US1660321A - Electrical sound-producing apparatus - Google Patents

Description

Feb. 28, 1928. 7 1,660,321

- T- BODDE ELECTRICAL SOUND PRODUCING APPARATUS Original Filed Aug. 1, 1923 MILLI- AMPERES GAUSSS INVENTOR Theodore Bocld e BY A ATTORNEY v.

coil surrounding .current pulsations or impulses by .into corresponding Patented Feb. 28, 1928.

THEODORE BODDE, OF LEWISTON, NEW YORK.

ELECTRICAL SOUND-PRODUCING- APPARATUS.

Application filed August 1, 1923,

This invention relates to an apparatus for electrically producing sound, and more particularly to an apparatus for transforming sound waves or impulses into corresponding the action of an electron discharge tube or valve; and has special reference to an improved apparatus of the nature disclosed in my copending application Serial No. 613,273, filed Jan. 17, 1923.

As described in my said copending application, it is known that the electron stream or current between the electrodes of a vacuum tube or electron discharge valve maybe controlled by means of a magnetic field. In the action of these magnetically controlled valves if a constant voltage is impressed between the cathode and anode, the current that flows through the tube, that is, the electron stream that discharges from the cathode and impinges on the anode, while unaffected by a magnetic field having a strength less than a critical value, is reduced to zero if the magnetic field is increased beyond that value; and thus by changing the strength of the magnetic field to magnitudes below or above a critical amount, the current across the electrodes and hence the current in a Working circuit connected to the electrodes may be respectively established or extinguished. I have discovered that this phenomenon or property of magnetic control of the electron emission of the tube or valve may be utilized for effecting the transformation of sound vibrations or impulses electrical impulses for sound production and transmission; and that the tube or valve may be so constructedor designed as to permit of accomplishing this result. p

The magnetically controlled electron tube, or magnetron as it is termed, in one of its most efiicient forms comprises a vacuous vessel of cylindrical configuration provided with an axially disposed filament which when heated to incandescence emits an electron stream which impinges upon a cylindrical plateor anode symmetric-ally surrounding the cathode, the stream being controlled'by means of a magnetic field preferably produced by an energized-solenoid or the tube Or vessel. The paths of movement of the electron projected from the cathode are found to be influenced by the magnetic field, the paths being bent Serial No. 655,005. Renewed April 21, 1927.

or curved by. the magnetic field,-the degree of curvature imparted to the paths var ing with the strength of the magnetic eld When the magnetic field is below a critical value, the electron paths although curved still intersect the cylindrical anode, and since the electrons impinge on the electrons the anode, :the current through the tube remains unaffield of electrons bei-'.g then less than the radius of the cylindrical anode, electrons do not impinge on the anode, no current flows across the electrodes and the i and since the current in the working circuit is accordingly extingulshed.

When the parts ruptly changed rom the maximum to zero of the magnetron are symmetrlcally arran ed, the" current may beab-.

value, the transition from a closed to an open circuit bein however not abrupt where there isa lack 0 symmetry. I have discov-- ered that when the magnetron is subjected" to mechanical vibrations, a relative vibration between the cathode and the anode is roduced, the cathode or filament, due to its inertia, remaining suspended in space sta' tionary with respect to the vibrating anode, and as a result not only "is adis-symmetry produced which changes or variations in the electron stream when the magnetic field is at or about the critical point, but when the magnetron construction is modified as will appear hereinpermits of more gradualafter, variations in the current in the work- I mg circuit are obtainablecorresponding 1n magnitude and frequency to the vibrations to which the tube is subjected, the magnetron being'thus rendered serviceable and adaptable for translating sound vibrations into sound producing electrical pulsations.

As heretofore mentioned, the electron stream is controlled. by a certain critical value of the magnetic field voltage is impressed upon the magnetron electrodes.- It. is known "that the critical value of a given magnetron varies with and proportional to the square root of the voltage impressed upon the electrodes. foundthat in the operation of the sound producing apparatus variationstake place in the working circuit thereof, which variations produce "changes in the voltage im- .100 if a constant e pressed upon the magnetron electrodes especially When said working circuit possesses high inductance and resistance factors, and in order to produce a pure and strongiconversion of the mechanical vibrations into electrical impulses, it is highly desirable to compensate for the changes in the impressed voltage. It is accordingly a principal object of my present invention to provide an improved sound producing apparatus of this nature in which the voltage variations or fluctuations are compensated for so that the activit of the apparatus is made independent of changes in the critical value of the magnetron.

