EP0552994B1 - Shoe, in particular a sports-shoe, comprising a spring located in the sole, enclosure and spring for such a shoe - Google Patents

Description

The invention relates to a shoe of the kind which comprises at least one spring, arranged in the sole between an upper plate and a lower plate to absorb impacts on the ground, the spring being disposed substantially vertically above the heel of the user, between the rigid upper plate and the lower plate close to the ground, and being constituted by at least one spring of the torsion spring type which comprises at least one winding with a substantially horizontal axis provided at each of its ends with a radial extension arm, the two extreme radial arms forming an angle between them, the winding being arranged so as to bear externally against one of the plates while the ends of the arms are in abutment against the other plate, l winding can approach or move away from the plate from which it is distant in a direction substantially orthogonal to this plate, while the angular difference between l he arm increases or decreases under the effect of the load applied to the spring.

The invention relates more particularly to such a shoe intended for sports activities but can also be applied to shoes such as city shoes.

US-A- 4,756,095 shows a shoe of this kind. According to this document, one of the arms of the spring is immobilized in translation, while the winding of the spring is in sliding contact against the respective plate. The production of such a shoe is relatively complex. In addition, at the beginning of the lowering of the sole portion, the spring does not exert a high reaction, which gives an impression of "soft" to the heel of the user.

The object of the invention is, above all, to provide a shoe of the kind defined above which responds better than so far to the various requirements of the practice and which no longer has, or to a lesser degree, the drawbacks mentioned above.

The invention also aims to provide a shoe which makes it possible to reduce the friction of the user's foot relative to the upper surrounding the foot, in particular in its rear part, despite the elasticity of the sole.

The invention also aims to provide a shoe in which one can put in place a spring of a particular type capable of fulfilling its role of shock absorber over a reduced vertical elastic stroke of approximately 6 to 7 mm.

The invention also aims to provide a shoe, the production of which is simple and the elastic means of which can be incorporated in a cassette capable of being slid into the sole of the shoe.

According to the invention, a shoe of the kind defined above is characterized in that the arms of the spring have substantially the same radial dimension, that the angle between the arms of the spring, in the rest position, is approximately 60 °. , the angle between an arm and the vertical being approximately 30 °, and the ends of the arms are in sliding contact against said other plate, means being further provided for holding the spring relative to the plate in the longitudinal direction and in the position where the axis of the windings is transverse.

Advantageously, the spring comprises two coaxial windings in opposite directions, separated from each other by a free space, the end arms located axially towards the outside of these windings being connected by a branch parallel to the axis of the springs. The inward arms are bent outward at their ends.

A transverse groove with a concave circular profile follows a part of the cylindrical surface of the windings, to hold the spring.

Advantageously, the height of the spring is approximately 18 mm when it is not subjected to a load and it is arranged so that, from the first millimeter of reduction in the overall height of the spring, the load undergone by this spring is about 35 daN.

The vertical elastic stroke of the spring is approximately 6 or 7 mm, the initial load then only having doubled.

Preferably, the shoe comprises a cassette of triangular prismatic shape constituted by a dihedron produced with two rigid plates articulated along the edge, the spring being disposed between the faces of this dihedron, this prismatic cassette being slid between an upper sole part and a bottom sole part of the shoe, the sole parts being connected at their periphery by a sort of bellows accepting variations in height of the prismatic cassette.

The edge of the cassette is advantageously located substantially at the level of the metatarsus of the user's foot, while the spring of the cassette is located under the heel region.

A cassette can also be located in front of the metatarsus of the user's foot, the edge of the cassette being slightly in front of the metatarsus of the foot, while the spring of the cassette is located under the toe of the shoe.

The shoe may include two cassettes arranged in opposite directions, one at the front, the other at the rear, the front cassette having dimensions smaller than those of the rear cassette.

The upper plate and the lower plate may have U-shaped cross sections turning their concavity towards each other, and the wings of which fit together to ensure relative lateral holding of the two plates.

The upper plate is rigid and is entirely located behind a transverse line intended to be located under the metatarsus of the user's foot; the sole has a transverse articulation zone at this line so that the angle formed between the plane of the rigid upper plate and the part of the sole located in front of the articulation zone can vary; the walls of the upper of the shoe which surround the foot of the user are fixed, at their lower part, to the rigid upper plate; the spring (s) is (are) located under the single zone of the rigid plate intended to be located under the heel of the user, the assembly being such that the variations of the load applied to the spring cause an oscillating movement of the rigid upper plate around the transverse line of articulation, relative to the lower plate.

