US2512619A - Electron discharge device - Google Patents

Description

June 27, 1950 D. v. EDWARDS ETAL 2,512,519

4 ELECTRON DISCHARGE DEVICE Filed Aug. 21, '1947' 3 Sheets-Sheet l Flak Z.

Summers DY Edwards and W. G-Br'own.

MMM

Their Cmorneg D. v. EDWARDS ETAL 2,512,619

ELECTRON DISCHARGE DEVICE June 27, 1950 3 Sheets-Sheet 2 Filed Aug. 21, 1947 lvllllllllllllll 6 3nvcntor DAV Edwards and W.G.Br own u Their Gttorneg June 27, 1950 p v EDWARDS ETAL 2,512,619

ELECTRON DISCHARGE DEVICE Filed Aug. 21, 1947 3 Sheets-Sheet 3 Snncutors DVEdwcLr'ds and WGBr'own Their (momeg Patented June 27, 1950 ELECTRON DISCHARGE DEVICE Donald V. Edwards, Montclair, and Warren G. Brown, West Englewood, N. J., assignorsto Electrons, Incorporated, Newark, N. J., a corporation of Delaware Application August 21, 1947, Serial No. 789,876

I 19 Claims. (Cl. -250-2'l.5)

. 1 This invention relates to hard vacuum electro discharge tubes, and more particularly to such tubes of the triode type for use in cross-magnetizing magnetic fields and capable of providing relatively large anode current for power oscillators, inverters and the like.

In one type of hard vacuum triode, such as disclosed for example in the prior application of J. H. Burnett, Ser. No; 647,007, filed February 12, 1946, and termed for convenience a magnatriode, the thermionic emissive cathode, control element or grid, and the anode or plate characteristic of the typical triode are specially organized and disposed in a strong cross-magnetizing magnetic field, so that relatively high positive potentials may be applied to the control element or grid and obtain large anode currents without appreciable electron current to said control element.

The primary object of this invention is to provide a structural organization and arrangement of parts for a magnatriode of this type, which will establish and maintain under the operating conditions of temperature and the like, the desired space relationship of the tube elements, and also afiord appropriate areas of the cathode emissive surfaces, control elements and anodes for relatively large anode currents within over-all dimensions suitable for providing efilciently a strong magnetic field through the tube.

Various other objects, attributes, and advantages of this invention will be in part apparent, and in part pointed out as the description progresses.

By way of general explanation, and without attempting to define the nature and scope of this invention, it is proposed to support a plurality of narrow elongated flat grid bars in parallel relation with a plurality of filamentary cathodes, one between each pair of grid bars, between the opposing surfaces of an enclosing anode, all insuch a manner to permit expansion of the grid bars and cathodes at the operating temperatures without material distortion of their space relation: to maintain an endwise tension on the cathodes when heated to cooperate with the cross section of the cathodes to resist their displacement by a fiow of heating current in them while in the magnetic field, and to employ simple expedients for mounting and supporting the parts in the desired space relationship,- using insulated elements required to withstand the cathode heating voltage only. This is merely .a' general explanatory summary of some of the significant features of the invention; and the significance of these features, and various other structural characteristics of the invention will appear hereinafter.

The accompanying drawings illustrate one specific and typical embodiment of the invention,

certain parts being illustrated in a somewhat schematic and diagrammatic fashion, more with- Fig. 2 is a fragmentary and diagrammatic view for explanatory purposes of a transverse section of what may be termed an elemental unit of the magnatriode type of tube.

Fig. 3 is one view of the general organization of the tube of this invention, in the form of a longitudinal section through the tube, with part of the anode broken away.

Fig. 4 is another longitudinal section through the tube in another plane along the line 4-4 indicated in Fig. 3.

Figs. 5 and 6 are two transverse sections through the tube of Figs. 3 and 4 along the lines 5-5 and 6--6 respectively in Fig. 3.

