Patent GB-545252-A (GB)
Title: Improvements in and relating to control systems for controlling the operation of vibrating electromagnetic motors
IPC: H02P27/04
Filed: 1940-09-04
Abstract: 545,252. Jigging conveyer. TRAYLOR VIBRATOR CO. Sept. 4, 1940, No. 13871. Convention date, Oct. 2, 1939. [Class 78 (i)] [Also in Group XXXV] A reciprocating motor is controlled as to the frequency amplitude of its vibrations by thermionic valves which are influenced by a device operable by the motor vibration and producing a control voltage varying with the motor vibrations and applied to the valves operating the motor. The invention is described in connection with a vibrating conveyer, Fig. 1, of known type with a pick-up coil 27 on a permanent magnet 26 for induction of the control voltage by an armature 31 mounted on the conveyer tray 19. The tray is carried on an extension 13 of the armature 14, the whole moving system being supported on springs 12 and vibrated by currents in the coil 17 'of a magnet 16 which is fixed in the stationary frame 15. A rubber cushion 24 on a bracket 22 supports the tray carrier 13. In this form the natural frequency of the motor directly determines the frequency of the control voltage but the armature 31 may be vibrated independent of the motor, or the frequencycontrolled channel, referred to hereafter, may be energized from a separate source. Fig. 2 shows one thermionic control system, 27 and 17, .respectively, being the pick-up and motoroperating coils 32 the alternating supply and 38, 39 the power operating valves preferably of negative bias type, supplied through a centretapped transformer 35. The frequency and magnitude of the, pulsating current in the coils 17 are controlled by controlling the grid potentials and phase in the valves 38, 39. The filaments of the various valves are heated from the correspondingly lettered windings x, y, z, of the transformers A3, A4. Two potentiometers 47, 45 across the pick-up 27 supply the frequency and amplitude channels shown in the upper and lower rows of valves, but the potentiometer 47 may be omitted. The frequency channel comprises amplifiers A1, A2, a split-secondary transformer 54 and a double rectifier R1 with a resistor 56 (and an optional balancing resistor 55) from which half-cycle D.C. proportional to the pick-up current passes to the phaseshifting control rectifier C.R. The amplitude channel comprises amplifiers A3, A4, transformer 65, full-wave rectifier R2 and resistor 67 leading to an amplifier A5. The input of this amplifier includes three voltages, viz. (i) the D.C. voltage of resistor 67 which is proportional to that in the pick-up and may be controlled by the potentiometer tap 46 (ii) a negative voltage of about 30 volts from a battery and (iii) a small A.C. voltage of about 3 volts from the transformer 44. The amplifier output goes through a transformer 72 to a full wave rectifier R3 tuned on the input side approximately to the mains frequency at 32 and having an output resistor 61. Finally, there is a two-part phase-shifting transformer T, the primaries 76, 81 of one part of which are connected in the plate circuits of the valves 58, 59 through the split secondary of a transformer 74 across the mains while the secondaries 91, 92 are connected to the grids of the power valves 38, 39. The primary 85 of the other part is across a reactor 83, which, with a series resistor 84, is across the secondary at 74, while the secondaries are so connected that their voltages lag behind those of the valve plates by 150 to 160 degrees. The effect is to maintain the frequency of the operating pulses from the valves 38, 39 constantly at a value which is determined by the motor itself and is independent of the supply frequency at 32, while the magnitude of the pulses is controllable. The Specification also describes (Figs. 4, 5 and 7, not shown) a control system for operation on 3-phase mains through six power valves in the limbs of a 6-phase transformer bank. The control includes a balanced push-pull compressor type of amplifier, with 5-grid valves which automatically stabilizes the amplitude of the motor vibration to a preset value. To make this system of control selfstarting a hand-operated buzzer is connected across apart of the pick-up coil to give the initial impulse. In another form of control (Fig. 6, not shown), particularly suitable for use with a 6-phase bank of power valves, two potentiometers are connected in parallel with the pickup coil, one controlling an amplitude channel and the other a frequency channel in which a relaxation oscillator is included.