US1878341A - Voltage regulator - Google Patents

Description

Patented Sept. 20, 1932 UNITED STATES PATENT OFFICE PEBGY L. SPENGEB, OF MEDFOBD, MASSAC'HU'SE'ITS, ASSIGNOIR T0 RAY'IHEON ING. OB CAMBRIDGE, MASSAGHUSET'IS, A CORPORA'I'ION' O13 MASSAOHUSETTS VOLTAGE REG-'ULATOR Applloatlon flled. Marob. 151928. Serlal N0. 261,976.

The present invention relates in general to gaseous conduction apparatus and in partieular to a device for regulating the line voltage in a system subject to voltage or cu1- rent changes or both.

F01 voltage regulation purposes in radio supply cireuits and elsewhere, it has been proposed heretofore to connect across the line a gaseous discharge device in which the anode consists of a solid cross-sectioned bod positioned within a hollow cathode. T e gas employed is of the monatomic group, ordinarily helium, which commends itself chiefly by way of minimizing cathode disintegration under conditions of fairly high current and also in requiring a purification process simpler than in the case of neon or argon.

Tests conducted by me have demonstrated the fact that in prior art tubes including those filled with helium, there is considerable instability of operation manifested by way of irregular output and other disorders. The origin of the d1sturbances is hard to ascertain but I believe it to reside in the region of the positive electrode and to be a function of voltage drop at this point, which discovery is based upon the fact that when the voltage loss at that surface is reduced, the tendency of the regulator to produce uniform terminal voltage becomes pronounced even under couditions of variable input.

While there are many factors which contribute 1:0 otential loss at the electrode, the decrease in each serving to produce greater stability, the condition of instability is parlsicularly emphasized in the case of prior art anodes of solid construction and in the event, the helium or other gas cdntains an electro-negative impurity e. g. nitrogen o1 oxygen. Furthermore, the discharge in the neighborhood of a positive member having small area is likely to show unstable characteristics under conditions of apgreciable loa'd, producing unsatisfactory per ormance as a current by-pass.

I have also found by experience that instability in regulator tube is much more likely at relatively high than ab low gas pressure; there appears to be a definite pressure applicable to euch of the rare gases below which a taube of' given size and design remains stable even under the most unfavorable circumstances. The transition from the unstable 130 stable conditions ab the gas pressure referred to is to be sharply distinguished from the case where gas is entirely removed from the envelope, to produce a hard vacuum, by which uniforrnity 0f operation and lack of sensitiveness may be secured. In ehe present invention, the presence 0f gas is not only desirable but essential and it is apparent that a gaseous conduction device operating under stable conditions is fundamentally diflerent from a strictly electron discharge apparatus.

I propose to modify the construction of prior regulators in order t0 reduce to a stable factor the anode losses, at the same fime securing all the advantages obtainable from the use of helium. The modification is centered about a novel form of anode which has been found t0 operate well in conjunction with a hollow cathode. The modification takes on simple construction and design without the necessity of critical dimension, thus lending itself readily 130 ease of manufacture and mass Production. It also has a high degree of reproducibility, i. e. all tubes made in accordance with the design have substantially the same internal characteristics.

For the purpose of illustrating the genus of the invention, a typical embodiment is shown in the accompanying drawing.

The figure shows an envelope 1 formed of glass and terminating in a press 2. Within the envelope and supported frm the press in suitable manner e. g. by fusing the lead-in Wires in the glass, there is a hollow cathode 3 of closed perimeter preferably shaped as an open-ended cylinder and made of refractory material. The anode 4, also refractory, is smaller in dimension than the cathode, a condition which is decidedly beneficial in operation. The anode has a shape conforming to that of the cathode, and is positioned within the latter preferably in coaxial relation therewith, i. e. concentrically in the lateral direction, and midway between the cathode edges in the direction of the principal axis. Numeral 5 designates a wire or additional electrode employed for sta1:ting pnrposes; this electrode 1s located relatwely close to the inner surface of the cathode as shown.

