Patent GB-761978-A (GB)
Title: Improvements in or relating to remote control arrangements
IPC: G05D3/14
Filed: 1953-06-12
Abstract: 761,978. Electric control systems. COLE, Ltd., E. K., and COPPIN K. J. Sept. 13, 1954 [June 12, 1953], No. 16192/53. Class 40 (1). [Also in Group XXIV] The invention relates to a system for positioning a shaft using coarse and fine balanced bridges. The control potentiometer of the coarse bridge (coarse index) is adjustable in steps 0 ... 9, and the fine control potentiometer (fine index) C is continuously adjustable. According to the invention the balancing potentiometer of the " fine " bridge consists of a ring potentiometer RV2 the wiper arm 20 of which is driven by the reversible balancing motor M, and so arranged that, as the wiper arm 20 passes over the position where the high and low potential ends 0-100 of the ring are conterminous, a reversible impulse counter 1W is energized, in a sense depending on the direction of the motor drive, to step the wiper arm of the coarse balancing potentiometer RV1 in the appropriate direction. This stepping of the coarse potentiometer continues until the coarse bridge is balanced, when the fine bridge takes over control at a reduced motor speed and is balanced during the next partial rotation of wiper 20. To avoid backlash errors, the fine wiper 20 always comes to rest at the balance point while travelling in the same direction, say forwards. If it approaches in the oppositite direction it overshoots the balance point and then returns thereto in the appropriate direction. Detailed circuitry. With the coarse and fine indexes set to a desired shaft position, a set button SET is momentarily operated to energize a relay TA. Unbalance of the coarse and fine bridges are detected by polarized relays PA, PB respectively. Depending on the sense of the coarse bridge unbalance a forward or reverse relay FR, RR is energized by PA and TA, locks TA, and drives the balancing motor M in the corrective sense. As the fine potentiometer wiper 20 passes the 0-100 position, it short-circuits a relay TR, which over cam contacts S1 closed by the motor M at this time, energizes a forward or reverse impulse relay 1F, 1R depending on whether the forward or reverse relay FR, RR is operative, temporary locking circuits being provided for the operative relays FR, RR, 1R, 1F over the cam contacts S1 to preclude incorrect operation. When the coarse potentiometer is stepped to the balance position, the operative forward or reverse relay FR, RR is released as cam contacts S open, and TA releases to (a) switch the fine bridge in the control circuit and (b) energize a " reduce speed " relay, RS which in known manner permits the motor to run only at a reduced speed. The forward or reverse relay FR, RR as appropriate is now energized over contacts of the polarized relay PB, TR, TA and the motor runs until fine balance is achieved, the motor being dynamically braked to rest, if travelling in the forward direction. If the wiper arm 20 approaches the balance position in the reverse direction, however, the reverse relay RR does not release at the balance point so that the motor overshoots until the polarized relay PB operates in the opposite direction to release RR and operate FR to reverse the motor until the balance point is reached. Modifications. The unbalance sensing polarized relays PA, PB may be replaced by a single polarized relay adapted to be switched from the coarse to the fine bridge, Fig. 2 (not shown). When the system is used for tuning a transmitter the transmitter equipment may be paralysed until tuning has been effected by a slow-release relay in parallel with the motor M.