Abstract:
An item of sports equipment to be fastened to a person&#39;s foot, the sports equipment including a rolling or sliding member by which the sports equipment can be rolled or slid along a ground surface, wherein the rolling or sliding member includes a front portion and a rear portion, wherein the front portion includes a roller or a sliding surface for the ground surface, and the rear portion includes a roller or a sliding surface for the ground surface, wherein the front portion and the rear portion are connected to a crosspiece.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is the U.S. National Phase application of PCT International Application No. PCT/EP2011/002230, filed May 5, 2011, which claims priority to German Patent Application No. 10 2010 020 253.3, filed May 11, 2010, the contents of such applications being incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates to an item of sports equipment which is arranged on or fastened to a person&#39;s foot for its intended use. The sports equipment can for example be a sliding board or snow sliding board, in particular an alpine ski. In principle, however, the sports equipment can also be a cross-country ski, a roller ski or an in-line skate. 
       BACKGROUND OF THE INVENTION 
       [0003]    A multitude of different alpine skis are known from the prior art. Modern skis are configured as so-called carving skis. One essential feature of a carving ski is its relatively large sidecut. This means that the ski is significantly wider at its front and rear ends than between the ends, such as for example in the region of the binding, which is the narrowest point or point of greatest sidecut. This determines the sidecut depth. This depth can be measured if the ski is put on edge, on a level surface, by 90° about its longitudinal axis and lies on its widest points at the front and rear end. The distance between the narrowest point of the ski and the level surface corresponds to the sidecut depth. Between the bearing points, the lateral flank of the ski follows a curve for which a radius can be calculated as a function of the distance between the bearing points and the sidecut depth. In the case of carving skis, this radius usually equates to between 10 and 20 m, but can also be more or less than this. For designing the shape of the lateral flank of the ski and/or for ascertaining the radius of the lateral flank, the curve radius of the ideal motion curve and the desired motion speed are selected. From this, it is possible to ascertain the centrifugal force and therefore the inclination angle of the skier and the skis towards the interior of the curve for stable turning. This determines the carving angle by which the ski is put on edge about its longitudinal axis. If one imagines a ski which has a constant width and is flexed about its transverse axis onto the radius of the motion curve, then the intersecting edge between the ski and the ground surface—which is assumed to be level—determines the desired shape of the lateral flank of the ski. Carving skis therefore carve particularly well. 
         [0004]    Other features of a carving ski are its flexibility about the transverse axis, which is predetermined by its flexural rigidity about the transverse axis, and its ability to twist about the longitudinal axis, which is predetermined by its torsional rigidity about the longitudinal axis of the ski. What is generally desired is flexibility of the ski about its transverse axis combined with a high torsional rigidity of the ski. Due to the design of the ski, high flexibility combined with high torsional rigidity cannot usually be realised simultaneously. The binding in combination with the ski boot also influences, i.e. reduces, the flexibility of the ski. 
         [0005]    Referring to  FIGS. 1   a  to  1   c , the behaviour of known skis under different load conditions shall be explained. The ski in  FIG. 1   a  has no load, wherein it can be seen that due to its prestress, the ski  1  is concavely arched on its sliding surface between the front and rear ends. If the ski  1  is put on edge, as in  FIG. 1 , and the ski  1  is pressed against a flat ground surface with a force F, it will bow convexly. In  FIG. 1   b , the line of application of the force F—which is applied at the skier&#39;s centre of gravity—passes through the design point K which has been assumed to be the force application point in the design of the ski. The ski  1  is therefore under a load, as is assumed in the design. If the edge of the ski conforms to the ground surface, then it is not deformed any further, irrespective of the magnitude of the force F. 
         [0006]    While skiing, the skier does not usually keep their centre of gravity exactly and constantly over the design point K. The skier&#39;s centre of gravity is instead situated in front of or behind the design point, such that the force F is applied at an offset in relation to the design point. If the force F applied at the centre of gravity is offset towards the rear in the longitudinal direction in relation to the design point, then the angular speed during motion will be increased by the factor of the motion curve. If the force is offset towards the front in the longitudinal direction in relation to the design point K, then the angular speed during motion will be reduced by the factor of the motion curve. The force F which is offset in relation to the design point K generates a moment which is dependent on the distance between the force line of the force F and the design point K. This moment raises the ski between the design point K and the front end such that the edge no longer lies on the ground surface at this point, or at least relieves the ski at this point such that the edge no longer presses onto the ground surface with the required force. The ski will therefore no longer follow the ideal motion curve. 
         [0007]    It is therefore an object of the invention to provide an item of sports equipment which can be strapped onto a foot and which enables improved motion characteristics. 
       SUMMARY OF THE INVENTION 
       [0008]    This object is solved by the subject matter as describe in the description and illustrated in the figures. 
         [0009]    The invention proceeds from an item of sports equipment to be fastened to a person&#39;s foot. It is for example possible to provide one such item of sports equipment for each foot or to provide one shared item of sports equipment for both feet. The sports equipment can for example be a snow sliding board, such as for example a ski, particularly preferably an alpine ski. Alternatively, the invention can also be used with roller skis or in-line skates. The sports equipment can be able to be fastened to the person&#39;s foot by means of a boot. The boot can be a separate part which is connected to the sports equipment, or the sports equipment can comprise the boot. 
         [0010]    The sports equipment comprises a means for contact with the ground surface, which can be referred to as the ground surface contact means. This means can be a rolling means or a sliding means. Using the ground surface contact means, the sports equipment can be able to be moved, in particular rolled or slid, along a ground surface in a contact. The rolling or sliding means can comprise a front portion and a rear portion, wherein the front portion comprises a roller or a sliding surface for the ground surface, and the rear portion comprises a roller or a sliding surface for the ground surface. 
         [0011]    The front portion is the portion which is arranged in front of the rear portion in the intended direction of motion. The intended direction of motion preferably corresponds to the forward movement of the user of the sports equipment. The front portion and the rear portion are parts which are preferably separate from each other and are preferably configured to be elongated. The longitudinal axis of the front portion and the longitudinal axis of the rear portion can preferably be aligned with each other and can in particular form the longitudinal axis of the sports equipment. The front portion can form a mount for at least one and preferably two rollers or a sliding surface and in particular an engaging edge. The same correspondingly applies to the rear portion. 
