GB1090349A - Improvements in or relating to fluid control valves - Google Patents

Abstract

1,090,349. Fluid-pressure servomotor systems. HOUDAILLE INDUSTRIES Inc. Oct.18, 1965 [Dec.18, 1964], No.44039/65. Heading G3P. [Also in Division F2] Each piston-and-cylinder forming an assembly for operating a press or the single piston-andcylinder employed in an impact device for testing materials is supplied with actuating fluid via a fast-acting valve 19, Fig. 3, having a differential piston 49 with an obturator portion formed by two different diameter parts 66, 71 joined by an inclined shoulder 67 all of which co-operate with complementary seating areas in the bore 40 that houses the piston. The bore 40 has a supply groove 57 a pilot valve port 58 and a vent passage 63 opening thereinto whilst the passage 45 downstream of the obturator communicates directly with the associated piston-and-cylinder device 34, 27 and a vent port 73. With the differential pistons 49 in the position shown a pilot chamber 52 is supplied with pressure fluid from groove 57 by leakage past piston ring 59. Ring 60 on the smaller part of the differential piston provide for less leakage than the ring 59. The differential piston 49 is held in the position shown by pressure in pilot chamber 52 since the passage 45 into which supply fluid leaks via piston parts 66, 67 and 71 is vented through port 73. Upon actuation of a normally-closed pilot-valve 23 the pressure in chamber 52 falls and supply pressure acting on a shoulder 69 adjacent piston part 66 urges the piston 49 leftwards but the groove 57 is not connected to passage 45 until the piston has attained a high velocity in the time which elapses before the part 71 leaves its corresponding bore part whereupon a very high-pressure fluid from a pump or accumulator surges into the passage 45. As the piston 49 moves it progressively throttles the pilot-valve port 58 and the fluid is therefore trapped between the piston and a face 53 and so provides for piston deceleration and cushioning. The differential piston 49 may be returned to the position shown by a further pilot valve controlled piston 96 which may also function as a lock for the piston 49. The piston valve 23 may be solenoid operated and controlled by any means e.g. excessive pressure in the upper end of the piston-and-cylinder or movement limit switches. In a modification Fig. 2 (not shown), the piston, which has a surface 76 subject to the full pressure of the supply fluid, is in telescopic relationship to a stub 78; the pilot chamber 52a communicates with the pilot valve through a number of different size ports 58a whilst the pilot fluid is obtained from the main inlet through an adjustable restriction. The piston is urged by a spring 95 to the closed position shown.