Preferably, the rigid upper plate extends to the transverse line of articulation, which constitutes its front limit.

A layer of softer material may be provided under the lower surface of this rigid lower plate, to come into contact with the ground.

The rigid upper plate may have a surface limited to that of the heel of the shoe, while the lower plate has similar dimensions and is mounted with at least substantially vertical freedom in translation, relative to the upper plate

Advantageously, the spring is arranged to give, from the start of compression, a high load, which then only doubles, after a compression stroke of about 6 or 7 mm, so as to achieve good shock absorption.

Preferably, the cassette has a triangular prismatic shape constituted by a dihedron produced with two rigid plates articulated along the edge around a transverse axis, a spring being disposed between the faces of this dihedron; this cassette is intended to be slid between an upper sole part and a lower sole part of the shoe, the length of the cassette being such that the axis of articulation is, in normal use of the shoe, substantially under the metatarsus of the user's foot, while the spring is located substantially vertical to the user's heel.

The spring comprises at least one winding provided at each of its ends with a radial extension arm, the two extreme radial arms having substantially the same radial dimension and forming between them an angle of approximately 60 °, and it comprises two windings in opposite direction coaxial, separated from each other by a free space, the end arms located axially towards the outside of these windings being connected by a branch parallel to the axis of the springs, the winding being intended to be disposed in external support against a plate, while the ends of the arms are intended to come into sliding contact against another plate, the winding being able to approach or move away from the plate from which it is distant in a direction substantially orthogonal to this plate, while the angular difference between the arms increases or decreases, under the effect of the load.

The invention may include, within the scope of the claims, apart from the provisions set out above, a certain number of other provisions which will be more explicitly discussed below in connection with exemplary embodiments described with reference to the drawings attached, but which are in no way limiting.

Figure 1 of these drawings is a schematic view in longitudinal section, with parts outside, of a shoe according to the invention.

FIG. 2 is a perspective view, on a larger scale, of the spring disposed in the sole of the shoe of FIG. 1.

Figure 3 is an elevational view, on a larger scale, of the spring according to the invention.

Figure 4 shows the spring of Figure 3 in its crushed position.

Figure 5 is a schematic perspective view of a cassette intended to be introduced into the sole of a shoe.

Figure 6 is a cross section of the sole at the heel of a shoe according to the invention.

Figure 7 is a side view with parts in section of a shoe type city shoe according to the invention.

Figure 8 is a schematic perspective view of a detail of the shoe of Figure 6, on a larger scale.

Figure 9 shows, similarly to Figure 7, an alternative embodiment of a city shoe.

Figure 10 shows, similarly to Figure 9, another variant of a city shoe.

Figure 11 is a longitudinal vertical section of the heel of another variant of a city shoe.

FIG. 12 is a horizontal section, seen from above, of the heel of FIG. 11.

Figure 13, finally, is a schematic side view of another alternative embodiment of the shoe.

Before describing the shoe shown in Figure 1, it seems useful to make a few comments.

To absorb the shocks of the heel of a shoe on the ground, shocks which have repercussions on the ankles, knees and hips, it appeared desirable to obtain from the shoe a sufficient elastic stroke at the location of the heel.

• dans la marche à grandes enjambées, tout le poids du corps repose sur le talon ; la zone du métatarse du pied de l'utilisateur ne touche le sol qu'un moment après que le talon est entré en contact avec le sol ;
• dans la marche à petits pas, on peut considérer que le pied touche le sol à plat ; le métatarse et le talon se posent pratiquement en même temps avec prédominance du poids du corps sur le talon ;
• lors de la course à pied, il est recommandé de faire venir la partie avant du pied la première en contact avec le sol, puis le pied se déroule avec un léger retour à plat assurant une répartition des efforts et diminuant la fatigue.

We can classify the types of contact of the shoe with the ground in three main categories:

• in walking with long strides, the whole weight of the body rests on the heel; the metatarsal area of the user's foot does not touch the ground until a moment after the heel has come into contact with the ground;
• in walking with small steps, we can consider that the foot touches the ground flat; the metatarsus and the heel arise practically at the same time with predominance of the weight of the body on the heel;
• when running, it is recommended to bring the front part of the foot first into contact with the ground, then the foot unrolls with a slight flat return ensuring a distribution of efforts and reducing fatigue.

