EP0806228A1 - Ski - Google Patents

Abstract

The ski consists of a body (2) with a supporting surface defined by front and rear contact lines (A,D') and a central zone (ZRC) of more or less constant thickness (E) and a length which is more than 40 per cent of the length (Lp) of the supporting surface. It has two zones (ZA and ZED) of variable thickness, located before and after central zone. The length of the central zone is between 600 and 900 mm, and its thickness is between 22 and 35 mm, or between 15 and 30 mm. The central zone of the ski can be made from one piece of material or in two layers, with the forward and rear sections joined to it by strips of a visco-elastic material.

Description

Technical area

The invention relates to the field of alpine skiing and cross-country skiing. It relates more particularly to an improved geometry in which the variation in thickness of the ski over the length thereof gives very significant gliding properties.

Previous techniques

In general, a ski can be compared to a beam or a board slightly curved longitudinally to form the camber of the ski, with a front part raised to form the tip and a rear part also slightly raised to form the heel. The ski being laid flat on the snow, and under the effect of the skier's load, the bottom surface or sole remains in contact with the snow from the front contact line to the rear contact line. The distance between the front and rear contact lines determines the "bearing length" of the ski.

The geometry of this beam is precisely determined to give the ski the desired behavior, in particular in bending and in torsion. Thus, in general, the beam or the board has a certain flexibility which allows it to follow the shape of the ground. The flexibility characteristics largely result from the variation in thickness of the board between the front and rear contact lines. In all skis known to date, the thickness of the ski increases continuously from the front contact line to the area of the skate in which it is maximum. This thickness then decreases continuously up to the rear contact line. Such a geometry is for example described in patent FR 2 700 476 in the case of a cross-country ski.

This thickness distribution generally combines with a variation in width of the ski according to its length, to give the latter a specific behavior.

This is how an alpine ski will be determined to achieve large curves or tight turns, to absorb fields of bumps or to evolve on smooth tracks, or to slide off piste on virgin snow. For cross-country skiing, it will either be designed to slide flat for "classic" practice, or designed to hang on the ridge for "no skater".

In general, the pressure exerted on the snow for a ski is maximum at the level of the skate, near the skier's foot, then decreases progressively until it vanishes in the vicinity of the ends.

The shape of this pressure distribution curve is mainly linked to the variation in thickness along the ski. The overpressure zone of the skate has a negative influence on the sliding characteristics of the board.

In other words, there is a certain incompatibility between the flexibility characteristics necessary for the registration of the ski in the turn with an optimization of the sliding qualities of the sole.

The problem which the invention therefore proposes to solve is to significantly increase the sliding characteristics of a ski without modifying its dynamic behavior.

Statement of the invention

The invention therefore relates to a ski intended for the practice of alpine skiing or cross-country skiing, formed of a body and the sole of which has a bearing surface of length Lp delimited at the front and at the rear by the lines of contact respectively before A 'and rear D', and whose thickness is E _A at the level of the front contact line A 'and E _D at the level of the rear contact line D'.

• la surface portante se décompose en trois zones contiguës à savoir :
  • une zone centrale Z_BC d'épaisseur E sensiblement constante et dont la longueur L_BC est supérieure à quarante pourcent (40%) de la longueur Lp de la surface portante;
  • deux zones avant Z_AB et arrière Z_CD d'épaisseur variable, localisées respectivement en avant et en arrière de la zone centrale Z_BC, et de longueurs L_AB et L_CD,
• en ce que le quotient $\frac{{\mathit{\text{E - E}}}_{\mathit{\text{A}}}}{{\mathit{\text{L}}}_{\mathit{\text{AB}}}}$
  
  de la différence d'épaisseur (E-E_A) du ski entre les points extrêmes (A,B) de la zone avant Z_AB, divisée par la longueur (L_AB) de la même zone est compris entre zéro virgule zéro un (0,01) et zéro virgule un (0,1);
• et en ce que le quotient $\frac{{\mathit{\text{E -E}}}_{\mathit{\text{D}}}}{{\mathit{\text{L}}}_{\mathit{\text{CD}}}}$
  
  de la différence d'épaisseur (E-E_D) du ski entre les points extrêmes (C,D) de la zone arrière, divisée par la longueur (L_CD) de la même zone est compris entre zéro virgule zéro un (0,01) et zéro virgule un (0,1).

