4473-1.doc Jockey wheel Field of Invention This invention relates to improvements in wheels and more particularly to small wheels used for trailers and caravans and the like, which are commonly 5 called a jockey wheel. Background Current jockey wheels generally come in two types. The first, or "premium", type of wheel generally has a metal rim with a separate rubber tyre mounted on the rim. The second, or "budget", type of wheel is entirely moulded in soft 10 rubber and thus squashes down under heavy loads and higher temperatures. This increases rolling resistance and over time will cause the jockey wheel to go "out of round" due to the poor memory of the material. Summary of the Invention In one broad form the invention provides a wheel and tyre combination 15 comprising a rim and a tyre formed in situ on the rim. In another broad form the invention provides a method of manufacturing a wheel and tyre combination, including providing a rim and forming the tyre on the rim. The method preferably includes providing a hub and rim assembly and forming 20 the tyre on the rim of the hub and rim assembly. Forming the tyre on the rim preferably comprises injection moulding the tyre on the rim. Preferably the rim includes a peripheral portion onto which the tyre is 4473-1.doc -2 formed. Preferably the peripheral portion includes a first surface that extends circumferentially about an axis of rotation. Preferably the peripheral portion includes at least one first protrusion that extends at least radially from the 5 first surface. In another broad form the invention provides a wheel comprising a rim, the rim having a peripheral portion adapted for mounting a tyre, the peripheral portion including a first surface that extends circumferentially about an axis of rotation and at least one first protrusion that extends at least radially from 10 the first surface remote from edges of the first surface. Preferably the at least one first protrusion comprises a series of protrusions spaced circumferentially upon the first surface about an axis of rotation. The at least one first protrusion preferably extends parallel to the axis of rotation but may extend at an angle other than 90 degrees to the axis of rotation. The 15 at least one first protrusion may extend circumferentially about the axis of rotation. The at least one first protrusion may comprise at least one continuous or discontinuous flange that extends around the axis perpendicular to the axis. The at least one first protrusion may have at least one aperture therein. 20 Preferably the at least one first protrusion extends radially from the centre of the first surface. Preferably the peripheral portion includes at least one second protrusion that extends circumferentially and at least axially relative to the axis of rotation and is spaced from the first surface. 25 Preferably the at least one second protrusion extends axially from one or more 4473-1.doc -3 first protrusions. A second protrusion may extend from two or more first protrusions. The at least one second protrusion may be continuous or discontinuous about the axis of rotation. The at least one second protrusion may have at least one aperture therein. 5 Preferably the at least one second protrusion comprises one or more continuous or discontinuous cylindrical portions that extend around the axis coaxial to the axis. The at least one second protrusion preferably extends parallel to the axis. The at least one second protrusion preferably extends from a free end of the at 10 least one first protrusion and more preferably extends over a major portion of the first surface. In a preferred form a series of first protrusions extend from the centre of the first surface and are spaced about the circumference. The second protrusion comprises a cylindrical tube like portion that extends from the free ends 15 axially on either side of the first protrusion so as to form a T-shaped cross section combination. The first surface may be cylindrical about the axis of rotation. In another broad form, the invention provides a combination of the wheel and a tyre, wherein the tyre surrounds at least part of at least one first protrusion. 20 The tyre may pass through at least one aperture in at least one first protrusion. The tyre may surround at least part of at least one second protrusion. The tyre may extend around and under at least one second protrusion. The tyre may pass through at least one aperture in at least one second 4473-1.doc -4 protrusion. The tyre and wheel may be physically locked together such that they cannot be separated. The tyre may be formed in situ on or about the rim. 5 The tyre may be injection moulded on or about the rim. In another broad form, the invention provides a method of manufacturing a wheel and tyre combination, comprising the steps of providing a wheel having the features described above and then applying a tyre on or about the rim of the wheel. 10 The tyre may be provided separately to the wheel and then mounted upon the wheel. The method may include forming the tyre in situ on or about the rim. The method may include forming the tyre by injection moulding the tyre on or about the rim. 15 Unless the context clearly requires otherwise, throughout the description and any claims the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to". Brief Description of the Drawings 20 Figure 1 is an exploded perspective view of a wheel and tyre assembly according to a first embodiment of the invention. Figure 2 is a side view of the assembly of figure 1.
