US1587662A - Apparatus for generating alternating current - Google Patents

Description

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Patented June 5%, i926.

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FRITZ LOWENSTEIN, OF NEW' YORK, N. Y; JOHN C. WVAIT, ADltIINIfSTRATOIEt 01* SAID FRITZ LOWENSTEIN, DECEASED, ASEiIG'NOB, IVIESNE ASSIGNMENTS, TO RADIO PATENTS COBFOEA'IION, A DQIQESTIC GOREOlt-ATION.

APPARATUS FOR GENERATING ALTERNATING (DUKE-ENE.

Application f led November 29, 19 18.

lhis invention relates tov apparatus for generating alternating current, and more particularly to oscillation generating sys tems in which a source of direct current is utilized as the source of energy from which the alternating current is produced.

I am aware that Various types of systems have been proposed heretofore -for deriving alternating current from direct current, but such systems have not proved satisfactory in all respects. Some are complex, comparatively ineilicient, and incapable of sufliciently accurate control, while others are incapable of a large power output.

It is, therefore, a principal object of my invention to provide apparatus for generating electrical oscillations, by means of which a high efficiency and accurate control may be attained in a simple manner with a comparatively large power out-put. Other objects of the invention will appear as the description of the invention proceeds.

In one practical form of system embodying my invention, direct current is supplied to a divided circuit consisting of a plurality of parallel branches, two in a typical. instance, each of which includes a conductive gap and alternating potential-impressing means cooperating therewith. Thus, for example, each parallel branch may include an evacuated vessel of the audion type containing a heated filament cathode, a plate or wing anode, and a grid interposed in the conductive gap between the cathode and anode. The grids of the audions in the parallel branch circuits are electrically connected to gether, this grid circuit being electrically interlinked with a frequency-controlling or steering circuit, which is also electrically interlinked with both of the wing circuits. The steering circuit may be a circuit specially provided for the purpose; or the output circuit may be arranged to exercise also the functions of a steering circuit, as will hereinafter more fully appear. In any case, it is essential to the present invention that the i-JtGQllllg circuit, whether it he an output circuit or a special auxiliary circuit, shall be capableot sharp tuningf In other words, the oscillation decrement oi? the steering circuit should always be less, and most desirably very much less, than is possible with a circuit containing an iron core, such as repeater circuit of the well known type, where Serial No. 264,645.

the oscillation decrement is commonly not less than 0.1. In the practice of the present nvent on, the oscillation decrement of the steering circuit is never as high as that of an lron core or repeater circuit; and in the best embodiments of the invention said decrement is of a much lower order of mag mtude, say 0.01 or 0.001,in typical examples. By means of such a sharply tunable steering circuit, great accuracy in controlling the frequency of. the alternating current generated, is attained, as well as other advantages, especially in high trequencv work. l i hen a system of the character deseribed is in operation more current from the direct current source flows alternately through one wing circuit and then through the other, owing to the modulating effect or the interposed grids; and the relation of the wing circuits. to the output circuit is such that an alternating current is thereby induced in the latter. The frequency. of this alternating current is determined and governed with extreme accuracy by the sharply tuned steering circuit before mentioned which impresses upon thegrid circuit whatever frequency may be desired, thereby causing an alternating rise and fall of potential in the resp ctive grids in such manner that when the potential of one grid is raised, the other is lowered, and vice versa. Thus the modulating effect of the grids, which is electrostatic in the present invention, is positively governed and the output frequency accurately controlled in a regula-ble manner. The frequency may of course be adjusted or varied by suitable adjustment of the constants of the steering circuit, vs 'hether the latter be the output circuit proper or a special auxiliary circuit.

The objects and novel features of my invention will be. more fully understood,from the. following description taken in connection with the drawing in which Figs. 1 and 2 are diagrams of systems embodying my invention.

In the specific embodiments of my invention illustrated in the figures or the drawing. the, divided circuit consists ftW li branches or wing circuits}; and Y, to which a battery or other suitable source of direct current, is connectedby the conductors and 11. 'llhebattery B together with the conductors lfi aud 11 and thawing circuits X and Y thus form a closed direct current input circuit for the generating system.

