EP0657192B1 - Ski with a profile varying according to the position of the sliding surface - Google Patents

Abstract

The invention relates to a ski equipped with a running sole which has discontinuous striations (50, 70) and which comprises a central zone (5) for flat gliding and, on at least one side, a lateral zone (6, 7) for curved gliding, the latter bordering the central zone (5). The surface of the rear part at least of the central zone (5) included between the rear contact line (11) and the median boot line of the ski is equipped with a marked profile such that the measured values of the significant parameters of roughness Rtm and Rku are greater than the values measured on the surface of the said lateral zone (6, 7) for curved gliding. The invention relates more particularly to a downhill (alpine) ski whose turning and gliding capabilities are improved. <IMAGE>

Description

The invention relates to a ski for evolution on snow, such as an alpine ski, a monoski or snowboard.

It relates more particularly to a ski provided with a lower sole topped with streaks, whose sliding ability has been improved.

Specialists know that to get the ski to slide properly, the sole in contact with snow should not be perfectly smooth. Under the influence of friction and the pressure exerted, the snow grains melt and transform into microdroplets which tend to clump together and form a film lubricating water. It is therefore important to carry out a structuring allowing the rupture and evacuation of this film of water to avoid the suction phenomena which oppose slippage.

This observation made it possible to see the publication of a certain number of patents presenting more or less empirical solutions in response to problems posed by the phenomenon.

In document CH 161 592, the sole is provided in its central part a multitude of parallel and straight grooves which extend so continues for about a third of the length and across the full width of the surface of slips.

The downside is that you get a very directive ski which is difficult to initiate turns at high speed. For that, we thought of shortening the length of the grooves and group them in rows separated from each other as in document FR-A-2 654 005. In this solution, the structure of surface combines the effect of the formation and adequate guidance of the layer of water and on the other hand the appropriate rupture of the layer of water, without giving the ski of major directive effect.

Finally, in document FR-A-2 683 730, the sliding surface is provided with ridges discontinuous oriented in the longitudinal direction whose shape is wavy, of pace generally sinusoidal, so as to preferably give the sole a roughness coefficient Ra within an appropriate value range.

In all the solutions of the prior art, we have focused mainly on work on the shape, length and orientation of the streaks without worrying about the question of what were the optimal areas to receive such structuring and which areas were better not to structure. The object of the present invention is to provide a satisfactory solution to these problems.

The Applicant has in fact found that there exists at a surface of sliding of the stressed areas differently on snow, and that consequently the structure had to be adapted to take this into account.

The central region of the sole plays an important role in the flat gliding of the ski, so it is important that it is strongly structured to allow good flow and avoid the suction phenomenon.

When cornering, the ski is tilted by the skier on either edge lateral. The sole therefore remains in contact with the snow on a lateral region of narrow width bordering the central region. The pressure exerted by the weight of the skier on this small surface is therefore large and it is therefore important to minimize friction by providing a smooth surface or less marked structure. We must, in fact, favor the support properties and edge hooking while reducing the "guiding" effects due to the structure of the sole that can oppose cornering. The problem with the water film is secondary in this configuration.

The invention therefore aims to provide a ski for evolution on snow comprising a lower surface of variable width (L) made of plastic, provided with a plurality of discontinuous stripes and two lateral edges which border laterally said surface; which is based on a front contact line and a rear contact line when the ski is unloaded. The lower surface includes a central flat glide area extending between the two lines of contact, and on at least one side, a curved sliding side zone bordering said central zone between the two contact lines, the width (l1) of which is greater than 0.03 L; the surface of the rear part at least, of said zone center, between the rear contact line and the center line of ski boot, being provided with a marked structure such that the values measured significant roughness parameters Rtm and Rku are greater than values measured on the surface of said lateral sliding curve area.

Preferably, the lower surface comprises two symmetrical lateral zones relative to the longitudinal axis of the ski, bordering on both sides the central area.

