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. T he system has two parking brake lock-in valves. One parking brake lock-in valve is install ed 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 t he 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 n ew 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 pipin g 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 th e 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.