Abstract:
A heel cup can be inserted into a shoe in order to define a posterior upward projection and lateral wings which surround the posterior and lateral faces of the calcaneum and which, through lateral notches, define a preferential deformation zone at, and in the direction of, the subtalar cone of the tibiotarsal joint. Moreover, a sufficiently-rigid connecting zone connects the posterior upward projection and the lateral wings, thus providing the shoe with good stability while enabling inversion and eversion foot movements. In this way, comfort is increased considerably, while the risk of articular injuries is reduced since the subtalar articulation is contained correctly upon reaching the limit thereof.

Description:
TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention concerns footwear and more particularly, although not exclusively, multipurpose sports shoes, walking shoes, orthopedic shoes. 
         [0002]    Whatever the application concerned, shoes must assume different functions and in particular a function of mechanical protection of the sensitive portions of the foot against impact and a function of holding or supporting the foot and ankle joints. 
         [0003]    To fulfill their function of impact protection, shoes must in particular protect the heel and the area of attachment of the Achilles tendon. 
         [0004]    To fulfill their function of holding or supporting the joints, shoes must in particular limit the forces on the ankle and foot joints when they are close to their maximum amplitude of movement. 
         [0005]    However, a shoe must simultaneously allow free functioning of the ankle and foot joints for the various movements of walking, running, jumping, turning. 
         [0006]    Clearly there is a contradiction between the necessity to protect and to support the ankle and foot joints, on the one hand, and the simultaneous necessity to allow freedom of movement of the joints of the foot and the ankle. In fact, protection and support of the joints are obtained in principle by providing rigid members incorporated into the shoe while freedom of movement necessitates the use of flexible uppers in the construction of the shoe. 
         [0007]    Thus any attempt to stiffen the structure of the uppers of the shoe improves the support of the joints, to the detriment of comfort, i.e. to the detriment of the freedom of movement of the joints. Conversely, improving comfort entails increasing the flexibility of the structure of the uppers of the shoe, but, this time, to the detriment of the functions of supporting the joints and protecting the foot and the ankle. 
         [0008]    There have therefore already been proposed sports shoes consisting in a sole to which is fixed a flexible upper covering the foot and the heel. Such shoes simply provide flexible containment of a portion of the calcaneo-pedal block. The use of such shoes has been generalized to many sporting activities such as tennis, football, athletics, jogging. The design of this type of shoe is not intended to provide containment of the joints of the foot and a fortiori the ankle. 
         [0009]    There have also been proposed sports shoe types known as high-leg shoes, i.e. shoes including not only a pedal cup but also a flexible vamp or upper providing containment of all of the foot and ankle joints. 
         [0010]    Shoes constructed in accordance with this principle are used in many sports such as basketball, football, tennis. The upper of these shoes is flexible so that they provide flexible support and containment. Such shoes therefore do not provide effective protection of the ankle joint in the event of twisting when participating in sports. The ankle joint is in fact insufficiently supported in the event of unexpected twisting, which leads to distension of the sub-astragalus ligaments possibly followed by distension of the tibio-tarsal ligaments. 
         [0011]    In the case of walking shoes, and more particularly shoes intended for mountaineering, the containment of the ankle joints is provided in a quasirigid manner. The protection is effective, but comfort is reduced. 
         [0012]    To improve comfort in the presence of shoes with rigid shell portions providing good protection, it has also been proposed to provide an articulation area between the vamp and the upper, the aim of the articulation being to facilitate the movements of the natural foot and ankle joints. However, although the design of these articulations is relatively well suited to enabling the natural physiological movement of transverse axis rotation of the tibio-tarsal joint, these structures cannot at the same time effectively contain and allow free physiological movements of the sub-astragalus joint of the ankle. This then results either in a lack of comfort or in a lack of protection of the joint, or even a risk of aging and premature failure of the shoe articulation area. 
         [0013]    In the field of athletics, there has also been proposed, in the document U.S. Pat. No. 6,126,626 A, an ankle brace that can be adapted by molding to an ankle, forming an assembly that is structurally independent of a shoe but that the user can nevertheless wear when inserting the foot into a shoe. The ankle brace is attached to the ankle by laces and is not fixed to the shoe. It is made from a sheet the upper edge whereof is free of cutouts. Placed around the ankle, the ankle brace has lateral openings situated below the lateral projections of the sub-astragalus cone of the ankle. This structure aims to prevent the normal physiological movements of eversion and inversion, and this reduces freedom of movement and comfort. 
