Patent ID: 7523995

Claim:
A self-propelled machine, comprising: a machine frame supportable by a plurality of ground engaging units; a support device connected between said machine frame and at least one of said ground engaging units, the support device including a lifting column having a lifting column axis oriented generally vertically relative to the machine frame, the lifting column being configured to controllably raise and lower said at least one ground engaging unit relative to the machine frame; a first actuator connected to said support device and located at a lower portion of the lifting column, and adapted to move said at least one ground engaging unit between projecting and retracted positions relative to said machine frame; a second actuator associated with said at least one ground engaging unit, wherein the second actuator is a rotary actuator located at an upper portion of the lifting column spaced apart from the first actuator along the lifting column axis, and adapted to cause at least a portion of the lifting column to rotate about the lifting column axis and to maintain the same rotational direction of said at least one ground engaging unit in each of said projecting and retracted positions; and a controller associated with and adapted to coordinate the actuation of said first and second actuators.