US3270146A - Hearing aid - Google Patents

Description

Aug. 30, 1966 E. EBERHARD ETAL 3,270,146

HEARING AID Filed March 14, 1965 3 Sheets-Sheet l Fig. IA

INVENTOR 5 ATTY'S.

Aug. 30, 966 E. EBERHARD ETAL 3,270,146

HEARING AID Filed March 14, 1963 Q .z Sheets-Sheet 2 "*TO RECEIVER INPUT I I0 TRANSISTOR 26R 26 loo INPUT HOLES FOR TERMINAL CAPACITOR LEADS I08 +I.25v INPU TERMIN I06 ll8 TRANSISTOR To RECEIVER Fig. 3

TRANSISTOR I-llB-I I|-I04-| L 28 I l i -IO2* i T'T'l I L I \CAPACITOR INVENTORS Everett Eberhqrd Fig. 4 R/chard T. Martin ATTYS.

Aug. 30, 1966 E. EBERHARD ETAL 3,270,146

HEARING AID I Filed March 14, 1963 5 Sheets-Sheet a TO RECEIVER INPUT HOLES FOR CAPACITOR TERMNAL LEADS +I.25v INPUT TERMINAL I TO RECEIVER lg TRANSISTOR 20s 3|8 /TO RECEIVER Fig 7 l NPUT 302 I k 7 mo .5

330 SM 304 313 3'0 HOLES FOR INPUT CAPACITOR TERMINAL LEADS INPUT TERMINAL 318 To RECEIVER 8 INVENTORS Everett Eberhard Richard T Martin BY MKCIM ATTY'S.

United States Patent 3,270,146 HEARING AID Everett Eberhard, Phoenix, Ariz., and Richard T. Martin,

Minneapolis, Minn., assignors to Motorola, Inc., Chicago, 111., a corporation of Illinois Filed Mar. 14, 1963, Ser. No. 265,125 3 Claims. (Cl. 179107) The present invention relates to hearing aids, and it relates more particularly to an improved miniaturized hearing aid of the transistor amplifier type.

The improved miniaturized hearing aid unit to be described is completely contained with-in an extremely small housing. The unit is adapted to be worn directly in the ear, or to be inconspicuously supported behind the ear. The unit is preferably symmetrical so as to constitute a dual fitting instrument which can be worn on or in either ear.

Many attempts have been made in recent years to miniaturize hearing aids, so that the entire unit may be supported on the ear. These attempts at miniaturization have been made in order to obviate the necessity for bulky and unsightly equipment about the person of the wearer.

Problems have been encountered, however, in the use of many of the prior art hearing aids of the above mentioned miniature type. This is because the space requirements are such that the prior art active circuits cannot be properly encapsulated or otherwise protected. This has resulted in relatively rapid corrosion in and deterioration of the prior art instruments due to the effects of perspiration, and the like.

The hearing aid of the present invention, as will be described, is capable of being miniaturized to such an extent that its active components can be encapsulated Without exceeding the weight and space requirements of the overall unit. The instrument of the invention, therefore, can be adequately protected against the above mentioned corrosive and deteriorating effects.

The hearing aid to be described is a fixed-level instrument for mild nerve type hearing losses. The instrument, however, has also proven effective as a full-time or a part time instrument in the moderate or strong loss range-s.

An object of the invention is to provide an improved hearing aid of the above mentioned type which requires a minimum of component parts in order to achieve its desired purpose, and yet which is capable of efficient and trouble-free operation.

Another object of the invention is to provide such an improved hearing aid which may be produced on a relatively economical basis and marketed as a relatively inexpensive unit.

Yet another object of the invention is to provide such an improved hearing aid which may be constructed to occupy materially less volume than the prior art instruments of the same general type, so as to be appropriate for encapsulation and other like protective measures.

A still further object of the invention is to provide such an improved hearing aid which is rugged in its construction and which is therefore capable of withstanding rough usage.

Another object of the invention is to provide such an improved hearing aid which is highly resistant to the adverse effects of moisture and other corrosive agents.

