TELEPHONE RINGER

1,217,577. Reciprocating motors. STANDARD TELEPHONES & CABLES Ltd. 21 March, 1968, No. 13710/68. Heading H2A. [Also in Divisions G4-G6] A reciprocating motor including a magnetic device for use as a telephone ringer employs a single H-cross-section soft iron core for a coil 13 which is energized by A.C. to cause an armature 50 to rock between polepieces 15 and (16) which are arranged to have the same polarity, such that a hammer 70, attached to the armature strikes a pair of bells (not shown). The polepieces are formed by extensions of the cheeks 11 and 12 of the core and extend through slots in a non-magnetic support plate 20 which is adjustably mounted on cheeks 11 and 12 by screws 80 and slits 81 and is equipped with a permanent magnet 30 attached on the side nearest coil 13. Magnet 30 is arranged'to have its magnetic axis perpendicular to the longitudinal axis of the magnet so that the polepieces each have the same polarity. The armature is arranged to pivot on semi-cylindrical fulcra (24), (Fig. 4, not shown) attached to plate 20 at a point intermediate the ends of the armature, a flat cross-shaped spring 60 being employed to give the armature a rest position substantially parallel to plate 20. Each of the two limbs of the cross has holes 61 and (63) by which means the cross is attached by rivets 23 through holes 61 to the plate 20 and by rivets 51 through holes (63) to the armature. Non-magnetic rivets 82, 83 are provided to prevent the armature locking in one position. Alternatively, the entire H-member can be coated with plastics material to achieve the same object. Figs. 5 to 8 (not shown) illustrate an alternative embodiment in which the hammer extends from the armature in the opposite direction to that shown through an aperture in the support plate and under the coil.