         [0012]    If the ground surface contact means is a rolling means, the front portion—which is in particular formed in the shape of a mount—can form or comprise a bearing for the at least one roller and comprise at least one roller which can be rotated relative to the front portion. The same correspondingly applies to the rear portion. Slide bearings or ball bearings which can be formed from metal, plastic or ceramic can be provided as the bearing. The running surfaces of the rollers preferably comprise a plastic or rubber material which on the one hand offers good rolling-off characteristics and on the other hand prevents the rollers from slipping away laterally. In particular, the front portion and/or the rear portion can respectively comprise at least two rollers. The front and/or rear portions are respectively supported in the longitudinal direction at two points of contact on the ground surface. The first roller forms the first point of contact with the ground surface, and the second roller forms the second point of contact with the ground surface. The at least two rollers of one portion and in particular the at least two rollers of the other portion are arranged one behind the other in the longitudinal direction. In particular, the rollers of the front and rear portions roll off on a shared line. 
         [0013]    In particularly preferred embodiments, the ground surface contact means is a sliding means. A sliding surface is arranged on the lower side of the front portion which is formed in the shape of a mount. The same applies to the rear portion. The sliding surface can be formed by a plastic material or a metal which in particular forms a low coefficient of friction with snow or ice. The sliding surface can be defined laterally, i.e. along the longitudinal axis, in particular on both sides by engaging edges which can preferably be formed from metal, in particular steel. It would however in principle also be possible to provide only one engaging edge, for example on the inner side, i.e. where there is a separate item of sports equipment for each foot, on the flank pointing towards the other item of sports equipment. When the sports equipment is put on edge about the longitudinal axis, the engaging edges can enter into engagement with the ground surface. The engaging edges form the transition between the sliding surface and lateral flanks extending along the longitudinal direction of the front and/or rear portion. The engaging edges are preferably arranged on both sides of the sliding surface and/or laterally enclose the sliding surfaces. The front portion and the rear portion are preferably configured in the shape of boards or sliding boards, i.e. the thickness of each of the front portion and rear portion is small as compared to their length and/or width. In particular, the front portion and the rear portion can be configured in the shape of skis. 
         [0014]    The front portion and the rear portion can preferably be elastically deformed about their transverse axis, i.e. the axis which is perpendicular to the longitudinal axis and parallel to the ground surface and/or sliding surface, in particular to such an extent that the front portion and the rear portion can conform to a path arranged on the ground surface. It is generally preferred if the front portion and rear portion can be elastically reshaped such that the engaging edges can conform to the ground surface or the path when the sports equipment is put on edge. 
         [0015]    It is preferred if the front portion widens, in particular constantly, from its end which points towards the rear portion to its opposite, i.e. front end. The region at the front end of the front portion is wider in the direction of the transverse axis than the region at the rear end of the front portion. The rear portion can widen, in particular constantly, from its end which points towards the front portion to its opposite, in particular rear end. The region of the front end of the rear portion can exhibit a smaller width in the direction of the transverse axis than the region at the rear end of the rear portion. The width of the rear end region of the rear portion can preferably be smaller than or also larger than or as large as the width of the front end region of the front portion. The front portion and rear portion are preferably arranged with respect to each other such that their engaging edges lie on a shared curve, in particular having a shared radius. 
         [0016]    The arrangement consisting of the front portion and the rear portion can exhibit a sidecut which—between the bearing points formed in the region of the front end of the front portion and in the region of the rear end of the rear portion—is at its largest in the region of the rear end of the front portion or in the region of the front end of the rear portion. In particular, the sidecut depth is at its largest in this region. The sidecut depth can for example be 32 mm, thus forming a radius of 10 m at a distance between the bearing points of 1600 mm. The sidecut or sidecut depth onto the curve on which the engaging edges of the front portion and the rear portion lie can be at its greatest in the region in which the front and rear portions point towards each other. In other words, the front and rear portions of the sports equipment could be obtained by cutting through a conventional carving ski in the region of its smallest width transverse to the longitudinal axis, in particular along the transverse axis. 
         [0017]    In accordance with the invention, the front portion and the rear portion are connected to a crosspiece. The crosspiece can be a part which is separate from the front and rear portions. The crosspiece preferably spans a region in which the front and rear portions point towards each other, in particular without being fastened to this region and/or with a gap between this region or the front and/or rear portion. In embodiments in which the ground surface contact means is a sliding means in particular, the crosspiece exhibits a greater moment of resistance to flexing about the transverse axis than the front and rear portions. The crosspiece also exhibits a higher torsional capacity than the front and rear portions. The crosspiece can therefore be regarded as rigid as compared to the front and rear portions. Due to the greater rigidity of the crosspiece, torsional moments generated when turning can therefore be channelled via the relatively rigid crosspiece into the front and rear portions. This results in a significantly reduced deformation of the ski and/or the front and rear portions as compared to a standard ski, whereby the edge engagement is maintained during turning. For conventional carving skis have the problem that due to their large sidecut and high flexibility about the transverse axis, a torsion is generated which causes the region of the binding to be put on edge at a greater angle than the region of the front end and rear end of the ski. During extreme turning or in the event of skiing errors, i.e. when the centre of gravity is shifted towards the front or towards the rear in relation to the design point, the ski can slip away, which can even lead to a fall. 
         [0018]    In generally preferred embodiments, the crosspiece is fastened to the front portion between the end which points towards the rear portion and its opposite end, in particular via a joint, and is fastened to the rear portion between the end which points towards the front portion and its opposite end, in particular via a joint. 
         [0019]    The crosspiece can in particular be connected or fastened to the front and rear portions via the joints only. The region of the crosspiece which is arranged between the joints is preferably self-supporting, i.e. substantially disconnected from the first and second portions, or spans the region between the joints in a self-supporting manner. However, this should not necessarily exclude the possibility of the region of the crosspiece arranged between the joints coming into contact with the front and rear portions or the joint arranged between these portions. A spring element and/or a damping element could for example be arranged between the self-supporting portion of the crosspiece and the front portion, the rear portion and/or the joint. 
