US2522099A

US2522099A - Portable electromagnetic hearing aid

Info

Publication number: US2522099A
Application number: US10963A
Authority: US
Inventors: Demant William
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-12-20
Filing date: 1948-02-26
Publication date: 1950-09-12
Anticipated expiration: 1967-09-12

Description

Sept. 12, 1956 w. DEMANT 2,522,099

, "PORTABLE ELECTROMAGNETIC HEARING AID Filed Feb. 26, 1948 IN V EN TOR. Wu. L. m M QEMANT .4 TTORNE X Patented Sept. 12, 1950 s PATENT cams PORTABLE ELEGTROMAGNETIC HEARING AID Willian Demant, Copenhagen, Denmark Application-February 26, 1948, Serial No. 10,963 In Denmark December 20, 1946 Section 1, Public Law- 690, August 8, 1946 Patent expires December 20, 1966 The present invention relates to a. portable, electro-inagnetic hearing aid'for bone conduction in which apparatus the armature of the' maghetic system is fastened to the interior wall of a casing,

preferably of non-magnetic material, enclosing the'magnetic system, whereas the said magnetic system is'elastically suspended so that it may oscillate in relation to the armature. 1

In a known hearing aid of this type, the diaphragm consists of a relatively rigid, thick metal plate which for the purpose of reducing the rigidity has been slotted both lengthwise and crosswise. Besides through the slots thus formed, the space between the diaphragm and magnetic system is at the sides connected with the space in the casing surrounding the magnetic system. On account of the relatively great rigidity of the diaphragm, the apparatus will have a natural frequency within the audible range, and by the said arrangement of the apparatus the air space between the diaphragm and the magnetic system cannot serve to dampen these natural, Y oscillations.

These disadvantages are overcome by the hearing aid according to the invention, in that the magnetic system is fastened to the bottom of a bowl-shaped casing across which a relatively invention the advantage is derived that the bowlshaped casing along its edge is provided with threads to which a nut carrying the diaphragm is screwed. This entails the advantage that a readjustment of the distance between the diaphragm and the poles of the magnetic system may very easily be undertaken without the use of special tools.

In the following the invention is explained in detail and described under reference to the drawing showing an embodiment of the invention.

The hearing aid according to the invention consists on the outside of a casing composed of two parts, namely a plate-shaped part I and a bow1-shaped part 2. The armature of the mag- .ZJ-Claims. (o1. na -114) v 2 netic system is in the form of a flat, circular iron disc 3, through the middle of which a hole has been drilled or otherwise made, through which hole a brass bushing. 4 is inserted. The bushing 4 is as shown in the upper part of the drawing provided with a broad collar 5, between which and the armature is placed the diaphragm 6, in the middle of which a hole is provided, and between the diaphragm and the armature a disc I of, for instance, Pertinax or fibre, is inserted in order to prevent the diaphragm from ringing against the armature.

The part of the bushing shown in the lower part of the drawing is beaded around the edge of the hole in the centre of the armature, so that the diaphragm 6%, will be firmly secured between the collar 5 and the disc 1.

Around the diaphragm 6 the edge of a nut 8 is flanged. Into this nut is screwed a bowlshaped casing 9, and the connection is secured by means of a lock nut 10.

To the bottom of the casing 9, the magnetic system is fastened. It consists of a permanent magnet I l with poles l2 of soft iron, around which windings l3 are placed.

Through the bottom of the casing 9 fine canals have been drilled, through which pipes Id of insulating material are inserted. Through these pipes the ends of the magnet windings 13 are taken to soldering webs I5. The pipes M fit tightly into the canals in the bottom of the easing, so that the air may pass from the interior of the casing to the surrounding spaces only through these very thin pipes, the cross-section area of which is further reduced by the wires to the magnet windings. The pipes may, further be entirely closed, e. g. by means of a coating of lac.

As will be understood, there will thus be no possibility or only very slight possibility for the air inside the casing to be caused to flow in and out by the movements of the diaphragm 6. This means that the air inside the casing 9 will act as a dampening cushion during the oscillations of the diaphragm 6. This will entail the advantage that th oscillations of the magnetic system and the casing 9, while the apparatus is in use, will only to a Very slight extent develop into natural oscillations, and when furthermore, the diaphragm 6 is of very thin material while the mass of the magnetic system and the casing 9 is relatively great, it will be understood that the apparatus according to the invention will be able to reproduce sound with exceedingly great purity of tone.

Having now described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A portable electromagnetic hearing aid for bone conduction, comprising an outer casing, an armature member and a resilient sound-receiving diaphragm concentrically and fixedly attached to each other and to the inner wall of said casing, a second bowl-shaped casing inside said first casing being attached along its edge to said diaphragm so as to be supported and substantially air-tightly closed thereby, and an electro-magnet system mounted in said second casing and having pole pieces coacting with said armature member, the second bowl-shaped casing and the soundreceiving diaphragm forming a substantially airtight enclosure for said electro-magnet system whereby an air cushion is provided in said second bowl-shaped casing.

2. A portable electromagnetic hearing aid for bone conduction, comprising an outer casing, a circular resilient sound-receiving diaphragm at its center fixedly attached to the inner wall of said casing in spaced relation therewith, an armature member attached to the center of said diaphragm on the side away from said inner wall, a threaded ring member provided with a flange portion engaging the circumferential rim of said 4 diaphragm, a second bowl-shaped casing inside said first casing and having a threaded portion along its edge adapted to adjustably engage said threaded ring member, said diaphragm thereby resiliently supporting and substantially air-tightly closing said bowl-shaped casing, and an electro-magnet system mounted inside said bowlshaped casing and having pole pieces coacting with said armature member, the second bowlshaped casing and the sound-receiving diaphragm forming a substantially air-tight enclosure for said electro-magnet system whereby an air cushion is provided in said second boW1- shaped casing.

WILLIAM DEMANT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,149,610 Allis Aug. 10, 1915 1,507,171 Hahneman et al. Sept. 2, 1924 2,086,630 Miner July 13, 1937 2,127,468 Greibach Aug. 16, 1938 2,169,306 Lain et a1 Aug. 15, 1939 2,202,906 Hawley June 4, 1940