To the accomplishment of the foregoing and such other objects as may hereinafter appear, my invention consists in the elements and their relation one to the other, as hereinafter particularly described and sought to be defined in the claims, reference bein had to the accompanying drawings whie show referred embodiments of my invention, and in which:

Fig. 1 is a view showing my invention applied to a transmitter,

Fig. 2 is a diagrammatic view of a modification of my invention,

Fi 3 is a graphical view showing the electrica characteristics of the magnetron and the manner of adjusting the magnetic field thereof, Y

Figs. 4 and 5 are diagrammatic views depictingthe principles or theory underlying the invention, and

Fig. 6 is a modification of the construction of the magnetron device which maybe employed.

Referring now more in detail to the drawings and more artieularly to Fig. 1 thereof, the magnetical y control ed valve'or magnetron generally designated as M is shown to comprise a vacuous vessel or tube 10 provided with the cathode in the form of a straight filament 11 arranged axiall of the tube, and an anode 12, the said ano e in the invention here exemplified comprising a sectionor portion of a surface of a cylinder as will be detailed hereinafter, the filament being provided with the sealed terminals 13 and 14 and the anodebeing provided with the sealed terminal 15; and encircling the tube 10 symmetricall with the cathode and anode there is provi ed the solenoid 16 for producing a controlling magnetic field.

For heating the filament to incandescenee a closed circuit is provided. which includes the battery 17, the op osite poles of which are connected to the lament terminals 13 and 14; by means of the conductors 18 and 19. As is well known, upon heating the filament 11 by means of-this closed circuit, there will take place an emission of electrons from the filament 11 to the anode 12, and upon closing a Working circuit connected to the anodeand cathode a current will be established therethrough.

For energizing the solenoid 16 the same may be connected to a source of current which may be the battery 17 by means of a circuit comprising the conductor 20, the coil of the solenoid 16, conductor 21, and rheostat 22, the rheostat being employed for predetermining the degree of energization of the solenoid and hence the magnitude of the magnetic field thereof.

As above mentioned, it the electron tube be subjected to a magnetic field below a predetermined amount, the emission of electrons from the cathode and the impinging of these electrons on the anode of the tube will be uninterrupted and unhindered, and that if the tube be subjected to a magnetic field beyond such predetermined amount, the electrons will be diverted and prevented from reaching the anode, resulting in an opening of the tube circuit and the opening of the working circuit controlled thereby. The graphical representation of this phenomenon is shown in Fig. 3, in which the strength of the magnetic field is represented by the abscissze, and the strength of the current flowing between the cathode and anode is represented by the ordinates of the graph. If the magnetizing influence is less than the line represented as CD, the current in the workin circuit will be a maximum represented by the line XC. If, however, the magnetization passes the point D, the current in the Working circuit decreases and rapidly diminishes to a minimum as the magnetic field approaches the value XE, the chan e along the curve DE being more or less abrupt as the parts of the magnetron are more or less symmetrical in arrangement.

For the purpose of transforming vibrations such as sound vibrations into corresponding electrical pulsations, the magnetron of my present invention is mounted on a vibratable member which may be set into vibration in accordance with sound Waves impinging thereon, the said vibratable member comprising for example a sounding board or a diaphragm of a transmitter. This is shown for example in Fig. 1 of the drawings, and referring to this figure, the magnetron is shown mounted for movement with a diaphragm 23 associated with the mouth-piece 24, the magnetron being referably bodily mounted on and carried y the diaphragm 23 by means of the sup porting element 25. Also preferably in order to minimize the weight carried by the diaphragm 23, the tube 10 alone is mounted thereon, the solenoid 16 being arranged so as to be maintained in a relatively stationary condition during vibration of the tube. With this construction as the diaphragm and the tube are set into vibratory motion, the anode 12 is moved relatively to the cathode or filament 11, the latter remaining suspended in stationary position due to its inertia. In order to heighten this inertia effect, the cathode 11 may be weighted at its ends as by means of the small weights 26, 26. When the tube isset into vibratory motion and when the solenoid 16 is energized to produce a magnetic field at or about the critical value, the relative vibration between the anode and the cathode effects variations in the electron stream reaching the anode, which variations are proportional in magnitude or amplitude and frequency to the oscillations or vibrations impressed upon the tube. By connecting across the electrodes a receiving circuit which may include the receiver 27, the transformer 28, the battery 29 and conductors 30 and 31, it will be apparent that the variations in the electron stream will produce corresponding sound producing variations in the current of the working or receiving circuit.

