Ski with a system for influencing its stiffness by using inertial forces

Abstract: The stiffness of a ski is controlled by inertial means (937,938), thus the stiffness being dependent upon inertial forces exerted upon the ski. Said means preferably comprise an inertial pivot arm (937).

Description: The invention relates to a ski provided with a system for influencing the stiffness of an area of a ski, especially the underfoot area of a ski, this system comprising an elongated support means arranged in longitudinal direction of the ski, a first portion of said support means fixed to the ski and a free end portion being movable in relation to the ski in longitudinal direction thereof, and an impedance means cooperating with said support means. Description of Background and Relevant Information A ski provided with such system is disclosed in EP-A 04 09 749 (publication date : 23.1.91 referring 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 mentioned earlier, 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 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. A more particular object of the invention is to provide a support plate and an adjustable stop, movable to make the device very stiff when necessary. 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 the main object of the invention to provide an assembly for changing the stiffness of the ski dependent upon inertial forces. The ski according to the invention which is defined in claim 1 has impedance means comprising an inertial means serving as an abutment stop designed to move upon inertial forces acting on said stop and thereby restraining the movableness of the free end portion according to the inertial forces. The support means could be a support plate which supports a ski boot and runs substantially along the length of a ski boot and is 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 and cooperates with the stop controlled by inertial forces. In one embodiment of the invention, the impedance means can be an adjustable force rocker or stop comprising an inertial arm pivotable about a fulcrum fixable to the ski, the arm having one end attached to spring means while the other end is free. The arm is designed to pivot as a result of the inertial forces acting thereon so that the free end is brought into juxtaposition with a surface of a slide member of the support plate, to limit the distance which the slide member can slide and thus control the stiffening effect of the support plate during turns when inertial forces bring the arm into juxtaposition with the surface of the slide member. The slide member preferably has a bifurcated forked configuration, and the inertial pivot arm is brought into juxtaposition with the forked end to obtain the stiffening result. Brief Description of the Drawings The invention will be better understood when reference is had to the following drawing in which like numbers refer to like parts, and in which: FIG. 1 is a plan view of an embodiment of the invention, without a cover plate, and FIG. 2 is a cross-section of the latter embodiment taken ablong the longitudinal centerline of FIG. 1. 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 by means of a discrete change such as to stop the articulation between the plate and the stop. The engagement means and the inpedance 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 an adjustable stop for engaging the support plate to vary the underfoot stiffness of the ski. FIG. 1 is an plan view of an embodiment of the support plate of the invention, shown without a cover plate. A support plate main member 904 is fastened at one end or portion thereof (not shown) to the ski (not shown). As illustrated, a free end of the support plate main member 904 is fastened to a support plate slide member 935 by means of attachment screws 907, not shown, inserted into threaded bushing 908. Thus the support plate slide member 935 is forced by the support plate main member 904 to move in longitudinal direction of the ski when the ski flexes or bends. The support plate slide member 935 is retained in slide bearing yoke 918, being free to slide therethrough, and is bifurcated at its unattached end having forks 939 and 940 located thereon. The forks are provided with fork abutment surfaces 941 and 942, respectively, adapted for juxtaposition to surface 943 of the free end 944 of pivot arm 937 which serves as an abutment or control member, or abutment stop. The opposite end of the pivot arm is attached to spring 939 whose other end is anchored, for example, to base plate 936, better seen in FIG. 2. In this embodiment, the pivot arm or abutment stop itself cooperates in limiting the amount of longitudinal movement of which the support plate slide member is capable. In this regard, the inertial force on the free end 944 of the pivot arm, for instance, when the ski is running on its edge, serves to automatically pivot the arm so that the outermost radial surface 943 of the free end of the pivot arm 937 pivots to a point at which it is juxtaposed to either fork abutment surface 941 or 942, where it acts to