EM signal generator for clock with electronic alarm - has permanent magnetic particles in base of plastics material housing and diaphragm with mound-shaped flux return bridging piece

摘要

The lower part of the housing receives a carrier plate with a coil core, a coil, a circular magnet and a diaphragm with a central flux return disc. The whole is closed by a resonator cap. A flux return bridging piece (7) extends from the centre of the diaphgram (6) to its edge in the shape of a mound-like projection. The lower part (1) of the housing is formed as a permanent magnet. A carrier disc (5) fixed to the coil core (3) serves as a holder for the coil (4). The lower part is pref. produced from injection mouled plastics material contg. homogeneously distributed magnetic particles. The carrier disc (5) is pref. a plastics material part stabilised by a metal grid. ADVANTAGE - Large free area for oscillation of diaphragm.