Introduction

This invention relates to orthotic footwear and, more particularly, to soles for use in footwear, the soles incorporating orthotic devices.

Background of the Invention

Podiatrists, in treating foot disorders, freguently recommend the use of orthotics in footwear. Orthotics are shaped rubber or plastics inserts that are used to improve the physical angulation and load bearing characteristics of the foot. Podiatrists also attribute poor quality and ill fitting footwear to the cause of many biomechanical problems in feet. The thong, sometimes known as a flip flop or jandal, is a very popular item of footwear that essentially comprises a flat rubber or plastics sole that is held to the foot by a toe strap. Thongs are cheap, readily available and viewed as casual fashion items.

They are thus popular the world over. Unfortunately, however, thongs do not provide the degree of orthotic support that podiatrists require from footwear.

Furthermore, because thongs are viewed as fashion items, the incorporation of orthotics into thongs substantially reduces their commercial attractiveness.

It is these issues that have brought about the present invention . Summary of the Invention

According to one aspect of the present invention, there is provided a footwear sole comprising a laminate of

superimposed contoured elements of varying density. The expression ^ole' as used herein is understood to embrace the entire sole of footwear or a component layers of the sole of footwear. The expression also embraces an insert that can be placed inside footwear.

Preferably a first contoured element of one density is superimposed on a second contoured element of a different density to form a substantially flat laminate. In a preferred embodiment, the elements are fused together during manufacture. Preferably, one element is

manufactured of high density polyurethane with the other element being manufactured in low density polyurethane. The elements are profiled to provide a variety of types of orthotic support.

In a preferred embodiment, the sole is designed for general use without being specific to the problems of a particular patient. In other embodiments, it is

understood that the sole could be custom built to provide podiatrists solutions to a variety of foot problems.

Preferably, the sole is the sole of a thong that

incorporates holes to support a toe strap.

In other embodiments, the sole may be incorporated in a variety of footwear including open sandals, and sporting shoes .

Description of the Drawings

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a perspective view of a thong incorporating a sole of the invention;

Figure 2 is a perspective view of a first lower element forming part of a laminate that makes up the sole; Figure 3 is a perspective view of a second upper element that forms the other part of the laminate;

Figure 4a is a plan view of the sole that is the subject of one embodiment of the present invention;

Figures 4b to 4e are cross sectional views of the sole taken on the lines of AA, BB, CC, and DD of Figure 4a; Figure 5a is another plan view of the sole;

Figures 5b to 5i are cross sectional views taken on the lines of EE, FF, GG, HH, II, KK, and LL of Figure 5a; Figure 6 is an illustration of foot pronation viewed from the rear;

Figure 7 is an illustration of foot supination viewed from the rear; and

Figure 8 is a rear view of a foot in a neutral position. Description of the Preferred Embodiment

Figures 1 and 2 of the accompanying drawings illustrate a thong 10, sometimes known as a flip flop or jandal.

Thongs 10 are a very popular form of footwear and usually comprise a rubber or plastics substantially flat sole 11 with a toe strap 20 that is secured to the sole by extending through a single hole 16 at the front and then a pair of spaced holes 17, 18 approximately mid-way along the length of the sole 11. The thong 10 has become a very popular means of casual wear and thongs are sold the world over in huge quantities . Unfortunately, podiatrists consider the thong to have substandard characteristics in terms of biomechanical support . The sole 11 of the thong 10 illustrated in the

accompanying drawings is formed as a laminate of a lower element 12, shown in Figure 3, and an upper element 13, shown in Figure 4. Each element 12, 13 is profiled to provide a degree of orthotic support but when the two elements are superimposed and fused together during the manufacturing process, they assume the substantially flat profile shown in Figures 1 and 2 which ensures that the sole 11 looks like the sole of a conventional thong.

However, the orthotic properties of the sole 11 come about through the profiling of the elements 12, 13 and the use of plastics of differing density in their manufacture.

