US2573438A - Electroacoustic transducer set - Google Patents

Description

Oct. 30, 1951 J. L. HATHAWAY ET AL ELECTROACOUSTIC TRNSDUCER SET 2 SHEETS- SHEET l Filed Sept. 18, 1946 Oct- 30, 1951 J. L. HATHAWAY z-:TAL

ELECTROACOUSTIC TRANSDUCER SET I2 SHEETS- SHEET 2 lll-Q72'.

Filed sept. 18, 1946 Patented Oct. 30, 1951 UNITED STATES PATENT OFFICE ELECTROACOUSTIC TRANSDUCER SET Jarrett L. Hathaway, Manhasset, and William Hotine, Bayville, N. Y., assignors to Radio Corporation of America, a corporation of Delaware Application September 18, 1946, Serial N o. 697,666

(Cl. Z50-14) 6 Claims. 1

This invention relates to extremely small, compact and lightweight electro-acoustic transducer sets capable of being worn on the person.

A specific application of this invention is in the field of vest pocket type radio receivers, although features of the invention are applicable to apparatus for aiding persons who have difficulty in hearing. When the invention is used in connection with a radio receiver, the receiving unit may either be carried in a pocket of the wearer or strapped about the waist or suspended from the shoulder of the wearer.

Hitherto, the small portable radio receiving sets designed for carriage on the person have suffered from one. or more of the following disadvantages: Bulkiness, excessive weight, lack of stability, and insuilicient battery life for the required sensitivity.

The present invention overcomes these diiculties and provides an extremely small and lightweight radio receiver set capable of being worn on the person and one which possesses sufficient sensitivity for satisfactory reception for many hours of continuous operation.

An important feature of the invention is the extremely lightweight and very thin iiexible tubing and associated ear attachment for transferring sound from the transducer located in the housing carried on the person to the ear of the wearer. Where this feature is employed in a radio receiver, the iiexible tubing may serve the additional purpose of an enclosure for a thin antenna wire.

Another feature of the invention is the use of a. metallic housing or casing for the radio receiving apparatus in conjunction with a carrying belt of such character as to increase the overall effective length of the antenna.

One embodiment of the invention is a radio receiver of the vest pocket type, which is contained in a housing, and comprises a battery type built-in power supply, a signal rectifying and amplifying system, and an electro-acoustic transducer. Extending from this housing and coupled to the transducer is a thin-walled flexible tub-e conducting sound waves from the transducer to a small ear plug which may be fitted into the ear. Av radio antenna wire is inserted within the thin-walled exible sound conveying tube. By way of example only, we have found that a small diameter Vinylite hollow tube can be used with very satisfactory results.

This entire unit is extremely small, compact and of lightweight and can easily fit into a pocket of the wearer. Ii desired, the housing may be provided with loops for enabling a carrying strap to be inserted through the loops, thus permittingthe set to be carried by the wearer. If a strap is employed, it is preferred that this strap include a wire or some conducting material extending for the length of the strap and which, by coupling to the housing of the radio receiver, will effectively increase the overall length of the antenna.

Another embodiment of the radio receiver is a hearing aid having a compact, small and lightweight housing containing therein a suitable microphone, an audio amplifier and a transducer. Here again, as in a radio receiver embodiment, there is employed a thin-walled exible tube for conducting sound waves from the transducer to a small ear plug which may be tted into the ear.

A more detailed description of the invention follows in conjunction with a drawing, wherein:

Fig. l diagrammatically shows, in box form, a radio receiver of the present invention;

Fig. 2 is a detailed circuit diagram of the receiver of Fig. l;

Fig. 3a and 3b respectively show exploded and assembled views of the flexible sound conveying tube in association with an ear plug at one end and the telephone electro-acoustic receiver at the other end;

Fig. 4 is a perspective view of the complete vest pocket type of radio receiver of the invention;

Fig. 5 diagrammatically shows, in box form, the invention as applied to a hearing aid type of apparatus;

Fig. 6 shows the iiexible sound conveyingI tube feature of the invention in association with a standard telephone plug at one end and a small ear plug at the other end.

Throughout the iigures of the drawing the same parts are represented by the same reference numerals.