This ski is characterized in that:

• the bearing surface is divided into three contiguous areas, namely:
  • a central zone Z _BC of thickness E substantially constant and whose length L _BC is greater than forty percent (40%) of the length Lp of the bearing surface;
  • two zones before Z _AB and rear Z _CD of variable thickness, located respectively in front and behind the central zone Z _BC, and of lengths L _AB and L _CD ,
• in that the quotient $\frac{{\mathit{\text{E - E}}}_{\mathit{\text{AT}}}}{{\mathit{\text{L}}}_{\mathit{\text{AB}}}}$
  
  of the difference in thickness (EE _A ) of the ski between the extreme points (A, B) of the area before Z _AB , divided by the length (L _AB ) of the same area is between zero point zero one (0, 01) and zero point one (0.1);
• and in that the quotient $\frac{{\mathit{\text{E -E}}}_{\mathit{\text{D}}}}{{\mathit{\text{L}}}_{\mathit{\text{CD}}}}$
  
  the difference in thickness (EE _D ) of the ski between the extreme points (C, D) of the rear zone, divided by the length (L _CD ) of the same zone is between zero point zero one (0.01) and zero point one (0.1).

In other words, the invention consists in giving the ski a constant thickness in its central part, to ensure a uniform distribution of the pressure exerted on the snow.

Concomitantly, in order to keep the qualities of flexibility necessary for good dynamic behavior and registration when cornering, the zones situated in front and behind the characteristic intermediate zone are of decreasing thickness up to the contact lines.

In other words, unlike all the embodiments in accordance with the prior art in which the thickness of the ski is continuously variable, a ski according to the invention has in its central zone an upper face parallel to the sole.

Of course, the invention is not limited to skiing in which the thickness of the intermediate zone is strictly constant, but also covers the embodiments in which this thickness is substantially constant. By "substantially" constant is meant that the maximum difference in thickness at two points in this intermediate zone is at most equal to five percent (5%) of the total thickness.

It has been observed that good results are obtained in terms of gliding in the case where the length of constant thickness is between six hundred milllimeters (600 mm) and 900 millimeters (900 mm).

As already said, the invention relates to narrow skis used for cross-country skiing or for alpine skiing, on which the user's foot is positioned along the longitudinal axis.

Thus in the case of cross-country skiing, it has been observed that a good improvement in sliding behavior is obtained when the thickness E of the intermediate zone Z _BC is between twenty two millimeters (22 mm) and thirty five millimeters (35 mm).

Similarly, in the case of alpine skiing, similar results are observed when the thickness E of the intermediate zone Z _BC is between fifteen millimeters (15 mm) and thirty millimeters (30 mm).

In this way, each ski of a pair being stressed independently during a turn for an alpine ski or in momentum for a cross-country ski, the pressure exerted by the sole of the boot is retransmitted so uniform over the entire carrying length of the ski. The zone of constant thickness due to its stiffness plays a sort of pressure distributing role, which improves the sliding capacity.

As already mentioned, to maintain good load progressiveness, it is important that the thickness of the ski decreases from the characteristic intermediate zone to the front and rear contact lines.

Thus, on a cross-country ski, good dynamic behavior was observed when the quotient of the difference in thickness (EE _A ; EE _D ) of the ski between the extreme points (A, B; C, D) of each front zone Z _AB and back Z _CD , divided by the length (L _AB ; L _CD ) of the same area is between zero point zero three (0.03) and zero point zero nine (0.09). $$\text{In other words, 0.03 ≤}\frac{{\mathit{\text{E - E}}}_{\mathit{\text{AT}}}}{{\mathit{\text{L}}}_{\mathit{\text{AB}}}}\text{≤ 0.09 and 0.03 ≤}\frac{{\mathit{\text{E - E}}}_{\mathit{\text{D}}}}{{\mathit{\text{L}}}_{\mathit{\text{CD}}}}\text{≤ 0.09}$$

≤ 0,03 et 0,01 ≤ $\frac{{\mathit{\text{E -E}}}_{\mathit{\text{D}}}}{{\mathit{\text{L}}}_{\mathit{\text{CD}}}}$

