Ski with a system for influencing its stiffness by using hydraulic means

Abstract: The stiffness and vibrational behavior of a ski is controlled by hydraulic means (811,813,815-818) forming a hydraulic circuit in which a fluid is caused to flow in one direction upon flexing of the ski and in reverse direction upon counterflexing of the ski, said circuit having a selectively adjustable hydraulic resistance (815,816,817) which can have different values according to the direction of flow.

Description: The invention relates to a ski provided with a system for influencing the stiffness of an area of the ski, especially the underfoot area of the ski, as mentioned in the generic part of claim 1. Description of Background and Relevant Information A ski with such system is disclosed in FR-A 2 433 350. This document shows a ski with two hydraulic dampening devices influencing the flexing behavior of the forward end and the rearward and of the ski. These devices comprise respective hydraulic piston cylinder units, the cylinders of which are arranged and fixed on the foot supporting area of the ski. Each piston is connected to one end of a respective flexible bandlike plate which is slidably guided on the ski and fixed with its other end to the forward or rearward end of the ski. Upon flexing of the ski the pistons move in longitudinal direction in relation to the respective cylinders, whereby the flexing motions of the ski are dampened. AT-A 296109 refers to a support plate for a ski boot on a ski, said plate having an elastic movability in longitudinal direction of the ski for enabling the boot to perform respective movements when shock forces are applied to the ski. Such shocks are therefor dampened. While the devices of the mentioned references could be arranged in combination on a ski, it cannot be seen, how one device could be integrated in the other device without affecting the effectiveness of one device. EP-A 04 09 749 refers to a plate called Rossi-Bar which is slidably guided in longitudinal direction of the ski. The front and rear ends of said plate are engaged by spring means formed of elastomeric material and supported on the ski. The stiffness of the ski must be unavoidably increased under every condition, because the spring means exert a progressive force counteracting against flexing of the ski. An additional stiffness is caused by the fact, that the plate, which has the form of a rigid bar, is locked to the ski by clamps along the length of the plate, and it is the clamps which prevent the plate from sliding on the ski upon bending of the ski. Thus the plate reduces the bending of the ski. Important conditions affecting downhill skiers are the nature of the snow, the type of skiing to be done, the type of skis and bindings used and the skill of the skier. The snow and the ski run can vary during a day, while the ski and the skier are generally invariable. The snow can range from ice hard snow to very loose or soft snow, sometimes called powder snow. There are profound differences in skiing turns and speed according to the type of snow being skied upon. One primary characteristic of an ski is its ability to bend or flex as it carries a skier. A ski flexes and counterflexes, and keeps the skier in control as he or she follows the contour of a slope and enables a skier to manipulate the skis as he or she bounds and rebounds down the slope. In racing events, the snow can be ice hard both to increase the skier's speed and to avoid ruts in the snow. Hard snow may limit the bending of the skis. Turning is mainly accomplished in hard snow by the skier tilting the skis to dig the edges at the bottom of the ski into the snow by shifting his or her weight and body position. On the other hand, the ski can bend a large amount in powder snow. The longitudinal sides of skis are convex arcs, and it is through the use of the side cuts and bending of the ski that the skier turns; the edges of the skis are of much less importance in turning in powder snow. Regular snow, that is snow whose texture and packing is between hard snow and powder snow, presents other problems to the skier. Experience, communications with racers and other skiing experts, and testing, indicate that a ski stiffer underfoot of the ski boot may be preferable in very hard snow conditions while an overall more flexible ski appears to be preferable in soft snow conditions. An intermediate situation is preferable for snow of intermediate softness. It is also known that a ski loosely attached to the skier transfers little energy from the ski to the skier when the ski encounters obstacles, thus resulting in higher speed. However, a loose attachment results in loss of ski control in turns; hence it is desirable to have a loosely connected ski when traveling essentially in a straight line for greater speed and a tightly connected ski when making turns for greater control. The vibration characteristics of skis are also believed to be important. Skis have several vibration modes which are exhibited during skiing. High frequency vibrations break the contact between the ski bearing surface and the snow, which improves speed. On very hard snow conditions, the breaking of the contact between running surface and snow does not result in the same level of benefit but the ski still vibrates resulting in audible and perceptible