EP1249184B1 - Reinforcement for sportshoe - Google Patents

Abstract

In median and rear zones (B, C) a sandwich structure is employed, comprising a core (12) with two skins (11, 13). In the leading zone (A) it is flexible in the longitudinal direction and stiff in torsion.

Description

The field of the invention is that of shoes intended to cooperate with a cross-country ski, according to a movement in which, the tip of the shoe being secured to the machine, the heel is movable between a position resting on the machine and a raised position with respect to said craft.
This movement of the foot is the one found especially in cross-country skiing practices in so-called "non-alternative" or "no skater" evolutions.These modes of evolution also exist for sports gear of the type cross-country skiing on wheels.

The essential qualities sought for shoes adapted to this kind of movement, are rigidity in the transverse direction (high torsional stiffness) combined with longitudinal flexibility, especially in the metatarsophalangeal zone (low longitudinal stiffness).

The present invention thus relates more precisely to a reinforcement aimed at improving the mechanical qualities mentioned above.

Such a reinforcement is advantageously intended to be a constituent element of the lower part of the cross-country ski boot. By way of example, such a lower part conventionally comprises an outsole intended to cooperate with the sports vehicle, a first assembly, and an insole. This lower part is assembled with the upper part of the shoe which comprises in particular a vamp, and possibly a rod. The lower edge of the upper is usually sewn and / or glued and / or welded with the outsole, as well as with the mounting first. There are also other modes of assembly, in particular by the so-called "strobel" technique.

It is indeed important that the cross-country ski boots, be rigid or stiff in torsion with respect to the longitudinal axis of the shoe. This ensures a good stability of the shoe, this torsional stiffness to ensure optimal guidance of the ski by the shoe.

In addition, the flexibility in the longitudinal direction of the sole of the shoe is desirable for walking and proves essential during the evolution in "no alternative". The foot and the shoe must be able to wrap and unfold easily and harmoniously with respect to the fixed front tip of the shoe.

The foot and the upper and lower parts (sole) of the shoe are flexed during almost all sports activities. In practice and in the sense of this presentation, we speak of flexion to evoke that which intervenes in the movement at the level of the metatarsophalangeal joint. The shoe must, in its design, perfectly respect the positioning of this joint which makes an angle of about 71/72 ° with the internal tangent to the foot, and which is along the same tangent at about 73/74% of the total length of the foot.

To promote flexion, it is customary to use reinforcements integrating in the upper part (upper / upper) or in the lower part (sole of the boot).

In addition to the mechanical properties of torsional stiffness and flexibility in longitudinal flexion along the metatarsophalangeal axis, other parameters must be taken into account, including: lightness, cost, industrial feasibility ...

With regard to the reinforcements which are more specifically of interest in the context of the present invention, there are a number of prior technical proposals which, until now, have not been entirely satisfactory.

U.S. Patent No. 5,406,723 relates to a cycling shoe sole having a multilayer structure. The latter is supposed to give the cycling shoe sufficient longitudinal rigidity so that it can withstand the force of curvature which is exerted on the sole of the shoe during pedaling, while satisfying a constraint of lightness oh so important to relieve the cyclist's efforts. The multilayer structure of this shoe sole is constituted by a polyurethane foam core interposed between two skins each consisting of a plurality of composite layers based on glass fibers or carbon embedded in a matrix of crosslinked polymer resin (phenolic resin) . It is clear that such a sandwich reinforcement for shoe outsole cycling, has a flexural stiffness such that it prohibits virtually any longitudinal flexion movement. This is precisely what is sought. Therefore, such a reinforcement is properly unsuitable for shoes intended to allow a rolled / unrolled movement of the shoe.

