Patent GB-405493-A (GB)
Title: Improvements in or relating to hearing-aid devices
IPC: H04R11/00
Filed: 1933-04-28
Abstract: 405,493. Instruments for deaf persons. SONOTONE CORPORATION, 19, West 44th Street, New York, U.S.A.-(Assignees of Lieber, H., and Nicholides, E. C. ; 19, West 44th Street, New York, U.S.A.) April 28, 1933, No. 12445. Convention date, June 1, 1932. [Class 40 (iv).] A hearing aid of the bone conduction type comprising an armature co-operating with magnet poles has a small air gap between the armature and the poles of a size of the order at which freezing would normally occur between the armature and poles, a vibration transmitting member being provided between the armature and the bone structure of the user adapted, when the device is in operative position, to exercise reactive forces on the armature opposing its freezing and maintaining its vibration with sufficient power to secure satisfactory hearing. Fig. 2 shows one form of the device in which the contact button 8 of the vibrator 6 is held against the mastoid temporal bone by a head clip 7, the coil 5 of the vibrator being connected in series with a microphone 2, variable resistance 11 and battery 4. If desired, an amplifying arrangement may be provided between the microphone 2 and vibrator 6. The vibrator, Fig. 4, comprises a pair of angularly bent magnets 21 assembled with like poles 22 on opposite sides of the enlarged base 23 of a core member 24 which projects into an aperture in an outer pole plate 26 which is slotted to reduce eddy currents and abuts at its outer ends against the upper ends of the magnets 21. The core 24 is surrounded by a coil 5 which is covered by a strip of varnished cloth &c. to which is secured a pair of contact strips which are in electrical connection with sockets 78, 79 located in the lower wall 63 of the casing and adapted to receive plugs 80 on the cords 3. A brass &c. clamping strap 37 is secured by screws to the plate 26 so as to hold the magnets 21, core 24, plate 26 and coil 5 together as a unit, the enlarged base 23 of the core being riveted to the bottom of the strap whilst spring members 39 are preferably inserted between the outer magnet surfaces and the strap. The side arms of the strap are also formed with wing plates adapted to be clamped to the casing projections 65 by screws 66. An insulator ring 45 holds the end of the core spaced from the plate 26. A strip diaphragm 51 carrying an armature 56 has its ends clamped between blocks 52, 53 on the plate 26, the blocks 52 being slotted so as to be adjustable along the plate 26 to vary the length of the vibrating diaphragm. The armature 56 carries a rod 58 passing through a longitudinal perforation 57 in the core 24 and carrying at its outer end the contact button 8. The rod 58 is guided by a spring strip 42 overlying a rectangular opening in the strap 37 to which it is secured at its outer end. A sheet metal partition 67 is mounted opposite the wall 60 to form a narrow channel 68 adapted to receive the end 72 of a member 71 carried by the clip 7. Fig. 12 shows a modification in which the vibrator is carried by a handle 90 in order to enable the device to be applied to the skull or spinal column. The handle is formed with a longitudinal slot within which the cords 3 are inserted, the lower portion of the slot being covered by a spring- controlled hinged cover 95. According to a further modification, Fig. 14, the vibrator is combined with a spectacle frame 101 so that the contact member 103 bears on the nasal bone. The leads 105, 106 from the coil 5 are arranged in channels in the upper and lower parts 108, 109 of the frame of one of the lenses and thence over the hinged joint through channels 110 in the temple 111.