Referring to Fig. l of the drawing in more detail, the radio receiver of the invention comprises a casing represented here by a dashed rectangle 2 containing therein a radio frequency vacuum tube amplier 4, a detector 6 coupled to the output of the radio receiver amplifier, an audio frequency vacuum tube amplifier 8 following the detector 6, and an electro-acoustic transducer I coupled to the output of the audio amplifier 8. A, B and C batteries, represented diagrammatically by the box I8, supply polarized potentials Via leads and 'I to the amplifiers d and 3, respectively. CasingI 2 is preferably made of metal although, if desired, a suitable molded plastic material can be used. An input antenna I6 in the form of a Wire is connected at one end to the input of the radio frequency ampliner 4, and eX- tends for the major portion of its length through the interior of a exible plastic thin-walled small diameter tube I2. The tube I2 has the appearance of a thin piece of spaghetti and is coupled at one end to the transducer It and coupled at its other end to an ear plug i4. The manner in which the tube I2 may bey joinedto thetransducer II] and the ear plug I 4 will be described in more detail later in connection with the description of Figs. 3a and 3b. a a a I By reference to the schematic circuit diagram amplifier comprises a pentode vacuum tube 4 having a parallel tuned input circuit LI, CI, and a parallel tuned output circuit L2, C2. A condenser C6 couples the output of the radio frequency amplier 4 to a detector circuit `6 comprising a pair of dry rectiers XI and X2 arranged as a voltage doubler. These rectiers may be crystal detectors, or germanium rectiiier units, silicon rectiers, or any suitable type. Although they have been shown as dry rectiers, it will be obvious that, if desired, they may be replaced by a vacuum tube type of rectifier, in a manner well known tov those skilled in the art. The output of the rectifier 6 is utilized to supply the AGC voltage to the grid of tube 4 by way of a resistor R3. Rectifier 6 also furnishes an audio voltage via condenser CI to the audio amplifier 8, which is approximately double that of a single rectifier. The output of the audio amplifier 8 is coupled to a suitable audio transformer T whose secondary winding is coupled to an electro-acoustic trans-4 ducer I0.

Transducer unit I0 is shown as a telephone receiver having a pair of coils wound around the poles of a permanent magnet P and connected in series to theY secondary winding of the audio transformer. The diaphragm is located immediately above the coils of the telephone receiver and responds to variations in current through the coils of the transducer. A cap C having a suitable aperture centrally located therein closes the transducer unit. This central aperture in the cap C communicates with the interior of the thin spaghetti-like plastic tube I2. The opening at the other end of the tube I2 communicates with the interior of the ear plu-g I4, thus conveying sound waves from the transducer unit I0 through the interior of the plastic tube I2, to the ear of the wearer in which the ear plug I4 is inserted.

The antenna of the radio frequency receiver is a thin wire I6 which extends for the major portion of its length within the plastic tube I2. Although in Figs. 1 and 2 the wire I6 appears as though the major portion of its length were outside the plastic tube I2, it should be understood that these showings are merely diagrammatic and that a more accurate showing appears in Fig. 4, which shows the perspective View of a radio receiver actually constructed in accordance with the invention, and tested with highly satisfactory results.

In one embodiment of the invention., suQQQSS:

4 fully tried out and practiced, the radio frequency amplifier 4, was an RCA 1L4 miniature tube, arnplier 8 was an RCA 3Q4 miniature tube, while rectiers XI and X2 were germanium rectiiier' units. The A battery for the filaments of the two tubes was 11/2 Volts and connected to an on-oif switch SW. The C battery was 21/2 Volts, while the B battery was 45 volts. The A battery was a small cylindrical hash-light type, while the B and C battery was a dry battery type of rectangular configuration. The plastic spaghetti type of tube was anvinyl plastic tubingaboutthree feet long and having an inside diameter of .060, inch. The thickness of the vinyl tubing WasLOZinch. rlhe dimensions of the receiver casing and the locations of the elements viewable from the outside of the housing are generally shown in Fig. 4. For

V tuning the inputandoutput circuits of the radio Aand 3` on the top of the housing for enabling a screw driver to be inserted for changing the valuesof the variable condensers CI and C2. The of Fig. 2, it will be seen that the radio frequency A antenna wire I6 had a diameter of .003 inch and was especially small toe-.prevent any undue antenuaton of the sound waves passing through the tube I2 from the transducer to the ear plug. "It will thus be seen that although the tube yI2 had an inside diameter of approximately'l/l of an inch, the diameter of the antenna wire was considerably smaller in size so that it occupied relatively little space Within the tubing. a ,Y

