GB2137474A - Shoe construction - Google Patents

Abstract

A shoe construction comprises a moulded insole (1) and a moulded heel (5) interlocked by a boss (9) on the heel which fits in a complementary recess (10) in the insole. Nails or the like are used to fix the insole to the heel, but forces in the direction of arrow (21) are resisted by the interengaging surfaces (19,19A) of the boss (9) and recess (10). <IMAGE>

Description

SPECIFICATION Shoe construction This invention relates to a shoe construction, and more particularly to a shoe construction which can readily be manufactured by using moulded, preferably injection moulded components.

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. Traditionally, the heel has been joined to the composite insole, as by nailing.

The use of composite insoles and heels 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 and heels of any one particular size and shape produced will be relatively small. This adds to the cost of manufacture.

An apparent answer to the problem outlined above is to manufacture an insole and heel as a single 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 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, they tend to be expensive and this makes an integral sole and heel unit expensive to manufacture. Further, the cost of a mould to produce an integral unit is high, and if production runs are relatively small due to rapid changes in fashion this again adds to unit costs.

According to the present invention there is provided a shoe construction comprising an insole and a heel, the insole and the heel being separate integral mouldings and having interengaging means for positively locating the heel relative to the insole.

The present invention enables a basic insole and heel structure for a shoe to be assembled from two integrally moulded components, namely an insole and a heel. The insole may be manufactured to have the desired combination of flexibility and rigidity, and the heel can be manufactured from a relatively inexpensive material well suited to the construction of heels.

Preferably the insole comprises an integral moulding have 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 bound ed 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-size 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.

In the preferred embodiment, the insole is moulded with a structure to interfitwith and preferably to form a positive imterlock with a complementary structure moulded on the 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 insole 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 complementary to the recess. The vertical height to 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 of the invention will become clear from the following description of a preferred embodiment thereof, given by way of example oniy, 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 ratelyformed heel Figure 2 is an underneath plan view of the insole of Figure 1; Figure 3 is a section on the line Ill-Ill of Figure 2; Figure 4 shows an intermediate stage in the manufacture of the insole of Figures 1-3; and Figures 5 and 6 are respectively sections on the lines V-V of Figure 1 and Vl-VI of Figure 5.

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. One such moulding material is a blend, in suitable proportions, of API LON 737 and APILON 1387 as supplied by APPLICAZIONI PLASTICHE INDUSTRIALI Spa of Mussolente, Italy.

A heel 5 which is an injection moulding made from a material conventional in the art for the manufacture of heels e.g. high-impact polystyrene, 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, as described in greater detail hereinafter.

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 of the forepart to the minimum thickness which can readily and consistently be moulded in mass production injection moulding machines. If this minimum thickness of the peripheral 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 forepart to a desired level, and this is achieved without resorting to injection moulding material to an undesirably thin section. The margin 13 of the forepart is cut or moulded to any desired shape, and the edge 14 defining the aperture is preferably moulded tapering to a knife edge in order to provide a steady transistion 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, irregularites 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, eg. 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 reaily 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 cutting 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 the aperture 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 reliably 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 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-edgeofthe 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 the 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 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.

Referring now to Figures 5 and 6, the structure of the boss 9 and recess 10 is shown in more detail. It should firstly be pointed out that whilst, in the interest of clarity, a small gap has been shown between the insole 1 and heel 5, such gap does not exist in practice, except when specifically created as described above to produce a gap for receipt of the lasted over edge of a closed back shoe.

The boss 9 has flat lateral faces 15,16 which are snugly received between mating flat faces 15A, 16A of the recess 10. Accordingly, the heel is positively located in the rotational sense, i.e. it cannot rotate about its longitudinal axis 17 relative to the insole.

The front 18 and rear 19 faces of the boss, and corresponding faces 18A, 19A of the recess, are parts of the surface of a right circular cylinder having an axis parallel to the longitudinal axis 17. It will be noticed that the axis 17 extends obliquely to the line 20 which is normal to the general zone of contact of the heel and insole. Thus, rotational forces in the general direction of the arrow 21 to which the heel is commonly subjected in use are well resisted by the interengagement of the rear boss surface 19 with the corresponding recess surface 19A. In fact, these two surfaces 19,19A have a wedging effect such that forces acting in the direction of the arrow 21 tend to force the heel and insole into more intimate engagement. This is in contrast to conventional construction in which nails are relied upon to provide the sole fixing of the heel.

Claims (10)

1. A shoe construction comprising an insole and a heel, the insole and the heel being separate integral mouldings and having interengaging means for positively locating the heel relative to the insole.

2. A shoe construction according to claim 1 wherein the interengaging means comprises a recess in one of the insole and heel and a boss having a cross-section complementary to that of the recess on the other of the insole and heel.

3. A shoe construction according to claim 2 wherein the boss includes at least one non-circular portion to prevent rotation of the heel about its longitudinal axis relative to the insole.

4. A shoe construction according to claim 2 or claim 3 wherein the boss extends obliquely to the line normal to the zone of contact of the heel and the insole whereby force applied to the base of the heel and directed towards the toe of the insole is resisted by interengaging surfaces of the heel and insole.

5. A shoe construction according to any of claims 2 to 4 wherein the height of the boss is greater than the depth of the recess.

6. A shoe construction according to any preceding claim wherein the insole comprising an integral moulding having a forepart, a waist region, and a rear region, and 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.

7. A shoe construction according to claim 6 wherein an aperture is provided in the central zone of the forepart.

8. A shoe construction according to claim 7 wherein the edge of the peripheral zone defining the aperture is tapered in transverse cross-section.

9. A shoe construction 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.

10. A shoe construction substantially as herein described with reference to the accompanying drawings.