Foot form bed

Abstract

 57 A foot form bed (10) for a sandal or other article of footwear is moulded from polyurethane (12) with twenty or more wooden dowel (14) elements arranged as inserts in a regular array. The wooden dowel (14) elements provide relatively hard sites in the foot engaging surface which mimic the feel of a rigid wooden foot bed whilst the interstitial polyurethane (12) material provides flexibility. The dowel (14) elements may extend through the major part of the depth of the bed with possibly a relatively thin walking sole (18) being added. Alternatively, the dowels (14) may be formed in a relatively thin layer of polyurethane which it is subsequently bonded to a softer polyurethane base (44).

Description

[0001] This invention relates to the foot form bed of an article of footwear.

[0002] It has long been appreciated that a foot form bed of solid wood has important advantages in the ability to produce a rigid and contoured foot engaging surface which not only offers proper support, but also exercises the foot. Merit has been seen as well in the natural moisture-absorbing properties of wood which make the sandal or other article of footwear more comfortable to wear. Against these known advantages of a solid wood foot form bed, certain drawbacks are recognised. First, undesirably high shocks may be transmitted to the foot during walking. For this reason it has been proposed to form a resilient outer sole beneath the wooden foot form bed. A further drawback, in certain cases, is the lack of flexibility which prohibits the foot form bed from following the differing movements of parts of the foot during walking. In attempts to overcome this second drawback, it has been proposed (see for example US-A-4,117,582) to separate front and rear portions of a solid wood foot form bed with a flexible connecting portion or hinge of, for example, foamed polyurethane. In these previous proposals, the flexible portion constitutes a hinge extending across the width of the foot bed generally beneath the ball of the foot. In one modification, (see US-A-4,400,894) it is suggested that the hinge be spread over the region of the ball of the foot by forming alternating wood and foamed polyurethane parts, each extending across the width of the foot bed.

[0003] Whilst this proposal does provide a degree of flexibility, this is confined to a hinge action, whether along a straight line or a narrow transverse region beneath the ball of the foot. Moreover, difficulties have been encountered in adhesion between the wood and the polyurethane, since the contacting surfaces are relatively small and the bending loads relatively high. Indeed it is suggested in one prior proposal, (see US-A-4,400,894) that the contacting surfaces be shaped, as viewed in cross-section, to reduce the risk of fracture at this point.

[0004] It is an object of this invention to provide an improved foot form bed which retains many of the advantages of a solid foot form bed, for example of wood, whilst offering a degree of flexibility throughout substantially the entire bed, or in another aspect the entire fore part of the bed.

[0005] Accordingly, the present invention consists, in one aspect*, in a foot form bed for an article of footwear, comprising a body of flexible material having embedded therein a plurality of rigid elements which are of substantial depth relative'to the depth of said body and are small in longitudinal and transverse dimension relative to the corresponding dimensions of the bed, which serve to provide an array of relatively hard sites over a substantial portion of the foot engaging surface of the bed, the interstitial material providing a degree of flexibility throughout said portion.

[0006] The invention will now be described by way of example with reference to the accompanying drawings in which:-

Figure 1 is a plan view of a foot form bed according to this invention,

Figure 2 is a side view of the bed shown in Figure 1,

Figure 3 is a plan view of a modified foot form bed according to this invention,

Figure 4 is a side view of the bed shown in Figure 3, and

Figure 5 is a plan view of a further modified foot form bed according to this invention.

[0007] Referring to Figure 1, the foot form bed shown generally at 10 comprises a body 12 of foamed polyurethane in which are embedded a large number of wooden dowel elements 14. In this example, the dowels are of identical cross-section with a diameter of about 9 millimetres. The elements are arranged in a substantially regular array with a typical spacing, axis to axis, of about 12 millimetres. As is apparent from Figure 1, the elements do not extend to the edges of the bed 10 and a margin 16 is left clear around the entire periphery of the bed.

[0008] As is shown more clearly in Figure 2, the dowels 14 extend and are open to the foot engaging surface of the bed so that they are able to absorb moisture from the foot. For this reason, it is desirable that the dowel elements are cut with the cylindrical axis parallel to the grain of the wood. At the underside of the bed 10, an outer sole 18 is formed; this may be integral with the body 10 or formed separately of the same or different material.

[0009] The dowel elements vary in length such that the upper exposed surfaces of the elements define - as an envelope - the desired shape of the foot engaging surface.

[0010] The described foot form bed may be produced by moulding a polyurethane body 12 in a complementarily shaped mould having the dowel elements 14 as inserts. Alternatively, a large block of polyurethane may be moulded with lengths of dowel as inserts, the resulting block being machined after moulding to produce the desired shape. For reasons of manufacturing economy, it may be desirable to produce different sizes of foot bed from the same or identically formed blocks. To this end, each size might have the same array of dowel elements with a differing width of margin 16.

[0011] After moulding of the composite block 20, it can usefully be frozen cryogenically to enable the further shaping to be carried out with techniques similar to conventional wood machining. Other techniques may suggest themselves to the man skilled in the art.

