METHOD OF MANUFACTURING MOULDS FOR THE SOLES OF FOOTWEAR AND A MOULD PRODUCED BY THIS METHOD

Abstract: A method of manufacturing a mould part having the shape of a sole of an article of footwear, wherein a metallic slab (2) is made in the generally desired shape, the slab (2) is assembled with other mould parts (8, 9) to define a mould cavity surrounding the slab (2), and an elastomer is introduced into the cavity to cover the peripheral face of the slab (2), the arrangement being such that the elastomer becomes secured to the slab (2) but not to the other mould parts (8, 9), to form a seal round the peripheral face. Thus the surfaces of the slab (2) destined to receive the sealing joint may be sanded and lubricated with the aid of a solvent and a polyurethane based primer may be applied to these surfaces to increase the adhesion of the seal on the slab, and a mould release agent may be applied to the internal surfaces of the shells of the mould.

Description: TITLE: MANUFACTURE OF MOUI,DSS FOR T1{E SOLES OF FOOTWEAR The invention relates to the manufacture of moulds for the soles of footwear. It is known to manufacture metallic moulds for the soles of footwear. I In the traditional production methods it is necessary to machine the mould parts in order that they fit together closely. Such production processes require a considerable amount of time and skill during the machining operations as it is essential that when the machined block defining the mould top is assembled with the parts defining the mould sides, the contour of the parts correspond exactly to avoid gaps which would result in so called "flashing" during the pouring or injection of the material serving to constitute the sole. It is however almost impossible to obtain a perfect register between the various mould parts by traditional means, with the result that the moulded footwear will require subsequent treatment to remove the flashing. It is an object of the invention to mitigate against or remove the shortcomings of the known arrangement. It is also an object of the invention to provide a mould for the production of soles for footwear articles which is simple and quick to produce. To this end, the invention relates to a method of manufacturing a mould part, wherein a slab is made in the generally desired shape, the slab is assembled with other mould parts to define a mould cavity surrounding the slab, and an elastomer is introduced into the cavity to cover the peripheral face of the slab the arrangement being such that the elastomer becomes secured to the slab but not to the other mould parts, to form a seal round the peripheral face. This process makes it possible to reduce the machining operations on the mould parts while still obtaining good sealing between the mould parts during pouring or injection to form the sole, it being possible for the moulding to be carried out in two or more successive operations using distinct materials and/or different colour materials. According to another feature of the invention, during the production of the slab, which is preferably of metal, lateral centering bosses and an end boss on the periphery are made to locate the slab in the mould. According to a further feature of the invention, the lateral centering bosses are removed after formation of the peripheral seal to increase the elasticity of the sealing joint. The invention also relates to a mould part for soles of footwear. articles made by the method described above, comprising a metallic slab provided on its outer surface with a coating of an elastomer material such as polyurethane forming a sealing joint. In accordance with another feature of the invention, the sealing joint preferably extends over the whole height of the peripheral surface of the metallic slab. The invention is diaGramtnatically illustrated, by way of example, in the accompanying drawings, in which: Figure 1 is a perspective view of a rough metallic slab which forms a first mould part; Figure 2 is an inverted perspective view of the metallic slab of Figure 1 assembled with other mould parts; Figure 3 is a perspective view of the first mould part in the finished state. According to Figure 1, a first mould part 1 generally in the shape of a sole of an article of footwear is constituted by a metallic slab 2, e.g of aluminium. The upper face 3 of the slab 2 is hollow and is arranged for the reception of the material to form the sole of the article of footwear. The hollow is defined by a peripheral lip 4 round the slab. The slab 2 also incorporates lateral centering bosses 5 and an end boss 6 which together allow the slab to be located in the mould. As shown in Figure 2, the slab 2 is inverted and is assembled with other mould parts formed by two shell components S and 9 to form a mould 7. The location of the slab 2 relative to the mould parts S and 9 is effected with the aid of the lateral bosses 5 and of the end boss 6. The two shell components 8 and 9 when assembled and locked together present a joint plane 10. The mould 7 is provided with a duct 11 for the injection or introduction of an elastomer material such as polyurethane into the mould cavity According to Figure 3, the mould part 1 is shown in the finished state, in which it is provided over the full width of its external peripheral surface with a coating 12 of elastomer, which forms a sealing joint when the mould part is assembled with the other mould parts in the production of footwear. The end boss 6 is retained, while the lateral centering bosses 5 have been removed in order to increase the elasticity of the sealing joint 12. The sealing joint 12 may be of polyurethane. The end boss 6 is retained to allow the slab 2 to maintain a fixed position in the endwise direction, since the injection duct is located in one end to ensure good sealing. In order to make the mould part 1 for a sole of an article of footwear shown in the Figures 1 to 3, a metal slab is first made in the form of the sole desired, the slab 2 is assembled with two shell components 8 and 9 to form a mould 7; an elastomer such as polyurethane is poured or injected into the mould cavity to cover the external peripheral surfaces of the slab 2 with a coating of polyurethane, this latter constituting the sealing joint 12 of the slab 2. During the manufacture of the slab as it is shown in Figure 1, lateral bosses 5 and an end boss 6 are formed to allow subsequently the location and the fitting of the slab 2 in the mould 7 (Figure 2), and when the slab 2 has been positioned, a sanding operation and a lubricating operation are carried out with the aid of a solvent on the external surfaces of the slab destined to receive the sealing joint 12. A polyurethane based primer is then applied to this external surface to increase the adhesion of the sealing joint 12 on the metal. A mould releasing agent is applied to the internal surfaces of the shell components 8 and 9 of the mould 7 in order to eliminate any adhesion of the polyurethane to those parts of the mould during the pouring or injection A thin film of a material such as polyethylene is placed between the joint planes 10 of the shell components 8 and 9 to improve the sealing of the shell components. This thin film has a thickness of from s/100 to 1/10 mm. Polyurethane is poured or injected into the mould 7. This material fills the spaces available between the metallic slab 2 and the internal faces of the mould 7. The exothermic reaction of the polymrethane will reactivate the film of primer so that the polyurethane becomes attached to the slab. When the cross-linking of the polyurethane is completed, the mould part 1 is extracted from the mould 7 and the lateral bosses 5 are removed therefrom in order to improve the elasticity of the sealing joint 12. The sealing joint 12, which is preferably made in a polyurethane having high mechanical and physical properties, is by way of an example from 3.5 mm to 10 ram thick. Its hardness can vary between 600 and 900 Shore. As shown in Figure 3, the mould part 1 is ready for use in a mould for the production of soles for articles of footwear.

