into a correspondingly shaped recess in the rear part. Such an embodiment, in which an even firmer connection is achieved, is particularly advantageous in the case of soles which are subject to high stress and which simultaneously form the insole and / or the footbed. The recess expands expediently towards the inside of the rear part and is, for example, dovetail-shaped.

In order to enable a perfect connection between the sole according to the invention and the upper of the shoe also in the area of the front part by nailing or stapling, according to the invention at least one anchoring body, fastening part or the like which runs transversely to the longitudinal direction of the sole and serves to connect the front part to the upper part of the shoe. arranged, which extends at least to the lateral boundary of the front part. Such an anchoring body, fastening part or the like can consist, for example, of a metallic spring pin, but can also be formed from another material, for example from plastic or from wood. It is essential that the anchoring body, fastening part or the like is, on the one hand, well anchored in the flexible front part and, on the other hand, a firm connection of the shoe upper part to the anchoring body, fastening part or the like is made possible, so that a secure connection the upper of the shoe is also guaranteed with the front of the shoe sole.

A separate anchoring body, fastening part or the like can be arranged in the region of each of the two lateral boundaries of the front part, which extends only over a certain region into the interior of the front part. However, it is expedient if an anchoring body, fastening part or the like extending over the entire width of the front part is provided, so that the upper part can be fastened to the two ends of the same anchoring body, fastening part or the like. In such an embodiment, a lateral pulling out of the anchoring body, fastening part or the like from the front part is prevented with certainty.

To connect the anchoring body, fastening part or the like to the upper part, this anchoring body, fastening part or the like can be provided according to the invention with its ends extending to the lateral limitation of the front part with openings which receive pins, nails, clamps penetrating the upper part of the shoe , Bolts or the like. Are determined. For example, screw bolts, possibly those with a self-tapping thread, can be screwed into these openings, thereby ensuring a secure connection of the upper part to the anchoring body, fastening part or the like.

In another embodiment, according to the invention, the anchoring body, fastening part or the like is provided with projections which protrude from the lateral boundaries of the front part and which penetrate the upper part. These approaches can have, for example, a screw thread onto which a screw nut can be screwed. However, it is also possible to design these approaches such that, after the upper part has been arranged, the free end of the projections protruding therefrom is deformed into a rivet head.

In the drawing, the invention is illustrated schematically using exemplary embodiments. 1 shows a sole designed according to the invention in a section in the longitudinal direction of the sole for a women's shoe and FIG. 2 for a clog.

The soles shown in the drawing consist of a substantially rigid rear part 1 and a flexible front part 2 connected to it. In the sole for a women's shoe shown in Fig. 1, the substantially rigid rear part 1 is made of a polymer having a cell structure, e.g. made of foamed hard polyurethane or foamed polyvinyl chloride or polystyrene. The flexible front part 2 is preferably made of polyurethane, which is foamed onto the essentially rigid rear part 1. Fillers can be embedded in the essentially rigid rear part 1, namely either wooden parts, cork parts and / or leather parts, in particular leather fiber materials, which reinforce the essentially rigid rear part 1 and give the surface of this rear part a special appearance. However, it is also possible for tiny bubbles to be embedded in the essentially rigid rear part 1, the thin shell of which consists of elastic finylidene cholide copolymer and / or vinyl chloride copolymer and whose hollow core contains a gas, preferably air. These bubbles also form a cell structure in the rear part 1, which is required for a good mechanical connection of the rear part to the foamed flexible front part 2.

In order to enlarge the connection surface 3 of the front part 2 and thereby improve the connection, in the embodiment according to FIG. 1 the connection surface of the front part 2 is concave and merges tangentially into both the upper side 4 and the lower side 5 of the rear part 1.

In the embodiment shown in FIG. 2, the essentially rigid rear part 1 is made of wood, to which the flexible front part 2, which is made of polyurethane, for example, is foamed. As can be seen from the drawing, the front part 2 protrudes on its underside over the rear part 1 and is formed in one piece with an extension 2 ′ which extends along the rear part 1 and is foamed on the underside 5 of the rear part 1. This not only improves the connection between the front part 2 and rear part 1, but also the outsole is formed at the same time.

The connecting surface of the front part 2 is concave again and merges tangentially into the upper side 4 and the lower side 5 of the essentially rigid rear part 1. In this embodiment, however, a protrusion 6 protrudes in the central region of the connecting surface 3 and engages in a dovetail-shaped recess 7 in the rear part 1, as a result of which the connection between the front part and the rear part is further improved.

