GB2344538A

GB2344538A - Skateboard with convexly curved wheels

Info

Publication number: GB2344538A
Application number: GB9930807A
Authority: GB
Inventors: Scott S Doane
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-12-12
Filing date: 1999-12-07
Publication date: 2000-06-14
Also published as: GB9930807D0; GB9827445D0

Abstract

A skateboard having relatively large diameter wheels 11 and 12, each having a convexly curved tread profile with a flat central portion 20. The wheels may be carried in bearings resiliently mounted for longitudinal movement and are mounted beyond the ends of the board, with their axes being approximately level with the board. Straps 15 and 16 receive the user's feet. A pivoted portion 14 at the rear may be spring-loaded and has a braking element underneath. The pivoted portion is also coupled through a one-way clutch to the rear wheel, so that the user can drive the board by pumping up and down on the pivoted portion.

Description

Sriowbosrd/Slcateboar7 The present invention relates to skateboards and the like.

A skateboard consists essentially of a board, roughly 1 m long, which is supported on small wheels similar to roller-skate wheels. A person standing on a skateboard can perform a variety of manoeuvres. Skateboards were deve] oped as a land-based equivalent or derivative of surfboards, and have been well known for some 3 decades.

More recently, snowboards have been developed. A snowboard is of roughly similar size to a skateboard, but has a smooth undersurface; it is used in a similar way to a skateboard but on snow rather than on hard surfaces.

The basic movement of a snowboard is slippage on the snow, similar to the movement of skis. But as with skis, a distinctive feature of a snowboard is that it can be steered by the user shifting their weight on it. This feature results from the shape of the snowboard, which has a narrowed waist at its central region, so that the sides are shaped rough ! y thus : X. If the rider leans say to the left, the snowboard is tilted laterally and its left-hand edge is pressed into the snow, producing a depression in the snow. That depression has a curved edge matching the curve of the snowboard, and the movement of the snowboard tends to follow round the curve of the depression. Of course, varying speeds and varying degrees of tilt allow an expert to achieve close control over the movement of the snowboard.

The general object of the present invention is to provide an improved skateboard which simulates, to some extent, the characteristics of a snowboard.

According to one aspect, the invention provides a skateboard having wheels with convexly curved tread profiles. The tread profile preferably has a flat central portion with sloping outer regions. The wheels are also preferably of relatively large diameter, and at least one wheel may be carried in a bearing which is resiliently mounted for longitudinal movement. The wheels are preferably mounted beyond the ends of the board rather than underneath it, with their axes being approximately level with the board.

Such a skateboard will move in the direction of its axis when it is level, with the central flat portions of the tread profiles of its wheels in contact with the ground. If the user shifts their weight to the side of the board, however, the board will tilt and the portion of the profile of the wheels in contact with the ground will shift to one of the two outer sloping regions of the profile.

As a result, the wheels will behave as rolling cones rather than cylinders, and the board will tend to follow a curved path. The axis of each wheel will intersect the ground, and the wheel will tend to follow a circular path about that point.

The width of the wheels is preferably relatively large, to ensure that the tilting of the board produces the desired path curvature. Within limits, the broader the wheels, the less sensitive the board will be.

The board may have straps on its upper surface for receiving the user's f eet.

The board may have a pivoted portion at the rear which is preferably spring-loaded and carries underneath it a braking element, so that the user can brake the board by pressing down upon the pivoted portion and so engagirg the braking element with the ground.

Ideally, for smooth curved motion the axes of the two wheels should be angled towards each other so that they share a single common point about which the board will rotate. Similarly, if the board becomes airborne and then lands slightly on the skew, the axes of the wheels should ideally be angled to compensate for the skew. According to another aspect, therefore, the invention provides a skateboard in which at least one of the wheels has its axle resiliently mounted for longitudinal movement of its bearing. The axes of the wheels can therefore converge when the board is following a curved path and at least one of the axes can skew if the board lands in a skewed state.

In addition to steering, it is also desirable to be able to drive a skateboard.

The usual techniques are to accelerate the board by suitable movements of the body (side to side and up and down), or to push repeatedly on the ground with one foot, as with a scooter.

According to another aspect, the present invention provides a skateboard with a pivoted portion at the rear which is preferably spring-loaded and is coupled through a one-way clutch to the rear wheel. By pumping up and down on the pivoted portion, the user can drive the rear wheel, which can then rotate freely when the pumping motion ceases, in a manner similar to driving a bicycle by pressing on the pedals and then allowing it to free-wheel. The pivoted portion may carry a braking element, the skateboard may have wheels with convexly curved tread profiles, and the wheels may have bearings resiliently mounted for horizontal movement, all as described above.

A skateboard in accordance with the invention will now be described, by way of example, with reference to the drawings, in which: Fig. I is a general top view of the skateboard ; Fig. 2 is a more detailed view of the front wheel; Fig. 3 is a more detailed view of the mounting of the front wheel; and Fig. 4 is a more detailed view of the rear of the skateboard.

Referring to Fig. 1, the skateboard comprises a platform 10, e front wheel 11, and a rear wheel 12. A strut 13, which may conveniently be formed from a steel tube suitably bent to shape, passes from the rear of the skateboard round the platform 10 and the front wheel 11. The platform is mounted on this strut, and the axles of the wheels 11 and 12 are also mounted on this strut. At the rear of the skateboard there is a subsidiary platform 14 which is pivotally mounted on the strut 13 so that it can rock about an axis parallel to the axes of the wheels. The platform 10 and the subsidiary platform 14 have straps 15 and 16 attached to them; the user can push their feet through these straps to hold themselves on the skateboard.

