US1875744A - Arrangement for dispensing badly conductive substances in vacuum valves - Google Patents

Description

Sept. 6, 1932. B. LOEWE ARRANGEMENT FOR DISPERSING BADLY CONDUCTIVE SUBSTANCES IN VACUUM VALVES Filed May 25, 1929 Patented Sept. 6, 1932 UNITED STATES PATENT! OFFICE ZBERNHARD LonwE, F BERLIN, GERMANY ARRANGEMENT .FOR DISPENSING .BADLY oo'NnUcrIVE SUBSTANCES IN VACUUM VALVES r I Application filed May 23,1929, Serial No. 365,340, and in Germany May 12, 1928.

The invention relates to an arrangement for dispersing substances in vacuum Valves.

It is possible by means ofthe arrangement.

according to my invention to evaporate substances both during the process of manufacturing the valve and afterwards, should an evaporation benecessary during the. operaation or putting into service of the valve.

In this respect the device according. to my invention differs from other known devices where the substances to be dispersed are arranged, for instance, on an auxiliary wire which, prior to the manufacture of the valve,

. is so strongly heated that, once the valve has beenput into service the process of dispersal cannot be continued.

It is a further well known-practice to scatter substances in vacuum valves by heating them by eddvcurrents. In this manner, how- 0 ever, only substances with certainconductivities may be disnersedrwith some degree'of effectiveness. If. moreover, such shape is given to the substances that eddy currents of ,suflicient strengthmav be generated in the substances by means of a field generated outside the valve, it is possible to evaporate, for

instance. getter substances such as mag nesium within the valve by eddy current heating.

tive. respectively non -conductive or electrolytic substances are to be evaporated or even only heated. this process may not be applied 0 because in badlvconductive substances eddy currents cannotbe induced to a noteworthy If, however. salts or other badly conducsuitable frequency is allowed to act upon the valve from the outside. As close as possible to these points to be heated with particular intensity the substance to be heated may, ac cording to my invention, be arranged. If, more particularly, the substance to be heatedis non-conductive,it may be arranged in such.

' manner that it 'directlyencloses the point to be heated intensely and may thus be heated v by heat conduction. If, however, it possesses 5 a certain amount ofjconductivity it maybe advisable to arrange it at a moderate distance from the point to be heated intensely in order that the conduction of the eddy currents in the portion or element to'beheated intensely may notbe impaired by the presence .ofsuch substancel p 1 The dispersal of substances according to my invention is applied in the first place in the manufactureof highly emissive cathodes. 5 The tablet of barium oxide and silicon or ferro-silicium and aluminium to be used according, to my invention described in appli cation No. 342,930 and filed February 26th, 1929, is generally such. material of very small electric conductivity or contains such mate-' rials. If such material is to be dispersed in the shape of a tablet or lozenge on the inner surface of the anode by eddy current heating it is necessary for the anode to be heated with particular intensity at the point of attachment. Accordingto my invention the anode is provided with two slots forthe substance to be dispersed at the side of the place of attachment and the point of attachment 80.

7 therefore takes place at such point. It is pos- The slots 2 in the anode may from the outside across the glass jar or the electrode system and whose axis is coincident with the axis of the cylindrical anode, the induced eddy current lines run at the cylindrical jacket of anode 1 essentially in circles which, however, on account of the slots 2 are greatly compressed on bridge 3 and a particularly strong heating,such as described,

sible to arrange the substance to be evaporated according to my invention in the shape of a lozenge 4 on the bridge 3. If the substanceis non-conductive, the current conduction is not essentially changed by the presence of such substance and in bridge 3 the same quantity 1 v of heat is therefore produced as would be produced 1 without the presence of the sub stance 4. Part of the heat developed in the bridge 3is drained off through the body 4 and the effect to be produced by the heat is there fore produced. in the body 4.

The element or body 4 is attached onthe bridge on the inner surface ofthe anode and may consist of a reactivecompound according to my invention described in application No.-

342930 and filed February 26th, 1929. The effect to be produced bythe heat is the dispersal of the substance 4 for purposes of form-v ing .a highly emissive layer. on the cathode 6.

