Tractor trailer brake system

Claim 1

IN A TRACTOR TRAILER BRAKE SYSTEM, MANUALLY OPERABLE CONTROL VALVE MEANS FOR SUPPLYING FLUID PRESSURE TO THE ACTUATORS FOR THE TRACTORS BRAKES, A SERVICE LINE HAVINGA FORWARD END CONNECTED TO BE SUPPLIED WITH PRESSURE FROM SAID CONTROL VALVE MEANS UPON OPERATION THEREOF, SAID SERVICE LINE HAVING A REAR END ON THE TRAILER, MEANS CONNECTED TO THE REAR END OF SAID SERVICE LINE TO BE OPERATED BY PRESSURE THEREIN TO OPERATE THE TRAILER BRAKE ACTUATORS IN PROPORTION TO THE DEGREE OF SUCH PRESSURE, AND AN AUTOMATIC VALVE MECHANISM CONNECTED IN SAID SERVICE LINE BETWEEN THE ENDS THEREOF, SAID AUTOMATIC VALVE MECHANISM COMPRISING A BODY HAVING A PRESSURE CHAMBER CONNECTED TO A SOURCE A PRESSURE, SAID VALVE MECHANISM HAVING A DUCT THERETHROUGH NORMALLY AFFORDING COMMUNICATION BETWEEN SAID ENDS OF SAID SERVICE LINE, A NORMALLY CLOSED VALVE DISCONNECTING SAID PRESSURE CHAMBER FROM SAID DUCT, A NORMALLY OPEN VALVE IN SAID DUCT CONNECTED TO SAID NORMALLY CLOSED VALVE, A VALVE SEAT MOVABLE IN ONE DIRECTION TO ENGAGE SAID NORMALLY OPEN VALVE TO CLOSE SAID DUCT AND TO TRANSMIT MOVEMENT FROM SUCH VALVE TO SAID NORMALLY CLOSED VALVE TO OPEN IT AND SUPPLY PRESSURE FROM SAID PRESSURE CHAMBER TO THE REAR END OF SAID SERVICE LINE, AND A SOLENOID HAVING AN ARMATURE MECHANICALLY CONNECTED TO SAID VALVE SEAT WHEREBY SAID SOLENOID IS ENERGIZABLE TO MOVE SAID VALVE SEAT TO CLOSE SAID NORMALLY OPEN VALVE AND OPEN SAID NORMALLY CLOSED VALVE TO CUT OFF COMMUNICATION THROUGH SAID DUCT AND ADMIT PRESSURE TO THE REAR END OF SAID SERVICE LINE, SAID SOLENOID HAVING A CIRCUIT INCLUDING A SWITCH ARRANGED TO BE CLOSED UPON INITIAL OPERATION OF SAID CONTROL VALVE MEANS.