US1836266A - Electric sound reproducer - Google Patents

Description

Dec. 15, 1931. w. s. MCCLINTOCK.JR 1,836,266

ELECTRI C SOUND REPRODUC ER Filed Dec. 26, 1929 2 Sheets-Sheet l hfZ/z'aw 37% flak/004A" I dd/1M. M W P Dec. 15, 1931. w. s. M CLINTOCKJR ELECTRIC SOUND REPRODUCER Filed Dec. 26, 1929 2 Sheets-Sheet Patented Dec. 15, 1 931 UNITED STATES PATENT OFFICE WILLIAM S. MCCLINTOO'K, JR, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE m ml- IPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF. ILLINOIS ELECTRIC SOUND REPRODUCEB Application filed December 26, 1929. Serial No. 416,317.

My invention relates to electric sound reproducers of the condenser or capacity speaker ty e.

Its chief object is to eliminate the necessity of operating the capacity speaker under a maintained high potential, while still retaining satisfactory performance.

As a practical advantage, my invention permits operation of the capacity reproducer without use of a high voltage. or example,

I may use only two or three dry cells. I may eliminate the more expensive and complicated high voltage batteries or rectifier and amplifier circuits.

While by no means restricted to such use, my invention is here shown as embodied in a one way oflice telephone system. In this system is a small transmitter including an operating switchto be placed in one room and a capacity speaker in the other, with a transformer and two or three dry cells located wherever convenient. This system as illustrated requires no additional source of potential and no amplification.

For the effective operation of capacity speakers it has heretofore been necessary to maintain an impressed basic high voltage of some 400 or 500 volts durin o eration. This has usually been accomplis e by a B battery or a filter circuit in the secondary or speaker circuit. Unless operated insuch a high voltage range, the operating characteristics'of the speaker have been too feeble to be practicable.

In my invention I avoid the necessity of operating under any maintained or impressed voltage on the speaker circuit. A Instead I condition the speaker for effective operation with impulses of ordinary strength, by shocking the speaker, which is preferably accomplished by momentary short circuiting of the primary. I prefer to use a circuit closing switch for the primary circuit which afl'ords an automatic, preliminary, momentary short circuiting or shunting of the primary around the transmitter.

Another feature of m invention is that this shocking of the spea erwith the closing of the 0 rating circuit gives a distinctive I audible signal serving as a preliminary warning that a message is about to be given. .Con-

versely, the operatin switch can be arranged to give a similar shoc u nits release, which provides a signal that t e message has been completed.

Other objects, features and advantages of my invention are set forth in the following specification and in the accompanying drawings, wherein:

Fig. 1 is a circuit diagram of a one way ofiice telephone system embodying my invention;

.Fig. 2 is a schematic view of the transmitter, transformer and battery, and capacity speaker units of the circuit of Fig. 1,;

Fig. 3 is an enlarged plan view, with portions broken away, of the capacity reproduoer element;

Fig. 4 is a detailed section taken on the line 4-4 of Fig. 3 showin' the attachment of-one of the lead-in wires, the dielectric and tinfoil bein omitted.

Fig. 5 is a similar detail section taken on line 55 of Fig. 3 showing the attachment of the other lead-in wire; and

Fig. dis a detail section taken on the line 6-6 of Fig. 3 showing the mounting of the condenser in its frame.

The oflice telephone system schematically shown in Figs. 1 and 2 comprises in neral a transmitter 10, a transformer and ttery housed in the case 41, and a capacity reproducer, which may be of the type shown in Kyle Patent 1,644,387. The details of the reproducer shown in detail in Figs. 3 to 6 inclusive include some variations in construction.

An operating switch conveniently housed in the handle of the transmitter and controlled by a thumb button is so arranged that immediately preliminary to closing the primary circuit through the transmitter, it shunts the circuit across the transmitter, thereby short-circuiting the primary and subjecting the secondary or speaker circuit toa momentary ock.

To describe the system in Referring to Figs. 1 and 2, 11. usual type of transmitter is provided with an electric circuit including conductors 11 and 12. The conductor 11 communicates with ablade 18 of greater detail a push button switch consisting of blades 13, 14 and 15 which yield when the button 16 is pushed down. An insulating block 17 spaces the blades 13 and 15. The conductor 12 leads to a contact 18 which is engaged by blade 15 when it is sufficiently depressed. A contact 19 on the blade 14 will be engaged by the blade 13 prior to the engagement of the blade 15 with the contact 18, so that the blade 14 is forced out of engagement with the contact 21 prior to the engagement of the blade 15 with the contact 18.

