EP0594513B1 - Process for making a ski - Google Patents

Abstract

This process for producing a ski consists in assembling, in a shaped mould, at least two assemblies, respectively a first assembly (1) consisting of the running sole (3), edges (4) and at least one mechanical reinforcement element (5), and a second assembly (2) consisting of a rigid shaped shell (7) defining, with the first assembly (1), a space intended to receive a central core (8). Prior to the assembly stage, the base of the said first assembly (1) is subjected to a functional machining. <IMAGE>

Description

The invention relates to a new process for the manufacture and production of skis, in particular alpine skis.

One of the methods allowing the production of such skis consists in assembling, in particular by gluing, two sub-assemblies, respectively a first sub-assembly consisting of the gliding sole, the edges, and at least one reinforcing element, and a second sub-assembly constituted by the upper part of the ski, namely in particular a rigid shell in shape, corresponding to the external shape of the ski, possibly coated with a decoration and comprising inside the central core. This bonding is carried out by any known means, either by means of a thermoplastic film as for example described in the document FR-A-2 663 237, or by means of traditional adhesive for this type of application, or by expansion in situ of the resin constituting the central core (see for example FR-A-2 654 644).

Whatever the ski manufacturing process, once it is made, it is necessary to carry out a certain number of finishing steps, among which the machining of its underside. To do this, the skis are routed to different machining stations. Already, due to the very shape of the ski, namely, by the presence of curved shapes at the tip and the heel, these are difficult to stack and load automatically in each machining station , this operation thus requiring either a person or an automatic feeder.

In addition, during the various grinding or sanding stations of the sole, the skis are subjected to a drive ensuring besides the effective progression of the skis at their level, also the application of pressure in the direction of said tools in order to allow a effective action of these. This training is typically carried out by means of a roller, generally coated with rubber, and applying a relatively high pressure on the top of the ski. Now, more and more often, skis have an upper face with a complex profile and in any case not planar, either because it has hollows, bumps, or else successive plates, even grooves or asymmetries, so that 'There is no longer a stable and constant reference surface capable of serving as a bearing surface for said roller. In this way, these differences in relief are reflected at the level of the sole, generating undulations and therefore altering the sliding properties of the ski, regardless of the number of passes at the grinding or sanding stations.

In addition, by the very fact of the materials used for the manufacture of the ski, it has elasticity both in torsion and in bending. Given the high pressure exerted on the drive roller, under the central reach of said drive roller, there is a deformation of the ski generating a flatness defect, altering the sliding properties of the sole, as well as the handling of the skiing and ease of initiating turns.

It should also be emphasized that with modern technologies, skis are very often pre-decorated, which implies that the machining operations of the lower surface being carried out practically at the end of the manufacturing process, a defect in crippling machining of this lower surface causes the destruction of the entire ski, thereby increasing the importance of the loss.

Finally, this machining operation being carried out on virtually finished skis, it is not uncommon to observe a local deterioration of the decor, either during handling, or again due to the driving roller. This alteration of the decor may be such that it also makes the ski prohibitive for sale.

In other words, this machining phase carried out on a substantially finished ski is not satisfactory in the context of the industrialization and automation of the manufacture of skis.

It should be noted that the lower surface of an alpine ski always consists of a sole made of plastic material bordered by metal edges. This juxtaposition of materials, one hard and the other soft, makes machining by sanding or grinding very delicate because the composition of the abrasive products cannot be ideal simultaneously for each of these two materials: it can only be d '' a compromise, to the detriment of the general quality of finish of this underside, which we know the fundamental role in the context of sliding.

The object of the invention is to overcome these various drawbacks by proposing a method of making skis that reconciles both greater ease of automation and machining of the sole and the edges carried out under optimum conditions.

This method for producing a ski, consisting in assembling by any known means in a shaped mold, at least two sets, respectively a first set, called the sole assembly, consisting of the gliding sole, edges and at least one mechanical reinforcement element, and a second assembly constituted by a rigid shell in shape, defining with the first assembly a space intended to receive a central core is characterized in that prior to the assembly step, the underside of the first assembly undergoes functional machining.

In other words, the invention no longer consists in machining in particular the sole on a finished ski, but in carrying out this phase on a sole assembly, which is rigid and flat, and which also makes it possible automate this machining phase much more easily.

By "functional machining" is meant the phases necessary for obtaining the desired surface geometry for the sole and edge assembly, as well as those necessary for obtaining a suitable roughness for this same assembly.

This functional machining consists first of all of deburring and cleaning, in particular lateral of the edges, for example by scraping, in order to use this lateral face of the edges as a reference face for the subsequent machining phases; then, this first step is followed by the grinding of the sole itself and / or the base of the edge.

