US20080231019A1

US20080231019A1 - Cross-Country Ski with Wheels

Info

Publication number: US20080231019A1
Application number: US11/997,642
Authority: US
Inventors: Charles Villani
Original assignee: SPORTISSIMO SARL
Current assignee: SPORTISSIMO SARL
Priority date: 2005-08-04
Filing date: 2006-07-19
Publication date: 2008-09-25
Also published as: WO2007014858A2; EP1909931A2; EP1749556A1; EP1909931B1; WO2007014858A3; ATE424241T1; DE602006005494D1

Abstract

A cross-country ski with wheels generally has a chassis with a middle beam and two supports for wheels, one being located in front of the middle beam and the other at the rear. A front wheel is mounted on the front support and at least one rear wheel is mounted on the rear support. The front support has an articulation situated in front of the front wheel whereby permitting the front wheel to pivot about an axis located in a longitudinal plane and vertical with regard to the cross-country ski with wheels.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates in general to a cross-country rollerski, intended for cross-country skiing on ground without snow cover.

BRIEF SUMMARY OF RELATED ART

A conventional cross-country rollerski comprises a central bar, one wheel at the front and one at the rear of the central bar and a cross-country ski boot binding.
Normally, cross-country rollerskiing is practised on roads with a relatively smooth surface. This is because a conventional cross-country ski is poorly suited to woodland or rough trails. Since the wheels are generally small, there is a considerable risk that they may jam. Furthermore, with traditional cross-country rollerskis, the skier takes corners by lifting one of his skis so as to redirect it. To apply this technique while on the move requires a degree of experience. Moreover, it is not always suitable for uneven ground because the skier is hesitant about lifting a ski.
Another problem encountered by a sportsperson when practising cross-country rollerskiing is that of braking. Patent application FR 2 627 995 describes a rollerski comprising a Bowden cable brake on the rear wheel. A gripping ring is attached to the belt of the skier by means of a resilient cable. To brake, the skier takes hold of the gripping ring and pulls on the brake cable. The fact that a belt has to be worn and that the brake cables hang freely by the side of the legs is somewhat inconvenient. Moreover, to brake the skier has to use his hands, which are already holding the ski poles. It is therefore difficult to grip the ring, because the skier has to concentrate at the same time on coordinating the poles.

