EP0677306A1 - Ski and method for producing the same - Google Patents

Abstract

The ski which is made of composite material has a sliding plate (1) edged with side squares (10) . Along its length it carries superposed sub-assemblies (11,12,14,15) fixed to each other by a visco-elastic sheet or plate interface (16) with an inverted V section. The visco-elastic sheet is located in the median neutral fibre plane of the ski thickness. The maximum thickness of the ski is greater than 26 mm. The lower and upper sub-assemblies are made of polyurethane or one in polyurethane and the other of wood. The cores (11,12) of the sub assembly are surrounded by a fabric sheath (14,15) pre-impregnated with a thermal hardening resin, such as epoxide. The visco-elastic sheet shows through the lateral edges of the ski. The two sub assemblies and the visco elastic sheet are encompassed in a shell (13) . <IMAGE>

Description

The invention relates to a new type of ski, in particular alpine skiing, or even also cross-country skiing, advantageously but not limitatively provided with a non-planar upper profile. It also relates to methods of manufacturing this type of ski.

The profile of the skis, originally very traditional, since it has a substantially rectangular or even trapezoidal cross section, has substantially evolved to result in skis of variable shapes, which may in particular include a non-planar top, giving for example a triangular cross section.

If this change in the profile of alpine skis certainly meets the aim of optimizing the qualities, in particular the reactivity of these skis, we have also noticed that they could cause a general weakening of the ski structure, and particularly of the phenomena ruptures or delaminations.

These rupturing phenomena also prove to be more marked, as soon as a more complex ski profile is adopted which varies the distance relative to the neutral fiber, by increasing, in certain areas, this distance in a dangerous manner.

In a modern ski produced in composite structure, taking into account the elastic limit of the materials used as reinforcements, the limit thickness of the ski, capable of giving it properties of sufficient resistance to the maximum stresses of traction and compression during bending stresses , is around 26 mm. In such a ski, and because of the steel edges used, the neutral fiber is located substantially at 40% of the thickness of the ski starting from the sole.

Furthermore, the current trend in the production of alpine skis, leads to a general narrowing of the ski, in order to acquire greater precision when cornering. The corollary to this narrowing of the ski is constituted by the elevation of the skier's feet. Indeed, by this narrowing, during a turn, the risk increases to see the shoe wear on the snow, and not the edges of the ski, resulting almost inevitably by a shifting of the ski, which can also cause the fall. By increasing the thickness of the ski, we cancel, if not reduce this risk, because we move the shoe away from the snow.

There is therefore an contradiction between this concern to increase the thickness of the skis, and the risks involved in terms of resistance to rupture of the structure which constitutes them.

The invention proposes to produce a thick ski in composite material, capable of overcoming these phenomena of ruptures and delamination. This ski, the thickness of which at the pad level is greater than 26 mm, is produced in two main parts, that is to say comprising two sub-assemblies, respectively a lower main sub-assembly, and an upper secondary sub-assembly. , extending substantially over the entire carrying length of the ski, the subassemblies being secured to one another by means of a sheet or plate made of a visco-elastic material.

In patent US-A-5 232 241, a ski has been described, the upper face of which has a recess intended to receive a plate comprising the fasteners, namely the front stop and the heel piece, this plate being glued to the overall structure of the ski by introducing a visco-elastic material at the interface. In fact, this plate, known as a "binding" plate, is partially damped against vibrations generated by the progression of skiing on snow. In addition, by the particular form of the recess, and the complementary shape of said plate, the role of the intermediate element in visco-elastic material is necessarily limited to the sole damping function.

There has also been proposed in documents FR-A-2 670 392 and 2 675 391 an alpine ski comprising on the one hand, the ski itself and on the other hand, a stiffener, shorter than the contact surface of the ski with snow, and attached to part of the upper face of the ski, the ski itself and the stiffener further comprising at their interface a layer of flexible elastic or visco-elastic material in order to provide damping functions. The stiffener used has the function of limiting bending and aims to oppose the excessive opening of the ski. It therefore fulfills here only a function of adjustment in bending, partially modified by the damping action of the plate of visco-elastic material.

