Brake control for disconnected trailers

Claim 1

IN A TRAILER BRAKE SYSTEM HAVING AN EMERGENCY RELAY VALVE NORMALLY CONNECTED THROUGH AN EMERGENCY LINE TO A SOURCE OF PRESSURE ON A TRACTOR TO SUPPLY AIR UNDER PRESSURE TO AN AIR RESERVOIR ON THE TRAILER AND BEING RESPONSIVE WHEN SAID EMERGENCY LINE IS DISCONNECTED FROM SAID TRACTOR TO ACTUATE SAID EMERGENCY RELAY VALVE TO APPLY BRAKES ON SAID TRAILER, THE COMBINATION OF A VALVE BODY HAVING FIRST, SECOND AND THIRD PORTS CONNECTED TO SAID EMERGENCY RELAY VALVE, SAID EMERGENCY LINE AND SAID TRAILER RESERVOIR, RESPECTIVELY, AN ACTUATOR DISPOSED IN SAID BODY MEMBER AND BEING MOVABLE TO CONTROL THE FLOW OF AIR THROUGH SAID PORTS, SAID ACTUATOR HAVING ONE POSITION IN WHICH SAID FIRST AND SECOND PORTS ARE CONNECTED TOGETHER TO PERMIT AIR FLOW FROM SAID TRACTOR TO SAID RESERVOIR WHEN SAID TRACTOR IS CONNECTED TO SAID TRAILER AND TO ACTUATE SAID EMERGENCY RELAY VALVE TO APPLY THE TRAILER BRAKES WHEN SAID TRAILER IS DISCONNECTED FROM THE TRACTOR, SAID ACTUATOR HAVING A SECOND POSITION IN WHICH SAID FIRST AND THIRD PORTS ARE CONNECTED TOGETHER TO ADMIT AIR FROM SAID TRAILER RESERVOIR TO SAID EMERGENCY RELAY VALVE TO ACTUATE THE LATTER FOR RELEASING THE TRAILER BRAKES WHEN THE TRAILER IS DISCONNECTED FROM THE TRACTOR, SPRING MEANS OPERATIVE TO CONTINUOUSLY URGE SAID ACTUATOR TO SAID ONE POSITION, MEANS FOR MANUALLY MOVING SAID ACTUATOR BETWEEN SAID FIRST AND SECOND POSITIONS, AND SEAL MEANS ASSOCIATED WITH SAID ACTUATOR AND OPERATIVE IN RESPONSE TO A SUPPLY OF AIR UNDER PRESSURE FROM SAID TRAILER RESERVOIR TO MAINTAIN SAID ACTUATOR IN SAID SECOND POSITION AGAINST THE RESISTANCE OF SAID SPRING, SAID SEAL MEANS BEING RESPONSIVE TO A SUPPLY OF AIR UNDER PRESSURE FROM SAID EMERGENCY LINE WHEN SAID TRAILER IS CONNECTED TO SAID TRACTOR TO OVERCOME THE PRESSURE OF THE AIR FROM SAID TRAILER RESERVOIR TO PERMIT SAID SPRING TO BIAS SAID ACTUATOR TO SAID FIRST POSITION.