The present invention relates to footwear such as shoes.

Some shoe designs have a cavity between the outer sole and the shoe upper which normally contains a piece of synthetic material placed in the cavity during manufacture of the shoe. Whilst providing some cushioning for the wearer, the synthetic piece does not always effectively extend throughout the outer sole such as into the heel portion of the shoe and since it is a discrete piece of material it is not possible to vary the cushioning effect in a range of shoes.

The present invention seeks to provide an improved item of footwear and a method of manufacturing such an item of footwear.

The present invention provides an item of footwear such as a shoe comprising an outer sole and an upper having an insole, and at least one cavity between the outer sole and insole having inserted therein by injection a resilient material which provides cushioning between the outer sole and insole.

The invention also provides a method of manufacture of footwear such as a shoe comprising the assembly of securing an outer sole to an upper to provide at least one empty cavity between said outer sole and an insole of said upper, and subsequent to said assembly, injecting into said at least one cavity a resilient material to provide cushioning between the outer sole and the insole.

In a preferred form of the invention the material is a synthetic material, preferably a plastics foam.

The present invention is further described hereinafter, by way of example, with reference to the accompanying drawings which are each a longitudinal section through a preferred form of shoe according to the present invention.

Referring to the drawings, there is shown a shoe 10 having a shoe upper 12 of leather or synthetic material secured to a multi-layered sole and heel unit 14. The assembly has an outer sole 16 and

a heel 15 of resilient, lightweight synthetic material, an intermediate layer or mid sole 17 which may or may not be integral w h the outer sole 16 and heel 15, and an insole 20. In the illustrated embodiments the intermediate layer 17 has a cavity 18 extending the full length of the shoe from the toe portion to the heel portion between the outer sole 16 (or mid sole 17) and the insole 20. Normally, during manufacture of the shoe a discrete piece or pieces of a resilient material such as a synthetic foam would be inserted into the cavity in order to provide some cushioning effect for the user. However, in the preferred process according to the present invention, during manufacture of the shoe the cavity 18 is left empty. Then, once assembly of the shoe has been completed, ie after the outer sole 16 and heel unit 15 is attached to the upper 12, a synthetic foam material 19 is subsequently injected under pressure into the cavity 18 to fill the whole of the cavity from the toe portion to the heel portion of the shoe. The synthetic material is conveniently injected through a small bore 22 which extends through the outer sole 16. Air which is trapped in the cavity 18 is allowed to escape through breather holes 24 and 26 to enable the synthetic material to fully and intimately fill the whole of the cavity.

The cavity 18 and foam material 19 are shown extending into a recess 150 in the heel 15 which recess is further shown of extended depth in Figure 2.

The shoe is conveniently retained on a last or other support for the insole 20 during injection, the last serving to maintain the desired profile of the insole of the shoe.

The pressure injection oζ for example, a reactive, high resilience chemical foam into the cavity 18 is particularly suited to Goodyear welted footwear. It is also suited to other construction methods of manufacture where units (i.e. the combined heel and sole) have a cavity in the fore part waist and heel as shown. Variation of the quantity of synthetic material injected and/or the pressure at which the material is injected allows the cushioning effect of the material to be varied easily, enabling a range of footwear providing different cushioning to be produced. By injecting a synthetic foam material one can ensure that the whole of the cavity 18 is filled by the material to provide a full cushioning effect between the outer sole and the insole.

Injection can be effected using, for example, specialist low pressure metering apparatus. In trials, a mixture of base resin and hardening agent (typically Diphenylmethane 4,4' Di-isocyanate) at a

ratio of 3:1 was injected into the cavity 18 of a shoe at ambient temperature. Table I below sets out the details of the quantities used to inject five different shoes, all of which provided a noticeable improvement in comfort in the footwear. Ideally, a foam density of 0.2 - 0.3g/cm is employed. The mix used also resulted in a "skin" forming on the outside of the injected material, this skin restricting water penetration into the body of the foam material.

TABLE I

Injected Injection

Material Rate Injection

Weight (g) (g sec) Time

60 14.5 4.2

65 14.5 4.5

70 14.5 4.8

75 14.5 5.2

80 14.5 5.5

In a further form of the invention, the sole 14 is a single layer sole and the cavity or cavities 18 are formed in the single layer sole.

Although the bore 22 is described as being provided in the outer sole 16, it will be appreciated that the synthetic material can be injected into the cavity at any convenient location, for example through the shoe insole 20.