US2192162A - Gas discharge tube - Google Patents

Description

Feb 27, 1940. 7

H. KNlEPKAMP 2,192,162

GAS DISCHARGE TUBE Filed Deo. 18, 1957 INVENToI. HEINRICH KNIEPKAMP v WCM A TTORNEY.

Patented Feb. 27, 1940 GAS DISCHARGE TUBE Heinrich Kniepkamp, Berlin-Pankow, Germany,

assigner to Siemens and Halske `Aktiengesellschaft, Siemensstadt-Berlin, Germany, a corporation of Germany Application December 18, 1937, Serial No. 180,475

. In Germany December 29, 1936 5 Claims.

This invention relates to electron discharge devices, particularly to high voltage grid controlled gas discharge devices. v

As long as the voltages which are handled in an 5 electric 'discharge vessel do= not surpass a certain limit, it is not difficult to obtain reliable operation. But as soon as higher potentials are used,

it becomes increasingly diicult to insure 'reliable operation of the device because of the ever-preslo ent risk and danger of back-arcing and flashing. Another unfavorable factor resides in the wall charges, for these are liable to lead to unexpected and undesirable discharges, for instance, in the `formof sliding or creeping discharges or sparks. 1F. Discharges of this latter kind are likely to release occluded gases from the glass wall or shell which are very annoying and troublesome, and under certain circumstances they may render operation of the discharge vessel impossible. AEiorts to 9o eliminate these discharges have heretofore been attempted by so forming thev electrode system that the configuration or pattern ofthe electrical eld would not favor such discharges. Another remedy, in arrangements known in the prior art 35 has been that the entire discharge path, including electrodes, was surrounded by a screen or shield .optionally serving also for control purposes, or by forming the electrodes in such a manner that they would embrace or surround one 3;) another. However, even in such an arrangef ment interstitial spaces or openings exist through whichthe electrons moving at a high velocity are enabled to reach the walls ofthe vessels from the-discharge space proper Where they may build :1,5 up undesirable charges.. Moreover, the heat producedy on the electrodes, owing to the thermal shielding by the screen (control grid) or as a result of the nesting into one another of the electrodes may be carried off only with great difli- ,m culty. This again promotes undesirable discharges and more particularly back-arcing.

The .object of this invention is to provide an improved electron discharge device of the grid controlled gas discharge type particularly suit- 45 able forvuse at high voltages, and particularly such a device in which back-arcing or flash-over is substantially eliminated.

According to the invention, the plate and the control .electrodes have planar surfaces Afacing 50 each other and they have a sectional form such that the discharge space intervening lbetween the electrodes connects with the ambient space only through 'a narrow tortuous gap. The rest of the two electrodes are exposed to the interior of the tubeenvelope and do not enclose each other with (Cl. Z50-27.5)

the result that both of the electrodes are able to unimpededly radiate the heat dissipated in them.

The novel features which I believe to be characteristic of this invention are set forth with particularity in the appended claims, but the inven- 5 tion itself will best be understood by reference to the following description taken' in connection with the accompanying drawing in which Figure 1 is a vertical section of an electron discharge.

device made according to thisinvention and Figl0 i ure 2 isa vertical section of details of a modification of this invention. l,

The essential features of the invention will be understood most clearly by reference to the accompanying drawing. In Figure 1, confined l5 within the tube envelope I which contains a gaseous medium, are a cathode 2, a plate or `anode 3, and a control grid 4 forming the electrode assembly. The cathode 2 by the aid ofthe supporting rods 5 which at the same time function as current supply leads is anchored inthe press B. In' the embodiment here shown the iilament or cathode is of the hollowtype, althoughit will be understood that any othertype of cathode or source of electron supply may be used in connection with `the invention. The discharge space 'l is surrounded by a shield or screen 8 which at one end supports the control grid l4. The said control grid just like the plate is preferably made Lof graphite. This insures two advantages in that both secondary emission may be practically sup"` pressed by convenient choice of the material and that satisfactory conditions for conducting away and radiating 'the heat are secured. For the same purpose, the thickness of the graphite grid is chosen comparatively great, the desideratum being to make thearea 9 radiating off heat from For instance, it hasl the grid as large as possible. been found to be quite advantageous to choose the thickness of the grid not less than one-tenth the grid diameter. The drawing clearly shows what viewpoints are essential in choosing the sectional form of the electrodes facing each other. The continuous annular projection lll of the control grid must so engage in the annular groove Il of the plate or anode that between the two surfaces I2 and I3 there remains but a narrow gapof, say, 1-2 mm. width. Such electrons as happen to havey an outwardly directed speed component would then have to pass through this gap between the interfitting projections and recesses surrounding the discharge space between the electrodes, and they would have to alter the sense of ltheir night several times. As a consequence they would be so impeded in their motion that practically no electrons at all would be able to escape from the discharge space and reach the wall or shell of glass. The space I4, as will thus n be seen, is entirely shut oil" from the discharge.