BRIEF SUMMARY OF THE INVENTION

A cross-country rollerski generally comprises a chassis with a central bar and two supports for the wheels, one at the front of said central bar and the other at the rear. One front wheel is fitted on the front support and at least one rear wheel is fitted on the rear support. It will be noted that the presence of a pair of rear wheels increases the stability of the rollerski, which will be appreciated by a beginner skier or one who wants to practise cross-country rollerskiing on unasphalted trails. On the other hand, a cross-country ski with just one rear wheel has the advantage of providing less resistance to forward movement and thus allowing faster travel. Apart from the parts described thus far, a conventional cross-country ski comprises a binding on the central bar for receiving a cross-country ski boot. The binding in particular allows the skier to lift his heel, which constitutes an additional fundamental difference between a cross-country rollerski and a roller skate.
According to one important aspect of the invention, the front support has a joint arranged in front of said front wheel allowing the front wheel to pivot about an axis lying in the longitudinal and vertical plane relative to the cross-country ski. This axis may be itself be substantially vertical or, in accordance with a preferred embodiment of the invention, be inclined forwards relative to the vertical by an angle of between 5 to 45 degrees, preferably between 15 and 35 degrees. A cross-country rollerski according to the present invention therefore has the advantage of a directional front wheel. With a conventional cross-country rollerski, a skier has to take corners in steps consisting of lifting one of his skis to give it a different direction from the ski remaining on the ground. Since, in a rollerski according to the invention, the front wheel is drawn, the user can corner while keeping one or both skis on the ground, simply by shifting his weight to the side towards which he wishes to turn. Of course, to take tighter corners, for example, or to turn on the spot, it is still possible to corner conventionally. In addition to the simplified technique for taking corners, the front wheel increases rolling comfort, more particularly on rougher ground. Thanks to its orientability, the front wheel may avoid small stones in its path. Consequently, a directional wheel is less likely to get completely jammed, which could cause the skier to fall over. A cross-country rollerski which is even better suited to rough ground advantageously comprises wheels with a larger diameter, for example of 10 to 15 cm.
More specifically, the front support may comprise a frame connected rigidly to the central bar with two lateral sides which extend on either side of the front wheel and join together in front of it. At the central bar end, the frame is preferably wider than the central bar. The frame width reduces towards the point where the sides of the frame join in front of the wheel. The wheel itself is fitted on a wheel holder (e.g. a fork element or a connecting rod), which is connected to the frame by the joint allowing the wheel to pivot. The lateral sides of the frame make it possible to limit the pivoting movement of the front wheel. Since the width of the frame reduces towards the front, the latter has, when viewed from above, a form resembling a teardrop or a triangle. The front wheel may pivot by an angle corresponding to the angle formed between the two lateral sides of the frame. This latter is preferably around 15 degrees.
To increase comfort still further, the front support comprises a shock absorber at the level of the joint. A shock absorber will be particularly appreciated on woodland trails or on damaged roads. Obviously, the rear wheel support may also be equipped with a shock absorber. For even more comfort and to provide optimum shock absorption, the wheels are advantageously inflatable.
To prevent the front wheel from colliding with the frame when cornering, the wheel holder may comprise limit stops cooperating with the two lateral sides of the frame. The pivoting movement of the front wheel is thus limited. The limit stops may be adjustable to allow the user to select the maximum angle which the wheel may form with the longitudinal axis of the ski.
Advantageously, the front support comprises recentring means for the front wheel. These recentring means may resiliently oppose inclination of the front wheel relative to the longitudinal axis of the ski and pull or push it into a position in which it is aligned with the cross-country ski. The recentring means may be arranged at the level of the joint but, in one preferred embodiment of the invention, the recentring means comprise springs arranged between the frame and the fork element of the front support. It should be noted that if the axis of the joint of the front wheel holder is inclined towards the front, the user can control the locking and also recentring of the front wheel by changing the lateral inclination of his skis.