The conductorll and the blade 13 are connected with a conductor 22 which communicates with the primary winding of the transformer 24. The conductor 25 carrying the contact 21 is connected to a battery 26in practice preferably two or three dry cells which is connected with the opposite end of the primary winding 23 by a conductor 27. The switch blade 15 is connected to the conductor 25 by a conductor 28.

The secondary 29 of the transformer is connected by conductors 31 and 32 with the opposite plates 33 and 34 respectively of the reproducer 35. If desired, a spark gap 36 may be used to protect the reproducer from excessive voltages.

The switch mechanism may be incorporated in the handle portion 40 of the transmitter. The transformer and battery may be housed in a cabinet 41 having the conduct0rs22 and 25 connected to binding posts 43 and 44. The conductors 31 and 32 leading to the secondary 29 of the transformer are secured by binding posts 45 and 46 respectively.

The reproducer 35 consists preferably of a metal plate 34 perforated as at 48 and is corrugated as shown in Figs. 4 and5. A thin sheet of resilient rubber 49 is stretched over the plate 34 and its edges are wrapped around a cord 52 which is pressed into a marginal recess in the frame 51 to hold the rubber taut. The metal plate 34 is preferably slightly convexed to maintain a fairly uniform pressure of the rubber sheet against the perforated plate. The plate 34 of the condenser-reproducer is relatively rigid. To

provide suflicient relative flexibility of the plates, the upper plate 33 is formed of tinfoil or the like which is secured to the rubber sheet by a suitable adhesive.

The tinfoil plate 33, which forms the diaphragm of the reproducer, moves upon chargmg d discharging of the condenser in proportion to the frequency and strength of the sound waves transmitted. The plate 34 is referably' secured to the frame portion 51 by nails 53 passing through perforations around the edge thereof. A protecting moulding strip. 54 may be fixed by screws 55 on the frame over the edges of plate 34 as shown in Fig. 6.

The conductor 32 is electrically connected to the plate 33 by a binding post consistingof a bolt 56 passing throu h an over-size opening in the plate 34 and t rough washers 57 and 58 which engage the plate 32.

The conductor 31 is electrically connected with the plate 34 by a lead-in strip nailed between the frame and an edge of the plate (Fig. 4). i

If desired, a decorated paper cover or picture 61 may protect the delicate tinfoil plate 33 as indicated in Fig. 2. The reproducer may be hung by an eye 62 as shown, or may stand on a base.

In the normal operation of my system, the operator lifts the transmitter to his mouth by the handle'40, pressing the buttom 16. This initially engages the blade 13 with the contact 19 of the blade 14, thereby short circuiting the battery 26 through the primary 23 of the transformer, and gives the condenser-reproducer 35 a momentary shock. The shocking of the condenser-reproducer has the dual function of conditioning the reproducer and giving an audible signal that a message is to be given. The switch in the transmitter handle next disengages the blade 14 from the contact 21, breaking the momentary short circuit. Immediately thereafter the blade 15 engages the contact 18, placing the battery in series with the transmitter and the primary, which constitutes the normal speaking circuit.

For a two way or inter-communicating installation another system can be used with the reproducer of one and the transmitter of the other at the respective terminals. In such a system of course the person addressed can talk in reply, and also the party addressed, by merely pressing the button on his transmitter, can indicate to the other party that he is ready to receive the message without using the conventional Hello.

The conditioning of the capacity speaker by such a momentary shock is not permanent, but from my experiments it seems to last at least for a few hours. However, the automatic shocking of the reproducer prior to each communication always insures that the capacity reproducer is properly conditioned for operation. Such a conditioning of the reproducer is somewhat analogous to a molecular polarization of the rubber, even though it is of course a non-metallic substance. This analogy is further borne out by the cumulative effect of such shocking. With each additional shocking the effect becomes more lasting.