That the change in the electric current or stream varies proportionally with the impressed mechanical vibrations of the tube system will appear from a consideration of Figs. 3 to 5 of the drawings. In these figures I have attempted to depict in a diagrammatic fashion the underlying theory of the invention, and I desire it to be understood' that although this theory I believe to be properly explanatory of the phenomenon or the behaviour of the apparatus, the theory is presented by way of explanation only, and not by way of limitation. When the magnetic field active on the magnetron is of a magnitude equal to the critical value of the tube as represented for example by the asterisk on the curve represented in Fig. 3, the current in the'tube is at the transition point, and the average electron path may be represented by the curve a: (Fig. 4), the electron path being tangent to the anode 12. This, however, is only the average path, and due to such factors as the physical dimension of the filament, the lack of complete symmetry of the parts, etc, the electrons are rojected from the cathode in a plurality o proximate paths such for'example as the paths :1), y and 2, the electrons in the path a impinging on the anode, and the electrons in the path y circling about in a closed path, as shown, without touching the anode. When the tube is vibrated, however, more or less of the electrons reach the anode according to the position of the tube and attached anode with respect to the relatively stationary cathode. This is shown in Fig. 5 of the drawings, wherein the diaphragm 23, tube 10 and anode 12 are shown in three successive positions F, G and H, the anode in position 12 embracing the electron paths m, y and z, the anode position 12 embracing the paths w and z, and the anode in position 12embracing only the anode,

path a. It will therefore be evident that the total electron stream emanating from the filament and impinging against the cylindrical anode surface varies progressively with and in proportion to the vibratory motion of the tube.

In the construction shown in Fig. 1 and diagrammatically indicated in Figs. 3 to 5, the anode 12 is a section or a part of a cylinder, and more particularly a cylinder with one side cut away, and the preferred form comprises a quadrant of a cylinder. The cylindrical anode as distinguished from the known ma-gnetrons is cut away on one side for the reason that if a full cylinder be employed any variation in the electron current on one side produced by the vibrations would be neutralized by an equal and opposite variation on the opposite side, producing a net result of no variations in the working circuit. With one side' of the however, removed, the electron stream variations on one side of the cylinder produce a current in the working circuit as desired. The same results may be accomplished by utilizing a complete cylindrical anode, however, and by eccentrically arranging the anode and cathode as will be detailedfurther hereinafter.

As already mentioned, a desideratum of the present invention comprehends the provision of an improved sound producing apparatus in which the voltage variations in the receiver circuit are compensated for so as to render the operation of the device independent of changes in the critical value of the magnetron, directly proportional to the square root of the voltage between the cathode and the anode. To accomplish the desired result, I provide means for producing variations in the magnetic field which controls the magnetron proportional to the changes in the critical value of the magnetron due to the variations in the receiver circuit, and with such means I maintain substantially the same relative proportion between the magnitude of the active or controlling magnetic field and the square root of the voltage effective across the electrodes. The means I prefer to provide for effecting the desired compensation comprises a circuit including a magnetizing coil 32 surrounding the mag netron tube to produce a magnetic field which is combined with the magnetic field of the coil 16, both fields producing a resultant controlling field having a. magnitude which maintains the magnetron at its critical point, the said circuit further including the conductor 33, the resistance 34 in shunt with a condenser 35, the rheostat 36 and the 37, the parts of the circuit beconductor ing connected across the anode and cathode as shown in Fig. 1. The resistance, inductance and capac ty quantities in this circuit this critical value being are preferably so predetermined as torender the circuit non-inductive, so that changes in this circuit due to changes in the voltage across the magnetron electrodes will be instantaneously 'efifected.

In the preferred construction, the magnitude of the magnetic field produced by the coil 32 is made about equal to the magnitude of the field producedby the coil 16, the resultant of these fields being regulated to be equal to the critical value of the magnetron. With this construction it will be seen that half of the magnetic field is proportional to the voltage between the cathode and the anode, and the other half of the magnetic field is maintained constant, this as will presently appear, producing a total magnetic field which at all times is proportional to the square root of the voltage between the a cathode and anode, making the high tension current passing through the magnetron independent ofinstantaneous voltage variations between the cathode and anode, which variations are the result of resistance and inductance changes in the receiver circuits due to such causes, for example, as the change in frequency of the circuit during the operation thereof, especially when the resistances and inductances .are of very large magnitudes. That the coils l6 and 32 will produce together a. total magnetic field which is at all times proportional to the square root of the voltage between the cathode and anode. may be seen from the following example, Assuming a voltage variation' of 4%, as for example a change in voltage across the electrodes from 100 to 104 volts, when the magnetic fields of the coils- 16 and 32 are equal, the coil 16 producesa constant magnetic field having a value say of 50, and the coil 32 then hasa value which will change from to 52 so that the total resultant field varies from 100 to 102; therefore have the following: Rgs ultant field 100 102 11 f tr a! Volta e c anges mm #1009 104 a change from 10.0000 to 10.0019 (5r 1/50th of 1% which change is infinitesimal, the ratio thus IBIHZIIIIIIIO constant in all substantial respects. Tius with these assumed values, the magnetron will not be afi'ecte'd by the voltage variation, and the sound producing apparatus is rendered dependent only on the mechanical'vibrations.