EP No. 0 931 470 discloses a sports shoe comprising a stiffening element integrated in the lower part (sole of the shoe). This stiffening element is an inner or outer sole or an internal sandwich-type reinforcement comprising a core 15 made of expanded plastic foam (light wood, vertical plastic cylinders or honeycomb), this core being inserted between two skins 13 and 14 based on polymer (nylon, polyurethane, polypropylene), resin or composite material comprising synthetic resins in which are included carbon fibers, aramid, or glass. The rigidity of the skins 13 and 14 is greater than that of the core 15. The thickness of the latter is greater than that of the skins 13 and 14. It can be seen from FIG. 5 and text column 3 lines 41 to 53 of FIG. EP 0 931 470 that the stiffening element may comprise parts of variable section and of different flexibilities, in particular having a greater longitudinal flexibility on the forefoot. Such a sole construction, however, remains essentially rigid and is not suitable for sports requiring a course of the foot such as cross-country skiing, race, etc ... Moreover, the EP No. 0 931 470 aims essentially a application to shoes with a rigid sole, such as a bike, mountain shoe, etc.

French Patent No. 2,600,868 (86,10130) relates to a cross-country ski boot sole that is torsionally stiff and flexible in the longitudinal direction. This sole comprises a reinforcement located at least in the metatarsophalangeal region and corresponding to a first assembly consisting of a composite sheet (carbon or aramid glass fibers embedded in epoxy or polyester resins). This composite sheet has the characteristic of having fibers oriented in two or three directions relative to the longitudinal axis of the sole (polydirectional fabric). This is intended to obtain the desired stiffness in the transverse longitudinal direction and in torsion. There is no question of sandwich structure in this reinforcement. Furthermore, this shoe sole remains perfectible with regard to the transverse stiffness and therefore the skiing behavior, the flexibility, the durability, the lightness, the efficiency, the regularity and the sensitivity of the rolled / unrolled movement and the protection of the foot during flexions.

French Patent Application No. 2,682,011 (91 12376) relates to a cross-country ski boot whose torsional stiffness and longitudinal flexibility in the metatarsophalangeal zone are improved and which comprises an outer sole covered by a first internal mounting defining between them a peripheral assembly area called mounting socket, for securing the rod and the upper with the lower part of the shoe. The outsole has torsional stiffness properties and is mounted in combination with the mounting first made of a flexible bending material (rubber) in an area corresponding to the forefoot part. The first assembly is also made of leather or cellulose fibers in its anterior end region corresponding to the phalanges area, while the rear part is made for example of cardboard.
It is not used in the assembly according to FR 2 682 011 to a sandwich structure and it has been found that the torsional stiffness, and therefore the control of the ski, remain perfectible. In addition, this shoe could also be improved in terms of yield optimization, which results from the spring effect in this area of the metatarsophalangeal flexion axis.
Finally, the materials used in the first assembly of this shoe do not have all the desirable guarantees in terms of stability of mechanical properties over time.

• augmenter la raideur en torsion de façon à améliorer la conduite et le contrôle de l'engin de sport, tout en optimisant l'aptitude à la flexion dans la zone métatarsophalangienne, de façon à permettre un mouvement d'enroulé/déroulé régulier et souple de la chaussure et de façon à permettre en outre de percevoir les réactions de l'engin de sport et du sol et donc de doser les efforts ;
• à améliorer le rendement de la chaussure en optimisant l'effet ressort dans la zone métatarsophalangienne, sans nuire à la flexibilité, ni à la raideur en torsion ;
• à mettre en oeuvre des matériaux répondant aux spécifications mécaniques évoquées ci-dessus, et aptes à conserver lesdites propriétés ou qualités et donc les comportements subséquents, de manière prolongée dans le temps (dégradation lente - augmentation de la durabilité) ;
• à gagner encore du poids sur la chaussure ;
• à protéger le pied lors des flexions en minimisant les contraintes en compression subies par le pied ;
• à maintenir le coût de revient dans des limites acceptables ;
• à développer un renfort qui soit aisément fabriquable au niveau industriel.

