FOOTWEAR REINFORCEMENT

Abstract: An article of footwear comprises an upper, a flexible metal midsole and outsole. Between the flexible metal midsole and the outsole is located an internal arch-reinforcement member or "digging-plate". The "digging-plate" may be made of a rigid plastics material, suitably a fibre-reinforced plastics material.

Description: This invention relates to articles of footwear having an internal arch reinforcement and to a method for their manufacture. Although the present invention will be described herein with particular reference to a reinforced moulded boot, it is not to be construed as being limited thereto. The incorporation of stiffening or reinforcement elements in footwear to strengthen portions of the footwear structure is known. For instance: U.S. Patent Specification 3 442 032 discloses shoes having a stiffener of undirectional fibres embedded in thermoplastic resin, for example a shank stiffener in the insole or between the insole and the outsole; G.B. Patent Application Publication 2 061 172A discloses high-heeled synthetic resin footwear having an arcuate arch-and-heel stiffener of ferrous metal embedded in injection-moulded sole and heel portions; and U.S. Patent Specification 4 255 825 discloses injectionmoulded plastic footwear, especially high-heeled shoes, having a rigid arch-and-heel reinforcement of plastic or metal. Such footwear constructions generally are for normal wear and do not have the strength desired for work- or safety-boots. Work- and safety-boots having a metal midsole in an injection-moulded sole are known, for instance from DE Offenlegungsschrift 2 823 099. However, it is found that such boots lack desirable resistance when used for digging operations which exert a high localised force on the arch region. When boots are worn for use in digging operations, the spade or other implement tends to cut or abrade the arch region of the outsole of the boot. Outsoles of rubber are cut-resistant to some extent, but outsoles of pvc (the preferred material for bulk manufacture of boots) are relatively quickly damaged by repeated digging operations. It is known to provide such boots with an external, "tie-on", metal plate to reinforce the arch region of the outsole. Such plates, known as "digging plates", are expensive and cumbersome and tend to be inefficient. It is also known, in the case of boots with hand-made rubber outsoles, to incorporate an arch reinforcement member on the outside of the boot. However, in the case of pvc boots, such an external reinforcement, being of a harder material than that of the outsole, would tend to "break away" on flexing of the sole when the boot is in use. We have found that reinforcement of the arch region of the outsole can be achieved, according to the present invention, by providing an internal "digging-plate" of a rigid plastics material. Accordingly, the present invention provides an article of footwear comprising an upper, a flexible metal midsole and an outsole, in which an arch reinforcement member in the form of a plate of rigid plastics material is located between the metal midsole and the outsole. The present invention further provides a method for the manufacture of an article of footwear of the type described in the immediately-preceding paragraph, the method comprising the following stages: (i) placing the metal midsole in an injection mould and closing the mould by means of a sole closure plate; (ii) injecting material into the mould to form the upper and to secure the midsole to the upper; and (iii) replacing the sole closure plate with an outsole moulding plate and injecting material into the mould to form the outsole; the method being characterised in that the arch reinforcement member is attached to the metal midsole before stage (i). The arch reinforcement member preferably is a plate of a fibre-reinforced plastics material. Examples of such materials include fibre-reinforced polycarbonates and polypropylenes. The particularly preferred reinforcing fibres are glass fibres. In the moulding process according to the present invention, the sole closure plate may be shaped so as to accommodate the arch reinforcement member. By attachment of the arch reinforcement member to the midsole prior to placing the midsole assembly in the mould, movement of the arch reinforcement member during the moulding process is avoided. Such attachment may be achieved by means of a suitable adhesive. In the finished boot, the arch reinforcement member can constitute part of the thickness of the outsole. Alternatively, the outsole can be modified so as to have its normal thickness in addition to the thickness of the arch reinforcement, for example, to comply with British Standard Specifications 1870 part 3 and 6159 part 1 (which relate to safety footwear). The preferred material for the arch reinforcement member (a glass fibre-reinforced polycarbonate) meets the nail penetration test requirements specified in British Standard Specification 1870 Part 3. If required, footwear according to the present invention can include a toe reinforcement, known per se.

Claims: An article of footwear comprising an upper, a flexible metal midsole and an outsole, characterised in that an arch reinforcement member in the form of a plate of rigid plastics material is located between the metal midsole and the outsole. An article according to Claim 1 characterised in that the arch reinforcement member is a rigid plate made of a plastics material reinforced with fibres (e.g. glass fibres). An article according to Claim 1 or 2, characterised in that the plastics material is polycarbonate or polypropylene. An article according to Claim 1, 2 or 3, characterised in that the article is a reinforced moulded boot. An article according to any of the preceding Claims, characterised in that the reinforcement member provides an internal digging plate for reinforcement of the arch region when used in a digging operation. Method of making an article of footwear as defined in any of the preceding Claims, which comprises the stages of: (i) placing the metal midsole in an injection mould and closing the mould by means of a sole closure plate; (ii) injecting material into the mould to form the upper and to secure the midsole to the upper; and (iii) replacing the sole closure plate with an outsole moulding plate and injecting material into the mould to form the outsole, characterised in that the arch reinforcement member is attached to the metal midsole before stage (i). A method according to Claim 6, characterised in that the sole closure plate is shaped so as to accommodate the arch reinforcement member. A method according to Claim 6 or 7, characterised in that the arch reinforcement member is attached to the midsole by means of an adhesive.

Inventors: HARRINGTON, ROBERT
Applicants: DUNLOP LIMITED
Application year: 1988
Main classification: A43B13
IPC codes: A43B7, B29D35