GB191517247A - Improvements in and relating to Talking Machines and Driving Mechanism therefor. - Google Patents

Abstract

17,247. British Thomson-Houston Co., [General Electric Co.]. Dec. 8. Driving; speed, regulating; turntables. - The record-support of a talking - machine is provided with a band of electrically - conducting material which is set in motion by eddy-current action when influenced by a shifting magnetic field. As shown in Fig. 2, the turntable has a turneddown rim of aluminium, copper, &c. passing between two electro - magnets 17, 18 energized by coils 21, 22. The coil 21 surrounds the central leg of a three - logged magnet. having a substantially closed magnetic circuit, and its inductance is therefore high. The magnet 18 is of U-shape, and the inductance of its coils 22 is lower on account of the air gap The coils are connected in parallel to alternating-current leads 24, which may be coupled by a plug to an ordinary lamp socket, and a non-inductive resistance, such as a lamp 23, is placed in series with the coils 22. A difference of phase is thus produced between the currents in the coils, and the resulting shifting magnetic field across the gap rotates the turntable. The speed is regulated by a centrifugal brake comprising a governor 36 mounted in a frame 31 and driven by a friction-wheel 35 pressed against the underside of the turntable by springs 32, 33 supporting the frame 31. At a certain speed, determined by the adjustment of a pointer 41, a rotary disk 37 moves axially into engagement with an adjustable brake block 38. The turntable may be arrested by a brake lever 47. The lamp 23 serves to illuminate the machine and facilitates the changing of records and needles.