Patent GB-1514097-A (GB)
Title: Vocal prosthesis for laryngoplegics
IPC: A61F2/20
Filed: 1976-02-05
Abstract: 1514097 Dumb aids DR KUHN & CO GmbH 5 Feb 1976 [22 Feb 1975] 04555/76 Heading H4J A dumb aid (Fig. 2) comprises a sound head 16 (Fig. 5) including a hard membrane 10 clamped in a housing part 4. The hard membrane 10 is driven by a vibratory coil 15 on the ram 14 and the ram 14 and coil 15 are held by a soft membrane 6. The coil 15 is arranged in the field of a permanent magnet system 1, 2, 3 and the coil 15 is energized by a signal generator /control part. The permanent magnet I is a hard magnetic material of the type RECO 5  (where RE is one or more of Y, La. Ce. Pr, Nd or Sm). The sound head 16 is readily releasable from the generator/control part and when removed electrical connection between the sound head and generator/control part is effected. When the sound head 16 is removed it may be pivotally accommodated in the bracket 24 (Figs. 7, 8, not shown) of a strap (25) fastened to a neck band. The signal generator/control part includes a signal transmitter 26 (multivibrator with final power stage) and two potentiometers 27, 28 for adjusting frequency and volume respectively. A switch-on device 29 has a locking ring 31 to prevent accidental actuation. A rechargeable battery 30 is included. The sound head 16 has a screw cup 9 and the hard membrane 10 is clamped between two elastic rings 11,12 of foamed plastics and drawn towards a tensioning disc 13 resting on an inwardly protruding flange within a screw cap 9. A stop 17 acts on a projection of the hard membrane 10 and transmits vibrations of the ram 14. The ram 14 and coil 15 are supported by a soft membrane 6 tensioned across the end surface of a hollow cylindrical housing part 4. The soft membrane 6 is stuck to the top of a fibre ring 5 within the housing part 4. Fig. 5 shows, on the right side, the ram 14 and coil 15 slightly below the rest position and, on the left side, the location when current flows through the coil 15 to press the ram 14 against the stop 17. Two flexible braids 18 are connected to the coil 15 and by cable 21 to the generator/control part. The magnet system comprises a permanent magnet disc 1 between pole rings 2, 3. Ring 2 has a core which extends to the edge of the pole ring 3. A sleeve 32 force fits the pole rings 2, 3 and permanent magnet disc 1 together and acts as a guide for the coil 15. The arrangment protects disc 1 from chipping and shocks. A circular shape is shown but other shapes, e.g. polygonal, may be employed. The frusto-conical shape of the pole ring 3 minimizes weight. The magnet system is retained by a ring 7 projecting slightly over pole ring 2. The housing part 4 and sleeve 32 are of plastics material. Adjustment of the hard membrane 10 relative to the ram 14 is effected by twisting the screw cap 9. The sound head and generator/control part are removably secured together by screws 20 which engage key-hole shaped holes 19 in the retaining ring 7. Slight rotation secures and releases. The connecting cable 21 is stored in a cavity 23 having a spool 22. In use the sound head 16 is fastened to a neck band and the generator/control part is accommodated in the user's clothing. The switch 29 may, if desired, be separate and constructed as a flat element with a large actuating surface. The switch actuator may be flat or housed in a flat elastic envelope and accommodated under the armpit or laterally on the user's waist for operation by the elbow. In another embodiment the sound head 16 and generator/control part make electrical connection when they are mechanically connected together. When mechanically disconnected an adapter cable is at one end firmly attached to the bracket for the sound head on the neck band and at the other end has a plug and socket or other releasable connection with the generator/control part.