Heretofore it has been common to form separate assemblies of rim and spokes for automotive steering wheels of the type referred to, and for example reference may be made to the Australien Pat. Nos. 535883 (60416/80), 534549 (66660/81) Ford, or the General Motors' U.S. Pat. No. 523159 (52771/79), these being the closest prior art known to the Applicant. However each of those specifications refers to an assembly, but it is common engineering practice to effect assembly of metal parts solely by welding, for example for joining a circular rim of tubing to a central hub by a pair of spokes welded therebetween. It is also common practice to envelop an entire metal assembly, or all except the hub, within a moulding of resilient polymeric material. Foam polyurethane with a dense skin is frequently used for this purpose.
The most highly stressed part of a steering wheel is where the spokes are joined to the hub. If the hub includes a flat plate, and if both hub and plate have ample thickness, good welding conditions exist and little difficulty is likely to be encountered. However if the hub has a circular base with an outstanding flange (a very commonly used shape), the welding conditions are not good and difficulties can be experienced in achieving the required strength. One object therefore is to provide improved welding conditions, and this is achieved by spokes of general `V` formation, the hub being welded to the apex of the `V`. This provides an improved welding condition, and the quantity of metal can therefore be reduced below what is required in prior art, without serious danger of loss of strength. The spokes can, for example, be tubular.
The other localities of weakness in the metal structure of steering wheels is where the spokes join the rim. Again there is a requirement for good welding conditions. Another object of the invention is to improve the spoke/rim arrangement, and this is achieved by the spokes and rim being a unitary member having ends joined by welds to respective intermediate portions of the member. By this arrangement, only one of the spokes is joined by a weld to the rim, and even if there is a weld failure, it is limited to one spoke only. This improvement, combined with the improved join between the spokes and hub, provides a metal structure with much less risk of failure than any previous steering wheel structure known to the Applicant, even if the weight of metal is less than in the prior art wheel.