In document FR-A-2 237 653, a composite ski has been described integrating within its structure, and under the filling core, a layer of a material with high modulus of elasticity joined to an elastomer layer, intended to fulfill only the shock absorber function. Therefore, the elastomer layer, placed inside the reinforcing elements, relative to the neutral fiber, provides no solution to the phenomena of delamination and failure.

In other words, no element of the prior art taught a solution capable of allowing the use of skis made of composite materials, of relatively large thickness, in any case, much greater than the thicknesses conventionally used, and starting from more complex profile skis.

The ski according to the invention consists, over its carrying length, of two superposed sub-assemblies, secured to one another by means of an interface constituted by a sheet or a plate made of a visco-elastic material , glued over its entire length to each of these two sub-assemblies. It is characterized in that the sheet or plate of visco-elastic material is located approximately at the level of the median plane of the thickness of the ski.

In this way, two mechanized ski cores are obtained, one on top of the other, allowing the shearing phenomena of the upper sub-assembly to occur on the lower sub-assembly without however leading to the delamination phenomenon of the reinforcing elements constituting the mechanization. of each subset. In fact, it is thus possible to make skis of relatively large thickness without fear of the occurrence of rupture and delamination phenomena.

Advantageously, said median plane incorporates the neutral fiber of the ski. In this way, said plate or sheet of visco-elastic material is located at the level of the neutral fiber, said neutral fiber being traditionally defined as being the zone at which the compressive and tensile stresses are canceled.

According to certain embodiments of the invention, the interface between the two sub-assemblies is not planar, but can adopt any profile, and for example in inverted V.

The two sub-assemblies, respectively lower and upper, both comprise a core made of polyurethane, or one made of polyurethane and the other of wood, or even of other substitute materials, each core comprising at least one element. reinforcement consisting of either a fabric or a sheet of glass fibers, carbon or aramids (KEVLAR - Registered trademark), or by a metal strip pre-impregnated with a thermosetting resin, in particular to promote its bonding.

Each of the sub-assemblies advantageously consists of a core surrounded by a sheath of woven material, advantageously pre-impregnated with a thermosetting resin, such as an epoxy resin.

In an advantageous embodiment of the invention, the strip of visco-elastic material is flush laterally at the edges of the ski.

In another embodiment of the invention, the two sub-assemblies as well as the intermediate element constituted by the plate of visco-elastic material are included in a shaped shell, supporting the decoration.

The invention also relates to a method for producing such a ski. This process is characterized in that the constituent sub-assemblies of the ski are directly produced according to the desired profile, then placed in a mold, with the interposition of an interface made of visco-elastic material pre-bonded with a resin, the cohesion of the final constitutive structure of the ski being obtained by raising the temperature of the mold, liquefying said prepreg resin and revealing its qualities of adhesion. The cores are produced either by machining or by injection of polyurethane in a specific mold. The two cores entering the structure of the same ski can be of identical or different natures.

In another embodiment, the lower sub-assembly previously produced according to the final shape, is put into place within a mold in shape on the sole and square elements, then we proceed when the sheet or sheet of visco-elastic material is put in place, then these elements are capped by a shell comprising, at its upper internal face, reinforcing elements, and finally, polyurethane is injected in order to to form the upper core inside the space provided between the shell and the sheet of visco-elastic material.

In a variant of this embodiment, the sheet of visco-elastic material is covered with a reinforcing strip prior to the injection of polyurethane.

The manner in which the invention can be implemented and the advantages which ensue therefrom will emerge more clearly from the elements of embodiment which follow, given by way of nonlimiting indication in support of the appended figures.

Figure 1 is a schematic perspective representation of a variable profile ski implementing the invention.

Figures 2 and 3 are schematic representations in cross section of a ski with a traditional profile, according to two different embodiments, according to the invention.

Figures 4 and 5 are schematic representations of cross section of the ski shown in Figure 1, also according to two different embodiments.

