Patent GB-671594-A (GB)
Title: Improvements in or relating to electronic phase shift apparatus
IPC: H03H11/26
Filed: 1950-04-04
Abstract: 671,594. Electric control systems. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. April 4, 1950. [June 15, 1949] No. 8427/50. Class 40 (i). [Also in Group XL (c)] In a pulse delaying circuit an input signal is applied via an amplifier to trigger a first pulse generator which produces a reference pulse having a predetermined phase relationship to the input signal, the reference pulse is then applied via a variable delay stage to trigger a second pulse generator to produce an output pulse which has a pre-determined but variable delay with respect to the reference pulse. The invention may be applied to a rotor balancing equipment for securing an adjustable phase relationship between a sine-wave generator or other cyclically operating component of the equipment and an input signal controlled by the revolution or vibration of the rotor to be balanced. In such a system the signal source 10 shown in the Figure comprises a vibration pick-up, a photoelectric pulse generator or an A.C. tachometer generator and the pulses produced across the cathode load of valve 83 are used to synchronise a sinusoidal voltage generator 90. The input signal from source 10 is applied through an amplifying or phase-inverting stage comprising valve 23 to an amplifying and shaping circuit comprising valves 33 and 43 respectively. The voltage across the load resistor 44 is differentiated by resistor-capacitor network 54, 48 and the positive peaks trigger a single-stroke blocking oscillator stage comprising valve 53 to produce a series of positivegoing output pulses across its cathode load, in coincidence with the first impulsive portion of the input signal from generator 10 ; these reference pulses may be taken from terminal 8. The pulses produced across the cathode load of valve 53 trigger a cathode-coupled flip-flop circuit comprising valves 63, 631 the changeover point of which is adjustable by variation of resistor 65, or capacitors 171-175 to produce after differentiation by network 76, 84 a series of positive going pulses the positions of which relative to that of the reference pulses at terminal 8 may be varied by adjusting the change over point of the flip-flop circuit. These positive going pulses trigger a further blocking- oscillator stage comprising valve 83, to produce a sequence of positive pulses across the cathode load which are applied to the utilization circuit 90. In a modification Fig. 4 (not shown), the blocking oscillator pulse generator stages are replaced by a pulse generating circuit in which a capacitor is charged from the H.T. supply via a resistor and is periodically discharged through a thyratron which is rendered conducting by the positive going trigger pulses. In a further modification, Fig. 6 (not shown), the cathode coupled flip-flop stage has its change-over point adjusted by variation of the grid bias of the normally non-conductive valve. The flip-flop stage may be replaced by a phantastron Miller-integrator circuit, Fig. 5 (not shown), comprising a penta-grid valve which produces an output pulse across its cathode load which has a delay with respect to the positive triggering pulse which is adjusted by variation of the bias on the third grid.