Patent GB-417995-A (GB)
Title: Improvements in electric follow up and remote control systems
IPC: G05D3/12
Filed: 1933-01-11
Abstract: 417,995. Valve amplifying circuits. SPERRY GYROSCOPE CO., Inc., Manhattan Bridge Plaza, MOSELEY, F. L., 140, Willow Street, both in Brooklyn, New York, U.S.A., and NISBET, R. H., 24, Penwerris Avenue, Osterley, Middlesex. Jan. 11, 1933, No. 999. [Class 40 (v).] In an electric control system of the type in which a driven member is moved by an electric motor into a position corresponding to that of a controlling member, the motor is controlled by one or more grid glow tubes, the control grids of which are fed with a voltage out of phase with the plate voltage and obtained by combining two out-of-phase voltages at least one of which is variable. The combined voltage may comprise a fixed grid voltage to which the signal voltage is added or both voltages may be derived from the controlling member, the phases altering in opposite directions for a movement of the controlling member. The signal voltage may be amplified before being added to the grid voltage. An oscillating voltage may be supplied to the grids of the valves to keep the motor in oscillation and so overcome backlash and friction and reduce hunting. The suggested uses of the invention include follow-up systems for gyro compasses and the positioning of heavy objects such as search-lights. One form of the invention is indicated in Fig. 1. The transmitter T1 is such that the E.M.F. induced in L3 varies in phase with the direction of movement of the moving member (no E.M.F. being induced when the transmitter is normal) and this voltage es is fed to coupling transformer T2. The transformer T2 has two secondaries L5, L6 which feed grid glow tubes V1, V2 in push-pull. A bias voltage eb, which is 90‹ out of phase with the plate voltage and with the signal voltage es, is fed to the centre point 3 of transformer T2 so that the voltage fed to the valves V1, V2 is the combination of voltages eb and es. As illustrated in Fig. 2A, when the transmitter armature is normal, the voltage es is zero and consequently the currents I1, I2 passed by valves VI, V2 are equal and the fluxes #1, #2 in the motor windings F1, F2 are equal. When the plate is moved to the left as shown in Fig. 2B, equal and opposite voltages esl, es2 are induced in L1, L2 and as these are in phase with the plate voltage ep the grid voltages are eg1, eg2 respectively and currents I1, I2 are passed by the valves to drive the motor clockwise. If the plate is moved to the right, anticlockwise motion of the motor results. Amplifiers may be provided before or after the combination of the signal and bias voltages in positions indicated as 20 and 21 (Fig. 1). Instead of a fixed bias voltage, two out of phase voltages may be provided by the control member by providing a three-phase winding coupled to two coils arranged at right angles, the two sides being provided with suitable reactances and resistances. The motor may be kept in a state of oscillation to prevent backlash &c. and of producing the oscillation such as feed back from the plate of the valves, oscillation of an amplifying valve and a rotatable plate co-operating with a pair of transformer cores are described in the Complete and Provisional Specifications.