GB1463873A - Fluid flow control valve - Google Patents

Abstract

1463873 Valves PHOENIX VALVE MFRS (PTY) Ltd 8 May 1974 [8 May 1973] 20366/74 Heading F2V In a pressure reducing valve for a water supply, water enters through an inlet connection 30, passes through a filter screen 28, past an open non-return ball valve 22 and enters a chamber 38 bounded in part by the wall of a casing 12 and in part by a movable valve element 32 supported by a pair of rolling diaphragms 34, 36 which seal the valve element to the casing. The valve element comprises a main part 42 formed with two diametrically opposed slots 44. The upper end 46 is closed over and the diaphragm 34 is attached to it by a clamping ring 48. A loading spring 76 bears on the upper surface of the end 46. The lower end of the valve element is attached to the diaphragm 36 and has a bore 72, constituting the outlet of the valve, which co-operates with a closure member 68 attached to a cross-member 64 extending across the casing and passing through the slots 44. The diameter of the upper end of the valve element is made smaller than that of the lower end to allow for the area of the bore over which pressure is non-effective in controlling the opening of the valve. The upper end of the casing is closed by a cap 16 which entraps air to act as a cushion for the valve element. Alternatively, the volume of the chamber may be reduced by the introduction of a liquid by means not shown. By appropriate selection of the difference in diameter of the two valve parts subjected to inlet pressure it is possible to influence the backpressure at which the valve closes. By making the differences in area equal to the area of the bore 72 the valve becomes pressure-balanced and closes at a pressure independent of inlet pressure. By suitable choice of the difference in area the closing back-pressure needed can be made to rise or fall with increasing inlet pressure. In an alternative embodiment, Fig. 2 (not shown), the outlet bore is formed in the fixed cross-member and the valve element 32 carries the closure element 68. In a further embodiment, Fig. 3 (not shown), the loading spring operates at the other end of the valve element to bias it to a closed position and inlet pressure is fed to the cap 16 via a manually operated pilot valve (118) to open the valve. When this valve is closed pressure within the cap is allowed to drain away to the outlet via a variable throttle (122) to produce a slow closing of the valve.