In order to best absorb the impact of the heel on the ground for the different types of contact mentioned above, as visible in FIG. 1, a shoe C, according to the invention, includes a spring R placed in the sole 1 between an upper plate 2 extending to the rear part of the shoe, and in particular under the heel of the user's foot F, and a lower plate 3. The plates 2 and 3 form an angle O between them.

The upper plate 2 is rigid, for example made of rigid plastic, having a low coefficient of friction. This plate 2 is located behind a transverse front limit L, constituted by a line perpendicular to the plane of Figure 1, located in the area intended to be located under the metatarsus 4 of the user's foot. In the embodiment of Figure 1, the rigid upper plate 2 extends to the limit L which constitutes its transverse front edge.

A transverse articulation zone 5 is provided, along the limit L, between the plate 2 and the front part 6 of the sole of the shoe which can be identical to the usual structure. In the exemplary embodiment of FIG. 1, the lower plate 3 is also rigid and extends to the limit L. The articulation 5 can comprise a transverse axis 7, for example metallic, engaged in bearings formed by ears provided on the lateral edges of the plates 2 and 3. In addition, the connection between the plate 2 and the front part 6 of the sole is ensured by a flexible strip 8. The plate 3 is linked to the front part 6, of preferably also by a flexible zone.

The upper 9 of the shoe, which envelops the foot F of the user, has its lower edges fixed on the periphery of the plate 2 and, towards the front, on the upper edge of the part 6.

The assembly of the plate 2 and the front part 6 of the sole is covered by an inner sole 10 of reduced thickness, relatively soft, extending over the entire length of the shoe, so that the foot of the user does not feel any roughness of the junction zones.

The spring R is of the torsion spring 11 type; it is arranged, substantially vertical to the heel of the user, between the rigid upper plate 2 and the lower plate 3 close to the ground.

As best seen in FIG. 2, the spring 11 comprises two coaxial windings 12, 13, in opposite directions, separated from each other by a free space 14.

Each winding 12, 13 comprises radial end arms 12 a , 12 b , 13 a , 13 b forming between them an angle A, and substantially of the same length.

The arms 12b, 13b are located at the outer ends of the springs 12, 13 and are mutually parallel while the arms 12a, 13a are located at the inner ends of the windings 12, 13, these two arms being parallel also. The outer arms 12b , 13b are connected, at their outer radial ends, by a branch 15 parallel to the axis of the windings.

The arms 12 a , 13 a located inwards are curved outwards, at their radial ends, along lugs 16 a , 16 b .

The spring 11 is arranged so that the windings 12, 13 bear externally against one of the plates, substantially along a generatrix. In the example considered, the windings 12, 13 are in abutment against the upper plate 2, while the branch 15 and the legs 16 a , 16 b are in abutment against the lower plate 3. The branch 15 and the legs 16 a , 16 b are in sliding contact against this plate 3, which is made of a material with low friction.

Means are provided for holding the spring 11 relative to the plate 2 in the longitudinal direction and in the position where the axis of the windings is transverse. These means can be constituted by a transverse groove 17 with a concave circular profile which comes to marry part of the cylindrical surface of the windings 12 and 13. The spring 11 is kept slightly compressed between the plates 2 and 3.

Of course, other means for holding the spring can be provided; these means need not interfere with the angular movement of the branches 12 a , 12 b and 13 a , 13 b when a load is applied to the plate 2 and causes the spring 11 to be crushed.

The space 18 located between the plates 2 and 3 and included between the articulation zone 5 and the spring 11 is free of any material so that the plate 2 can be angularly debated, relative to the plate 3, by oscillation around the articulation zone 5 during variations of the useful height H of the spring. This useful height H, as shown in Figure 3, is equal to the distance between the leg support plane 15 and the legs 16 a, 16 b and the plane parallel to this plane support externally tangent to the windings 12 , 13. Of course, the space 18 a located behind the spring 11 is also free of any material.

).Advantageously, the height H is approximately 18 mm when the spring 11 is not subjected to any load and the spring 11 is arranged so that, from the first millimeter of reduction in the height H, the load undergone, and therefore the reaction exerted by this spring, is around 35 daN. The spring 11 is also arranged so that the vertical elastic stroke, that is to say the reduction in height H is approximately 6 or 7 mm for doubling the vertical load which caused the first millimeter of reduction height. The angle A is advantageously chosen to be close to 60 ° at rest so that the angle between an extreme radial arm 12 a , 13 a or 12 b , 13 b and the vertical is approximately 30 ° ( $\frac{\text{AT}}{\text{2}}$

).