≤ 0,03Similarly, good dynamic behavior of an alpine ski was observed when the quotient of the difference in thickness (EE _A ; EE _D ) of the ski between the extreme points (A, B; C, D) of each zone front Z _AB and rear Z _CD , divided by the length (L _AB ; L _CD ) of the same area is between zero point zero one (0.01) and zero point zero three (0.03). In other words, 0.01 ≤ $\frac{{\mathit{\text{E - E}}}_{\mathit{\text{AT}}}}{{\mathit{\text{L}}}_{\mathit{\text{AB}}}}$

≤ 0.03 and 0.01 ≤ $\frac{{\mathit{\text{E -E}}}_{\mathit{\text{D}}}}{{\mathit{\text{L}}}_{\mathit{\text{CD}}}}$

≤ 0.03

Concerning the realization of the characteristic intermediate zone, several designs respect the principle of the invention.

Thus, in a first embodiment, the intermediate zone Z _BC is constituted by a monobloc part of the beam.

In a second embodiment, the intermediate zone Z _BC is constituted by the superposition of a part of the beam and of an upper element surmounting it.

In other words, the upper face of the ski receives in the characteristic intermediate zone a rigid plate which ensures uniform transmission over its entire length of the weight and the impulses generated by the skier, so that the distribution of the pressure exerted on the snow as uniform as possible over the entire length of the characteristic intermediate zone.

In a first embodiment, the entire length of the upper element is glued to the beam.

In a sophisticated variant, the central part of the upper element is glued to the beam and the front and rear extreme parts of the reinforcing element are connected to the beam by strips of visco-elastic material. This makes it possible to reduce the stresses at the ends of the upper element and to benefit from phenomena of damping by shearing of the viscoelastic bands.

Concerning the geometry of the extreme zones of the upper element, several variants can be envisaged.

Thus, the extreme front and rear parts of this upper element may have vertical sections, corresponding to a thickness step. These end portions may also have inclined faces in the direction of the front and rear contact lines respectively, so as to ensure a continuous thickness variation without breakage.

The upper element can take different forms which prove to be interesting, either to manufacture or under the conditions of use.

Thus, in a first variant, the front and rear end portions of the upper element have inclined faces in the direction of the contact lines respectively before A 'and rear D'.

In other words, the upper element is seen from above in a generally rectangular shape.

In a second form variant, the front and rear end portions of the upper element conform to a V shape, the point of which is directed towards the outside of the upper element.

In a variant intended to distinguish the behavior of left and right skis, the front and rear end portions of the upper element form, in top view, two non-parallel lines.

According to two construction variants, the beam and the upper element can either be both of constant thickness, or be of complementary shapes so that the thickness of the assembly is of constant thickness. In the latter case, the upper beam and element can be convex or concave.

Brief description of the drawings

The manner of carrying out the invention, as well as the advantages which result therefrom, will emerge clearly from the description of the embodiments which follow, supported by the appended figures in which:

Figure 1 is a side view of a ski according to the invention, in which the proportions have been exaggeratedly modified to allow a good understanding of the dimensional criteria characteristic of the invention.

Figure 2 is a side view of a ski according to an alternative embodiment.

Figure 3 is a side view of a detail of the connecting area of the intermediate and front areas characteristic of the invention.

FIG. 4 is an alternative embodiment of FIG. 3.

Figures 5 to 7 are top views of skis having characteristic upper elements in three form variants.

FIG. 8 is a detail side view of the intermediate zone of a ski equipped with an upper element connected to the upper face of the ski in part by strips of viscoelastic material.

Ways to realize the invention

As already said, the invention relates to a ski, cross-country or downhill, which has over its length, a characteristic thickness variation.

In known manner, a ski (1) consists mainly of a beam (2) whose lower face (3) forms the sole.

Only the part of the sole (3) between the front contact line (A ') and the rear contact line (D') is intended to come into contact with snow. The front part of the front contact line (A ') is raised upwards and constitutes the tip (4) while the rear part of the front contact line (D') is also raised, but to a lesser extent. degree and constitutes the heel (5) of the ski (1).

In known manner, the thickness of the ski at the contact lines is less than the thickness measured in the bearing surface.