The frame may comprise reinforcing means, such as plates or rods, extending over the front wheel.
A first embodiment of the present invention further proposes a brake of a design specific to a cross-country ski. The brake device proposed comprises a brake pad capable of acting on the rear wheel(s), a brake cable and a brake control lever. The latter is arranged so as to be able to actuated by the shin of a user of the cross-country rollerski. On actuation of the brake control lever, the brake cable is tautened so as to move the brake pad into a braking position. An improved brake for a cross-country rollerski is provided by the present invention. The brake allows the user to brake without having to adopt an unstable position. He does not need to use his hands to actuate the brake. The fact that the skier can use his ski poles to balance significantly reduces his risk of falling.
Preferably, the brake control lever may be actuated by a forward movement of the user's shin. To brake, the skier bends the knee and his shin pushes the brake control lever forwards. At the same time as braking, the user therefore lowers his centre of gravity, which gives him greater stability.
According to one preferred embodiment of the invention, the brake control lever may rock forwards when the skier lifts his heel without the brake pad consequently being engaged in a braking position. The technique of cross-country rollerskiing requires the skier to raise the heel of the foot backwards momentarily. The leg concerned therefore descends obliquely in a rearward direction and is thus liable to actuate the brake control lever if the latter does not follow the leg's movement. The fact that the brake control lever may rock forwards when the heel is raised without moving the pad into a braking position means that the skier can roll along without worrying about touching the brake control lever. To allow the brake control lever to rock, the brake device may comprise a means for reducing the tension of the brake cable when the skier's heel is raised.
Advantageously, the brake device comprises a spring which, when the brake control lever is not actuated, holds the brake pad in a rolling position and exerts tension on the brake cable to straighten up the brake control lever. The rolling position is defined as a position in which the parts of the brake device do not prevent the wheel from turning freely.
According to another preferred embodiment of the invention, the brake device comprises a brake lever, a brake pad, a brake cable and an actuator, said brake lever bearing the brake pad and being connected to the actuator by the brake cable, the actuator being capable of being moved into a braking position in which it pulls on the brake cable as the result of a forwards movement of the skier's knee. Advantageously, this actuator includes a reel to which a strap is attached which may be attached at the skier's knee and unwound from said reel. In this case, the actuator is fixed to the chassis so as to be able to turn relative to a horizontal transverse axis, the strap causing rocking of the actuator into the braking position when it is essentially unwound, i.e. when it is totally unwound and/or, if the reel comprises a strap return spring, when the force transmitted to the actuator by the return spring exceeds the initial tension of the brake cable. Preferably, the brake device comprises adjusting means allowing the skier to adjust the length of the strap as required. The brake device in this embodiment essentially exhibits the advantages of the embodiment described above. Relative to the latter, it does however require fewer moving parts and constitutes a simpler mechanism which is therefore potentially cheaper to manufacture. It should be noted that the word strap in this context denotes all types of preferably substantially inelastic cable, cord etc.
According to one interesting aspect of the invention, the rear wheel support comprises a truck (a skateboard axle for example) with shock absorption provided by an elastomer or, preferably, by springs. The chassis preferably comprises a part which is raised relative to the central bar, to which the truck is fixed. Advantageously, the raised part is joined to the central bar by means of a curved or oblique transitional part, which additionally imparts an elegant appearance to the ski.
A person skilled in the art will note that a cross-country ski with brake as described herein does not necessarily need to be equipped with a directional front wheel.
The total length of the cross-country ski is preferably between 60 and 90 cm, and more preferably between 60 and 70 cm. A short ski has a lower moment of inertia, which makes the sport easier to practise and makes it more attractive. With the pivoting wheel, the directional stability of the ski is not called into question by shortening of the ski. It will be noted that the cross-country ski may have a mechanism for varying its length, e.g. a telescopic central bar. Each user may thus adjust the length of the ski in accordance with his own needs.

