Patent Application
20130106069
The present invention is in the area of sport and recreation equipment.
Modern carving or parabolic snow ski can be easily turned by applying leg pressure on the edges which is transmitted through the camber shape to the front and rear part of the concave side cut. Grass ski or in general dry surface ski is designed to simulate snow ski. The most commonly used grass ski design is based on the rolling tread disclosed in U.S. Pat. No. 4,572,528. This design although ensures smooth riding makes turning quite difficult. Tight turns, critical for speed control, are very hard to achieve making such device unsafe and unsuitable for most recreational skiers. This type of ski is mainly used for racing and summer training of competitive snow skiers.
The idea of applying swivel casters to devices that simulate ski was disclosed as early as 1974 in U.S. Pat. No. 3,827,706 and revisited a decade ago in US Patent 2002195788 which discloses a wheeled device referred to as street-ski. The street-ski design has been commercially implemented as a board device known as T-board. The T-board turns in response to shifting the weight of the rider on the board towards the edge of the board. The casters mounted on the underside of the T-board are equipped with springs that resist pivoting and return the wheels to the straight position.
U.S. Pat. No. 7,195,259 discloses in
Another device aimed at simulation of snow ski is disclosed in U.S. Pat. No. 7,784,833. It uses four fixed wheels mounted near the centre of a narrow platform and two swivel casters with springs that resist pivoting at both ends. However, since the casters are mounted in the same direction this device will not simulate carving.
The objective of the invention presented herein is to provide wheeled skiing apparatus which does not suffer from safety problems such as speed wobbles caused by swivel caster flutter and simulates kinematics of carving ski. Further objective of the current invention is to improve safety of skiing on wheeled devices by providing a simple braking mechanism.
In accordance with the present invention there is provided a dry surface ski apparatus that comprises a leading self-steering swivel caster, a trailing non self-steering swivel caster both mounted to the underside of an elongated platform supporting the skier, a steering system connecting the leading caster fork to the trailing caster fork which transmits the steering movement of the leading swivel caster to the steering movement in the opposite direction of the trailing swivel caster. The steering movement of the self-steering leading swivel caster is induced by rolling skier's knees in the required direction of turn. The turn is then tightened by the steering system which steers the trailing caster wheel in the opposite direction thus making it similar to the trajectory of a flexed carving ski.
If flutter of the leading self-steering caster was to occur the oscillation would be transmitted by the steering system to the trailing non self-steering swivel caster. The ground friction forces acting on the trailing caster would then dampen the flutter.
In order to facilitate braking a wing like member is attached to the outer edge of each skier supporting elongated platform in front of the ski binding. When the skier plants ski poles in front of these wing like members the ground friction force of the ski pole tips is transmitted to the skis which allows slowing down and stopping.
Wheeled devices simulating modern carving skis by means of utilising self-steering swivel casters are prone to speed wobbles due to caster flutter.
In particular if the street-ski design disclosed in US Patent 2002195788 was to be applied to skis with skier's feet immobilised in boots bound to the platform, edge pressure could only be applied by rolling the knees sideways. Such edge pressure force would not be very strong and thus require soft springs especially in the leading swivel casters to allow tight turns. However, soft springs would make the swivel casters prone to flutter and result in potentially dangerous speed wobbles.
Another problem with the design of street-ski is that many skiers especially at the beginner to intermediate level have natural tendency to perform rotary turns by twisting their feet. This would result in both leading and trailing swivel casters turning in the same rather than the opposite directions causing drift movement instead of a carved turn.
The design disclosed in
A fundamental safety problem of wheeled devices simulating skis is lack of ability to brake.
The problem of flutter is solved by connecting the leading self-steering swivel caster to a non self-steering trailing swivel caster by a steering system in such a way that when the leading caster is steered in one direction by the skier the trailing caster is automatically steered in the opposite way. Ground friction reactive forces acting on the trailing caster resist steering and are transmitted through the steering system to the leading caster thus dampening flutter if it was to occur. At the same time the leading and trailing swivel casters which turn in the opposite directions in a synchronised manner prevent drift movement and closely simulate flexing of carving ski along its entire length.
In order to facilitate braking a wing like member is attached to the outer edge of each skier supporting elongated platform in front of the ski binding. When the skier plants ski poles in front of these wing like members the ground friction forces acting on the ski pole tips are transmitted to the skis which allows slowing down and stopping.
