US2256101A - Glow discharge stabilizer tube - Google Patents

Description

Sept. 16, 1941. E. MULLER GLOW DISCHARGE STABILIZER TUBE Filed NOV. l2, 1938 ffy, 7

Patented Sept. 16, 1941 GLOW DISCHARGE STABILIZER TUBE Erwin Mller, Berlin-Eichwalae, Germany, assignor to Stabilovolt G. m. b. H., Berlin, Germany, Company Application November 12, 1938, Serial No. 240,133 In Germain' November 11, 1937 4 Claims.

(Cl. Z50-27.5)

(Granted under the provisions of sec. 14, act oi' March 2, 1927; 357 O. G. v

The present invention relates in general to glow discharge tubes for regulating the voltage of electric current, and has reference in particular to glow discharge potential dividers provided with wall electrodes.

According to the present invention, discharges of relatively strong currents, between 1 and 100 ma. or more, have to start from these wall electrodes which-to give an example may be the onlyelectrodes in the discharge vessel. This result is produced by the means hereinafter described.

In the drawing, several tubes according to my invention are shown by way of example.

Fig. 1 is a longitudinal sectional view of one form of construction of the tube according to the invention.

Fig. 2 is a longitudinal sectional view showing a modified form of construction of the new tube.

Fig. 3 is a longitudinal sectional view and shows a further modiiication of the invention.

Fig. 4 is likewise a longitudinal sectional view' illustrating another form of construction.

Fig. 5 is a longitudinal sectional view of a still further modification, and

Fig. 6 is a transverse sectional view on line 5-5 of Fig. 5. f

Inthe embodiment shown in Fig. 1, l repre ably of a thin layer of graphite (Aquadag) The electrodes may be made active by known; processes, for example by the use of metals of the alkaline earths or their alloys, or by means' of atnmized magnesium. In the'v case of graphite 45 electrodes, especially colloidal graphite deposits (Aquadag) can be used'as activating medium.

4In such a case, the high reduction properties of ducing metal oxides can be applied to the walls of the tubes by means of a binder which, in the forming process, during manufacture. would be adsorbed to the metals by hydrogen.

The manufacture of the glow discharge'potential divider tubes is considerably simpliiied and made more economical by the use of wall electrodes, especially in view of the simplicity of the application of the coatings. the small space requirements, cooling through the walls is much more eiiective than in the case of electrodes which yare free standing in the interior of the tube. On the other hand, the low heat conductivity of a glass bulb, for instance, brings about but negligible heating of the electrode material which is rendered active when the stem is inserted into the bulb. Thus, the activating material is prevented from decomposing due to the heat, as is the case with metal electrodes. Further savings are realized by the fact that the'length of the tubes is reduced.

'I'he colloidal graphite mentioned above, like various other materials suitable `for the manufacture of the coating, has a high cathode drop as compared with pure metals. Any metal parts projecting from thefsurface of the layer which are in conductive connection with it, will cause the discharge to be concentrated at these metal parts. In such a case local heating will occur which will be vstrong enough to destroy the bulb at that spot, and which may even melt it.

It is therefore another feature of thepresent invention to prevent such occurrences. According to the invention, the-lead-in wires, especially the cathode lead-in wires, are so disposed with respect to the conductive coatings that they are covered by the same. In other words, the cathode lead-in wires are disposed either within or underneath the surface of the conductive coatings.

'I'his arrangement is illustrated in Fig. 2. Reieren'ce numeral 2a designates the glass bulb. 'I'he lead-in wires 5a and 6a which are connected to the conductive coatings forming the anode la and the cathode 3a, are so molten into the glass Walls of the bulb 2a that the wires are arranged underneath the surface of the conductive coatings. l The wires may extend slightly into the body of the coatings, without projecting, however, beyond their surfaces. In order to uni formly distribute the glow discharge, it is advisable to see that the distance between the two electrodes, at the points where the wires are led into the interior of the tube, is the same as at the other points. As stated above this arrangement of the lead-in wires is of advantage especially in cases where there is a high cathode In spite of manner.

ablechemicill` drop due tothe properties of certain materials used. Ithasalsobeenfoundadvantageousto makeanotchatthepointswherethewireis` led through the wall (e. g. when the vessel is made of ceramic material). the notch serving to receive the lead-in wire so that no hardening lof the electrode will occur in the interior of the tube.

Thorough investigation of the tubes described above has shown that the ignition voltage of thesetubesishigherthanthatofdischarge tubes of similar design in which electrodes made of metal sheet `are used. This phenomenon is believed to berv due to the fact that the materials used to form the coatings have `gas producing properties, and consequently part of the gases of the gaseous mixture with which such tubes are iilled combine with these newly formed gases. This factor is believed to be responsible for an increase in the ignition potential.

A further feature of the invention is to provide the tube with ignition electrodes which facilitate the starting of the tube in well known Such ignition electrode is preferably made in a way similar to the main electrodes, i. e. in the form of a. conductive coating disposed on the wall of the discharge vessel.

This feature is illustrated in Fig. 3 of the drawing. The glass bulb 2b` is provided with a cathode layer Ib and an anode layer 3b. Leadfin wires 1b and ibare connected to the anode and cathode layer. respectively. An additional coating 6b forming an ignition electrode is provided on the wallfof the lglass projection 4b. Electrode 6b, which is connected to the leadin wire 8b, represents an auxiliary anode which during operation of the tube, is connected to the voltage source over a separate series resistor. This arrangement causes relatively weak aux-- iliary current discharge between the main cathode I b and the; auxiliary anode 6b, producing ignition of the main discharge to the anode 3b at a very low ignition peak (difference be-` -tween ignition and operating voltages).

