US Patent 8210556 Midwheel drive wheelchair with independent front and rear suspension

A wheelchair includes a frame, and a front pivot arm pivotally mounted to the frame at a front pivot point, the front pivot arm having a caster for supporting the frame. A rear pivot arm is pivotally mounted to the frame at a rear pivot point, the rear pivot arm having a caster for supporting the frame. A ground engaging mid-wheel drive wheel is connected to the frame. A linkage connects the front and rear pivot arms to each other in a manner such that an upward or downward rotation of one of the pivot arms about its pivot point causes rotation of the other pivot arm about its pivot point in an opposite rotational direction.