Patent ID: 7344204

Claim:
A safety device for a trailer, the device having: a valve, the valve having a casing rotatably mounting a valve spool therein, the casing having an air inlet, an air outlet, a vent outlet, and an alarm outlet, separate from the air and vent outlets, therein; the valve spool having a single passageway therethrough; the air inlet connectable to a first brake line section from a compressor; the air outlet connectable to a second brake line section leading to brakes on the trailer; the vent outlet leading to the atmosphere; the alarm outlet connectable to an alarm line leading to an alarm on the trailer; the valve spool rotatable within the casing to any one of: a drive position where the valve connects the air inlet to the air outlet via the passageway to unlock the brakes and blocks the vent and alarm outlets; a locked position where the valve connects the air outlet to the vent outlet via the passageway to vent the brakes and leave the brakes locked and blocks the air inlet and alarm outlet; and an alarm position where the valve connects the air inlet to the alarm outlet via the passageway to sound the alarm when an attempt is made to move the trailer with a truck cab and blocks the vent and air outlets.