METHOD OF MANUFACTURING A GLIDING BOARD

Abstract

This method relates to the manufacture of a gliding board having a non-rectangular cross-section including an upper assembly including at least one upper protective layer and a fibre stiffener impregnated with a thermosetting resin, a polyurethane foam-based core, and a lower assembly including a base of the board. The method involves placing the lower assembly and the upper assembly in a mould, and then injecting a reactive mixture into a space enclosed between the lower assembly and the upper assembly in order to produce an expanded polyurethane foam. The thermosetting resin used to impregnate the fibre stiffener is based on polyurethane and the expanded foam of the core comes into direct contact with the fibre stiffener.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the way in which the invention is implemented and its resulting advantages may more readily be understood, the following description is given, merely by way of example, reference being made to the accompanying drawings:

FIG. 1 is a schematic perspective view of a fibre stiffener shown during the stage when it is impregnated with resin;

FIG. 2 is a cross-sectional view of a mould into which the lower and upper assemblies have been placed; and

FIG. 3 is a cross-sectional view of the same mould shown after injection of the polyurethane foam.

DETAILED DESCRIPTION OF THE INVENTION

The method according to the invention comprises a first stage involving impregnating a fibre stiffener with a polyurethane-based thermosetting resin. In this stage, as shown in FIG. 1, stiffener (1) is initially placed on film (2) which is typically polyethylene-based. The stiffener is then impregnated with a polyurethane-based resin using a brush application technique or similar. The formulation of this resin can vary widely as long as it includes polymerising chemical reagents in polyurethane form as its primary constituent. By way of example, the resin marketed under the BAYPREG brand name by BAYER MATERIEL SCIENCE AG is satisfactory. When this resin is deposited on fibre stiffener (1), a second film (4), also made of polyethylene, is applied to the exposed face of the stiffener. Assembly (5) thus formed is subjected to pressure in order to ensure uniform impregnation of the resin over the entire surface area of the stiffener.

By way of example, the stiffeners used can be unidirectional stiffeners, i.e. mats of yarns having a very large size in the longitudinal direction of the board. These mats of yarns can be associated either by weaving using very small-diameter thread or by using classic stitching operations.

As appropriate, assembly (5) formed by stiffener (1) sandwiched between films (2) and (4) can be exposed to a source of heat so as to complete a first partial polymerisation stage leaving this resin in a condition conventionally referred to as stage B or Beta stage. However, it is not necessary to perform this partial polymerisation in order to implement the invention.

The fibres of the fibre stiffener are either natural or synthetic, for example fibres made of carbon, glass, polyaramide (Kevlar®), or even a blend of these fibres.

Subsequently, stiffener (1) is associated with upper protective layer (10). To achieve this, film (4) is peeled off so that the stiffener has an exposed face which can be applied onto the lower face of upper protective layer (10). If the resin has not been heated, it remains in a sufficiently tacky state to stick to upper protective layer (10) immediately. Conversely, if the resin used to impregnate the stiffener is in a non-tacky state, a bonding intermediate is used to attach stiffener (10) to upper protective layer (10).

Then, the bottom of mould (15) receives the lower assembly, shaped in the form shown, of the smooth base (16) bordered by edges (17) and topped by another fibre stiffener layer (18). Longitudinal reinforcing elements (19) are also introduced in order to form the lateral edges of the future board. Upper assembly (11) consisting of upper protective layer (10) and stiffener (1) is then placed on top of the open space of the mould. The mould is then closed by its cover (20).

The undulating shape of upper assembly (10) and (11) defines, between this upper assembly and the lower assembly, a space (21) into which the components which react in order to form the polyurethane foam will be injected and spread.

After injection and as shown in FIG. 3, these components react and expand, thereby pushing upper assembly (11) against cover (20) of the mould, thus giving the gliding board its final shape. The pressure exerted by the foam of the core results in the foam penetrating slightly into stiffener (1) thus ensuring effective anchoring of the stiffener to the core. The chemical compatibility of the resin of the core and that of the stiffener means that there is chemical continuity between the core and the stiffener and this increases the rigidity of the assembly.

In the embodiment described, stiffener (1) may not extend laterally as far as edges (19). However, in a variation which is not shown, not only said fibre stiffener may reach as far as edges (19), the latter may be retracted in order to create a shell structure with said stiffener then extending as far as edges (17).

At the same time, lower stiffener (18) may also extend as far as lateral edges (19) or even, if there are no lateral edges, extend onto edges (17).

The upper assembly used can be more complex. In particular, it may consist of a combination of reinforcing elements such as a metal plate, a fibre stiffener element impregnated with a previously polymerised thermosetting resin and/or a fibre stiffener element impregnated with a thermoplastic resin or, obviously, the resin according to the invention.

The foregoing description shows that the method according to the invention has the advantage of allowing the manufacture of gliding boards using a method which is simple because it does not include any leaktight intermediate but confers especially attractive rigidity properties.

Claims

1. A method of manufacturing a gliding board having a non-rectangular cross-section comprising: an upper assembly including at least one upper protective layer and a fibre stiffener impregnated with a thermosetting resin;a polyurethane foam-based core; anda lower assembly including a base of the board, wherein:one places the lower assembly and the upper assembly, in which the resin used to impregnate said fibre stiffener is not in a fully polymerised state, are placed in a mould;and then one injects a reactive mixture is injected into a space enclosed between the lower assembly and the upper assembly in order to produce an expanded polyurethane foam;wherein the thermosetting resin used to impregnate the fibre stiffener is based on polyurethane, and the expanded foam of the core comes into direct contact with said fibre stiffener.

2. A method of manufacturing a gliding board as claimed according to claim 1, wherein the thermosetting resin of the fibre stiffener is in a tacky state when the upper assembly is placed in the mould.

3. A method of manufacturing a gliding board as claimed according to claim 1, wherein the thermosetting resin of the fibre stiffener is in a non-tacky state when the upper assembly is placed in the mould.

4. A method of manufacturing a gliding board according to claim 1, wherein the upper assembly consists of a combination of reinforcing elements including at least two of a metal plate, a fibre reinforcing element impregnated with a previously polymerised thermosetting resin, and a fibre reinforcing element impregnated with a thermoplastic resin.

5. A method of manufacturing a gliding board according to claim 1, wherein the lower assembly includes a fibre stiffener impregnated with a polyurethane thermosetting resin.

6. A method of manufacturing a gliding board according to claim 1, comprising a prior stage of producing the fibre stiffener of the upper assembly in which: the fibre stiffener is placed on a film, typically a polyethylene-based film,the fibre stiffener is impregnated with a polyurethane-based resin;the fibre stiffener is covered with a second film; andthe fibre stiffener covered with the films is pressed in order to even out the distribution of the thermosetting resin in the fibre stiffener.

7. A method of manufacturing a gliding board according to claim 1, wherein the fibre stiffener is exposed to a source of heat in order to make it non-tacky.

8. A method of manufacturing a gliding board according to claim 1, wherein the mould is exposed to a source of heat during a polymerisation reaction of the mixture that constitutes the core.