A feature of the invention is the use of thin-filmed conductors and resistors in conjunction with transistors in the amplifier section of the instrument. Such a. construction, as will be described, provides an amplifier which occupies about half the volume of the prior art amplifiers of the same general type.

Another feature of the invention is the provision of a hearing aid of the miniaturized type for use directly in or on the ear of the wearer, and having an amplifier sec- "ice tion of a size and weight such that it may be readily encapsulated so as to render the unit highly resistant to moisture and other corrosive agents.

Yet another feature of the invention is the provision of adjustable short-circui-ting tabs for use in conjunction with the thin-filmed resistances in the transistorized amplifier section of the hearing aid, so that the resistance of the resistances may be easily controlled to take care of characteristic variations in the different transistors used in the amplifier section.

Basically, the thin-filmed resistance consists of a conducting film of carbon, metal or metal oxides deposited on an insulating substrate. The value of the thin-film resistance is controlled by controlling the thickness and length of the film. The thin-film resistance is usually coated with an insulating protective varnish.

In a constructed embodiment of the invention, thin-film resistances have been formed by using tin oxide deposited on a ceramic substrate. The conductors interconnecting such resistances were also formed as a thin-film on the substrate, and these conductors were formed of chromegold, in the constructed embodiment.

The transistorized hearing aid of the present invention utilizes a thin-film resistance and conductor construction which, as will be described, makes possible a material size reduction in the active component of the unit. This enables encapsulation techniques to be used without result-ing in an unduly bulky or heavy instrument.

The encapsulation of the active components of the hearing aid of the invention precludes any possible external contact. Such encapsulation not only protects the unit from external corrosive effects, but renders the assembly extremely rugged from a mechanical standpoint, and enables it to be subjected to rough usage without the likelihood of damage.

In addition, a flexible circuit construction is provided in the hearing aid unit to be described, this being due to the short-circuiting tabs referred to above. These tabs provide for adjustable resistors in the amplifier circuit,

and they also form convenient resistor taps. The adjustable resistor feature of the circuit permits adjustments to be made to accommodate wide characteristic variations which are normally found between different transistors of the same type. o

Other features and advantages of the invention will become apparent from a consideration of the following description, when the description is taken in conjunction with the accompanying drawings in which:

FIGURE 1A is a side perspective View of, on an enlarged scale, a miniaturized hearing aid unit constructed in accordance with the present invention for direct mounting within the ear of the wearer;

FIGURE 1B shows the unit of FIGURE 1A, adapted to be supportedbehind the ear of the wearer;

FIGURE 2 is a circuit diagram of a transistorized amplifier appropriate for use in the unit of the invention;

FIGURE 3 is a plan view of the actual constructional details of the amplifier of FIGURE 2, and illustrating the manner in which thin-film conductors and thin-film resistors are supported on an insulating substrate;

FIGURE 4 is a side elevational view of the amplifier section of FIGURE 3;

FIGURE 5 is a circuit diagram of a transistorized amplifier, constituting a modification of the circuit of FIG- URE 2;

FIGURE 6 is a plan view of the mechanical details of the amplifier of FIGURE 5;

FIGURE 7 is a circuit diagram of yet another modification of the transistorized amplifier of FIGURE 2; and

FIGURE 8 is a plan view of the constructional details of the amplifier of FIGURE 7.

The constructional details of a hearing aid unit con- 3 structed to incorporate the concepts of the present invention are shown in FIGURE 1A. The unit of FIGURE 1A includes a casing which may have a generally rectangular configuration.

The casing 10 has a tilted, generally circular portion 12 formed on its forward wall, and a receiver 14 is mounted on the portion 12. The receiver 14 includes the speaker of the unit.

A receiver tip, or earpiece, 16 is detachably mounted on the receiver 14. The receiver tip 16 is shaped to extend directly into the ear canal of the wearer to support the entire unit within the ear. The unit is symmetrical so that it can be worn, without any modification, in either ear.