In FIG. 1, the thicknesses at the front (A ') and rear (D') contact lines are denoted E _A and E _{D respectively} .

According to an essential characteristic of the invention, the bearing surface, of length Lp, breaks down into three contiguous zones, namely: a central zone Z _BC, framed by two zones respectively before Z _AB and Z _CD .

According to the invention, the central zone Z _BC extends over at least forty percent (40%), and preferably fifty percent (50%) of the length Lp of the bearing zone, and has a substantially constant thickness E .

Thus, in this central zone Z _BC , the upper face (6) of the ski and the sole (3) are substantially parallel.

As already said, by "substantially" constant, it is meant that the maximum difference between the thicknesses measured on two points of this central zone Z _BC is at most equal to five percent (5%) and preferably less than one percent (1%) of the total thickness E, while this difference is greater than 25% and 10% respectively on a cross-country ski and an alpine ski in accordance with the Prior Art.

According to another essential and dissociable characteristic of the invention, the variation in thickness on the zones before Z _AB and Z _CD , also meets precise criteria.

≤ 0,1Thus, concerning the front zone, the quotient of the difference in thickness by the length is between 0.01 and 0.1, that is to say: 0.01 ≤ $\frac{{\mathit{\text{E - E}}}_{\mathit{\text{AT}}}}{{\mathit{\text{L}}}_{\mathit{\text{AB}}}}$

≤ 0.1

Geometrically, this means that the ski being placed with its sole (3) flat on a horizontal plane, the slope between points A and B is between one percent (1%) and ten percent (10%).

These dimensional parameters can be transposed to the rear zone Z _CD .

By way of example, it is considered that on a ski (1) of size 183 centimeters, the length Lp of the bearing zone being 158 centimeters, the intermediate zone Z _CD may have a length greater than 630 mm and more favorably 800 millimeters.

Furthermore, the thickness E of this same area must be between 15 and 35 millimeters, while the thickness E _A , E _D at the front and rear contact lines can vary at the same time between 4 and 12 millimeters .

According to another important characteristic of the invention, the intermediate zone of constant thickness can be constituted either by a very portion of the beam (2), or be formed by the association of the beam and an upper element (10 ) arranged on the upper face (6) of the ski.

In the case where the intermediate zone Z _BC is in one piece, it may or may not be seen there as a break in curvature at the points B and C constituting the limits of the intermediate zone, or else ensuring a smooth transition easier to manufacture.

As seen in Figures 3 and 4, the upper element may have ends (11, 12) of various geometries. Thus, one can consider giving this end (11) a vertical pan shape (13) or else a beveled shape (14) ensuring a gradual thickness variation over a short transition range.

Thus, we see in Figures 5 to 7, that the upper element (10) can take various advantageous forms.

Thus, in a first variant, the upper element (10) has a substantially rectangular shape, and the end portions (11, 12) end in straight segments (16, 17), mutually parallel and perpendicular to the median longitudinal plane ski.

In another variant, illustrated in FIG. 6, the extreme parts (11, 12) of the upper element (10) follow herringbone shapes (18, 19) oriented by the ends of the ski. This allows the pressure distributing effect of the upper element (10) to be extended forwards and backwards.

In a variant illustrated in FIG. 7, the ends (11, 12) of the upper element (10) conform to the shapes of straight segments (20, 21) which, the extensions of which converge, on one side of the ski, substantially at the median length of the upper element (10). This creates an asymmetry between the left and right ski.

As can be seen in FIG. 8, the upper element (10) can be connected to the upper face (6) of the ski by gluing or other equivalent means, as illustrated only in its middle part.

In this case, the front and rear parts of the reinforcing element (10) are connected to the upper face (6) of the ski by strips of viscoelastic materials (25, 26), which allows a uniform distribution of pressure while by ensuring a damping effect by shearing of the viscoelastic material.

It appears from the foregoing that a cross-country or downhill ski in accordance with the invention has, thanks to its variation in thickness over its length, gliding qualities clearly superior to that of skis existing hitherto.

By surprising effect, the dynamic behavior and in particular the entry in the curve, is not modified.

