FR2517978A1 - Foam filled ski bodies with line tubular inserts - to increase the overall stiffness to wt. ratio - Google Patents

Abstract

Skis with a hollow body filled with cellular (polyurethane or acrylic) resin moulded or injected in situ also incorporate reinforcing elements of tubular section which are plugged or pinched at each end to exclude the cellular foam. Used to provide an enhanced stiffness/wt. ratio, esp. for ski bodies which are relatively deep in the centre and shallow towards each end. The tubular inserts may be of rigid or semi-rigid thermoplastic, thermosetting or elastomeric materials, esp. an alloy (blend) of BBS and polycarbonate or of a fibre-reinforced resin, incorporating glass or carbon fibres. Opt. twin parallel tubes are included. The max. dia. of the tube may be equal to or less than the thickness of the adjacent ski core cavity, may be overlapped by a strip metal profile also within the cellular core.

Description

"Core type ski with winged structure and its manufacturing process".

 The present invention relates generally to the field of skis and their manufacturing process.

 It is currently known to manufacture skis having a hollow tubular structure by placing inside a mold tubes made of glass fiber fabric impregnated with a thermosetting material, formed around air chambers which are inflated. until the sausages conform to the shape of the mold. However, this process appears to be relatively complicated and expensive and is not suitable for the manufacture of skis of the core type made of expanded cellular material.

 It has also been proposed to incorporate a hollow tubular structure formed by a metal tube into the core of expanded material of a ski. The use of a metal tube has the disadvantage of having to be reinforced beforehand with the profile of the ski. In addition, on the one hand the ski thus obtained should be very heavy and on the other hand it risks being subjected to permanent deformations due to the elastic limit of the metal tube and the high stresses which the ski undergoes.

 Contrary in particular to the state of the art described above above, the aim of the present invention is to produce a lighter ski while retaining the advantages which the production of skis of the core type in expanded cellular material obtained by injection or molding, and in particular skis of the polyurethane foam core type.

 The present invention relates, first of all, to a method for producing, in a mold, a ski core made of injected or molded cellular synthetic material, in which this flthttic material is expanded around a hollow tubular structure formed by at least one tube. extending longitudinally. It also relates to the nucleus obtained by this process.

 According to the present invention9 the ends of said tube are closed before the injection or molding operation so that the cellular synthetic material cannot, during its expansion5 penetrate inside said tube.

 The method according to the present invention can also have different variants. Indeed, at least one of the ends of said tube can be closed prior to its introduction into the mold.

 One can crush or partially flatten and close at least one of the ends of said tube, prior to its introduction into the mold.

 It is also possible to crush or flatten completely and maintain crushing or fixing in this state at least one of the ends of said tube, before its introduction into the mold.

 According to the process of the present invention, it is also possible to provide, for the closing of the mold, to ovalize at least partially and in the direction of the thickness of the core; said tube over at least a portion of its length.

 It is also possible to provide, when the mold is closed, to ovalize at least partially and in the direction of the thickness of said core, said tube on at least one of its end portions.

 Thanks to these last two embodiments of the method according to the present invention7 said tube can advantageously adapt to the shapes and E the arrangement of the other elements arranged in the mold such as the inserts for anchoring the shoe fixing screws and can advantageously follow the profile of the ski, without this tube having been previously conformed to this profile.

 The present invention also relates to a ski which can advantageously be manufactured with the aid of the above process.

 The ski according to the present invention comprises an elongated body and in the extension of this body a heel and a spatula and is of the core type made of a cellular synthetic material, injected or molded, this core comprising a tubular structure delimiting therein a longitudinal hollow space. zen This core is surrounded, as is known, by resistant or decorative outer layers to form the final ski.

 According to the present invention9 said tubular structure is drilled by at least one rigid or semi-rigid synthetic resin tube, the ends of said tube being closed and said tube extending, in the core, longitudinally over at least part of said body .

 According to the present invention, at least one of the ends of said tube is closed by a plug.

 According to the present invention, in zains one of the ends of said tube is at least partially flattened or crushed and has, in the direction of the thickness of the ski, a thickness equal to or less than the thickness of the core at right from this end.

 According to the present invention, at least one end of said tube is completely flattened or flattened.

 According to the present invention, the synthetic resin forming said tube can be any. It suffices in fact that it is rigid or semi-rigid and that it has sufficient thermal stability so that during its forming it does not break, in order to prevent the cellular synthetic material from penetrating inside. this tube and so that it does not completely collapse under the pressure exerted by the cellular synthetic material during its expansion.

 One can therefore choose as synthetic resin a thermoplastic resin, a thermosetting resin or an elastomer.

One can also choose an alloy of synthetic resins and in particular an alloy of thermoplastic resins.

 As the resin alloy, it is preferable to choose an ABS alloy (acrylonitrile-butadiene-styrene resin) and a polycarbonate.

 In a variant, provision may also be made to reinforce the synthetic resin by in particular glass fiber, aramid or carbon. In this way, the tube placed in the core can have a certain mechanical function while allowing a lightening of this core.

 According to the present invention, said tubular structure can obviously be formed of several tubes.