Figs. '7 and 8 are fragmentary enlarged views showing certain details of construction for the anchorage of the ends of the cathodes and the type of cathode insulators preferably employed.

Before discussing in detail the structural features of the embodiment of the invention shown, it wduld appear to be expedient to consider the general organization and functions of what may be termed an elemental unit of the magnatriode type of tube, as illustrated in Fig. 2. Such elemental magnatriode unit, which in efiect is the basisfor the tube structure of this invention, comprises a suitable thermionic emissive cathode C of an elongated or filamentary form, which.

is disposed between two parallel anodes A, A and two elongated grid bars G, G as indicated in Fig. 2, it being assumed that the cathode C, anodes A, A and grid bars G, G shown in cross section will have the appropriate length. This organization of tube elements, within'a suitable evacuated envelope (not shown), is disposed in a strong uni-directional magnetic'field, such as provided between the pole pieces designated N and S of a permanent magnet or equivalent Briefly considering the purpose and advantages of this arrangement of tube elements in a magnetic field, it is contemplated that the cathode C will be capable of emitting a surplus of electrons for the operating voltages, so that the anode current is space charge limited. The potentials on the grid bars G, G serve to supplement or neutralize this space charge and control the electron current from the cathode to the anodes A, A In this connection, it can be seen that negative potentials on the grid bars G, (3- tend to reduce the anode current, and it sufliciently large will cut otf anode current, while positive potentials will act to neutralize the effect oi! the space charge to increase the anode current, and also tend to increase the potential at the cathode surface to draw more electrons from the cathode. The magnetic field, indicated bythe arrow H, which is a cross-magnetizing field with respect to the cathode, may be said to have in general the effect of converging or focusing the electrons leaving the cathodes into streams or beams, such as indicated by dotted lines 5 in Fig. 2, this focusing action being in accordance with the well known principles relating to the movement of electrons in magnetic fields.

Assuming a magnetic field otthe appropriate strength with respect to the tube elements and voltages involved, a relatively high positive potential may be applied to the grid bars G, G and result in large anode currents, without having electron current to the grid and grid losses characteristlc of the usual type of triode, because the magnetic field acts to confine the stream of electronspassing from the cathode to the anodes to paths which miss or escape the grid barsin spite of the positive potential thereon.

The use of such an arrangement 01' tube elements in a cross-magnetizing field, in the manner characteristic of the magnatriode type oi. tube and schematically illustrated in Fig. 2, affords operating characteristics for tubes 01' the hard vacuum triode type, which may be advantageously employed in various applications of triodes, such as amplifiers, power oscillators, inverters and the like; but since the particular use or application 01 this type of tube is not material to this invention, and forms the subject matter of other applications, it is not necessary to discuss further the operating characteristics and advantages of the magnatriode. Also, the magnatriode type of tube is disclosed and claimed in other applications such as that of J H. Burnett above mentioned; and no claim is made herein to the basic features of such a tube and various structural characteristics disclosed and claimed in these other applications.

For a tube having the features of the elemental form of magnatriode illustrated in Fig. 2, which is capable of providing large anode currents and utilizing high voltages for power purposes and the like, it is desirable-to increase the eflective areas of the cathode, anodes and grid bars of the elemental unit, while maintaining the desired relatively close space relationship of these tube elements under the operating conditions oi temperature and the like. There are various requirements to be satisfied for such a, power tube structure. Among other things, it is desirable that the tube should have over-all dimensions 4 suitable for use in small airgaps of magnetic circuits, so that a strong magnetic field may be obtained from the magneto-motive-force employed, such as from a permanent magnet or the like. During operation of the tube, the cathodes and grid bars tend to assume relatively high temperatures in such a compact assembly; and appropriate expedients have to be adopted for mounting and supporting these elements to permit their elongation and expansion without materially affecting the relatively close relationship desirable. Also, in this type of tube the cathode is subjected'to a sidewise bending or displacing force due to the reaction of the magnetic field in which the tube is used and the magnetic field created by the current flowing in the cathode; and it is desirable to employ, in addition to a cross section suitable to resist such bending force, a supporting arrangement which will serve to maintain an endwise tension on the cathode after it is heated. In addition to these requirements typical of a tube of this type, it is desirable to provide forms of support and electrical isolation of the various parts in the desired close relationship, in a manner which will permit the use of high voltages. More particularly, where insulators are employed to obtain the desired space relationship of parts, it is desirable that these insulators be subjected to the lower voltages involved, such as the cathode heating voltage, and should also be located so as to keep relatively cool during the operation of the tube.

