GB1099745A - Fluid powered servomechanism - Google Patents

Abstract

1,099,745. Fluid-pressure servomotor systems. MOOG Inc. June 15, 1966, No. 26791/66. Heading G3P. In a fluid powered servosystem, Fig. 12, torque motors 242, 248 receive the same electrical signal and, via respective flapper-nozzle units 238, 240, 241 and 249, 250, 251, control a spool valve 255 and a model spool 260, feedback to the flappers being provided by springs 264, 265. A further flapper 268 co-operating with nozzles 269, 270 is hinged at 271, 272 and connected by springs 257, 267 to the spool 255 and the model 260. When the spool and model undergo identical movements, the flapper 268 remains centrally disposed between nozzles 269, 270, but when the spool and model undergo relative movement, e. g. due to clogging of a nozzle or restrictor or failure of an electrical winding, the flapper 268 pivots to generate a monitoring pressure Pm which may act to prevent spool 255 from controlling its servomotor and initiate operation of the latter by means of a duplicate servosystem. In the embodiment of Fig. 3 the two parts 65, 66 of a tandem actuator are respectively controlled by systems 1 and 2, the arrangement being that system 2 is redundant until system 1 fails. Pressure supplies P 1 , P 2 are fed to the systems and solenoids 118, 206 are momentarily energized to allow fluid to flow to conduits 126, 182. Pressure in 126 acts via line 128 to move a spool 85 to the left to uncover a port 94 which is connected via lines 116, 114 to the supply P, so that when solenoid 118 is de-energized the spool 85 is retained in its leftward position where it connects lines 75, 76 of motor 65 with lines 73, 74 leading from a spool valve 12 controlled by torque motor and amplifier unit 10. Pressure in 182 acts via 201 to move a relay valve 202 to the right to uncover a port 200 which is connected via 194 and 192 to supply P 2 so that when solenoid 206 is de-energized the relay valve is retained in its leftward position. Pressure in 126 also acts via 190 on a piston 186 to maintain a spool 175 in its leftward position against pressure exerted on the left hand end of the latter via 182. In this position, spool 175 connects opposite sides of motor 66 so that the latter is not actuated by its torque motor 150, amplifier 151 and spool valve 152. Pressure in 126 and 182 also acts in chambers 222, 223 of a piston locking device 210 to raise the latter to disengage cams 226, 228 from rollers 229, 230 on rod 68 of the tandem actuator. Under these circumstances, system 1 is active to control motor 65, the latter having a positional feedback connection to the torque motors via lever 131, link 135, frame 136 (shown dotted) and spring- centred devices 138, 155. Each system also has a torque motor 142, 156 controlling a monitor fluid amplifier 11, 153 the outputs of which are applied as differential pressures across respective detector spools 96, 162. The spool valves 12, 152 have feedback connections to the flappers of both the amplifiers. If a fault occurs in system 1, spool 96 is moved by the resulting monitor pressure and vents line 116 to allow spring 92 to move spool 85 to the right to connect opposite sides of motor 65. If the monitor pressure disappears, spool 85 still remains in its rightward position since port 94 is now closed. Line 126 is now vented via line 129 and chamber 91 so pressure is lost in chambers 189, 222. The locking device is retained in its upward position by pressure in chamber 223 but spool 175 is now moved to the right to connect lines 165, 166 of motor 66 to lines 163, 164 so that the tandem actuator is now actuated by system 2. If system 2 fails, spool 162 is moved by the monitor pressure to vent line 194 to allow spring 203 to move relay valve 202 to the left to vent line 182 to allow spring 181 to move spool 175 to the left to connect opposite sides of motor 66. Pressure is now lost in chamber 223 so piston 210 is lowered by spring 212 to cause cams 226, 228 to engage rollers 229, 230 to lock the tandem actuator.