         [0014]    The document U.S. Pat. No. 3,807,062 A describes an athletics shoe including a relatively rigid sheet in the heel area. This sheet surrounds the posterior portion of the foot from the base up to a point above the calcaneum and its lower edge is fixed to the sole of the shoe. Two symmetrical lateral cutouts are oriented horizontally and situated well above the lateral projections of the sub-astragalus cone of the ankle. The calcaneum is not surrounded laterally in its entirety. Comfort and protection remain insufficient. 
       SUMMARY OF THE INVENTION 
       [0015]    The problem addressed by the present invention is improving both the comfort and the safety of shoes, thereby avoiding the drawbacks of traditional shoes, so as to support the natural foot and ankle joints without compromising comfort. 
         [0016]    Another object of the invention is to propose a particularly simple and inexpensive structure that enables simultaneous improvement of protection and comfort. 
         [0017]    To achieve this, the invention exploits the results of an in-depth study of the natural physiological movements of the foot and ankle joints and of the movements of the different portions of the foot relative to the shoe during movements such as walking, running, jumping and turning. 
         [0018]    It has become apparent in this way that traditional shoes are not sufficiently well adapted to the physiological movements of the foot and ankle joints, and that this is what explains either the lack of comfort or the lack of protection, or even the risk of rapid deterioration of the shoe. 
         [0019]    To achieve the above and other objects, the invention proposes a shoe heel cup comprising an elastically deformable material sheet of appropriate high stiffness conformed to surround the posterior portion of the foot and cover at least the whole of the posterior face of the foot from its base to a point above the calcaneum and extending forwardly, with its lower edge adapted to be fixed to the shoe sole, the sheet comprising, in its upper edge, two lateral cutouts that are symmetrical with respect to each other; the lateral cutouts are oriented so that, when the heel cup is in place in the shoe, the lateral cutouts are substantially at the level of the lateral projections of the sub-astragalus cone and the sheet laterally surrounds the calcaneum. 
         [0020]    The heel cup constructed in this way is a particularly simple and inexpensive item and its use in a shoe considerably improves the trade-off achieved between the necessities of protecting the heel and the joints and the necessities of comfort resulting from a great freedom of movement of the joints. 
         [0021]    The lateral cutouts preferably have a V-shape that diverges towards the front and towards the top of the shoe. This favors elastic deformation of the enveloping area between the edges of the lateral cutouts. 
         [0022]    The aperture angle of the V-shaped lateral cutouts may advantageously be greater than the angle of the sub-astragalus cone, which effectively frees the movements of inversion and eversion of the ankle. 
         [0023]    Cutouts having greater or lesser depths could be envisaged. The depth of the lateral cutouts is preferably such that, when the heel cup is in place in the shoe, the bottom of the lateral cutouts is slightly to the rear of the sub-astragalus joint. This achieves a good trade-off between the comfort resulting from the presence of the lateral cutouts and the protection resulting from the posterior portion of the cup being free of cutouts and absorbing mechanical forces. 
         [0024]    For a shoe size  42 , the heel cup may advantageously be made from a sheet of material delimited by a slightly convex lower edge of length from approximately 12 to 16 cm and by a more strongly convex upper edge including the two lateral cutouts, the central area of the sheet having a height from approximately 4 to 7 cm. 
         [0025]    Another aspect of the invention proposes a shoe including:
       a sole,   an upper fixed to the sole and adapted to envelop the plantar mass of the foot and the calcaneo-pedal block,   a vamp connected to the posterior portion of the upper and adapted to envelop at least the rear upper area of the foot,   a more rigid material heel cup having a lower edge fixed to the sole and conformed to surround the posterior portion of the foot and cover at least the whole of the posterior face of the foot from its base to a point above the calcaneum and to surround the calcaneum laterally,   the heel cup being as defined hereinabove and producing a one-piece reinforcement consisting of a posterior tongue and two lateral wings.       
 
         [0031]    In a first application, the invention may be used in a shoe including an upper and a vamp that are relatively flexible, the heel cup being made from an elastically deformable material more rigid than the upper and the vamp. 
         [0032]    In a second application, the invention may be used in a shoe having an essentially rigid upper, an essentially rigid vamp, and a more flexible upper and/or vamp portion in the area of the lateral cutouts of the heel cup, the heel cup itself being made from a material more rigid than the upper portion and/or the vamp portion situated in the area of the lateral cutouts. 
         [0033]    At least in the area of the lateral cutouts, the upper and/or the vamp may advantageously constitute an elastic deformation area of lower stiffness. 
