Pneumatic servo-drive mechanism for power braking

摘要

A pneumatic servomotor (1) for an assisted braking having a housing, separated by a diaphragm (5) into a first variable-volume chamber (3) and a second variable volume chamber (7) therein. During a. brake application a force applied to a control rod (13) moves to allow a first flap (19) to isolate the second chamber (7) from the first chamber (3) and thereafter allow a second flap (23) to open and allow pressurized assist fluid to be communicated to the second chamber (7). The diaphragm (5) has a lip (35) thereon that engages the housing to define a thrust chamber (41). On opening of the second flap (19) allows the pressurized assist fluid is initially communicated to the thrust chamber (41) and only after a predetermined travel of the control rod (13) is the pressurized assist fluid communicated to the second chamber (7) for creating a pressure differential between the fluid in the first chamber (3) and second chamber (7) to develop an output force to effect a brake application. On termination of the input force to the control rod (13) the lip (35) provides for one-way isolation to permit the discharge of the assistance fluid from second chamber (7) to allow for equalization of fluid pressure in the first (3) and second (7) chambers.