Patent GB-683696-A (GB)
Title: Improvements in or relating to regulating mechanisms
IPC: G05D16/18
Filed: 1949-09-01
Abstract: 683,696. Fluid-pressure servomotor-control systems. BAILEY METERS & CONTROLS, Ltd. Sept. 1, 1949 [Sept. 2, 1948], No. 22675/49. Class 135. A regulator comprises a pivoted beam 4, Fig.1, tiltable by a bellows 32, subject to a loading pressure via a union 35 and a pipe 34, against a spring 11 to actuate a pilot valve 7 for a servomotor which, through a lever 28, Fig. 2, gears 26, 27 and a cam 20, moves a bell-crank 15 thereby changing the tension of the spring and bringing the beam back to its neutral position. The pilot valve 7, Fig. 7, comprises a body with a fluid inlet-port 57, outlets 55, 56 to the servomotor and exhaust ports 55<SP>1</SP>, 56<SP>1</SP>. The ports 55, 56, 57 connect respectively through filters with ducts 72, 81, 94, Fig. 6, the first two of which are interconnected by a duct 102, joined by a pipe 105 to the union 35. Plug cocks 76, 91 operable by knobs 88, 97 respectively, are inserted in passages 81, 94. In one arrangement, the regulator 1, Fig. 8, is applied to a system for controlling a boiler flue damper 117, and the loading pressure is supplied through a conduit 133 to the union 35 by a relay 134, of the kind described in Specification 461,389, operated by a valve 136 connected to a Bourdon tube 135 subject to the pressure in a steam duct 135<SP>1</SP>. The damper is moved by a piston and cylinder 116 through a beam 122 and a link 128, a link 126 connecting the beam and the lever 28. Opposite sides of the cylinder may be interconnected by turning the cock 76, and the damper may be positioned manually by a lever connected to the pivot of the beam 122, the fluid supply being cut off by cock 91. The damper is locked in the adjusted position by two plates 156, Fig. 13, urged towards each other by a spring 162 to grip a rod 124 passing through the plates and connected to the beam 122. The lock is released by a cam 164 turned through gears 166, 167. An alternative form of lock comprises a slotted bar connected to the beam and engaged by a screwed clamp. Stops limit the movement of the piston. In another arrangement, the regulator is applied to a system for controlling a valve 176, Fig. 9, supplying fluid to a tank 175, and the loading pressure is supplied by a relay 182 operated by a valve 181 connected to a Bourdon tube 180 subject to a pressure proportional to the temperature in the tank. The valve 176 is operated through stem 185, connected by a link to the lever 28, by a diaphragm motor 186 controlled by either of the lands 60, 61 of the pilot valve 7. In yet another arrangement, the cam 20, Fig. 20, is connected to a lever 200 operable either manually, or automatically by a variable, to pivot the beam through the spring, thus moving the pilot valve 7 which controls by its lower land 61 the pressure in the bellows 32 and in a pipe 199 connected to a servomotor, e.g. the diaphragm motor 186. In a further arrangement, the passages of the pilot valve are blanked off and the loading pressure supplied by the relay actuates the diaphragm. The shape of the cam 20 may be varied to provide any desired relationship between the amount of cam rotation for a particular change of loading pressure throughout the range of pressures and this range is variable by moving the spring along the notched arm 14 of the bell-crank.