The casing 2 was made of metal and had a rectangular shape adapted to iit into the pocket of a wearer. The on-and-oif SW switch was located at the-top, as well as the plastic tubeI2, and the control holes I and 3. The casing 2' had a cover 2 at the bottom which could be removed quicklyl and easily for the replacement of batteries; The batteries were slid into the bottom of theV casing 2' and required no wire connections, inasmuch as reliance was had on `contact springs withinthle' case which engaged the battery terminals. `4 a The metallic casing 2 was also provided with metallic belt loops 'I through which a belt 9 could be inserted for supporting the receiver, either from the shoulder or from the Waist of the wearer; The belt 9' is shown ashaving embodied therein a wire II for association with metallic snap fastener elements I3 and I5. Elements I5 are mounted on the metallic casing 2'. The metallic wire I I in the belt 9 serves to increase the overall eifective length of the antenna. If desired, the snap fastening elements I3 and I5 may be eliminated entirely, and the same result obtained by virtue of capacitycoupling between wire II and the metallic casing 2 when the belt is inserted through the loops 'I, 1 and worn on the wearer.v The ear plug I4 was made of soft rubber and had an overall length of slightly less than 1X2 inch and a maximum width ofv about 5A; of an inch. These extremely s mall dimensions enable the ear plug to be almost completely hidden from view when inserted into the ear.

The weight of the entire receiving unit of Fig. 4, without the carrying strap 9, was 24 oz. weight of the carrying strap was 11/2 oz. The weight of the soft rubber ear plug I4 was about An embodiment of Fig. 4 was actually tried outy in practice in a television studio for receiving in-k structions from a small radio transmitter operating at a frequency of 27:32 megacycles. 'Ifhe maximum output from the audio transformer T' was of the order of 50 milliwatts. n It will be understood, of course, that the invention is not iimitedft this particular freduency, or to this' order of output since other frequencies may be used'ancl other outputs obtained', depending upon the types of tubes and circuits employed.

The manner in which the spaghetti-like plastic sound conveying tubing I2 is connected to its terminal fittings is shown in detail in Figs. 3a and 3b. One end of the tube I2, for example the left hand end, is pushed (by stretching it) over the tapered end of a sleeve Il whose other end is threaded into the interior of the cap C of the telephone receiver I0. Once the end of tube I2 is pushed on the tapered end of the sleeve I l, it will remain rmly joined to this end by friction. kThe other end of tube I2, the right hand end, is similarly pushed (by stretching it) over the tapered end of sleeve I 9 and remains fixed and is held on the sleeve by friction. If desired', a suitable cement may be used to insure a tight and permanent nt between the ends of the plastic tubing and the sleeves II and I9. The other end of sleeve I9 is provided with a flange 2l which is pushed into the bore of the rubber ear plug I4 and is retained therein. It will thus be seen that the ear plug is readily replaceable quickly and easily, which is an important feature for sanitary reasons especially when the unit is to be used by different persons. While Fig. 3a shows an exploded view of the cap C, sleeve I'I, tube I2, sleeve I9, and ear plug I4, Fig. 3b shows how these nt together. In the embodiment actually constructed and satisfactorily tried out in practice, the sleeves I 'I and I9 were made of brass, although it should be understood that, if desired, a suitable molded plastic material may also be used.

Fig. 5 shows diagrammatically how the invention may be used in connection with a hearing aid type of apparatus to be carried on the person. In Fig. 5 the hearing aid is shown as a suitable housing represented by the rectangle 2 containing a microphone M, an audio amplier 8, an electro-acoustic transducer I0 and suitable batteries I8. If the microphone M is of the carbon type it will require a connection to the batteries I3 in which case there will be provided a connection shown by the dashed line 23 suitably coupled to the elements in a manner Well known to those skilled in the art. The output of the electroacoustic transducer I0 which will be a telephone receiver, is conveyed by a thin walled flexible plastic tube I2 to the ear plug I4.

Fig. 6 is a mechanical assemblage which shows how the plastic tubing I2 and its terminal fittings can be carried as a complete plug-in type unit.

