Vehicle anti-theft system combination

Claim 1

An anti-theft combination for vehicles having an air-brake system including pressure supply lines wherein the brakes of the parked vehicle are applied with spring force to prevent movement of the vehicle, comprising, at least one double compartment brake cylinder having a first compartment for applying the brakes with air pressure for control while driving and a second compartment having a spring for automatically applying the brakes with spring force in the absence of air pressure for holding the vehicle when parked; said second compartment having a diaphragm compressing said spring to a neutral position when air pressure is present in the brake system; a normally closed check valve in the air lines leading from pressure supply to said brake cylinder for blocking air pressure supply when parked; a normally open relief valve in said brake system down stream from said check valve for venting air pressure in the brake system when parked; a solenoid on each said valve for moving each said valve to its non-normal position when said solenoids are energized; wires leading to said solenoids for electrically energizing said solenoids; a normally open relay in said wires normally interrupting EMF supply to said solenoids; said relay being self-holding-in when closed and energized and opening automatically upon deenergizing; a key operated lock mechanism for closing said relay, and a key for operating said lock mechanism; the anti-theft system having a driving condition upon connection of air pressure to the air lines and EMF to the wires established by the driver using said key to close said relay whereupon said solenoids are energized and said check valves are open allowing introduction of air pressure into the brake system and said relief valve is closed holding air pressure in the brake system with said diaphragm compressing said spring to a neutral position; the anti-theft system having a non-driving condition upon the disconnection of EMF to said relay whereupon it opens the stays open de-energizing said solenoids thereby allowing said check valve to close preventing the introduction of air pressure to said diaphragm to Release the brakes by compressing said spring to a neutral position, and allowing said relief valve to open to vent air pressure in the brake system including said diaphragm whereupon the spring force of said spring in said air cylinder sets the brakes preventing movement of the vehicle.