         [0020]    The joint which connects the crosspiece to the front or rear portion is preferably a pivoting joint. The pivoting joint can comprise at least one or only one rotational degree of freedom. The pivoting joint is preferably connected rigidly about the longitudinal axis to the front and rear portions for a pivoting movement of the crosspiece relative to the front and rear portions, in particular without a rotational degree of freedom about the longitudinal axis. The joint is preferably configured such that it permits a pivoting movement between the crosspiece and the front portion and between the crosspiece and the rear portion about the transverse axis, in particular with a rotational degree of freedom about the transverse axis. The pivoting axis of the respective pivoting joint is therefore parallel to the transverse axis, i.e. parallel to the ground surface, and transverse to the longitudinal axis of the sports equipment. The pivoting joint could in principle permit a pivoting movement between the crosspiece and the front portion and between the crosspiece and the rear portion about the vertical axis, although this is less preferred. It is therefore particularly preferred if the pivoting joint permits a pivoting movement about the transverse axis only. Connecting the front and rear portions to the crosspiece by means of pivoting joints which can be pivoted about the transverse axis enables the flexural rigidity of the system to be reduced and correspondingly adjusted, irrespective of the torsional rigidity. In particular, this ability to pivot means that the rollers or engaging edges better follow the ideal motion curve during turning. 
         [0021]    Another advantage of the arrangement of the pivoting joints described above is that shifting the force of the skier exerted on the crosspiece towards the front or towards the rear along the longitudinal axis only increases or reduces the reaction forces on the front pivoting joint and the rear pivoting joint. The transmission of a moment about the transverse axis from the crosspiece to the front and rear portions is substantially prevented or at least reduced by means of the pivoting joints. The pivoting movement could for example be damped by means of a damping member which is arranged kinematically between the crosspiece and the front portion and/or between the crosspiece and the rear portion. Correspondingly, a spring could also impede the pivoting movement and/or transmit torque about the transverse axis from the crosspiece to the front portion and/or rear portion. To this end, the spring would likewise be arranged kinematically between the crosspiece and the front portion and between the crosspiece and the rear portion. 
         [0022]    In the design of the sports equipment, a separate design point can be provided for the front portion, and a separate design point can be provided for the rear portion. By configuring the sports equipment to include the crosspiece, the line of application of the reaction force exerted on the front portion can pass through the design point. To this end, the pivoting joint is fastened to the design point. The same correspondingly applies to the rear portion. Since the forces then constantly act into the design point, and the transmission of moments about the transverse axis from the crosspiece to the front and rear portions is at least reduced, a reliable edge engagement or roller contact is constantly ensured, since the engaging edge or the rollers of the front and rear portions conform(s) to the motion curve, even after only a relatively small minimum force has been reached for this purpose, when the sports equipment is tilted upwards about the longitudinal axis, irrespective of the force. 
         [0023]    The front design point or the front joint is arranged in the region of the rear two thirds, in the middle third or in the rear half of the front portion in relation to the longitudinal axis. The rear design point or the rear joint is preferably arranged in the region of the front two thirds, in the middle third or in the front half of the rear portion in relation to the longitudinal axis. The agility of the sports equipment during turning can be influenced by the position of the joints in the front portion and rear portion. 
         [0024]    In principle, it would seem possible for the ends of the front portion and rear portion which project towards each other to be connected to each other in one part. The front portion and rear portion could then form a shared mount, in particular a ski or roller mount, on which the crosspiece is placed in the way described above. 
         [0025]    A moment could be transmitted from the front portion to the rear portion and vice versa by this arrangement. If this is to be prevented or at least reduced, the ends of the front portion and the rear portion which project towards each other can be connected such that the connection exhibits a lower flexural rigidity about the transverse axis than the front portion and the rear portion. It would then for example be possible to manufacture the front and rear portions integrally, wherein the part which connects the ends, which can be referred to as a joint, is designed to exhibit a very low flexural rigidity. An example of this would be the arrangement of suitable fibre-reinforced plastics such as for example aramide fibre reinforced plastics which exhibit low rigidity and simultaneously high elastic deformability. 
         [0026]    Alternatively, such a joint could be configured in the form of a hinge, wherein the front and rear portions respectively comprise parts of the hinge which interlock and are connected for example by means of a bolt. One portion can for example comprise a hinge part featuring at least one, for example two sleeve portions which are arranged in alignment and spaced with respect to each other. A hinge part arranged on the other portion and featuring at least one sleeve part can be arranged in alignment with the at least one hinge part of the first portion, in particular between the two sleeve parts, wherein the hinge parts are fixed to each other by means of a screw or bolt which is inserted through the sleeve parts of the two portions. The advantage of a hinge is that the joint only permits a pivoting movement about one pivoting axis between the front portion the rear portion. This for example transmits torsional moments about the longitudinal axis from the front portion to the rear portion and vice versa, while flexural moments about the transverse axis are not transmitted. If torsional transmission is not desired, a ball joint which permits torsional movements and pivoting movements can be used instead of a hinge. 
         [0027]    In another configuration, the ends of the front portion and rear portion which project towards each other can be connected to a flexible belt which can for example be formed from leather or plastic or from metal. The belt can for example be integrated, for example worked, into the front and/or rear portion during manufacture. Alternatively, the belt can be fastened to the front and rear portions using separate fastening options, such as for example by means of a rivet, screws or an adhesive connection. The belt can for example be a fabric belt. 
         [0028]    In general terms, the means which connects the ends which point towards each other can form a flexible or elastic connection. The means can for example comprise or be formed from a metallic and/or elastomeric material, such as for example rubber or natural rubber, and/or a leather-like material and/or a duroplast or thermoplast. A composite material which forms the connecting means can for example be formed from at least one or two of these materials. 
         [0029]    The connection between the ends of the front and rear portions which point towards each other could in principle comprise a spring member and/or damping member. The magnitude of the moment about the pivoting axis which is to be transmitted can be adjusted to almost any value by the spring member. Pivoting movements which the front and rear portions can perform relative to each other can be damped by the damping member. 
         [0030]    In advantageous developments, the sports equipment can be folded up, enabling it to be transported in a space-saving way. In particular, the transport length of the sports equipment can be reduced relative to its operational length. 
