FR2615746A1 - DOWNHILL SKIING AND METHOD OF MANUFACTURING THE SKI - Google Patents

Abstract

1. A downhill ski comprising a sole (1) made of flexible or semi-rigid material, having a profile which is substantially constant along the entire length of the ski, and the two longitudinal edges of which are embedded in metallic flanges (6), and whose central portion is in contact via its surface facing the core (9) with a layer (7) of elastic material, characterised in that the central portion (2) of the sole has a thickness (e) less than the thickness (E) of its lateral zones (3) embedded in the lower flanges (6), and in that the layer (7) of elastic material interposed between the central portion (2) of the sole and a hard layer (8) located on the side of the core is compressed between these two elements, its thickness before compression being greater that the difference (E-e) between the two thicknesses of the sole.

Description

DOWNHILL SKIING AND METHOD

MANUFACTURING THIS SKI

  The present invention relates to a downhill ski, also called downhill skiing or downhill skiing, and a method of manufacturing such a ski. The lower part of a large number of runway skis currently known consists of a very high density and very high molecular weight polyethylene sole, which is bordered by edges

in steel.

  These soles are flat and of constant thickness. These soles are conventionally cut into slices of constant thickness in a flat cylinder, in the form of a grinding wheel, obtained by sintering the polyethylene

in powder.

  The invention aims to improve the glide of track skis semi-rigid plastic sole, more particularly to polyethylene sole. It is based on the observation made by observing children's games using either inflatable sledges or rigid plastic sledges, that snow slides on inflatable sleds are superior to sleds made of rigid plastic material. This result is obtained by a ski whose sole, which is of constant profile on substantially

  the entire length of the ski, is made of a flexible or semi-rigid material, preferably

  essentially in powder polyethylene, of high density, very high molecular weight, extruded according to a particular known method, to a profiled shape such that the thickness of this sole at the lower edges is significantly greater than its thickness on the remainder of the width of the ski. Furthermore, a layer of an elastic material, for example a polyethylene foam or elastic rubber, is compressed between this lower thickness of the sole and a hard layer placed above. In the middle part of the ski, an elastic and slightly curved underside in convex form is thus obtained in the absence of strong pressure on the ski, so that the surface

  Slip at this place is quite close to that of an inflatable sledge.

  To manufacture such a ski, polyethylene extrusion is first of all made of a sole which is profiled so as to have a flat base and a thickness which is, in the transverse direction, much higher on the edges than in the middle part. remaining. The ski is then produced by stacking under pressure in the mold of several layers,

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26157 4 6

  which necessarily this profiled sole placed in the bottom of the mold and bordered by the two lower edges, then a layer of elastic foam, surmounting at least the sole portion of smaller thickness and having a greater thickness than the hollow formed in this sole due to of this lesser median thickness, then at least

  a hard layer, such as a rigid reinforcement layer.

  In any case, the invention will be well understood, and its advantages

  and other characteristics will emerge, in the course of the following description

  a non-limiting embodiment of this ski, with reference to the accompanying schematic drawings in which: Figure 1 is a perspective view of the extruded sole, before making this ski;

  Figure 2 is a cross-section showing the phase of reali-

  molding; Figure 3 is a cross section of this ski according to IIIIII of Figure 4; Figure 4 is a side view of this ski, worn by a skier Figure 5 is a cross section of this ski according to V-V of

Figure 4.

  FIG. 1 shows the appearance of the polyethylene strip, obtained by extrusion in a piston extruder, which is intended to constitute,

  after cutting to the right length, the sole 1 of this ski.