Fig. 2 is a front view of the front wheel 11; the rear wheel 12 is similar.

As shown, the wheel has a wide tread which is profiled to have a central horizontal portion 20 and two outer sloping portions 21; the diameter of the wheel (ie its central portion 20) may conveniently be around 150 mm. When the board is horizontal, the central portion 20 of the profile will make contact with the ground es shown at 22, so that the board travels stably in the direction of its long axis. If the board is tilted transversely, however, by the user shifting their weight, one of the outer portions 21 of the profile will make contact with the ground, as shown at 23. As a result, the board will tend to travel in a curved path.

The outer portion 21 of the profile is part of a cone, and a cone rolls around its vertex. The resulting centre of curvature of the path will therefore be located at the point where the axis of the cone, ie the axis of the wheel 11, rneets the ground plane 23.

The wheel 11 is mounted in bearings or mountings 24 (Fig. 3) which are supported in bearing frames 25 which are in turn mounted on the strut 13.

The bearing 24 can slide horizontally in the frame 25, and is resiliently urged towards the central position by spring elements 26. This allows the axis of the wheel to slew from strict perpendicularity to the long axis of the skateboard.

This allows the point where the axis of the wheel 11 meets the ground to move backwerds closer to the corresponding point where the axis of the wheel 12 meets the ground when the board is tilted, giving a smoother turning action. The wheel 12 can be similarly mounted at one or both sides, though this may complicate the driving mechanism described below.

If the skateboard has become airborne and then lands slightly skewed, then the wheels may be forced to skid and a jerk may result. The resilient mounting of one or both wheels will also allow the wheels to skew slightly in this situation, reducing such jerkiness.

The profile of the wheel 11 may be curved rather than consisting of three straight segments joining at sharp angles. This will allow the user to control the curvature of the path, by adjusting which part of the profile contacts the ground.

Further, the central portion 20 of the profile is preferably relatively smooth and hard, allowing a degree of sliding, whereas the outer portions 21 are preferably of a material and/or provided with a tread pattern which gives them a relatively good grip.

The subsidiary platform 14 is mounted via a pivot 30 (Fig. 4) on the ends of the strut 13. Spring means (not shown) bias this platform to the approximately horizontal position. This platform 14 has a braking element 31 attached beneath it at its rear as shown. The user can therefore brake the skateboard by shifting their weight to the back edge of this platform 14 and so bringing the braking element 31 into contact with the ground.

The rear wheel 12 has a drive capstan 35 mounted on its exle 36 (Fig. 4).

The capstan 35 is spring biassed to rotate clockwise against a stop (not shown), and is coupled to the wheel 12 via a one-way type clutch like the free-wheel mechanism of a bicycle. The wheel 12 can therefore rotate freely while the capstan 36 is stationary, but a rapid pulse of clockwise rotation of the capstan drives the wheel 12. The capstan 36 has a drive cord or chain 37 attached to its circumference. This chain 37 passes over a pulley 38 and has its other end attached to the front end of the subsidiary platform 14.

The effect of this arrangement is that the user can drive the skateboard, by shifting their back foot to press down rapidly on the front edge of that platform. This will pull the chain 37 over the pulley 38, and rotate the capstan 35 sharply anticlockwise. The wheel 12 will also be rotating anticlockwise (as seen in the drawings), but if the chain 37 tries to rotate the capstan faster than the wheel 12, the one-way clutch will engage and the capstan will drive the wheel -12. The user can thus accelerate the skateboard.

This drive arrangement for the rear wheel can of course be provided on both sides the skateboard if desired.

Alternatively, the drive cord could be attached to some part of the user's body, such that appropriate movement of the body part drives the capstan.

Claims

Claims 1 A skateboard having wheels with convexly curved tread profiles.
2 A skateboard according to claim I wherein the tread profile has a flat central portion with sloping outer regions.
3 A skateboard according to either previous claim wherein the wheels are of relatively large diameter.
4 A skateboard according to any previous claim wherein at least one wheel is carried in a bearing which is resiliently mounted for longitudinal movement.
5 A skateboard wherein at least one wheel is carried in a bearing which is resiliently mounted for longitudinal movement.
6 A skateboard according to any previous claim wherein the wheels are mounted beyond the ends of the board with their axes being approximately level with the board.
7 A skateboard according to any previous claim wherein the width of the wheels is relatively large.
8 A skateboard according to any previous claim wherein the board has straps on its upper surface for receiving the user's feet.
9 A skateboard according to any previous claim wherein the board has a pivoted portion at the rear.
10 A skateboard with a pivoted portion at the rear.
11 A skateboard according to either of claims 9 and 10 wherein the pivoted portion is spring-loaded and carries underneath it a braking element, so that the user can brake the board by pressing down upon the pivoted portion and so engaging the braking element with the ground.
12 A skateboard according to any of claims 9 to 11 wherein the pivoted portion is spring-loaded and is coupled through a one-way clutch to the rear wheel.
13 A skateboard substantially as herein described and illustrated.
14 Any novel and inventive feature or combination of features specifically disclosed herein within the meaning of Article 4H of the International Convention (Paris Convention).