US 3668334 A
A hearing aid has a pair of spaced electric contacts projecting from its case in a position to hold a battery between them for operating the hearing aid. A removable housing with an open inner end normally fits over these contacts to conceal the battery. The housing contains a radio-frequency pickup detection circuit connected with a radio-frequency pickup coil and provided with a pair of terminals. The hearing aid case has means projecting from it into the housing and detachably engaging the pair of terminals therein to connect the radio-frequency detection circuit with the amplifier in the case. A pickup coil tuned to a different radio-frequency can be connected to the case by simply replacing the housing with a similar one containing such a coil.
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Description (OCR text may contain errors)
United States Patent Schwake  HEARING AID WITH CHANGEABLE BATTERY COVER CONTAINING RF PICKUP con.
 lnventor: William 0. Schwake, Sulphur, Okla. I  Assignee: Radioear Corporation, Canonsburg, Pa.  Filed: May 7, 1970  Appl. No.: 35,464
 U.S. Cl. ..179/107R  Int. Cl ..H04r 25/00  Field ofSearch ..179/107, 179, 1 PC, 29;
 References Cited UNITED STATES PATENT 8' 2,439,411 4/1948 Mitchell... ..325/361 3,315,375 4/1967 Heinz ..179/1 2,302,113 11/1942 Faltico ..179/107 R 2,308,270 1/1943 Cubert ..179/107 R 2,789,160 Gage... ..179/107 R [4 1 June 6,1972
FOREIGN PATENT SOR APPLICATIONS 1,093,839 12/1960 Germany ..179/1 710,388 6/1954 Great Britain ..179/107 R 1,815,836 8/1969 Germany ..179/107 R Primary Examiner-Kathleen H. Claffy Assistant Examiner-Thomas L. Kundert AttorneyBrown, Murray, Flick & Peckham  ABSTRACT A hearing aid has a pair of spaced electric contacts projecting from its case in a position to hold a battery between them for operating the hearing aid. A removable housing with an open inner end normally fits over these contacts to conceal the battery. The housing contains a radio-frequency pickup detection circuit connected with a radio-frequency pickup coil and provided with a pair of terminals. The hearing aid case has means projecting from it into the housing and detachably engaging the pair of terminals therein to connect the radio-frequency detection circuit with the amplifier in the case. A pickup coil tuned to a different radio-frequency can be connected to the case by simply replacing the housing with a similar one containing such a coil.
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HEARING AID WITI'I'CHANGEABLE BATTERY COVER CONTAINING RF PICKUP COIL An important but difiicult application for hearing aids is for children -with very severe hearing losses that have been present from birth or from a very early age, and who must attend'special schools for learning speech or for general education. In a typical schoolroom for such children, the teacher may be located at a substantial and varying distance from the pupil, so that the signal level of the sound received by the child through a standard hearing aid varies considerably in intensity from time to time. To overcome this in part, an induction loop system has been developed and has been in use for many years. The original induction loop systems were operated at audio-frequency. One or more loops of wire were placed in the schoolroom, so that a radiated magnetic field at audiofrequency could be present in the area where the hearing aid was to be used. The power to the loop was furnished by anamplifier having from to 50 watts of power, and the teachers voice was initially picked up by a microphone located close to the teachers face. A hearing aid provided with an inductive pickup coil, such as is also commonly used for telephone pickup with many hearing aids, is able to get a very good signal from the audio magnetic field within the loop area and the child can hear very well throughthis source.
In additionto the radiation of audio-frequency signals from a loop system, modulated radio-frequency signals have also been employed. The disadvantage ofspillover from one room to an adjacent room which often occurs with audio systems, is avoided by using a radio-frequency system. This is accomplished by using different radio-frequency channels for rooms that are so close together that the loop signals would otherwise interfere with one another, or by utilizing certain frequency modulation techniques.
In addition to hearing the teachers voice through the induction loop system, the child must also hear his own voice and generally this is'accomplished by having the hearing aid'arranged so that both the loop signal and the acoustic signal through the microphone of the hearing aid can be mixed simultaneously. Thus, in a loop equipped room, the child hears both his own voice and his teacher's voice very well.
Also, when the child is not in the classroom, he must'havea good acoustic hearing aid to give him the maximum number of hours of exposure to sound during the day that is possible. He normally can do this by switching the hearing aid to the microphone only position on the hearing aid, with the pickup of audio-frequency magnetic fields cut out.' This switching is not necessary in the case of a radio-frequency pickup, since while he is away from the radio-frequency induction'loopin the schoolroom he is very unlikely to encounter'any radiofrequencies in the bands where the hearing aid is sensitive.
