Patent ID: 7395906

Claim:
A brake actuator including a chamber in which is provided a first movable pressure responsive element which divides the chamber into first and second compartments, the second compartment having mounted therein a resilient biasing element which may act on the first pressure responsive element to move the first pressure responsive element to reduce the volume of one compartment and increase the volume of the other compartment, and a first valve assembly with an inlet which is connected to a source of pressurised fluid, and outlet which is connected to the first compartment, and an exhaust port through which fluid from the first compartment may be released, the brake actuator also including a second chamber in which is provided a second movable pressure responsive element which divides the second chamber into first and second compartments, the first compartment being connected to a source of pressurised fluid via a second valve assembly and the second compartment having mounted therein a second resilient biasing element which may act on the second pressure responsive element to move the pressure responsive element to reduce the volume of one compartment and increase the volume of the other compartment, the second valve assembly including and exhaust port through which pressurised fluid from the first compartment may be released, both resilient biasing elements being movable between a baking position and an inoperative position, and one resilient biasing element urging its responsive element towards the operative position, and the other resilient biasing element urging its respective pressure responsive element towards the braking position, wherein the exhaust port of the first valve assembly is connected to the second compartment of the first chamber, the exhaust port of the second valve assembly is connected to the second compartment of the second chamber, and second compartment of the second chamber is connected to the exhaust port of the first valve assemble.