Patent ID: 6923509

Claim:
An apparatus for locking and unlocking a brake actuator of a dual chamber brake system that operates brakes with compressed air, wherein the dual chamber includes the brake actuator in a first pressurizable chamber that serves as a service housing chamber and a high spring-rate spring in a second pressurizable chamber that serves as an emergency housing chamber, the brake actuator being movable in an axial direction to apply and release the brakes of the brake system; in the absence of compressed air the high spring-rate spring expanding to bias and keep the brake actuator in an axially forward position locking the brakes of the brake system, and wherein when there is compressed air in the second chamber the high spring-rate spring is compressed and allows retraction of the brake actuator from its forward position to unlock the brakes, the apparatus comprising: electro mechanical means responsive to a first coded signal for venting pressurized air from the second chamber and for preventing entry of pressurized air into the second chamber whereby expansion of the high spring rate spring causes the brake actuator to move into the axially forward position locking the brakes of the brake system, the electromechanical means being mounted in one of the pressurizable service housing chamber and the pressurizable emergency housing chamber the electro mechanical means also being responsive to a second coded signal for allowing pressurized air to enter into the second chamber and for disallowing the venting of pressurized air from the second chamber thereby unlocking the brake actuator and unlocking the brakes, the second chamber further including an inlet port, said inlet port allowing attachment of a hose through which pressurized air is normally supplied to the second chamber, and the electro mechanical means further including a solenoid valve mounted in the second chamber to shut-off the supply of pressurized air through the inlet port in response to the first coded signal, and allow the supply of pressurized air through the inlet port in response to the second coded signal.