Balanced valve

Claim 1

A BALANCED FLUID FLOW CONTROL VALVE COMPRISING: AN OUTLET HOUSING HAVING AN OPEN LOWER END AND AN OUTLET PORT; AN INLET HOUSING HAVING AN OPEN UPPER END AND AN INLET PORT; SAID INLET HOUSING BEING DISPOSED IN VERTICAL ALIGNMENT ON THE OUTLET HOUSING; AN INTEGRAL WALL ON THE UPPER END OF THE OUTLET HOUSING BETWEEN SAID INLET AND OUTLET HOUSINGS HAVING A FLOW PASSAGE OPENING FORMED THERETHROUGH WITH A VALVE SEAT FORMED THEREAROUND IN SAID INLET HOUSING; A STEM MOVABLY MOUNTED IN SAID HOUSINGS AND HAVING THE LOWER END THEREOF EXTENDED THROUGH SAID OPENING INTO SAID OUTLET HOUSING AND OUT OF SAID OPEN LOWER END; A VALVE ON SAID STEM IN SAID INLET HOUSING NORMALLY SEATED ON SAID VALVE SEAT FOR CLOSING SAID OPENING AND BLOCKING THE FLOW OF FLUID THERETHROUGH; SAID STEM EXTENDING UPWARDLY FROM SAID VALVE AND THROUGH THE OPEN UPPER END OF THE INLET HOUSING; AN UPPER END CAP MOUNTED ON THE UPPER END OF SAID INLET HOUSING FOR ENCLOSING THE OPEN UPPER END; A LOWER END CAP MOUNTED ON THE LOWER END OF THE OUTLET HOUSING FOR ENCLOSING THE LOWER OPEN END OF THE SAME; CLAMPING MEANS FOR SECURING SAID END CAPS ON SAID HOUSINGS; SPRING MEANS IN SAID UPPER END CAP AND ENGAGED WITH THE UPPER END OF SAID STEM FOR BIASING THE SAME DOWNWARDLY TO MOVE SAID VALVE INTO CLOSING ENGAGEMENT WITH SAID VALVE SEAT; A FIRST ROLLING DIAPHRAGM HAVING THE PERIPHERY SEALINGLY SECURED TO THE UPPER END OF SAID INLET HOUSING AND A CENTRAL PORTION SEALINGLY SECURED TO THE VALVE STEM; A SECOND ROLLING DIAPHRAGM HAVING THE PERIPHERY THEREOF SEALINGLY SECURED TO THE LOWER END OF SAID OUTLET HOUSING AND A CENTRAL PORTION SEALINGLY SECURED TO THE VALVE STEM; THE EFFECTIVE OPERATING AREAS OF SAID ROLLING DIAPHRAGMS AND SAID VALVE BEING SUBSTANTIALLY EQUAL; AND, MEANS FOR MOVING SAID STEM AND VALVE UPWARDLY AGAINST THE ACTION OF SAID SPRING MEANS FOR OPENING THE VALVE TO PERMIT FLUID FLOW FROM SAID INLET HOUSING INTO SAID OUTLET HOUSING FOR DISCHARGE THROUGH SAID OUTLET PORT.