In'many cases, the hearing aid equipment used for a child when a radio-frequency loop system is employed has been very bulky and cumbersome for a small child to wear. A large box is strapped on the child's chest and large headphones are often employed, much to his discomfort. On the other hand, 7
with the high quality now available from small wearable hearing I aids, particularly those equipped with wide-band microphones, the performance of the small aids is as good as and sometimes even better than that of the large box-type units when the small hearing aids are employed in a classroom with an audio-frequency induction loop, andof course the also are very good for direct acoustic pickup.
It is among the objects of this invention to provide a hearing aid which is very small in size, which can be used by a child for audiofrequency induction loop pickup as well as for acoustic pickup, and which is readily converted in the classroom whenever radio-frequency pickup is desired.
The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a front view of a hearing aid designed for acoustic and audi'o-frequency induction loop pickup, with part of the battery housing broken away;,
FIG. 2 is a side view thereof;
FIG. 3 is a greatly enlarged fragmentary vertical section through the hearing aid converted for radio-frequency induction loop pickup;
FIGS. 4 and 5 are horizontal sections taken on the line IV- IV and V-V, respectively, of FIG. 3;
FIG. 6 is a vertical section taken on the line VIVI of FIG. 3; and
FIG. 7 is a wiring diagram. g 7
Referring to FIGS. 1 and 2 of the drawings, a hearing aid provided interiorly with a microphone and an amplifier and with an external'receiver 1, also contains within its case 2 an audio-frequency pickup system, one purpose of which is inductive pickup of telephone conversations. It also can be used with an audio-frequency radiating loop in a schoolroom. Projecting from the lower end of the case is a pair of spaced electric contacts 3 and 4 that are connected into the hearing aid circuit. A battery 5 for powering the unit is held between these contacts, at least one of which is a spring contact. The two contacts and the battery normally are covered and concealed by a small housing 6 that has an open upper or inner end that allows it to be fitted up around them. The housing is held in place by connecting members, preferably in the form of reversely bent leaf springs 7 projecting from the bottom of the case. These engage the heads of rivets 8 or the.like in the vertical endsof the housing. The springs have humps below the rivet heads to hold the housing up against the case, but it can be removed easily in order to change the battery by simply pulling downward.
It is a feature of this invention'that this hearing aid can readily be converted, even by a child, to one provided with a radio-frequency pickup circuit, either amplitude or frequency modulated. Accordingly, as shown in FIGS. 3 to 6, another battery housing 10 is provided thatis similar to the one just described in all respects, except thatit is somewhat deeper so that there will be room in it to accommodate a radio-frequency pickup system. This system is mounted on the bottom of a small insulating plate ll'that fits in the lower end of the housing to form a radio-frequency pickup converter unit. The system includes one or more suitable radio-frequency pickup coils, such as coil 12, preferably provided with a high permeability powdered iron or ferrite core 12A to increase pickup sensitivity, fixed condensers 13 to tune the coil, a radiofrequency by-pass condenser 14, an audio-frequency coupling capacitor 15, the necessary resistors l 6 and a rectifier, such as a silicon diode 17. This radio-frequency detection circuit is electrically connected to the lower ends of a pair of metal terminals l8 in the form of thin vertical stainless steel strips, the lower ends of which are bent beneath the ends of the insulated plate and riveted to it. The terminals extend upwardly from the plate in slots in the housing walls and are attached to those walls by rivets l9or the like near the upper end of the housing.
The heads of the rivets are inside the converter housing and fonn detents for engagement by the springs 7 in the same manner as in FIG. 1. However, with housing 10 in place, the springs serve not only to hold the housing, but also to electrically connect the radio-frequency pickup system in the housing to the amplifier in the case. This means that at least one of the springs must be insulated from the battery contact beside it, which can be done by clamping a thin strip 21 of insulation between them and by using an insulating washer to separate the spring from the screw that holds the adjacent battery contact. The upper ends of the springs are connected by wires 22 and 23 with the circuit inside the case. The springs therefore carry the signal from the pickup system into the input of the hearing aid amplifier. There also is a switch 24 on the case (FIG. 1) forshifting from the audio-frequency to the radiofrequency pickup when a child goes from a room equipped with an audio-frequency loop to one equipped with a radiofrequency loop.
The wiring diagram in FIG. 7 shows how the converter becomes wired into the hearing aid circuit when housing I0 is plugged onto the hearing aid case. The microphone is at 26 and the audio-frequency pickup coil at 27.