Thus the lower element 12 is profiled to have a raised heel control area 15 and is produced in high density polyurethane. The upper element 13 has differently profiled surfaces and is manufactured of low density polyurethane . The high density polyurethane has a rigidity of between 65 and 70 degrees whilst the low density polyurethane has a rigidity of between 45 and 50 degrees. When the two elements 12, 13 are fused together, they form the

substantially flat laminate structure 11 shown in Figures 1 and 2. The elements 12, 13 are formed with the

anchorage holes pre-positioned, namely a central hole 16 towards the front of the sole and two spaced holes 17, 18 adjacent the midlength of the sole 11. These holes 16, 17, 18 accommodate the toe strap 20 as shown in Figures 1 and 2.

In Figures 6 and 7, a conventional sole S is shown in use. Figure 6 shows a typical pronation problem where the ankle A of the foot leans inwardly on the medial side M. Figure 7 shows a supination problem where again the ankle A is leaning outwardly on the lateral side L. With the sole 11 shown in Figure 8, that is the orthotic sole that is the subject of this application, the ankle A assumes a neutral position without leaning to either the medial M or lateral L sides. This sole 11 provides the podiatric qualities that ensure adequate biomechanical orthotic support and provide the conventional thong with the orthotic support that specialists require without changing the overall appearance of the thong.

The contour of the elements 12, 13 of the sole 11 of this invention not only diminishes the tendency of

pronation/supination of the foot in astatic position but also facilitates increased stability and control of the foot during gate. This is achieved by creating a

"locking" of the mid tarsal and subtalar joints during the push off phase of gate minimising stress on supporting tissues such as muscles and ligaments. The risk of developing biomechanical aberrations such as pronation/ supination and their possible sequelae is thus decreased. This is achieved by the following characteristics of the higher density lower contoured element 12 as demonstrated in Figures 4 and 5:

Close to 10 degree inversion angle of the rear foot support (a) (Figures 5b and 5c) ;

Elevated contour under medial plantar aspect of talar area (bl) extending into metatarsal region (b2) minimising talar inversion and supporting medial longitudinal arch of foot (b) (Figure 4e) ;

Elevated contour extending anteriorly from the medial arch support creating an anterior

(transverse) arch support (Figure 4d) ;

Extended elevated (~5mm) contour (from the calcaneum) under lateral tarsal (cuboid) and 5 th metatarsal bones allowing for locking of mid tarsal and subtalar joints during push off phase of gate (c) (Figure 4b) ;

• This extended lateral contour finishing well into the lateral metatarsal area minimising talar eversion and supporting the lateral arch of the foot (Figure 4c) ;

The higher density lower element 12 with the supporting contour will extend the whole size of the sole. It will then be covered by a lower density upper element 13 of congruent opposite contour and moulded or glued together. This concept provides a flat looking sole with sufficient accommodation of the foot onto the controlling lower element. In other words, a thong 10 with a flat sole 11 incorporating an orthotic supporting layer.

In addition the upper lower density layer 13 together with the lower higher density layer 12 create a unique dual shock absorption effect. The upper layer when transferring body weight onto the firmer lower layer is creating a dispersive shock absorption effect whilst the force passing through the lower denser layer is directed in a standard more vertical fashion.

Although the preferred embodiment relates to thongs, it is understood that this invention is applicable to a wide variety of soles including inserts that can be used in a wide range of footwear including sporting footwear.

The sole described above provides both pronation and supination support via an invisible inbuilt triple arch. Namely, arches on the inside outside insert and transverse to the sole. The inclination across the heel of the lower sole element provides rear foot control. This sole also provides metatarsal locking and provides a dual action shock absorption caused by the different absorption capacities of the upper and lower sole elements. All these features are provided in one substantially flat sole .

The biomechanical and orthotic qualities of the sole have been designed in a generic sense so that they provide orthotic improvements for a wide variety of podiatric problems. It is, however, understood that soles could be custom built to deal with specific problems and the custom building of such soles would be in the choice of densities of plastics and the profiling of the elements.

In the claims which follow and in the preceding

description of the invention, except where the context requires otherwise due to express language or necessary implication, the word "comprise" or variations such as "comprises" or "comprising" is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.