 In a variant; one can provide a tubular structure comprising two tubes arranged symmetrically with respect to the longitudinal axis of the ski. One can also provide a tube arranged along the longitudinal axis of the ski.

 It is also possible to provide tubes of different lengths and different sections.

 The manufacturing process and the particular choice of a tube made of a rigid or semi-ridged synthetic material have many advantages. In particular, the choice of a plastic tube closed at its ends and the fact of creating a hollow space makes it possible to obtain a significantly lightened core compared to a solid core, without considerably modifying the specific resistance of this core. In addition, the tube made of a synthetic material and the cellular material surrounding it cooperate, by self-bonding in contact with the foam during its expansion, so as to form a mechanical unit.

The present invention will be better understood from the study of a ski of the injected core type having a particular particular structure and described by way of nonlimiting example and illustrated by the drawing in which
- Figure I represents a ski seen from above in which the tubular structure is shown by transparency
2 shows a side view of the ski shown in Figure 1 1
- Figure 3 shows in an enlarged partial longitudinal section the front half of the ski;
- Figure 4a shows in section an embodiment of one of the ends of the tubular structure
- Figure 4b shows an end view of the tubular structure shown in Figure 4a
- Figure Sa shows in section a second embodiment of the end of the tubular structure
- Figure 5b shows an end view of the tubular structure shown in Figure Sa
- Figure 6 shows a cross section of the ski core in its mold, in the middle part of the tubular structure;
and Figure 7 shows a cross section of the ski core in its mold, in the end portion of the tubular structure.

 As can be seen in FIGS. J and 2, the ski 1 comprises a body 2 which is extended at one of its ends by a heel 3 and at the other of its ends by a tip 4.

 The ski 1 comprises, in its body 2, a tubular structure generally identified by the reference 5. The tubular structure 5 is formed, in the example shown, by two longitudinal tubes 6 and 7 which are arranged symmetrically not relative to the longitudinal axis of the ski 1. In the example shown, these tubes have the same length and extend in the body 2 of the latter without however reaching its ends.

 The tubes 6 and 7 are identical and are hollow. They are further trained to leave. of a cylindrical tube in semi-rigid synthetic resin.

 As can be seen in FIG. 3 which shows a partial longitudinal section along the axis of the tube 6s the ski J comprises a core 8 made of an expanded cellular synthetic resin, for example made of polyurethane foam, produced by injection and expansion in a mold .

 As is known to do, the core 8 is covered by an upper carrier layer 9 and by a lower carrier layer 10. These carrier layers 8 and 9 can simply cover the upper and lower faces of the core 8 so as to form a ski of the sandwich type or can be an integral part of a box completely surrounding the core 8.

 In the upper part of the core 8 and extending in the central part of the skiD is placed a metal or synthetic plate 11 intended for anchoring the screws of the bindings.

 As can be seen in FIG. 3, the tubes 6 and 7, and in particular the tube 6, have their front end 6a and 7a and their rear end 6b and 7b closed as will be seen below with reference to FIGS. 5a and 5b. The tubes 6 and 7 are, in the middle part of the ski, substantially cylindrical and have a diameter substantially equal to the distance separating the insert 11 and the lower layer 10.

 As can be seen in FIG. 3, the tube 6 has a front end portion 6c which is progressively ovalized to substantially follow the profile of the core 8, and consequently the profile of the ski 1. In this portion, the tube 6 has an oval section decreasing towards the end 6a.

 The tube 6 also has a progressively crushed rear end portion following the profile of the core 8 and has in this portion an oval section which decreases. We will explain later how these ovalized portions can be obtained simply. The tube 7 is shaped in the same way as the tube 6.

 With reference to FIGS. 4a, 4b and 5a, 5b we will now describe how the ends 6a, 6b and 7a, 7b of the tubes 6 and 7 can be closed. The end 6a of the tube 6 will be taken as an example.

 In a variant shown in FIGS. 4a and 4b, the end 6a of the tube 6 is crushed so as to take an oval shape and a stopper 12 having the same shape is placed inside this end 6a so as to close the tube 6.

 In a variant shown in Figures Sa and 5b, the end 6a of the tube 6 is completely flattened and is fixed in this state. It can be fixed there, for example by self-bonding by heating this end. In this case, no plug is necessary.

 In the ski shown in Figure 3, the tubes are closed according to the variant shown in Figures a and 5b.

 The variant of ski structure shown in FIG. 3 is not voluntary. The tubes 6 and 7 can extend over any length of the body 2 of the ski 1. A condition is however preferably to be observed. Indeed, it is preferable that the thickness of the ends of the tubes is less than or equal to the thickness of the core at the level of these ends.

 If the tubes 6 and 7 extend in the middle part of the core 8 so that at least one of their ends is located at a place in this core where its thickness is greater than or equal to the outside diameter of the tubes 6 and 7 , these ends can simply be plugged by a plug of circular section, this plug penetrating inside the tube. If, however, a plug is provided which surrounds this end of the tube, the outside diameter of this plug must be less than the thickness of the core 8 at the place where the plug is located in the core B.