Vacuum tubes T and T, which, for example, may be audion tubes of well known cinistruction, are connected in the branch circuits X and Y, respectively, the filaments 12 and 13 thereof being connected by conductors l4 and 15, resp ctively, to the con ductor l0, and being heated by current from the batteries A and A, respectively, or by current from some other suitable source.

1 The wings or anode plates 16 and 17, cooperatmg with the lilaments l2 and 13, re-

spectively, to term parallel conductive gaps, are connected by conductors 18 and 19 to the conductor 11.

The PliClS 20 and 21, constituting alternating potential in'ipressing means, are inter posed in the conductive gap between the lilaments and plates of the tubes T and T, respectively. T hese gri ds extend. across the streams of electrons passing from the respective filaments 12 and lb to the plates 16 and 17, and when the respective potentials oi the grids are varied, as by alternate increase and decrease, the currents 'tlowing in circuits X. and Y are modulated, by the electrostatic effect of the grids, so as to alternately increase and decrease thetlow of crrent in the respective wing circuits. The grids 20 and 21. are electrically connected together by a conductor 2 that includes a winding 23, by means of which the potentials on the grids may be accurately controlled or varied, in a manner to be set forth later.

Most desirably an intcrn'iediate point, usually the mid-point oi": the winding'fZS, is connected as by lead 23 to a point which may be either at substantially the same po tential as the cathodes l2 and .13. or more negative than said cathodes, (lQPEllCllllQ'1113011 the use to which the system is to be put. To rovide for operating under either condi tion, the lead 23 is arranged For adjustable connection at 23" either to conductor 10, for example, or to some point on the battery 1% as in the particular arrangement illustrated. In the latter case, which is a condition best adapted for telephone work, a potential more negative than that 01" the cathodes 1:2 and .13. is impressed upon the grids 20 and El, and the degree of this ultran itire potential may evidently be adjust-en as desired by shifting the lead connection.

For high frequency work, the connection may be shifted to equalize the grid and filament potentials.

The output or load c rcuit may comprise any suitable form of energy absorbing or translating means. its specific example, the load circuit illustrated is a tuned antenna circuit for a wireless telegraph or telephone transmitter. The antenna circuit embodies an aerial 2i, a ground 25, and inductances 26 and 27, which are inductively related,'res )eclively, to inductances 28 and S25) constituting portions of the conductors 1S and 1.) of the wing circuits X and Y, respectively, the a n tenna circuit being thereby loosely coupled to both said wing circuits. Although this arrangementis .i'nost desirable, the antenna may nevertheless be coupled to only one of said wing circuits. It will be understood that in the arrangement illi'istrated the coils 26 and 2? are usually and most desirably so wound and connected in the circuit that they are mutually assisting.

Particularly in the type of system illustrated, wherein the wing circuits are also free of iron cores and possess a low oscillation decrement, only a single wing circuit may be used.

Suitable means are provided to govern the "frequency of the grid potential alternations. In the arrangement illustrated in Fig. 1, the tuned antenna circuit is utilized as the frequency governing or steering circuit. This is accomplished by including in the antenna circuit a. winding 30, which is inductively related to the winding 43 connected to the grids :20 and 21, and thereby loosely couples the antenna and grid circuits. As here shown, the antenna circuit also contains a variable tuning inductance 31 by means of which the constants of the antenna circuit may be altered desired to provide for transmitting at different wave lengths, for example. It is especially to be noted that the antenna circuit in this instance contains no iron core or repeater, and that it has a small oscillation decrement ot the character previously described. The arrangement illnstrated. wherein the inductances 30 and 3 are between coupling induetances 26, 27, and ground, with inductance 3O nearest ground, otters special advantages, and is preferred.

The operation of the system shown in Fig. l is briefly as follows: Direct current being; supplied to the two wing circuits X and Y b the source of direct current B, pulsating cuiients are up in the wing circuits by virtue of the circuit cl'iaracteristics; and alternating; current oscillations are induced in the antenna circuit. These latter in'nnediately exercise a predominating influence, through the loose coupling 30, 23, on the grid potential alternations, each gridhaving;- impressed upon it potentials alternating in synchronism with the antenna. oscillations but substantially out of phase with each other. The frequency ot the antenna oscillations can be adjusted at will by shifting switch device for example, to vary the etiective value of inductance 31.