As can be seen in FIG. 3, the reaction forces exerted on the branch 15 and on the legs 16 a , 16 b in response to a vertical load V applied to the windings, create a torsional moment on said windings, the l amplitude depends on the lever arm d equal to the distance between the support zone of the arms on the plate 3, and the vertical passing through the axis of the windings 12, 13.

The length of the lever arm d is substantially proportional to $$\text{sin}\frac{\text{AT}}{\text{2}}\text{.}$$

The lever arm d increases when the compression of the spring occurs, at the same time as the action of the windings 12, 13 increases due to the increase in torsion. This increase in the length of the lever arm d mitigates the increase in the action of the windings.

de 30° au repos.With windings with an outside diameter of 10 mm and an initial height H of 18 mm, the lever arm d almost doubles in 6 mm compression, for an angle $\frac{\text{AT}}{\text{2}}$

30 ° at rest.

The outer contours of the plates 2 and 3 are connected by a flexible wall 19, similar to the wall of a bellows, capable of absorbing the oscillating movements of the plate 2 relative to the plate 3.

The lower plate 3 can be provided on its lower surface with a layer 20 of softer material, which also extends under the front part 6 of the shoe so as to constitute only a single ply.

As visible in FIG. 6, the plates 2 and 3 preferably have a U-shaped cross section turning their concavity towards each other. The concavity of the section of the upper plate 2 is turned downwards and the wings 21, 22 of this section, which are substantially vertical, are engaged between the wings 23, 24, facing upwards of the lower plate 3. Even when the spring 11 is not stressed, the lower edge of the wings 21, 22 is located below the upper edge of the wings 23, 24. Thus, in all operating conditions, good lateral resistance is ensured between the plates 2 and 3 by cooperation of the wings 21, 22 and wings 23, 24, the play between these wings being reduced.

The operation of the shoe of the invention immediately results from the foregoing explanations.

The spring 11 is calibrated so as to absorb, at the very start of its travel, for example in the first millimeter of reduction in the useful height H, a load corresponding substantially to half the weight of the user.

When the user walks or runs, there is a transfer of load from one foot to the other. The spring 11, associated with the foot on which the load is transferred will collapse so as to absorb this load; the plate 2 and the insole 10 will oscillate around the transverse articulation axis 5, the angle O decreasing.

When the load on the foot considered decreases, the spring 1 restores the absorbed energy and returns to its rest position.

It should be noted that the upper 9, by its lower edge, follows the movements of the plate 2 and that the foot F of the user is perfectly enclosed in the shoe and is integral with the upper 9, the insole 10 and the plate 2. It follows that during movements of the plate 2, there is no relative movement between the foot F of the user and the rod 9, which virtually eliminates any friction.

It would not be the same if the vertical elasticity was achieved inside the shoe which would cause friction from top to bottom and from bottom to top between the foot of the user, and more particularly the heel, and the inner part of the upper 9 of the shoe.

Furthermore, according to the invention, the tightening of the foot in the shoe by lacing, or equivalent means, remains the same during the vertical movements of the foot, while in a shoe where the vertical elasticity is produced inside the shoe, the tightening of the foot, in particular by lacing, varies constantly.

According to the invention, the movement of articulation of the foot takes place around the area of the metatarsus which corresponds to the natural area of articulation of the foot, the free space 18 of the sole allowing the plate 2 to oscillate in block.

The particular arrangement of the spring 11 of the torsion spring type, working by reducing its useful height due to the spacing of its radial end arms, is important.

Because the load, from the first millimeter of compression, towards the ground is approximately equal to half the weight of the user's body, the latter will be supported without vertical "softness" when the weight of his body is equally distributed on both feet, in station stopped. This high load of the spring, from the start of the compression movement, is decisive for allowing the spring to provide a significant return of energy.

Despite this high load, from the start, the spring only reaches, after 6 mm reduction in the working height H, twice the initial load.

In a conventional compression spring, the load reached after 6 mm of crushing would be substantially equal to six times the load obtained after 1 mm of crushing.

In addition, the torsion spring 11 of the invention, with double winding, occupies almost the entire width of the heel of the shoe, which contributes to good lateral stability, the axis of the winding being placed horizontally. In the case of conventional compression springs, several springs would be necessary.