The grinding of the sole can advantageously be preceded by one or more sanding steps by means of an abrasive belt, the number of grinding and / or sanding passes being a function of the desired degree of finish.

Advantageously, this machining can be carried out continuously, using a loader containing the said first sole assemblies in the form of stacks, the said assemblies being flat, of constant thickness and the periphery of which corresponds to the dimension line of the ski.

Advantageously, prior to the machining of the sole assembly proper, there is a localized machining of the base of the edges, for example using a diamond disc grinding machine, so as to reduce the height of each of the edges, the base of said edges thus being slightly set back relative to the plane defined by the underside of the sole.

According to the invention, after machining, the tip and the heel are bent. Advantageously, this bending operation is carried out after the chamfering of the edge edges at the areas intended to be bent.

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

Figure 1 is a sectional view of a ski being bonded in a mold after the machining phase according to the invention.

Figure 2 is a partial sectional view of a detail of the sole assembly.

Figure 3 is a schematic representation of the setback operation of the base of the edges.

Figure 4 is a partial schematic representation of the sole assembly after the operation of Figure 3 and in an advantageous form with respect thereto.

Figure 5 is a schematic view of part of the machining line of the sole assembly, of which Figure 6 is a top view.

The ski is made by bonding two sets, namely a first set called "sole assembly" (1), and a second set called "shell assembly" (2). The sole assembly (1) is in known manner constituted by a sliding sole (3), typically made of polyethylene, metal lateral edges (4), extending over a large part of the length of the ski, and an element mechanical reinforcement (5), typically consisting of a textile sheet pre-impregnated with a thermosetting resin, namely in particular epoxy. In addition, the sole assembly (1) may also include additional reinforcing elements, such as for example a blade made of a metal alloy (ZICRAL - registered trademark), or other textile plies.

The shell assembly (2) comprises a rigid shell (7) in shape, for example made of a prepolymerized textile sheet, covered with a film supporting the decoration, and integrating inside the core (8), consisting of all traditional material, including polyurethane, wood, etc .....

According to FIG. 1, these two assemblies (1) and (2) are assembled together in a mold, also in shape, a film of thermosetting adhesive or of hot-melt plastic or of thermoplastic elastomer (6) being previously placed between the two sets (1) and (2).

According to Figure 5, prior to this bonding, and in accordance with the invention, the sole assembly (1) undergoes after its completion, a machining phase. To do this, the various assemblies (1) produced are stored in a stack in a charger (10), said assemblies (1) having a section of constant thickness, are therefore planar, and have an outer periphery corresponding to the dimension line. skiing, namely in particular a reduced width at the level of the skate, which widens towards the heel and the tip. This type of loader, of a type known per se, makes it possible to feed the assemblies (1) one by one on a conveyor intended for conveying said assemblies at the level of the different machining stations (13, 15). At each of the machining stations, each assembly (1) is driven by means of a roller with horizontal axis (12), typically coated with rubber, and also ensuring the progression of the assembly at the level of said station. machining, also the exercise of significant pressure, in order to allow effective action of the machining tool. It is possible on such a machining line to machine several assemblies side by side, as has been shown in FIG. 6.

This machining consists first of all (although not shown in FIGS. 5 and 6) of proceeding to the lateral cleaning of the edges by scraping, an operation necessary to remove the burrs or drips resulting from the creep and then from the baking of the impregnation resin of the reinforcing element (5). Furthermore, it thus allows to have a reference face, particularly useful during the localized machining of the edges, as described later.

According to Figures 2, 3 and 4, this particular machining of the edges consists of grinding or grinding the base (9) of the edges (4), according to a machining width L slightly greater than the effective width of the bead of said edge. This grinding is traditionally carried out by means of a steel grinding wheel (20) or a diamond disc, thus making it possible to obtain a slight offset s from the base (9) of the edge, typically four hundredths of a millimeter, clean to favor the driving of the ski, since it makes it possible to reduce the errors of potential edges. In addition, this setback s can form a small angle α relative to the plane of the sole, as shown in FIG. 4. The precision of the dimension s for indenting the edge is guaranteed by the fact that the surface (22) is a clean reference bearing surface. To guarantee the good appearance of this surface and to promote its adhesion during the final bonding operation, this surface can be sanded in the first operation. The machining width L is ensured by the lateral copying of the edge shown diagrammatically by the arrow (21) in FIG. 3.

Following this machining of the edges, a sanding phase is carried out, intended to eliminate any defect in the longitudinal flatness of the sole. This sanding is traditionally carried out by means of an abrasive band (13) driven in translation in the same direction as the main dimension of the sole assembly (1), and this between two deflection rollers (16), and the operational area comprises a flat pad (14) also directed in this direction, at which the sole assembly (1) is driven under pressure. Advantageously, taking into account the detachment s previously carried out on the cord of each of the edges (4), this sanding phase can be replaced directly by a grinding phase.