         [0031]    In preferred embodiments, the crosspiece is connected to the front portion by a front fastening means, wherein the fastening means is configured such that the crosspiece can be detached from the front portion. Alternatively or additionally, the crosspiece can be connected to the rear portion by a rear fastening means, wherein the fastening means is configured such that the crosspiece can be detached from the rear portion. In particular, one of the front fastening means and rear fastening means can be detachable, while the other of the front fastening means and rear fastening means is non-detachable. It is also for example possible for both fastening means to be non-detachable. Preferably, the front fastening means and rear fastening means respectively form the joint described above, in particular the pivoting joint for connecting the crosspiece to the front portion and the rear portion. 
         [0032]    The crosspiece can in particular comprise the means by which the sports equipment can be fastened to a person&#39;s foot. The means can in particular be a boot or a binding with which a boot can be fastened to the crosspiece. The front and/or rear fastening means can in particular be configured as a safety binding which releases the crosspiece for movement when a maximum load is exceeded. When the maximum load is exceeded, such as for example in the event of a fall, the crosspiece can detach from the front and/or rear portion or at least move far enough that the load is reduced, such that injury to the user is prevented. 
         [0033]    In particularly preferred embodiments, one of the front portion and rear portion can be connected to the crosspiece such that it can be pivoted about two pivoting axes, and the other of the front portion and rear portion can be connected to the crosspiece such that it can be pivoted about one pivoting axis, in particular only one pivoting axis. In particular in an embodiment in which the ends of the front and rear portions which point towards each other are connected to each other, in particular such that they are fixed against shifting but can be pivoted, it is advantageous if one of the front joint and rear joint can be pivoted about two pivoting axes, since this can compensate for changes in length when the first and second portions conform to the motion curve during turning. As an alternative to a joint featuring two pivoting axes, a joint—in particular, a pivoting and sliding joint—could be provided which on the one hand permits a pivoting movement about one axis and on the other hand permits a shifting movement between the crosspiece and the corresponding portion, in particular transverse or perpendicular to the pivoting axis or in the direction of the longitudinal axis of the portion. 
         [0034]    A damping element, in particular one made of rubber, can in particular be arranged between the crosspiece and the front portion and between the crosspiece and the rear portion. The damping element can in particular be arranged between the front fastening means and the front portion and between the rear fastening means and the rear portion. 
         [0035]    At least one of the front end of the front portion and the rear end of the rear portion can be raised and form a so-called shovel. If only one of the ends is raised, the sports equipment is substantially designed for motion in one direction only, i.e. in the direction in which the shovel points. If both ends are fitted with shovels, then motion is possible in both directions, i.e. forwards and backwards, using the sports equipment. 
         [0036]    The invention has advantages in the manufacture of the front and rear portions, in particular when they are designed for a sliding contact. In conventional skis, the sliding surfaces between the front and rear ends have to be curved or concave and exhibit a corresponding prestress. This proves to be complicated when manufacturing conventional carving skis, since the cross-sections of the ski change significantly over their length due to the large sidecut. In the sports equipment in accordance with the invention, the front portion and the rear portion can manage without prestress. Alternatively, however, they can also be prestressed. Correspondingly, the sliding surface of the front portion and/or rear portion can be level or concavely curved when the sports equipment has no load. Since prestress is not mandatory, the front and rear portions can be manufactured by means of methods which are more cost-effective than with conventional skis. One such method is for example an injection-moulding method in which for example the edges which are made of steel are inserted into a corresponding die, and a plastic which can for example be fibre-reinforced is injected around them. 
         [0037]    Another invention relates to the structure of a front or rear portion as described in this document, in particular a ski portion, or a sliding board, in particular a snow sliding board, preferably a ski, for example a ski as shown in  FIGS. 1   a - c . This invention can constitute an advantageous development of the sports equipment described above or subject matter which is independent of the sports equipment described above. 
         [0038]    It is an object to specify a sliding board which is simple in design and cost-effective to manufacture, and a corresponding manufacturing method. 
         [0039]    The elongated front and/or rear portion in the shape of sliding boards, in particular the ski portion, or the sliding board can comprise an upper tension-compression belt and a lower tension-compression belt which is spaced from the upper tension-compression belt, wherein the upper and lower tension-compression belts are encased in a plastic by means of plastic injection-moulding. This forms a shear-resistant bond between the tension-compression belts and the plastic, whereby embodying the tension-compression belts can significantly influence the flexural rigidity of the portion as compared to an embodiment with no tension-compression belts. If the portion is flexed about a flexing axis which is perpendicular to the longitudinal direction and parallel to the sliding surface, a neutral fibre is created between the upper and lower tension-compression belts. Within the technical-mechanics context of elastostatics, “neutral fibre” refers to the zone of a beam cross-section which does not change in length during a flexing process. The flexural stress in this zone is zero. 
         [0040]    The area moment of inertia and therefore the flexural resistance of the sliding board can be increased by increasing the distance between one or both belts and the neutral fibre or by increasing the cross-sectional area of one or both belts. The flexural resistance of the ski can be reduced by reducing the distance between one or both belts and the neutral fibre or by reducing the cross-sectional area of one or both belts. 
         [0041]    The upper and/or lower tension-compression belt can for example be formed from plastic, such as for example fibre-reinforced plastic, or metal such as for example an aluminium or steel alloy and can in particular be able to be both tensioned and compressed. The upper and/or lower tension-compression belt can be formed in the shape of a plate and for example formed from sheet metal. 
         [0042]    The injection-moulded material is preferably a plastic, such as for example a duroplast or preferably a thermoplast. The plastic can be foamed or unfoamed. 
         [0043]    In order to improve the bond and shear resistance, the upper and/or lower tension-compression belt can comprise a multitude of cavities, in particular perforations, into which the injection-moulded plastic is introduced or into which the injection-moulded plastic was introduced as the composite was being manufactured. The cavities permeate the belt from its upper side to its lower side, i.e. in the direction of its thickness, in particular its sheet metal thickness or plate thickness. The belts can therefore be formed in the manner of a perforated sheet. The cavities or at least some of them can for example be circular, elliptical or oval or can exhibit another, preferably rounded, non-circular shape. These shapes enable an advantageous stress distribution, which is improved even further if the longest extent of the cavity extends approximately in the direction of the longitudinal direction of the sliding board. The main axis of an elliptical cavity or perforation can for example point approximately in the direction of the longitudinal direction of the sliding board. 