It can also be noted that the shoes which provide, as means of cushioning in the heel, flexible materials, of the elastomer or equivalent material type, are very soft at the start of the crushing, hence a lack of lateral stability, and harden then very quickly at the end of the crushing.

= 30°) au repos, avec possibilité de venir jusqu'à 90° ( $\frac{\text{A}}{\text{2}}$

= 90°) en fin d'écrasement, de bons résultats ont été obtenus avec des fils d'acier inox de diamètre de 2,4 mm.For walking and running, given the rapid heel / foot flat / forefoot or front foot / flat foot / heel winding, the hardnesses of the spring 11 must be well adapted but not too strong, because the amortization must be done very gradually, without encountering hard points. With springs whose outside diameter of the windings was 10 mm, the useful height H at rest of 19 mm and the arms open at 30 ° ( $\frac{\text{AT}}{\text{2}}$

= 30 °) at rest, with the possibility of coming up to 90 ° ( $\frac{\text{AT}}{\text{2}}$

= 90 °) at the end of the crushing, good results were obtained with stainless steel wires with a diameter of 2.4 mm.

For sports in which relatively frequent jumps are involved, harder springs can be provided.

Referring to FIG. 5, it can be seen that the spring 11 can be placed in a cassette 25, substantially in the form of a triangular or wedge prism, constituted by a dihedron produced with two rigid plates 102, 103. The plates 102, 103 form the faces of a dihedral and are articulated along the edge of the dihedral around a transverse axis 7, constituted for example by a metal rod 26.

The axis 26 is intended to be located substantially under the metatarsus 4 of the foot of the user, while the spring 11 is disposed between the faces 102, 103 of the dihedral backwards where it is held by any suitable means.

More specifically, the upper plate 102 has a U-shaped cross section turning its concavity downward, as shown in FIG. 6, and comprising lateral wings 104, 105 extending downward, substantially in a vertical plane.

The lower plate 103 also has a U-shaped cross section turning its concavity upwards and limited, on the sides, by vertical lateral wings 106, 107 situated inside the wings 104, 105, with reduced play. . The cooperation between the lateral wings of the plates 102 and 103 ensures transverse maintenance of one plate relative to the other.

As visible in FIG. 5, the lateral wings 104, 105 of the upper plate comprise, at their front end, an ear such as 27 framing a notch provided in the front edge of the upper plate 102. Each ear 27 has a hole serving bearing at the ends of axis 26.

The lower plate 103 comprises a cylindrical sleeve 28 forming its front transverse edge, disposed between the ears 27. This sleeve 28 has a central bore traversed by the axis 26.

A retaining lug 29 is provided at the rear of the plate 103 to cooperate with a stop provided on the rear face of the plate 102 and to keep the cassette 25 closed at rest, the spring 11 being prestressed by 1 mm. The assembly is such that even when the cassette is not stressed by a load, the side walls 104, 105 and 106, 107 overlap along a range.

The plates 102 and 103 are made of a rigid plastic material, with a reduced coefficient of friction.

The space 118 located between the axis 26 and the spring 11 of the cassette 25 is free of material like the space 18 of FIG. 1.

This cassette 25 is intended to be slid, in the manner of a wedge, between an upper sole part and a lower sole part of a shoe, the upper and lower sole parts having a flexible zone at the metatarsus of the user's foot, area in which the hinge pin 26 of the cassette will be located. The lower and upper sole portions of the shoe are connected at their periphery by a sort of bellows similar to the bellows 19 of FIG. 1. The fixing of this bellows to the outer edges of the lower and upper sole portions can be removably provided so that the cassette 25 can be replaced by another cassette of the same type but whose spring has a different rigidity. As a variant, the cassette can be put in place from below or from inside the shoe.

This change of cassette makes it possible to best adapt the shoe to the requirements of use depending on whether the shoe will be used, for example, on a particular day for a walk or on another day for a course involving relatively frequent jumps.

Of course, the upper 9 of the shoe has its lower edge fixed on the upper sole part so that during the crushing movements of the spring, there is no relative movement between the upper 9 and the foot of the user.

The upper sole part can comprise the plate 2 described with reference to FIGS. 1 to 3, and which is represented in FIG. 6, while the lower sole part can comprise the plate 3, also represented in FIG. 6. The faces external of the wings 104 and 105 of the plate 102 of the cassette are, practically, in contact with the internal faces of the wings 21, 22 of the plate 2.

