Patent ID: 8007341

Claim:
A wheel assembly comprising: a shaft; and a pair of wheels rotatably connected to opposite ends of the shaft, each wheel comprising: an inner cover; an outer cover connected to and spaced away from the inner cover, thereby forming an annular open space between the outer cover and the inner cover; and a steering member sandwiched between the inner cover and the outer cover, the steering member comprising a motor, a rotating plate, at least two elastic elements equidistant from each other around the inner cover, and at least two pawls rotatably connected to the outer cover, the motor fixed on the inner cover and including a rotating shaft, the rotating plate fixed to the rotating shaft and driven by the motor to rotate about an axis that the rotating shaft rotates about, each elastic element connecting the rotating plate to each pawl, each pawl extending out of the annular open space by rotation of the rotating plate, thereby changing the radius of the wheel.