GB1234273A - - Google Patents

Abstract

1,234,273. Electro-mechanical transducers. TIBBETTS INDUSTRIES Inc. 13 May, 1968 [16 May, 1967], No. 22598/68. Heading H4J. An electro-mechanical transducer (Figs. 1, 2, 3) (e.g. a microphone or receiver of a hearing aid) has within a casing 7 of high magnetic permeability material, magnets 8 and 9 which provide polarizing flux across a working gap. An armature comprises a generally U-shaped yoke 1 and an armature leg 2 which extends from the working gap through a signal coil 12 to the cross-piece 38, 39 of the yoke 1. The leg 2 is compliant in flexure. The cross-piece 38, 39 is compliant in torsion about an axis perpendicular to the leg 2. It is within the easing 7 and substantially closes, for magnetic shielding purposes, an opening in the casing 7. The cross-piece 38, 39 is connected by portions 40, 41 to ends 42, 43 connected to the casing 7. The position of the leg 2 in the working gap is adjustable by twisting inelastically the crosspiece 38, 39 the plastic deformation being substantially confined to the cross-piece 38, 39. An adjusting pad 4 is provided and this may be held by jaws of an arm for adjustment of the location of the leg 2. A U-shaped closure 14 of high magnetic permeability material is at one end. A terminal board 15 has terminals 28, 29 connected to the coil 12. The magnets 8, 9 have tapered polepieces 10, 11 separated by non-magnetic shims 44, 45. The vibratable end of the leg 2 is connected to a diaphragm 17 by a pin 6. The other end of the diaphragm 17 has a flexural pivot 5. A top cover 21 of magnetic material is provided and the air space above the diaphragm 17 is connected through an aperture 22 to an air space formed by an end closure 24. An acoustic connector 25 and a sleeve 26 contain an acoustic impedance. In one alternative embodiment the armature yoke comprises a cross-piece 107 (Fig. 30) having arms 501, 502 extending away from the armature leg 2. Arms 501, 502 are connected to the casing 7 (Fig. 29, not shown). In another alternative, the armature leg (200, 201), Fig. 7 (not shown) is composed of two layers. The adjusting pad (400), Figs. 9 to 11 (not shown) is integral with the yoke (100). An armature leg (202), Figs. 12 to 14 (not shown) has an end piece (372) formed at right angles, an adjusting rod (401) and a filler piece (300) all made from one piece. Other constructions of armature are described (Figs. 15 to 28 and Figs. 31 to 36, not shown).