Due to the fact that the plates 102, 103 of the cassette are rigid, it is however possible to remove the rigid plates 2 and 3 from the sole of the shoe; in such a case, the upper sole part and the lower sole part are made entirely of a flexible material.

A shoe fitted with such a cassette works as explained above, and has the same advantages as those mentioned in connection with FIGS. 1 to 3.

The description given so far rather relates to a sports shoe such as a shoe for walking, running or tennis, the lower surface of the sole of which is practically flat, without prominence at the heel.

As illustrated in FIG. 7, a shoe C according to the invention, can be of the city shoe type with a prominent heel 30, protruding downwards while the sole 201, flexible in particular in the zone 205 located under the metatarsus away from the ground from this area to the upper level of the heel at the back. There is therefore a free space 218 between the articulation zone 205 and the heel.

In the case of FIG. 7, the rigid upper plate 202 has an area limited substantially to that of the heel. It extends to the rear of the shoe but, towards the front, is limited by a transverse edge 31 situated behind the articulation zone 205.

The plate 202 has, at its periphery, a substantially vertical wall 222 extending downward. The lower plate 203 is also rigid and is mounted with a possibility of vertical translation relative to the plate 202. Lateral support and vertical guidance is ensured between the plates 202 and 203 by virtue of vertical walls 224 provided on the edges of the plate 203, and extending upwards, which cooperate with the wall 222.

The connection between the upper plate 202 and the lower plate 203 can be ensured by transverse pins 32 (FIG. 8) projecting transversely inwards, from the side walls 224, these pins 32 being engaged in vertical oblong openings 33 provided in the wall 222 of the plate 202. The pins 32 thus allow a relative oscillation between the plates 202 and 203 around a transverse axis and, moreover, a displacement in substantially vertical translation between these plates.

The spring 11 is disposed between the plate 202 and the plate 203, substantially vertical to the heel of the user, this spring 11 being held by any suitable means.

The plates 202, 203, when the shoe is not stressed, are separated as far as possible by the spring 11, the pins 32 being in abutment against the lower end of the openings 33.

The walls 222 and 224 are arranged to allow sufficient freedom in vertical translation while remaining engaged with one another when no load is exerted on the heel of the shoe.

The operation of a shoe according to Figure 7 is similar to that described with reference to the previous figures.

FIG. 9 shows an alternative embodiment of the city shoe of FIG. 7. The rigid upper plate 302 is limited by a flange 331 which comes to surround a flange 34 of the lower plate 303. The flanges 331 and 34, in their part transverse, have a shape curved, cylindrical, the horizontal axis of which is in the vicinity of the flexion region 305 of the sole. The spring 11 is housed between the plates 302, 303, the extent of which is limited to the area of the heel. There is a free space 318 between the zone 305 and the heel, so that the foot is not in too great contact on the front of the cassette. A sort of bellows 319 surrounds all of the plates 302, 303.

FIG. 10 illustrates a variant of a city shoe comprising, housed in the heel, a cassette 425, similar to the cassette of FIG. 5, but of shorter length. The hinge pin 426 is located in the area of the front edge of the heel, the spring 11 being towards the rear. The cassette 425 is disposed between an upper plate 402 and a rigid lower plate 403. The assembly is surrounded by a sort of bellows 419. We find the flexion zone 405 at the level of the metatarsus and the free space 418.

Figures 11 and 12 illustrate another alternative embodiment of the heel of a shoe.

The rigid upper plate 502 is placed against the upper wall 35 of an envelope 36 integral with the sole and comprising a vertical peripheral wall 37 directed downwards. The plate 502 is provided with a vertical rim 531 on its contour, with the exception of its front transverse edge.

The bottom plate 503, rigid, made of hard material like the plate 502, forms a sort of overturned cover with its rim 534 turned upwards, situated inside the wall 37 and the rim 531. The plate 503 can move , substantially vertically, relative to the plate 502. A stud 38 is provided projecting on each side, at the front and at the top of the longitudinal parts of the rim 534. Each stud 38 is received in a vertical groove 39 provided on the internal wall rim 534, and closed down. The plate 503 has at the rear, at the top of its rim, a lug 40 projecting rearwards, also received in a groove or window 41, closed downwards, from the rim 534.