Claims (17)

Ski (1) intended for alpine skiing or cross-country skiing, formed of a body (2) and the sole (3) of which has a bearing surface of length Lp delimited at the front and at the rear by the contact lines respectively before A 'and rear D', and whose thickness is E _A at the level of the front contact line A 'and E _D at the level of the rear contact line D', characterized in that than - the bearing surface is divided into three contiguous areas, namely: a central zone Z _BC of thickness E that is substantially constant and whose length L _BC is greater than forty percent (40%) of the length Lp of the bearing surface; - two zones before Z _AB and rear Z _CD of variable thickness, located respectively in front and behind the central zone Z _BC , and of lengths L _AB and L _CD , - in that the quotient $\frac{{\mathit{\text{E -E}}}_{\mathit{\text{AT}}}}{{\mathit{\text{L}}}_{\mathit{\text{AB}}}}$

the difference in thickness (EE _A ) of the ski between the extreme points (A, B) of the front zone, divided by the length (L _AB ) of the same zone is between zero point zero one (0.01) and zero point one (0.1). - and in that the quotient $\frac{{\mathit{\text{E - E}}}_{\mathit{\text{D}}}}{{\mathit{\text{L}}}_{\mathit{\text{CD}}}}$

the difference in thickness (EE _D ) of the ski between the extreme points (C, D) of the rear zone, divided by the length (L _CD ) of the same zone is between zero point zero one (0.01) and zero point one (0.1). Ski according to claim 1, characterized in that the length L _BC of the intermediate zone Z _BC is between six hundred milllimeters (600 mm) and 900 millimeters (900 mm). Ski according to claim 1, characterized in that it is intended for the practice of cross-country skiing, and in that the thickness E of the intermediate zone Z _BC is between twenty two millimeters (22 mm) and thirty five millimeters (35 mm). Ski according to claim 1, characterized in that it is intended for the practice of alpine skiing, and in that the thickness E of the intermediate zone Z _BC is between fifteen millimeters (15 mm) and thirty millimeters (30 mm ). Ski according to claim 1, characterized in that it is intended for the practice of cross-country skiing, and in that the quotient of the difference in thickness (EE _A ; EE _D ) of the ski between the extreme points (A, B; C, D) of each zone before Z _AB and rear Z _CD , divided by the length (L _AB ; L _CD ) of the same zone is between zero point zero three (0.03) and zero point zero nine ( 0.09). Ski according to claim 1, characterized in that it is intended for alpine skiing, and in that the quotient of the difference in thickness (EE _A ; EE _D ) of the ski between the extreme points (A, B ; C, D) of each zone before Z _AB and rear Z _CD , divided by the length (L _AB ; L _CD ) of the same zone is between zero point zero one (0.01) and zero point zero three (0 , 03). Ski according to one of claims 1 to 6, characterized in that the intermediate zone Z _BC is constituted by a monobloc part of the beam (3). Ski according to one of claims 1 to 6, characterized in that the intermediate zone Z _BC is constituted by the superposition of a part of the beam (3) and an upper element (10) surmounting it. Ski according to claim 8, characterized in that the entire length of the upper element (10) is glued to the beam (3). Ski according to claim 8, characterized in that the central part of the upper element (10) is glued to the beam (3) and in that the front and rear end parts (11,12) of the upper element ( 10) are connected to the beam (3) by strips (25,26) of visco-elastic material. Ski according to claim 8, characterized in that the front and rear end parts (11,12) of the upper element (10) have vertical sections (13). Ski according to claim 8, characterized in that the front and rear end parts (11,12) of the upper element (10) have sections (14) inclined in the direction of the contact lines respectively front A 'and rear D' . Ski according to claim 8, characterized in that the front and rear end portions (11,12) of the upper element (10) are formed by straight segments (16,17), parallel and perpendicular to the longitudinal median plane of the ski . Ski according to claim 8, characterized in that the front and rear end parts (11,12) of the upper element (10) conform to a V shape, the point (18,19) of which is directed towards the outside of the 'upper element (10). Ski according to claim 8, characterized in that the front and rear end portions of the upper element form, when viewed from above, two non-parallel lines. Ski according to claim 8, characterized in that the beam and the upper element are both of constant thickness. Ski according to claim 8, characterized in that the beam and the upper element are of complementary shapes so that the thickness of the assembly is constant.

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