Double check valve

Claim 1

A DOUBLE CHECK VALVE DEVICE OF THE REVERSE TYPE IN WHICH THE LOWER OF TWO SUPPLY FLUID PRESSURES IS SELECTIVELY CONNECTED TO A DELIVERY LINE, SAID VALVE DEVICE COMPRISING: (A) A VALVE BODY HAVING A THROUGH BORE THEREIN, (B) END CAPS SEALINGLY SECURED TO SAID BODY TO CLOSE THE ENDS OF SAID THROUGH BORE, EACH END CAP HAVING A SUPPLY CHAMBER THEREIN COMMUNICATING WITH THE CORRESPONDING END OF SAID BORE AND TO WHICH FLUID PRESSURE FROM DIFFERENT SOURCES BY BE RESPECTIVELY SUPPLIED, (C) TWO SPOOL VALVE ELEMENTS SLIDABLY OPERABLE IN SEALED TANDEM RELATION IN SAID BORE AND SUBJECT AT THE OUTER END THEREOF TO THE FLUID PRESSURE IN A CORRESPONDING ONE OF SAID SUPPLY CHAMBERS, EACH OF SAID VALVE ELEMENTS HAVING A PLURALITY OF SEALINGLY SEPARATED ANNULAR GROOVES IN THE OUTER SURFACE THEREOF, (D) SPRING MEANS INTERPOSED IN A CHAMBER INTERVENING BETWEEN THE ADJACENT INNER ENDS OF SAID SPOOL VALVE ELEMENTS AND BIASING SAID VALVE ELEMENTS RESPECTIVELY IN OPPOSITE DIRECTIONS TO NORMAL POSITIONS, (E) SEPARATE SUPPLY PASSAGEWAYS IN EACH OF SAID END CAPS EXTENDING INTO SAID BODY, EACH RESPECTIVELY CONNECTING A CORRESPONDING ONE OF SAID SUPPLY CHAMBERS TO THE SAID THROUGH BORE ADJACENT THE END OF SAID THROUGH BORE OPPOSITE TO SAID ONE OF SAID SUPPLY CHAMBERS, (F) AN EXHAUST PASSAGEWAY IN SAID BODY OPENING TO SAID BORE VIA WHICH SAID CHAMBER INTERVENING BETWEEN SAID SPOOL VALVES IS CONSTANTLY CONNECTED TO ATMOSPHERE, AND (G) A DELIVERY PASSAGEWAY IN SAID BODY OPENING TO SAID THROUGH BORE VIA WHICH FLUID UNDER PRESSURE MAY BE SUPPLIED TO A RECEIVING DEVICE, (H) THAT ONE OF THE SAID SPOOL VALVE ELEMENTS SUBJECT TO THE HIGHER FLUID PRESSURE BEING SHIFTABLE AGAINST THE FORCE OF SAID SPRING MEANS INTO AN OPERATING POSITION IN CONTACT WITH THE OTHER OF SAID SPOOL VALVE ELEMENTS WHICH IS THEREBY HELD IN ITS NORMAL POSITION, SAID ONE OF SPOOL VALVE ELEMENTS IN ITS OPERATING POSITION CUTTING OFF THE COMMUNICATION BETWEEN SAID DELIVERY PASSAGEWAY AND SAID EXHAUST PASSAGEWAY AND ESTABLISHING COMMUNICATION BETWEEN THE SUPPLY PASSAGEWAY FROM THE SUPPLY CHAMBER HAVING THE LOWER FLUID PRESSURE THEREIN AND THE SAID DELIVERY PASSAGEWAY.