         [0034]    In all embodiments, the heel cup adapted to be inserted in a shoe defines a posterior tongue and lateral wings that envelop the posterior face and the lateral faces of the calcaneum, at the same time as providing, by means of lateral cutouts, an area of preferential deformation situated at the level of and in the direction of the sub-astragalus cone of the foot joint. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0035]    Other objects, features and advantages of the present invention will emerge from the following description of particular embodiments, given with reference to the appended figures, in which: 
           [0036]      FIG. 1  is a front view in a deployed position of a sheet of material intended to constitute a shoe heel cup according to one embodiment of the present invention, 
           [0037]      FIG. 2  is a side view of the heel cup produced in accordance with the invention from the  FIG. 1  sheet; 
           [0038]      FIG. 3  is a rear view of the  FIG. 2  heel cup; 
           [0039]      FIG. 4  is a perspective view of the  FIG. 2  heel cup; 
           [0040]      FIG. 5  is a diagrammatic lateral external view of the ankle and foot joint in a traditional shoe provided with a rigid or flexible upper; and 
           [0041]      FIG. 6  is a diagrammatic lateral external view of the ankle and foot joint in a shoe provided with a heel cup in accordance with the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0042]      FIG. 5  is considered first, in order to outline the main structural components of a foot joint and the main movements of that joint. 
         [0043]    The foot  1  is represented in a shoe consisting of a sole  2  and an exterior upper  3  represented in dashed lines. 
         [0044]    The sole  2  of the shoe is resting on a horizontal plane P and the shoe extends longitudinally along a vertical plane perpendicular to the plane P, or plane of the figure. 
         [0045]    Of the foot  1 , shown inside the shoe, there are seen the calcaneum  4 , the astragalus  5 , the cuboid  6 , the scaphoid  7  and the cuneiforms  8  that are followed by the metatarsals and the phalanges, not shown. 
         [0046]    The calcaneo-pedal block, consisting of the calcaneum  4 , the cuboid  6 , the scaphoid  7  and the cuneiforms  8 , forms the lower structure of the foot, which rests on the sole  2  of the shoe. 
         [0047]    This calcaneo-pedal block is articulated to the bottom of the leg, indicated by the lower end of the tibia  9 , by a joint with two successive stages, namely a tibio-tarsal joint  10  between the tibia  9  and the astragalus  5 , and a sub-astragalus joint  11  between the astragalus  5  and the calcaneum  4 . 
         [0048]    The tibio-tarsal joint  10  enables movement of the foot in the sagittal plane, i.e. in rotation about a transverse axis perpendicular to the plane of the figure, for example to raise or lower the anterior end of the foot. 
         [0049]    The sub-astragalus joint  11  enables the other movements of the ankle, namely the movements of inversion and eversion. 
         [0050]    By inversion of the ankle is meant a movement that combines a partial or full combination of all of the following movements in the three spatial planes, namely:
       in the horizontal plane P, a rotation called inward rotation, i.e. directed towards the interior face of the opposite foot; this inward rotation has a maximum amplitude of rotation of 30° relative to a normal plumb position of the foot in which the longitudinal axis of the foot is substantially parallel to the sagittal plane of symmetry of the human being;   in the frontal plane, corresponding to a vertical plane F perpendicular to the plane P, an inward rolling with an amplitude of approximately 25° defined relative to the top and bottom extreme amplitude positions of the inward rolling,   in the sagittal plane, or the plane of  FIG. 5 , plantar flexion, with an amplitude of approximately 10° in the direction of the arrow f 1  and defined relative to a normal plumb position of a human being situated on a horizontal plane.       
 
         [0054]    The amplitudes indicated above correspond to average values, each amplitude being liable to vary by plus or minus 10° according to the age of the person and their specific anatomical characteristics. 
         [0055]    By eversion of the ankle is meant a movement that combines in the three spatial planes, in a general direction away from or departing from the sagittal plane of symmetry of the person:
       an outward rotation of 30° maximum in the horizontal plane,   in the front plane F, an outward rolling of approximately 20°,   in the sagittal plane, a dorsal flexion in the direction of the arrow f 2  and with an amplitude of approximately 10°.       
 
         [0059]    Analysis of the movements of the sub-astragalus foot and ankle joint has shown that all these movements of inversion and eversion in the three spatial planes have instantaneous axes of displacement that themselves move in space within a geometrical envelope similar to a circular cone  12  called the sub-astragalus cone. 
         [0060]    The apex S of the cone  12  is at a distance d of a few centimeters to the rear of the calcaneum  4  and at a height H 1  that is approximately one third of the height H of the posterior side of the calcaneum  4 . The median axis  12   a  of the cone  12  passes through the summit S and through the median area of the two bundles of ligaments  13  and  14  that connect the astragalus  5  to the calcaneum  4 . It is found that the median axis  12   a  of the sub-astragalus cone  12  is at an angle a to the horizontal plane P from 20° to 50°, more generally from 30° to 45°. 