One end of the plastic tube I2 is connected to the soft rubber ear plug I4, while the other end of the plastic tubing is connected Via sleeve l1 and suitable apparatus within a housing 2' to a telephone plug 24. This plug 24 is adapted to be inserted into the audio output jack of any suitable audio circuit. This audio circuit, may, for example, be the audio output circuit of a radio receiver, or a telephone line, or a stationary or portable hearing aid. The housing 2' contains in its interior a suitable audio transformer 25, whose terminals are connected to the tip and sleeve of plug 24 and tc the electro-acoustic transducer unit I Il. The audio transformer 25 is a stepdown transformer and provides a suitable change in impedance between the telephone plug end of the circuit and the earphone transducer unit I0. The sponge rubber insert 26 serves the dual purpose of insulating the metallic casing of the audio transformer from the telephone plug terminals and mechanically stabilizing the audio transformer. The telephone receiver I0 is provided with the usual cap C having a centrally threaded aperture which communicates with the interior of the sleeve I'I associated with one end of the plastic tube l2. Suitable end plugs 2'I and 28'serve to hold the elements within the housing 2.

What is claimed is:

l. In a radio receiver, an electro-acoustic transducer for producing sound waves, and means for conveying said sound waves to the ear of a person, said means including a flexible hollow tube having one hollow end communicating with said transducenand a small hollow ear plug cornmunicating with the other end of said flexible hollow tube, and an antenna wire within said flexible hollow tube and coupled to said receiver.

2. A receiver having a length of spaghetti-like flexible tubing having one hollow end in sound transfer relation to an earphone, an ear plug in sound transfer relation to the other end of said flexible tubing, and a thin antenna wire located in the interior of said tubing and coupled to said receiver.

3. In combination, a radio receiver comprising an electro-acoustic transducer, a lightweight flexible hollow tube having one hollow end in sound transfer relation with said transducer, an ear plug in sound transfer relation with the other hollow end of said flexible hollow tube, an antenna wire located within said flexible hollow tube and coupled to the input of said radio receiver.

4. Means for conveying sound waves from an earphone having a closure provided with a threaded aperture, comprising a relatively long hollow exible lightweight spaghetti-like thinwalled tubing, a rigid hollow sleeve substantially entirely concealed by said tubing and having a threaded end for association with said threaded aperture and a tapered end for accommodating one end of said tubing, another rigid hollow sleeve substantially entirely concealed by said tubing and having a tapered end for accommodating the other end of said tubing, a soft lightweight rubber-like ear plug sufciently small to be concealed within the ear of a person and having a bore therein and a wider diameter hole along one portion of said bore, said last rigid sleeve also having a flange for accommodation in said wider diameter hole of said ear plug for holding said ear plug in position on said last sleeve.

5. For use with the audio output of a communication system, a telephone plug having tip and sleeve terminals, an audio transformer coupled to said terminals, an earphone type of electro-acoustic transducer coupled to the output of said transformer, a thin-walled lightweight hollow ilexible spaghetti-like tubing, inconspicuously small rigid hollow sleeve substantially concealed by the ends of said tubing, a lightweight ear plug sufliciently small to be concealed within the ear of a person and having a bore therein for association with one of said sleeves, and means for linking the other sleeve to said transducer in sound transfer relation.

6. Means for conveying sound waves from an earphone having a closure provided with a threaded aperture, comprising a relatively long hollow flexible lightweight spaghetti-like thinwalled tubing, a rigid hollow sleeve having a threaded end for association with said threaded aperture and a tapered end for accommodating one end of said tubing, another rigid hollow sleeve having a tapered end for 'accommodating the other end of said tubing, a soft lightweight rubber-like ear plug suficiently small to be concealed within the ear of a person and having a. bore therein and a Wider diameter hole along one portion of said bore, said last rigid sleeve also having a flange for accommodation in said wider diameter hole of said ear plug for holding said ear plug in position on said last sleeve.

` JARRETT L. I-IATHAWAY.

WILLIAM HOTINE.

REFERENCES CITED UNITED STATES PATENTS Name Date Pape Oct. 3, 1905 Number awmsa Number Name Date l Williams Jan. 15, 1918 Cherry Mar. 11, 1919 Williams May 30, 1922 Doble June 9, 1925 Summer Apr. 20, 1926 Hahnemann Apr. 20, 1926 Lodge Mar. 27, 1930 Rath June 24, 1930 Kelley Aug. 7, 1934 Bedell Jan. 8, 1935 Minton Oct. 22, 1935 Mashbir Dec. 7, 1937 Morey May 23, 1939 Mitchell Oct. 13, 1942 Olson Nov. 28, 1944 Striker June 19, 1945 Thibos Apr. 22, 1947 Kelsey Nov. 4, 1947

Images