chatter. A reduction in chatter is desirable in these condicions. Thus different requirements in underfoot stiffness and vibration exist depending on snow conditions. The ski designer, faced with the different kinds of snow, the different types of skiing, and variations in skiers and their bindings, can only develop skis which can handle all of these varying characteristics reasonably well but are not optimized for any specific condition. All ski bindings have an effect on ski stiffness underfoot. When a ski bends during skiing, the distance between the toe piece and the heel piece varies since they move relative to each other with the upward curvature of the ski. However, the length of the ski boot sole remains constant. Therefore, there is generally a limited movement rearwardly of the heelpiece in a clamp on the ski to keep it in contact with the boot. The force required to move the heel unit back results in a stiffening of the ski section directly under the bindung and boot. It is believed that most ski bindings on the market fall into this category. Therefore ski manufacturers take this stiffening action of the binding system into consideration in the design of the ski. The underfoot stiffness of the ski bindung combination is thus optimized for the type of skier and preferred snow conditions the ski was intended for. Different binding systems and separate devices to be used in conjunction with the ski and commercially available bindings have been manufactured to either increase or decrease the underfoot stiffness of the basic bindung/ski configuration. Other devices can effect the normal vibration of an ski. Combinations which decrease stiffness underfoot may improve soft snow skiablility while deteriorating skiability towards the end of the hard snow spectrum. Combinations which increase stiffness have the opposite effect. In some systems, the binding is constructed to render the ski more flexible. In the ESS v.a.r. device, a boot support plate having a forward portion which is slidable in an channel on the ski, should render the ski more flexible. However, the support plate is fixed with additional fastening means to the ski, and thus is believed to limit its benefits on soft snow. The fixing of the support plate decreases the bending of the ski. The Tyrolia Freeflex system utilizes a flexible plate attached to the top of the ski. The plate is fixed to the ski at the toe of the binding and is held in place about the heel by a slidable clamp fixed on the ski. Both toe and heel binding units are affixed on the boot support plate. When the ski bends, the heel clamp moves closer to the toe unit but the flexible plate is allowed to slide rearwardly reducing the tendency of the heel unit to move towards the toe as in a normal binding configuration. The ski is thus allowed to flex more underfoot. The plate is allowed to move in the slidable clamp but is also held to the ski by an additional sliding point between the toe and the heel. This mounting configuration increases sliding friction and thus the overall decrease of ski stiffening is relatively small. Devices of this nature are disclosed in U.S. Patent 3 937 481. Most ski binding manufacturers produce bindings which increase the stiffness of skis. The stiffness of an ski provides a firm edge to drive into the snow for making turns in hard or intermediate snow. In this respect, it is much like an ice skater who drives his or her blade into the ice to make a turn. A flexible blade would detract from the skater making a turn, just as a very soft ski in the section directly below the boot would detract from the skier turning in hard snow. Some expert skiers performing giant slalom or super giant slalom have found that their turning ability is enhanced when they attach to the ski, such as by gluing, a thin plate on top of the ski in the binding area. This added plate increases the distance between the skier's boot and the edges of the ski, and enhances the leverage which the skier has to drive the edges of the ski into the snow. WIPO Document 83/03360 discloses a device wherein glue and an elastomeric material hold a plate for supporting a toe piece and heel piece to the ski. The elastomeric material absorbs some of the vibration of the ski on the hard snow and relieves some of the discomforting noise of the ski rapidly smacking against the snow. Furthermore, the device stiffens the ski/plate/binding combination in the underfoot area of the ski improving edge control on hard snow. In U.S. Patent 3 937 481, a ski binding having an elongated plate is slidably mounted thereon for cushioning the skier when a forward abutment is encountered. Only the forward or toe portion of the system is fixed to the ski, so that the plate allegedly follows the bending of the ski. The device in fact impedes the bending of the ski since it is strapped to the ski in a number of places. A similar device with similar shortcomings is disclosed in Austrian Patent 373 786. A device of this type is sold under the name Derbyflex. It has been believed by many experts that raising the ski binding with such a plate detracts from the skier's ability to control the ski, since it was thought hat the skier had to be close to the snow to feel" the snow and ski accordingly. The present inventors and other manufacturers believe that this notion is wrong for