Figure 6 is a schematic representation in cross section of a ski, according to the profile of Figure 1, during molding, produced according to another embodiment of the invention.

FIG. 7 is a schematic representation in cross section of a ski, during molding, produced according to another embodiment of the invention.

The ski shown in FIG. 1 firstly comprises a gliding sole (1), extending between its two ends, respectively posterior (2) (heel) and anterior (3) (tip). This ski may be with a full hull, that is to say, covering the ski from one edge to another, as also shown in FIGS. 2 and 4, or with partial hull (FIG. 3 and 5), or on the contrary more traditional and, in this case includes side edges.

The ski shown in Figure 1 has a particular profile, also described in French application No. 93.06807 of the Applicant, since its upper face (4), which in this case must be understood as being the surface s' extending from the upper end of a side edge to the other when these exist, or directly from one metal edge to another when it is a hull ski, is in relief and present at the at least one upper edge (5), in fact defining two slopes respectively (6) and (8), inclined relative to the plane of the surface of the sole. In fact, any cross section of this type of ski is of substantially triangular shape, as can be seen in FIGS. 4, 5, 6 and 7.

According to a characteristic of the invention, the thickness of this ski, in particular at the level of the skate (9), that is to say the thickest central zone of the ski at the level of which the bindings are implanted, is greater than 26 mm, and for example 28 mm at its thickest point.

In addition, according to another essential characteristic of the invention, the internal structure of the ski basically comprises two sub-assemblies each comprising a core, respectively (11) and (12), extending over the entire bearing length of the ski, secured between them, in particular by bonding, at their common interface, said interface further receiving a sheet or plate (16) of a visco-elastic material. The carrying length of a ski is defined as being the distance on the sole separating the two front (23) and rear (24) contact lines of the ski.

The two sub-assemblies integrating the cores (11) and (12) are thus likely, by the existence of this sheet or plate of visco-elastic material (16), to move very slightly, one relative to the 'other, in other words to allow shearing movement of the upper part of the ski relative to the lower part, without causing rupture or delamination phenomena, which skis known hitherto did not allow to obtain, taking into account the rigidity of the stacks, therefore the relative elastic non-shearing, that is to say non-destructive.

This fundamental result thus makes it possible to produce skis of relatively large thickness or of an improved profile such as the profile shown in FIGS. 1, 4, 5, 6 and 7.

According to a first embodiment of the invention, the two cores (11) and (12) are made of polyurethane, each of said cores being surrounded by a fabric sheath respectively (14) and (15), playing the role of reinforcing element, and constituting with said cores (11, 12) the lower and upper sub-assemblies. The polyurethane cores can advantageously be produced before the actual production of the ski, either by machining or by injection into a specific mold.

In the example described in connection with FIG. 3, the ski itself is finalized at the level of a mold, in which the sole (1), first made of polyethylene and two lateral metal edges, are first put in place. (10). The first core (11) provided with its fabric sheath (14) pre-impregnated with a thermosetting epoxy resin is then placed on the sole (1) between two vertical edges (7). The visco-elastic material interface (16) is then placed flat on the upper face of the core (11) and the edges (7). We position then the upper core (12) also provided with a fabric sheath (15) pre-impregnated with a thermosetting resin, in particular an epoxy resin, on said interface (16). The assembly is then covered for example with a shaped shell (13), supporting the decor. The mold is then closed and brought to temperature so as to lead to a quasi-liquefaction of the prepreg resins, making it possible to develop their bonding properties, and thus ensuring the cohesion of the whole.

This bonding occurs on the one hand, between the sole and the edges (1, 10) and the lower sub-assembly (11, 14), then between the sheath (14) and the edges (7), then between the sub-assembly lower (11, 14) and the viscoelastic plate (16), and then between said viscoelastic plate (16) and the upper sub-assembly (12, 15), and finally, between the sheath (15) and the outer shell (13).

