Patent GB-451317-A (GB)
Title: Improvements in apparatus for the automatic operation of plant or machines
IPC: C10J3/24
Filed: 1935-10-05
Abstract: 451,317. Automatic control of plant or machines. POWER-GAS CORPORATION, Ltd., RAMBUSH, N. E., and BALLINGALL, J. M., Parkfield Works, Stocktonon-Tees. Oct. 5, 1935, No. 27514. [Class 135] [See also Group XII] In a servomotor control system for automatically controlling the operation of plant or machines and particularly adapted for controlling the operation of the various valves of a water-gas plant, the several main valves are operated against loading means by single acting pistons under the control of relay valves actuated, against a fluid-pressure load commonly applied, by fluid pressure selectively applied through control valves operated by cyclically moved selector elements. The various loading means are arranged so that when emergency conditions arise the operation of emergency controls permit these means to move the main valves into the safe or standby condition. The timing dial 21 which carries a series of tappets 62 is continuously rotated by an electric motor 20 acting through electrically released spring-applied brake 73, reduction gearing 25, gear wheel 26, worm gears 261, 221 and change speed wheels 22, 23. The gear wheel 26 also drives a wheel mounted on a shaft 24 adapted to be clutched to a shaft 27 arranged to act through bevel-and-worm gearing to rotate a cam shaft 29. The clutch mechanism which is described in Specification 282,505, [Class 135], is operated when a tappet 63 on arm 64 is moved by one of the tappets on the timing dial and is so designed that when the shafts are coupled together the shaft 27 makes one revolution and is then declutched. To ensure clearance between the clutch elements the shaft 27, after declutching, is given a further slight angular movement by a weighted lever carrying a roller engaging a cam on the shaft 27. Mounted on the shaft 29 are five cams corresponding to the stack valve, secondary air valve, primary air valve, change over valve or valves and steam valve of a water gas plant and which operate through levers on control valves 38-42. The control valves, (Fig. 20), each comprise a spindle 90 working in a packing and formed with an axial passage communicating with two sets of radial ports arranged so that the pipe 81 may be connected either to a pipe 43 leading to a pressure manifold 44 or to an exhaust passage 98. The fluid pressure admitted through the pipe 43 normally holds the valve in its lower position with the pipe 81 connected to exhaust. The several pipes 81 are coupled to the actuating chambers of relay valves 48-52. These valves (Fig. 21) each comprise a spindle 100 having an enlarged part 102 with an axial passage connecting two sets of radial ports adapted to connect a passage 105, leading to a main valve actuator, either to a pressure supply conduit 86 or to an exhaust conduit 88. These valves are urged towards their lower position by fluid pressure from a manifold 54 admitted through conduits 53 to act on shoulders 103. The conduits 86 may be fitted with throttles so as to vary the speed of operation of the several main valve actuators. The conduit 45 supplying the pressure manifold 44 is adapted to be connected to the main pressure supply conduit 80 or to exhaust 287 by a three-way emergency valve 46. The pipe 55 supplying the pressure manifold 54 is connected to the main supply conduit 80 or to exhaust 288 by a three-way relief valve 56, so that loading pressure may be removed to facilitate hand operation of the relay valves. This hand actuation is effected by means of hand levers carrying toothed quadrants engaging racks 115 pinned to the relay valve spindles. The toothed quadrants are arranged on two parallel spindles and are provided with suitably shaped bosses arranged so that pairs of valves may bo interlocked. The emergency valve is moved to the pressure position by a hand operated pinion 130 engaging a toothed sector 129 on a shaft carrying an arm 126 coupled by a link to the valve spindle. As the arm 126 reaches its uppermost position it closes a contact 134 which completes the circuit through a coil operating a contactor 136 to establish the circuit through a holding magnet 121, which maintains the emergency valve in its pressure position against the action of a loading weight 122. The relief valve is manually actuated by a handle on a shaft carrying an arm 137 linked to the relief valve spindle. In its raised position this arm closes a switch 141 in the circuit of an electrically actuated audible alarm. The valves 46, 56 are mechanically interlocked by a lug 144 on the lever 126 and a bent arm 120 secured to the arm 137, so that the valve 46 must be put to exhaust before the valve 56 and the valve 56 restored to pressure before the valve 46. In order to stop the control apparatus when any irregularity occurs each main valve is provided with a pair of limit switches 190, 191 (Fig. 23), arranged in series with a reversing switch 200, driven synchronously with the cam shaft, in the control circuit of the driving motor 20 and holding magnet 121, so that when any change has been initiated and the required movement is not completed within a certain time interval the control circuit is broken. To start the apparatus the relief and emergency valves are brought into their pressure positions. The start button 213 is now pressed to complete a circuit through switch 134, stop press button 214 reversing switch 200, limit switch 190 or 191, overload switch 215 to energize a coil 135. This closes the contactor 136 in the holding magnet circuit and a switch 210 completing a circuit through a coil 225. The energization of this coil closes the motor contactor to start the motor and closes a switch 212 in parallel with the start button, which can now be released. To maintain the control circuit while a valve is passing from one position to another the reversing and limit valve circuit is shunted by temporary time switch 216. This switch is closed by a coil controlled by a switch 218 operated by an arm 219 on the clutch control lever 64 each time the clutch is operated and is automatically opened after an interval by clockwork. In order that the motor may continue to run after an emergency operation until it reaches the stand by positioning the switch 210 is shunted bv a limit switch 226 actuated by a cam on the timing dial. An indicating disc 76 (Fig. 3), is geared to the cam shaft and a series of indicating lamps 195 controlled by switches 197 operated with the limit switches 190, 191 give visible indication of the state of the plant.