I believe from experiments I have conducted that the advantages of relying upon shocking of the reproducer to condition it for effective operation, instead of maintaining an impressed high voltage, is not only in eliminating the necessity for more elaborate means for maintaing such high voltage, but also that, in operating the capacity reproduc'er on a basic voltage of zero, a more favorable operating range results with greater sound wave producing power from the reproducer in proportion to the charge power.

While my invention has been described as adapted specifically to an ofiice telephone system and with one specific circuit illustrated, I contemplate that many other embodiments of my invention may be made in a radio re ceiving set without departing from the scope or spirit of my invention as set forth in the appended claims.

I claim:

1. The combination with a condenser-reproducer of means for momentarily abnormally electrically shockin the condenserreproducer to condition it or normal operation.

- 2. The combination with a condenser-reproducer and a receiving circuit therefor operating upon a basic voltage of zero, of means for abnormally electrically shocking the con- 'closable operating circuit therefor, which consists in subjecting the reproducer to a momentary electrical shocking preliminary to closing the circuit for normal operation.

5. A method of operating a condenser reproducer comprising condenser plates with a pliable resilient dielectric there-between, which consists in normally operating the circuit of the reproducer without a high basic voltage and from time to time subjecting the reproducer to an abnormdl electrical conditioning.

6. The combination of a condenser-reproducer comprising a pair of condenser plates and a rubber dielectric there-between, a secondary circuit for the reproducer, a primary coupled with the secondary, means for electrically impressing sound waves thereon, and means for momentarily subjecting the rimary to an abnormalcurrent for shockmg the condenser-reproducer to condition it for normal operation in the absence of an impressed high voltage.

7. In a device ofthe class described, tramsmitter means for converting sound waves into electrical waves, means comprising a densenreprfoducer for converting the ctric'al waves into sound waves, and means for producing an electrical shock in said re producer. 7

8. In a device of the class described, a transmitter, a condenser-reproducer therefor, a source of potential, normal operating circuits connecting the several parts of the device, and circuit closing means therefor,- causing said potential source to shock said reproducer. v

9. In a device of the class described, a transmitter, a condenser-reproducer, an electric circuit connecting said transmitter and reproducer, a source of electrical potential for said transmitter, circuit closing means for connecting said source in series with said transformer and comprising a portion adapt ed to momentarily shunt said transmitter prior to connecting it in series whereby a shock is transmitted to said reproducer.

10. In a device of the class described, a transmitter, a condenser-reproducer, an electric circuit connecting said transmitter and said reproducer, a source of electrical potential for said circuit, a potential transformer in the circuit between the transmitter and the reproducer, circuit closing means for connecting said source in series with said transmitter and the primary of said transformer, and means for momentarily short circuiting said source through the primary of said transformer.

11. The combination with a condenser reproducer of a normal operating circuit therefor, a switch for said circuit, and means actuated upon operation of the switch for first momentarily shocking the circuit for conditionin the condenser-reproducer.

12. n a device of the class described, a transmitter, a condenser-reproducer, an electric circuit connecting said transmitter and said reproducer, a source of electrical otential for said circuit, a potential trans ormer in the circuit between the transmitter and the reproducer, circuit closing means for connecting said source in series with said transmitter and the primary of said transformer, including a portion adapted to momentarily short circuit said source through the primary of said transformer upon actuation of said circuit closing means. v

13. In an acoustic device of the class described, a transmitter, a condenser-repro ducer, a reproducer charger in electrical series with said reproducer, a source of potential for said transmitter, circuit closing means for connecting said source in series with said transmitter and said charger, and means adapted to short circuit the source through the charger.

14. In an acoustic device of the class de scribed, a transmitter, a condenser-reproducer, a reproducer charger in electrical series with said reproducer, a source of potential for said transmitter, switch means for connecting and disconnecting said source in series with said transmitter and said charger, including a portion adapted to short circuit the source through the charger upon actuation of said switch.

15. A telephone system of the class described comprising a transmitter, a low voltage battery, a transformer, a circuit for the three, a switch for the circuit,-and a secondary circuit through the transformer, a condenser-reproducer in the secondary, and means for short circuiting the battery through the primary of the transformer for shocking the condenser-reproducer.

In witness whereof, I hereunto subscribe my name this 24th day of December,1929. W'ILLIAM S. M CLINTOCK, J R.

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