A fiat, rectangular shaped microphone 18 is supported within the casing 10 adjacent the rear wall of the casing, and the rear wall is apertured adjacent the microphone to permit the sound Waves to impinge on the microphone. The aperture in the rear wall may be covered by a cloth 20. The microphone 18 is electronically coupled to the receiver 14 by an amplifier section 22. A battery 24 for the unit is mounted in the circuit portion 12 of the casing.

The unit of FIGURE 1A may be supported inconspicuously behind the ear of the wearer by means, for example, of a plastic tube 30, shown in FIGURE 1B. The tube 30 extends around the ear, and it includes a coupler 32 at one end which is inserted into the canal. An adapter 34 is mounted on the other end of the tube. The ear piece 16 in FIGURE 1A is removed, and the unit of FIGURE 1A may then be clipped onto the adapter 34, as shown in FIGURE 1B.

The amplifier section 22 of the hearing aid unit may be constructed of thin-film resistances and conductors, as mentioned above. This section may take the form shown in FIGURES 3 and 4, for example, or it may take the form of FIGURE 6 or 8, or it may take other equivalent forms.

An appropriate transistorized circuit diagram for the amplifier section 22 of the hearing aid is shown in FIG- URE 2.

The amplifier of FIGURE 2 includes a pair of input terminals 100. One of the input terminals 100 is grounded, and the other is connected to a coupling capacitor 102. The coupling capacitor 102 is connected to the base of an NPN transistor 104. The emitter of the transistor 104 is grounded, and its collector is connected to a resistor 106. The resistor 106 is connected to a further resistor 108, and to a resistor 110. The resistor 110 is connected back to the base of the transistor 104.

The resistor 108 may be connected to the positive terminal of a unidirectional potential source (such as the battery 24 in FIGURE 1A) which may, for example, have a potential of 1.25 volts. The capacitor 102 may have a capacity of 2 microfarads, the resistor 106 may have a resistance of 1 kilo-ohm, the resistor 108 may have a resistance of 1 kilo-ohm, and the resistor 110 may have a resistance of 85 kilo-ohms.

The collector of the transistor 104 is also connected to a capacitor 112. The capacitor 112 is connected to resistor 114 and to the base of an NPN transistor 116. The emitter of the transistor 116 is grounded, and the collector is connected to an output terminal 118. The collector is also connected to the resistor 114 and to a grounded capacitor 120.

The capacitor 112 may have a capacity, for example, of 2 microfarads. The resistor 114 may have a resistance of 60 kilo-ohms, and the capacitor 120 may have a capacity of .07 microfarad.

As illustrated in FIGURES 3 and 4, the various components and circuit connections of the circuit of FIGURE 2 may be mounted on an insulating substrate 122, composed, for example, of ceramic and having a rectangular configuration. The various conductors maybe formed on the substrate in the thin-film form of chrome-gold conductors, for example; and the various resistors may be formed on the substrate as thin-film, tin-oxide resistances. The thin-film resistances and conductors may be formed on the substrate 122 in the pattern illustrated in FIGURE 3, and they may be so formed in accordance with appropriate, known thin-film processes.

As shown in FIGURE 4, for example, the transistors 104 and 116 are mounted on one side of the substrate 122, and the capacitors 102 and 112 are mounted on the other side. The particular NPN transistor utilized in the illustrated circuit in a constructed embodiment were of an uncased silicon planar type. This type of transistor is especially suited to the purpose because of the negligible width thereof.

The resistance values of the resistors 110 and 114 may be adjusted to a desired value, dictated by the characteristics of the transistors 104 and 116, this being achieved by the use of a multiplicity of short-circuiting tabs 126. These tabs are formed over the thin-film resistors, and the tabs are selectively connected to the adjacent conductor to provide the required resistance value.

The unit of FIGURES 3 and 4 may be encapsulated in a suitable encapsulating compound, as designated by the dotted line 128 in FIGURE 4. As mentioned previous ly, the extremely small size of the unit renders such encapsulation feasible, because of the relatively low mass of the encapsulating material required, and because of the relatively small overall volume of the encapsulated unit.

