EP0439713B1 - Cross-county ski for sliding - Google Patents

Description

The present invention relates to cross-country skis used for progression on snow according to the racing techniques on the bottom tracks, uphill, downhill and bumpy terrain.

Cross-country skis generally include a central portion arched between a front contact line and a rear contact line, with a front end region curved upward to form a spatula in front of the front contact line, and with a posterior end zone generally slightly curved upwards, behind the rear contact line.

When the cross-country ski is placed on a plane, by its lower sliding surface, at rest, it is supported on the plane by two transverse lines called the front contact line and the rear contact line. Between the two front and rear contact lines, the arched central part detaches from the support plane: from the front contact line, the distance increases progressively between the support plane and the underside of the ski, until it reaches a maximum in the central area of the ski, then this distance gradually decreases until it reaches the rear contact line.

For many years, the traditional long distance running technique, for progression on the flat and uphill, consisted of the alternative step. According to this technique, the two skis remain parallel to the direction of progression, the skier alternately resting on one ski to slide the other. In order for the support to be effective, in order to give a good forward impulse, we have always sought to give the ski a particular structure in which the camber of the central area of the ski has a relatively pronounced bend in its center: from the front contact line, the ski being placed on a plane, the traditional camber is such that the distance gradually increases along a slope which decreases slightly until it reaches the central area of the ski; in the central zone of the ski, the slope decreases very quickly, to reverse, and then decreases slightly when one moves in the direction of the rear contact line, until reaching this rear contact line. In the central area of traditional skis, the slope variation module is relatively constant and is of the order of 10⁻³ to 2.10⁻³ cm⁻¹. Thanks to this strong slope variation, such a camber traditional constitutes, in the vicinity of the central zone of the ski, a part which is slightly detached from the support plane when the skier is simply resting on his skis. To apply this central area against the support plane, it is necessary to give the ski a pulse from top to bottom according to a relatively large force.

Such a form of camber, with a pronounced bend, allows, in the traditional technique of alternative pitch, to reserve a central ski area having good qualities of grip on snow. Thus, in the absence of an impulse from top to bottom on the ski, the central adherent zone can remain slightly detached from the snow, and not oppose the sliding of the ski; on the other hand, by giving an impulse from top to bottom on the ski, the skier can apply the adherent central zone on the snow, and thus benefit from this adhesion to take support and progress forward.

To obtain good sliding qualities despite the presence of the central elbow, it has been necessary, in traditional cross-country skis, to provide particularly flexible ski ends. This flexibility can be characterized by subjecting the ski ends to bending under the action of a weight.

More recently, the long-distance running technique has evolved, and it is now moving towards progression by means of a skater's step. In this technique, the skier places his skis in directions slightly divergent with respect to the direction of progression, and pushes himself alternately from one ski to the other; at each step, one of the skis slides substantially flat while the other serves as a support and is therefore inclined to bite the inside edge.

However, it appears that traditional cross-country skis are not suitable for such a skating step technique.

In particular, the great flexibility of the front and rear ends of traditional ski does not allow to benefit from a good support on the inner edge to give an impulse in skater steps. And if you increase the rigidity of the ski, you get a cross-country ski whose sliding qualities are clearly insufficient, and are no longer compatible with the intended use.

The object of the present invention is in particular to design a new cross-country ski which is particularly well suited for new techniques of progression in skater steps.

The cross-country ski according to the invention presents the best compromise between the qualities of gliding flat, the qualities of gliding on an inner edge during the pulse in skater steps, and the qualities of attachment on the inner edge for the pulse in no skater.

To achieve these and other objects, a cross-country ski according to the present invention differs in particular from known skis in that the slope variation module is a constant value and its value is less than 9.10 9 cm⁻¹ in the central zone of the central part (1) when the ski is at rest.

According to another characteristic, in the central part zone located in the vicinity of the front contact line, the ski is more rigid than a traditional ski.

This combination of characteristics provides both good qualities of flat gliding, and good qualities of hooking on edge in support of a skater's step, gliding on edge being also excellent.

According to an embodiment of the invention, in the central part zone located in the vicinity of the rear contact line, the ski is also more rigid than a traditional ski.

A further improved quality of hooking on edge is obtained by additionally providing, on such a cross-country ski of the invention, an inner side face hollowed out such that the maximum distance between the side face and the rope connecting the end zones. of said lateral face is greater than about 1.25 millimeters. Good results are obtained for such a maximum distance of approximately 2.5 millimeters.

