Patent GB-896431-A (GB)
Title: Improvements in or relating to a fluid pressure servo motor control system
IPC: F15B9/08
Filed: 1958-10-10
Abstract: 896,431. Fluid-pressure servomotor-control systems. MAICHLE, O. Oct. 10, 1958 [Oct. 11, 1957], No. 32361/58. Class 135. The space between two rigidly interconnected diaphragms 1a, 1b, Fig. 1 is connected to a source of control fluid which, when its pressure increases sufficiently, lifts the diaphragm assembly and an attached valve 8 to cause a sleeve 2 and a valve 3 connected thereto to be displaced so enabling an operating fluid supplied to a chamber 3a from a hollow column 16 to flow into another chamber 10 and through a port 4 and another hollow column 17 to depress the spring-loaded diaphragm of a regulator spindle 6, which, through a spring 7, lowers the diaphragms 1a 1b and valve 8, and allows the sleeve 2 to fall and hence the valve 3 to seat. A decrease in pressure of the control fluid lowers the diaphragms 1a, 1b and valve 8 and so opens the adjacent end of the sleeve 2 whereupon operating fluid from the chamber 5 above the regulator diaphragm escapes via column 17, port 4, chamber 10 and sleeve 2 to a space above diaphragm la; the consequent upward movement of the regulator spindle reducing the tension in the spring 7 and enabling the diaphragms 1a, 1b to rise and cause the valve 8 to abut the sleeve 2, thus preventing further escape of fluid from chamber 5. The chambers 3a and 10 are interconnected by a leak-path, which may be adjustable, to keep the valve 8 spaced from the sleeve 9 and to provide an over-pressure in a transparent regulator cover E which is vented via a non- return valve to prevent the entry of any air therethrough. Pressure gauges C as shown, are connected to the columns 16, 17 and a third hollow column not shown ; the gauges may be cylindrical and used in place of the nuts 16a only two of which are shown. The sleeve 2 may be attached to the diaphragms 1a, 1b and the latter may be dispensed with. The columns upstand from the base of the apparatus. In a modification, any lowering of the pressure of the control fluid in the chamber 23, Fig. 5, between the actuating diaphragms causes the latter and the attached valve 24 to move downwardly to uncover the adjacent end of the sleeve 22, thus allowing fluid to escape from a chamber 26 via apertures 25 in the sleeve 22, the rate of this escape is greater than that at which fluid enters chamber 26 through restricted inlets 27, 32, whereby the pressure beneath a diaphragm attached to a valve 20 unseats the latter and enables the operating fluid to escape at a greater rate from above the regulator diaphragm to the space above the actuating diaphragm until the balance position is attained when the sleeve 22 is closed by the valve 24 and the resulting pressure build-up in chamber 26, due to operating fluid flowing through restriction 31, closes the valve 20. Upon an increase of pressure of the control fluid in chamber 23 the actuating diaphragms lift the valve 24 and hence sleeve 22 and unseats an auxiliary valve 21, so allowing fluid to escape from a chamber 29 faster than the inflow thereto via restriction 30 whereby the pressure acting on a diaphragm attached to a main valve 19 is sufficient to cause the latter to unseat and enabling operating fluid from passage 17 to flow into passage 16 and then to the regulator diaphragm. When the balance position is reached the sleeve 22 is closed off by the valve 24 and the valve 21 seats in the valve 19; pressure then builds up in chamber 29 to seat the valve 19. The gap between the valve 24 and the sleeve 22 is maintained by a flow from passage 17 via restriction 32, chamber 26 and apertures 25. The diaphragms attached to valves 19, 20 may be dispensed with and the valves may be of the piston type. The diaphragms may be replaced by bellows. In another modification, the sleeve 36, Fig. 7, has an enlargement 35 which engages and mechanically opens the main valve 34 upon upward movement of the sleeve 36 in response to large pressure increases of the control fluid; small pressure increases being met by unseating of the auxiliary valve 33. Small decreases of control fluid pressure are catered for by movement of a valve 37 on the diaphragm assembly away from the adjacent end of sleeve 36 whilst large decreases in control pressure result in the valve 37 mechanically opening the main valve through which the sleeve 36 is slidable. This construction may be applied to the Fig. 5 arrangement. The apparatus may be used as a pressure, temperature, quantity or liquid level regulator.