Patent GB-580172-A (GB)
Title: Improvements in electrical "follow-up" devices
IPC: G05D3/14
Filed: 1942-05-13
Abstract: 580,172. Electrical control systems. GENERAL ELECTRIC CO., Ltd., and JACOBY, H. C. E. May 13, 1942, No. 6511. [Class 40 (i)] In an electrical follow-up system comprising coarse and fine balanceable networks each having master and slave potentiometer resistances, out-of-balance currents operate relays connected between movable tappings on master and slave potentiometers and cause an electric motor to drive the slave to follow up the master and balance the network, _the coarse network. being balanced before the fine. Fig. 1 shows a system for controlling an, aeroplane engine throttle comprising a transmitter having coarse and fine potentiometers 1M, 3M and a receiver having coarse and fine potentiometers 1S, 3S. The contacts 4M, 5M and 12M are rotated by the pilot and contacts 4S, 5S and 12S by motor 9. The potentiometers are arranged so that contact. 12 traverses the whole of commutator 10 while contacts 4 and 5 move from one contact to the next, there being one contact 12 for each segment of commutator 6, as shown, Fig. 2. When contact 4 is in a gap between two segments, contact 12 occupies an off position and another contact 15 bridges two contacts 16, 17 in order to energize relay 18. If, for example, the master potentiometer is moved to the position shown while the contact 5S engages segment (a) of commutator 6S, both relays J.8M and 18S are energized and change over normally open contacts 18MN01, 18SNO1 and normally closed contacts 18MNC1, 18SNC1. An out-of-balance current flowing from contact (a) of 6S through contacts 5S, 18SNO1, coils 27, 26, contacts 18MNO1, 5M to segment (e) of commutator 6M, causes coarse polarized relay 27 to open its contacts 27NC, so that it is impossible for fine polarized relay 28 to affect motor 9, and close contacts 27SM to energize the forward field winding 20 and armature 19 of motor 9. Since the difference between the positions of master and slave is great, the current in speed relay coil 26 is sufficient to open contacts 26NC so that motor 9 drives contacts 4S, 5S, 12S at a high speed.. As the difference in position lessens, the speed relay drops out and the motor drives at a slower speeds so -as to present overshooting. An. 'out-of-balance current flowing from master to slave. causes contacts 27MS to close, energizing the backward winding 21. so that the motor drives the slave contacts in the opposite direction. If the master is moved so that contact 12M engages a segment of commutator 10M, contact 4M moving on to a segment of commutator 6M at the same time, the coil 18M will be de-energized and current flows through contacts 18MNC1 and 4M. Motor 9 drives contacts 4S, 5S, 12S until contact 5S engages the segment corresponding to the one engaged by contact 4M, when relay 27 falls out. Since . contact 12S is in its off position coil 18S is energized and contacts 18SN02 closed. Current flows through contacts 18SN02, coil 28 of the fine polarized relay, contacts 18MNC2, 12M to commutator 10M, so. that contacts 28SM close to energize the motor and drive contacts 12S at slow speed to a position of correspondence. When contact 12S leaves the off position, relay 18S falls out and current passes through contacts. 12S, 18SNC2 through. coil 28. The motor is coupled to the throttle and slave contacts by a clutch, clutch trip coil 23 being connected across the supply. Spring means are arranged to move the throttle to a predetermined position if the supply fails and solenoid 23 is de-energized.