Supporting plate incorporating an adjustable asymmetry function for shaped skis

The present invention relates to the alpine skiing equipment, in particular to safety-binding assemblies for shaped skis and to the means for improving the performance of such skis.

The invention is based on the objective of providing a supporting plate, positioned between the ski and the ski-binding, such as to enable the skier to execute a carving turn in such a way, that in ideal circumstances the skis would track two parallel lines matching closely the arcs of concentric circles, and that no extra energy would be needed to sustain a parallel position of the skis throughout the turn. In addition, the solution of the technical problem should allow the skier to make an ideal carving turn with no excessive vibrations and without requiring the skier to increase his/her physical efforts much above normal activity. Besides, the solution of the technical problem should be undemanding as far as technology is concerned, and also economically feasible.

For decades the skiing technique has been based on performing the turns by using in effect only one ski that is the outside ski. The trace of such a turn is a single line. By contrast, with carving skiing technique, which is practiced by shaped skis, also referred to as super sidecut skis, the weight Is basically equal on both skis and the edge angles of the skis are equal. Consequently, the skis draw a trace in a form of two parallel arcs spaced apart at a distance equal to the gap between the skier\'s feet, which is about 0.5 m when the turning is intense and executed at high speeds. A correct carved turn can be carried out only, if the construction and the deformation of the system configured of the ski and the supporting plate are such as to allow the ski edge to be curved into an ideal contour congruent as much as possible to a portion of a circle. With the edges bent in such a way the skier literally carves Into the snow and the trace of such ideal turn is a pair of parallel curves nearly matching the arcs of two concentric circles.

Due to physical limitations and due to problems originating from these limitations, it is hard to carry out an ideal carving turn. For illustration, an example of a typical intense carving turn is presented in FIG. 5, having a radius of 5 meters and the distance between the inside and the outside ski of 0.5 meters. The weight on both skis is equal, as each ski carries a half of the skier\'s weight F_g, and both skis have equal edge angle α relative to the surface of the snow. If the inside and the outside ski are considered as two separate systems, it is evident from FIG. 5, that the skier makes a similar arc with the inside and the outside ski, respectively, and that both circles, which are spaced at a distance between the skis (0.5 m), have equal radius. However, near the middle of a turn, the circles intersect, because the skis are not running along parallel round arcs through the entire turn. At the beginning of a turn the skis are parallel, while toward the midpoint their tips tend to close like a snowplow. As a result, soon after the beginning of a turn the skier has to put in much effort to hold the skis in parallel position.

Due to ergonomic characteristics of the human body, and especially when the turns are performed on difficult terrain and with higher speeds as well as in critical situations, the weight exerted on the outside ski is increased as compared to the weight exerted on the inside ski. Consequently, the weight on the inside ski is lower, and besides, the tilt of the outside ski edge becomes higher than the tilt of the inside ski. From FIG. 6 it is evident, that the resultant of the forces exerted on the outside ski is greater, therefore the outside ski bends more than the inside ski. Due to greater bending of the outside ski and due to its higher tilt relative to the snow surface, a curve carved by the edge of the outside ski matches a circle with a smaller radius than the desired turn, moreover, smaller radius than the circle arc carved by the inside, less weighted and less tilted ski. As a result, the skier should put in more of his/her energy to sustain the skis in parallel position and should continuously make corrections in the turn, while the courses of the skis deviate more and more from circle arcs. Hence, the sensitive dynamic balance of the skier is destroyed, one ski lags behind the other and the upper part of the skier\'s body is rotating. All these effects together prevent the skier to carry out the turns as intended, causing a loss in speed and balance and an increase in energy consumption, so the skier could be exhausted quickly.

FIG. 7 shows an example of an ideal carving turn where the skis trace two parallel lines throughout the course of the turn, the skier is in a dynamic balance at all times and no unnecessary consumption of inner energy is required to sustain the skis in parallel position. The above turning characteristics enable the skier to execute a turn in a fastest way, which is extremely important for the alpine skiing racers. With the skiing equipment known so far such perfect turns could be performed only by an excellent skier, who could weight the inside ski slightly more than the outside ski and who could at the same time increase the tilt of the inside ski by several degrees in comparison to the tilt of the outside ski. With regard to ergonomic aspects, such performance of a turn would be extremely hard to manage and moreover, it would not be feasible for a majority of skiers, as it would result in high dynamic instability.

