GB509837A - Improvements in or relating to sound reproducing devices - Google Patents

Abstract

509,837. Instruments for deaf persons. STANDARD TELEPHONES & CABLES, Ltd. (Visschers, P. A. J.). Jan. 21, 1938, No. 2068. [Class 40 (iv)] A sound-reproducing device, particularly for use as a deaf-aid instrument, comprises a circular casing 1, a stiff disc diaphragm 27 peripherally mounted in the casing and contacting centrally on one side with the casing and carrying on the other side a receiver unit comprising a vibratory armature 19 mounted on a thin flexible disc diaphragm 18, the armature being also connected to the centre of the stiff diaphragm whereby the comparatively heavy electromagnetic unit in response to voice currents is adapted to transmit vibrations through the diaphragms to the casing which is effective to transmit vibrations to any compact mass with which it is in contact. The stiff diaphragm 27, which has peripheral extensions 25 engaging in recesses 26 in the casing, is connected by a screw 24 to an axial projection 22 of the armature 19 which is secured by screws 32 and a washer 21 to a phosphor-bronze diaphragm 18 attached to an annular polepiece 16. The screw 24 has a head which is engaged by the cover 2 of the casing 1. A ring permanent magnet 9 is clamped between the polepiece 16 and a steel plate 8 carrying a centre polepiece 11. The leads 30 to a speechcoil 13 surrounding the polepiece 11 are taken through an insulator 14 mounted in the disc 8 and are connected to terminal members 29 secured to pivots 7 to which the external leads 4 are attached. The leads pass through a lead-in tube 3 and are held against the floor of the casing by a plate 5 secured to the base by a screw 6.