GB586136A - Electrical synchronisation of rotary shafts - Google Patents

Abstract

586,136. Electric synchronous movements. STANDARD TELEPHONES & CABLES, Ltd. (International Standard Electric Corporation). Dec. 21, 1943, No. 21386. [Class 40 (iii)] [Also in Group XXXV] In an automatic rotary speed control system an activated tuning fork having a natural frequency corresponding to the desired speed of the rotary system, controls a contact to connect intermittently, when the phase difference between the rotary system and the tuning fork exceeds a predetermined value, a potential, corresponding to the phase difference, generated in dependence upon rotation of the rotary system, and continuously varying in the same manner during each revolution of the rotary system, to the grid circuit of a thermionic valve, the anode current of which restores the speed of the rotary system to the desired value. In Fig. 7, motors 37 and 55 driving a transmitter 36 and a receiver 52, respectively, of a facsimile telegraph system in stations remote from each other and connected by wire or wireless, have their speeds controlled by separate tuning forks. Only the fork 61 at the receiving end is shown. This fork operates at a frequency slightly less than the transmitter fork initially, but the energization of its activator coil 76 is controlled automatically to bring the two forks into synchronism. The motors then run synchronously, the receiver motor 55 having a constant lag. The image current is generated at OI which is normally connected through line L to the receiver amplifier RI, but this circuit is interrupted by cain 47 to send synchronizing impulses from oscillator OS which are selected in a combined amplifier, detector and filter RS. The output potential from RS has the waveform of Fig. 8B and a frequency dependent on the speed of the transmitter. This potential is used (a) to operate a line starter clutch 53 and (b) to charge condenser 82 to a voltage dependent on the instant at which brush 68 leaves segment 63. The latter voltage pulses the grid of a tetrode 77, the anode current of which energizes the activator coil of fork 61. The frequency of fork 61 is thereby progressively adjusted until synchronism obtains. Driving contacts 85 of fork 61 control the supply to the screen grid of tetrode 77. The current through these contacts may be reduced by arranging them to control the suppressor grid bias of a pentode serving in place of tetrode 77. Correction for fading, when a wireless link is used, by the use of a valve working under saturation conditions and the.use of impedances to produce the varying potential used to pulse the grid is referred to.