• les figures 1 et 2 illustrent le profil d'un ski traditionnel posé à plat sur un plan support, respectivement au repos et soumis à une force d'appui centrale ;
• les figures 3 et 4 illustrent le profil d'un ski selon la présente invention dans les mêmes conditions, ski au repos sur un plan, ski sur un plan et soumis à une force d'appui centrale ;
• la figure 5 illustre le profil d'un ski traditionnel lorsqu'il se trouve en appui sur une carre, pour impulsion en pas de patineur ;
• la figure 6 illustre le profil d'un ski selon l'invention lorsqu'il est également en impulsion sur carre pour pas de patineur ;
• la figure 7 illustre, a plus grande échelle, la courbe décrivant le profil d'un ski traditionnel au repos, donnant la distance entre la face inférieure de glisse du ski et un plan support en fonction de la position longitudinale considérée sur le ski ;
• la figure 8 illustre la pente de la face inférieure de glisse du ski traditionnel en fonction de la position longitudinale considérée ;
• la figure 9 représente la variation de pente de face inférieure de glisse du ski traditionnel en fonction de la position longitudinale considérée ;
• les figures 10 à 12 illustrent les mêmes courbes que les figures 7 à 9, pour un ski selon l'invention ;
• la figure 13 est une vue de dessus d'un ski de fond traditionnel ;
• la figure 14 est une vue de dessus d'un ski selon l'invention ;
• la figure 15 illustre le test de souplesse pour déterminer la souplesse de partie avant du ski ; et
• la figure 16 illustre le test de souplesse pour déterminer la souplesse de partie arrière du ski.

Other objects, characteristics and advantages of the present invention will emerge from the following description of particular embodiments, given in relation to the attached figures, among which:

• Figures 1 and 2 illustrate the profile of a traditional ski placed flat on a support plane, respectively at rest and subjected to a central support force;
• Figures 3 and 4 illustrate the profile of a ski according to the present invention under the same conditions, ski at rest on a plane, ski on a plane and subjected to a central support force;
• FIG. 5 illustrates the profile of a traditional ski when it is resting on an edge, for impulse in skater steps;
• FIG. 6 illustrates the profile of a ski according to the invention when it is also in pulse on edge for no skater;
• FIG. 7 illustrates, on a larger scale, the curve describing the profile of a traditional ski at rest, giving the distance between the lower sliding face of the ski and a support plane as a function of the longitudinal position considered on the ski;
• FIG. 8 illustrates the slope of the lower sliding face of the traditional ski as a function of the longitudinal position considered;
• FIG. 9 represents the variation in slope of the lower sliding face of the traditional ski as a function of the longitudinal position considered;
• Figures 10 to 12 illustrate the same curves as Figures 7 to 9, for a ski according to the invention;
• Figure 13 is a top view of a traditional cross-country ski;
• Figure 14 is a top view of a ski according to the invention;
• FIG. 15 illustrates the flexibility test to determine the flexibility of the front part of the ski; and
• FIG. 16 illustrates the flexibility test to determine the flexibility of the rear part of the ski.

As shown in FIGS. 1 and 3, a cross-country ski generally comprises a central arched part 1, connecting to a front end zone 2 bent upwards in the shape of a spatula, and to a rear end zone 3 generally raised upwards and forming a heel. When the ski is placed on a support plane 4, at rest, it rests along a front contact line 5 and a rear contact line 6 delimiting the central part 1.

The central zone of central part 1 has a concavity facing downwards, and is connected respectively, by a front inflection line 50 and a rear inflection line 60, to a front zone and to a rear zone of central part 1 whose concavities are turned upwards. Generally, the inflection lines 50 and 60 are not far from the respective contact lines 5 and 6.

In a traditional ski, as shown in FIGS. 1 and 2, the central zone 7 of the arched central part 1 has a relatively pronounced bend. In this way, when a user is supported by the ski, his weight constitutes a force 8 applied from top to bottom on the central zone 7 but, by the presence of the elbow of the zone central 7, this central zone does not touch the plane 4, as shown in FIG. 2. To make the central zone 7 touch on the plane 4, the user must apply an additional pulse. By providing such a central area 7 having attachment characteristics on the snow, either by a particular wax, or by the presence of scales, the user can, by an additional impulse, take advantage of the grip qualities of this area. central 7. On the other hand, in the normal sliding position, the weight of the user does not cause the central zone 7 to be pressed against the snow, and does not brake the ski.

