Valve

Claim 1

A VALVE COMPRISING (A) A HOUSING CONTAINING A BORE INTERSECTED BY THREE SPACED CHAMBERS, THERE BEING A SUPPLY CHAMBER, AN EXHAUST CHAMBER AND AN INTERMEDIATE MOTOR CHAMBER; (B) A VALVE MEMBER MOVALBE IN THE BORE AND CONTAINING AN INTERNAL PASSAGE INTERSECTED BY FIRST AND SECOND SPACED THROUGH PORTS; (C) THE VALVE MEMBER HAVING A FIRST POSITION IN WHICH THE SECOND THROUGH PORT REGISTERS WITH THE MOTOR CHAMBER, A SECOND POSITION IN WHICH THE FIRST, AND SECOND THROUGH PORTS REGISTER, RESPECTIVELY, WITH THE SUPPLY AND MOTOR CHAMBERS, AND A THIRD POSITION IN WHICH THE FIRSAT AND SECOND THROUGH PORTS REGISTER RESPECTIVELY WITH THE MOTOR AND EXHAUST CHAMBERS; (D) A CHECK VALVE SEAT ENCIRCLING THE INTERNAL PASSAGE AND LOCATED BETWEEN THE FIRST AND SECOND THROUGH PORTS; (E) A CHECK VALVE HEAD RECIPROCABLE IN THE INTERNAL PASSAGE BETWEEN OPEN AND CLOSED POSITIONS WISTH RESPECT TO SAID SEAT FOR CONTROLLING FLOW FROM THE FIRST TO THE SECOND THROUGH PORT; (F) REACTION SURFACES ON THE CHECK VALVE HEAD SUBJECT TO THE PRESSURE IN THE SECOND THROUGH PORT FOR DEVELOPING FORCES THAT URGE THE HEAD IN BOTH THE OPENING AND THE CLOSING DIRECTIONS, THE AREAS OF THE REACTION SURFACES BEING SO PROPORTIONED THAT THE FORCE URGING THE HEAD IN THE OPENING DIRECTION DOES NOT EXCEED THE FORCE URGING THE HEAD IN THE CLOSING DIRECTION; (G) MENS DEFINING A VENT CHAMBER WITHIN THE VALVE MEMBER WHICH COMMUNICATES WITH THE EXHAUST CHAMBER AT LEAST WHEN THE VALVE MEMBER IS IN THE FIRST POSITION; (H) A RELIEF PASSAGE CONNECTING THE VENT CHAMBER WITH THE SECOND THROUGH PORT, SAID RELIEF PASSAGE CONSTITUTING THE SOLE FLUID CONNECTION BETWEEN THE VENT CHAMBER AND THE SECOND THROUGH PORT; AND (I) A RELIEF VALVE NORMALLY PREVENTING FLOW FROM THE SECOND PORT TO THE VENT CHAMBER THROUGH THE RELIEF PASSAGE BUT BEING RESPONSIVE TO THE DIFFERENTIAL BETWEEN THE PRESSURES IN THE SECOND PORT AND THE VENT CHAMBER FOR OPENING THE RELIEF PASSAGE WHEN THE DIFFERENTIAL REACHES A PREDETERMINED VALUE.