The spring 11 is disposed between the plates 502 and 503 in a manner similar to that described above.

FIG. 13 shows a shoe whose sole has a cassette 625 a similar to the cassette 25 in FIG. 6, but moreover short, located in front of the metatarsus of the user's foot and arranged in the opposite direction. In other words, the edge of the cassette 625 a is located slightly in front of the metatarsus, while the spring of the cassette 625 a is located under the toe of the shoe. The vertical elastic stroke of the spring of the cassette 625 a is smaller than that of the spring associated with the heel; this stroke is, for example, 3 or 4 mm.

This cassette 625 a can be combined with a second cassette 625 b , arranged like the cassette 25 in FIGS. 5 and 6, that is to say with its edge forwards and its spring under the heel. The cassette spring 625 b has a travel of 6 to 7 mm.

As a variant, the cassette 625 a can be combined with a rear sole part similar to that of FIG. 1.

Whatever the embodiment, a shoe according to the invention remains simple to manufacture while ensuring good shock absorption of the heel on the ground with an optimal restitution of the energy stored during the impact. The friction between the foot and the upper of the shoe, especially at the heel, is eliminated despite the elasticity introduced at the heel.

Claims (18)

1. A shoe comprising at least one spring (R) disposed in the sole between an upper plate (2, 102, 202, 302, 402, 502) and a lower plate (3, 103, 203, 303, 403, 503) for absorbing the impacts on the ground, the spring (R) being disposed substantially in the vertical direction of the user's heel, between the rigid upper plate (2, 102, 202, 302, 402, 502) and the lower plate (3, 103, 203, 303, 403, 502) close to the ground, and being constituted by at least one spring (11) of the torsion spring type which comprises at least one coil (12, 13) with a substantially horizontal axis, provided at each of its ends with a radial extension arm (12a, 12b; 13a, 13b), the two radial end arms (12a, 12b; 13a, 13b), forming between them an angle (A), the coil being disposed so as to bear externally against one of the plates (2, 102, 202, 302, 402, 502; 3, 103, 203, 303, 403, 503), while the ends of the arms (12a, 12b; 13a, 13b) bear against the other plate (3, 103, 203, 303, 403, 503; 2, 102, 202, 302, 402, 502), the coil being capable of coming closer to, or moving away from the plate from which it is spaced along a direction that is substantially orthogonal to this plate, while the angular interspacing between the arms increases or decreases under the effect of the load applied to the spring, characterized in that the arms of the spring (12a, 12b; 13a, 13b) have substantially the same radial dimension, that the angle (A) between the arms of the spring is approximately 60° in the rest position, the angle between one arm and the vertical being approximately 30°, and that the ends of the arms (12a, 12b; 13a, 13b) are in a sliding bearing contact with the said other plate (3, 103, 203, 303, 403, 503; 2, 102, 202, 302, 402, 502), means being moreover provided for keeping the spring (11) relative to the plate (2, 102, 202, 302, 402, 502; 3, 103, 203, 403, 503) along the longitudinal direction and in the position where the axis of the coil is transverse.
2. A shoe according to claim 1, characterized in that the spring comprises two coils (12, 13) in opposite coaxial directions, separated from each other by a free space (14), the end arms (12b, 13b) situated axially towards the outside of these coils, being connected by a leg (15) parallel to the axis of the springs.
3. A shoe according to claim 2, characterized in that the arms (12a, 13a) situated towards the inside are bent towards the outside at their ends (16a, 16b)
4. A shoe according to one of claims 1 to 3, characterized in that a transverse groove (17) with a concave circular profile comes to follow a portion of the cylindrical surface of the coils (12, 13) to keep the spring in position.
5. A shoe according to one of the preceding claims, characterized in that the height of the spring is approximately 18 mm when it is not subjected to a load, and that it is arranged so that when the overall height of the spring is reduced by the first millimetre, the load sustained by this spring will be approximately 35daN.
6. A shoe according to claim 5, characterized in that the vertical elastic travel of the spring is approximately 6 or 7 mm, the initial load then being only doubled.
7. A shoe according to any one of the preceding claims, characterized in that it comprises a cassette (25, 625a, 625b) of a triangular prismatic shape, constituted by a dihedron obtained by two rigid plates (102, 103) articulated along the edge, the spring (R, 11) being disposed between the faces of this dihedron, this prismatic cassette (25) being slipped in between a portion of the upper sole and a portion of the lower sole, the sole portions being joined at their periphery by a kind of bellows (19) which accepts the variations in height of the prismatic cassette.
