Device for regulating a flow of gas

Claim 1

IN A FLUID FLOW REGULATING DEVICE, IN COMBINATION, A SUBSTANTIALLY CYLINDRICAL PLUG OF ELASTICALLY DEFORMABLE MATERIAL AND HAVING OPPOSITE ANNULAR END FACES, A PAIR OF CENTRAL AXIAL EXTENSIONS PROJECTING RESPECTIVELY IN OPPOSITE DIRECTIONS FROM SAID END FACES AND A PERIPHERAL FACE EXTENDING BETWEEN SAID END FACES, SAID PLUG BEING FORMED WITH AN AXIAL BORE THERETHROUGH FOR PASSAGE OF A FLUID THROUGH SAID PLUG; WALL MEANS HAVING AN INNER PERIPHERAL SURFACE ABUTTING AGAINST SAID PERIPHERAL FACE OF SAID PLUG OVER THE WHOLE LENGTH THEREOF FOR PREVENTING RADIAL OUTWARD EXPANSION OF SAID PLUG; AND VARIABLE PRESSURE MEANS ENGAGING SAID OPPOSITE ANNULAR END FACES WHILE LEAVING SAID CENTRAL EXTENSIONS FREE AND UNENGAGED FOR COMPRESSING SAID PLUG ONLY ALONG OUTER ANNULAR PORTIONS THEREOF TO A VARIABLE DEGREE TO REDUCE THEREBY THE INNER DIAMETER OF SAID BORE AND TO CAUSE EXPANSION OF SAID UNENGAGED CENTRAL EXTENSIONS OF THE PLUG IN AXIAL DIRECTION SO AS TO REGULATE FLOW OF FLUID THROUGH SAID BORE SO AS TO PERMIT A VERY GRADUAL AND SUBSTANTIALLY UNIFORM CONTRACTION OF SAID BORE DURING APPLICATION OF PRESSURE AGAINST THE OUTER ANNULAR SURFACE PORTIONS OF SAID END FACES OF SAID PLUG.