Abstract: The control valve for a two stage servomotor used in a braking system. A two stage servomotor has a housing with a stepped bore therein for retaining a piston and a cylindrical body. A deformable member adjacent the cylindrical body transmits a first operational input into the piston. A first operational input moves the piston and produces a pressure signal. The first operational input and the resistance to movement by the piston changes the shape of the deformable member. The changes in the shape of deformable member moves the control valve and allows the pressure signal to be communicated to the cylindrical body. The pressure signal acting on the cylindrical body provides an additional second operational force for moving the piston.

Abstract: In a servomotor having a two stage output created by the transfer of an operational force from a first diameter piston to a concentric second diameter piston, a control valve is concentrically located within the second diameter piston to provide for a uniform transition from the first diameter piston to the second diameter piston.

Abstract: A servomotor having a front shell with an annular wall in which an annular groove is located adjacent to an open end thereof. A rear shell has a peripheral ledge with radial lugs which are aligned in slots on the annular wall of the front shell. A diaphragm secured to a hub, which can move within the annular wall, has a bead with a contour which matches the annular wall from the annular groove to the slots. The peripheral ledge on the rear shell engages and compresses the bead of the diaphragm against the annular wall and groove of the front shell to separate a front chamber from a rear chamber when tabs on the open end of the annular wall lock the lugs against the slots.

Abstract: A movable wall assembly for use in a servomotor having a resilient diaphragm with a bead radially compressed in a groove on a hub by a backing plate to form a seal between a vacuum chamber and a power chamber. The diaphragm correspondingly axially urges the wall assembly into contact with the hub to prevent relative movement therebetween.

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.