Abstract: A diaphragm brake booster includes a housing, a movable power piston disposed in the housing, a diaphragm inner periphery thereof being secured to the power piston, a valve member disposed in the power piston for generating a pressure differential between the two chambers defined by the power piston and the diaphragm upon manual operation. The brake booster further includes a key member for restricting the movement of the valve member, the key member being supported on the power piston near the portion where the inner periphery of the diaphragm is secured.

Abstract: Improvements in a servomotor including a retainer coupling an annular diaphragm having its outer periphery sealingly attached to the servomotor housing and an axially movable power piston within the housing. The piston has a boss axially extending through the annular diaphragm and an external flange extending radially from the outer periphery of the boss for positioning adjacent the diaphragm, the diaphragm and power piston forming two pressure chambers. A valve member is slidably and sealingly disposed in a bore formed in the boss of the power piston for regulating pressure in the pressure chambers. The retainer has an axially extending cylindrical seat in which the boss is tightly positioned and a flange radially extending from the seat for pressing an inner portion of the diaphragm against the power piston flange.