It must therefore be noted that the previous technical proposals are not completely satisfactory or are unsuitable for solving the technical problem or problems consisting of:

• increase the torsional stiffness so as to improve the driving and control of the sports machine, while optimizing the bending ability in the metatarsophalangeal area, so as to allow a smooth and flexible rolling / unwinding movement of the shoe and so as to also allow to perceive the reactions of the sports vehicle and the ground and thus to dose the efforts;
• to improve the performance of the shoe by optimizing the spring effect in the metatarsophalangeal zone, without impairing flexibility or torsional stiffness;
• to implement materials meeting the mechanical specifications mentioned above, and able to retain said properties or qualities and therefore the subsequent behaviors, of prolonged in time (slow degradation - increased sustainability);
• to gain even more weight on the shoe;
• protecting the foot during bending by minimizing the compressive stresses to the foot;
• to keep the cost price within acceptable limits;
• to develop a reinforcement that is easily manufactured at the industrial level.

One of the objectives of the present invention is to provide a shoe reinforcement, in particular sports boot (e.g. cross-country ski), which provides significant advances in particular with regard to the technical specifications stated above.

Another object of the invention is to provide a cross-country ski boot reinforcement enabling the improvement of ski riding performance, durability, flexibility, weight gain, cost, protection of the ski, foot, industrial feasibility.

Another object of the present invention is to provide a shoe, especially sports and especially cross-country ski, comprising a reinforcement in the sole assembly to best meet the specifications mentioned above.

These objectives among others, are achieved by the present invention which firstly relates to a shoe reinforcement as defined in claim 1.

According to the invention, the choice of a material having a sandwich structure at least in the rear zone C corresponding to the heel and in the zone B corresponding to the arch, contributes to obtaining the desired results in terms of longitudinal flexibility and of torsional stiffness in the anterior metatarsophalangeal area. The same goes for the performance of the shoe (spring effect in zone A), the driving of the ski, the durability, the lightness, the ease and the precision of the rolled / unrolled movement of the foot and of the shoe, as well as the protection of the foot during flexions.

The present invention also relates to a bottom shoe, comprising the reinforcement as defined in claim 1.

The invention will be better understood in the light of the following description of a non-limiting example of a preferred embodiment of the reinforcement and the shoe considered.

• la figure 1 est une vue en perspective d'une chaussure de ski de fond, selon l'invention, fixée de manière réversible par sa pointe antérieure sur un ski de fond et soulevée par rapport audit ski de fond selon un mouvement d'enroulé par flexion;
• la figure 2 est une vue en coupe transversale de la chaussure et du ski représentés à la figure 1;
• les figures 4A et 4B montrent respectivement en vue de dessous et de côté la semelle externe de la chaussure représentée aux figures 1 et 2;
• les figures 5A et 5B montrent respectivement en vue de dessous et de côté la première de montage apparaissant sur la figure 2;
• la figure 6 est une représentation schématique en coupe longitudinale d'un premier mode de réalisation du renfort non couvert par les revendications;
• la figure 7 est une représentation schématique en coupe longitudinale d'un mode de réalisation du renfort selon l'invention;
• la figure 8 est une représentation schématique en coupe longitudinale d'un autre mode de réalisation du renfort selon l'invention;
• la figure 9 est une représentation schématique en coupe longitudinale d'un mode de réalisation du renfort non couvert par les revendications;
• la figure 10 est une représentation schématique en coupe longitudinale d'un mode de réalisation du renfort non couvert par les revendications;
• la figure 11 est une vue de dessous d'une première de montage semblable à celle représentée à la figure 5A, avec arrachement partiel dans la zone antérieure A, d'un premier exemple de fabrication de la nappe fibreuse du renfort selon l'invention;
• la figure 12 est une vue de dessous d'une première de montage semblable à celle représentée à la figure 5A, avec arrachement partiel dans la zone antérieure A, d'un deuxième exemple de fabrication de la nappe fibreuse du renfort selon l'invention.