most types of skiers, and that holding a ski boot somewhat high over the ski increases his or her ability to control the ski. Other patents disclosing ski bindings for increasing stiffness in skis include German Patent 21 35 450. Even though the added plate is beneficial, it only applies to skiing on hard snow where a stiffer underfoot ski is desirable. When used on softer or powder snow, the added stiffness detracts from the skier's ability to control the ski since easier bending adds to the turnability of the ski in soft snow. Other devices are known having moveable boot support plates on skis. For example, U.S. Patent 4 974 867 discloses a shock absorbing buffer disposed between a ski and a binding, and is not really related to the stiffness of the binding. The skill of the skier is another condition which the skiing apparatus should take into consideration. Although stiff skis are beneficial to good skiers in events such as giant slalom and super giant slalom, novice skiers should generally use flexible skis for all events, since they enable reasonable performance even though edge control in turns may be sacrificed. The inventors are unaware of any skibindings or skis which are adaptable to vary the stiffness in the binding location of a ski system according to the nature of the snow or the type of skiing to be done. They are aware of no skiing system whose stiffness and vibration characteristics can be changed to perform well in the various skiing conditions. Brief Description of the Invention It is an object of the invention to provide an improved device for controlling snow skis according to the nature of the snow, the skiing to be done, the type of skis and/or the skill oft the skier. It is a further object of the invention to provide a continuously adjustable stiffness device for a ski. It is a general object of the present invention to provide an improved ski control system for use with various types of snow, different degrees of skill of the skier and different skiing events, which system is efficient to manufacture and to use. It is yet another object of the invention to provide improved dampening means, to approve the skier's control during vibrations of the ski. These objects are solved by the features of the characterizing part of claim 1. The invention is adapted to control both the stiffness and the vibrational behavior of a ski. The support plate which supports a ski boot runs substantially along the length of the ski boot and can be attached to the ski at or near one of the ends of the plate. The other end of the plate is a free portion which slides longitudinally relative to the ski as the ski flexes or bends longitudinally about an axis or axes transverse to the longitudinal direction of the ski. According to one embodiment of the invention, a hydraulic cylinder is attached to the ski, adjacent to the free end of the support plate, whose opposite end is fixed to the ski. A piston located within the cylinder has an arm fixed to the free end of the support plate. Flow valves control the rate of hydraulic fluid flowing as the ski bends and the cylinder moves relative to the piston. The system can be set for flexing or counterflexing. According to another preferred embodiment of the invention, the support plate includes an elongated main member, and a slide member with can be moved longitudinally on the main member to accommodate ski boots of different sizes. The rear or heel end of the main member is fixed to the ski, and the forward end of the main member has a bearing for the slide. Brief Description of the Drawings The invention will be better understood when reference is had to the following drawings in which like numbers refer to like parts, and in which: FIGS. 1 and 2 are schematic drawings of the invention where the impedance means comprises a hydraulic system. Detailed Description of the Preferred Embodiments of the Invention The invention is directed to the changing of the stiffness of a ski. It includes an engagement means and an impedance means which cooperates with the engagement means to change the stiffness of the ski. The engagement means moves relative to the ski as the ski bends, unless this movement is changed, such as by being restricted or stopped by the impedance means. In some forms of the invention, the engagement means is a plate fixed to the ski and the impedance means is a stop for engaging the plate to change - in this case increase - the stiffness of the ski. The engagement means and the impedance means are operatively connected by hydraulic means to change - by varying - the stiffness of the ski to modify the articulation between the plate and the stop. The engagement means and the impedance means can be positioned at different places on the ski to control the stiffness at different areas of the ski. However, in its preferred embodiment, the engagement means is a support plate for supporting the ski boot on the ski, and the impedance means is adjustable for controllably engaging the support plate to vary the underfoot stiffness of the ski. Some hydraulic embodiments of the invention are shown in FIGS. 1 and 2. In these figures, support plates 803 are fixed at one end to the ski by anchors 805. The free end 807 is slidable in a clamp 809 attached to ski 107 as the ski bends longitudinally. The free end 807 of plate 803 is