         [0044]    The cavities of the upper and lower tension-compression belts or the cavities of engaging edges can be manufactured by being punched out. The upper and lower tension-compression belts can be manufactured by a separating method, in particular punching, or a separating and reshaping method, in particular flexural punching, or by another method known to the person skilled in the art. 
         [0045]    The upper tension-compression belt and the lower tension-compression belt can be pieces which are separate from each other or can be formed in one piece. If the belts are separate, they are in particular separated from each other by the injected plastic. If the belts are formed in one piece, they can in particular be connected by connecting portions which permeate the neutral fibre. The connecting portions can comprise a multitude of cavities which can be embodied as specified for the cavities of the tension-compression belts. The connecting portions are preferably arranged transverse to the sliding surface of the sliding board. 
         [0046]    The upper tension-compression belt or the plane in which the upper tension-compression belt lies, and the lower tension-compression belt or the plane in which the lower tension-compression belt lies, are preferably arranged approximately parallel to the sliding surface. 
         [0047]    The sliding board can comprise engaging edges, in particular steel edges, which preferably comprise cavities, in particular perforations. The cavities can be formed as described for the tension-compression belts. The cavities can overlap, in particular be congruent, with the cavities of the lower tension-compression belt. The engaging edges can be fused or soldered or connected via a connecting layer to the lower tension-compression belt or can abut against it. An adhesive is for example suitable as the connecting layer. The connecting layer exists even before the adhesive is injected. The engaging edges can thus be inserted into the injection-moulding die as one part together with the lower tension-compression belt when the sliding board is manufactured. The cavities preferably exhibit the same raster and/or size and/or shape as cavities of the lower tension-compression belt, which advantageously enables an unobstructed flow of the plastic between the upper side and lower side of the composite consisting of the lower tension-compression belt and the engaging edges. These cavities of the lower tension-compression belt are in particular arranged for example 1 to 10 mm away from the periphery of the lower tension-compression belt along the longitudinal direction and in the peripheral regions of the lower tension-compression belt. 
         [0048]    The upper side of the sliding board, i.e. the side facing away from the sliding surface, can optionally comprise a faceplate which can be provided with a pattern or with no pattern on its visible side. The faceplate can exhibit mechanical properties which are negligible with respect to the flexural rigidity and/or torsional rigidity of the sliding board or which contribute to the flexural rigidity and/or torsional rigidity of the sliding board. The upper side or the material of the faceplate is configured such that it exhibits a suitable adhesion for being printing on or other technologies for manufacturing a pattern. The upper side of the faceplate can alternatively or additionally comprise a structure which predominantly serves to furnish optical properties. The faceplate can be manufactured by injection-moulding one or more materials such as for example one or more plastics and can therefore be an injection-moulded part which however already exists before the plastic in which the tension-compression belts are encased is injected. 
         [0049]    The faceplate can comprise projections, in particular ribs, which are anchored in the injected plastic and/or can comprise projections which serve as spacers for the upper tension-compression belt. One or more projections of the faceplate can serve as both anchors and spacers. The injected plastic can be arranged between the upper tension-compression belt, or a plane in which the upper tension-compression belt lies, and the faceplate. The projection or projections can be anchored in the plastic during the process of manufacturing the sliding board, by injection-moulding plastic. The projections which serve as spacers serve to hold the upper tension-compression belt at a distance from the faceplate while the sliding board is being manufactured, such that the plastic can be dispersed between the faceplate and the upper tension-compression belt and/or can flow through the cavities of the upper tension-compression belt. In embodiments with no faceplate, the injection-moulding die in which the plastic is injected around the upper and lower tension-compression belts and preferably also the engaging edges can comprise the projections which serve as spacers for the upper tension-compression belt. 
         [0050]    The injected plastic can be arranged between the upper tension-compression belt, or a plane in which the upper tension-compression belt lies, and the lower tension-compression belt or a plane in which the lower tension-compression belt lies. The injected plastic can be arranged between the lower tension-compression belt, or a plane in which the lower tension-compression belt lies, and the sliding surface. 
         [0051]    The sliding board can therefore exhibit the following structure from top to bottom in relation to its height or thickness which is perpendicular to the length and width of the sliding board:
       optionally, a faceplate or a patterned element comprising projections or ribs;   the injection-moulded plastic;   the punched or perforated upper tension-compression belt;   the injection-moulded plastic and as applicable a connecting portion of the upper and lower tension-compression belts;   the punched or perforated lower tension-compression belt;   engaging edges, provided with cavities or perforations, in the peripheral region of the sliding board or lower tension-compression belt;   the injection-moulded plastic.       
 
         [0059]    The sliding board can be manufactured using the following steps. 
         [0060]    If provided, the faceplate—in particular, a patterned element—is inserted into an injection-moulding die, wherein at least one spacer in the form of one of the aforementioned projections is for example provided for the upper tension-compression belt. 
         [0061]    If provided, a tip protector or a part of the joint—in particular, hinge—for the front end and/or a protector or a part of the joint—in particular, hinge—for the rear end of the sliding board can optionally be inserted into the injection-moulding die. Dies for the faceplate, the tip protector and the protector for the rear end, into which the respective part can be inserted, can be provided in the injection-moulding die. If one of the faceplate, the tip protector and the protector for the rear end is not inserted as a separate part, the injection-moulding die can comprise corresponding die portions in which these parts are formed during injection-moulding. 
         [0062]    In preferred embodiments, a part of the joint can be formed during injection-moulding, i.e. the part of the joint is manufactured during injection-moulding. Alternatively, the part of the joint can be a constituent of the upper tension-compression belt or a constituent of the lower tension-compression belt. To this end, the front or rear end of the upper or lower tension-compression belt can form a part, such as for example a sleeve or an eyelet, which is manufactured by reshaping, in particular flexing. In another alternative, the part of the joint can be inserted into the injection-moulding die before injection-moulding, wherein subsequent injection-moulding at least partially injects the plastic around the part of the joint or at least partially anchors the part of the joint in the plastic. 
