GB2136671A - Shoe component - Google Patents

Abstract

An insole (1) is injection moulded from a plastics material to give a flexible forepart (2), a rigid waist (3) and rear (4) regions. To provide adequate flexibility without using excessively thin sections the forepart (2) has a central aperture (12) which is filled during shoe manufacture by a foam filler. A recess (10) in the rear region (4) mates with a complementary boss on a heel to locate the heel. The forepart (2) is preferably moulded over-size and cut to the final profile. <IMAGE>

Description

SPECIFICATION Shoe component This invention relates to a shoe component, and more particularly to a shoe component which can readily be manufactured by moulding, preferably by injection moulding.

In most shoe constructions the forepart of the shoe should be flexible to allow the shoe to bend as the heel is raised during normal walking, and the central waist region of the shoe should be fairly rigid to provide adequate strength for the shoe and to support the foot. Traditionally this has been achieved by use of a composite insole which is relatively thick and rigid in the waist and rear regions, and relatively thin and flexible in the forepart. The rigid rear region provides a rigid attachment for the heel, and the insole may include a metal shank to reinforce the heel attachment region and the waist region.The flexible forepart may be provided by a sheet of flexible material, e.g. fibre board, which extends the full length of the insole and is laminated with other materials in the waist and rear regions, or by a sheet of flexible material which terminates at the rear of the forepart and is there joined to the remainder of the insole.

The use of composite insoles as outlined above has a number of disadvantages. The fact that the insole is a composite structure comprising a plurality of assembled components means that the insole is time consuming and expensive to manufacture, and is prone to failure in use due to defective design, materials, or workmanship. The problem is aggrevated by the fact that in general, as fashions change, the insole will be re-designed with varying heel height and shoe shape, and accordingly the number of insoles of any one particular size and shape produced will be relatively small. This adds to the cost of manufacture.

As apparent answer to the problem outlined above is to manufacture an insole as a single integral member by means of injection moulding. However, heretofore no satisfactory commercial injection moulded insole having a flexible forepart has been produced. This is in part due to the lack, until recently, of a moulding composition which is available at reasonable costs and yet which will, if moulded in a sufficiently thin section, provide the combination of tensile strength, flexibility, and flexlife required for the forepart. Whilst materials having the desired characteristics are now available, it has been found that in order to provide the desired flexibility, the section to which the forepart must be moulded is so thin that it cannot readily be accomplished in mass production injection moulding machinery, such as would be used to provide commercial insole units.

According to the present invention there is provided an insole for a shoe, comprising an integral moulding having a forepart, a waist region, and a rear region, wherein the forepart is bounded by a peripheral zone which has a cross-sectional thickness greater than the thickness of material, if any, in the central region of the forepart.

In the preferred embodiment of the invention the central region of the forepart is completely omitted so that the forepart consists solely of the peripheral zone. This enables the peripheral zone to be of a thickness compatible with ready mass production moulding, whilst at the same time ensuring that the overall flexibility of the forepart is adequate. During subsequent assembly of a shoe the aperture in the centre of the forepart is filled with a suitable filler, e.g. of foam, thereby giving a smooth upper surface to the insole for receipt of a sock and a smooth lower surface to the insole for receipt of an outer sole.

Whilst in the preferred embodiment an aperture is provided in the central region of the forepart, it will be appreciated that a continuous web of material may span the region enclosed by the peripheral zone. The web will be thin relative to the peripheral zone so as not to impede unduly flexing of the forepart. Whilst provision of such a web is more difficult than the provision of an aperture, it is nonetheless possible in mass production injection moulding machinery because the thin web is bounded on all sides by the relatively thick peripheral zone.

In effect, by thickening the peripheral zone and thinning the central region the overall flexibility of the forepart can be made satisfactory, whilst the problem of moulding a section which is thin over its entire extent is avoided.

In the preferred embodiment of the invention the insole is manufactured by first moulding a unit with an over-sized forepart, and then cutting the forepart back to the desired peripheral profile. Preferably, the forepart is initially moulded to a castor profile and is then trimmed to the desired finished profile. By this technique, changes in fashion can, within limits, be accommodated merely by different trimming of the initial castor profile, without change to the mould tools. This is particularly advantageous in that it extends the life of any given production run of insoles. The trimming of the castor profile may desirably be accomplished by means of a press tool.

The insole may be moulded with an integral heel.