It will be observed that simply by shifting a single controlling: member, switch arm in this instance, the frequency of the oscillations in the antenna or output circuit may be changed to any desired value without adjustmg any other part of the system, The imr 1: oer/secs portance of thisarranggeiuent in enabling, tor example. rapid and easy shittto any desired wave length in transn-nitting radio signals is at once apparent.

in the arrangement shown in Fig. 2, an auxiliary ltrerpiency-e-ontrollinpj or stecrin); circuit is en, oyed to impress a governing; alternating )otential. ot the desired uuency on the connected grids. This auxiliary circuit may take various forms, but in any case must be capable of sharp tuning. As here shown it comprises a variable capacity 33, and inductance of which a part, 34, cooperates with winding 23 to loosely couple the grid and steering circuits; while pick-up coils 34S and 34;", coo fierating with windings and 29, respectively, loosely couple the steering and the output or antenna circuits. The antenna circuit may include a variable tuninp; capacity 35.

This embodiment of the invention operates in substantially the same manner as the system of Fig. 1, but the auxiliary tuned circuit governs the output "frequency, taking; energy from the wing circuits and impressing upon the grids an alternating potential of predetermined frequency.

Aflthough a tuned antenna is shown in Fig. 2, the use of a special auxiliary steering; circuit is not to be understood as limited to a system where the output circuit is tuned. On the contrary, an auxiliary, steering circuit is especially useful where it is not desired to have the output or consumption circuit tuned, or where the consumption circuit can not be as sharply tuned as the auxiliary steering circuit.

ll hile the above described systems, which may be called splitters, involve the use of more than one audion or equivalent device, certain features of the invention are evidently applicable to splitter systems in which only one of the parallel circuits contains such device, the other circuit being in the nature of a by-pass and containing inductance and capacity, tor example. It is also to be understood that the systems herein disclosed may, within the invention, be inductively or otherwise associated with telephone or other input circuits, provided the steering; or treq iency-controllinc; circuit be capable of sharp tuning, as hereinbeiore set forth.

What I claim is:

1. A. system for generating alternating current comprising the combination with a source of direct current, of a pair of thermionic devices each including an anode, a cathode, and a modulating device cooperating therewith, parallel circuit connections whereby said thermionic devices are connected in circuit with said source and in parallel with each other, each of said parallel circuit connections including an inductive winding, a connection between said modulatingdevices, and a sharply tunable circuit inductively coupled to such modulating de vice connection in such manner as to produce alternating potentials of substantially di'li'ering phase on said modulator devices, said sharply tunable circuit including separate inductive windings cooperatingrespectively with the inductive windings in said parallel circuit connections.

In a system for generating alternating such modulating device connection in such manner as to produce alternating potentials of substantially difliering phase on said modulating); devices, said sharply tunable circuit includinq separate inductive windings cooperating with the respective inductive windings in said parallel branches.

3. In a system for generating alternating current, the combination with a circuit having a plurality of parallel branches, and means for energizing; said circuit, of thermionic means having anode, cathode and modulating means included in each of the parallel branches of said circuit, whereby parallel thermionic current paths are provided, a plurality of inductive windings, arranged one in each parallel branch of the circuit, a connection bet-ween the different portions of said modulating means in said parallel branches, and a separate sharply tunable circuit coupled inductively, only, to such modulating means connection in such manner as to produce alternating potentials of substantially differing phase on said difterent portions of said modulating means, said sharply tunable circuit including separate inductive windings cooperatiin; with the respective inductive windings in said parallel branches.

4:. In a system for generating alternating current, the combination with a circuit having a plurality of parallel branches, and mean's for energizing said circuits, of plurality of thermionic devices, each including; an anode, a cathode and a modulating device, each thermionic device having its anoce and cathode included in its respective parallel branch of the circuit, whereby the thermionic devices are arranged in parallel with each other, a plurality of inductive windings, arranged one in each parallel branch duce alternating differing phase on said modulating dev1ces,.

of the circuit, a connection between said modulating device, a separate circuit coupled inductively, only, to such modulating device connection in such manner as to propotentials of substantially said separate circuit including separate inductive windings cooperating with the respective inductive windings in said parallel branches, and an output circuit related to 10 said parallel branches.

In testimony whereof I hereunto afiix my signature.

FRITZ LONENSTEIN.

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