Double-check quick relief combination valve for air brake systems

Claim 1

IN A DUAL-CHECK RELEASE VALVE UNIT FOR AN AIR BRAKE SYSTEM INCLUDING AN AIR PRESSURE-ENERGIZED SERVICE BRAKE ACTUATOR AND A SPRING-ENERGIZED PARKING BRAKE ACTUATOR NORMALLY MAINTAINED INOPERATIVE IN RESPONSE TO AIR PRESSURE APPLIED THERETO, IN COMBINATION: A CASING INCLUDING MEANS DEFINING A SHUTTLE VALVE CYLINDER HAVING A TRANSFER PORT IN ITS LATERAL WALL INTERMEDIATE ITS ENDS, A CHECK VALVE SEAT AROUND SAID TRANSFER PORT EXTERNALLY OF SAID CYLINDER, A TRANSFER CHAMBER COMMUNICATING WITH SAID SEAT, AN EXHAUST PORT IN THE OUTER END OF SAID TRANSFER CHAMBER, A RELEASE VALVE SEAT AROUND SAID EXHAUST PORT WITHIN SAID TRANSFER CHAMBER IN OPPOSED RELATION TO SAID CHECK VALVE SEAT, A CONNECTING PORT COMMUNICATING WITH SAID TRANSFER CHAMBER, FOR CONNECTION TO SAID PARKING BRAKE ACTUATOR TO SUPPLY AIR PRESSURE THERETO FOR MAINTAINING IT INOPERATIVE, INLET PORTS AT THE RESPECTIVE ENDS OF SAID CYLINDER, FOR CONNECTION TO RESPECTIVE AIR PRESSURE LINES AT LEAST ONE OF WHICH IS AN EMERGENCY AIR PRESSURE LINE, AND SHUTTLE VALVE SEATS AROUND THE RESPECTIVE INLET PORTS WITHIN SAID CYLINDER; A DUAL CHECK RELEASE VALVE CLOSURE UNIT DISPOSED IN SAID TRANSFER CHAMBER AND MOVABLE BETWEEN SAID RELEASE VALVE SEAT AND SAID CHECK VALVE SEAT FOR ALTERNATIVE SEATING ENGAGEMENT THEREWITH; MEANS SPRING LOADING SAID CLOSURE UNIT TO A POSITION SEATED ON SAID CHECK VALVE SEAT TO CHECK FLOW OF AIR FROM THE TRANSFER CHAMBER TO SAID SHUTTLE VALVE CYLINDER, SAID CLOSURE UNIT INCLUDING MEANS ACTING IN RESPONSE TO AIR PRESSURE IN THE TRANSFER PORT, TO ENGAGE SAID RELEASE VALVE SEAT TO CLOSE THE EXHAUST PORT FOR PRESSURIZING THE TRANSFER CHAMBER, AND, WHEN UNSEATED FROM THE RELEASE VALVE SEAT, PROVIDING OPEN COMMUNICATION THROUGH THE TRANSFER CHAMBER BETWEEN THE CONNECTING PORT AND THE EXHAUST PORT FOR DUMPING AIR PRESSURE FROM THE PARKING BRAKE ACTUATOR SO AS TO EFFECT SPRING-ENERGIZED ACTUATION OF THE BRAKE; A SHUTTLE VALVE POPPET SLIDABLE IN SAID CYLINDER BETWEEN POSITIONS SEATED AGAINST THE RESPECTIVE SHUTTLE VALVE SEATS, RESPONSIVE TO PRESSURE IN EITHER OF SAID INLET PORTS TO MOVE TO AN OPEN POSITION WITH RESPECT TO THE RESPECTIVE SHUTTLE VALVE SEAT THEREOF, SO AS TO ADMIT AIR FROM THE PRESSURIZED INLET PORT INTO THE SHUTTLE CYLINDER AND SAID TRANSFER PORT, UNSEATING SAID CHECK VALVE CLOSURE FROM THE CHECK VALVE SEAT, THEREBY ADMITTING AIR INTO THE TRANSFER CHAMBER AND SEATING SAID CHECK VALVE CLOSURE AGAINST THE RELEASE VALVE SEAT SO AS TO CLOSE SAID EXHAUST PORT AND TO DIRECT THE AIR THROUGH THE CONNECTING PORT TO THE RESPECTIVE ACTUATORS FOR RELEASING THE PARKING BRAKES.