Patent GB-397861-A (GB)
Title: Improvements in controlling systems
IPC: G05B11/01
Filed: 1932-01-22
Abstract: 397,861. Potentiometers. TAGLIABUE MANUFACTURING CO., C. J., Park Avenue, Brooklyn, New York, U.S.A. Jan. 22, 1932, No. 2041. Convention date, Feb. 21, 1931. [Class 37.] Electric currents are measured by maintaining a bridge in a state of equilibrium, the potentiometer tapping being varied by an electric motor, the amount of movement being determined by the direction from which a source of radiant energy impinges on a suitable responsive device. As described, a source of light L is reflected by a mirror M through a slot 13 on to a photo-electric cell PC, various parts of the slot being periodically covered to enable control operations to be performed depending on the part of the slot through which the ray passes. The motor 21 drives the cams C1, C2, C3 continuously, the cams C1, C2, which are of identical shape but arranged angularly as shown lifting in turn the shutters S1, S2, to close portions of the opening 13, and at the same time operating contact springs 17, 18. The mirror M is carried by the galvanometer G which is in the circuit of the variable source of current being measured, shown as a thermo couple TC, and a potentiometer wire 9, the connection 8 to which being variable by' the motor 1. The carriage 7 carries a stylus which records the movement of the carriage, and consequently the variations of TC, on a chart rotated by the motor 21. Assuming that the light is passing through the extreme righthand edge of the opening 13 then when cam C2 raises shutter S2 and closes springs 18, as R is energized by PC, circuits are completed to short RL (33, 34, 35, 49) and to energize RR (37, 38, 40, 41, 42, RR, 44, 46). RR locks over 28 and energizes winding 2 of motor 1 to drive the carriage 7 to the right, C2 opens springs 18 and drops S2, and C3 operates 19 without effect (as R is energized), C1 lifts S2 de-energizing R but RR remains locked up and the motor continues to drive 7. When S1 drops R re-energizes so that when C3 again operates it is again ineffective. S2 is then again raised and the above cycle is repeated. The potentiometer tapping gradually alters the position of the light until it passes from the part a, Fig. 3a, of the slot 13 to part b. When in this position R is still energized with S2 up but when S2 falls the projection 25 on S2 (see Fig. 3) blocks the light and R dc-energizes so that when C3 next closes 19 a circuit is completed for RL (46, 44, RL, 49, 19, 32, 42, 28, 37). RL locks up and connects up winding 3 of the motor so that both windings being energized, the motor stops. The relays RR, RL remain locked up until S2 again opens b. If the light is still passing through this portion of the slot 13, R is again energized, RL is shorted down over the circuit traced above, and winding 2 again becomes effective to move the carriage. The carriage is thus moved step by step until light falls on portion c of the slot which is never uncovered. As R is now not operated both windings remain energized and the carriage remains stationary until the current produced by TC varies moving the light to one of the sections a, b, d, e. Movement of the carriage from left to right is controlled by RL, the movement being continuous when the light falls in section e and step by step when in the section d in a manner obvious from the above description.