However, in the preferred embodiment the insole is moulded with a structure to interfit with a complementary structure moulded on a separate heel to provide positive location of the heel and insole. The insole may then be secured to the heel by any suitable means, for example welding, adhesive bonding, nails, or the like. Again, the use of a detached heel enables changes in fashion to be accommodated without changes to the and mould tools, and within limits allows a range of basic shoe shapes to be manufactured from a single insole moulding. Further, since the mechanical stress to which the heel is subjected is less than that to which the insole is subjected, significant savings can be made by moulding the heel as a separate unit from a relatively inexpensive moulding material.

In a particularly preferred embodiment of the invention the insole is provided in combination with a separately formed heel, one of the insole and heel being provided with a recess, and the other of the insole and heel being provided with a boss com plementarytothe recess. The vertival height the boss may be equal to or less than that of the recess, in which case, the heel will fit flush with the insole around the periphery of the interface between the heel and the insole, or the height of the boss may be greater than the depth of the recess, whereby a peripheral groove will be formed between the insole and the heel to accommodate the lasted edge of a shoe upper.

The above and further features and advantages will become clearer from the following description of a preferred embodiment thereof, given by way of example only, reference being had to the accompanying drawings wherein: Figure 1 is a side view of an embodiment of insole according to the invention assembled with a sepa rately formed heel; Figure 2 is an underneath plan view of the insole of Figure 1; Figure 3is a section on the line Ill-Ill of Figure 2; and Figure 4 shows an intermediate stage in the manufacture of the insole of Figures 1-3.

Referring firstly to Figures 1-3, the insole 1 illustrated comprises a forepart 2, a waist region 3 and a rear region 4. The insole is an integral injection moulding and is formed from a moulding material having the characteristic of rigidity in a relatively thick section, and flexibility and long flex-life in a relatively thin section.

A heel 5 which is an injection moulding made from a material conventional in the artforthe manufacture of heels is secured to the insole 1 by means of nails 6. As is conventional, the heel 5 includes a moulded in rod 7, to reinforce the heel and to receive a heel tip 8.

The upper end of the heel 5 is formed with an upstanding boss 9 which is received in a complementary recess 10 provided in the underside of the insole. The complementary boss 9 and recess 10 ensure accurate and reliable alignment of the heel relative to the insole, and greatly assists in strengthening the connection between the heel and the insole. The connection between the heel and the insole may be effected by means other than the nails 6, or means additional to the nails 6, e.g. adhesive, may be provided to assist in securing the heel to the insole.

The thickness and shape of the insole in the waist region 3 and rear region 4 is such that these regions are sufficiently rigid to form the load-bearing platform of a shoe without the need for further loadbearing components. This rigidity is preferably accomplished by means of the cross-sectional area and shape of the waist region 3 and rear region 4, although strengthening members may be incorporated in this region either by placing such members in the cavity of the mould during moulding of the insole, or by providing a moulded recess in the upper or lower surface of the insole to receive a reinforcing shank.

The forepart of the insole 1 is flexible in order to allow the finished shoe to bend in the forepart in the conventional manner. The flexibility is achieved by reducing the thickness of the forepart in the peripheral zone 11 oftheforeparttothe minimum thickness which can readily and consistently be moulded in mass production injection moulding machines. If this minimum thickness of the peripher al zone was carried across the full width of the forepart, the forepart would be excessively rigid. In order to overcome this difficulty an aperture 12 is provided in the central zone of the forepart.

The effect of the aperture 12 is to reduce the overall rigidity of the forepartto a desired level, and this is achieved without resorting to injection mould ing material to an undesirably thin section. The margin 13 of the forepart is cut or moulded to any desrired shape, and the edge 14 defining the aperture is preferably moulded tapering to a knife edge in orderto provide a steady transition from the full thickness of the peripheral zone 11 to nothing. Since flash and other irregularities at the edge 14 are not critical to the shoe construction, the relatively poor finish that will be obtained when moulding to a knife edge is not critical.

If preferred, the aperture 12 may be omitted and the peripheral zone 11 can be spanned by a thin web of moulding material. Again, irregularities or holes in such a web will not be critical, and the web will be relatively easy to mould since it is edged all round by a relatively thick zone.

During assembly of a shoe an upper may be lasted over onto the peripheral zone 11 and suitably secured, e.g. as by adhesive. A suitable filler, e.g. of foam plastics material can then be inserted in the aperture 12 to provide a smooth lower surface for the receipt of an outer sole. The usual cover sock secured within the shoe to the upper surface of the insole will cover the upper surface of the filler, if this is exposed through the aperture 12.

