Navistar International Transportation Corporation

Robert L Douglas

Brad A Hively

Michael J Lehman

Terry E Hively

Roy S Zeitlow

Richard B Davis

A parking brake lock-in key switch system for a truck or bus brake system. The system has two parking brake lock-in valves. One parking brake lock-in valve is installed in the air line piping between the primary air tank and the push pull double check valve and the second parking brake lock-in valve is in the air line piping between the secondary air tank and the push pull double check valve. The parking brake lock-in valves are air operated valves which when closed will look in actuated parking brakes. The parking brake lock-in valves are operated by a solenoid operated pilot valve which provides air from an air supply to close the lock-in valves when the ignition key is moved to the 'off' position. An actuated parking brake will be locked in because new air from the respective tanks will be prevented from flowing to the push pull double check valve and hence the brake chambers. The parking brake lock-in valve does not vent off downstream piping when it closes. Should the ignition key be positioned to the 'off' position with the vehicle in motion and the parking brake actuator is not engaged in the park position, air will be locked in the air line piping between the parking brake lock-in valves and the individual brake chambers including the piping in which the push pull double check valve is installed. This locked in air will prevent the brake chambers from locking the wheels, hence preventing inadvertent engagement of the parking brakes. One embodiment of the invention for vehicles with automatic transmissions will include an automatic apply-automatic release parking brake system which operates alone or in parallel with the parking brake lock-in key switch system. The automatic apply-automatic release parking brake system has a valve that acts to operate and engage the parking brake when the automatic transmission is placed in the &ldquo;Park&rdquo; position. The valve of the automatic apply-automatic release parking brake system in this embodiment will deactivate and release the parking brake when the transmission shifter is moved out of the &ldquo;Park&rdquo; position and the engine of the vehicle is running.

Parking brake lock-in key switch system for vehicle air brake system

A parking brake lock-in key switch system for a truck or bus brake system is disclosed. The system has two parking brake lock-in valves. One parking brake lock-in valve is installed in the air line piping between the primary air tank and the push pull double check valve and the second parking brake lock-in valve is in the air line piping between the secondary air tank and the push pull double check valve. The parking brake lock-in valves are air operated valves which when closed will lock in actuated parking brakes. The parking brake lock-in valves are operated by a solenoid operated pilot valve which provides air from an air supply to close the lock-in valves when the ignition key is moved to the `off` position. An actuated parking brake will be locked in because new air from the respective tanks will be prevented from flowing to the push pull double check valve and hence the brake chambers. The parking brake lock-in valve does not vent off downstream piping when it closes. Should the ignition key be positioned to the `off` position with the vehicle in motion and the parking brake actuator is not engaged in the park position, air will be locked in the air line piping between the parking brake lock-in valves and the individual brake chambers including the piping in which the push pull double check valve is installed. This locked in air will prevent the brake chambers from locking the wheels, hence preventing inadvertent engagement of the parking brakes.

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Fort Wayne, IN, United States of America

Robert L Douglas