The parameters Rtm and Rku used are those among the roughness parameters which make it possible to best appreciate on a surface the difference between a strong or marked structuring effective for breaking and evacuating the water film according to the invention and a finer or less marked structure limiting friction with snow when cornering.

The Rtm parameter designates the average of the maximum roughnesses which measure the vertical distance between the highest point and the lowest point of the roughness profile over the total evaluation length, according to DIN 4762 / 1E or ISO 4287/1.

The Rku (Roughness Kurtosis) parameter designates the flattening parameter of the density of height distribution. The flatter the density curve, the more Rku is great; on the contrary, if the curve is pointed and its maximum well centered, Rku is low (ISO Standard 4287/1).

In particular, the Rtm value is less than or equal to 15 µm and the Rku value is less than or equal to 3 in the surface of said lateral zone (s), then that Rtm> 15 µm and Rku> 3 in the rear part, at least, of the central zone as defined above.

According to another characteristic, the width (l1) of the lateral zone (s) is between 0.03 L and 0.3 L, knowing that the width (l2) of the central zone of sliding flat must remain greater than or equal to 0.45 L.

Advantageously, the width (l1) of the lateral zone (s) increases from from the vicinity of the minimum bottom surface width line (L min), in direction of contact lines. Indeed, it is advantageous to reserve a surface more or less striated at the ends in order to improve the easy pivoting of the ski. Thus, it is preferable that the width (l1) is greater than or equal to 2 mm in the vicinity of the surface width line lower (L min) and is greater than or equal to 10 mm in the vicinity of the lines of ski contact.

According to a characteristic linked to the previous one, the width (l2) of the central zone strongly striated is constant. Such a structure can thus be easily obtained by a repetitive and reproducible technique using the passage on the sole of a tool in a single pass.

According to an additional characteristic, the structuring of the central area is achieved by passing a tool under the hot and pressurized sole shape of a roll comprising a relief pattern with constant width (l) of edges on the surface of which a plurality of discontinuous ribs is formed.

According to an alternative characteristic, the width (l1) of the area (s) lateral (s) is constant and the width (l2) of the central zone of sliding flat gradually increases from the vicinity of the minimum width (L min) in direction of contact lines.

In this case, it is preferable that the width (l1) of the lateral zone (s) is greater than or equal to 6 mm.

According to another more general characteristic, the central zone strongly structured comprises a plurality of short, straight and discontinuous streaks, arranged in separate or nested rows.

According to an additional characteristic, at least a majority of streaks are oriented along the longitudinal axis of the ski. Some may, however, be inclined and present an angle relative to the longitudinal axis, so in particular to avoid an excessive rail effect or to improve the release of the water film in certain snow conditions or for certain types of skis.

We can also foresee that the structuring presents a roughness gradient such that the measured parameters Rtm and Rku gradually increase from the edge towards the longitudinal axis over at least a significant part of the width of the lower surface being understood that the roughness (Rtm and Rku) can remain substantially constant over small portions of width. This may be the case, for example, by predicting a gradual increase in streak density, an increase in certain streak parameters (depth, width, length, shape, etc.).

Similarly, it may be preferable to consider that the structuring along the axis longitudinal has a roughness gradient such that the measured parameters Rtm and Rku vary gradually, from the rear contact line towards of the front contact line, over at least a substantial part of the length ski ; it being understood that the roughness can remain substantially constant over certain portions of length.

• la figure 1 représente une première forme de réalisation de la surface de glisse selon l'invention en vue de dessous du ski ;
• les figures 1a et 1b sont des vues à plus grande échelle de détails de la figure 1 ;
• la figure 2 illustre le ski de la figure 1 en prise de virage en vue de coupe ;
• les figures 3 et 4 montrent un exemple de réalisation de la structuration de la semelle d'un ski de la figure 1 ;
• la figure 5 est une seconde forme de réalisation de la surface de glisse selon l'invention en vue de dessous comparable à la vue de la figure 1 ;
• la figure 6 est une autre forme selon une variante de la figure 5 ;
• la figure 7 est une autre forme selon une autre variante ;
• les figures 8 à 10 sont des exemples variés de structuration en vue de détail selon l'invention.

