Abstract: Implement and steering actuators are selectively actuated through steering and implement control valves respectively by fluid power output of respective steering and implement pumps. A pressure compensator is provided for at times diverting excess fluid from the steering pump to the implement control valve, and the implement pump applies fluid pressure to the implement valve through an unloading valve that gives the charging of an accumulator by the implement pump preference over operation of the implement actuator. The sensing of loss of fluid power in the steering pump activates an emergency control valve to connect the accumulator to the steering valve and to disconnect the pressure compensator from the implement control valve.

Abstract: A four position hydraulic valve having a first power, a hold, a float, and a second power position is adapted for pneumatic control by enclosing the ends of the power spool in pneumatic chambers. A three position pneumatic valve having its two output ports connected respectively to the pneumatic chambers, drives the power spool from the hold position to either power position and from the float position to the hold position. A detent retains the powers spool in the float position after a second power position and a centering spring biases the power spool toward the hold position from either power position and the float position.