Valve for controlling flow of fluid

摘要

938,375. Fluid-pressure servomotor control systems. CAMERON IRON WORKS Inc. Dec. 15, 1959 [Sept. 4, 1959], No. 42645/59. Class 135. In a fluid-pressure control system pilot valve 48 is biased in one direction and held by pressure in a normal position so that main valve 26 connects inlet 10 to outlet 11 when the pressure e.g. at the outlet is intermediate a first and second predetermined pressure, and the pilot valve is moved from its normal position by the first or second pressure to close valve 26 when either of these pressures is obtained. Inlet pressure passes through main valve 26 and its actuating piston 28 via filter 31, and passages 44, 43, through a passage 38a, manual reset valve 87 and passage 38 to the normally closed pilot valve 48. Should the first or second pressure via passages 52, 48a, 46 act on end 47 of valve 48, the valve moves upwards against spring 72 through abutments 73-76 or downwards under the action of spring 69 to connect inlet pressure port 54 to either of ports 55, 57 so that inlet pressure via passages 39, 39a and valve 87 acts above piston 28 to close the main valve. As piston 28 moves off sealed spigot 41, so inlet pressure acts directly on the piston to close the main valve quickly. Lever 89 is moved downwards to shift valve 87 to the right from its " automatic " position as shown for manually opening the main valve by venting pressure above piston 28 through passage 103. The main valve may be manually closed by moving lever 89 upwards to shift valve 87 leftwards whereby inlet pressure at 38 passes via passages 104, 105 in valve 87 to passage 39a and the piston 28. In an alternative embodiment passage 39 is extended upwards to a further pilot valve port whereby, when valve 87 is in its " automatic " position and the main valve has closed, return of the conduit pressure to normal allows the pilot valve to return to its normal position and pressure above piston 28 is then exhausted via the extension of passage 39, passages 60, 70 through the pilot valve and passages 48a, 52 to the main valve outlet. In an alternative embodiment (Fig. 7, not shown) the pilot valve is formed by two telescoping pistons, each of which is moved under spring load when the other abuts a stop, and the valve 87 has only two loads and two positions for automatic operation, and re-opening the main valve. In a further embodiment, the main closure is a gate valve in a uniform through bore without restrictions 18, 19, as in Fig. 2, for producing a pressure drop.