Various other characteristics of the invention will emerge from the description which follows according to nonlimiting examples of making a ski in accordance with the invention, with reference to the appended schematic drawings including:

• FIG. 1 represents a first embodiment of the sliding surface according to the invention in view from below of the ski;
• Figures 1a and 1b are enlarged views of details of Figure 1;
• Figure 2 illustrates the ski of Figure 1 in cornering for cutting;
• Figures 3 and 4 show an embodiment of the structure of the sole of a ski of Figure 1;
• Figure 5 is a second embodiment of the sliding surface according to the invention in bottom view comparable to the view of Figure 1;
• Figure 6 is another form according to a variant of Figure 5;
• Figure 7 is another form according to another variant;
• Figures 8 to 10 are various examples of structuring in detail according to the invention.

In the example illustrated in FIG. 1, it is an alpine type ski with a view to below, where we can see the bottom surface or gliding sole (1) in polyethylene, the side edges (2), the tip (3) and the heel (4).

The sole is arched and rests on a front contact line (10) and a rear contact line (11) when the ski is unloaded. By the weight of the skier, the area between these two contact lines (10, 11) meets the snow and becomes the so-called "bearing" surface of the ski.

A central zone (5) known as "gliding flat" is formed on the bearing surface, of width (l2) in which a significant structuring is carried out. Figure 1a shows, in enlarged view, an example of significant structuring according to the invention. It can be a multitude of short straight (50), discontinuous and arranged in rows nested one inside the other.

The bearing surface comprises, on either side of the central zone (5), two lateral zones (6, 7) of sliding in curve, of width (l1). These areas have a less marked structure in which the streaks (70) are more spaced, more short, shallower and narrower, for example, than those in the area central (Figure 1b). Structuring could also be almost non-existent and the surface as smooth as possible.

Figure 2 shows the ski when a turn is engaged and its inclination by compared to the surface of the ground. Part of the sole penetrates more or less deep in snow or ice, depending on conditions, thanks to the cut exercised by the edge (2). We understand the usefulness of reserving a length zone (7) (11) of the bearing surface having a minimum of friction with the snow; the central zone (5) of length (l2) almost never being in contact with the snow during the turn.

In the example illustrated, as in all cases of the invention, the width (L) of the sole varies to follow the side line of the ski. The width (l1) is always greater than 0.03 L, at any point of width (L) of the sole, measured between the contact lines (10, 11). Preferably, (l1) is between 0.03 L and 0.3 L, knowing that (l2) must remain greater than or equal to 0.45 L. For example, on a traditional alpine ski, (l1) can be between 3 mm and 25 mm, approximately and (l2) is greater than 27 mm.

In the example illustrated, (l2) is constant between the contact lines (10, 11) and thus (11) varies gradually. In particular, from the widest width (L) small (L min), located near the middle of the bearing surface, the width (l1) of each lateral zone (6, 7) gradually increases towards the lines contact (10, 11).

• profondeur des stries : comprise entre 0,02 mm et 0,08 mm ;
• longueur des stries : comprise entre 10 mm et 60 mm ;
• largeur des stries : comprise entre 0,1 mm et 0,3 mm ;
• motif : rangées imbriquées ;
• coefficient Rtm : compris entre 20 µm et 80 µm ;
• coefficient Rku compris entre 5 et 35

During tests on snow, the Applicant has noticed that the following surface characteristics of the central zone (5) bring satisfactory results on snow:

• streak depth: between 0.02 mm and 0.08 mm;
• length of the streaks: between 10 mm and 60 mm;
• width of the streaks: between 0.1 mm and 0.3 mm;
• pattern: nested rows;
• coefficient Rtm: between 20 µm and 80 µm;
• coefficient Rku between 5 and 35

The roughness parameters are measured perpendicular to the axis longitudinal of the ski; just like the width measurements L, l1, l2.

