GB1338092A - Transducers - Google Patents

Abstract

1338092 Audio transducers COSMOCORD Ltd 19 April 1971 [28 Jan 1970] 4084/70 Heading H4J A magnetic transducer comprises a closed magnetic circuit including two pairs of permanent magnets having unlike poles adjacent to form magnetic gaps and a vibratable armature extends through both gaps and through a coil. The Figure shows an exploded view of one form of microphone in which the magnetic circuit is formed by magnet pairs 10, 11 and 12, 13 and magnetic members 15 and 16. The magnets 10 and 11 clamp an end 14a of the armature 11 thickened by the addition of coatings or layers of plastics or metal, while spacers 17 and 18 similarly space the magnets 12 and 13 to allow the end 14b of the armature to vibrate. Apertures such as 15g in the magnetic members allow for the insertion of two coils which surround the armature. The assembly is mounted in a casing not shown which transmits vibrations from one face of the casing which acts as a diaphragm to the armature via a driving pin shown connected to the armature. Vibration of the armature 14 displaces the end 14b within the gap between magnets 12 and 13 causing magnetic flux to flow backwards and forwards through the armature. The resultant flux flow induces currents in the coils. Various magnetic shunts Figs. 1, 6 and 8 using a displaceable auxiliary magnet or deflectable magnetic coupling extensions in each case controlled by an adjustment screw are treated adjacent the end 14a of the armature to render the effective position of the armature adjustable to allow the initial flux to be set to zero.