8. A shoe according to claim 7, characterized in that the edge of the cassette (25, 625b) is situated substantially in the region of the metatarsal (4) of the user's foot, while the spring of the cassette (R, 11) is situated under the region of the heel.
9. A shoe according to claim 7, characterized in that the cassette (625a) is situated ahead of the metatarsal of the user's foot, the edge of the cassette being situated slightly ahead of the metatarsal of the foot, while the spring of the cassette is situated beneath the point of the shoe.
10. A shoe according to one of claims 7 to 9, characterized in that it comprises two cassettes (625a, 625b) disposed in opposite directions one at the front, the other at the rear, the front cassette having smaller dimensions than those of the rear cassette.
11. A shoe according to any one of the preceding claims, characterized in that the upper plate (2, 102, 202, 302, 402, 502) and the lower plate (3, 103, 203, 303, 403, 503) have U-shaped cross-sections, their concavity turning towards each other, and whose sides (21, 22; 23, 24) fit into one another to ensure a relative lateral hold of the two plates.
12. A shoe according to any one of the preceding claims, characterized in that : the upper plate (2, 102, 202, 302, 402, 502) is rigid and entirely situated behind a transverse line (L) intended to be located under the metatarsal (4) of the user's foot; the sole has a transverse articulation zone (5) in the region of this line (L), so that the angle formed between the plane of the rigid upper plate (2, 102, 202, 302, 402, 502) and the portion (6) of the sole situated ahead of the articulation zone can vary; the walls of the side (9) of the shoe which surround the user's foot are fixed at their lower portion to the rigid upper plate (2, 102, 202, 302, 402, 502); the spring or springs (R, 11) is (or are) situated beneath the only zone of the rigid plate intended to be located under the user's heel, the whole set being such that the variations of the load applied to the spring (R, 11) entail an oscillating movement of the rigid upper plate (2, 102, 202, 302, 402, 502) round the transverse articulation line (L), relative to the lower plate (3, 103, 203, 303, 403, 503).
13. A shoe according to claim 12, characterized in that the rigid upper plate (2, 102) extends as far as the transverse articulation line (L) which constitutes its front limit.
14. A shoe according to one of claims 12 or 13, characterized in that the lower plate (3, 103, 203, 303, 403, 503) is rigid and that a layer (20) of a more flexible material is provided under the lower surface of this rigid plate (3, 103, 203, 303, 403, 503) so as to come into contact with the ground.
15. A shoe according to claim 12, characterized in that the rigid upper plate (202, 302, 402, 502) has a surface that is limited to the heel of the shoe, while the lower plate (203, 303, 403, 503) has similar dimensions and is mounted with scope for at least a substantially vertical translation relative to the upper plate (202, 302, 402, 502).
16. A shoe according to one of claims 12 to 15, characterized in that the spring (11) is arranged to provide at the start of the compression a high loading which will subsequently only double, after a compression travel of approximately 6 or 7 mm, so as to obtain a good absorption of the impacts.
17. A cassette intended to be slipped in between an upper sole portion and a lower sole portion of a shoe according to one of claims 7 to 11, the said cassette (25, 625b) having a triangular prismatic shape constituted by a dihedron obtained by two rigid plates (102, 103) articulated along the edge round a transverse pin (26), a spring (R, 11) being disposed between the faces of this dihedron, the length of the cassette being such that the articulation pin is located during normal use of the shoe substantially under the metatarsal of the user's foot, while the spring (R, 11) is located substantially in the vertical direction of the user's heel.
18. A spring for a shoe sole, comprising at least one coil (12, 13) provided at each of its ends with an axial extension arm (12a, 12b; 13a, 13b), characterized in that the two radial end arms have substantially the same radial dimension, and form between them an angle (A) of approximately 60°, and that it comprises two coaxial coils (12, 13) with reverse directions, separated from each other by a free space (14), the end arms (12b, 13b) situated axially towards the outside of these coils, being connected by a leg (15) parallel to the axis of the springs, the coil being intended to be disposed to bear externally against a plate, while the ends of the arms are intended to come into a sliding bearing contact with another plate, the coil being capable of coming closer to, or moving away from the plate from which it is interspaced along a substantially orthogonal direction to this plate, while the angular interspacing between the arms increases or decreases under the effect of the load.

Images