This description is made with reference to the appended drawings in which:

• FIG. 1 is a perspective view of a cross-country ski boot, according to the invention, reversibly fixed by its anterior tip on a cross-country ski and lifted with respect to said cross-country ski in a wound movement by flexion;
• Figure 2 is a cross-sectional view of the shoe and the ski shown in Figure 1;
• Figures 4A and 4B respectively show in bottom view and side the outer sole of the shoe shown in Figures 1 and 2;
• FIGS. 5A and 5B respectively show, in bottom view and on the side, the first assembly appearing in FIG. 2;
• Figure 6 is a schematic representation in longitudinal section of a first embodiment of the reinforcement not covered by the claims;
• Figure 7 is a schematic representation in longitudinal section of an embodiment of the reinforcement according to the invention;
• Figure 8 is a schematic representation in longitudinal section of another embodiment of the reinforcement according to the invention;
• Figure 9 is a schematic representation in longitudinal section of an embodiment of the reinforcement not covered by the claims;
• Figure 10 is a schematic representation in longitudinal section of an embodiment of the reinforcement not covered by the claims;
• Figure 11 is a bottom view of a mounting first similar to that shown in Figure 5A, partially cut away in the front area A of a first example of manufacture of the fibrous web of the reinforcement according to the invention;
• Figure 12 is a bottom view of a mounting first similar to that shown in Figure 5A, partially cut away in the front area A of a second example of manufacture of the fibrous web of the reinforcement according to the invention.

The invention relates to a cross-country ski boot reinforcement, designated 1 in the drawings. This cross-country ski boot 1 is reversibly fixed by its front end to a cross-country ski 2 equipped with a binding 3. The foot and the ankle taking place in the boot 1 are symbolized in this FIG. 1 and are designated by the common reference 4. The boot 1 comprises an outer sole 5 and a vamp / upper 6. The boot 1 is shown in the raised position of the heel relative to the ski 2.

FIG. 2 shows the boot 1 in a bearing position on the upper surface of the ski-down 2. As can be seen in FIGS. 1, 2 and 4A, the outer sole 5 of the boot 1 has a longitudinal groove 7 designed to cooperate with a guide rib 8 secured to the upper surface of the ski 2. The groove 7 and the rib 8 have complementary trapezoidal cross-sections. The guide groove 7 of the outer sole 5 is partly defined by two parallel longitudinal members 18 having in their front portion transverse grooves 12 intended to improve the flexural flexibility of the sole without compromising their torsional rigidity (FIG. ).

The shoe 1 and the foot 4 move from the unwound position bearing on the ski of FIG. 2, to the wound position (raised) of FIG. 1, by bending around the metatarsophalangeal flexion axis shown in FIG. 11 and designated by the reference α.

As can be seen from FIG. 2, the lower part or sole of the boot 1 comprises the outer sole 5 on which the first mounting 9 rests, surmounted by an inner sole 10, and secured to the upper part of the boot constituted by the upper / stem 6, by means of a connection by stitching and / or welding and / or bonding of the lower edge of the upper 6, which in this case is interposed between the first mounting 9 and the outer sole 5 .

• semelle interne 10 représentée sur les figures 2 et 3,
• première de montage 9 représentée sur les figures 2, 5A et 5B,
• et semelle externe 5 représentée aux figures 2, 4A et 4B.

Selon une variante, le renfort constitue intégralement l'un desdits éléments constitutifs 5, 9, 10.According to the invention, the reinforcement is integrated in at least one of the constituent elements 5, 9, 10 of the lower part of the boot 1, namely:

• inner sole 10 shown in Figures 2 and 3,
• first mounting 9 shown in Figures 2, 5A and 5B,
• and outsole 5 shown in Figures 2, 4A and 4B.

According to one variant, the reinforcement constitutes integrally one of said constituent elements 5, 9, 10.

• la zone A antérieure s'étendant de part et d'autre de l'axe de flexion métatarsophalangienne α tel que représenté sur la figure 11 et correspondant au positionnement de l'articulation métatarsophalangienne, qui fait un angle d'environ 71/72° avec la tangente interne T au pied et qui se situe le long de cette même tangente à environ 73/74% de la longueur totale du pied à partir de l'extrémité postérieure P.
• la zone B médiane s'étendant de la limite postérieure L_A de la zone A correspondant à l'avant de la voûte plantaire jusqu'à l'arrière de la voûte plantaire.
• la zone C postérieure s'étendant de la limite postérieure L_B de la zone B jusqu'à l'extrémité du talon.