One of the major advantages of this invention is that radiofrequency converters as described herein can be provided which are tuned to difierent radio-frequencies. In a relatively small device, it has been found easy to provide pickup coils that have good sensitivity over a range of at least from 20 kHz to 400 kHz. Each converter is tuned to the desired frequency by the use of a suitable number of turns on the pickup coil and by the proper choice of tuning capacitance. Consequently, when several different rooms are equipped with radiofrequency transmitters of different frequencies, the child can move from one room to the other and still hear well by merely changing the converter on his hearing aid. A number of radiofrequency transmitters are already installed in schools for the deaf and in other schools, and the converters can be made to provide the necessary frequency for good pickup of the signals from existing installations, as well as from new installations. A supply of converters can be maintained in each room for the particular frequency that its transmitter radiates, and for convenience they can be color coded for the different rooms. Each converter is identified on the outside with the frequency to which it is tuned, so that it can be properly identified at all times.
It will be seen that housing not only serves its regular function of covering the battery, but also as a housing for the radio-frequency pickup system. Also, the leaf springs projecting from the hearing aid case, which ordinarily are used only for holding the battery housing 6 in place, now have the additional function of electrically connecting the radio-frequency pickup system with the amplifier circuit in the case. If that system is not desired or if the child is not in a room where a radio-frequency signal is being used, the hearing aid can be converted back to a standard instrument by merely removing the bottom housing and replacing it with the standard battery housing or cover 6. This normally would be done when the child leaves the schoolroom for home or while eating a meal at school. Some schools recognize the importance of a child wearing his hearing aid during school vacations; The hearing aid disclosed herein provides the child with a single hearing aid suitable for all purposes; acoustic, audio-frequency pickup and radio-frequency pickup, so it can be used for vacation periods as well as for school.
l. A hearing aid for the hard of hearing comprising a case, a hearing aid amplifier circuit in the case adapted to be connected with a receiver, a microphone connected with the circuit, a pair of spaced electric contacts projecting from the case and connected in said circuit, said contacts being positioned to hold a battery between them outside of the case, a removable housing with an open inner end normally fitting over said contacts to conceal them and any battery between them, a radio-frequency pickup coil mounted in the outer end of said housing, a radio-frequency detection circuit in the outer end of the housing connected with the coil and provided with a pair of terminals, and conductor means connected in said amplifier circuit and projecting from the case into the housing and detachably engaging said terminals to connect said circuits, whereby a coil tuned to a different radiofrequency can be connected with said amplifier circuit by simply replacing said housing with a similar one containing such a coil.
2. A hearing aid according to claim 1, in which said conductor means are leaf springs pressing against said terminals to also hold said housing in position on the case.
3. A hearing aid according to claim 1, in which said conductor means are leaf springs, and said terminals extend toward the open end of the housing and are provided with detents engaged by said springs to hold said housing in position on the case.
4. A hearing aid according to claim 3, in which said detents are the heads of fasteners securing said temiinals to the wall of the housing.
5. A hearing aid according to claim 1, including an insulating base supporting said coil and radio-frequencyl detection circuit and concealing them from the open end of e housing,
said terminals including metal strips extending from the opposite ends of said base along the housing wall toward said open end, and said conductor means being leaf springs overlapping said strips.
6. A hearing aid according to claim 5, including fasteners securing the free ends of said strips to the housing wall and having heads inside the housing, and said springs being formed to snap over said heads when the housing is applied to the case.
7. A hearing aid according to claim 1, in which said conductor means are leaf springs extending along the outer surfaces of said battery contacts, and said hearing aid includes insulation separating at least one of the battery contacts from the adjacent leaf spring.
8. A hearing aid according to claim 1, including an insulating base supporting said coil and radio-frequency detection circuit and concealing them from the open end of the housing, said temiinals including metal strips extending from the opposite ends of said base along the housing wall toward said open end, and fasteners securing the free ends of the strips to the housing wall and having heads inside the housing, and said conductor means being leaf springs constructed and arranged to snap over said heads when the housing is applied to the case, whereby to hold the housing against the case.
9. A hearing aid according to claim 1, including an insulating base supporting said coil and radio-frequency detection circuit and concealing them from the open end of the housing, said terminals including metal strips extending from the opposite ends of said base along the housing wall toward said open end, and fasteners securing the free ends of the strips to the housing wall and having heads inside the housing, and said conductor means being leaf springs, the springs extending along the outer surfaces of said battery contacts, and the hearing aid including insulation separating a battery contact from the adjacent leaf spring.