The invention offers significant improvement in safety and kinematics of wheeled devices simulating modern carving ski. It eliminates speed wobbles caused by swivel caster flutter and enables better speed control and braking.
As used herein a swivel caster whose swivel radius is greater than the radius of the caster wheel is referred to as a self-steering swivel caster. Such swivel caster can automatically align to the direction of travel. A swivel caster whose swivel radius is equal to the radius of the caster wheel is herein referred to as a non self-steering swivel caster. Such swivel caster cannot automatically align to the direction of travel.
The convention adopted in this document for describing similar elements appearing in different figures is such that the callouts to such elements have different leading digits inherited from the figure number but identical two-digit trailing parts. In particular callouts 100, 200, 300 and 400 refer to an elongated platform, callouts 101, 201, 301 and 401 refer to a leading self-steering swivel caster, callouts 103, 203, 303 and 403 refer to a trailing non self-steering swivel caster, callouts 207, 307 and 407 refer to the swivel axis of the leading self-steering swivel caster, callouts 210, 310 and 410 refer to the swivel axis of the trailing non self-steering swivel caster, callouts 209, 309 and 409 refer to the axle of the leading self-steering swivel caster, callouts 208, 308 and 408 refer to the axle of the trailing non self-steering swivel caster and finally callouts 220, 320 and 420 refer to a wing-like member.
Referring to
Said steering arms 202a and 202b are rigidly attached to respectively the right-hand and left-hand sides of fork of the leading caster 201. Similarly, there are steering arms 204a and 204b rigidly attached to respectively the right-hand and left-hand side of the fork of trailing caster 203. The left steering arm 202b of the leading caster is connected to the right steering arm 204a of the trailing caster by a tie rod 205. The right steering arm 202a of the leading caster is connected to the left steering arm 204b of the trailing caster by a tie rod 206. Said tie rods 205 and 206 are pivotably attached at the ends to said steering arms 202a, 202b and 204a and 204b and transmit steering movement of the leading caster to the opposite steering movement of the trailing caster i.e. if the leading caster turns left the trailing caster turns right and if the leading caster turns right the trailing caster turns left.
It is obvious that if tie rod 205 (alternatively 206) is sufficiently rigid the steering system only comprising steering arm 202b (alternatively 202a), steering arm 204a (respectively 204b) and tie rod 206 (respectively 205) will achieve the same functionality as the steering system comprising all these members. The advantage of the steering system having all the members above is that none of tie rods 205 and 206 has to be rigid, for instance they both can be cables.
If flutter of said swivel caster 101 occurs during travel the oscillations are transmitted to trailing swivel caster 103 and dampened by resistive ground friction of the wheel of said caster 103.
Preferably the forks of said leading and trailing casters are made from metal and the wheel rims are made from metal or plastic. Preferably the wheels have rubber tyres. Preferably said skier supporting elongated platform is made from a light composite material or light metal. Preferably the members of said steering system are made from metal.
There is a ski boot 118 attached to the supporting elongated platform 100 (200) between the leading and trailing casters by means of a ski binding. Preferably the supporting elongated platform 100 is shaped in such a way that its middle section is lowered towards the ground.
A wing like member 220 is attached to the outer edge of each skier supporting elongated platform in front of the ski binding. When a ski pole is planted in front of said member 220 the ground friction of the ski pole tip is transmitted by said member 220 to the elongated platform and causes the skier to slow down and stop.
The second preferred embodiment presented in
The third preferred embodiment presented in
It will be appreciated that applications of the present invention are not limited to skiing and the connected leading self-steering swivel caster and rear non self-steering swivel caster can be applied to other devices such as in-line skates and skateboards.
Although the present invention has been illustrated with reference to certain preferred embodiments, it will be obvious to those skilled in the art that it is not limited to the specifics set forth therein and modifications and variations especially with respect to the steering mechanism will be possible within the spirit and scope of the present invention. All such variations and modifications are intended to be covered by the present invention.
The application of the present invention is mainly as an off-season training device which can be used by skiers to improve their skiing technique and fitness. Since the device is primarily turned by rolling skier's knees in the direction of turn and sliding is impossible, the device is particularly suitable for learning the modern technique of skiing.
Testing of the proof of concept device built according to the first preferred embodiment confirmed its expected behaviour and gained favourable reviews by skiing instructors and coaches including former Olympic skiers.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011904527 | Oct 2011 | AU | national |
