Patent GB-472693-A (GB)
Title: Improvements in elastic fluid turbines
IPC: F01D17/26
Filed: 1936-03-31
Abstract: 472,693. Fluid-pressure servomotorcontrol systems. GUY, H. L., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. March 31, 1936, No. 9549. [Class 135] [Also in Group XXVI] Relates to a means for preventing acceleration or racing of steam turbines after the governor valves have been closed, arising from steam leaking past these valves, by varying the steam pressure before them. The pressure before the governor valves is controlled by a valve A in series with them, the opening of valve A being governed by the turbine governor. The valve member 7 is controlled by a relay B consisting of a spring-loaded piston 14 and a cylinder space 18 in communication with a trip pilot valve C through duct 24 and ports 25. The oil supply 58 for operating relay B is under the control of the valve C and the pilot valve F. Valve C is controlled by the operation of emergency devices D and E whilst valve F is controlled by the turbine governor and a spring- loaded tappet 21. If when the main governor valves are closed the turbine tends to race, sleeve 75 moves upwards and acting through levers causes piston 53 to move upwards putting the line 31 in communication with drain 60 so releasing the pressure in space 18 and the valve 7 closes. The bridge piece 11 moving downwards with the valve forces rod 23 and tappet 21 downwards against spring 22. This causes the link 71 to rotate bell-crank 65 about its pivot and move piston 53 downwards to cover ports 55a and stop oil supply to drain 60, and valve A remains stationary. The reverse takes place if the turbine tends to slow up, line 31 being put in communication with supply 58. Speeder gear illustrated by a spring- loaded lever 82 acting on the governor sleeve 75 is used to bring the machine up to speed, the spring 84 acting in conjunction with the spring 79 allows the position of the sleeve 75 and consequently the position of valve 53 to be adjusted, so that at any given speed the valve 53a can cover ports .55a and prevent movement of valve A. The valve A can be operated by hand wheel 47 rigidly attached to which is sleeve 48a which acts on the threaded rod 51 to move rod 37 which in turn moves valve C through lever 33. Pilot valve 26 places the duct 24 in communication with the oil exhaust line 29 or feed line 31 to operate the valve. As the valve moves the lever 33 attached to bridge 11 operates the valve 26 to prevent further movement. Sleeves 48, 48a, rod 51, piston 36 and rod 37 are normally held down against the action of spring 39 by means of splines on sleeve 48 engaging internal splines on the washer 49 which is located in partition wall 38b. When the emergency trip valve is operated the pressure in cylinder 43 is released, piston 42 moves downwards and turns washer 49 through linkwork 40, 41 thus releasing sleeves 48, 48a, rod 51, &c. This causes the end of lever 33 to rise, lift valve 26 and release pressure in relay cylinder 18 causing valve A to close. Although the closing of valve A acting through link 71 causes the piston 53 to allow oil under pressure to pass into line 31, the head 26a of valve 26 blocks port 30 to prevent opening movement of piston 14.