BRIEF DESCRIPTION OF THE DRAWINGS

Other distinctive features and characteristics of the invention will be revealed by the detailed description of various advantageous embodiments given below, by way of example. Reference is made to the appended drawings, in which:

FIG. 1: is a longitudinal view of a front wheel support;

FIG. 2: is a horizontal view of the device of FIG. 1

FIG. 3: is a longitudinal view of a brake device for the rear wheel when actuated by the skier;

FIG. 4: is a longitudinal view of a brake device for the rear wheel when the skier is not actuating the brake but keeping his heel in contact with the ski;

FIG. 5: is a longitudinal view of a brake device for the rear wheel when the skier is raising his heel;

FIG. 6: is an isometric view of a preferred embodiment if a cross-country rollerski;

FIG. 7: is a side view of the cross-country rollerski of FIG. 6;

FIG. 8: is a plan view of the cross-country rollerski of FIG. 6;

FIG. 9: is a view from below of the cross-country rollerski of FIG. 6;

FIG. 10: shows a longitudinal section through the front wheel support of the cross-country ski of FIG. 6;

FIG. 11: is an isometric view of a detail of the brake device of the cross-country rollerski of FIG. 6.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a longitudinal view and FIG. 2 a horizontal view of a support 10 for the front wheel 12 of a cross-country rollerski according to a first embodiment. The support 10 comprises a frame 16, a fork element 18 and a joint 14, arranged in front of the wheel 12, which connects the frame 16 to the fork element 18. The wheel 12 is mounted on the fork element so as to be able to turn freely about its axis 34. Owing to the joint 14, the fork element 18 may pivot, together with the wheel 12, about the axis 20 passing vertically through the joint 14. The fork element 18 is held movably relative to the frame 16 by ball bearings 22, 24. The frame 16 is suspended on the fork element by means of a spring 26. A peg 28 is positioned on the axis 20 of the joint 14 and fixed to the fork element 18. At the bottom end, the peg 28 has a thread for screwing a nut 30 thereon. The ball bearing 24 rests on the nut 30 and serves to support the spring 26. The other side of the spring 26 rests against the ball bearing 22 and presses the latter against the upper wall of the cylindrical housing 32, which is firmly connected to the frame 16. The ball bearing 22 serves as a guide for the peg 28, which may perform a to-and-fro movement relative to the cylindrical housing 32 for the purpose of shock absorption. A limit stop 36, comprising for example a washer of polyethylene or Teflon, is arranged between the upper wall of the housing 32 and the fork element 18, to prevent these two components from hitting one another when the rollerski is loaded only slightly or not at all. The limit stop 36 advantageously comprises another ball bearing for reducing the friction between the cylindrical housing 32 and the fork element 18.
The wheel 12 is preferably an inflatable wheel with a diameter of from 10 to 15 cm. A larger wheel size allows better rolling over uneven ground, on which rollers with a normal diameter (6 to 8 cm) would get jammed. To prevent large wheels from making the skier too far from the ground, the frame 16 is situated below the axis 34 of the front wheel. It should be noted that the greater is the distance from ground to foot, the more difficult it is to remain balanced on the ski. Moreover, the risk run by the skier of spraining his foot in the event of a fall increases with the distance from the ground.
Viewed from above, the frame 16 assumes a shape resembling a teardrop. The width of the frame 16 to the rear of the wheel 12 is greater than the width of the central bar 15. The pivoting movement of the wheel 12 is limited by the angle formed between the two lateral sides of the frame 16. This angle is preferably between 10 and 15 degrees.
The fork element 18 descends from the joint 14 towards the axis 34 of the front wheel 12. Beyond the axis 34, relative to the joint, the arms of the fork element are extended to form limit stops 36. These strike against the frame 16 and so limit the pivoting movement of the wheel 12 about the axis 20. The limit stops 36 may comprise a buffer of resilient material for the purpose of shock absorption when the limit stops strike against the frame 16.
To recentre the wheel 12, the springs 38, 40 are arranged on both sides of the wheel 12 between the fork element 18 and the frame 16. When a corner is taken to the right, the rear of the wheel 12 moves leftwards. The left-hand spring 38 is compressed and the right-hand spring 40 is stretched. The springs 38, 40 therefore assist in recentring the wheel 12 until it is realigned with the central bar 15.
FIGS. 3, 4 and 5 show a longitudinal view of the rear part of the cross-country rollerski. A support 41 for the rear wheel(s) 42 is fixed to the central bar 15 to the rear of said central bar 15. The cross-country rollerski comprises a brake device with a brake pad 44, a brake cable 46 and a brake control lever 48. When a force 50 is exerted on the lever 48, the cable 46 is tautened and the brake pad comes into contact with the wheel 42.