         [0061]    Moreover, the sub-astragalus cone  12  has a cone angle β the average value whereof varies from 15° to 30° according to the age of the person and their anatomical peculiarities. 
         [0062]    In a plan view of the foot, i.e. a view from above, the median axis  12   a  of the sub-astragalus cone  12  is also at an angle from 10° to 30° to the sagittal plane, on the interior side, i.e. towards the other foot. 
         [0063]    The above considerations thus define an anatomically and physiologically based geometrical and mechanical model substantially representative of the kinematics of the ankle joint. 
         [0064]    The shoe according to the invention and the shoe heel cup according to the invention aim to favor the movements thus defined about axes moving in the sub-astragalus cone  12  at the same time as limiting those movements to prevent excessive forces on the joint members at the end of the amplitude of movement and providing good protection of fragile portions of the foot. 
         [0065]    According to the invention, to obtain satisfactory freedom of these movements, necessary to obtain sufficient comfort, at the same time as protecting the foot effectively against impact and excess amplitudes of movement, it is necessary to envelop the rear of the foot in a heel cup with lateral cutouts positioned in corresponding relationship to the sub-astragalus cone  12 . 
         [0066]    Consider  FIGS. 1 to 4 , which show a heel cup structure  24  of this kind according to the invention. 
         [0067]    The heel cup  24  is made from a sheet  15  of an elastically deformable material having sufficient stiffness to constitute a shoe reinforcement. The sheet  15  of this material is delimited by a slightly convex lower edge  16  and a more strongly convex upper edge  17  having two lateral cutouts  18  and  19  disposed symmetrically with respect to a median axis  20  generally perpendicular to the lower edge  16 . 
         [0068]    There are therefore seen in the figure a central area  21  intended to constitute a posterior tongue in a shoe and two lateral wings  22  and  23 . 
         [0069]    In practical applications to multipurpose shoes, for a size  42 , the sheet  15  may have a length L from approximately 12 to 16 cm and a height H of the central area  21  from approximately 4 to 7 cm. 
         [0070]    The lateral cutouts  18  and  19  are oriented along respective axes  18   a  and  19   a  inclined at approximately 45°. The lateral cutouts have an aperture angle  18   b  or  19   b  of approximately 30°. Their respective bottom  18   c  or  19   c  is at a distance d 1  of approximately 2 cm from the mid-point M of the lower edge  16 . 
         [0071]    The lower edge  16  may advantageously comprise at least one V-shaped conformation cutout  16   a . The confirmation cutout  16   a  enables the two segments constituting the lower edge  16  to move towards each other to impart to the sheet  15  a concavity in the vertical direction to envelop the rear of the foot. 
         [0072]      FIG. 2  shows the heel cup  24  according to the invention produced from the  FIG. 1  sheet  15  by bending the two wings  22  and  23  parallel to each other and moving the two segments of the lower edge  16  towards each other to close up the conformation cutout  16   a , the central area  21  being curved. Thus there are seen in the figure the wing  22 , the central area  21  forming a posterior tongue and the lateral cutout  18 , the bottom  18   c  of which is forward of the posterior edge  21   a , from which it is separated by a narrow connecting area  21   b  of width d 2  that is sufficiently wide to have sufficient mechanical properties of elasticity and stiffness to control relative movement between the posterior tongue  21  and the lateral wings  22  and  23 . 
         [0073]      FIG. 3  is a rear view of the  FIG. 2  heel cup  24 , in which are seen the two wings  22  and  23 , the posterior tongue  21 , the lateral slots  18  and  19 , the connecting area  21   b  and the conformation cutouts  16   a , the edges whereof are closer together or pressed against each other. 
         [0074]      FIG. 4  is a perspective view of the heel cup in which the same main portions are seen identified by the same reference numbers. 
         [0075]    Consider now  FIG. 6 , which is an external side view of a foot inserted into one embodiment of a shoe according to the invention including the heel cup  24  according to the invention. 
         [0076]    The components of the skeleton of the foot previously described with reference to  FIG. 5  are seen again. 
         [0077]    In  FIG. 6 , the invention is applied to a multipurpose shoe with a relatively low vamp. 
         [0078]    The shoe comprises the sole  2 , the heel cup  24 , an upper  25  and a vamp  26 . 
         [0079]    The sole  2  has the usual structure, chosen as a function of the intended uses. 
         [0080]    The upper  25  is fixed to the sole  2  and is adapted to envelop the plantar mass of the foot and the calcaneo-pedal block. 