But .in the case of this invention, and contradistinct to what is true of arrangements known in the prior art, this merit is not intended with the short-coming of poor thermal abduction. The

:o distance between the surface l of the anode andv the surface 96 of the grid is chosen of an approximate order of. magnitude of the free length of path of the electrons, with a View to precluding back-lighting. The control grid 4 is pro- )5 vided with a number of slender channels I1 for the passage of the discharge.

The discharge vessel comprising an electrode assembly built in a way as hereinbefpre disclosed .will evidence no undesirable discharges even when operating with potentials between 20 and The cross-sectional forms of the electrodes facing each other according to the invention may be chosen in diiferent ways. But care must be taken so that the discharge space between the electrodes is separated from the ambient by a gap presenting several changes in directions or curves. For instance, the groove orvcurves could also be formed in the control grid, while the anode or plate is provided with an extension or elevation designed to fit into a groove of the control grid. This is shown, for instance, in Figure 2. In this eXemplifled embodiment the anode or plate I8 has a co1- lar H9 which engages in a matching groove 20 of the control grid 2|. l

While in the exemplified embodiments here disclosed, graphite has been mentioned as a vparticularly advantageous material to use for the-two electrodes facing each other, it is entirely possible, 40 inside the scope and spirit of the invention, to

build these electrodes of a different kind of material, more particularly materials possessing highr Where electrodesv heat conducting qualities. made of sheet-metal are used it will frequently ,45 prove advantageous to provide these with heat radiating ribs or fins to still further improve the conditions of getting rid of dissipated heat.

While I have indicated the preferred embodiments of this invention of which I am now aware s() and have also indicated only one specific application for which this invention may be employed, it will be apparent that this invention is by no means limited to the exact forms illustrated or the use indicated,but that many variations may si, be made in the particular structure used and the purpose for which it is employed without departing from the scope of this invention as set forth in the appended claims.

What I claim as new is:

m 1. An electron discharge device having an envelope containing a gaseous atmosphere,acathode within said envelope for emitting electrons and an anode electrode for receiving said electrons, a tubular control electrode completely enclosing 4"5 said cathode for segregating said cathode and anode and having a perforated surface throughv an electron discharge can take place, said anode le havinga surface presented across an intervening electrode free space to the perforated surface vof the control electrode for y,receiving the discharge, said anode surface being providedwith a continuous groove, and said control'electrodehaving a1 15 continuous projection surrounding the perforated surface and extending Within said groove out of f contact with the walls .of said groove to provide a tortuous gap around the discharge path between said surfaces of said anode and control 20 electrode. v

3. An electron dischargefdevice having an`v en-' velope containing a gaseous atmosphere, a c ath-V ode for emitting electrons within said envelope, f

and an anode for receiving said electrons, a tubuz lar control electrode completely enclosing saidr Y cathode for segregating said cathode and4 anode v 1 and having a perforated-surface through which an electron discharge can take place, said anode" l having a surface presented across` an intervening 'Im electrode free space to the perforated surface oi the control electrode for receiving the discharge,` said surfacesbeing provided with interiitting projections and recessesl surrounding the discharge space, said interiitting projections and yrecesses g being spaced to provide a tortuouS gap Surrounding .the discharge path between the anode andA T control electrode. v Y. 4. An electron discharge device having an -envelope containing a gaseous atmosphera'a cathl4 6 ode within said yenvelcpefor emitting yelectrons and an anode for receiving saidelectrons, a tubular control electrode surrounding said cathode and closed at one end by a disc-like carbon member .provided with perforations through ,Vwhich electrons can pass,. said anode havingy a surface opposite said disc-like carbon memberfor receiving electrons passing through the perforations in said disc-like carbon member, an annular groove surrounding said 'surface of Said anode and animi! annular projection on said disc-like carbon member surrounding the vperforated surface of said f disc-likev carbon member and extending into said groove but out of contact with the walls .of said groove for providing a tortuous gap surroundingfr) the discharge path between the facing surfaces of the anode and control electrode.

5. An electron discharge device having a gas? eous atmosphere and containing a cathode for emitting electrons and an anode for receiving GO said electrons, a tubular control electrodel surrounding said cathode and having a closure member at each end, oneof said closure members 'being provided with perforations through which electrons can passto the anode, said anode hav` ing a surface presented tol the surface of said perforated closure member, one of' said surfaces being provided with a continuous` groove and4 the other of said surfaces with a continuous projection extending into said groove but lo'ut'ofr 70,` n

contact with the walls offthe groove for providing" l a tortuous` gap ksurrounding the discharge'spacef" between the opposed surfaces of the anode and closure member.

HEINRICH KNIEPKAMP.- f* 75.

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