The electrode system according to Fig. 1 is;

complemented by the grid 7.

narrow if, however, notwithstanding such narrowness interferences may beexpected in particularly sensitive valves by the leakage of electrons through these slots, the slots mayadditionally be covered by non-conductive material; it is possible, for instance, ,in the manner indicated in the figure to make them as wide as a mica-sheet is thick and to insert one or several mica plates, into the slots 2. I

Fig. 2 shows a further embodiment of my invention where an element of conductive material is to be heated. In this case it will not be advisable to arrange the lozenge 4 immediately on the bridge 3 of the anode. For

" this purpose, on the contrary, the bridge may be made particularly narrow in order to effect a very strong heating, and the substance to be heated and which may be badly, yet noticeably conductive may be arranged outside the anode across bridge 3, thus being without conductive connection with the anode and being heated merely by heat radiation from bridge 3.

The element 4 may be made very be a piece ofmagnesium.

or some other suitable getter substance. For the dispersal of getter substances an embodiment like that on Fig. 3 is particularly appropriate. By giving the getter substance 4 proper dimensions and by arranging it at a correct distance from anode 2 we may produce the result that in the manufacture of the V valve the dispersal of the magnesium takes place only after the outgassing of the metal elements.

Whilst the arrangement according to my 1nvention as shown .in Fig. 2 is preferred for the dispersal of a getter substance, the arrangement according to Fig. 1 is suitable in the firstplace for-the production of a high emission cathode.

There is,'however, no objection to arranging the substance to be dispersed as getter substance immediately on the outer surface of the anode. "In the exemplary embodiment of Fig. 2, moreover also, mica strips 5 may be inserted in slot.2.

- W hatsoever may be the embodiment of my invention, the fundamental principleof it is always, to determine the distribution of eddy current lines in a metal conductor by a ce'r tain shape in such a way that at one or several places the temperature produced by the eddy currents is higher than that at other places.

I claim:

1. A vacuum tube-comprising an electrode system consisting of a cathode, a grid and a cylindrical anode, lead-in wires .for the system, an eddy current arrangement outside the tube consisting of a high frequency current coil for heating the anode at a destined place to a higher temperature than at neighbouring places the anode being slit along a line across saidplace. r

2. A vacuum tube comprising an electrode system consisting of a cathode, a grid and a cylindrical anode, lead-in wires for the'system, an eddy current arrangement outside the tube consisting of a high frequency current coil for heating the anodeat a destined place to a higher'te'mperature than atneighbouring places the anode being slit along a line across said place and non-conductive substances arranged at said place these non-conductive substances being scattered. A

3. A vacuum tube comprising an electrode system consisting of a cathode, a grid and a cylindrical anode, lead-in wires for the sys: tem, an eddy current arrangement outside the; tube consisting of a high frequency'current coil for heating the anode at a destined place to a higher temperature than at neighbouring 7 places the anode being slit along aline across said place and a reaction mixture arranged at said place this reaction mixture being scat tered and precipitated at the surface of the cathode as a highly emissive layer;

4. A vacuum tube comprising an electrode system consisting of a cathode, a grid and a cylindrical anode, lead-in wires for the sys-' tem, an eddy current arrangement outside the tube consisting of a high frequency current coil for heating the anode, a lozenge of barium oxide and silicon attached to the inner surface of the anode in the middle of a shell line, the anode being slitfrom both ends along said shell line.

5. A Vacuum tube comprising an electrode system consisting of a cathode, a grid and a cylindrical anode, lead-in Wires for the sys tem, an eddy current arrangement outside the tube consisting of a high frequency current coil for heating the anode, a lozenge of barium oxide and silicon attached to theinner surface of the anode in the middle of a shell line, the anode being slit from both ends along said shell line, and mica sheets inserted in these slots of the anode.

In testimony whereof I have afixed my signature. BERNHARD LOEVVE,

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