The shoe reinforcement considered here is symbolically divided into three zones by reference to the anatomy of the foot, namely:

• the anterior zone A extending on either side of the metatarsophalangeal flexion axis α as represented in FIG. 11 and corresponding to the positioning of the metatarsophalangeal joint, which makes an angle of approximately 71/72 ° with the internal tangent T at the foot and which is along the same tangent at approximately 73/74% of the total length of the foot from the posterior end P.
• the median zone B extending from the posterior limit L _A of the zone A corresponding to the front of the arch to the back of the arch.
• the posterior zone C extending from the posterior limit L _B of the zone B to the end of the heel.

FIG. 5B shows diagrammatically the dotted foot 4, and zones A, B and C have been defined with reference to the anatomy of the foot.
The reinforcement according to the invention can be divided into three zones A, B, C indicated in FIGS. 3, 4A, 4B, 5A, 5B.
The same applies to FIGS. 7 and 8, which diagrammatically represent two different embodiments of the reinforcement according to the invention and which show the sandwich structure specific to zones B and C.

This sandwich structure comprises two skins 11 and 13 respectively upper and lower between which is interposed a core 12. The nature of the constituent materials of the skins 11 and 13 and the core 12 in the two embodiments of Figures 7 and 8 will be detailed below.

According to an advantageous characteristic of the invention, the shoe reinforcement to which it relates can be characterized by the stiffness in longitudinal flexion RfA, RfB, RfC of the zones A, B, C.

Thus, according to a preferred arrangement of the invention, each zone A, B, C has a stiffness in longitudinal flexion RfA, RfB, RfC, such that: $$\mathrm{R}\mathrm{f}\mathrm{AT}<\mathrm{R}\mathrm{f}\mathrm{B}\le \mathrm{R}\mathrm{f}\mathrm{VS}$$

• la zone A présente une raideur RfA constante ou progressive de l'avant vers l'arrière,
• la zone B présente une raideur RfB constante ou progressive de l'avant vers l'arrière,
• la zone C présente une raideur RfC constante ou progressive de l'avant vers l'arrière.

More preferably still:

• zone A has constant or progressive stiffness RfA from front to rear,
• zone B has constant or progressive RfB stiffness from front to rear,
• zone C has constant or progressive stiffness RfC from front to rear.

avec:

• RfA constante
• RfB progressive de l'avant vers l'arrière
• RfC progressive de l'avant vers l'arrière.

Dans ce mode de réalisation du renfort, il est prévu deux régions de raideurs différentes, à savoir la région de raideur minimum correspondant à la zone A, et une région de raideur progressive correspondant aux zones B et C.According to one embodiment of the reinforcement shown in FIG. 7: $$\mathrm{RfA}<\mathrm{RfB}\le \mathrm{RfC},$$

with:

• Constant RfA
• Progressive RfB from front to back
• RfC progressive from front to back.

In this embodiment of the reinforcement, two regions of different stiffness are provided, namely the region of minimum stiffness corresponding to zone A, and a region of progressive stiffness corresponding to zones B and C.

avec :

• RfA constante
• RfB progressive de l'avant vers l'arrière
• RfC constante.

According to another embodiment of the reinforcement according to the invention, represented in FIG. $$\mathrm{R}\mathrm{f}\mathrm{AT}<\mathrm{R}\mathrm{f}\mathrm{B}\le \mathrm{R}\mathrm{f}\mathrm{VS},$$

with:

• Constant RfA
• Progressive RfB from front to back
• Constant RfC.

Naturally, the control of the stiffness in longitudinal flexion of the zones A, B and C of the reinforcement is obtained by varying the nature of the constituent materials of the skins 11 and 13 and the core 12 of the sandwich structure. It is also possible to vary this stiffness in longitudinal flexion by varying the thickness by gradually varying the stiffness of the reinforcement in the areas A, B, C, as is apparent from Figures 7 and 8.

