GB489516A - Improvements in and relating to means for automatically controlling registration in printing and other operations on a continuous strip of material - Google Patents

Abstract

489,516. Valve relay circuits. BRITISH THOMSON-HOUSTON CO., Ltd. March 1, 1937, No. 6072. Convention date, Feb. 27, 1936. [Class 40 (v)] [Also in Group XXXV] In the control of a reversible motor with separate fields on the anode circuits of valves 31, 32 the grids of these valves are energized by A.C. at a predetermined phase angle, but a variable D.C. component is supplied from a normally balanced resistance bridge 42, 43. The resistance 42 is in the output circuit of valves 36, 37 containing an ionizable medium and connected across a resistance 49 forming part of a potentiometer 49, 50 supplied with D.C. A second potentiometer across the same D.C. terminals comprises resistances 46, 47, 48, and the grids of triodes 36, 37 are connected through resistances 60, 61 respectively to a point 46a thereon. The output of amplifiers 55, 57 and 56, 58 passes through the resistances 60, 61 respectively. The second stage valves 57, 58 are grid biassed so as normally to supply current to the resistances 60, 61 and so hold the valves 36, 37 nonconducting. Each time a photo-cell 26, 28 is activated the resulting change in output of the associated amplifier reduces the grid voltage of the valve 57 or 58 so that the valves 36, 37 carry current. When these activations are not simultaneous one of the valves 36, 37 conducts first and unbalances the bridge 42, 43 so that the corresponding winding of the motor 24 is energized through the corresponding valve 31 or 32. Commutation of the valves 36, 37 is obtained by valves 62, 63, the first being rendered conducting by the charge built up in condenser 66 whereupon the transformer 69 causes the valve 63 to send current through resistance 50 sufficient to raise the cathode potentials of valves 36, 37 above that of their anodes ; at the same time anode 63b discharges condenser 66 to reset the system.