US Patent 7395906 Brake actuator

A brake actuator including a chamber in which is provided a movable pressure responsive element which divides the chamber into first and second compartments, the brake actuator also including a valve assembly with an inlet which is connected to a source of pressurised fluid, an outlet which is connected to a volume within the brake actuator not including the second compartment, and an exhaust port through which fluid from the volume may be released, wherein the exhaust port of the valve assembly is connected to the second compartment.