Patent GB-1037544-A (GB)
Title: Improvements in safety valves
IPC: G05D16/02
Filed: 1963-06-06
Abstract: 1,037,544. Fluid pressure servomotor systems. V.W. FARRIS. June 6, 1963 [June 11, 1962; April 23, 1963], No. 22598/63. Heading G3P. A pressure relief valve comprises a main valve closure member 29, Fig. 1, carried by a piston 31 and subjected to the pressure at the inlet 25. The valve controls the pressure in a conduit 27 and a diaphragm 43, loaded by a spring 62, forms a chamber 45 connected to the conduit 27 by a pipe 69. The diaphragm 43 is fixed to a member 41 which carries a yoke 46. A lever 48 is mounted on the yoke 46 by a pin 47 and the lever pivots about a pin 50, adjustable in a slot 49 of the lever by movement of a pin carrier 54. A yoke 52 is fixed to the opposite end of the lever 48 and carries a roller 53 which abuts a rod 124, Fig. 6 (not shown) of a spring loaded valve member having valve closures 105, 110. A chamber 103 above the valve member is connected to the conduit 27 through pipes connected to pipe 69, and the space below valve member 110 is connected to exhaust. The chamber 107 between the valve members is connected to a chamber 117, Fig. 5 (not shown) which has a bellows 119 connected to a valve member having closure surfaces 91, 94 which co-operate with seats 92, 93. A chamber 87 on the left of the valve member is connected to the conduit 27 by pipes connected to pipe 69 and the chamber on the right of the valve member is connected to exhaust through port 121. The chamber 90 between the closure surfaces is connected by a pipe 96 to a chamber 38, the pressure in this chamber acting on the piston 31 in a direction to close the main valve 29. In operation when the pressure in the conduit 27 is below a value determined by the spring 62, the valves are in the position shown in which pressure from the conduit 27 is fed to the chamber 38 to hold the main valve closed and the chamber 119 is connected to exhaust. When the pressure in the conduit exceeds the predetermined value, the diaphragm 43 moves upwards against the loading 62 to rotate the lever 48 about the pivot 50. Movement of the lever 48 acts on the rod 124 to open valve 106 and close valve 110 whereby conduit pressure is fed to chamber 117 to act on bellows 119. This causes the valve 91 to close and valve 94 to open thereby connecting the chamber 38 to exhaust. The pressure at the inlet 25 is then able to open the main valve to relieve the excess pressure. When the pressure again falls, the lever 48 is moved to the position shown to allow the valves 106, 110 to connect chamber 117 to exhaust and the subsequent expansion of the bellows moves the valves 91, 94 to supply conduit pressure to chamber 38 thus closing the main valve. In a modification, the valve controlling the supply and exhaust of fluid to the chamber above piston 221, Fig. 18 (not shown), is actuated directly by the diaphragm 227. The diaphragm is connected to a yoke 239 which carries a pin 240 for a lever 241. The lever 241 is rotated by the diaphragm about a fixed pivot 242. A yoke 244 at the opposite end of the lever is selectively connected to a lever 246 at points 249. The lever 246 is pivoted at 247 and is engaged by a roller 250 of a lever 251, which lever is loaded by a spring 255. The spring 255 provides the loading on the diaphragm 227 and a bell-crank lever (not shown) connected to lever 251 actuates the valve controlling the supply and exhaust of conduit fluid to the chamber above the piston 221. The adjustment of pivot 50 Fig. 1, and connection 249 Fig. 18 controls the response of the system to excess pressure and the rate of opening of the main valve.