1. Field of the Invention
The present invention relates to a caster assembly and, more specifically, to a twin-wheel caster having a pair of wheels mounted for rotation on opposite ends of a common shaft and with the shaft supported by a body member.
2. Description of the Prior Art
In the prior art, twin-wheel casters have been constructed wherein a shaft member is supported by a body member and with wheels mounted for rotation on opposite ends of the shaft member. Generally, in the prior art, the shaft or axle includes a narrow groove which receives a ridge which is molded in an axial opening in a hub portion of a plastic wheel. The difficulty with this design is that with use of the caster the cyclical axial loadings applied to the wheel soon wear away the plastic ridge due to the sharp corners of the groove formed on the axle.
In one prior art attempt to eliminate the above problem, a wide groove at the end of the axle is used which groove approaches one-half of the depth of the axial opening in the wheel. The groove is positioned so that the axle ends in a knife-edged disc. The disc snaps over the ridge formed in the axial opening of an under-cut plastic wheel and, because of the unbalanced support provided by this design, the axle tends to wear into the wheel. This in turn effectively increases the under-cut portion adjacent the ridge thereby improving the retention of the wheel on the axle. The problem with this type of approach is that as the wheels wear in, the wheels tend to become wobbly.
Other prior art casters have included two grooves at the end of each axle, but these two grooves had sharp corners which would tend to wear away the under-cut portion of the plastic wheel adjacent to the ridges.