4473-1.doc -5 Figure 3 is a front view of the assembly of figure 1. Figure 4 is cross sectional view of the assembly of figure 1 taken along lines AA of figure 2. Figure 5 is cross sectional view of the assembly of figure 1 taken along lines BB 5 of figure 3. Figure 6 is an exploded perspective view of a wheel and tyre assembly according to a second embodiment of the invention. Figure 7 is a side view of the assembly of figure 6. Figure 8 is a front view of the assembly of figure 6. 10 Figure 9 is cross sectional view of the assembly of figure 6 taken along lines AA of figure 7. Figure 10 is cross sectional view of the assembly of figure 6 taken along lines BB of figure 8. Detailed Description of Preferred and other Embodiments 15 Referring to the figures there is shown a wheel and tyre assembly 10, 110 according to two embodiments of the invention. The first embodiment is shown in figures 1 - 5, and the second embodiment is shown in figures 6 - 10. The same numbers are used to identify the corresponding components in the two embodiments. 20 The wheels 10, 110 have a combined hub and rim unit 12, preferably formed of a hard plastic, most preferably polypropylene. Other "hard" plastics may be used. The unit includes hub portion 14 and rim portion 16, with spokes 18 extending from hub portion 14 to support rim portion 16. The spokes 18 may be radial spokes of narrow cross-section as shown in figures 1 and 5, or may 4473-1.doc -6 take some other configuration such as the five spoke configuration shown in figures 6, 7 and 10. The hub portion 14 has a central passageway 20 for receiving an axle (not shown). Polypropylene has good bearing properties and does not need a bush inserted 5 into the centre of the hub, whereas the soft PVC/rubber of prior art budget jockey wheels does not and wears quickly. A bush may be provided if desired. The rim portion 16 comprises a surface 27 and a circumferentially extending portion 22, as seen in figures 4 and 9 that serves to aid in retention of the tyre on the rim. The wheel 10 has a solid tyre 24 that extends around the 10 circumference of the rim 16 and surrounds the portion 22. The portion 22 preferably comprises a series of protrusions 26 that extend generally radially from the surface 27 and that extend circumferentially about the rim. As seen in figures 4 and 9 these protrusions are narrower than surface 27. If desired the protrusions may be continuous, forming a single 15 circumferentially extending ridge or may be a series of arc like ridges extending part way about the circumference. The portion 22 also includes a ring 28. The ring 28 extends generally parallel to the axle on either side of the protrusions 26. The ring may be divided into two or more arc portions extending part way about the circumference. Both the protrusion 26 and ring 20 28 may be continuous or discontinuous. The tyre 24 is relatively thin radially and so may be made of a relatively soft plastic or rubber without significant distortion due to loading in use. This allows for good traction on slippery and sloped surfaces without distortion associated with prior art wheels moulded entirely in soft rubber. The wheel is 25 also much lighter than the older style so reducing the weight of the entire jockey wheel assembly.
4473-1.doc -7 The use of a structurally sound hub and rim unit 12 also enables support of high vertical load without noticeable deflection. As seen in figures 4 and 9, the tyre extends around and under the ring 28 and so sideways forces are unlikely to cause sideways movement of the tyre 5 relative to the rim. Whilst a T- shaped portion is preferred, the rim portion 16 may have other profiles. The profile preferably resists sideways movement of the tyre relative to the rim and also preferably resists radially outwards movement of the tyre relative to the rim. Thus one or more simple circumferentially extending 10 protrusions may be provided, which resist sideways motion. The one or more circumferentially extending protrusions may be continuous, so as to form a circular ridge or discontinuous. One or more sideways extending arms may be provided from the free end(s) of the protrusions that extend between a portion of the tyre and the rim so as to take the load from the tyre. 15 In the preferred form of the invention the tyre 24 is formed by direct moulding onto the hub/rim assembly 12. In the preferred form the wheel 10 is made by first moulding the hard plastic hub/rim unit 12. The hub/rim unit 12 is placed into another injection moulding toot and the soft PVC tyre 24 is over-moulded onto the rim. The 20 material of the tyre 24 extends into openings 29 between adjacent protrusions 26 and so the two parts are physically locked together and cannot be separated. This also prevents relative circumferential rotation of the tyre 24 and hub/rim unit 12. Whilst a continuous ring 28 and a continuous protrusion 26 may be used, the 25 use of discontinuous, discrete portions prevents circumferential rotation of the tyre relative to the hub/rim unit 12.
4473-1.doc -8 This method of manufacture also has the advantage of not requiring any labour for assembly of the tyre and rim after moulding. Later two hub caps 30 are pushed into place on either side, if required. Whilst not preferred, the tyre may be formed separately and then mounted on 5 the hub/rim assembly 12. As seen in figures 1 and 4 the spokes 18 are preferably recessed relative to the rim and hub portions so the hub caps 30 may be flush with the rim. When a hub cap is to be used, the hub portion 18 preferably has a non circular boss 32 that is received in a corresponding recess 34 on the hub cap 30, which 10 prevents rotation of the hub caps 28 relative to the remainder of the wheel. The features of the invention described or mentioned in this document may be combined in any combination of features where features are not mutually exclusive. It will be apparent to those skilled in the art that many obvious modifications 15 and variations may be made to the embodiments described herein without departing from the spirit or scope of the invention.