, Referring now to the modification shown in FigLQ of the drawings, in'which the parts ,are'shown diagrammatically and the magetizing coils dissociatedfrom the magnetron "tube for'purposes of clarity, the means for com ensatin for volta e variations com P g e "prises a circuit connected in parallel with the receiver 27' without includingthe high the said circuit includand the conductor 33'.

denser 35', rheostat 36 connected across the receiver 27 by means of the conductor 37', It has been found that the receiver 27' is the main cause'of the instantaneous voltage variations due to the resistance and inductance thereof so that these voltage variations will produce corresponding instantaneous current variations in the coil 32, resulting in corresponding instantaneous field variations. The field roduced by the coil 32 in this case should be in opposition tothat produced by the coil 16, the latter coil producing by itself preferably an extinguishing field pensating' coil 32 having a value such as to and the comkeep constant the proportion between the resultant field and the square root of the voltage. As the circuit of the coil 32' is connected directly between the two ends where the variations of this voltage occur, it can easily be regulated b means of the rheostat 36' so as to respon in the right proportionvto these variations. The remaining parts of the arrangement shown in Fig. 2

are similar to those shown in Fig. 1, and are designated by similar and primed reference characters.

Referring now to Fig. 6 of the drawings, I show a diagrammatic modification of'the magnetron in which a'full cylindrical anode 12 is employed in the tube 10, the filament 11 being arranged eccentrically relatively to the anode "12, the center of the anode being represented as c, the tube 10 being fitted to a diaphragm 23, with the arrangement such that the diaphragm is placed perpendicularly to the center line MN which passes through both centers 11' and a.

With this arrangement it will be seen that -11 represents the boundary of the electron field produced by the desired magnitude of the magnetic field.

The use and'operation of the will in the main be fully apparent 0111 the above detailed dGSCIiPtlOH- thereof. It will be further apparent that although I have shown my invention applied on a diaparatus phragm or sounding board'directly responsive to sound such as speech to, electrically produce sound proddcing variations in an electric circuit, this applicationof the invention has been given merely byway of example, and that otherapplications will be "obvious to those skilled in the m For example, the magnetron may be subjected" to vibrations of a mechanical vibrating sys-- controlling magnetic means for producing an electron discharge 'tem such as are employed in phonograph sound regroduction for the transmission of.

speech. t will be further seen that with the provision of the apparatus extremely sensitive and pure transmitter is obtained which in addition is entirely free from unavoidable secondary current changes which occur in known transmitters.

While I have shown my device in the preferred forms, it will be obvious that many changes and modifications may be made in the structure disclosed without departing from the spirit of the following claims.

I claim: v H

1. In combination, an electron discharge device having a cathode, an anode an a means for producing an electron discharge [controlling magnetic field, a circuit connected to the cathode and anode, and means for changing the magnitude of said magnetic field proportionate to changes in the critical valueof the electron discharge device due to variations in said circuit.

2. In combination, an. electron discharge device having a cathode, an anode and a means for producing an electron discharge field, a receiver circuit connected to the cathode and anode, and means for compensating forffluctuations in the voltage active across the, cathode and anode due .to variations in said receiver 'circuit.

3. In combination, device having a cathode,

an electron discharge an anode and a controlling magnetic field, avreceiver circuit connected to the cathode and anode, said circuit including a source of energy, and means the same relafor maintaining substantially tive proportions between the magnitude of the said magnetic field and the square root of the voltage active across the cathode and anode.

'4. In combination, an electron discharge device having a cathode, an anode and a means for producing an electron discharge controlling magnetic field, means for effecting vibrations of the device to produce vari ations in the electron stream impinging on the anode, a receiver circuit connected to the cathode and anode, and means for changing the magnitude of said magnetic field proportionate to changes in the critical value of the electron discharge device due to variations in said receiver circuit.

