Abstract: A pressure differentially controlled valve for use in a two stage servomotor to prevent reversion from the second stage to the first stage. A first valve initially moves to transfer the output of a servomotor from a first piston to a second piston. A pressure differential responsive second valve prevents the output of the second piston chamber from being communicated to the first piston chamber by moving thereafter with the first valve until an input force is terminated.

Abstract: A hold-off resilient member for resisting movement of a plunger caused by an input force. The plunger initially moves a first control valve to permit air to enter a servomotor and develop an operational pressure differential in response to the input force. Further movement of the plunger will axially compress the resilient member as a function of input force to output force causing its peripheral surface to radially expand and actuate a second control valve. The actuation of the second control valve will permit air above atmospheric pressure to develop the operational pressure differential in response to the input force.