| 摘要 |
533,866. Valves. BRITISH THOMSONHOUSTON CO., Ltd. (General Electric Co.). Dec. 6, 1939, No. 31615. [Class 135] A testing arrangement for a fluid control valve 13, having operating means consisting of a fluid operated servomotor with a piston 17 connected to the valve stem 14, comprises a valve controlled byepass 41, 42, connected to the servomotor on opposite sides of the piston 17, to check the movability of the stem 14, the byepass being automatically rendered ineffective in response to a limited movement of the valve stem. The piston 17 is biassed to the valve closing position by a spring 19 and is moved to the valve opening position by fluid pressure led to the cylinder 18 by pipes 20, 25, including a valve 21. Piston valves 38, 39. on a common stem are normally positioned as shown so that the pipe 42 is blocked and the pipe 41 is open at 36 to the atmosphere. To test the operability of the valve 13 a hand-lever 45 is raised to close the duct 36 and connect the pipes 41, 42. The pressure on opposite sides of the servomotor piston 17 is thus equalized and the latter moves in a direction to close the valve 13. Such valve-closing movement is very limited and ceases as soon as the servomotor piston 17 covers the end of the pipe 42. Upon release of the lever 45 the valve 13 is moved to the fully open position. As shown, the valve 21 embodies a trip latch 27 co-operating with the shaft 30 of a turbine or other part of the mechanism embodying the fluid control valve. Upon excessive speed of the shaft 30 the latch 27 is tripped and the valve 21 moves to exhaust the servomotor cylinder 18, whereupon the valve 13 closes. Means to indicate that the valve 13 is making testing movements consists of contacts 50 electrically associated with a lamp 48. Upon slight testing movements of the valve 13 a projection 51 on the valve stem 14 closes the contacts 50 and the lamp 48 is illuminated.
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