         [0063]    The upper tension-compression belt is inserted into the injection-moulding die, in particular into a part of the injection-moulding die which is intended for the upper side of the sliding board, and fixed. The lower tension-compression belt, to which the engaging edges are fastened, is simultaneously or subsequently inserted into the injection-moulding die, preferably together with the engaging edges, in particular into a part of the injection-moulding die which is intended for the lower side of the sliding board. Once these parts have been inserted, the injection-moulding die can be sealed. 
         [0064]    Plastic which is provided in a free-flowing state, in particular a heated thermoplast, is injected into the injection-moulding die, such that the plastic is injected around the upper tension-compression belt and the lower tension-compression belt. The free-flowing plastic is for example injected through an opening, in particular a hole in the upper tension-compression belt which is preferably larger than the cavities of the upper tension-compression belt, between the lower tension-compression belt (or its plane) and the upper tension-compression belt, or below the upper tension-compression belt, in particular towards the lower tension-compression belt. The free-flowing plastic is divided into a front plastic flow (in relation to the longitudinal direction of the sliding board) towards a front end or the tip, and a rear plastic flow (in relation to the longitudinal direction of the sliding board) towards a rear end, wherein the upper tension-compression belt is advantageously pressed against the spacers of the injection-moulding die or faceplate. If a lower tension-compression belt which is separate from the upper tension-compression belt is provided, the tension-compression belts can be pressed or held apart by the plastic flows. 
         [0065]    The divided plastic flows are respectively pressed through a multitude of the cavities of the upper tension-compression belt and/or lower tension-compression belt onto the other side of the upper and/or lower tension-compression belt, i.e. onto the lower side of the lower tension-compression belt or between the sliding surface and the lower tension-compression belt, whereby the plastic also flows through the cavities of the engaging edges and encases the engaging edges and preferably also forms the sliding surface, and onto the upper side of the upper tension-compression belt, whereby the plastic encases the projections of the optionally provided faceplate which serve as anchors or forms the upper side of the sliding board. 
         [0066]    The injection-moulding die can comprise one to five recesses or projections which extend in the longitudinal direction of the sliding board and are configured such that they form corresponding projections or recesses on the sliding surface of the sliding board, which advantageously increases the directional stability of the sliding board when it is in use. If they are arranged in the edge region of the sliding board, the recesses or projections can be arranged parallel to the edges or the sidecut curve of the sliding board, such as for example one projection or recess for each of the left-hand and right-hand edge of the sliding board. 
         [0067]    Once the injected plastic has solidified, for example by cooling the injection-moulding die, the injection-moulding die can be opened and the sliding board removed or ejected. 
         [0068]    Such a sliding board has the following advantages over already existing technologies:
       a lower number of parts;   a shorter manufacturing cycle per sliding board, i.e. about two minutes instead of 20 to 30 minutes as before;   almost no cuttings, waste material or cut-off material;   apart from sharpening the engaging edges, the sliding board does not need to be abraded after it has been removed from the injection-moulding die.       
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0073]    The inventions have been described on the basis of a number of advantageous embodiments. In the following, the inventions are described on the basis of figures. Features thus disclosed, each individually and in combination, advantageously develop the inventions. There is shown: 
           [0074]      FIGS. 1   a  to  1   c  a conventional ski, under different load conditions; 
           [0075]      FIGS. 2   a  to  2   c  an item of sports equipment in accordance with the invention, under different load conditions; 
           [0076]      FIG. 2   d  a modification of the sports equipment from  FIGS. 2   a  to  2   c;    
           [0077]      FIG. 3  another embodiment of an item of sports equipment in accordance with the invention, in a lateral view and a front view; 
           [0078]      FIG. 4   a  a cross-section through a sliding board from  FIGS. 1   a  to  1   c  or a front or rear portion for the sports equipment from  FIGS. 2   a  to  2   d;    
           [0079]      FIG. 4   b  an upper tension-compression belt for the device from  FIG. 4   a;    
           [0080]      FIG. 4   c  a lower tension-compression belt for the device from  FIG. 4   a;    
           [0081]      FIG. 4   d  edges for the device from  FIG. 4   a  or  5 ; and 
           [0082]      FIG. 5  a cross-section through a modified front or rear portion for the sports equipment from  FIGS. 2   a  to  2   d.    
       
    
    
     DETAILED DESCRIPTION 
       [0083]      FIG. 2   a  shows an item of sports equipment which is particularly designed for sliding on snow or ice. The sports equipment comprises a front portion  10  and a rear portion  20  which are configured to be elongated and the longitudinal axes of which are approximately aligned. The front portion  10  comprises a raised shovel  12  which points in the direction of motion. The front portion  10  and the rear portion  20  are respectively formed as snow sliding boards, in particular in the shape of skis. As shown in  FIGS. 2   a  to  2   d , the ends  11 ,  22  of the front portion  10  and rear portion  20  which point towards each other are disconnected, but could be connected to a pivoting joint  40  in the form of a hinge, as shown in  FIG. 2   d . The pivoting joint can in principle also be formed in another of the ways described in this document. The sports equipment shown in  FIG. 2   d  is in principle structured in the same way as the sports equipment from  FIGS. 2   a  to  2   c.    
         [0084]    The front portion  10  and the rear portion  20  can be elastically deformed transverse to their longitudinal axis, i.e. about their transverse axis. The first portion  10  and the second portion  20  are connected by means of a crosspiece  30 , the flexural rigidity of which about the transverse axis is significantly greater than that of the first and second portions  10 ,  20 , such that the crosspiece  30  can also be referred to as rigid. The crosspiece  30  is fastened to the first portion  10  and the second portion  20  by means of pivoting joints  13 ,  23 . The pivoting joints  13 ,  23  therefore form bearings for the crosspiece  30 , which are in principle torque-free, on the first portion  10  and the second portion  20 . If desired, a moment could be transmitted from the crosspiece  30  to the front and/or rear portion  10 ,  20  by a spring member arranged on the pivoting joints. A damping member could also be provided which acts kinematically between the crosspiece  30  and the front portion  10  and/or rear portion  20  and damps pivoting movements between the crosspiece  30  and the front portion  10  and/or between the crosspiece  30  and the rear portion  20 . 