attached to a piston 811 slidable in a fluid cylinder 813, which is part of a hydraulic circuit. Cylinder 811 is fixed to ski 107. The part of the cylinder chamber forward of piston 811 is connected by fluid lines to an adjustable valve 815, a selected one of oppositely directed, uni-directional valve heads 816,817 and a manual fluid valve selector 818 connected to a fluid line for the fluid in cylinder 813 on one chamber or side of piston 811. When the system is set up as shown in FIG. 1, as the ski bends or flexes, forward end 807 and piston 811 move rapidly through the chamber in cylinder 813 since fluid is forced from the cylinder through fast flowing , one way or uni-directional valve head 816, through valve selector 818 and into the side of the cylinder chamber behind piston 811. In this configuration the ski can flex downwardly freely and easily since piston 811 encounters little resistance in its forward movement. When the downward loads which caused the ski to flex are reduced - such as the end of a turn - the ski will tend to return to its normal flex state as fluid flows from the right hand side of cylinder 813, through adjustable valve 815 and into the cylinder on the left hand side of piston 811. The rate of counterflexing will be determined by the adjustment of adjustable valve 815. The counterflex speed of the ski can thus be adjusted by the setting of valve 815, and the counterflex can be dampened. In FIG. 2, valve selector 818 is operatively connected to uni-directional valve head 817. Now when the ski flexes, free end 807 forces piston 811 to the right, and fluid flows through adjustable valve 815; this is generally a slow flow rate depending on how valve 815 is adjusted. During counterflex, the fluid moves very quickly from the left side of piston 811, through one way valve 817 so that the piston returns quickly to the embodiment shown in FIG. 2. This is good for the free and easy counterflexing movement of the ski. Various systems for controlling the stiffness of a ski have been described above. The skier may manually, or perhaps with the ski pole or some other device, adjust the apparatus according to the type of stiffness to be desired. The skier need not have different skiing apparatus for different types of snow or different abilities of the skier, and need not settle for a binding which is appropriate for only one type of skiing or which approximates different types of skiing but cannot adequately control the stiffness precisely for different types of skiing. Now, the skier need only adjust the apparatus for the type of stiffness desired and to participate in the skiing event. The settings can be changed as the skier desires. Furthermore, in some embodiments the skier can continuously adjust the stiffness of the ski. The adjustable member could be at places other than at the forward end of the support plate, such as at the rear end, at both ends and/or in the middle. Although many embodiments are given, it should be appreciated that other variations will fall within the scope of the invention.

Claims: A ski provided with a system for influencing the stiffness of an area, especially the underfoot area, of the ski (107), this system comprising an elongated support means (803) arranged in longitudinal direction of the ski, a first portion (805) of said support means fixed to the ski and a free end portion (807) being movable in relation to the ski in longitudinal direction thereof, and an impedance means (811,813,815 to 818) cooperating with said support means and comprising a hydraulic means (811,813,815 to 818) forming a hydraulic circuit in which a fluid is caused to flow in one direction upon flexing of the ski and in reverse direction upon counterflexing of the ski, said circuit having a selectively adjustable resistance (815,816,817), characterized in that said support means is a support plate for supporting a ski boot. A ski provided with a system according to claim 1, characterized in that said resistance has a high value for the fluid flowing in the one direction and a low or neglectable value for the fluid flowing in the reverse direction. A ski provided with a system according to claim 1 or 2, characterized in that a piston-cylinder-unit (811,813) is operatively arranged between the ski (107) and the free end portion (807), said piston-cylinder-unit having a first side forward of the piston and a second side behind the piston, and the said sides being connectable and/or connected in parallel by an adjustable valve (815) having an adjustable hydraulic resistance and an uni-directional valve (816,817). A ski provided with a system according to claim 3, characterized in that selectable opositely directed uni-directional valves (816,817) are arranged. A ski provided with a system according to one of claims 2 to 4, characterized in that the hydraulic circuit has its high hydraulic resistance upon counterflexing of the ski. A ski provided with a system accordnung to one of claims 2 to 4, characterized in that the hydraulic circuit has its high hydraulic resistance upon flexing of the ski.

Inventors: LEHNER EDWIN, PREMEK STEPHANEK, RUFFINENGO PIERO G, WAGNER LUDWIG, LEHNER, EDWIN, PREMEK, STEPHANEK, RUFFINENGO, PIERO G., WAGNER, LUDWIG
Applicants: MARKER DEUTSCHLAND GMBH
Application year: 1991
Main classification: A63C5
IPC codes: A63C9, A63C5