Patent 7712555 was granted and assigned to Clark Equipment Company on May, 2010 by the United States Patent and Trademark Office.
A hydraulic system includes first and second pumps, first and second motors, and three valves for selectively creating combined and basic hydraulic flow. The arrangement of valves permits combined flow to be provided to both motors in series to cause high speed operation of the motors, and permits combined flow to be provided to one motor and basic flow to the other motor. When applied to a vehicle, the arrangement provides a steerable high speed series arrangement of the vehicle's drive motors.