restrain their movement. The pivoting motion acts against the force imposed by the weak spring 938; however, when the inertial force is no longer operable, the spring acts to realign the pivot arm along the longitudinal axis of the ski. Advantageously, the juxtaposed surfaces of abutment surfaces 941 and 942, as well as the outermost radial surface 943 of pivot arm 937 have mating curved surfaces which conform to a radial arc whose center is the pivot point of the pivot arm 937. FIG. 2 is a cross-section view of a support plate of the invention along the longitudinal centerline of FIG. 1. The support plate main member 904 is connected to the support plate slide member 935 by means of attachment screws 907, which engage the threaded bushing 908 disposed in the fork slots of the bifurcated end of the support plate main member 904. The slide member 935 is retained in slide bearing yoke 918, which in turn is fastened to a ski by fastening screws 919. The pivot arm 937, pivotable about the smooth shanked fastener 909 which also fastens base plate 936 to the ski, is urged into a longitudinal position, relativ to the ski, by weak spring 939 anchored to the base plate 936. The figure illustrates the thickened section of the pivot arm 944, which not only adds inertial mass to the arm, but also provides the necessary surface area 943 at its end to efficiently engage the forked abutment surfaces 941 and 942, respectively. The jaws of the binding and cover plate 906 are fastened to the assembly by attachment screws 907, as previously indicated, while the front ends of the jaws are prevented from upward and lateral movement by the smooth shanked fastener 909. If desired, provision may be made for moving the pivot arm 937 along the longitudinal axis of the support plate assembly to allow the clearance between surfaces 941 and 942 with surface 943 to be adjusted in a way allowing more or less movement of the support plate slide member 935, thus adjusting the freedom of the ski to flex. As will be appreciated, the support plate slide member is free to slip back and forth through the slide bearing yoke 918 so long as the ski is mowing in a direction of the fall line of the slope, a condition in which no stiffening of the ski adjacent to the support plate will occur. On the other hand, when the ski is moved into a turn, a condition in which inertial forces act on the pivot arm 937, the arm will swing out of the intermediate position illustrated in the figure, the surface 943 of its free end thereupon being juxtaposed with one of the abutment surfaces 941 or 942. In this position, the movement of the slide member 935 is restrained, preventing flexing of the ski and allowing short, rapid turns to be accomplished with precision, even on hard snow. 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 of the ski (107), especially the underfoot area, this system comprising an elongated support means (904) arranged in longitudinal direction of the ski, a first portion of said support means fixed to the ski and a free end portion (939,940) being movable in relation to the ski in longitudinal direction thereof, and an impedance means (937,938) cooperating with said support means, whereby said impedance means comprises an inertial means (937,938) serving as an abutment stop designed to move upon inertial forces acting on said stop and thereby restraining the movableness of the free end portion (939,940) according to the inertial forces. A ski provided with a system according to claim 1, characterized in that said inertial means comprises an inertial pivot arm (937) designed to pivot as a result of inertial forces acting thereon so that a free end is brought into juxtaposition with a surface (941,942) of the free end portion, to limit the distance which the free end portion can move, thereby controlling a stiffening effect when inertial forces bring the arm into juxtaposition with the said surface. A ski provided with a system according to claim 2, characterized in that the free end portion is bifurcated having forks (939,940) located thereon, said forks provided with abutment surfaces (941,942) adapted for juxtaposition to a surface (943) of the free end (944) of pivot arm (937) which serves as an abutment or control member or abutment stop upon inertial forces. A ski provied with a system according to claim 3, characterized in that the pivot arm is attached to a spring (938), said spring acting to realign the pivot arm along the longitudinal axis of the ski when the inertial force is no longer operable. A ski provided with a system according to one of claims 2 to 4, characterized in that the free end portion (939,940) can freely move when the pivot arm (937) is in its position related to absence of inertial forces. A ski provided with a system according to one of claims 2 to 5, characterized in that means for controllably moving the pivot arm along the longitudinal axis of the support means are comprised to allow more or less movement of the free end portion, thus adjusting a freedom of the ski to flex.

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: A63C5, A63C9