As mentioned above, the provision of the shorting tabs 126 provides a solution for the transistor characteristic variation problem. The resistors 110' and 114 can be adjusted to any desired value, by selectively connecting the short-circuiting tabs to the adjacent conductive film.

The modified circuit of FIGURE 5 is essentially similar to that of FIGURE 2, except that it provides for higher gain at lower input impedance to the transistors 104 and 116. The circuit of FIGURE 5, and the lay-out of FIG- URE 6, illustrates the versatility of the thin-film concept in the combination of the present invention. In the circuit of FIGURE 5, elements which are equivalent to those in the circuit of FIGURE 2 have been designated by the same numerals.

In the circuit of FIGURE 5, the input terminals are connected to ground and to the coupling capacitor 102. The coupling capacitor 102 is connected to the base of the transistor 104. The collector of the transistor 104 is connected to a resistor 200 which, in turn, is connected to a resistor 202 and to the resistor 203. The resistor 202 is connected to the positive terminal of the 1.25 volt direct voltage source. The resistor 200 may have a re sistance of 550 ohms, the resistor 202 may have a resistance of 1.8 kilo-ohms, and the resistor 203 may have a resistance of 96 kilo-ohms, for example.

The collector of the transistor 104 is also connected to the capacitor 112 which, in turn, is connected to the base of the transistor 116. The collector of the transistor 116 is connected to the output terminal 118 and to a resistor 204 and to 120. The resistor 204 is connected to the junction of a pair of resistors 206 and 208. The resistor 206 is connected to the positive terminal of the 1.25 volt direct voltage source, and the resistor. The resistor 204 may have a resistance, for example, of 12.5 kilo-ohms, and the resistor 206 may have a resistance of 22.5 kilo-ohms, and the resistor 208 may have a resistance of 124 kiloohms.

The various components of the circuit of FIGURE 5 may be mounted on the substrate 122 in the manner shown in FIGURE 6. Again, the technique of thin-film resistance and thin-film conductor deposition is used to form the amplifier section. Short-circuiting tabs 126 are provided on the resistors 203 and 208, and these tabs may be selectively connected to the adjacent conductors, to make the necessary adjustments in'these resistors to compensate for variations in the characteristics of the transistors 104 and 116.

It Will be appreciated that the circuit lay-out of FIG- URE 6 has a total of two adjustable resistors, and the equivalent of four fixed resistors. However, the lay-out of FIGURE 6 can be placed in the same space as the original thin-film lay-out of FIGURE 2, which incorporates but two adjustable resistors and two fixed resistors.

As mentioned above, the circuit of FIGURE 7 is generally similar to that of FIGURE 2. In the embodiment of FIGURES 7 and 8, however, germanium transistors 300 and 302 are used preferably, so as to achieve a higher power level, and to achieve this with a minimum of transistor cost. In the embodiment of FIGURES 7 and 8, the substrate 304 is provided with two relatively large holes 306 and 308 for receiving the transistors 300 and 302. The substrate is formed of suitable insulating material such as ceramic.

The circuit of FIGURE 7 includes a pair of input terminals 310. One of the input terminals is grounded, and the other is connected to a coupling capacitor 312. The capacitor 312 has a capacity of 2 microfarads, for example, and it is connected to the base electrode of the transistor 300. The transistors 300 and 302 in the latter embodiment are of the PNP type.

The emitter of the transistor 300 is grounded, and the collector is connected to a resistor 313 and to a resistor 314. The resistor 313 may, for example, have a resistance I of 2.7 kilo-ohms, and it is connected to the negative terminal of a 1.25 volt direct voltage source. The resistor 314 may have a maximum resistance of 135 kilo-ohms, for example, and it is connected back to the base of the transistor 300.