Attached to the cathode, there is a etallic capsule 6 containing substange for 1ber-' ating by heat treatment, act1ve electropositive material; this substance 1s preferably a mixture of two or more all xah 1netals, e. g. caesium and potassium, as clauned- 11 my a plication Ser1al N0. 204,320 ent1tled ctifier tubes with a preferred proportion of five parts gotassium to one part caesium. As pointe out in the application supra, the potassium takes on the ri}le of getter leaving to the caesium, the funct1on of minimizing otential drop. The capsule preferably should be insulated from the. cathode und for this purpose, I provide a metallic wire in two sections insulatingly separated by a. glass bead 7. The receptacle or container 1 1s filled with a gas of the monatomic group, preferably helium at a ressure ranging from 15 to25millimetersof g. The manufacturin process may be completed by furnishin a ase for the envelope carrying contact p ugs.

In operation, the regulator is connected across the line, in case of a B eliminator ordinarily of 90 volts, cathode 3 to the negative side, anode 4 to the positive side and a tap taken from a point in the circuit where the voltage is sufficiently high to provide the necessary starting otential for auxiliary anode 5. Upon initiation of a discharge between the cathode and operating anode, a eurrent path is established in shunt to the load which acts as a by-pass for excess Current caused by potential variations.

While anode 5 may be used solely as a starting ex edient, e. g. by providing a suitable metho of rende r1ng it inoperatwe upon completion of the startiflg function, it l1as been found advantageous to continue the discharge throughout the entire operating period of the regulator; the auxiliary flow of current appears to raise the intensity of ionization within the hollow cathode to a uniform level, making .for improved operation. A tube as described, has the desirable property of producing a substantially constant voltage drop across its terminals regardless of the magnitude of current passing, and has a great degree of stability. The current-.

voltage characteristic shows a substantial portion in parallel to the current axis whieh portion is selected for operation, so that notvvithstanding substantial changes in current through the ti1be, no substantial voltage variations take place across the terminals.

Experience has shown that inside my novel hollow-anodedevice, the otential drop in the vicinity of the positive electrode, i. e. the voltage necessary to draw electrons to the anode surface, is materially lass than in the case of a member having solid cross-section. While the reason for the voltage difference is diflicnlt to ascertain correctly, and accordin ly I do not wish to be limited to my explanat1on, I believe it to reside in the fact that within the hollow ele@trode, there is a region of intense ionization giving rise to electro-positive ions of large mass and small mobility which reduce the negative space charge of the electrons moving to the anode. The glow represents a congregation of positive 1ons which act to draw other electrons through the open ends of the cylinder with the result that the edges or rims over which the stream pours, oflers a very 10W potential loss to the passing current. Inasmuch as the voltage drop is determined, not directl from the electron stream, but rather from t e ionization caused by the same, a secondary function, the discharge remains stable even under conditions of hi h current and when emp loying an anode 0 relatively small dimens1on. also counteracts the tendency of the electronegative impurities, drawn to the region by the a0tion of the electric field, from raising the anode loss.

This phenomenon may be considered from.

prior art, the anodes were such that the total active surface thereof became velvety. In my device, the surface of the anode which is bombarded and the active surface of the anode are difierent. Those electrons which go very fast, hit the outer anode surface' causing the velvet; appearance. But m0st of the current carrymg particles take a curved path to the inner surface of the anode, which is probably the surface having the lowest drop or anode loss, and in doing so are slowed down considerably. Hence there is no or little anode bombardment and no velvety surface is formed on the inner surfat:es of the anode. In a broader sense, any anode The intense ionization referred to,

having reentrant er concave surfaces would wide limits; in the same manner, the relative diameters may be changed. Duo to the arrangement and design of electrodes, and the pressure of the gas, the degree of stability is exceedingly marked, giving the tube a non-critical oharacteristic under all conditions of operation and furnishing a safe mar-v gin of stability to enhance reproducibility and mass production. The cylindrical form of anode offers an advantage during manufacture in that it may be heated by a high frequency discharge during the pumping process, thus efi'ectively removing the gas hold by occlusion.

