Patent GB-571147-A (GB)
Title: Improvements in and relating to means for the automatic control of electromagnetic vibrating apparatus
IPC: H02K33/00
Filed: 1943-03-22
Abstract: 571,147. Automatic control systems for electrically - vibrated mechanism. TRAYLOR VIBRATOR CO. March 22, 1943, No. 4668. Convention date, March 6, 1942. [Class 38 (iv)] The amplitude of vibration of a vibrating apparatus is maintained constant by supplying the operating power through a power tube having a control grid supplied with an alternating voltage lagging on the anode voltage and superposing on the grid a D.C. voltage proportional to an alternating control voltage varying in value according to the'amplitude of vibration. The amplitude of movement of a vibratory motor 10 such as that described in Specification 545,252, or mechanism driven thereby, is maintained at a selected value by using an adjustable magnetic pick-up device, e.g. of the kind above described, to generate a control alternating voltage which is applied to a potentiometer 57, whereby a selected proportion of the voltage is applied through a transformer and rectifier to a resistance 76 in the grid control circuit of a pentode 28. The control voltage is also applied to determine vibration frequency, through a phase advancing network 68 compensating time lag in the grid circuit of a pentode 29. The pentodes have a common output circuit including a resistance 66 in the grid circuit of full wave rectifiers 15, 16. The grid circuits of the rectifiers 15, 16 are energized from transformers 60 with alternating voltage 90 degrees lagging on their anode voltage, the grid circuits of the valves 28, 29 include direct current voltages determined by taps on a potentiometer 34, 35 and the arrangement is such that each alternate half-cycle of control voltage produces in resistance 66 a potential drop proportional to the amplitude of that voltage and the other half-cycles each produce a drop sufficient in all cases to render the rectifiers 15, 16 non- conducting. The motor-driven mechanism thus receives from these rectifiers impulses of current corresponding to half-cycles of the control voltage, which impulses are controlled by the valve 28 to maintain a constant amplitude of vibration at whatever part of the mechanism the pick-up 53 is installed and of a frequency controlled through the valve 29 and determined by the natural frequency of the vibrating system. The effect of the resistance 76 is swamped during starting by a relay 84 which places a fixed potential, determined by a discharge tube 49 and adjustable by contact 85, in the grid circuit of pentode 28 ; failure of this discharge tube or of the circuit of the potentiometer 34, 35 supplying the grid and anode circuits of valves 28, 29 releases a relay 42 causing interruption of the holding circuit of the main switch 13 which is controlled by push-buttons 51, 52 and a relay 44. The relay 44 is energized after a time delay when switch 24 is closed to start the system and locks itself in through the contacts of relay 42. The time delay is due to a double rectifier 43, the second part of which has its cathode heated by the anode current of the first part and excites the relay 44.