US Patent 7270334 Wheel assemblies for use with load bearing platforms

A wheel assembly for supporting a load bearing platform includes a primary wheel and at least four secondary wheels that are of equal size. The primary wheel includes at least one planar member having an even number of axles at fixed locations extending perpendicularly therefrom with one secondary wheel mounted on each axle. The fixed locations are angularly equidistant apart and also equidistant from the central axis of the primary wheel. The diameter of each secondary wheel is greater than is the distance between locations, and adjacent secondary wheels are arranged to roll in separate, parallel paths.