The collector of the transistor 300 is connected to a coupling capacitor 316. The coupling capacitor may have a capacity, for example of 2 microfarads, and it is connected to the base of the transistor 302. The emitter of the transistor 302 is grounded, and the collector of the transistor is connected to an output terminal 318. The collector of the transistor 302 is also connected to a grounded capacitor 320 and to a resistor 322. The capacitor 320 may, for example, have a capacitance of 107 microfarads. The resistor 322 may have a maximum resistance, for example, of 210 kilo-ohms.

As shown in FIGURE 8, the circuit of FIGURE 7 is laid out appropriately on the substrate 304. Thin-film resistances and conductors are used to provide an integrated circuit structure. Shorting tabs 330' are formed on the resistor 322 and on the resistor 314. As in the previous embodiments, these shorting tabs may be connected to the adjacent respective conductors, so that the associated resistors may have a desired value to match the characteristics of the transistors 300 and 302.

The invention provides, therefore, an improved miniaturized hearing aid instrument which may be mounted directly in the ear of the user; and which is advantageous in that it may be constructed simply, practically, and economically, to provide a rugged, impervious unit. The unit of the invention is susceptible to rough usage without damage, and it is also highly resistant to adverse effects of moisture and other corrosive agents.

While particular embodiments of the invention have been shown and described, modifications may be made, and the following claims are intended to cover all such modifications.

What is claimed is:

1. In a hearing aid unit which includes a microphone and a receiver means, an amplifier section electronically coupling said microphone to said receiver means and including in combination: a panel-like substrate member formed of insulating material; at least one transistor mounted on said substrate member; a plurality of resistances mounted on said substrate member as film-like deposits; a plurality of conductors interconnecting said transistor and said resistances and mounted on said substrate member as film-like deposits; and a plurality of electrical-1y conductive tabs formed over at least one of said resistances at spaced points therealong and adjacent to at least one of said conductors, said tabs being adapted to be selectively coupled to the adjacent conductor to adjust to the value of such resistance.

2. The structure of claim 1 in which said amplifier section is encapsulated in a material to protect said amplifier section.

3. The structure of claim 1 including a casing in which said amplifier section is mounted, with said casing including a detachable earpiece for the receiver means which is shaped to extend into the ear canal of the wearer to support the hearing aid within the ear.

References Cited by the Examiner UNITED STATES PATENTS 2,999,136 9/1961 Holt et al 179107 3,070,762 12/1962 Evans 317101 3,178,804 .4/1965 Ullery et al 317101 OTHER REFERENCES Conway: Electronic Engineering, Resistors for Deposited Circuit Techniques, November 1949.

KATHLEEN H. CLAFFY, Primary Examiner.

ROBERT H. ROSE, Examiner.

S. I. BOR, Assistant Examiner.

Claims (1)

1. IN A HEARING AID UNIT WHICH INCLUDES A MICROPHONE AND A RECEIVER MEANS, AN AMPLIFIER SECTION ELECTRONICALLY COUPLING SAID MICROPHONE TO SAID RECEIVER MEANS AND INCLUDING IN COMBINATION: A PANEL-LIKE SUBSTRATE MEMBER FORMED OF INSULATING MATERIAL; AT LEAST ONE TRANSISTOR MOUNTED ON SAID SUBSTRATE MEMBER; A PLURALITY OF RESISTANCES MOUNTED ON SAID SUBSTRATE MEMBER AS FILM-LIKE DEPOSITS; A PLURALITY OF CONDUCTORS INTERCONNECTING SAID TRANSISTOR AND SAID RESISTANCES AND MOUNTED ON SAID SUBSTRATE MEMBER AS FILM-LIKE DEPOSITS; AND A PLURALITY OF ELECTRICALLY CONDUCTIVE TABS FORMED OVER AT LEAST ONE OF SAID RESISTANCES AT SPACED POINTS THEREALONG AND ADJACENT TO AT LEAST ONE OF SAID CONDUCTORS, SAID TABS BEING ADAPTED TO BE SELECTIVELY COUPLED TO THE ADJACENT CONDUCTOR TO ADJUST TO THE VALUE OF SUCH RESISTANCE.

Images