Versatile change over valve for liquefied gas breathing appts. adapts to conditions of use

摘要

This change over valve, abstracts alternately from vessels, pref. of liquefied gas for breathing appts. A symmetrical change over piston, with both a valve plug and seals on each end, slides in a working chamber, driven by differential pressure, between two end positions, to connect the higher pressure inlet of two, to the outlet. In an innovative design, the piston (7) and/or working chamber (12) allow relocation of at least one seal (8.1, 8.2) in various positions. Hence the effective working area, and the change over differential pressure, are determined by the seal position. Pref. the valve plugs (7.2) of the change over piston (7) have pairs of seals (8.1, 8.2) of differing dia., set with mutual axial clearance, seating on corresponding dia. of the working chamber (12). The valve plug (7.2) diameter varies continuously and may taper down as a truncated cone towards the ends of the piston (7). Finally the plug (7.2) transforms into a cylindrical guide shaft (7.3). The surface of the valve plug (7.2) has locations for the sealing elements (8.1,8.2) at differing axial positions, which may take the form of several concentric ring grooves (9) of which two may accept sealing elements (8.1, 8.2). The mounting of the seated change over piston (7) allows flow past the basic body (7.1) from the appropriate inlet, to the outlet (4) grooved cross channel (10) for flow. O-ring (8.1, 8.2), piston- or flange sealing is used. The material is: Viton (RTM), EPDM.