US1815762A - Electric discharge device - Google Patents

Description

July 21, 1931. E. E. CHARLTON ELECTRIC DISCHARGE DEVICE Filed July 17, 1924 Patented July 21, 1931 -UNITED STATES PATENT OFFICE ERNEST E. CHARLTON, OF SCHENECTADY, NEW YORK, ASSIGNOR T GENERAL ELEC- A TRIO COMPANY, A CORPORATION 0F NEW 'YORK ELECTRIC DISCHARGE DEVICE Application mea July 17,

the efliciency and current-carrying capacity`v of this type of rectifier.

1o My invention relates particularly to the class of gas ionization rectifiers in'which a cathode is employed having a relatively much larger surface than the anode, thereby obtaining an asymmetric conductivity. Heretofore, these rectifiers have been made only for half wave rectification.

The provision of more than one anode in such a rectifier is not sufiicient alone to secure efficient full wa-.ve rectification, as a relatively large current flows between the anodes in the gas which not only wastes energy and reduces the efficiency of the device but the discharge between the anodes will eventually change to an arc discharge. The tendencyfor discharges between the anodes to occur will make the rectification unstable. In accordance with my invention, I have provided a rectifier having a plurality of anodes in which the cathode is so disposed between the anodes as to largely suppress the I undesired flow of current between the anodes, and to produce stable rectification. I have provided several forms of rectifiers in all of which the cathode acts as a shield between the anodes, but which differ somewhat in their construction. For example in one form of my invention the shielding is more complete than in the simplest form to permit operation at higher voltages and in still another form an apertured envelope of lnon-conducting material is provided about the one or both anodes to permit rectification of current of still higher voltage.

The novel features of my invention will be described with greater detail in the following specification taken in connection with the accompanying drawings in which Fig. 1 illustrates in perspectivea simple form of rectifier forA the rectification of currents ofl moderate voltage; Fig. 2 is a perspective 1924. Serial No. 728,638.

view which is partly in vertical section of another formo higher current-carrying capacity; Fig. 3 illustrates a third form of my invention, of still higher current-carrying capacity, this view also being partly in vertical section; Fig. 4 is a diagram of electrical connections which may be used for my improved device; and Fig. 5 is a fragmental View of a modication..

The device'shown in Fig. 1 comprises a bulb 1 in which are mounted a plate-shaped cathode 2 and anodes 3, 4 which are located on opposite sides of and closely adjacent to the cathode 2. The cathode 2 which is of the unheated or self-sustaining discharge type may vrconsist of nickel, iron, molybdenum, tantalum, or of other metals which can be readily shaped into plate form and which are not easily vaporized at moderately high temperatures. The anodes 3, 4 in the device shown in this figure consist of wires of tungsten, nickel or of other suitable metal. Tungsten is preferred as it may be readily sealed through the projections 5, 6 of the. hard glass stem 7, only short sections of the wires projecting beyond the glass. The anode wires are led through the glass stem and are connected to the contacts 8, 9 of theIl bayonet type base 10. The cathode conductor 11 is sealed to a contact 12 of the base.

The bulb 1 is charged with a suitable gas which at the operating temperature of the device will have a density high enough to produce a desired conductivity by ionization. For example, the bulb may be charged with helium and neon as the ionization medium. Helium is much to be preferred. The pressure of the gaseous filling may be varied between wide limits depending upon the characteristic of the gas, the operatin voltage. the geometric construction of the evice, the current-carrying capacity and other tube conditions. In general the pressure of the gas may be varied between the limits of about terial which is chemically reactive toward gaseous impurities, or is otherwise capable of removing contaminating gas, such as water vapor, oxygen, hydrogen and nitrogen. For example, I may apply to one of the electrodes a small quantity of metallic magnesium, calcium or the like and then after the bulb has been exhausted, freed from water vapor, and charged'with helium or other desired gas, the electrodes are heated by a. high frequency field to the vapolizing temperature of tlie magnesium, or other alkali earth metal, thereby depositing,r a film of this metal on the walls of the bulb. The voltage consumption in the device is lowered about 20% by the presence of a film of finely divided magnesium.

The voltage drop may be st1ll further lowered with an accompanymg lncrease of etliciencj; by admitting an alkali metal, preferably csium or rubidium into the bulb before the magnesium is vaporized and oxidizing the alkali metal as by admitting a little oxygen and warming the bulb. The oxidevof the alkali metal appears toreadily combine with hydrogen which is liberated during the operation of the rectifier, probably by the decomposition of water vapor given off by the bulb. By the use of caesium oxide together with magnesium I have reduced the voltage drop to less than one-half its original value. This chemical addition to the gas atmosphere whereby the voltage drop is lowered is covered by my application, Ser. No. 726,640.

As shown in Fig. 4, the rectifier maybe used by connecting the anodes 3, 4 to the opposite terminals of a source of alternating current, such as the terminals of the secondary of a transformer 13, while the cathode is connected by a conductor 14 in series with a load 15 to an intermediate point on the transformer secondary.

The load 15 here has been represented as a non-inductive resistance, having voltage taps whereby rectified current at different voltages may be made available forA radio systems or other purposes. The rectifier, of

course. may be used to furnish rectified current for other loads, such as storage batteries, or direct current instruments. A steady current condition may be produced by the use of a wave filter consisting of a series reactance 27, and shunt condensers 28, 29.

In the device shown in Fig. 2, the cathode surface is even larger with respect to the anode surface than in the device shown in Fig. 1. The cathode assumes the form of two substantially cylindrical housings 16, 17 surrounding the respective anodes 3, 4.-.