The brake control lever 48 is arranged in such a manner on the central bar 15 of the chassis that it allows the skier to brake with the shin 64. At the level of the central bar 15 or close thereto, the lever 48 is mounted on a substantially horizontal and transverse pin 52, which allows the upper part of the lever 48 to pivot forwards. The pin 52 is held in a support element 66 so as to be able to slide at an angle relative to the rolling direction. To this end, the support element 66 has oblong holes 68 which are inclined relative to the horizontal and in which the pin 52 may slide. In a variant of this embodiment, the pin 52 is fixed to the support element 52, and the oblong holes 68 are provided in the brake control lever 48.
The binding 70 enables a cross-country ski boot 72 to be fixed to the central bar 15 in such a way as to be movable about an axis 74 situated at the front of the shoe 72 so that the skier can raise his heel. The binding 70 is additionally provided with a deflection element 76 which deflects the brake cable 46 towards a fastening point 54 on the brake control lever 48.
The cable 46 is deflected by a pair of deflection pulleys 56 and directed towards the rear wheel 42 through a cavity in the central bar 15. Another deflection pulley 58 directs the cable 46 towards a brake lever 60, which comprises the brake pad 44.
To brake, the skier bends the knee while keeping his heel in contact with the central bar 15 (FIG. 3). The shin 64 then pushes the top of the lever 48 forwards. The fastening point 54 is moved forwards, which increases the distance between the deflection element 76 and the fastening point 54. At the same time, the pin 52 slides obliquely forwards and the boss 78 of the brake control lever pushes on the cable 46. As a result, the brake cable 46 is tautened. The pulleys 58, 56 transmit the tension from the cable 46 to the brake lever 60 and the brake pad 44 is brought into contact with the rear wheel 42. A spring 62 between the brake lever and the support 41 is stretched when the brake is actuated.
When the skier releases the pressure on the control lever 48, the spring 62 straightens up the brake lever 60 and thus brings the brake pad 44 into the rolling position (FIG. 4). At the same time, tension is produced along the cable 46, which brings the brake control lever 48 back into its rolling position: the top of the lever 48 is moved backwards, whilst the tension in the cable 46 causes the pin 52 to slide backwards in the oblong guide holes 68.
For rolling, the pin 52 of the brake control lever 48 is held in the upper rear part of the oblong hole 68 by the tension in the cable 46. When the skier raises his heel, as shown in FIG. 5, the deflection element 76 of the binding 70 inclines forwards and moves closer to the fastening point 54 of the cable to the brake control lever 48. The tension in the cable 46 is thus released, which enables the brake control lever 48 to rock forwards without the brake being actuated.
When the cross-country rollerski has two rear wheels 42, these are preferably mounted so as to rotate on an axle which is able to pivot about a fixed axis of the central bar inclined relative to vertical. In this way, by shifting his weight sideways the skier may incline the cross-country rollerski to one side and thus cause locking of the rear axle, as with a skateboard. Advantageously, this locking device comprises a means for limiting inclination of the ski and locking.
One preferred embodiment of the invention is illustrated in FIGS. 6 to 11. The cross-country rollerski 100 comprises a chassis with a central bar 115, a front wheel support 110 and a rear wheel support 141. The central bar 115 is formed of a rectangular hollow profile element of aluminium, connected to the wheel supports 110, 141 by screws or welding. The wheels comprise tubed tyres 30 mm wide and 122 mm in diameter. The wheels, or at least one wheel, may be provided an antireverse bearing, which will facilitate practice of the sport.
The wheel support 110 comprises a frame 116, a fork element 118 and a joint 114, arranged in front of the wheel 112, which connects the frame 116 to the fork element 118. The frame 116 takes the form of a cage with reinforcing plates 117 extending over the front wheel 112. The frame 116 and the central bar 115 are joined together 119 by interlocking. They are held in position by clamping with screws through the central bar 115, inserts being provided in the frame 116.
