The diaphragm is formed of a compressible elastomeric composition. The end closure or end cap portion of the diaphragm enveloping the stem foot and swivel component is adapted to seat in fluid sealing engagement in the valve seat when the valve stem is moved to a closed position.Needle & Gauge Valves The diaphragm is expanded at its opposite end to provide a sealing ring secured to the valve housing.

Connecting, and integral with, the foregoing end cap and sealing ring portions of the diaphragm is a constricted neck portion which fits loosely about the annular neck of the valve stem sloping outwardly at its opposite ends to form the end cap and sealing ring.MUD VALVES The diaphragm neck is axially resilient, flexible and compressible and the inner diameter of the diaphragm sealing ring is such that when the valve stem bearing the swivel component and diaphragm cap about its foot are moved to a valve open position the annular diaphragm neck collapses and is drawn up into the sealing ring and the end cap is positively lifted from the valve seat, without breaking the mechanical seal effected by the sealing ring with the surrounding valve housing and a stop ring of rigid construction, normally a metal or engineering plastic, positioned about the valve stem and retained in a fixed position within the valve assembly. Balance ValvesThe stop ring has an inner diameter less than that of the flange formed about the inner length of the valve stem to limit the axial movement of the valve stem and to prevent it from exerting undue compressive force on the diaphragm and its end cap into, and when in, contact with the valve seat; that is, a squeeze effect not in excess of about 45 percent of the thickness of said end closure means when it is compressed.

The valve diaphragm and swivel bearing adapt to, and compensate for, the presence of any irregularity in the surface of the seat or valve and provide for independent rotation of the valve stem with concomitant stationary disposition of the valve in the valve seat when the two are in contact in the closed position of the valve assembly.

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