Patent GB-730081-A (GB)
Title: Improvements in or relating to fluid-pressure operated devices
Inventor: OLAH GEORGE
IPC: G01L13/04
Filed: 1949-03-14
Abstract: 730,081. Fluid-pressure servomotor-control systems; valves. PRECISION DEVELOPMENTS CO., Ltd. March 13, 1950 [March 14, 1949], No. 6948/49. Class 135. A device for varying the pressure of a fluid as a function of the value of a variable force comprises a duct 1, Fig. 1, supplied with fluid, e.g. compressed air, at a predetermined pressure, a chamber 3 supplied by the duct through a constriction 2, an opening 4 from the chamber to a space, e.g. the atmosphere, containing fluid at a pressure different from that in the chamber, said opening being controlled by a ball valve 6 urged from a conical seating 5, of from 20 degrees to 40 degrees included angle, solely under the action of the higher of the two pressures and urged towards the seat by the variable force applied to an abutment 7, the pressure in the chamber 3 being connected by a pipe 9 to a pressureactuated device or gauge. In an arrangement for measuring flow, the force is applied to the ball 13, Fig. 2, by a lever 10 connected to bells 21, 22 subject to the pressures on opposite sides of a valve 29 in a conduit 27. Where the force may be applied in either direction, two ball valves 46, 47, Fig. 4, are acted on by a lever 49 to which the force 51 is applied, the respective chambers 37, 43 being supplied by conduits 35, 40 through constrictions 36, 42. When the lever moves, one ball is urged towards its seat and the other away from its seat and a pressure difference is obtained in pipes 52, 53 which is proportional to and of the same sign as the force and is applied, e.g. to a mercury manometer 54. Apparatus for producing a pressure or a pressure difference proportional to the dis. placement of a member comprises a float 59, Fig. 5, sensing level'in a manometer 60 measuring flow and carrying a rack 62 engaging a pinion 63 which is connected to a magnet 66 rotatable in a sealed chamber. A block 80 on a shaft 78 outside the chamber rotates with the magnet and a cam 90 of square root law form raises or lowers a roller 88 on an arm 87 fixed to a shaft 86. Also on the shaft 86 is an arm 91, Fig. 6, carrying a spring 94 and. a balance weight 103, the positions of which may be varied by screws 98, 102, respectively. The other end of the spring engages a lever 96 pivoted at 105 and carrying at opposite ends an air dashpot 111 and a balance weight 110. Intermediate the ends there are abutments 113, 114 for ball valves 127, 128 coacting with seals on blocks 121, 122 respectively. Compressed air is supplied by a conduit 132, through a restriction 115 and, as shown, a single variable pressure is taken to a utilizing device by a pipe 133. To obtain a pressure difference the block 121 is rotated through 180‹, the restriction 115 is replaced by two restrictions in bore 116, and a connection is made to opening 119. Apparatus for converting an electrical signal into a proportional pressure or pressure difference comprises a rod 155, Fig. 9, carrying a wound former 150 axially movable in the air gap of a pot-type magnet 143, the rod being supported by insulated spring arms 157, 152. The ends of the rod are provided with abutments 173, 180 for ball valves 172, 178 respectively, compressed air being supplied to a conduit 187 containing restrictions 190, 199 and the pressure difference due to a signal carried to the wound former being taken off by pipes 182, 183. The signal may be derived from a displaceable member moving a contact along a slide wire and the pressure difference may be applied to a manometer. High amplification of an input signal may be obtained, e.g. by applying the pressure difference obtained from an electrical signal device 222, Fig. 15, of the kind described with reference to Fig. 9, to bells 223, 224 connected to a lever 225. Abutments 227, 228 at opposite ends of the lever engage ball valves 229, 230 respectively, which provide variable pressures in chambers 233, 234 supplied with compressed air by a conduit 237 through restrictions 235, 236 and the pressure difference is applied by pipes 238, 239 to a manometer 240. Apparatus for producing a pressure proportional to a force which is applied as a variable fluid pressure comprises a housing 249, Fig. 21, containing a member 271 having knife-edges 273, 274 supporting a beam 276, Fig. 19, stabilized by air-dashports 275 and on which acts a ball 305 subjected to the variable pressure. The beam applies the resulting force to a ball valve 315 and the proportional pressure is taken at outlet 318. The arm between the pivotal axis of the beam and the ball valve is variable by turning the member 271 relatively to the housing 249.