As can further be seen from FIG. 1, the flexible front part 2 made of foamed polyurethane has a cover 8 made of plywood, cork or leather in order to improve the wearing comfort. If this cover consists of leather, it can extend to the essentially rigid rear part 1, since the leather can follow the bending processes in the ball area at the junction between the essentially rigid rear part 1 and the flexible front part 2. When using plywood or cork, on the other hand, it is expedient if the cover 8 does not extend to the essentially rigid rear part 1, so that the bending process in the bale area is not hindered. In such a case, an elastic intermediate piece can be inserted between the essentially rigid rear part and the cover.

In the embodiment according to FIG. 2, anchoring bodies, fastening parts or the like 9 are also provided in the flexible front part 2, which extend to the lateral boundary of the front part 2. These anchoring bodies, fastening parts or the like. 9, which serve to firmly connect the upper part of the shoe in the area of the front part 2 to the sole, can be formed, for example, by tension pins which consist of a longitudinally slit metallic tube in which the upper part pins, nails, clamps, screws, especially those with self-tapping threads, etc. that can penetrate the shoe. However, it is also possible to form the anchoring body, fastening elements or the like 9 from a wooden pin in which nails can be driven in or screws can be screwed in, or from a plastic cylinder provided with openings, wherein pins, bolts or the like can also be inserted into the openings are. Finally, the anchoring bodies, fastening elements or the like. 9 can be provided with projections which project beyond the lateral boundaries of the front part 2 and penetrate the upper part of the shoe and are then deformed to form a rivet head. The approaches can also be provided with a screw thread onto which a screw nut is screwed.

In the manufacture of the sole according to the invention, the essentially rigid rear part 1 is first preformed and the preformed part is inserted into a mold. If this essentially rigid rear part 1 is made of wood or cork, pretreatment of the connecting surface is generally not necessary, since these materials have open cells anyway. If, on the other hand, the essentially rigid rear part 1 consists of a polymer having a cell structure, that is to say, for example, of polyvinyl chloride or polystyrene, the cells must be opened on the connecting surface 3 and, if appropriate, also on the underside 5. For this purpose, these surfaces are either roughened mechanically or chemically pretreated with a solvent. A suitable solvent is, for example, when using foamed polyurethane-dimethylformamide and when using foamed polystyrene-toluene. After inserting the substantially rigid rear part 1 into the mold, the anchoring body, fastening parts or the like. 9 and / or the cover 8 are inserted into the mold, whereupon the material forming the flexible front part 2 is filled into the mold and then the mold closed and let this material harden with the mold closed. It is also possible to close the mold after inserting the essentially rigid rear part 1 and, if appropriate, the anchoring body, fastening parts or the like and / or the cover and then the material forming the flexible front part 2 through an opening in the mold, if necessary under pressure to inject.

After the sole has been shaped, at least the surface facing the sole of the foot, preferably also the side surfaces of the sole, is processed, for example by grinding or milling.

Although it has always been assumed in the preceding description that the essentially rigid rear part 1 is first preformed and that the flexible part 2 is foamed onto this part, a reverse procedure is also possible in principle, in which the flexible front part 2 is first produced, this front part 2 can already be provided with the anchoring bodies, fastening parts or the like. 9 and / or with the cover 8, that after roughening the connecting surface 3 to the rear part 1, this front part 2 is inserted into a mold and that, for example, made of hard - Polyurethane existing rear part is foamed onto this front part. In this case, too, there is a firm and permanent connection between the front part and the rear part.

Claims (25)

1. Sole for shoes, consisting of at least one substantially rigid rear portion (1) and of a flexible front portion (2) connected with said rear portion (1) approximately at the area of the ball by molding, at least one of the two portions (1, 2) cosist- ing of a synthetic plastics material, characterized in that one of the two portions, preferably the rear portion, consists of a material having a cell structure, the cells of this portion being at least partially opened at the connecting surface (3) and that the other of the two portions, preferably the flexible front portion (2) is formed of a synthetic plastics material connected with said first portion by foaming thereto.

2. Sole as claimed in claim 1, characterized in that the portion having a cell structure consists of apolymer having a cell structure, of wood, if desired, of wood arranged in layers, of cork, if desired, of cork arranged in layers, and/or of combinations of these materials arranged in layers.

3. Sole as claimed in claim 1, characterized in that the portion foamed onto the other portion consists of polyurethane.

4. Sole as claimed in claim 1, 2 or 3 characterized in that the front portion (2) extends on its bottom side over the rear portion (1) and is provided with an extension (2') being integral with the front portion (2), which extension (2') extends at least partially along the rear portion (1) and is foamed onto the bottom side (5) thereof.

5. Sole as claimed in any one of claims 1 to 4, characterized in that the protruding area of the front portion (2) and the extension (2') foamed onto the rear portion (1) form the running sole.