Then proceed to the grinding of the sole itself, by means of a grinding wheel more specially adapted to polyethylene, and this in particular, in order to obtain a flatness over the entire width of said sole. The number of grindings or sandings depends on the degree of finish desired. Typically, this number of passages is between 3 and 12.

Once these various operations have been completed, the bending of the tip and the heel is then carried out, bending generally carried out by means of a roller bender, capable of giving shape memory to the metal edges. Advantageously, and prior to this bending operation, the edges of the edges are chamfered at the level of the tips and the heel, in order to give ease to the ski, in particular when driving in a turn.

We then proceed, said sole assemblies being ready, for the actual production of the ski by bonding with the corresponding shell assemblies, by positioning the sole assembly in a mold, then by coating the upper face of this sole assembly with a film of thermoplastic elastomer (6), the bonding properties of which may be revealed when hot, and finally, by positioning the shell assembly on this film. The respective positioning of the two assemblies, sole and shell respectively, is ensured in the mold by any known means.

This process is also particularly suitable, when the bonding of the two assemblies, sole and shell respectively, is ensured by the expansion of a polyurethane foam, acting in particular as a core. In this case, after putting said assemblies in place and closing the mold, the constituents of the foam are injected into the space formed between them. In known manner, the polymerization of the latter gives it adhesion properties, thus capable of firmly and irreversibly joining the sole assembly to the shell assembly.

In another variant, the central core (8) consists of an independent element. When the two assemblies, respectively sole (1) and shell (2) are put in place, as well as said pre-glued core, and after closing the mold, it is subjected to a heating phase, capable of inducing beforehand to the polymerization of the prepreg resin of said core, its creep, so as to come to wet the two assemblies. In known manner, such a resin, in particular an epoxy, develops adhesion properties during its polymerization. This then leads, as in the previous case, to a firm and irreversible connection of the two assemblies, sole and shell respectively.

We therefore observe that with the method of the invention, this machining operation is easily automated, since both the loading on the conveyor, as the temporary storage at the end of said conveyor at which the various stages of 'machining, can be done automatically by conventional loaders.

In addition, due to the fact that one works with a planar element, one overcomes all the drawbacks linked to a non-planar reference surface, and in particular defects in flatness and alteration of the gliding sole, which can prove to be unacceptable for finished skiing.

On the ski obtained according to the invention, after the assembly operation of the two sole and shell assemblies, an operation of lateral machining of the edges may prove to be necessary, in order to eliminate the lateral burrs of glue or polyurethane. However, it does not have to be taken up in actual functional machining of the base of the sole, only a brief operation of final cleaning which can be envisaged, in particular by means of a polishing strip of the SCOTCH-BRITE type (registered trademark ).

Claims (9)

1. Method for producing a ski, consisting in assembling at least two units in a shaped mould, respectively a first unit (1) called the running-sole unit, consisting of the running sole (3), the edges (4) and at least one mechanical reinforcement element (5), and a second unit (2) consisting of a shaped rigid shell (7), defining with the first unit (1) a space intended to receive a central core (8), characterized in that, prior to the assembly step, the base of the said first unit (1) undergoes functional machining.
2. Method according to Claim 1, characterized in that the functional machining of the running-sole unit (1) consists:

   - in first burring and cleaning the lateral faces of the edges (4);

   - in then grinding the running sole (3).
3. Method according to Claim 2, characterized in that the grinding of the running-sole unit (1) is carried out after at least one sanding step.
4. Method according to Claim 3, characterized in that the number of grinding and sanding steps is a function of the desired level of finish.
5. Method according to one of Claims 1 to 4, characterized in that, prior to machining the running-sole unit (1) proper, localized machining of the base of the edges (4) is carried out so as to decrease the height of the bead of each of the edges, the base (9) of the said edges being thus located slightly set back with respect to the plane defined by the base of the running sole (3).
6. Method according to Claim 5, characterized in that the base (9) of the said edges (4) furthermore undergoes additional machining, so as to have an inclination α with respect to the plane of the running sole.
7. Method according to one of Claims 1 to 6, characterized in that the machining phase is carried out continuously, the units (1) being in the form of plane elements of constant thickness, the perimeter of which corresponds to the dimension line of the ski and which are positioned consecutively by means of an automatic loader on a conveyor intended to convey the said units to the various machining stations.
8. Method according to one of Claims 1 to 7, characterized in that, after machining, bending of the ends of the unit (1), which are intended to become the tip and the heel, is carried out.
9. Method according to Claim 8, characterized in that, prior to the bending operation, the ridges of the edges (4) of the said ends which are to be bent are chamfered.

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