GB492321A - Improvements in magneto generators for use in telephone or like systems - Google Patents

Abstract

492,321. Magnetos. AUTOMATIC TELEPHONE & ELECTRIC CO., Ltd. March 19, 1937, No. 8175. Convention date, April 13, 1936. [Class 35] A magneto of the telephone type comprises a manually rotatable member 15 connected by means of a resilient coupling to a magnetic armature 30 in such a manner that rotation of the member causes the armature to oscillate between the U-shaped polepieces 35, 36 of a permanent magnet 12 and thereby generate in a coil 37 pulses of current suitable for operating a telephone receiver as a calling signal. In the constructior shown in Figs. 4, 5, the handle 15 is secured to a gear-wheel 16 geared to a wheel 19 on a shaft 20 which carries at its other end. a disc 21 to which a pin 22 is secured in one of the holes 24. A spiral spring 26 is secured at one end 27 to the armature 30, while its other end is wrapped around the pin 22. The armature is pivotally supported in a chamber of non - magnetic material mounted inside the coil 37, parts of the chamber being electrically insulated from one another to prevent the formation of eddy currents. The pole shoes are provided with shims of non-magnetic material to prevent the armature sticking to the poles. On rotating the handle, the armature moves rapidly from one pair of polepieces to the other, the alternate tensioning and relaxation of the spring giving a snap action. In a modification, Fig. 9, the rotatable shaft 15 carries a cam 41 which oscillates the armature 30 against the action of a spring 42. In another construction, Fig. 10, the rotatable shaft 15 carries an eccentric pin 44 which engages a pair of springs 51 secured to the armature 30. The magneto is adapted for use in a telephone system in which a magnetic type of telephone apparatus TA at station A, Fig. 1, is normally connected through keys KA, KB to a similar apparatus TB at the station B. Each apparatus is of the type comprising a cone-shaped diaphragm 50 connected to an armature 51 which is pivoted between the poles of a magnet 53 and carries a winding 52. Each station is provided with a magneto SA, SB according to the invention, and either station can be called from the other by operating its key and rotating' the handle 15 of the magneto.