Ski and Process for Its Manufacture

This invention pertains to a ski and its manufacturing process.

A ski usually displays one or more upper layers of decorations and protections against external attacks, which sometimes extend laterally to envelop the edges of the ski.

The prior art offers many solutions, the most conventional of which resides in the manufacture of an extruded A.B.S. leaf protection or of a filled thermohardening resin to which thin layers of lacquer and finishing varnish are applied. These structures have the disadvantage of weak resistance to scraping and offer only a small degree of resolution in providing of durable decorations.

Other supports have enabled the use of the sublimation process such as described in patent FR 2 596 286 which discloses the use of a two-layer film of polyamide and sequenced polyamidepolyesther. However this type of construction presents a serious problem of resistance against hot flow for certain flexible grades and of compatibility in adhesiveness with the lower subassembly which constitutes the gathering of the so-called "mechanical" elements of the ski.

It is often necessary to use gluing films like those which are described, for example, in applicant's French Patent No. 89 15662.

It is an object of this invention to provide an upper decoration and protection element, at lower cost, which resists external attacks and hot flow, and which is compatible with materials generally used in mechanical reinforcements, thus enabling the use of all the modern processes of embossing, such as, for example, sublimation.

To this end, the invention pertains to a ski that is made up of an upper decoration and protection sub-assembly comprising a lower layer, comprised of a copolymer of styrene and either carboxylic acid or a carboxylic acid anhydride or a mixture of those copolymers, to which adheres at least one upper layer made of a polyamide.

The invention also pertains to the process of manufacturing such a ski.

Other objects, characteristics and advantages of this invention will emerge from the following description of several embodiments thereof, provided with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a ski according to the invention;

FIG. 2 shows a simplified example of a cross section of a ski according to a first embodiment of the invention; and

FIG. 3 shows a cross sectional view of the detailed structure of the ski according to a second embodiment of the invention.

FIG. 1 shows in perspective a ski made according to the invention. Like conventional skis, this ski includes an upper face 1, a lower face 2 or sliding surface, two lateral faces 3 and 4, and a front end 5 that is bent upwardly, in the form of a spatula. A decoration 6, shown schematically, is visible from the outface on the upper face 1 and on the lateral faces 3 and 4.

FIG. 2 illustrates an embodiment of the ski comprising an upper decoration and protection sub-assembly 7 that is constituted of two layers 71 and 72; the lower layer 71 is made of a copolymer of styrene and either a carboxylic acid or a carboxylic acid anhydride; the upper layer 72 is made of polyamide.

The lower layer 71 is an opaque plastic material with a density close to 1, and is preferably comprised of a copolymer of styrene and, of maleic anhydride. It can eventually be modified or filled by any means known to those skilled in the art so as to augment its mechanical characteristics. Thus, the lower layer 71 may be comprised of a mixture of a copolymer of styrene and of maleic anhydride, and, for instance, an elastomer. In the kinds of fill material that are deemed suitable, glass balls, fiber of glass, of carbon or others could be used.

This copolymer displays very good adhesive capabilities with the upper layer 72. The polyamide that comprises the latter is preferably selected from among the polyamides 11 which are polyamides having 11 carbon atoms between 2 NH groups of the monomer. It is transparent, rigid and displays good resistance against external conditions. Moreover, it is easily sublimated. Each layer 71 and 72 has a thickness from 0.1 to about 1 mm.

FIG. 3 shows a sectional view of the detailed structure of a ski according to another embodiment of the invention where the upper decoration and protection unit 7 extends laterally to the level of the edges 8 and has a section whose shape is substantially that of a reversed U. This construction has the advantage of allowing the application or extending the decoration on the lateral faces 3 and 4 of the ski.

The decoration and protection sub-assembly 7 is associated with an upper reinforcement layer of the mechanical sub-assembly 9, for example, through the intermedian, of a layer of glue.

According to a preferred embodiment of the invention, the mechanical sub-assembly 9 includes an upper reinforcement layer 91 comprised of a textile reinforcement sheet and of a thermohardening matrix such as an epoxide, polyester or polyurethane resin or a thermoplastic matrix. In those specific instances, the matrix has excellent adhesive properties with the lower layer of copolymer of the decoration sub-assembly, thus obviating the need for a supplemental interface of glue.

The lower mechanical sub-assembly 9 combines all the elements needed for the ski's resistance, namely, a sliding sole 94, usually of polyethylene, edges 8, a lower reinforcement 93, a core 92, and at least one upper reinforcement layer 91. The structure shown in FIG. 3 is provided only by way of example.

The invention also relates to the process of manufacturing such a ski including assembling the upper decoration subassembly 7 with the lower mechanical sub-assembly 9, and includes a prior step of manufacturing the decoration sub-assembly. This step makes it possible to obtain the adhesion of the upper layer 72 made of polyamide, and the lower layer 71 made of a copolymer of styrene and of carboxylic acid or a carboxylic acid anhydride. The double layer that is obtained meets the gluing requirements that are normally recognized for a laminate in the manufacturing of a ski.

The most commonly used processes are coextrusion and hot coating with an acrylic resin. Good gluing results are obtained by coextrusion of the double layer at a temperature close to 240.degree. C., at die relief. This operation is followed by continuous calendering, in order to define the thickness and the finish of the sub-assembly. Calendering also allows for the pursuit of adhesion kinetics for the two compounds that equals about 20 seconds at 160.degree. C.

Finally, this prior manufacturing step includes a last decoration phase. It can be executed through sublimation as described, for example, in applicant's French Patent No. 87 13552.

The decoration sub-assembly thus formed is applied onto the lower mechanical sub-assembly 9, and especially on at least part of an upper reinforcement layer 91 of the sub-assembly. Obviously, as shown in FIG. 3, the polymer layer 71 can extend laterally beyond the reinforcement by adhering to other elements, such as bindings, edges, or others. The assembly step can preferably include a molding phase proper during which the various elements are subjected to high pressures and temperatures. The adhesion is especially efficient when the upper reinforcement layer is comprised of a pre-impregnated textile sheet of a thermohardening resin matrix, not entirely reticulated, or of a thermoplastic resin matrix.

The epoxide, polyester, or polyurethane resin matrices generally provide the best results when they are used with a styrene and maleic anhydride copolymer whether modified or not. It is the molding operation which allows for the reactivation of the final reticulation and that makes it possible to provoke adhesion in the case of a thermohardening resin matrix.

The implementation of the molding operation can be different according to the processes; an example of a manufacturing process of a ski of which the core is injected is described in applicant's French Patent No. 89 15664. Of course, the molding phase does not take effect when the elements of the mechanical sub-assembly are manufactured before, then assembled by way of gluing.