Variable area valve

Claim 1

A FLOW CONTROL VALVE COMPRISING A CASING HAVING AN INLET PORT FOR FLUID UNDER PRESSURE, AND AN OUTLET PORT; AND A SPRING CLOSED VALVE MEMBER MOVABLE IN SAID CASING TO OPEN COMMUNICATION BETWEEN SAID INLET PORT AND SAID OUTLET PORT; SAID VALVE MEMBER HAVING A FIRST AREA EXPOSED TO THE FLUID PRESSURE IN SAID INLET PORT EFFECTIVE TO PROGRESSIVELY OPEN SAID VALVE MEMBER AGAINST SPRING PRESSURE ACTING THEREON AND THEREBY PROVIDE FOR PROGRESSIVE INCREASE IN FLOW FROM SAID OUTLET PORT AS THE PRESSURE ACTING ON SAID FIRST AREA INCREASES; SAID VALVE MEMBER AND CASING INCLUDING MEANS FORMING A RESTRICTED PASSAGE THROUGH WHICH THE FLUID FLOWS FROM SAID INLET PORT TO SAID OUTLET PORT AS SAID VALVE MEMBER IS OPENED; SAID VALVE MEMBER HAVING A SECOND LARGER AREA WHICH IS ACTED UPON BY FLUID UNDER PRESSURE ON THE UPSTREAM SIDE OF SAID RESTRICTED PASSAGE; SAID RESTRICTED PASSAGE BEING PROGRESSIVELY DECREASED IN FLOW AREA BY PROGRESSIVE OPENING MOVEMENT OF SAID VALVE MEMBER AS AFORESAID AND THUS HAVING A PROGRESSIVELY INCREASING PRESSURE DROP OVER AND ABOVE THAT DUE TO THE PROGRESSIVELY INCREASING FLOW OF FLUID THERETHROUGH SUCH THAT FLUID PRESSURE ACTING ON SAID SECOND AREA BUILDS UP TO EFFECTIVELY MOVE SAID VALVE MEMBER AGAINST THE SPRING PRESSURE AT A RATE SUCH THAT, AFTER A SUBSTANTIAL FLOW OF FLUID HAS BEEN ESTABLISHED BY A PROGRESSIVE RISE IN FLUID PRESSURE ACTING ON SAID FIRST AREA, CONTINUED INCREASE IN FLOW OF FLUID IS ACHIEVED DESPITE A DECREASE IN FLUID PRESSURE IN SAID INLET PORT.