[0012] It will be understood that the interstitial polyurethane material throughout the foot form bed will provide a degree of flexibility. With appropriate choice of polyurethane material and selection of the size and disposition of the dowel elements, this flexibility can be adjusted to enable the finished article of footwear to follow walking movements of the foot in optimum fashion. Preferably, the polyurethane will have a Shore hardness of 50 although a hardness in the range 35 to 75 would be possible. Despite this flexibility, the dowel elements provide an array of relatively hard sites over the foot engaging surface which mimic the "feel" of a solid foot engaging surface. Moreover, it is felt that the provision of an array of relatively hard sites in a relatively flexible body may have foot massaging properties not present in a continuous hard surface. This massaging effect may be enhanced by causing the dowel elements to project to a slight extent from the surrounding surface of the flexible material, the top surface of each dowel element then being preferably domed.

[0013] In a modification which is illustrated in Figures 3 and 4, the dowel elements are arranged over the fore part only of the foot form bed. Over the heel region, there is positioned a relatively thin wooden block 30. This provides a continuous wooden foot engaging surface over the heel region in which the requirement for flexibility is of course reduced.

[0014] A further modification is illustrated in Figure 5 of the accompanying drawings. In this embodiment, the dowel elements 40 extend through a layer 42 of relatively hard polyurethane which is then bonded to a base 44 of relatively soft polyurethane to produce the foot form bed. The array of dowel elements within the layer 42 may be as shown in Figure 1 or may take other convenient forms. The depth of the layer 42 is in this example 4 millimetres although a range of 3 to 8 millimetres is quite acceptable. In one example, the polyurethane of the layer 42 has a Shore hardness of 85 although a range of 70 to 90 would be possible. The base 44 may have a hardness in the range of 35 to 70.

[0015] In the illustrated embodiment, the base 44 has a contoured upper surface which is followed by the relatively thin and therefore flexible layer 42. In other forms, the upper surface of the base ₄₄ may take a different shape or may indeed be planar.

[0016] It is contemplated that the layer 42 will be produced by inserting the dowel elements through one side face of a mould having a thickness equal to or slightly exceeding the desired thickness of the layer. After injection moulding of polyurethane around the dowel elements, the protruding elements on the underside of the layer are machined to produce a smooth surface suitable for bonding to the base 40.

[0017] In further modifications, the size of the wooden dowel elements may be varied and the range 5 millimetres to 20 millimetres is believed to be suitable. The size of the dowel elements and possibly also the spacing between adjacent elements may be varied over the foot engaging surface. In this way the optimum levels of hardness and flexibility can be provided at the ball, instep and heel. Similarly, the shape of the rigid elements may vary over the foot engaging surface or may be constant but different from the circular cross-section described above.

[0018] It is believed desirable to leave a margin which is free from the dowel or other rigid elements. This is for the purposes of, first, presenting a homogeneous vertical edge and, second, to facilitate production of different size beds from a single block. However, with other manufacturing techniques, it may be appropriate to have a spacing at the edge of the bed which is no greater than the spacing between adjacent elements elsewhere in the bed. It has been explained that with the use of rigid elements formed of wood, a useful moisture absorbent property is achieved. For this purpose, the elements should extend to the foot engaging surface.. If this property is not required, a thin inner sole may be provided over the foot engaging surface, the depth of this inner sole being sufficiently small as not to interfere with the supporting function of the rigid elements. If the moisture absorbing property is not required, it may be appropriate to form the rigid elements of a material other than wood. Similarly, whilst the described embodiments utilise polyurethane, other flexible materials may in certain circumstances be suitable.

[0019] In a further modification, the wooden block illustrated in Figures 3 and 4 may be positioned in the fore part of the sole rather than at the heel as shown. Indeed, the 4 block may be varied further in shape or position or even omitted, it being regarded as important - however - that the dowel or other rigid elements provide an array of relatively hard sites over a substantial portion of the foot engaging surface of the bed.

Claims

1. A foot form bed for an article of footwear, comprising a body of flexible material having embedded therein a plurality of rigid elements which are of substantial depth relative to the depth of said body and are small in longitudinal and transverse dimension relative to the corresponding dimensions of the bed and which serve to provide an array of relatively hard sites over a substantial portion of the foot engaging surface of the bed, the interstitial material providing a degree of flexibility throughout said portion.

2. A foot form bed according to Claim 1, wherein the rigid elements extend through the depth of said body.

3. A foot form bed according to Claim 2, wherein the body forms a major portion of the depth of the completed foot form bed.

4. A foot form bed according to Claim 2, wherein the body is laminated with a base portion having a greater depth than that of said body.

5. A foot form bed according to Claim 4, wherein the material of said body is harder than the material of said base portion.

6. A foot form bed according to any one of the preceding claims, wherein the spacing between any adjacent pair of elements is less than the extent of either element in the direction of the spacing.

7. A foot form bed according to any one of the preceding claims, wherein the depth of each element is greater than the longitudinal or transverse dimension of that element.

8. A foot form bed according to any one of the preceding claims, wherein the longitudinal and transverse dimensions of each element are between 5 and 20 millimetres.

9. A foot form bed according to any one of the preceding claims, wherein at least twenty and preferably about one hundred rigid elements are embedded in the body.

10. A foot from bed for an article of footwear, comprising a body of flexible material having embedded therein and extending through the depth thereof a plurality of rigid elements serving to provide a plurality of relatively hard sites over a substantial portion of the foot engaging surface of the bed.

11. A method of manufacturing a foot form bed for an article of footwear, comprising moulding a body of mouldable flexible material with at least about twenty rigid elements as inserts in . a substantially regular array.

Drawing