         [0085]      FIG. 2   b  shows the sports equipment from  FIG. 2   a  when under a load during turning. The lateral edges which laterally enclose the sliding surfaces  14 ,  24  of the first and second portions  10 ,  20  conform to the motion curve, thus elastically bowing the first portion  10  and the second portion  20  such that the sliding surfaces  14 ,  24  are convex. The deformation is caused by the centrifugal force F which the user of the sports equipment exerts on the crosspiece  30 . The skier wears a ski boot which is fastened to the crosspiece  30  by means of a binding (not shown). Since the force F is arranged in the middle between the front joint  13  and the rear joint  23 , it is distributed uniformly between the joints  13 ,  23 , wherein the force F/2 acts on each of the joints. The line of application of the forces F/2 passes through the respective design point K of the front and rear portions  10 ,  20 . If a moment is applied to the crosspiece  30 , it is not relayed to the front and rear portions  10 ,  20 . Only the forces at the pivoting joints  13 ,  23  change. 
         [0086]    If the skier shifts their centre of gravity towards the rear ( FIG. 2   c ), the line of application of the force F moves further towards the rear and therefore nearer to the joint  23 . The joint  23  is therefore under the load of a force  3 F/ 4 , while the front joint  13  is only under the load of a force F/4. Despite the shift in the line of application of the force, a moment is not transmitted from the crosspiece  30  to the rear or front portions  10 ,  20 . The forces at the front joint  13  and the rear joint  23  also pass through the design point K of the front portion  10  and rear portion  20  under these load conditions. This ensures that the edge of the front portion  10  and rear portion  20  remains constantly conformed to the motion curve and does not rise up. 
         [0087]    It can be seen from  FIG. 2   d  that the crosspiece  30  is connected to the front portion  10  by a pivoting joint  13  which only permits a pivoting movement about one axis which is parallel to the transverse axis. The crosspiece  30  is also connected to the rear portion  20  by the joint  23 . The joint  23  exhibits two pivoting axes which are parallel to each other and parallel to the transverse axis. An intermediate piece is arranged between the two pivoting axes and performs a pivoting movement relative to the rear portion  20  and the crosspiece  30  when the rear portion  20  performs a pivoting movement relative to the crosspiece  30 . The intermediate piece serves as a length compensator when the front portion  10  is pivoted relative to the rear portion  20  by means of the hinge  40 . 
         [0088]      FIG. 3  shows an alternative item of sports equipment in the form of a roller skate which comprises a boot for accommodating a foot. A first pivoting joint  13  for a front mount  10  and a second pivoting joint  23  for a rear mount  20  are arranged on the lower side of the boot. The front mount  10  and the rear mount  20  can be pivoted in relation to the boot, the rigid sole of which forms a crosspiece  30 , by means of the pivoting joints  13 ,  23 . The front mount  10  comprises two bearings which each rotatably support a roller  15  relative to the front mount  10 . The rear mount  20  comprises two bearings which each rotatably support a roller  25  relative to the rear mount  20 . The mounts  20 ,  10  are disconnected, but could for example be connected via a joint as described in this document; alternatively or additionally, they could be connected via a spring and/or damping element. 
         [0089]    The four rollers  15 ,  25  shown in  FIG. 3  are arranged in alignment in the longitudinal direction of the crosspiece  30 , i.e. in the middle beneath the boot, as can be seen from the lateral view in  FIG. 3 . 
         [0090]    With conventional inline skates, so-called grinding occurs during turning, wherein usually four or five rollers arranged in a straight line are moved along the motion curve, generating a relatively high degree of abrasion on the rollers. The arrangement in accordance with the invention remedies this, since the rollers  25  of the rear mount  20  can conform to the motion curve independently of the rollers  15  of the front mount  10 . The same applies to the mount  10 . As can be seen from  FIG. 3 , the front mount  10  and the rear mount  20  can only be pivoted about one axis, i.e. the transverse axis, which is parallel to the rotational axes of the rollers  15 ,  25 . 
         [0091]    If the front mount  10  and rear mount  20  are connected by means of a pivot bearing  40 , as shown for example in  FIG. 2   d , the rear mount  20  is preferably connected to the crosspiece  30  by a joint  23  which permits length compensation. Such a joint is for example shown in  FIG. 2   d . The joint  23  exhibits two pivoting axes which are parallel to each other and parallel to the transverse axis. An intermediate piece is arranged between the two pivoting axes which performs a pivoting movement relative to the rear portion  20  and the crosspiece  30  when the rear portion  20  performs a pivoting movement relative to the crosspiece  30 . The intermediate piece serves as a length compensator when the front portion  10  is pivoted relative to the rear portion  20  by means of the hinge  40 . 
         [0092]      FIGS. 4   a  and  5  show a cross-section transverse to the longitudinal axis of a sliding board or ski, for example the ski from  FIGS. 1   a  to  1   c  or the portions  10 ,  20  in  FIGS. 2   a  to  2   d , which are referred to in the following as the ski  100 , wherein “ski” is to be understood to also mean a sliding board in general. 
         [0093]    The ski  100  comprises an upper side which is preferably formed by a faceplate  150  and arranged facing away from a sliding surface  160  on the lower side of the ski  100 . A patterned element can be arranged on the upper side and/or the faceplate  150  can comprise a patterned element. The sliding surface  160  is laterally enclosed or defined in the longitudinal direction of the ski  100  by an engaging edge  130  on each side, which is preferably formed as a steel edge. Reference is additionally made to the engaging edge or steel edge described in this document. The engaging edge  130  comprises a multitude of perforations  131  which are arranged such that they are spaced from each other by a grid spacing r ( FIG. 4   c ). The steel edges  130  are fastened directly to a lower tension-compression belt  120  via a connecting layer  135 , namely on the lower side of the lower tension-compression belt  120 , i.e. the side which points towards the sliding surface  160 . The steel edges  130  and the connecting layer  135  each comprise perforations  121  which are congruent with the perforations  131  of the lower tension-compression belt  120 . The perforations  121  are arranged along the longitudinal direction of the ski  100  in the peripheral region of the tension-compression belt  120 . The perforations  121 ,  131 , which are formed as elliptical holes whose main axes point in the direction of the longitudinal direction of the ski  100 , therefore form a passage between the upper side of the tension-compression belt  120  and the lower side of the engaging edge  130 . The engaging edge  130  is shown to be approximately L-shaped, wherein one limb is parallel to the tension-compression belt  120  and the other limb is approximately perpendicular to the first limb. The perpendicular limb preferably forms the sharpened edge which can engage with the ground surface when the ski  100  is in use. The connecting layer  135  can for example be an adhesive. 