6. Sole as claimed in claim 1, characterized in that the substantially rigid rear portion (1) is provided with filling materials.

7. Sole as claimed in claims 1 and 6, characterized in that the filling materials are wood particles, cork particles and/or leather particles, particularly leather fibre materials.

8. Sole as claimed in claims 1 and 6, characterized in that the filling materials are formed of minute bubbles, the thin shell of which cosists of an elastic vinylidene chloride copolymer and/or vinyl chloride copolymer and the hollow core of which contains a gas, prefembly air.

9. Sole as claimed in any one of claims 1 to 8, characterized in that the substantially rigid rear portion (1) consists of hard polyurethane foamed within a mold.

10. Sole as claimed in any one of claims 1 to 8, characterized in that the substantially rigid rear portion (1) consists of foamable homopolymers, copolymers and mixed polymers, for example polyvinyl chloride or polystyrene, if desired provided with filling materials, said polymers having a hardness of more than 60 Shore D.

11. Sole as claimed in any one of claims 1 to 10, characterized in that the flexible front portion (2) consists of polymers foamed onto the other portion and having a hardness of 26 to 98 Shore A, preferably 45 to 78 Shore A, and a density of 0.3 to 0.95, preferably 0.45 to 0.78.

12. Sole as claimed in any one of claims 1 to 11, characterized in that the top side of at least the front portion (2) is provided with a top layer, for example consisting of laminated wood, cork or leather.

13. Sole as claimed in anyone of claims 1 to 12, characterized in that the connecting surface (3) of the front portion (2), by means of which said front portion is connected to the rear portion (1), comprises a groove, preferably this connecting surface is concave in shape.

14. Sole as claimed in claim 13, characterized in that the marginal areas of the connecting surface (3) of the front portion (2) tangentially pass over into the top side (4) and/or into the bottom side (5) of the rear portion (1).

15. Sole as claimed in claims 13 and 14, characterized in that at the center area of the connecting surface (3) of the front portion (2) there protrudes at least one protrusion (6) engaging a correspondingly shaped recess (7) of the rear portion (1).

16. Sole as claimed in claim 15, characterized in that the recess (7) enlarges in direction towards the interior of the rear portion (1), for example the recess having a dove-tail shape.

17. Sole as claimed in any one of claims 1 to 16, characterized in that at least one anchoring member, fastening portion or the like (9) is provided within the front portion (2), which member extends transversely relative to the longitudinal direction of the sole and serves for the purpose of connecting the front portion (2) to the upper of the shoe and extends at least up to the lateral border of the front portion (2).

18. Sole as claimed in claim 17, characterized in that an anchoring member, fastening portion or the like (9) is provided which extends over the whole width of the front portion (2).

19. Sole as claimed in claim 17 or 18, characterized in that the anchoring member, fastening portion or the like (9) is provided with openings at its ends extending up to the lateral border of the front portion (2), said openings being adapted to accomodate pins, nails, clamps, bolts or the like extending through the upper.

20. Sole as claimed in claim 17 or 18, characterized in that the anchoring member, fastening portion or the like (9) is provided with extensions protruding from the lateral borders of the front portion (2) and extending through the upper.

21. Process for producing a sole as claimed in any one of claims 1 to 20, characterized in that the portion comprising the partially open celi structure at the connecting surface (3), preferably the substantially rigid rear portion (1), and, if desired, the anchoring members, fastening portions or the like and/or the top layer, are put into a mold, synthetic plastics material, preferably polyurethane forming material, is poured or injected, if desired under pressure, into the remaining free space of the mold for forming the other portion, preferably the flexible front portion (2), said synthetic plastics material is allowed to cure, keeping the mold closed, and that, if desired, after having removed the sole from the mold, at least the surface facing the sole of the foot, preferably also the lateral surfaces of the sole are worked, preferably by a grinding or milling operation.

22. Process as claimed in claim 21, characterized in that the cells of the portion having a cell structure, prior to placing this portion into the mold, are opened at the connecting surface (3) with the other portion.

23. Process as claimed in claim 21 or 22, characterized in that for the purpose of opening the cells the connecting surface (3) of the portion having a cell structure is mechanically roughened.

24. Process as claimed in claims 21 and 22, characterized in that for the purpose of opening the cells the connecting surface (3) of the portion having a cell structure is chemically pretreated with a solvent, for example dimethylformamide for portions consisting of foamed polyurethane, or toluene for portions consisting of foamed polystyrene.

25. Process as claimed in claim 21, characterized in that the synthetic plastics material, preferably the polyurethane forming material, is filled into the mold prior to closing the mold.

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