These housings, which are electricallv connected together, as indicated at 31, are mounted on the stem 7 which is sealed in the 4bulb l.l In this form of my invention the area of the cathode is about 300 times greater much larger rod-like bodies which are mounted upon the leading-in conductors 20, 21. In order to reduce theeff'ective area of these anodes 18, 19 and thereby to give a rectifying characteristic to the device,l these anodes are respectively surrounded by insulating envelopes or shrouds 22, 23, which are spaced closely adjacent to the anodes at the sides but are spaced away from the end face of the anodes. Apertures 24, 25 of restricted size are provided in these envelopes at the ends, which are spaced away from the anodes. In some cases, as'shown in Fig'. 5,la conductive coating 26 maybe rovided to advantage upon the inner surl ace of tlie anode shrouds. The anodes in this case are connected to the conductive coating upon the inside of the shroud. In Fig. 5, the anode 19 is connected to the coating26 by a suitable conductor 30, in this case a'.` helical spring sprung between the anode and the surrounding envelope. When this device is charged. with a suitable gas, such as helium, a glow discharge can readily pass from the electrodes 18,- 19 alternately to the surrounding cathode constituted by the members 16, 17.

As the polarity of the electrodes 18, 19 alternates current fiows to the cathode alternately from the anodes 18, 19 during the intervals when each respective anode is positive. In other words, the apertures 24, 25 in the envelopes 22,23 surrounding the respective anodes do not prevent the passage of electrons from the outer casing constituting the cathode to the anodes but due to their relatively small diameter they will prevent electron flow in the opposite direction. Apparently a negative charge accumulatesupon the inner surface of the anode shrouds 22, 23 which repels the electrons emanating from the electrodes 18, 19, largely suppressing current flow between the electrodes 18, 19. Arelatively large currentA can flow in the opposite direction as little or no` negative charge can accumulate on the outside ofthe envelopes 22, 23. Such a charge will be neutralized by the more active positive ionizmation occurring in the space' between the shrouds and the cathodes ,16, 17.

Furthermore, a negative charge on the outside, evenv if present, would not be so effective in suppressingv current flow as a charge on the inside. Whatever may be the mechanism of'conduction, I have obtained sub- ,vez

stantially complete rectilication with devices 4therein, sleeves of insulating material closely as shown in Fig.' 3 with impressed mean ef-d fective voltages between the electrodes 18, 19 higher than 2,000 volts.

What I claim as new and desire to secure by Letters Patent of the United States, is

l. An electric discharge device comprising a container terminating in a reentrant stem, a plurality of anodes therein, a cathode of the self-sustaining discharge type having a materially largersurface than said anodes, said cathode constituting a shield between said anodes and being closely adjacent thereto, all of said electrodes being surported solely from said stem and an ioniza le gas in said container having at the operating temperature of said device a pressure sufiiciently high to. conduct an ionization current be'- tween said electrodes.y

2. An -electric discharge device comprising a plurality of point anodes, a cathode of the self-sustaining discharge type which has a materially larger surface than said respec- :ill

tive anodes, said cathode being closely adjacent to and substantially surroundingI the anodes and having a portion intermediate said anodes to thereby shield them from one another, an enclosing container and an attenuated'gas in said container.

3. A rectifier comprising a plurality of anodes, a cathode constituted by a conductive practically complete housin surrounding each of saidrespective anodges and acting to shield said anodes from one another, said anodes each having a materially smaller surface than said-cathode, an enclosing container and a gaseous filling of inert gas therein ata pressure of about 5 to 80 millimeters of mercury.

4. An' electrical discharge device comprising a plurality of anodes, a cathode located Ybetween and constituting a shield for said anodes and shrouds ofl non-conductive material, each havin an aperture, 'respectively surrounding sai anodes, van enclosing con tainer and a filling of gas in said container mert with respect to said electrodes and having a pressure at operating temperatures which is suiiiciently high to produce a substantial current-carrying capacity by being ionized.

5. A rectifier comprising 'a plurality of i anodes consisting of diicultly vaporizable metal, insulating envelopes therefor closely surrounding the sides of said anodes, and

.each having an aperture opposite the endsA of surrounding all but an exposed tip of said anodes,elongatedhousings of sheet metal rev spectively enclosing said anodes and being electrically connected to constitute a common cathode and a chargeof attenuated gas in said container e 7. A rectifier for alternating current com- -prising a container, a stem projecting into said container, said stem having a plurality of elongated extensions, wires sealed respectively into said stems and each having a tip protruding from said respective extensions, 4 metal housings mounted upon said stem and respectively surrounding the tips of said wires, an electric connection between said' housings, external contacts for said wires and said housings and a charge of gas in said container at a pressure of the order of 5 to 80 millimeters of mercury. f

8. A rectifier for alternating current comprising a container, a plurality of anodes located therein, 'a cathode constituting a conductive housing substantially surrounding each of said respective anodes and constituting a barrier between said anodes, said cathode having a materially largersurface than either of said anodes, aperturedshrouds'consisting of insulating material ,respectively located between said anodes and said cathode and a readilys ionizable gaseous medium 'in said container.

In witness whereof, I have hereunto set my hand this 16th day if July, 1924.

ERNEST E. CHARLTON.

said anodes'and spaced away therefrom, a f I y cathode having a plurality ofmembers respectlvely surrounding said envelopes and spaced away therefrom," a'. surroundm container and a charge of rare gas inL sai container at a pressure of about 19 millimeters of mercury.

040A rectifier for alternatin current compricing a container, a plura ty of anodes

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