Ski with a system for influencing its stiffness by using friction

Abstract: The stiffness and vibrational behavior of a ski is controlled by frictional cooperation of an engagement means and an impedance means (607,619,627,629) moving relativ to each other when the ski flexes.

Description: The invention relates to a ski combined with a system for influencing the stiffness of an area of the ski, especially the underfoot area, as mentioned in the generic part of claim 1. Description of Background and Relevant Information A ski provided with such system is disclosed in WO 83/03360. This document refers to a vibration damping system for skis. This system comprises a longitudinal plate having one end to the ski and another end arranged with movability in longitudinal direction of the ski, wherein such movability can be restricted by tension forces of elastomer material inserted between abutment elements fixed to the ski and abutment faces of the movable end of the longitudinal plate. A layer of elastomeric material is interposed between in underside of a middle portion of the longitudinal plate and the adjacent upperside of the ski for dampening vibrational movements of the latter. 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 if 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 loked 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 important 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 bonding 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 underfoor may improve snow skiabilility 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 betwwen 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. 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. 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. Even though the added plate is beneficial, it only applies to skiing on hard snow were a stiffer underfoot ski is desirable. When used on softer or powder snow, the added stiffness detracts from the skier's ability 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 bindung, 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. Another aspect of the invention is to provide a support plate for a ski binding which controls the stiffness of skis in different skiing conditions. A further object of the invention is to provide a device for controlling the stiffness of skis incorporating a plate fixable to a ski and having a slidable portion, and an impedance device for controlling the slidable device to obtain the desired stiffness. Another object of the invention is to provide a support plate assembly for controlling the stiffness of a ski with the assembly having a plate attached to the ski and an adjustable stop whose position controls the effects of the plate an the amount of bending of the ski. 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. In fundamental form, the invention includes a support plate which is attached to the ski, and runs substantially along the length of a ski boot area. The plate is fixed to the ski at or near one of its ends. 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 tranverse to the longitudinal direction of the ski. This free end portion cooperates with a friction member arranged at the ski. 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: FIG. 1 is a schematic drawing of a form of the invention where the impedance means is a contiuously varible bias device including a friction member. Detailed Description of the Preferred Embodiments of the Invention The invention is directed to the changing of the stiffness of an ski. It includes an engagement means which moves relative to the ski as the ski bends, and an impedance means which cooperates with the engagement 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 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 engagment means is a support plate for supporting the ski boot on the ski, and the impedance means is an adjustable stop for engaging the support plate to vary the underfoot stiffness of the ski. Referring to FIG. 1, a stiffness controlling assembly 601 is shown including a support plate 603 which is fixed to the ski 107 at one end, here the rear end of the palte, and a free at ist opposite end, which shown here is the forward end 605. When the ski 107 flexes or bends longitudinally about an axis traverse to the longitudinal direction of the about an axis traverse to the longitudinal direction of the ski 107, the end 605 slides longitudinally relative to the ski 107. The free end 605 has tapered portions at the upper and lower part of plate 603 with inclined faces shown at 607 and 609, which run transverse to ski 107. an adjustment, control or retainer memner 611 has a housing 612 which is attached to the ski by means of a fastener such a screw 613 and a holding member 615, which is attached to the ski, for receiving retainer or fastening member 613 through a bore 617 contoured to receive the fastener. A spring such as helical spring 619 is disposed in housing 612 and is located to be compressed by compression member such as washer 621 as fastener 613 is rotated. Spring 619 is compressible between shoulder 622 in housing 612 and member 621. Retainer member 611 includes a flange 623 which extends rearwardly, and has an inclined abutment face 625 which is contoured to engage the face 607 of plate 603. Holding member 615 also has a flange 627 extending partly along the length of ski 107, and having an inclined portion with a face 629 contoured to engage the face 609 of plate 603. Screw 613 has a flange 631 which is seated beneath the upper end wall of housing 612 of adjustment member 611, and has a head 633 which can be turned to either move nut 621 into holding member 615 to compress spring 619, or to be urged in the opposite direction to relieve the compression on spring 619. The stiffening in the apparatus shown in FIG. 1 is accomplished by friction between an adjusting member and a support plate. The apparatus is continuously adjustable. Therefore, in the operation of assembly in FIG. 1, if further stiffening of the ski is desired, screw 613 is tightened to move nut 621 towards the ski to compress spring 619. This compression urges adjusting member 611, and the face of leg 623 against face 625 of plate 603. The tension created by face 607 and face 625, and face 609 and face 629, essentially clamps plate 603 to the ski at its forward end 605, to substantially prevent bending of ski 107 between fastener 611 and the anchor between the support plate and the ski. In its most compressed condition, the ski apparatus is extremely stiff underfoot, and is particularly useful in curves made on hard snow. As fastener 613 is loosened, the compression on spring 619 decreases, and the tension on end 605 of support plate 603 becomes less and less. In its compressed condition, the portion of ski 107 under support plate 603 is essentially bendable, and is particularly useful for skiing on loose or powder snow. There is no need for a clamp to guide support plate 603 along ski 107 as the ski bends, since the forward end of the plate is confined between the retainer 611 and the holding member 615. The friction device 601 has some useful features. First, the spring is a progressive force, the spring force increasing as the support plate intrudes between the retainer 611 and the holding member 615, increasing stiffness as the ski bends. Second, the spring provides greater friction for flexing than for counterflexing. However, the friction approaches 0 as the angle α approaches 0.

Claims: A ski (107) combined with a system for influencing the stiffness of an area of the ski, expecially the underfoot area, this system comprising an elongated support plate (603) arranged in longitudinal direction of the ski, a first portion of said support plate fixed to the ski, and a free end portion (605) of said support plate being movable in relation to the ski in longitudinal direction thereof and having a face extending in longitudinal direction of the ski, and an impedance means (601) accomplishing friction counteracting movements of said support plate in relation to the ski and thereby providing a force increasing the stiffness of the ski as the ski bends characterized in that a friction member (601,619,623,627) arranged at the ski only at said free end portion urges with an adjustable force against said face (625,629) of said free end portion (605) thereby creating friction counteracting the movability of said free end portion in relation to the ski. A ski combined with a system according to claim 1, characterized in that the friction member provides greater friction for flexing than for counterflexing of the ski. A ski combined with a system according to one of claims 1 or 2, characterized in that the friction member provides a progressive force and increasing stiffness of the ski as the ski bends. A ski combined with a system according to one of claims 1 to 3, characterized in that both the free end portion (605) and the friction member (601) have inclined faces (607,609;625,629) for cooperation of the free end and the friction member, the one inclined faces (625,629) adapted for being urged between the other inclined faces (607,609) upon bending of the ski (107), thereby creating a progressive force upon intruding of the one inclined faces between the other inclined faces.

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