Fluid operated braking system

Claim 1

IN A VEHICLE BRAKING SYSTEM OF THE TYPE EMPLOYING SEPARATE BRAKING ASSEMBLIES FOR EACH OF A PLURALITY OF WHEELS, EACH ADAPTED TO BE ACTIVATED TO BRAKING POSITION BY A PNEUMATICALLY OPERATED BOOSTER ASSEMBLY AND TO BE ENERGIZED WITH PRESSURIZED AIR UNDER THE CONTROL OF THE VEHICLE DRIVER; THAT IMPROVEMENT WHICH COMPRISES MECHANICALLY POWERED ALTERNATE BRAKE SETTING MEANS EFFECTIVE TO SET THE VEHICLE BRAKES UPON FAILURE OF SAID PRESURIZED AIR, SAID MECHANICALLY POWERED BRAKE SETTING MEANS INCLUDING MEANS FOR HOLDING SAID BRAKE SETTING MEANS DEACTIVATED NORMALLY BY USE OF PRESSURIZED AIR, MANUALLY CONTROLLED VALVE MEANS READILY ACCESSIBLE TO THE VEHICLE DRIVER FROM HIS NORMAL DRIVING POSITION TO VENT PRESSURIZED AIR FROM SAID MECHANICALLY POWERED BRAKE SETTING MEANS THEREBY ACTIVATING THE LATTER TO SET AND HOLD THE BRAKES POSITIVELY SET UNTIL PRESSURIZED AIR IS AGAIN ADMITTED TO SAID MECHANICALLY POWERED BRAKE SETTING MEANS, AND PRESSURE DIFFERENTIAL RESPONSIVE CHECK VALVE MEANS IN THE PRESSURIZED FLUID SUPPLY TO SAID MEANS FOR HOLDING THE BRAKE SETTING MEANS DEACTIVATED, SAID PRESSURE DIFFERENTIAL RESPONSIVE CHECK VALVE BEING POSITIONED DOWNSTREAM FROM SAID MANUALLY CONTROLLED VALVE WHEREBY THE OPENING OF SAID CHECK VALVE TO VENT AIR TO THE ATMOSPHERE CAUSES AN ABRUPT PRESSURE DROP ON THE DOWNSTREAM SIDE OF SAID MANUAL VALVE, SAID CHECK VALVE MEANS INCLUDING MEANS OPERABLE TO PASS PRESSURIZED AIR TO SAID HOLDING MEANS AND TO HOLD SUCH AIR CAPTIVE AGAINST REVERSE FLOW UNTIL THE SYSTEM PRESSURE FALLS BELOW A PREDETERMINED MINIMUM OPERATING PRESSURE WHEREUPON SAID CAPTIVE AIR IS AUTOMATICALLY VENTED TO THE ATMOSPHERE THEREBY ALLOWING SAID MECHANICALLY POWERED BRAKE SETTING MEANS TO SET THE VEHICLE BRAKES, AND PRESSURE RESPONSIVE MEANS OPERATIVELY CONNECTED WITH SAID MANUAL VALVE OPERABLE BY SAID ABRUPT PRESSURE DROP TO CLOSE SAID MANUAL VALVE TO PREVENT AIR LOSS FROM THE BRAKING SYSTEM AS A WHOLE.