Pneumatic booster with floating reaction disc and dynamically cancellable reaction

Abstract

A pneumatic brake booster for a motor vehicle having a rigid casing (,) with a moving partition (,) to define a front chamber (,) and a rear chamber (,) therein. A pneumatic piston (,) carried by the moving partition (,) has a bore which retains a three-way valve (,). The three-way valve (,) is connected to an actuating rod (,) which acts on a plunger (,) to connect the front chamber (,) to the rear chamber (,) with a first pressure in a rest position and connects the rear chamber (,) to a second pressure in an actuation position. In the actuation position, a pressure differential develops across the movable partition (,) to create a boost force which is transmitted to a push rod (,) through a reaction disc (,) retained in a cup (,) to develop a braking force in response to an input force applied to the actuating rod (,). An intermediate member (,) located between the cup (,) and plunger (,) slides with respect to the piston (,) and plunger (,). During an emergency situation, members (,) of the intermediate member (,) secure the cup (,) to piston (,) and allow a braking force to be maintained by wheel brakes of a vehicle even if an operator terminates an input force.