It will be appreciated that the insole described above provides the highly desirable characteristics of rigidity in the waist and rear regions and flexibility in the forepart in an injection moulding which can readily be realised in mass production.

Preferably, the insole 1 of Figure 2 is produced from the basic injection moulding shown in Figure 4.

This injection moulding 15 includes a castor-profile forepart 16 of uniform thickness. By cuting along the dotted line shown in Figure 4, e.g. by means of suitable press tools, the insole 1 of Figure 2 can be produced. However, in the event that fashion changes dictate a change in forepart profile, the shape of the forepart of the finished insole can be changed simply by changing the press tools, and without need to change the injection moulding tools.

This offers a considerable saving in manufacturing costs by avoiding the necessity of manufacturing new injection moulding tools each time a change in forepart profile is required.

Although in the preferred embodiment the aperture 12 is formed during the injection moulding operation, it will be appreciated that in some circumstances it may be possible to form the aperture 12 during the press-cutting stage which forms the forepart external profile. In general, such a means of forming will be less satisfactory than forming the aperture during moulding since the cut edges of the aperture will be square rather than tapering as illustrated at 14 of Figure 3. However, such a technique is within the scope of the invention.

It will be appreciated that the invention provides an insole which can readily and reiiably be secured to a heel to form the structural body of a shoe. The insole may be formed as an integral injection moulding and is thus inexpensive as compared with composite structures assembled by skilled workers from several structural components. Further, the very high flex-life of moulding materials suitable for manufacturing the unit ensures a long and reliable life expectancy.

In the embodiment shown in the drawing the boss 9 has a height substantially equal to the depth of the recess 10. However, by making the height of the boss 9 greater than the depth of the recess 10 an aperture can be created between the insole and the heel. This arrangement is particularly advantageous in the manufacture of closed back shoes since the recess between the heel and insole receives the lasted over-edge of the upper. In practice, the upper will in this case be lasted onto the insole before the heel is secured, the heel serving to cover and hide the edges of the upper.

In a modified embodiment of the invention a suitable sheet of material, having substantially the same thickness as the thickness of the peripheral zone 11 and substantially the same shape as the aperture 12, is inserted into the central forepart zone of a mould tool which would, without the insert, mould an insole having a forepart of substantially uniform thickness. The mould tool is then closed and plastics material is injected to form the waist and rear regions of the insole and a peripheral zone around and bonded to the insert. Thus, a composite forepart is formed having a central zone formed by the insert and a peripheral zone of plastics corresponding to the peripheral zone 11 of the drawings.

Of course, in this case the insert should be of a material which does not significantly stiffen the forepart, and thus the stiffness of the forepart will largely be determined by the plastics material peripheral zone, as described above. Whilst this modification involves complications at the moulding stage, it does ease subsequent shoe construction by providing a smooth upper and lower surface to the insole without the need to insert a separate filler.

Claims (10)

1. An insole for a shoe, comprising an integral moulding having a forepart, a waist region, and a rear region, wherein the forepart is bounded by a peripheral zone which has a cross-sectional thickness greater than the thickness of material, if any, in the central region of the forepart.

2. An insole according to claim 1 wherein an aperture is provided in the central zone of the forepart.

3. An insole according to claim 2 wherein the edge of the peripheral zone defining the aperture is tapered in transverse cross-section.

4. An insole according to any preceding claim wherein the insole is cut from a blank at least the forepart of which is over-sized as compared with the finished profile of the insole.

5. An insole substantially as hereinbefore described with reference to the accompanying drawing.

6. An insole according to any preceding claim in combination with a heel, the heel and the insole having complementary interengaging means to locate the heel relative to the insole.

7. A combination according to claim 6 wherein the interengaging means comprises a recess in one of the insole and heel and a boss having a crosssection complementary to that of the recess on the other of the insole and heel.

8. A combination according to claim 7 wherein the height of the boss is greater than the depth of the recess.

9. An insole and heel combination substantially as herein described with reference to the accompanying drawing.

10. A method of shoe manufacture comprising: providing an insole according to any of claims 1 to 5; lasting an upper onto the insole; placing a filler in the central zone of the forepart; securing an outer sole to the insole to cover the edge of the upper and filler; and securing a sock within the shoe to cover any exposed part of the filler.