GB624510A - Electro-acoustic transducer - Google Patents

Abstract

624,510. Electromechanical transducers; diaphragms. MASSA, F. July 19, 1946, No. 21644. Convention date, July 23, 1945. [Class 40 (iv)] The diaphragm of an electromagnetic transducer is moulded very thick so that no external cover is required. The body 1 of the transducer is also moulded, and may have a permanent magnet 3, Fig. 2, and polepieces 2 as inserts for cooperation with a stack of armature laminations 5 moulded into the diaphragm 4. The opposed faces of the body and diaphragm are machined and cemented together. In a modification (Fig. 3, not shown), the permanent magnet and polepieces are replaced by a stack of laminations energized by a D.C. polarizing current through the coils 6 in addition to the audio-frequency current. In Fig. 4, a bimetallic magnetostriction element 15 is secured to the body 1 and actuates the diaphragm through a pin 19. A piezo-electric element (Fig. 5, not shown) may have three corners secured to the body, the fourth corner actuating the pin 19. The leads may enter the body through a moulded tapered sleeve 10 prevented from being pushed in or pulled out by the engagement of a flange 11 with lugs 12. To reduce the response to high frequencies, the device, used as a loud-speaker, may be placed beneath a cushion. When used as a headphone, it may be encased in sponge rubber 29, which may have central openings, and the body 1 may have ribs 23 pivotally secured to a rod 25 rotatable in a bracket 26 secured to the headpiece.