The individual conductive coatings are preferably made in such manner that a protective layer, tu be eliminated mer, is applied op the insulating material at those places where no conductive coating is to appear. This protective layer is'applied at the placs desired, e. g. be-

, tween the individual electrodes or at the sealing an easily removable'varnish may It is also possible to use for the protective layer a material which is applied in the liquid state, andwhichcanthereafterbetakenoifasalm or skin, such as for instance. collodion or gelatine. As soon as the protective skins are ailixed, the conductive electrode coatings may be applied, which is preferably done in one manufacturing operation. During the coating,`

the protected places may be disregarded. As

-soon as the electrode coating has been applied.

the protective layers are removed. The protective layers may, for example, be removed during the pumping step under suitable heating, the gasiiied being Dumped 0050i the tube It is possible, however, to dissolvethe protective layers before the pumpinrby applyinsuitglass bulb. Id represents a plurality of The protective proces described is not only for the electrodes proper but for all parts going into the constructions! the tubes and which are either to be covered, during their manufachire, with a conductive coang or are to be kept free therefrom.

According to another feature of the invention the discharge tubes intended for direct current operation are so constructed that. aside from the carbon cathode, the discharge space does not contain any other part operating as a cathode. This end can be attained either by manufacturing the lead-in wires from graphite or from graphite covered material, or by udng other metallic Yleads covered by insulating material. Thus, the pressure in the interior of the discharge tube of any bare parts on a metallic lead-in having a lower cathode drop than carbon is avoided.

This featureis emhodiediniheconstrucons shown in Figs. 4 and 5. In Fig. 4, the lead-in wires consist of metal covered with an insulatlead-in wires consist of graphite. Referring toFig.4,2cisaglassbulb,totheinterioi-wall of which two graphite coatings Ic and 3c are applied, of which ic operates as the cathode, and 3c as the anode. I'he wire 'Ic is directly connected to the anode 3c, while the wire 8c is connected at Illc to the cathode Ic after posing through a tubular glass elongation 9c which forms part of the tube. The tubular elongation 9c at its top. carries a disk vllc made of insulating material (e. g mica), so iat the wire is connected to the cathode at a point outs'uie of the discharge space proper. In Figure 4 this space is marked I2c. with an insulating substance e. g. order to prevent electric discharge In the embodiment shown in glas wool, in therethrough. u.. .it 5st? he ca e and 3d is the anode layer. The cathode lead-n i3d is made in the form of a conductive coating provided ontheinsidewallofthevesel 2d. Inorder to facilitate the manufacture, the form of the discharge vessel 2d is simpler than that shown inFig. 4. As showninFig.6,theanode3ddoes not form a complete ring but-is Provided with a passage through which extends the lead-in i3d. Fig. 6 clearly shows that this'form of conan-uc- ;iisiti; is of special simplicity, because itmerelyconthe insidewall of which twoco u w: l a: are applied. nd ctive nails -Thepresentinventloncanalsobeusedinthe design of multi-chamber glow discharge potential dividers. Insuchacase,thetubconsistof chambers, the walls of which are made of non-conductive material, for instance glass, ceramic material or the like. The electrode coating according to the invention is applied to the wall ofthe chambers. Tubforhghvoltages can be manufactured by providing a suitable conductive connection of the chambers. The connecting points of two ormore dischargegaps maynbeconnectedto atenninalcontactforthe Purpose of deriving part voltages. Itis advantageous to manufacture tubes of the type havingapluralityof chambersevenifnopartvnltagesaretobedeiivedbecauseinthatcasethe discharge-voltage and the igninn potential respectively willbe Thetubesmlyalso bemade ofmetaLusingseparators. :7s Insuchcasetheelectrodematerinlmlybeap- Space Yllc may be imm` ofasubstanallycylindrilglassbumto plied to the insulators, or, when special discharge properties are desired, to the metal wall.

What I claim, is:

1. A glow discharge tube for keeping voltages constant, comprising a double-walled container, the walls thereof being spaced apart, an anode and a cathode disposed in said container to form a glow discharge gap, and conducting means connected to said anode and cathode to admit electric current thereto, said anode and cathode having the form of layers, the latter consisting of colloidal graphite, the cathode layer being applied to the inner surface of the outer wall of said container, and the said anode layer being applied to the inner surface of the inner wall and a gas filling in said container in contact with said anode and cathode, whereby, upon admission of electric current, glow discharge takes place between the anode and cathode reducing the input voltage, while the out-put voltage remains substantially constant, independent of input current iluctuations.

2. A glow-discharge tube for keeping voltages constant comprising a double-walled container,

ducvelayerprovidedontheinsldesurtaceot the outer wall and a second conductive laver provided on the inside surface of the inner wall, and conductive means connected to said layers; said first layer forming the cathode and said second layer forming the anode of the glow discharge gap, and a third conductive layer, the latter being provided on the inside surface of'said inner wall in spaced relation with respect to said second layer, a gas iilling in said container in contact with said conductive layers, and conductive means connected to said third layer', the latter forming an ignition electrode.

3. Glow discharge tube in accordance with claim 1 in which the said layers consist of co1- loidal graphite, Aquadag, including an addition of metals of alkaline earths as activating media.

4. Glow type potential divider comprising a container, a gas lling therein, and a plurality of electrodes in said container, said electrodes forming a plurality of discharge gaps, said electrodes being in the form of layers and being applied to the interior walls o f the container, said layers consisting oi' colloidal graphite.

Eawm MLLER.

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