         [0094]    An upper tension-compression belt  110  is arranged between the upper side of the ski  100  and the lower tension-compression belt  120  in relation to the height of the ski  100 . The lower tension-compression belt  120  is arranged between the upper tension-compression belt  110  and the sliding surface  160  in relation to the height of the ski  100 . 
         [0095]    The upper tension-compression belt  110  comprises a multitude of perforations  113  which can be configured as elliptical holes with a main axis extending in the longitudinal direction of the ski  100 . The upper and lower tension-compression belts  110 ,  120  are each arranged such that they are spaced from a neutral fibre when the ski  100  is flexed about a flexing axis transverse to the longitudinal direction and parallel to the sliding surface  160 , wherein the neutral fibre is arranged between the upper tension-compression belt  110  and the lower tension-compression belt  120 . 
         [0096]    The embodiment shown in  FIG. 5  substantially differs from the embodiment shown in  FIG. 4   a  only in that instead of being separate from each other, the upper and lower tension-compression belts  110 ,  120  are connected to each other, namely via one or more connecting portions  115  which extend through the neutral fibre and are preferably formed from the same material as the upper and lower tension-compression belts  110 ,  120 . The upper tension-compression belt  110  and the lower tension-compression belt  120  and the connecting portion  115  are formed from one part in the embodiment from  FIG. 5 . In the embodiment from  FIG. 4   a , the upper tension-compression belt  110  and the lower tension-compression belt  120  are formed by separate parts. The connecting portion  115  is preferably arranged at an angle of between 45° and 90° in relation to the upper tension-compression belt  110  and the lower tension-compression belt  120  and likewise comprises perforations  116  which can be shaped in the same way as the perforations of the upper and lower tension-compression belts  110 ,  120 . 
         [0097]    A plastic  140  which is injected by means of an injection-moulding method is injected around the upper tension-compression belt  110  and the lower tension-compression belt  120 . The plastic is preferably a thermoplast such as for example polyethylene. The plastic can be provided in a foamed or unfoamed form. Other suitable plastics are for example thermoplasts which are fibre-reinforced, for example glass fibre reinforced. Examples of these include polyamide 6 plastics and polyamide 12 plastics which are reinforced with glass fibres. The fibres can for example be short fibres exhibiting a length of for example 0.1 to 1 mm or long fibres exhibiting a length of for example 1 to 50 mm. Plastics which contain long and short fibres can still be injection-moulded. The fibres can be inorganic or organic reinforcing fibres. 
         [0098]    The plastic  140  is additionally arranged or injected in the perforations  111 ,  113 ,  121 ,  123  and  131 . This results in a substantially shear-resistant connection between the tension-compression belts  110 ,  120 , the edges  130  and the plastic  140 . In other words, the plastic  140 , the upper tension-compression belt  110 , the lower tension-compression belt  120  and the edges  130  form a material composite. The area moment of inertia or the flexural resistance of the ski  100  about the aforementioned flexing axis can for example advantageously be adjusted in the design of the ski  100  by the distance between the tension-compression belts  110 ,  120  and the neutral fibre and by the cross-section of the tension-compression belts  110 ,  120 . 
         [0099]    The plastic  140  can form the upper side of the ski  100 . If a faceplate  150  is used, the faceplate can for example comprise projections (not shown) around which the plastic  140  is likewise injected, such that a firm bond between the plastic  140  and the faceplate  150  results. These or other projections (not shown) of the faceplate  150  can serve as spacers for the upper tension-compression belt  110 , such that the plastic  140  can be dispersed between the faceplate  150  and the upper tension-compression belt  110 . 
         [0100]    The upper tension-compression belt  110  ( FIG. 4   a ,  FIG. 5 ) can comprise an opening  112  which is formed as a hole in the planarly formed tension-compression belt, as shown for example in  FIG. 4 . The opening  112  exhibits a larger cross-section than the perforations  111  and  113 . The opening  112  is arranged approximately in the middle, i.e. within the middle third, in relation to the front and rear ends of the ski  100 . In this example, the opening is likewise elliptical, wherein the main axis points in the longitudinal direction of the ski  100 . 
         [0101]      FIG. 4   c  shows a lower tension-compression belt  120  in which the front end is arched upwards and forms a tip of the ski. The rear end of the tension-compression belt  120  is likewise arched upwards slightly, though not as much as the front end. It can be seen in  FIG. 4   c  that each of the left-hand and right-hand peripheral region of the tension-compression belt  120  comprises a multitude of perforations  121  which are arranged such that they are spaced from each other by one or more grid spacings r in the longitudinal direction of the ski  100  and are for example arranged not more than 2 mm from the lateral edge of the lower tension-compression belt  120 , in order to advantageously establish a mechanical connection with the injection-moulded plastic. A multitude of uniformly distributed perforations  123  are arranged between the perforations of the left-hand and right-hand side and are arranged in a distribution up to the region of the upwardly arched front end of the lower tension-compression belt  120 . The openings arranged in the upwardly arched region or tip of the ski, which are larger than the perforations  123 ,  121 , can on the one hand save weight in this region and on the other hand can reduce the strength in this region, since somewhat lower mechanism demands are made on the arched region or tip of the ski. The openings can therefore be larger than or exhibit a different shape to the perforations arranged between the arched region or tip of the ski and the rear end of the ski  100 . 
         [0102]      FIG. 4   d  shows the left-hand and right-hand edges  130  for the ski  100  from  FIG. 4   a  or  FIG. 5 , which exhibit a smaller width, extending transverse to the longitudinal direction of the ski  100 , than the lower tension-compression belt  120  and comprise a multitude of perforations  131  which are arranged in a distribution in the longitudinal direction of the edges  130  or the longitudinal direction of the ski  100  and are spaced from each other by one or more grid spacings r. The perforations  131  are arranged such that they are congruent with the perforations  121  of the lower tension-compression belt  120 .