         [0081]    The vamp  26 , connected to the posterior portion of the upper  25 , is adapted to envelop at least the upper posterior area of the foot. 
         [0082]    The heel cup  24  is disposed in the shoe to surround the rear portion of the foot, covering at least the whole of the posterior face of the foot from its base to a point above the calcaneum  4 . Its lower edge  16  is fixed to the sole  2 . The heel cup  24  surrounds the calcaneum  4  laterally. 
         [0083]    The posterior tongue  21  and the wing  22  are seen in  FIG. 6 . 
         [0084]    The cutout  18  is oriented substantially to contain the lateral projection of the sub-astragalus cone  12 . 
         [0085]    As seen in  FIG. 6 , the posterior tongue  21  rises to a height greater than or equal to the height of the summit area of the calcaneum  4 . As shown here, the posterior tongue  21  preferably rises to a height from approximately 2 to 4 cm above the summit area of the calcaneum. This protects the area of the bottom insertions of the Achilles tendon against impact. This also favors the absorption of the forces of rotation of the joint members of the ankle, by distributing the bearing forces between the posterior portion of the foot and the shoe over a greater height. 
         [0086]    As seen in the figures, the posterior tongue  21  widens in the upward direction, which laterally envelops the bottom insertions of the Achilles tendon and thus increases the protection thereof against impact. 
         [0087]    The side wings such as the wing  22  extend forwards at least to the anterior end area of the calcaneum  4 . Their height increases towards the front, which enables them to envelop laterally the anterior area of the calcaneum  4  over substantially all of its height, as seen clearly in  FIG. 6 . 
         [0088]    The heel cup  24  may be made from a material that is elastically flexible but has some stiffness, for example a material based on carbon or a carbon-kevlar type composite material, or even a material based on certain high-density plastic materials. 
         [0089]    In contrast, the area of the cutouts  18  and  19 , occupied by the upper  25  and/or the vamp  26 , must have greater flexibility in order to authorize deformation upon movement of the sub-astragalus joint. 
         [0090]    During movement of the joint, and in particular eversion and inversion movements, the lateral cutouts  18  and  19  provide areas of preferential deformation of the shoe, oriented parallel to the sub-astragalus cone  12 . Nevertheless, the support of the relatively rigid connecting area  21   b  between the posterior tongue  21  and the lateral wings  22  and  23  produces an elastic return torque that tends to return the foot into the sagittal plane of the tibia, thereby relieving the sub-astragalus joint  11 . 
         [0091]    At the same time, the resulting heel cup  24  opposes rolling movements of the foot relative to the shoe itself during eversion and inversion movements, by virtue of the fact that the calcaneum  4  is closely enveloped by the heel cup  24 . This produces a significant improvement in comfort and greater safety in the event of extreme loads, in particular on turning. 
         [0092]    The invention applies to low shoes as shown in  FIG. 6 , i.e. shoes with a low vamp  26 . 
         [0093]    It applies equally to shoes with a higher vamp  26 , covering the tibio-tarsal joint  10 . 
         [0094]    It applies equally well to shoes with a flexible upper  25  and to shoes with a plantar shell and rigid vamp, provided that an area of greater flexibility is provided at the level of the cutouts  18  and  19 . 
         [0095]    For example, good results have been obtained with a shoe as shown in  FIG. 6  in which the heel cup  24  is a sheet of semi-rigid plastic material, for example polyurethane, ABS, polyethylene, having a thickness of the order of 1 mm. The heel cup  24 , fixed, for example glued, to the sole  2 , is preferably accommodated inside the external upper of the shoe and covered internally with protective layers of felt or other material appropriate for contact with the foot  1 . Alternatively, the heel cup  24  may constitute an external element, visible on the shoe. The sole  2  may have a conventional structure of polyurethane reinforced with carbon fibers, the upper  25  and the vamp  26  being produced from any deformable material, of the polymer type, or synthetic fabric, or leather, for example, the elasticity whereof may be varied as a function of the type of use. 
         [0096]    As a function of the intended use of the shoe, and in particular as a function of the required dynamic loads, uppers  25  and vamps  26  will be chosen that are more flexible if it is required to adapt the shoe to a use producing lower loads or more rigid if it is required to adapt the shoe to a use producing higher loads. 
         [0097]    Thus there may be expected a very significant reduction in the risk of injury by twisting of the foot and ankle joints during sports or even when walking. At the same time, comfort is considerably improved. 
         [0098]    The present invention is not limited to the embodiments that have been explicitly described and includes variants and generalizations thereof that fall within the scope of the following claims.