GB384346A - Improvements in or relating to methods of synchronisation in television and like syst - Google Patents

Abstract

384,346. Motors. JACOMB, W. W. and BAIRD TELEVISION, Ltd., 133, Long Acre, London. June 22, 1931, No. 18071. [Class 35.] Rotary machines ; driving arrangements.- In a television or like receiving system of the kind in which an electric motor driving the picture reconstituting means is synchronized by means of a tuned oscillator or valve circuit responsive to a frequency component of the incoming signals, the motor may comprise an annular stator provided with four poles and a toothed rotor, or, as shown in Fig. 5, the stator 33 may have two poles 34, 35 only, each provided with bifurcated tips 36 .. 39 of which two, viz, 36 and 39, are wound with copper to render the motor self-starting. In another construction, Fig. 11, a two-pole motor is furnished with a starter comprising a lever 57 fitted with a toothed segment 55 that meshes with a pinion 52 on the motor shaft 48, a buffer 58 contacting, at the end of the lever's movement, with the knob of a tumbler switch 46 controlling the supply of current to field windings 42, 43, while simultaneously the segment 55 is slid axially to disengage the pinion 52. In order to obtain a sharp synchronism the teeth of the rotor are made relatively narrow, while the wave form of the synchronizing current, instead of being sinusoidal, has acute peaks, e.g. as shown in Figs. 7 and 8. The form shown in Fig. 7 may be generated in known manner by overloading the grid of the power valve driving the motor and by working the valve near the bottom bend of its characteristic curve, while the form shown in Fig. 8, is derived by tightening the coupling between the grid and anode of the power valve beyond the point at which self-oscillation would be maintained.