Figures 3 and 4 illustrate an advantageous example for performing the structuring of the sole of a ski according to the invention and more particularly in the case where it is desired to obtain a constant width (l2) of the central zone (5) of the lower surface giving a variable width (l1) of the lateral zones (6, 7).

For this, a device is used comprising a heated tool (8) having the form of a roller and which has on its surface a relief pattern with constant width (l) edges, comprising a plurality of discontinuous ribs (80). The surface of the roller is applied, under pressure, against the surface of the sole (1) of the ski to prepare by operating a longitudinal scrolling of the ski between several skids of guide (9). One can also provide for immobilization of the ski and the movement of the tool compared to skiing, as a completely equivalent means. Depending on the nature of the material constituting the sole and the dimensions of the streaks to be produced; we adapt without particular difficulties the pressure and temperature conditions, so obtain satisfactory and reproducible results.

By way of nonlimiting example, for a HDPE type sole and in the case of making streaks according to the characteristics given previously as for example, it is preferable to work at a temperature between 80 and 120 ° C, and apply pressure on the sole surface by the rotating tool (8).

In such a process, it is not necessary to carry out several passages of the tool on the surface. On the other hand, it is not excluded to rework the surface by a finishing process allowing microstructuring on the whole the sole, such as by techniques well known to those skilled in the art, like by grinding with stone, for example.

FIG. 5 shows a variant of the invention in which the width (l1) of the lateral zones of sliding in curve is constant along the ski. Because of the coast line of the ski which gives the lower surface a width (L) which is variable shape of "wasp waist" the width (l2) of the central flat glide area is also variable along the ski and increases from the vicinity of the line of width (L min) towards the contact lines (10, 11) of the ski.

In FIG. 6, only the rear part of the central zone (5), lying between the rear contact line (11) and the shoe center line (12) is provided with streaks. The shoe center line (12) is a line given by each manufacturer and its position in relation to the ski environment can vary from one type of ski to the other.

The front part between the front contact line (10) and the middle line shoe (12) is slightly or not striated so that the roughness parameters Rtm, Rku defined in the front part are close to the values or equal to respective values of the lateral zones (6, 7) of sliding in curve. Tests performed by the applicant have demonstrated that such a configuration may be more effective in certain snow conditions.

In the case of FIG. 7, the structuring of the central zone (5) presents a roughness gradient such that the measured parameters Rtm and Rku decrease gradually, from the rear contact line (11) towards the line front contact (10). This gradient can be obtained for example by making gradually reduce the number of streaks and their size (length, width and depth) from the rear line (11) to the front line (10).

It can be agreed that over certain short portions of the length (ΔL) of the lower surface, the Rtm and Rku values can be substantially constant in the central area (5). Thus, it can advantageously be provided that the decreasing progression of the values Rtm and Rku is done in stages, i.e. by a series of adjacent short portions in which the values Rtm and Rku are substantially constant but vary from one portion adjacent to the other.

• des stries (50) parallèles et disposées en rangées séparées, orientées longitudinalement (figure 8) ;
• des stries parallèles en rangées imbriquées, orientées longitudinalement (figure 9) ;
• des stries parallèles orientées longitudinalement (50a) et d'autres inclinées (50b) (figure 10).

FIGS. 8 to 10 show nonlimiting examples of positioning of the ridges on the sliding surface according to the invention. Among the streaks lining the surface, we can have:

• parallel ridges (50) arranged in separate rows, oriented longitudinally (FIG. 8);
• parallel streaks in nested rows, oriented longitudinally (Figure 9);
• parallel grooves oriented longitudinally (50a) and others inclined (50b) (Figure 10).

The length of the streaks can vary, in general, between 4 mm and 50 mm depending on the type of snow and type of ski used.

