Abstract: A valve member including a flexible diaphragm movable into and out of engagement with a valve seat to close and open the valve, respectively. A rigid support plate rests against the face of the diaphragm opposite the face which engages the valve seat. A stem projects from the plate, through a hole in the diaphragm and into the orifice surrounded by the valve seat. The diaphragm and plate are not rigidly secured together, so that the entire diaphragm is free to flex with respect to the support plate. A pilot passageway may extend completely through the plate and stem. The stem is long enough such that the lower end of the pilot passageway is below the plane of the valve seat even when the valve is open. An abutment, such as an outwardly projecting bead, on the lower end of the stem prevents accidental separation of the plate and diaphragm before they are assembled with a valve.

Abstract: A valve having a valve body formed with an internal orifice between the valve inlet and outlet ports, and a main valve member for opening and closing the orifice. A chamber above the valve member is supplied with high pressure fluid through a bleed passageway extending between the chamber and the inlet port. A pilot valve controls exhausting of the chamber when the main valve is to be opened. A flow control element in the bleed passageway maintains a constant rate of fluid flow for filling the chamber, to close the main valve, regardless of the pressure differential across the flow control element. The bleed passageway may be in either the valve body or the main valve member. The flow control element may be an annular rubber washer.