5. Incombination, an electron discharge device having a cathode, an anode and a means for producing an electron discharge controlling magnetic field which is at or about the critical value of the device, a receiver circuit connected to the cathode and anode, and means for changing the magnitude of said magnetic field proportionate to *5 changes in the critical value of the electron described an controlling magnetic the invention defined in f cuit.

means for producing discharge device due to variations in said receiver circuit.

.6. In combinatiom-an electron discharge device having a cathode, ananode' and a means for producing an electron discharge connected to the cathode and ano means for changing the magnitude 0% said magnetic field propch'tionate to changes in the critical value of the electron discharge de and field, a receiver; circuit device due to variations in said receiver circuit. I

7. An apparatus for producing sound by variations of an electrical current comprising anelement. vibratable in response to sound impulses, vice vibrated thereby, a receiver circuit connected to and controlled by the electron discharge device, and means for compensating 'for fluctuations in the voltage active across the electrodes of vice due'to varrtions in said receiver cir- 8. device havmg a cathode, an anode and a means for producing an electron discharge controll ng magnetic field, a receiver circuit an. electron discharge de-- In combination, an electron discharge the electron discharge deconnected to the cathode and anode, means for producing a second magnetic field cooperating with the first magnetic field to produce a resultant at or aboutthe critical value ofthe electron discharge device, and means for changing the magnitude of said resultant magnetic field proportionate to changes in the critical value of the electron discharge device due to variations in said receiver circuit. Y 9, In combination, an electron discharge device having a cathode,

an electron discharge controlling magnetic field, a receiver circuit connected'to the cathode and anode, means for producing a second magnetic field cooperating with the first magnetic field to produce a resultant magnetic field, and means for changing the magnitude of said resultant magnetic changes in the critical value of the electron discharge device due to variations in the receiver circuit.

10. In combination, an electron discharge device having a cathode, an anode, and a means for producing an electron discharge field proportionate to v I field, the said duce changes sultant magnetic", field proportionate to changes the critical value of the magducing a ma connected to t inductive circuit connected to said receiver 7 circuit, the non-inductive circuit includ ng magnetic a"'means for producing a second.

non-inductive circuit connected to the receiver circuit as in the magnitude of being so to prothe renetron;

p as

- the former and connected to the cathode a means for 1 to changes in the bration of the same 12; In combination, a magnetron having an anode, a cathode and a means for pro ducing a magnetic field, a receiver circuit and anode, a nonmductive circuit connected to said receiver circuit, the non-inductive circuit including field e ual in magnitude to the first magnetic eld, the said non-inductive circuit being so connected to the receiver circuit as to produce changes in the magnitude of the resultant magnetic field proportionate critical'value of the magnetron; v i 13. An apparatus for producing sound by variation of an electrical current comprising an electron discharge device having a cathode, anjanode, and ameans for producing an electron discharge controlling magnetic field, the anode and cathode being eccentrically arranged relatively to each other and 7 means for effecting the relative movement of said cathode and anode to produce variations in the electron stream'dischargingfrom impinging on the latter. 14'. An ap aratus for producing sound by variations 0 an electrical current comprising a magnetron having an anode and a cathode eccentrically arranged relatively to each other, and means for effecting the vi to produce variations in producing a second magnetic ode and anode of the electron stream impinging on themagnetron anode.

15; In combination, an electron discharge device having an anode and a cathode eccen- .TIIG thereto, and means for producing a on said device of a the radius of the field of electrons emanating from the cathode is substantially equal to the shortest distance betweenthe cathode and the anode.

16. In combinationan electron discharge device having a cylindrical anode and a cathode eccentric thereto, and means for producing a magnetic field active on said device magnetic field active magnitude such that of a magnitude such that the radius of the field of electrons emanating from the oath ode is substantially equal to theshortest distance between-the cathode and the anode.

17. The methodiof compensating for fluctuations in the voltage active across the cathan electron discharge de- "vice of the ty e in which the electron emission is control ecl by a magnetic field, which consists in'changing the magnitude of the magnetic field proportionately to the changes in the critical value of the electron discharge device due to said voltage fluctuations across the cathode and anode 18 The method of compensating for fluctuations in the voltageactive across the oathode and anode of'an electron discharge device of the ty e in which the electron emission is controlled by a magnetic field, which consists in maintaining substantially the same relative nitude of the sad magnetic field and the square root of the voltage active across the cathode and anode. v

Signed at Niagara Falls, in the ,county proportions between the magt of N iagaraand State of New York this30th day of July, A; D. 1923. p

THEODORE BODDE.

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