Of course, the invention cannot be limited only to the modes of realization described and represented, but it also includes all the technical equivalents and their combinations which may be included in the The scope of the following claims.

Claims (14)

1. Snow ski comprising a lower surface (1) having a variable width (L) made of a plastic material, equipped with a plurality of discontinuous serrations (50, 70) and two side running edges (2) that laterally border said surface (1), said surface resting on a forward contact line (10) and a rear contact line (11) when the ski does not carry a load, the lower surface (1) comprising a central flat gliding zone (5) extending between both contact lines (10, 11) and, at least on one side, a lateral curved gliding zone (6, 7) bordering said central zone (5) between both contact lines whose width (l1) is greater than 0.03 L, the surface of the rear portion at least, of said central zone (5), comprised between the rear contact line (11) and the boot center line (12) of the ski, being provided with a pronounced structuring such that the measured values of the significant roughness parameters Rtm and Rku are greater than the values measured on the surface of said lateral curved gliding zone (6, 7).
2. Ski according to claim 1, characterized in that the lower surface comprises two lateral zones (6, 7) that are symmetrical with respect to the longitudinal axis of the ski, bordering said central zone (5) on both sides.
3. Ski according to claim 1 or 2, characterized in that the Rtm value is less than or equal to 15 µm and the Rku value is less than or equal to 3 in the surface of said lateral zone(s) (6, 7), whereas Rtm > 15 µm and Rku > 3 in the rear portion, at least, of said central zone (5).
4. Ski according to any of claims 1, 2, or 3, characterized in that the width (l1) of the lateral zone(s) (6, 7) is comprised between 0.03 L and 0.3 L, considering that the width (l2) of the central flat gliding zone is greater than or equal to 0.45 L.
5. Ski according to any of the preceding claims, characterized in that the width (l1) of the lateral zone(s) (6, 7) increases from the vicinity of the minimum lower surface width line (L min), in the direction of the contact lines (10, 11).
6. Ski according to claim 5, characterized in that the width (l2) of the strongly serrated central zone (5) is constant.
7. Ski according to claim 5 or 6, characterized in that the width (l1) of the lateral zone(s) (6, 7) is greater than or equal to 2 mm in the vicinity of the minimum width line (L min) and (l1) is greater than or equal to 10 mm in the victory of said contact lines (10, 11),
8. Ski according to any of claims 1-4, characterized in that the width (l1) of the lateral zone(s) (6, 7) is constant and the width (l2) of the central flat gliding zone (5) increases progressively from the vicinity of minimum width (L) in the direction of contact lines (10, 11).
9. Ski according to claim 8, characterized in that the width (l1) of the lateral zone(s) (6, 7) is greater than or equal to 6 mm.
10. Ski according to any of the preceding claims, characterized in that the strongly structured central zone (5) comprises a plurality of short, rectilinear and discontinuous serrations (50), arranged in separate or meshed rows.
11. Ski according to claim 10, characterized in that a majority, at least, of the serrations (50) are oriented along the longitudinal axis of the ski.
12. Ski according to any of the preceding claims, characterized in that the structuring has such a roughness gradient that the measured Rtm and Rku parameters increase progressively from the running edge (2) towards the longitudinal axis, at least over a significant portion of the width (L) of the lower surface, considering that the roughness (Rtm, Rku) can be substantially constant over small width portions.
13. Ski according to any of the preceding claims, characterized in that the structuring along the longitudinal axis has such a roughness gradient that the measured parameters Rtm and Rku vary progressively, from the rear contact line (11) towards the forward contact line (10), over a substantial portion, at least, of the length of the ski, considering that the roughness can be substantially constant over certain length portions (ΔL).
14. Method for making a ski according to claim 1, characterized in that the structuring of the central zone (5) is obtained by passing a heated and pressurized tool (8) over the sole (1), said tool having the shape of a roller comprising a raised design of a constant edge width (l) on the surface from which a plurality of discontinuous ribs (80) are formed.

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