  This sole I has a contoured shape. Laterally, its thick-

  E is equal to the usual thickness of polyethylene soles

  sliced, chosen such that the two lateral edges of the sole

  closely under the two lower edges of the ski. This thickness is, however, equal to E only over a zone 3 of relatively small width I on each side of the sole, of the order of one tenth to one fifth of the total width L of the sole: on the remaining median part 2 of the sole, width A = L - 2 1, the thickness of the sole is equal to a value e well below E. For example, 'e is of the order of two to four times lower than E. The central portion 2 of the polyethylene strip 1, which is bonded to the structure of the ski via a resilient foam support, may be, because of its relative thinness, considered flexible, while the two strips lateral 3, much thicker and directly integral with the structure of the ski, are rigid. To fix

2 6 1 5 7 46

  the ideas, E is for example equal to 1.5 millimeters, while e is

equal to 0.5 millimeters.

  FIG. 2 shows the stack in a mold of which

  felt the bottom 4 and side edges 5, constituent elements of this ski. The sole 1 and the two lower edges 6 are first laid. Then, on this sole 1 and between the edges 6, a layer 7 of elastic polyethylene foam is applied, the thickness of which before compression is much greater than E - e. Then, over the entire width of the ski, a rigid reinforcement 8 is applied, then the core 9 and the two side edges 10, and finally an upper layer 11 followed by a cover layer 12. The lid of the mold, not shown, is then put in place and strongly pressurized, which among other things strongly compresses the layer

elastic 7.

  After the conventional molding, demolding and finishing operations, the ski schematically has the appearance shown in section

  transverse to FIG. 3: the compressed foam 7 has, by swelling,

  the thin part 2 of the sole I downwards, so that the sole I of the ski has a central portion which has a slight recess

  d down, giving it a generally domed shape (this decree-

  was very exaggerated in Figure 3 for the sake of clarity).

  Part 2 and the foam 7 being flexible and elastic, the ski rests

  so on a kind of elastic cushion in extra thickness.

  Of course, this elastic cushion flattens completely if it presses strongly from bottom to top, for example under the shoe of the skier who shoes this ski: Figures 4 and 5 show the state of the ski under the shoe 13 of the skier , where the support is maximum. At the front 14 and at the rear 15 of the ski, the prop is smaller, so that the section

  ski takes the slightly convex shape of Figure 3.

  Of course, the invention is not limited to the example of realizing

  tion that has just been described. In particular, another material than polyethylene could be used both for the realization of

  the sole as that of the layer of elastic foam.

2 6 1 5 7 4 6

Claims (4)

CLAIMS I - Downhill ski comprising a sole (1) of constant profile on substantially the entire length of the ski, characterized in that this sole is made of flexible plastic material or semi-rigid and has a shaped shape conferring, in the vicinity of lower edges (6), a thickness (E) substantially greater than its thickness (e) on the remainder (2) of the width of the ski, and in that a layer (7) of an elastic material is interposed and compressed between the portion (2) of lesser thickness (e) of the sole (1) and a hard layer (8) placed above.   2 - downhill ski according to claim 1, characterized in   the profiled sole (2) is made of extruded polyethylene.   3 - Downhill ski according to claim i or the claim   2, characterized in that the elastic layer (7) is made of polyurethane foam   ethylene or rubber foam.   4 - Downhill ski according to one of claims I to 3, characterized   in that the thickness (E) of the two side strips (3) of the sole   (1) is several times greater than that of its central portion (2).   - Downhill ski according to one of claims 1 to 4, characterized   rised in that the thickness. before compression of the elastic layer (7) is several times greater than the difference (E - e) between the two thickness of the sole (1).   6 - Method for producing a ski according to one of the claims   I to 5, characterized in that it consists in producing, by extrusion of poly-   ethylene, a sole (1) which is profiled so as to have a flat base and a thickness which is, in the transverse direction, significantly higher on the edges (3) than in the middle part (2) remaining, then   to manufacture the ski by stacking under pressure in the mold of several cou-   ches, which necessarily this profiled sole (1), placed in the bottom (4) of the mold and bordered by the two lower edges (6), then a layer (7) of elastic foam, surmounting at least the portion (2) of sole of smaller thickness and having a thickness greater than   hollow (E - e) formed in this sole because of this lesser thickness.   median, and then at least one hard layer (8), such as a diaper rigid reinforcement.