 If one of the ends of the tubes 6 and 7 extends in an area of the core where the thickness is less than the outside diameter of these tubes, this end of the tubes must be crushed so that the thickness of this end is less than or equal to the thickness of the core 8 where it is located. This end can then be shaped according to one of the variants shown in Figures 4e, 4b and Sa, 5b.

 We will now describe how the core 8 of the ski 1 shown in FIG. 3 can be made with reference to FIGS. 6 and 7.

 First, take two tubes 6 and 7 of circular section and the same length obtained for example by extruding a synthetic resin such as an alloy of ABS and polycarbonate which is semi-rigid.

The ends of these tubes 6 and 7 are completely crushed and heated so as to self-bond these ends in this crushed state. The tubes 6 and 7 are then closed,
There are, in the U-shaped channel 14a of the lower part 14 of an injection mold 13, the tubes 6 and 7, longitudinally and metrically, as well as the other elements such as the insert 11.

 The mold 13 is closed by placing its upper part 15 on its lower part 14, the parts 14 and i5 delimiting a hollow space having the shape of the desired core. When this mold 13 is closed, the end portions of the tubes 6 and 7 are crushed, by being ovalized, between the lower part 14 and the upper part 15 of the mold and according to the profile of the mold, as can be seen. see in figure 7.

 Finally, the synthetic resin is injected such as polyurethane which expands in the mold 13 but which does not penetrate inside the tubes 6 and 7 since their ends are closed.

When the synthetic resin is expanded, the tubes leave two longitudinal hollow spaces in the core.

The hollow spaces thus created allow on the one hand to produce a much lighter core than solid cores and on the other hand a saving of expanded cellular resin,
After demolding the core thus obtained, the ski manufacturing process is continued and ultimately a ski is obtained which is considerably lighter and has substantially the same mechanical qualities as a ski of the same structure but with a solid core,
It should be noted that if one or more tubes are provided which extend only in the middle part of the ski and which does not undergo deformations when the mold is closed, these tubes can then be chosen from a rigid material. If on the other hand one or more tubes are provided which extend beyond the middle part of the ski, it will then be preferable to choose these tubes in a semi-rigid material so that, during the deformations which they undergo upon closing from their ends and when the injection mold is closed, they do not break in such a way that the resin injected into the mold can penetrate and expand inside them.

 The present invention is not limited to the examples and embodiments described above. Many other variants are possible without departing from the scope of the present invention.

Claims (16)

 1. Method for producing, in a mold, a ski core of injected or molded cellular synthetic material, in which the synthetic material is expanded around a hollow tubular structure extending longitudinally formed by carefully a tube, characterized by the fact that the ends of said tube are closed before the injection or molding operation so that the synthetic material, during its expansion, cannot penetrate inside said tube.  2. Method according to claim 1, characterized in that, prior to its introduction into the mold, it is partially flattened or crushed and the air is closed at least one of the ends of said tube.  3. Method according to claim 1, characterized in that, prior to its introduction into the mold, it is completely crushed or flattened and that is maintained crushed or fixed in this state at least one of the ends of said tube.  4. Method according to any one of the preceding claims, characterized in that, when the mold is closed, at least in part and in the direction of the thickness of the core, said tube is ovalized on at least a portion of salongeur.  5. Method according to any one of the preceding claims, characterized in that, when the mold is closed, at least in part and in the thickness direction of the core are ovalized: said; ttibe at least la'une dd-end portions of said tube.  6. Method according to any one of claims I to 5, characterized in that, prior to its introduction into the mold, at least one of the ends of said tube is closed by a plug.  7. Ski core obtained by implementing the method according to any one of the preceding claims.  8. Ski comprising a body and in the extension of this body a heel and a spatula and of the core type made of an injected or molded cellular synthetic material, this core comprising a tubular structure delimiting in the latter a longitudinal hollow space, characterized by the fact that said tubular structure is formed by at least one rigid or semi-rigid synthetic resin tube, the ends of said tube being closed and said tube extending, in the core, longitudinally over at least part of said body.  9. Ski according to claim 10, characterized in that at least one of the ends of said tube is closed by a plug.  10. Ski according to one of claims 8 and 9, characterized in that at least one of the ends or end portions of said tube have, in the direction of the thickness of the ski, an equal thickness su less than the thickness of said core.  11. Ski according to any one of claims 8 to 10, characterized in that at least one of the ends of said tube is completely flattened or flattened.  12. Ski according to any one of claims 8 to 11, characterized in that the said tube is made of a synthetic resin chosen from thermoplastic resins, thermosetting resins and elastomers.  13. Ski according to any one of claims 8 to 1G, characterized in that said tube is made of an alloy of synthetic resins such as an alloy of ABS and polycarbonate.  14. Ski according to any one of claims 8 to 13, characterized in that said tube is made of a reinforced synthetic resin.  15. Ski according to any one of claims 8 to 14, characterized in that said tubular structure comprises two tubes arranged symmetrically with respect to the longitudinal axis of the ski.  16. Ski according to any one of claims 8 to 15, characterized by the fact that said tubular structure comprises a third tube arranged along the longitudinal axis of the ski.