The supporting plate incorporating an adjustable asymmetry function enables the skiers of various grades of skill, ranging from recreational skiers to ski racers, to perform perfect turns by taking advantage of the adjustment possibility offered by the solution according to the present invention.

Known supporting plates such as for example the World Cup-Air plate manufactured by Vist, are designed, firstly, to offer the basic function of a lifter beneath the ski-binding preventing the boot to touch the snow when the skier makes a turn and thereby allowing the skier to sustain the natural flexion of the ski, and secondly, to absorb vibrations.

In the U.S. Pat. No. 6,659,493 a connector plate for ski bindings of snow skis or snowboards is described which enables better execution of turns, improves the flexibility of skis or snowboard and ensures better absorption of vibrations. The connector plate is universal, which means that it can be applied with any type of skis or snowboards and with any type of ski bindings, however its advantages are most prominent with the shaped skis. Two connecting segments, constructed from an elastic layer made of rubber or silicon, realize the above characteristics. Along the lateral axis of the elastic layer, which lies perpendicular to the longitudinal axis of the ski or snowboard, at least one solid supporting element is located, dividing the elastic layer into two regions: one region is compressed and the other expands during the flexing of the ski or snowboard. In addition, the construction allows for longitudinal movement in the elastic layer of the connecting segments.

The support plate described in DE 198 43 866 A1 ensures an optimal line of a turn executed with shaped skis by lifting the boot to a higher position and thereby lessening the possibility for the boot to touch the snow at extreme carving angles, which would result in loss of edge grip. Besides, the plate is fixed to the ski by means of two bearing assemblies which allow certain sliding along the longitudinal direction and a predetermined torsion play relative to the cross axis of the support plate.

The device for improving the efficiency and controllability of skis disclosed in U.S. Pat. No. 5,758,894 has two elongated shaped plate-like elements, each having one end provided with locking members for fixing to the ski and another end provided with retention members, which allow the other end to slide longitudinally with respect to the ski. A toe unit or heel unit of a ski binding is fixed proximate to one of the ends. The same relative (center-of-gravity) position is thus maintained at all times between the boot and the ski, and thus the possibility to control said ski is always optimal.

Beside the basic function of lifting the skier and shifting the boot from the snow in the turns, the known supporting plates ensure various additional functions, for example absorbing of vibrations, enhancing the flexibility and improving the controllability of skis. In contrast to known constructions of supporting plates or devices, with the supporting plate according to the present invention a challenge of ideal carving turning is tackled with the aim to enable the skier to execute a perfect turn without superfluous consumption of energy and without excessive corrections. This aim is achieved by an asymmetry set-up assembly that prevents the skis to close into a wedge position toward the middle of the turn and ensures a parallel course of both skis throughout a turn. In addition, any unwanted vibrations of the front and the rear portion of the ski are absorbed by an adjustable feedback loop formed in the plate.

The behaviour of the skis in a turn can be compared with the behaviour of a motorcycle or a motorcar in a curve. A turn with only one ski touching the ground is comparable to a turning of a motorcycle, whereas a carving turn, which is performed with both skis on the ground, can be compared with a turning of a motorcar. As far as physical aspects are concerned, turning of a motorcycle is simple. In contrast, a turn of a motorcar involves turning of a pair of spaced front steering wheels and can be performed properly only by applying the Ackermann automotive steering principle, whereby the wheels are suspended separately so that the inside wheel can turn a bit tighter circle than the outside wheel. To achieve this, the inside wheel needs to be turned for a higher angle as compared to the outside wheel. The concept of a separate and different movement of the inside and the outside wheel represented an inspiration for the solution of a similar problem encountered when making a turn with shaped skis.

The supporting plate incorporating an adjustable asymmetry function has a special construction and Is fixed firmly onto the ski only in one transversal line in the front portion beneath the beginning of the toe piece of the binding, while in further three transversal lines, the plate is fastened flexibly in order to sustain maximum flexibility of the ski. The asymmetry set-up assembly, whose function is to discriminate the inside and the outside ski in the turn, whereby a distinct behaviour is assigned to the inside and the outside ski, respectively, is realized in the control assembly of the supporting plate by means of a weighting member, formed of two balls, that is one solid ball made of steel and one soft ball made of rubber or similar material. The weighting member may consist of a single steel ball. The construction of the supporting plate according to invention ensures also efficient suppression of unwanted vibrations.

The objects, features and advantages of the supporting plate according to the present invention are described in detail by reference to the accompanying figures showing:

FIG. 1 a longitudinal section of the supporting plate, fixed on the ski

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