GB554056A - Improvements in or relating to telephone ringers - Google Patents

Abstract

554,056. Transformers. STANDARD TELEPHONES & CABLES, Ltd. March 27, 1942, No. 4073. Convention date, Oct. 22, 1940. [Class 38 (ii)] [Also in Group XXXVIII] In a telephone bell, a rocking armature is mounted to move between the pole faces of a stationary electromagnet and carries a clapper which strikes a gong forming a housing for the whole..In the form shown, the armature, Fig. 8, comprises a permanent magnet 50 to which are secured pole-shoes 51 and an arm 52 carrying a clapper 61. The armature is mounted to rock between the laminated stator poles 14, 15, Fig. 4, of an electromagnet by means of pivots secured to it and joumalled in bearings in front and rear plates bridging the pole pieces. The armature is biased by a spring 63 towards a position in which the axis of the magnet 50 is perpendicular to the line joining the centres of the poles 14, 15, and is tuned by the spring to a natural oscillation frequency equal to that of the alternating current supplied to the field coils 16, 17. The stroke of the clapper may be varied by adjustment of a pivoted cam 40 which forms a stop engaged by a lug 58 on the clapper arm. The clapper strikes a stiff reed 66 secured to the gong and the loudness of the sound may be varied by slight rotation of the gong to alter the point at which the reed is struck. The stator poles 14, 15 are formed by lateral extensions from rectangular laminations constituting, together with a centre portion 70, shown in Fig. 6, which carries the windings, the core of the telephone transformer. The core portion 70 is formed with two longer laminations at one face to provide lugs by which it is attached to the upper and lower limbs of the rectangular portion. The whole assemblage is secured in the gong, which is of a squared form, by a single central screw (not shown).