According to different alternative embodiments of the examples of FIGS. 7 and 8, the possible variations in the thickness of the reinforcement according to the invention are not linear, since it is preferable that at the connection planes on the one hand, between zones A and B (posterior limit L _A of zone A), and secondly, between zones B and C (posterior limit L _B of zone B), there is no abrupt break of slope .

Regarding the nature of the materials used to make the reinforcement and more particularly its sandwich structure, it should be noted that one of the skins 11, 13, preferably both, of this sandwich structure, is (are) composite material based of woven or non-woven fibers and included in a matrix.
These fibers are preferably selected from the group consisting of: carbon fibers, glass fibers, metal fibers, natural or synthetic textile fibers, and mixtures thereof; carbon and glass fibers being particularly preferred;
The material constituting the matrix is preferably chosen from the group comprising: epoxy, polyester or phenolic resins, thermoplastics - advantageously polyamides, polyurethanes, polyolefins - and their mixtures,
By way of examples of fibers that can be used in the production of the composite skins 11, 13 of the reinforcement according to the invention, mention may be made of the fibers given in the table below, which also indicates the type of weaving plies (15). , 16, 15 ', 16'), as well as the mechanical characteristics of these networks or fibrous webs. fibers Weaving Breaking stress greater than Upper module at Glass UD 700 MPa 25000 MPa Glass Mutidirectionnel 350 MPa 12000 MPa Carbon UD 1500 MPa 70000 MPa Carbon multidirectional 700 MPa 35000 MPa In this table, UD stands for unidirectional.
Advantageously, the core of the sandwich structure is made of synthetic foams (preferably polyurethane, poly (meth) acrylic, polyvinyl chloride), wood or honeycomb.

The sandwich structure occupies only zones B and C in the embodiments shown in FIGS. 7 and 8.

The preferred embodiment of the reinforcement according to the invention could be the third mode described above, in which zone A of minimum stiffness RfA has a minimum constant thickness and combines the maximum torsional stiffness with a low flexural stiffness,

In all the embodiments defined above by way of examples, the median zone B is a zone of progressive stiffness, of variable thickness, making it possible to connect the two terminal zones A and C while bringing the progressivity in stiffness to the reinforcement. and the shoe.

The posterior zone C, for its part, has a maximum stiffness in torsion and flexion and has (preferably) constant thickness and stacking characteristics.

• identiques ou différentes entre elles, et
• constantes ou évolutives pour chaque sous-zone considérée.

According to variants, each zone A, B, C may comprise one or more sub-zones having stiffnesses in longitudinal flexion:

• identical or different from each other, and
• constant or evolving for each sub-area considered.

As can be seen in FIGS. 7 and 8 corresponding to the second and third embodiments of the reinforcement according to the invention, the area A of minimum stiffness RfA does not have a sandwich structure and comprises at least one of the two skins 11, 13 of the zones. B and C in their continuity, and optionally at least one additional layer, not shown in the drawings.

In the second embodiment of FIG. 7, zone A of the reinforcement consists of the extension of the upper skin 11 of the sandwich structure of zones B and C, contiguous to the lower skin 13 of this same sandwich structure.

In Figure 8, third embodiment, the zone A of the reinforcement is simply constituted by the extension of the lower skin 13 of the sandwich structure of the zones B and C. In this embodiment, the upper skin 11 of the sandwich structure zones B and C are extended by a portion 11A into zone A for a partial overlap with the skin 13 in said zone A, in order to ensure the resistance of the reinforcement in the zone adjoining the boundary between A and B.

Figures 11 and 12 show two ways to manufacture the reinforcement according to the invention especially when it corresponds to the first mounting 9. These Figures 11 and 12 partially show the composite structure of the skins 11 or 13 of the sandwich structure. The fibers 14 of the composite skins or skins 11 or 13 of the sandwich structure are arranged in one or more plies 15 and 16 (FIG. 11) 15 ', 16' (FIG. 12) of parallel fibers 14, this or these plies 15, 16, 15 ', 16' being oriented in one or more directions (unidirectional orientation UD or multidirectional).
In the two manufacturing methods of the skins shown in FIGS. 11 and 12, the reinforcement comprises two - plies (15 and 16), (15 'and 16') of parallel fibers 14, these plies being oriented in different directions.