Claims: CLAIN5S 1. A method of manufacturing a mould part, wherein a slab is made in the generally desired shaped, the slab is assembled with other mould parts to define a mould cavity surrounding the slab, and an elastomer is introduced into the cavity to cover the peripheral face of the slab, the arrangement being such that the elastomer becomes secured to the slab but not to the other mould parts, to form a seal round the peripheral face. 2. A method as claimed in claim 1, wherein during the manufacture of'the slab lateral centering bosses and an end boss are formed on its periphery to locate the slab in the mould. 3. A method as claimed in claim 2, wherein the lateral centering bosses are removed after formation of the peripheral seal to increase the elasticity of the sealing joint. 4. A method as claimed in any preceding claim, wherein after the fitting of the slab into the mould the surfaces of the slab destined to receive the sealing joint are sanded and lubricated with the aid of a solvent and then a polyurethane based primer is applied to these surfaces to increase the adhesion of the joint on the slab. 5. A method as claimed in any preceding claim wherein a mould release agent is applied to the internal surfaces of the shells of the mould. 6. A method as claimed in any preceding claim wherein a thin film of a material such as polyethylene is placed between the joint planes of the shell components to improve the closing of these shells. 7. A method of manufacturing a mould part, substantially as hereinbefore described. 8. A mould part for soles of footwear articles made by the method of any preceding claim comprising a metallic slab provided on its periphery with a coating of an elastomer material such as polyurethane forming a sealing joint. 9. A mould part as claimed in claim 8, wherein the metallic slab is provided on its periphery with lateral centering bosses and an end centering boss. 10. A mould part as claimed in claim 8 or claim 9, comprising on one of its faces a hollow part forming a location for the reception of the material constituting the sole of the article of footwear, the edges presenting the desired form of that sole. 11. A mould part as claimed in any one of claims 8 to 10, wherein the sealing joint extends over the whole height of the peripheral face of the metallic slab. 12. A mould part for soles of footwear articles substantially as hereinbefore described with reference to, and as illustrated in, the accompanying drawings.

Inventors: ADAM, JEAN-CLAUDE
Applicants: THE BRITISH BATA SHOE COMPANY LIMITED
Application year: 1980
Main classification: B29C1
IPC codes: B29C33, B29C39, B29C70, B29C45, B29D35