Minimum pressure delivery valve assembly

Claim 1

A MINIMUM PRESSURE DELIVERY VALVE ASSEMBLY FOR MOTOR COMPRESSOR UNITS HAVING A DISCHARGE CONDUIT LEADING TO SAID VALVE ASSEMBLY AND A DELIVERY CONDUIT LEADING FROM SAID VALVE ASSEMBLY FOR TRANSMISSION OF FLUID PRESSURE THERETHROUGH FROM SAID COMPRESSOR UNIT, COMPRISING IN COMBINATION A VALVE CASING FOR SAID VALVE ASSEMBLY AND INTERCONNECTING SAID DISCHARGE AND DELIVERY CONDUITS, A VALVE OPENING IN SAID CASING COMMUNICATING BETWEEN SAID CASING AND SAID DISCHARGE CONDUIT AND FORMING A VALVE SEAT, A MAIN CHECK VALVE MEMBER SEATABLE ON SAID SEAT FOR CONTROLLING FLOW FROM SAID DISCHARGE CONDUIT TO SAID DELIVERY CONDUIT AND FOR INTERRUPTING FLOW IN THE REVERSE DIRECTION, A FIRST CHAMBER IN SAID VALVE CASING INTERMEDIATE SAID VALVE OPENING AND SAID DELIVERY CONDUIT, AN AUXILIARY VALVE MEMBER SLIDABLE IN SAID FIRST CHAMBER AND HAVING AN OUTER FACE DISPOSED TOWARD SAID DISCHARGE CONDUIT AND AN INNER FACE OPPOSITELY DISPOSED WITH SAID OUTER FACE HAVING A GREATER EFFECTIVE PRESSURE-RESPONSIVE AREA THAN SAID INNER FACE, MEANS FORMING AN ABUTTING PROJECTION BETWEEN SAID AUXILIARY VALVE MEMBER AND SAID MAIN CHECK VALVE MEMBER DEFINING THEREBETWEEN A SECOND CHAMBER WHEN SAID MEMBERS ARE IN ABUTTING RELATION, FIRST SPRING MEANS IN SAID FIRST CHAMBER AND EFFECTIVE UPON SAID AUXILIARY VALVE MEMBER FOR NORMALLY BIASING SAID MEMBER INTO ABUTTING RELATION WITH SAID MAIN CHECK VALVE MEMBER IN THE ABSENCE OF AN OPPOSITELY DIRECTED MINIMUM FLUID PRESSURE EFFECTIVE UPON SAID OUTER FACE OF SAID AUXILIARY VALVE MEMBER, MEANS FORMING FLOW COMMUNICATION FROM SAID DELIVERY CONDUIT INTO SAID SECOND CHAMBER BETWEEN SAID AUXILIARY AND MAIN CHECK VALVE MEMBERS, MEANS FORMING FLOW COMMUNICATION FROM SAID DISCHARGE CONDUIT INTO SAID SECOND CHAMBER THROUGH SAID MAIN CHECK VALVE MEMBER, AND A SECOND SPRING RELATIVELY WEAKER THAN SAID FIRST SPRING AND EFFECTIVE BETWEEN SAID AUXILIARY AND MAIN CHECK VALVE MEMBERS FOR NORMALLY BIASING SAID MAIN CHECK VALVE MEMBER AWAY FROM SAID AUXILIARY VALVE MEMBER AND OUT OF SAID ABUTTING RELATION THEREWITH, SAID FIRST SPRING PROVIDING SUBSTANTIALLY THE ONLY FORCE ACTING ON SAID AUXILIARY VALVE MEMBER IN OPPOSITION TO FLUID PRESSURE IN SAID SECOND CHAMBER AND EFFECTIVE ON SAID OUTER FACE OF SAID AUXILIARY VALVE MEMBER.