According to a preferred feature of the invention, these two plies (15,16) and (15 ', 16') of parallel fibers 14 are symmetrical with respect to an axis, the latter preferably being the median longitudinal axis β (FIG. 12) of the reinforcement 9 or the δ axis (FIG. 11) perpendicular to the metatarsophalangeal flexion axis α, which forms an angle of approximately 19 ° + or -5 ° with respect to the median longitudinal axis β.

Advantageously, the angle between the two plies (15,16) and (15 ', 16') of parallel fibers 14 is about 90 ° + or -10 °.

Preferably, each web 15, 16, 15 ', 16' is constituted by a fiber fabric.

According to one variant, the reinforcement of the invention is an overmoulded insert 17, which has been fixed in any other way in at least one of the constituent elements 5, 9, 10 of the lower part of the boot, this element being of preferably selected from the group comprising the inner sole 10, the first mounting 9, the outer sole 5; the outer sole 5 being more especially preferred.
Figures 4A and 4B illustrate this advantageous variant of the invention. The sole 5 includes an overmoulded insert 17 forming the reinforcement according to the invention.
Advantageously, this insert has a composite structure, for example of the type described in the embodiments of FIGS. 7 and 8.

According to another variant of the outer sole 5 of FIG. 4A, the overmolded insert 17 may be made visible on one or more locations on the underside of this outer soleplate 5. The insert 17 may also extend over any or part of the soleing surface.

According to the invention, it is conceivable to use particular composite sandwich materials for the manufacture of the reinforcement according to the invention. Thus, this reinforcement may be at least partly constituted by one or more micro-sandwich composite sheets each having a thickness of less than or equal to 3 mm and comprising a composite core interposed between at least two composite skins, the mechanical strength and the cost per mass unit of the core being lower than those of at least one of the skins.

In order to manufacture the reinforcements according to the invention, conventional techniques for producing composites are used.

Thus the polymeric foams likely to form the souls of the sandwich structures are obtained by machining or injection, for example.

The composite skins of the sandwich structures are obtained by in-press polymerization techniques.

The assembly of the various composite skins and the soul or souls, whether they are foam or composite, is made by superposition and by putting into press (pressure of the order of 2 to 10 bars at temperatures of about 100 to 180 ° C.

It is also possible to use bonding or thermo-welding techniques.

According to another of these aspects, the present invention also relates to a cross-country ski boot, (FIGS. 1 and 2), characterized in that it comprises at least one reinforcement 5, 9, 10, 17 according to the invention, such as described above.
This shoe and reinforcement can improve the spring effect in the area of the metatarsophalangeal joint, so the performance of the shoe.
The optimization of the flexion and torsional stiffness compromise compromise significantly improves ski control and handling.
the materials used are light and retain their properties for a very long time. They give the cross-country ski boot, a behavior such that the movements of coiled / unrolled are much more regular and provide better sensations to the sportsmen.
Finally the reinforcement according to the invention provides good protection of the foot during bending because it reduces compression stresses.

Claims (11)

1. A composite reinforcement for a cross-country ski boot, making a foot rolling movement possible, said reinforcement extending over at least a portion of a front zone A located on both sides of the metatarsophalangeal joint (α) from the front end up to the beginning of the plantar arch, over at least a portion of a median zone B corresponding to the plantar arch, and over at least a portion of a rear zone C corresponding to the heel and starting from the end of the plantar arch and ending at the rear end, characterized in that the reinforcement comprises, in zones B and C, at least one "sandwich" structure (11/12/13) constituted by at least one core (12) made of synthetic foams, wood or honeycomb, inserted between at least two layers (11, 13) made of a synthetic material based on woven or nonwoven fibers (14) comprised in a matrix, and in that, in zone A, the reinforcement does not have a sandwich structure and comprises at least one of the two layers 11, 13 of zones B and C in their continuity, so that it is flexible in a substantially longitudinal direction, and in that each zone A, B, C, has a longitudinal flexural stiffness, RfA, RfB, RfC, respectively, such that: $$\mathrm{R}\mathrm{f}\mathrm{A}<\mathrm{R}\mathrm{f}\mathrm{B}\le \mathrm{R}\mathrm{f}\mathrm{C}$$