In the example described in FIG. 2, the ski is a ski with a typically trapezoidal cross section. However, this ski may have a rectangular profile as described in FIG. 3, or else, with a variable profile as shown in FIGS. 1, 4, 5, 6 and 7, and so have a triangular section, the characteristics of which dimensions of each of the faces are likely to vary throughout the ski.

The production method described in connection with FIGS. 2, 4 and 5 is identical to the previous one, with the proviso that this ski has no side edges, and that the shell (13) covers the two sub-assemblies to come practically resting on the edges (10). It is entirely possible to replace the polyurethane core with a wooden core (19) or equivalent, as shown in FIG. 4.

In addition, the visco-elastic material is not necessarily flat and parallel to the sole (1), as shown in Figures 2, 3 and 4, but can adopt a particular profile more suited to of the ski profile as shown in FIG. 5.

In fact and according to an essential characteristic of the invention, the interface (16) of visco-elastic material adopts a shape such that it allows its positioning to come as close as possible to the median plane of the thickness of the ski, and advantageously neutral fiber of the ski, in order to optimize the shear conditions of the ski even when the ski is heavily stressed so as to, on the one hand, reduce the risks of delamination, and on the other hand, increase the reactivity characteristics of the ski.

In addition, the properties, in particular mechanical properties of the interface film (16) made of visco-elastic material, are liable to vary as a function of its positioning over the length of the ski, in order to facilitate the shearing phenomenon in areas of greatest stress.

According to another method of carrying out the invention (see FIG. 6), after fitting the preformed lower core (11) wrapped in a sheath (14) on the sole (1) and the edges (10) at the inside the mold (20), then positioning of the visco-elastic interface (16) on said lower sub-assembly (11, 14), and finally positioning on said interface (16) of a fabric sheath (15), the interior of which is another stretchable and waterproof sheath (17), the whole being capped with a preformed shell (13) or a sheet intended to subsequently form the shell (13), the closure of the mold by means of the cover (21), then by injection of the constituents (polyol and isocyanate) of a polyurethane foam inside said sheath (17), which in contact with one another, react in a known manner and expand so as to come fill the empty space provided by the shell (13) to form in situ the second upper core (12), and if necessary, the shell (13).

In another embodiment of the invention, more specifically shown in Figure 7, is positioned on the sole (1) and the edges (10) inside a mold (20, 21), the sub- lower assembly (11,14) analogously to the example described above, and on which the interface (16) is positioned flat in visco-elastic, a layer of a reinforcing element is placed on its upper face ( 18). A sheet is then put in place after completion of the ski to form a shell (13), said sheet being provided at its upper internal face with a layer of a reinforcing element (22). The mold (20, 21) is closed and finally the polyurethane is injected into the free space provided between the interface (16) and the sheet (13), so as to produce the core upper (12). In the event of incompatibility, in particular chemical or adhesive incompatibility between the polyurethane and the impregnation resins of the reinforcing elements (18) and (22), it is possible to install a tight and stretchable sheath (17) on said interface ( 16) prior to closing the mold (20, 21), and inside which the polyurethane is actually injected.

When the ski is thus produced, the edges of the reinforcing element (22) are not in contact with the reinforcing element (18) and a fortiori the interface (16), so as to create at this level a discontinuity of the reinforcements, to facilitate the shearing phenomena of the upper sub-assembly relative to the lower sub-assembly on either side of the interface (16,18).

Furthermore, when the external shell (13) includes the two lower and upper sub-assemblies, without showing any break, that is to say discontinuity at the interface (16) (see FIGS. 2, 4, 6, 7), the shear occurring at said viscoelastic interface (16) is taken up by the plasticity of the material constituting the shell: polyethylene, ABS, etc..

Thus, such a ski produced in this way, presents great possibilities in terms of flexion, while allowing the use of a structure of relatively large thickness and improved, variable profiles, such as in particular the ski described in connection with the figure. 1.

