In particular, the present invention has reference to such wheels employed on vehicles for the purpose of reducing the loading per unit area, thereby to minimise the damage to the supporting surface through frictional and mechanical contact therewith, especially when turning.

The wheel of the present invention has particular but not exclusive application to a vehicle intended to be driven on a sensitive and easily damaged surface, for example, the grass of a golf course. One of the problems attendant upon the use of conventional wheels with pneumatic tyres on golf carts is that of changing direction, especially when moving on wet or heavy grass. The act of turning the wheel occasions damage to the grass and causes ruts and general surface disruption.

There have been various proposals for attempting to achieve the same objective and one particular idea involves the use of a plurality of ground engaging pads connected to and laterally across the tread of a pneumatic tyre in such a manner that the pads are rotatable about radial axes relative to the tyre. This arrangement purports to allow the tyre to move through a small angular movement whilst the pad or pads currently in contact with the ground remain in such contact until the wheel has rotated through a sufficient angle to bring the relevant pad or pads out of contact with the ground, the pad or pads returning to their normal position by virtue of resilient loading. The whole

of the pad across its full width moves in unison, and thus, when one extremity moves in a particular direction, the other moves in the opposite direction to the same extent. A serious drawback to that idea resides in its relative inflexibility and complexity, not only in use, but also and perhaps more especially, in manufacture.

An object of the present invention is to provide an improved wheel of simplified form but capable of spreading the wheel loading to avoid damaging a supporting surface.

According to the invention, there is provided a wheel including a plurality of spaced apart projections extending laterially and circumferentially of the wheel in such manner as, in use, sequentially to provide areas for contact, with a supporting surface, wherein the projections are provided on or integrally with a sleeve secured directly to the wheel to afford differential movement between each side of the wheel.

The sleeve may conveniently be in the form of a track securable to the periphery of the wheel which may usually include a hub carrying a tyre, the sleeve being securable to the tyre. The tyre may be solid or fluid filled. The term "fluid filled" as used herein, includes gas filled, for example, air or liquid filled or foam filled.

The sleeve may be in the form of a cage mountable on the wheel.

The sleeve may be annular or formable into an annular shape to circumscribe the wheel.

The means of securement of the sleeve to the wheel may be by the use of an adhesive. Alternatively, such means may be frictional by way of inflation of the tyre where the tyre employed is fluid filled. In a still further alternative, the means for securement may be provided mechanically by formations on the internal surface of the sleeve interengaging the surface of the wheel.

Conveniently, the sleeve is replaceable.

The projections may be equispaced around the periphery of the wheel and in the form of teeth. The spaces between the teeth may be of uniform rectilinear shape in the manner of slots and the teeth may give the appearance of castellations. In the alternative, the spaces between the teeth may be v-shaped or of other shape varying in cross section from the roots to the tips of adjacent teeth.

The projections are preferably of elastomeric material, such, for example, as natural rubber or a synthetic material giving sufficient flexibility to permit the differential movement between each side of the wheel. The sleeve may also be of the same material, the projections conveniently being integral therewith. Preferably, the elastomeric material is a laminated structure bonded either by heat or glue. For example, a neoprene, plastic, neoprene laminate.

By way of example, one form of wheel according to the present invention is described below with reference to the accompanying drawings in which: Figure 1 is a side view of the wheel;

Figure 2 is an end view of the wheel;

Figure 3 is a perspective view of the wheel; and Figure 4 is a diagrammatic representation of a golf cart.

Referring to the drawings, a wheel 1 includes a hub 2 mounted on an axle 4 rotatably held in bearings or bushes (not shown) provided in a front steering fork 6 of a golf cart 8. Similar wheels 1 are mounted at the rear of the cart on either side thereof.

Each wheel 1 also includes a pneumatically inflatable tyre 10 having a tread (not shown) on its circumference. A sleeve 12 of elastomeric material in the form of an essentially annular track comprises a central portion 14 having on each peripheral edge a plurality of equispaced projections in the form of teeth 16, the teeth being integral with the sleeve and spaced one from the other by a rectilinear slot 18 to give the appearance of castellations. The central portion 14 is bonded to the tread of the tyre 10 by a suitable adhesive, whilst the projections are movable independently in relation thereto and thus in relation to the tyre, thereby to afford differential movement as between the sides of the tyre.

In use, with the wheels 1 of the present invention in place on the golf cart 8 the loading per unit area thereof is spread by virtue of the provision of the projections in the form of teeth 16, and thus the tread of the tyre is effectively enlarged by the presence of the sleeve 12. Accordingly, when moving along a straight path the wheels of the invention afford a gentler contact with a potentially vulnerable supporting surface, which would, in the case of a golf cart, be grass.

When a change in direction is required the front fork 6 of the cart 8 is turned through the desired angle. In so doing, the wheel also moves through the same angle, but the elastomeric nature of the sleeve 12 and the flexibility provided by the teeth 16 allow limited and differential movement as between the two sides of the wheel. The teeth on the relatively inner side will tend to move together to compensate whilst the teeth on the relatively outer side of the wheel will tend to move apart, the movement of the outer and inner series of teeth being independent of each other. The teeth sequentially move into and out of contact with the supporting surface and by virtue of the elastomeric properties of the material from which they are made recover their normal relative positions when out of contact with the supporting surface.

The wheel of the invention also accommodates variations in the contours of the supporting surface and in so doing, allows the super-mounted vehicle to cope with all manner of terrain whilst maintaining good adhesion with little if any damaging effect upon the surface.

It is to be understood that the wheel of the present invention can be used other than for golf carts which represent only one application.

The advantage of the present invention resides in its simplicity of construction and manufacture in comparison with earlier proposals whilst retaining efficacy in reducing the loading per unit area and therefore obviating or alleviating the damaging effect of ordinary wheel treads.