US Patent 8220806 Surface milling system

A cart assembly for milling a surface includes a cart having a support frame, a triad of wheel assemblies, and a triad of receivers. The triad of wheel assemblies is disposed on the support frame. Each wheel assembly includes an actuator that selectively extends and retracts a shaft of the wheel assembly to maintain the support frame at a given elevation. The triad of receivers is disposed on the support frame in a generally triangular configuration. The receivers are in electrical communication with the actuators of the wheel assemblies. The cart assembly further includes a milling assembly mounted to the support frame of the cart. The milling assembly includes a grinder adapted to remove material from a surface.