Claims (15)

1 / Ski made of composite material, comprising a gliding sole (1), possibly bordered by lateral edges (10), and formed over its entire bearing length of two superimposed, joined sub-assemblies (11, 12, 14, 15) to each other by means of an interface constituted by a plate or sheet (16) of a viscoelastic material, glued over its entire length to each of said subassemblies, characterized in that the sheet or plate (16) of visco-elastic material is located approximately at the level of the median plane of the thickness of the ski. 2 / Ski according to claim 1, characterized in that the median plane incorporates the neutral fiber of the ski, so that said plate or sheet of visco-elastic material (16) is located at the neutral fiber of the ski. 3 / Ski according to one of claims 1 and 2 characterized in that its maximum thickness, in particular at the level of the skate is greater than 26 millimeters. 4 / Ski according to one of claims 1 to 3, characterized in that the interface in visco-elastic material (16) adopts any profile, and in particular in inverted V. 5 / Ski according to one of claims 1 to 4, characterized in that the two sub-assemblies, respectively lower (11, 14) and upper (12, 15), are made of polyurethane, or one of polyurethane and the other in wood, or even in other substitute materials. 6 / Ski according to claim 5, characterized in that each of the cores (11, 12) constituting the sub-assemblies is surrounded by a sheath (14, 15) of woven material, advantageously pre-impregnated with a thermosetting resin, and in particular in epoxy resin. 7 / Ski according to one of claims 1 to 6, characterized in that the sheet or plate (16) of visco-elastic material is flush with the side edges of the ski. 8 / Ski according to one of claims 1 to 6, characterized in that the two sub-assemblies (11, 12, 14, 15) as well as the intermediate element constituted by the plate of visco-elastic material (16) are enclosed in a shaped shell (13) supporting the decor. 9 / Ski according to one of claims 1 to 8, characterized in that the mechanical properties of the interface (16) made of viscoelastic material vary depending on its location relative to the length of the ski. 10 / Method for producing a composite ski consisting of two sub-assemblies (11, 12, 14, 15) superimposed, secured to one another by means of an interface constituted by a plate or sheet (16) in a visco-elastic material, glued over its entire length to each of said subassemblies, characterized in that the subassemblies (11,12, 14, 15) are directly produced according to the desired profile, then put in placed in a mold, with interposition of the interface (16) in viscoelastic material pre-bonded with a resin, the cohesion of the final constitutive structure of the ski being obtained by raising the temperature of the mold, liquefying said pre-resin impregnation and revealing its qualities of adhesion. 11 / Method for producing a composite ski consisting of two sub-assemblies (11, 12, 14, 15) superimposed, secured to one another via an interface constituted by a plate or sheet (16) in a visco-elastic material, glued over its entire length to each of said subassemblies, characterized in that it consists: - First of all to produce the lower sub-assembly (11, 14) according to its final profile; - Then to position said sub-assembly (11,14) within a mold in the form of the gliding sole (1) possibly bordered by edges (10), to which it is secured by gluing,; - Then place flat on the sub-assembly (11, 14) a plate or sheet of a visco-elastic material (16); - Then to cover these elements with a shell (13); - then to close the mold in shape; - And finally, to inject into the space provided between the interface (16) and the shell (13) the constituents of a polyurethane foam, which in known manner react and expand to fill the entire said space, in order to form the upper core (12). 12 / A method of making a ski according to claim 11, characterized in that the hull (13) is capable of extending from one edge to another, or from one edge to another. 13 / A method of producing a ski according to one of claims 11 and 12, characterized in that the shell (13) comprises at its upper internal face a reinforcing element (22), which, when the ski is achieved, does not reach the level of the interface (16). 14 / A method of producing a ski according to one of claims 11 to 13, characterized in that the injection of the polyurethane constituents takes place inside a stretchable and waterproof plastic sheath (17), in particular to said constituents, previously positioned flat on the plate or sheet (16) of visco-elastic material. 15 / A method for producing a ski according to one of claims 11 to 14, characterized in that the interface (16) receives on its upper face, prior to the injection of the polyurethane, a reinforcing element (18 ).

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