The front wheel 112 is mounted on the fork element 118 so as to be able to turn freely about its axis 134. Owing to the joint 114, the fork element 118 may pivot, together with the wheel 112, about the axis 120. The pivot axis 120 lies in the vertical longitudinal plane of symmetry of the cross-country rollerski 100 and is inclined forwards by 30 degrees. Since the pivot axis is inclined forwards, relative to vertical, the front wheel 112 tends to align itself with the ski when the skier keeps the central bar 115 horizontal, i.e. when he is not subjecting it to any lateral inclination. Limit stops 136 arranged on the axis of rotation 134 of the front wheel 112 limit the pivoting movement of the front wheel 112 by coming to rest on the lateral sides of the frame 116.
As is shown best in FIG. 10, the fork element 118 comprises a cylindrical mount 180 arranged about the axis 120 of the joint 114. The mount 180 accommodates a shaft 181 fixed to the frame 116 of the front wheel support. The shaft 181 ends in a limit stop 182 formed, in this embodiment, by a thick washer screwed onto the shaft 181. The cylindrical mount 180 has, at the lower end, a part 183 of reduced internal diameter forming a limit stop. Rotation of the shaft 181 in the cylindrical mount 183 is facilitated by a ball bearing 184 and a bushing 185 accommodated between the limit stop 183 of the mount 180 and the shaft 181. For the purpose of shock absorption, an elastomeric ring 186 is arranged between the ball bearing 184 and the limit stop 182 of the shaft 181. The hardness of the elastomeric ring 186 may of course be selected as a function of the weight of the skier. The shaft 181 and the cylindrical mount 180 are preferably made of steel. Lubrication of the assembly is enabled by the screw passage 187, which is closed by a plastics cover 188.
The rear wheel support 141 of the cross-country rollerski 100 comprises a truck 145, on which are mounted the rear wheels 142. Trucks suitable for use in the present invention are available on the market as standard components and do not in principle need to be described in detail. In the embodiment illustrated, an aluminium truck has been selected with shock absorption provided by springs, but it would of course be possible to select a truck with elastomer-based shock absorption. Generally, the greater is the angle formed between the axis of the springs and vertical, the more maneuverable is the truck. In the present case, an angle of 45 degrees has been selected. The distance between the rear wheels is 105 mm. The part 143 of the rear wheel support 141 by which the truck 145 is fixed to the chassis is raised relative to the central bar 115. The connection between this part and the central bar comprises an oblique transitional member 147, made preferably of the same material as the central bar 115, and lateral reinforcing plates 149 which increase the stability of the connection.
The cross-country ski is provided with a brake device acting on the rear wheels. The brake device comprises brake pads 144 mounted on a brake lever 160 which serves to bring the brake pad 144 into contact with the wheels 142. The brake lever 160 is actuated by a brake cable 146 extending in a sheath under the oblique transitional part 147. The brake cable 146 is attached by its other end to a brake actuator 190 placed on the central bar 115 to the rear of the zone where the skier's foot rests. The brake actuator 190 may turn on a transverse horizontal axis 191 so as to pull on the brake cable 146 and actuate the brake. The actuator 190 is attached to the user's leg by a strap 192 attached on the one hand under the skier's knee and on the other hand to the actuator. The strap is fixed to the actuator by means of a reel 193. When the skier pulls on the strap 192, the latter unreels initially without the actuator 190 pulling on the brake cable 146. Once the strap 192 is fully unwound, pulling additionally on the strap 192 brings about rocking of the actuator 190 about the axis 191 and therefore actuation of the brake. The reel 193 is provided with a return spiral spring 194 for keeping the strap 192 taut at all times and thus preventing the latter from dragging on the ground or interfering with other components of the cross-country rollerski 100. It has already been stated that, during normal forwards movement (without braking), the skier raises the heel of the foot of the leg momentarily at the rear. The length of the strap 192 as well the wound length of the strap 192 are adjustable so that raising of the heel does not cause braking. If he wants to brake, the skier bends his knees and consequently pulls more on the strap 192 than if he raises his heel. The wound length of the strap 192 is adjusted such that the strap 192 is entirely unwound before the skier's knee is in its ultimate position during braking. Thus, it may be ensured on the one hand that the brake is actuated reliably when the skier assumes the braking position and on the other hand that braking is triggered only under this condition. Of course, the correct wound length of strap and total length of strap may vary from one person to another. However, identifying these correct lengths for an individual is a routine matter for a person skilled in the art. Preferably, the brake device comprises adjusting means for adjusting these parameters.

