Patent ID: 6896335

Claim:
A wheel assembly comprising: a) a molded plastic wheel adapted to mount to an axle including: i) a seamless annular body that is integrally molded from a first material exhibiting a first density and that includes a hollow hub having an axle bore and a plurality of hollow spokes that radially extend from the hub to a hollow box defined by planar first and second side wall surfaces and a tread surface that lies parallel to the axle bore, wherein seamless, hollow cavities of the hub, the spokes, and the box communicate with each other, and ii) a discrete annular tread piece having a generally U-shape with first and second side pieces that project to a connecting tread band and separately molded from a second material exhibiting a second density different from the first material and wherein the tread piece is stretch fitted over the box such that the tread band overlies the tread surface and the first and second side pieces abut the first and second side wall surfaces; wherein the first and second side wall surfaces respectively include first and second raised annular flanges; wherein peripheral edges of the first and second side pieces abut the first and second flanges; wherein the tread band has an external surface that includes a plurality of raised lugs; wherein the tread surface includes a raised annular band and the tread band includes an annular groove; and wherein the annular groove contains the annular band.