On the other hand, as shown in FIG. 3, a ski according to the present invention comprises a central part 1, the central zone 7 of which does not have an elbow. In other words, the arched central part 1 has a variation in slope, the value of which is relatively small over the entire length of the central part 1 of the ski, this value being preferably less than 9.10⁻⁴ cm⁻¹, when the ski is at rest. . In this way, as shown in FIG. 4, when the user is resting on the ski, the force 8 applied to the central zone 7 is enough to make the ski flatten substantially along its entire lower surface on the plane 4. Thus, the camber of the central part 1 of a ski according to the present invention has a low flattening force, whereas a traditional cross-country ski requires a very large force for its flattening, due to the presence of the elbow in central area 7.

The differences in camber between a ski according to the present invention and a traditional cross-country ski are better explained in FIGS. 7 to 12, which make it possible to characterize the ski profiles between the front inflection line 50 and the rear inflection line 60. These figures represent, as a function of the longitudinal position considered along the ski, the different sizes which can characterize the camber. In Figures 7 and 10, there is shown the height H, or distance between the underside of the ski of the plane 4 on which the ski rests at rest. In a traditional ski, in FIG. 7, the central zone 7 has a relatively pronounced curvature while the zones adjacent to the ends are relatively flat; on the other hand, on a ski according to the invention, in FIG. 10, the variation in slope is substantially distributed over the entire length of the central part 1 of the ski and the profile of the central part 1 is similar to a parabola.

Similarly, in FIG. 8, for a traditional cross-country ski, the slope P of the lower face of the ski, or first derivative of the height H, has a relatively constant positive value in the zone A or zone before the ski, then a value decreasing rapidly in the central zone B, corresponding to the central zone 7 ski, then a relatively constant negative value in zone C or rear zone of the ski; on the other hand, in FIG. 11, a ski according to the present invention has a regularly decreasing slope P over the entire length of the central part 1 of the ski situated between the lines of inflection 50 and 60.

In FIG. 9, in a traditional cross-country ski, the variation in slope VP, or second derivative of the height H, has been represented. In the anterior zone A, this value is negative and low; in the central zone B, this value is strongly negative, and of modulus traditionally of the order of 10⁻³ to 2.10⁻³ cm⁻¹: in the posterior zone C, this value is weakly negative and constant; on the other hand, in FIG. 12, for a ski according to the invention, this value VP is constant and slightly negative, and of modulus less than 9.10⁻⁴ cm⁻¹.

In the central arched part 1, the maximum slope variation VP has a modulus advantageously equal to approximately 6.10⁻⁴ cm⁻¹.

In the central part zone 1 situated in the vicinity of the front contact line 5, a ski according to the present invention is relatively rigid compared to the rigidity that a traditional cross-country ski exhibits in the same zone. This rigidity can be obtained by any means well known in the state of the art, for example by providing, in the internal structure of the ski, reinforcing elements such as rigid material plates of appropriate thickness. The stiffness measurement obtained can be carried out by a test such as that shown in FIG. 15: a ski length L1, of 570 millimeters, starting from the front contact line 5, is retained at its two ends by free supports 9 and 10, while its center is subjected to a force 11 substantially perpendicular and of an intensity of 200 newtons; the central zone of this ski part located between the two free supports 9 and 10 moves elastically over a distance D1. The front contact line 5 is generally measured by introducing a cubic wedge 20 of 1 cm³ under the spatula and corresponds to the point 9.5 cm distant from the center of the wedge towards the middle of the ski. This theoretical determination is necessary to obtain good reproducibility of the measurements.
Similarly, the rear zone of a cross-country ski according to the present invention has a relatively high rigidity compared to that presented by a traditional cross-country ski. This rigidity can be obtained by any means such as the presence of an internal rigid reinforcement plate of the ski, these means being within the reach of those skilled in the art. The stiffness can be measured by a test shown in FIG. 16, similar to the test in FIG. 15, in which the posterior ski area situated on a length L2 of 570 millimeters from the rear contact line 6 of the ski, is resting on two free supports 12 and 13, its center being subjected to a substantially perpendicular force 14 and of an intensity of 200 newtons, the rear contact line 6 is, in general, measured at 5 centimeters from the rear end of the ski. This rigidity is significantly greater than that of traditional cross-country skis.