   
2. Reinforcement according to claim 1, characterized in that:

   - zone A has a front-to-rear constant or progressive stiffness RfA;

   - zone B has a front-to-rear constant or progressive stiffness RfB;

   - zone C has a front-to-rear constant or progressive stiffness RfC.
3. Reinforcement according to any of claims 1 or 2, characterized in that the layers (11, 13) of its sandwich structure are made of a composite material based on woven or nonwoven fibers (14) and comprised in a matrix,

   - the fibers being preferably selected from the group comprising: carbon fibers, glass fibers, metallic fibers, natural or synthetic textile fibers, and their mixtures; the carbon and glass fibers being particularly preferred;

   - the material constituting the matrix being preferably selected in the group including:

   epoxy, polyester or phenolic resins; thermoplastics - advantageously polyamides, polyurethanes, polyolefins, and their mixtures,
4. Reinforcement according to any of the previous claims, characterized in that the fibers (14) of the composite layers of the sandwich structure are arranged in one or several webs (15, 16, 15', 16') of parallel fibers (14), the web(s) (15, 16, 15', 16') being oriented in one or several directions (unidirectional UD or multidirectional orientation).
5. Reinforcement according to claim 4, characterized in that it comprises at least two webs (15, 16, 15', 16') of parallel fibers (14),

   - in that these two webs (15, 16, 15', 16') are oriented along different directions;

   - and in that these two webs (15, 16, 15', 16') of parallel fibers are symmetrical relative to an axis (β, δ), the latter preferably being the longitudinal median axis (β) of the reinforcement, or the axis (δ) perpendicular to the metatarsophalangeal bending axis (α) and forming an angle of about 19° +/- 5° relative to the longitudinal median axis, the angle between the two webs of parallel fibers being preferably about 90° +/- 10°.
6. Reinforcement according to any of the previous claims, characterized in that, in its zone A with minimum stiffness RfA, it comprises an extension of the lower layer 13 of the sandwich structure of zones B and C and an extension 11A of the lower layer 13 of the sandwich structure of zones B and C, which extension covers preferably partially the extension of the layer 13 in said zone A.
7. Reinforcement according to any of claims 1 to 6, characterized in that the reinforcement corresponds to at least one constituent element of the lower portion of the boot (1), said element being preferably selected from the group including: the inner sole (10), the lasting insole (9), and the outer sole (5).
8. Reinforcement according to any of claims 1 to 7, characterized in that the reinforcement is an insert that is duplicate molded in at least one of the constituent elements (5, 9, 10) of the lower portion of the boot (1), this element preferably being selected from the group comprising: the inner sole (10), the lasting insole (9), and the outer sole (5); the outer sole (5) being more particularly preferred.
9. Reinforcement according to any of claims 1 to 8, characterized in that it has a variable thickness, preferably generally increasing from the front of zone A to the rear of zone C, and in that said variation in thickness is linear or nonlinear, preferably without any break in slope in the area of the connecting lines, between zones A and B (rear limit L_A of the zone A), on the one hand, and between zones B and C (rear limit L_B of the zone B), on the other hand, so that there is no sudden break in slope.
10. Reinforcement according to any of claims 1 to 9, characterized in that the reinforcement is at least partially constituted by one or several micro-sandwich composite sheets, each having a thickness less than or equal to 3 mm, and comprising a composite core inserted between at least two composite layers, the mechanical strength of the core and cost per mass unit being less than those of at least one of the layers.
11. Cross-country ski boot making a foot rolling movement possible, characterized in that said boot comprises at least one reinforcement according to any of claims 1 to 10.

Images