GB473242A - Improvements in or relating to electric remote selective control systems - Google Patents

Abstract

473,242. Electric control systems. OSTER, L. E. W. MONTROSE-, and POLLOPAS PATENTS, Ltd. March 22, 1937, No. 8435. [Class 40 (i)] In a selective control system of the type employing a transmitter resistance 1 and a motor controlled receiver resistance 1<1> connected in an automatically balanced bridge circuit, the motor 7 is controlled by differently timed relays 10 .. 15 which function to bring the motor to rest instantaneously in a selected position. Normally, when the bridge is balanced, the relays 13, 14 ; 12, 15 and resistances 25, 22 are connected in parallel and in series with relays 10, 11 and the normal current flow is such that relay 11 only is operated to shortcircuit the motor armature. When the bridge is unbalanced, polarized relay 17 in the bridge wire short-circuits relay 11 and relays 10 and 12, 15 or 13, 14 are operated to close the motor circuit and thereby effect rebalancing of the bridge. When relay 17 restores, relay 11 again pulls up to short-circuit the armature, but relays 12, 15 or 13, 14 remain operated for a predetermined time and cause over-excitation of the field due to the reduction of resistance in the motor circuit and a consequent strong braking effect on the armature.