Patent GB-806909-A (GB)
Title: Improvements in or relating to fluid-flow governors
Inventor: JEAVONS MALCOLM WILLIAM
IPC: G05D7/01
Filed: 1954-02-09
Abstract: 806,909. Fluid-pressure servomotor control systems; valves. JEAVONS & CO. Ltd., E. E. March 16, 1955 [Feb. 9, 1954; June 17, 1954], Nos. 3750/54 and 17784/54. Class 135. Fluid flow in a line 1, Fig. 1, is controlled by a valve 2 which is governed through a servosystem by the pressure difference across either of two orifices 5 or 6 which are inserted in the line on the two sides of the valve 2, and means is provided to isolate the servo-system from the orifice which is not appropriate to the required direction of flow. The motive fluid for actuating the servo-system is drawn from the line itself and is caused to flow through a pressure regulating valve 16, a needle valve 25, and a control valve 19, all in series, and back to the line on the opposite side of the main valve 2. The controlling pressure difference across the orifice 5 or 6 is applied to a diaphragm actuating valve 19. Valves 11, 12, 33 and 34 are selector valves which choose the appropriate orifice and take off and return points for the direction of flow. Valve 16 is loaded by spring or dead weight plus the pressure downstream of the main valve, this latter pressure being applied through the line 23. Valve 19 is also loaded by a spring or dead weight and is biased to the open position. The two pressures appearing across the orifice 25 due to the flow therethrough are applied differentially to the diaphragm 3 controlling the valve 2. Stop valves 45 are inserted in the various lines which lead from or to the main line 1. Diaphragm 3 may be replaced by a piston and cylinder or by a liquid-seal bell. The pressures across the orifice 5 or 6 in use are measured on a differential pressure gauge 47 which is calibrated as a rate of volume flow meter, and they are also applied to an integrating recorder 48 which gives the total flow. The presssure of the fluid upstream of the valve 16 is measured on a pressure gauge 50 and recorded in a pressure recorder 51. In operation, assuming the flow to the line 1 is in the direction of the single-headed arrow, valves 33, 34 are actuated so that the pressures across the orifice 5 are applied to the diaphragm of valve 19 and valves 11, 12 are actuated so that pressure fluid is drawn from the point 8 and passed through the valves 16, 25, 19 and back to the line at the point 7. A change in the flow rate will cause the pressure differential across the orifice 5 to vary, and as the valve 16 maintains a predetermined total pressure drop between the upstream side of the orifice 25 and the discharge point 7, the variation in pressure drop across the valve 19 will affect the pressure drop across the orifice 25. This latter variation is applied to the diaphragm 3 to adjust the valve 2 in order to regulate the flow through the line 1. Valves 11, 12, 33 and 34 are ganged in pairs and actuated simultaneously. Their spindles 56, Fig. 2, are interconnected by links 54, 55, 59, and link 55 engages a nut 62 which can travel up and down a screw 63 so that, when the screw is rotated by means of a hand wheel 65, all the valves will be actuated simultaneously.