GB983997A - Moving coil transducer for telecommunication purposes - Google Patents

Abstract

983,997. Telephone receivers. G. KRONE. July 31, 1962, No. 29329/62. Heading H4J. A moving-coil receiver insert has a casing, divided into two acoustically coupled chambers to smooth the frequency response of the device, and contains a pot-type magnet system held by an apertured support ring which also forms a partition between the chambers. As shown, the magnet system consists of a permanent magnet 6, a polepiece 7 and pot-shaped return 8, both of magnetically soft material, held together by hollow rivet 9. The outside of the return 8 has a lip 8a which engages a synthetic support ring 2 which divides the space between the casing 1 and the return 8 into two chambers 14, 15. Ring 2 has apertures 13 covered by an elastic covering 16 of felt, textile fabric or synthetic fabric, covered by a retaining ring 17 which is held in position by three hollow rivets 18 formed with solder tags 18a. Coil 10 is held in the air gap of the magnet system by diaphragm 4 which is separated from pressure disc 20 of magnetically soft material by a synthetic plastic ring 19. Disc 20 is covered with a protective foil 21, and the edges of these and the diaphragm 4 are clamped against a shoulder of the support ring 2 by elastic pressure ring 22 which is held in place by cover 23 of casing 1. Coil 10 is connected electrically through rivets 18 and tags 18a to the casing 1 and to the central electrode 24 which is insulated from the casing 1. In a second embodiment the apertures in the support ring are partially filled with felt plugs held in place by apertured members. An apertured shield is inserted above the support ring to divide the upper chamber into two parts.