Claims

1-17. (canceled)

18. A cross-country rollerski comprising

a chassis with a central bar, a front support to the front of the central bar and a rear support to the rear of the central bar, wherein a front wheel is mounted on the front support and at least on rear wheel is mounted on the rear support and wherein the front support includes a joint in front of the front wheel that allows the front wheel to pivot about an axis lying in a longitudinal and vertical plane relative to the cross-country rollerski; and

a brake device with a brake lever, a brake pad, a brake cable and an actuator, wherein the brake lever bears the brake pad and is connected to the actuator by the brake cable, and wherein the actuator is configured in such a way as to be movable into a braking position, in which the actuator pulls on the brake cable, as a result of a forward movement of a knee or shin of a user of the cross-country rollerski.

19. The cross-country rollerski as claimed in claim 18, wherein the actuator comprises a brake control lever movable into the braking position by a forward movement of the user's shin, wherein, as a result of the brake control lever being moved into the braking position of the brake control lever, the brake cable is tautened to engage the brake pad into a braking position.

20. The cross-country rollerski as claimed in claim 19, comprising a binding on the central bar for receiving a cross-country ski boot and allowing the user of the cross-country rollerski to raise his heel, wherein the brake control lever is configured so as to rock forwards, when the user raises his heel, without thereby engaging the brake pad into its braking position.

21. The cross-country rollerski as claimed in claim 19, wherein the brake device comprises a spring, which, when the brake control lever is not held in its braking position by the user's shin, holds the brake pad in a rolling position and exerts tension on said brake cable to redress the brake control lever.

22. The cross-country rollerski as claimed in claim 18, wherein the actuator comprises a reel to which is attached a strap, the actuator being mounted to the chassis so as to be able to turn about a horizontal transverse axis, the strap being configured capable to be attached to the knee of the user of the cross-country rollerski and to be unwound from the reel in such a way as to cause the actuator to rock into said braking position by pivoting about said horizontal transverse axis when the strap has been essentially unwound from the reel.

23. The cross-country rollerski as claimed in claim 22, wherein the reel comprises a strap return spring.

24. The cross-country rollerski as claimed in claim 22, wherein the brake device comprises adjustment means allowing adjustment of the length of the strap.

25. The cross-country rollerski as claimed in claim 18, wherein the axis about which the front wheel may pivot is inclined forwards relative to vertical by an angle of between 15 and 35 degrees.

26. The cross-country rollerski as claimed in claim 18, wherein the front support comprises a frame connected rigidly to said central bar, the frame having two lateral sides which extend on either side of said front wheel and which join one another in front of said front wheel, the frame having a larger width than said central bar and the width of the frame decreasing towards the location where said lateral sides join, and wherein the front support also comprises a wheel holder connected by said joint to said frame, on which holder is mounted said front wheel.

27. The cross-country rollerski as claimed in claim 18, wherein said front support comprises a shock absorber at said joint.

28. The cross-country rollerski as claimed in claim 26, wherein said support comprises springs arranged between said wheel holder and said frame for recentring the front wheel.

29. The cross-country rollerski as claimed in claim 26, wherein the frame comprises reinforcement plates extending over the front wheel.

30. The cross-country rollerski as claimed in claim 18, wherein the rear support comprises a truck provided with springs or an elastomer to absorb shocks.

31. The cross-country rollerski as claimed in claim 30, wherein said chassis comprises a part raised with respect to the central bar and wherein the truck is fixed to this raised part.

32. The cross-country ski as claimed in claim 31, wherein the chassis comprises a curved or oblique transitional part connecting said raised part is connected to the central bar.

33. The cross-country ski as claimed in claim 18, wherein the central bar is a telescopic central bar.

34. A cross-country rollerski comprising

a chassis with a central bar, a front support to the front of the central bar and a rear support to the rear of the central bar, wherein a front wheel is mounted on the front support and at least on rear wheel is mounted on the rear support and wherein the front support includes a joint in front of the front wheel that allows the front wheel to pivot about an axis lying in a longitudinal and vertical plane relative to the cross-country rollerski;

a binding on the central bar for receiving a cross-country ski boot and allowing a user of the cross-country rollerski to lift his heel; and

a brake device with a brake lever, a brake pad, a brake cable and a brake control lever, wherein the brake lever bears the brake pad and is connected to the brake control lever by the brake cable, and wherein the brake control lever is configured in such a way as to be movable into a braking position by a forward motion of a user's shin, wherein said brake control lever pulls on the brake cable when the brake control lever is in its braking position and thereby engages the brake pad into a braking position.

35. A cross-country rollerski comprising

a brake device with a brake lever, a brake pad, a brake cable and a brake actuator, wherein the actuator comprises a reel to which is attached a strap, wherein the actuator is mounted to the chassis so as to be able to turn about a horizontal transverse axis, the strap being configured capable to be attached to the knee of the user of the cross-country rollerski and to be unwound from the reel in such a way as to cause the actuator to rock into a braking position by pivoting about said horizontal transverse axis when the strap has been essentially unwound from the reel, and wherein said actuator pulls on the brake cable when the actuator is in its braking position and thereby engages the brake pad into a braking position.