GB937423A - Pneumatically actuated relay valve assembly - Google Patents

Abstract

937,423. Fluid-pressure servomotor control systems; fluid regulation. FISHER GOVERNOR CO. Nov. 12, 1959 [Aug. 14, 1959], No. 38432/59. Class 135. In a two-stage pneumatic relay valve comprising a baffle-nozzle pair and a supply-exhaust diaphragm-actuated valve, the nozzle is mounted on the diaphragm. As described, a pneumatic servomotor control system has pressures acting on opposite sides of a piston 54, Fig. 8, which are determined by separate relay valve units 80, 82 actuated by a common beam 92 which is acted on by a bellow 90 which receives an input signal. The input signal reflects the pressure in a conduit controlled by a valve 222, the stem of which is connected to the piston 54. A feedback spring 126 interconnects the pistonrod 30 and the beam 92 which is pivotally supported by flexible strips 102, 104 is loaded by an adjustable spring 116 and carries flappers 110, 114 which co-operate respectively with nozzles 140, 140<SP>1</SP> in series with non-bleed relay valves comprising a diaphragm and piston assembly 136, 156, Fig. 7, which defines a nozzle chamber 148, an exhaust chamber 152 and an outlet chamber 178. The diaphragm and piston assembly control a double valve 170, 172 in accordance with the nozzle back pressure in chamber 148 to determine whether the outlet chamber 178 is connected to exhaust through the chamber 152 or to supply through valve bore 171. The supply pressure to the nozzle chamber passes through a restriction plug 190, the bore of which contains a reciprocable cleaning pin. The pressures in bellows 90 and at the top and bottom of piston 54 are indicated respectively by gauges 202, 182, 184, Fig. 3, which form part of the complete controller unit 12 mounted on top of the cylinder 14.