Shut-off valve for metered flows

Claim 1

A SHUT-OFF VALVE DEVICES FOR METERED FLOW LINES HAVING POSITIONS OF FULL-OPEN, CLOSED AND AN INTERMEDIATE POSITION OF REGISTRABLE LOW FLOW, SAID VALVE COMPRISING: A VALVE HOUSING HAVING A FLUID PASSAGE THERETHROUGH, A MAIN VALVE ELEMENT DISPOSED IN SAID HOUSING AND MOVABLE BETWEEN A CLOSED POSITION AND A FULL-OPEN POSITION, SAID VALVE ELEMENT BEING CLOSED BY MOVEMENT IN A DIRECTION OPPOSED TO NORMAL FLUID FLOW THROUGH SAID PASSAGE, MEANS DEFINING FIRST AND SECOND FLUID PASSAGEWAYS, SAID FIRST PASSAGEWAY FLUIDLY COMMUNICATING WITH SAID HOUSING PASSAGE ON THE UPSTREAM SIDE OF SAID VALVE ELEMENT FOR APPLYING A CLOSING FORCE TO SAID MAIN VALVE ELEMENT, SAID SECOND FLUID PASSAGEWAY COMMUNICATING WITH SAID HOUSING PASSAGE ON THE DOWNSTREAM SIDE OF SAID MAIN VALVE ELEMENT FOR RELIEVING SAID CLOSING FORCE, MEANS APPLYING A CLOSING BIAS FORCE TO SAID MAIN VALVE ELEMENT, MEANS INCLUDING A CONTROL VALVE SELECTIVELY OPERABLE FOR ALLOWING FLUID TO PASS EITHER THROUGH SAID FIRST PASSAGEWAY OR SAID SECOND PASSAGEWAY, AND MEANS ASSOCIATED WITH MOVEMENT OF SAID CONTROL VALVE FOR SECURING SAID MAIN VALVE ELEMENT AT A FIXED, PREDETERMINED POSITION INTERMEDIATE FULL-OPEN AND CLOSED.