In reducing the loss in potential at the positive electrode when stabilizing the discharge, the hollow-anode type of space eurrent device oflers a greatly improved voltage regulating property. Since the anode drop is low, it is not so dependent upon the negative space charge in its vicinity and is, therefore, a small factor in the voltage drop of the tube. The tube exhibits only small variation with changing current, the total potential drop remaining practically constant, even under conditions of varying ioad.

I claim:

1. A gas discharge device oomprising the combination with an envelope containing a gas at a reduced pressure, of a cathode, an anode within the cathode, and a source of alkali metal vapors supported by but insulated from one of said electrodes.

2. A gaseous regulator tube for regulating the voltage across a direct eurrent source' comprising, a gas tight vessel containing 1on1zable gas at a pressure suific1ent to ma1ntain a glow discharge between two spaced elect1odes therein, a hollow relatively large area cathode in said vessel adapted to be connected to the negative terminal of said source, and a hollow anode of smaller area than said cathode disposed inside said cathode and adapted to be conriected to the positive terminal of said source so as to maintain through said gas a regulating glow discharge with said cathode at which a substantially constant iroltage is secured across said source.

3. A gaseous regulator tube for regulating the voltage acr0ss a direct current source comprising, a gas tight vessel containing ionizable gas at a pressure suflicientto maim tain a glow discharge betWeen two spaced electrodes therein, a hollow oylindrical relatively large area cathode in said vessel adapted to be connected to the negativeterminal of said source, and a hollow cylindrical anode of smaller area than said cathode disposed inside said cathode and adapted 30 be connected to the positive terminal of said source so as to maintain through said gas a regulating glow discharge with said cathode a1:

the voltage across a direct current source comprising, a gas tight vessel containing ionizable gas at a pressure suflicient to maintain a glow discharge between two spaced electrodes therein, a hollow relatively large area cathode in said vessel adapted to be counected to the negative terminal of said source, a hollow anode of smaller area than said cathode disposed inside said cathode anti adapted to be connected to the positive terminal of said source so as to maintain through said gas a regulating g1ow discharge with said oathode at which a substantially c'onstant volta-ge is secured across said source,

and an additional electrode for maintaining throughoutsaid regulating discharge an independent discharge inside said vessel ionizing the gas therein.

5. A gaseous regulator tube for regulating the voltage aoross a direct current source comprising, a gas tight vessel containing ionizabie gas at a pressure suflicient to maintain a gl'ow discharge between two spaced electrodes therein, a hollow relatively large area cathode in said vessel adapted to be connected to the negative terminal of said source, a hollow anode of smaller area than said cathode disposed inside said cathode and adapted to be connected to the positive terminal of said source so as to maintain through said gas a regulating glow discharge With said cathode at which a substantially constant voltage is secured across said source, and an additional electrode disposed inside said cathode for maintaining therewith throughout said regulating discharge an independent discharge ionizing the gas in the vessel.

6. A gaseous regulator taube for regulating the voltage across a di1ect current source comprising, a gas tight vessel containing ionizable gas at a pressure suflicient t0 maintain a glow discharge bet-ween two spaced electrodes therein, a hollow relatively large area cathode in said ves sel adapted to be counected to the negative terminal of said source, and a hollow anodeof smaller area than said cathode disposed inside said cathode and adapted t0 be connected t-o the positive termina.l of said source so as 130 maintain through said gas a regulating glow discharge With said cathode at which a substantially constant voltage is secured across said source, the gas in said vessel including a monatomic inert gas and alkali metal vapor.

Intestimony whereof, I have signed my name to this specification this 13th day of March, 1928.

PERCY L. SPENCER.

which a substantially constant voltage is seeured across said source.

4:. A gaseous regulator tube fdr regulating

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