The effect obtained by this rigidity, combined with the absence of a bend in the central zone 7, is a very noticeable improvement in the qualities of edge grip and gliding on the edge. Figures 5 and 6 partially illustrate this effect; in FIG. 5, a traditional ski subjected to a push in edge grip takes a curved profile at its two ends, while its central zone remains bent; on the other hand, in FIG. 56, a ski according to the present invention, in the presence of a push bearing on the edge, has a substantially rectilinear profile, distributing the push over a maximum length of the ski. It will be readily understood that a ski according to the invention has much better sliding qualities on edge, by virtue of its substantially rectilinear shape.

We can further improve the hooking qualities on edge, to achieve a good support in no skater, by digging the side faces of the ski, or at least the inner side face or side face facing the other ski . This feature is illustrated in Figures 13 and 14; in FIG. 13, a traditional cross-country ski has two lateral faces 15 and 16 substantially parallel to one another. In other words, the width of the central part is very close to the width at the front part of the ski and the width at the rear part of the ski.

On the other hand, in FIG. 14, a ski according to the present invention advantageously has hollowed out lateral faces. For example, considering that the side face 15 is the inside face, facing the other ski not shown in the figure, the maximum distance D3 between the side face 15 and the rope 17 connecting the end zones of said face lateral 15 is, according to the invention, greater than about 1.25 millimeters. This maximum distance D3 is advantageously about 2.5 millimeters. This distance remains compatible with the standard forms of a traditional cross-country ski.

Such a hollowed face 15 according to the invention can be produced either on asymmetrical ski, that is to say one whose faces 15 and 16 have different shapes, or on a symmetrical ski in which the faces 15 and 16 are symmetrical by in relation to the median longitudinal plane of the ski.

For example, in Figure 14, there is shown such a symmetrical ski. In this case, the hollow side faces can also be characterized by the difference in ski widths; the difference between the width W1 of the ski at the front end and the width W2 of the ski in the central zone is greater than approximately 3 millimeters similarly, the difference between the width W3 in the rear zone of the ski and the width W2 in the central area of the ski is greater than approximately 2 millimeters. Good results are obtained by providing a difference in widths W1 and W2 equal to approximately 6 millimeters, and a difference between the widths W3 and W2 equal to approximately 4 millimeters.

For example, such a ski may have a central zone whose width W2 is approximately 43 millimeters, a front end zone whose width W1 is approximately 48 millimeters, and a rear end zone whose width W3 is about 46 millimeters.

The present invention is not limited to the embodiments which have been explicitly described, but it includes the various variants and generalizations thereof contained in the field of claims below.

Claims (7)

1. Cross-country ski, comprising:

   - an arched central portion (1) between a forward contact line (5) and a rear contact line (6), having a median zone connected by a forward inflection line (50) and a rear inflection line (60) spaced slightly from the respective contact lines (5, 6),

   - a front end zone (2), in front of forward contact line (5), curved upwardly in the shape of a shovel,

   - a rear end zone (3), behind rear contact line (6),

      characterized in that the slope variation modulus (VP) of the median zone of arched central portion (1) is a constant value when the ski is at rest, and this value is less than 9.10⁻⁴ cm⁻¹.
2. Cross-country ski according to claim 1, characterized in that the maximum slope variation modulus (VP) is approximately 6.10⁻⁴ cm⁻¹ in central zone (7) of arched central portion (1).
3. Cross-country ski according to any of claims 1 or 2, characterized in that it comprises a hollow, internal lateral surface (15) such that the maximum distance (D3) between lateral surface (15) and cord (17) connecting the end zones of said lateral surface (15) is greater than approximately 1.25 millimeters.
4. Cross-country ski according to claim 3, characterized in that said maximum distance (D3) is approximately 2.5 millimeters.
5. Cross-country ski according to any of claims 3 or 4, characterized in that:

   - the ski is substantially symmetrical,

   - the difference between width (W1) of the ski in the front end zone and width (W2) in the central zone of the ski is greater than approximately 3 millimeters,

   - the difference between width (W3) of the ski in the rear end zone and width (W2) in the central zone is greater than approximately 2 millimeters.
6. Cross-country ski according to claim 5, characterized in that the difference between said widths (W1) in the front zone of the ski and (W2) in the central zone of the ski is approximately 6 millimeters, whereas the difference between said widths (W3) in the rear zone of the ski and (W2) in the central zone of the ski is approximately 4 millimeters.
7. Cross-country ski according to claim 6, characterized in that:

   - the central zone of the ski has a width of approximately 43 millimeters,

   - the front end zone of the ski has a width of approximately 48 millimeters,

   - the rear end zone of the ski has a width of approximately 46 millimeters.

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