Hydraulically-operated changeover valve in braking system

摘要

The valve is for a system with regulated wheelspin, being mounted in the pipe between the pedal-operated master-cylinder and the suction side of a self-priming return pump, open when the master-cylinder is not in use, and shut by the pressure in the master-cylinder when this is in use. A first piston (5) is open to atmosphere at one end and spring-loaded (6) in the opposite direction, actuating a tappet (10) via a first diaphragm (3). The tappet passes through a valve seat (15) and actuates a plug (16) in a second chamber (14). The plug is fixed to a second piston (17) separating the second chamber from a third one (18). The master-cylinder is connected to the first (8) and third chambers, and the suction side of the pump to the second one. The seat diameter can be less than that of the second piston, which can be thrust towards it by a spring weaker than the first one. The tappet can be a separate component, guided in the axial direction in the first chamber.