After this brief summary of some of the problems sought to be solved by this invention, consideration may be given to the structural features of the specific embodiment of the invention illustrated. Referring to Fig. 1, it is contemplated that the tube of this invention, indicated generally at T, will be disposed in the airgap of a magnetic circuit having a suitable source of magneto-motive-force, such as a permanent magnet as indicated in Fig. 1. In the particular arrangement shown in outline in Fig. 1, which of course is merely typical, the permanent magnet comprises two curved arms or legs 6, preferably circular in cross section, of a suitable permanent magnet material, such as the alloy commonly called alnico. The lower ends of these curved arms 6, which are of course magnetized in accordance with recognized practice, are attached to a soft iron base or back yoke 1 in a suitable manner, such as by' screws or bolts (not shown) threaded into inserts in the permanent magnet material. rectangular shape are fastened in a similar manner to the upper ends of the permanent magnet arms 6, with an airgap as small as the dimensions of tube T will permit. The tube T is disposed in the airgap between these pole pieces 8 of the permanent magnet, such that the magnetic lines 01' force act in relation to the grid bars and anodes of the tube as indicated in Fig.- 2. As illustrated, it is assumed that this tube T will be supported in an upright position by a suitable base and socket, such as generally indicated in the outline at 9, mounted on the back yoke I of the magnet. This of course is merely one of the various arrangements that may be employed. For some applications it may be expedient to immerge the tube T and associated parts in oil for heat dissipation, or provide forced draft air cooling in any one of the well known manners not material to the present invention.

It will be evident that, to obtain a strong magnetic field through the tube T for a given Soit iron pole pieces 8 of a general size of permanent magnet, the airgap should be short; and for this reason the tube elements are organized and arranged and enclosed in an envelope of relatively large width and length, but relatively thin and narrow in its thickness, so as to have dimensions suitable for disposition in a short airgap between the pole pieces 8 of substantial area.

Referring to Figs. 3 and 4, the tube of this invention has a suitable envelope E assumed to be of glass-in the particular structure illustrated. This envelope has a length and width somewhat larger than the areas of the pole pieces of the magnetic circuit for the tube, as shown in Fig. 3, but is relatively thin or narrow, as shown in Fig. 4, to conform with the length of the airgap between these pole pieces. The side walls of the envelope E are straight longitudinally of the tube, but are curved transversely to give a generally elliptical cross section, as shown in Figs. 5 and 6, so that the walls of the envelope will have the necessary strength to resist pressure when exhausted. I

Generally speaking, the tube structure of this invention comprises two of the elemental magnatriode units shown in Fig. 2 arranged side by side. There are three grid bars GI, G2 and G3 arranged in parallel relation at substantially equal spaced intervals; and this assembly of grid bars is supported from the envelope E by a single supporting rod or post I2 sealed in a flat press I3 at the bottom of the envelope E in accordance with the usual practice, using the appropriate metal where this lead-in and supporting element passes through the glass to afiord a gas-tight seal. These grid bars are narrow flat strips" formed from sheet stock of suitable thickness with longitudinal flanges to give a channel cross section for lateral stifiness (see Fig. 6). These grid bars may also be provided with longitudinal corrugations (not shown) if desired. The material for these grid bars should be non-magnetic; and for many applications, it is desirable to employ a surface oxidized or otherwise treated toreduce the tendency to become emissive at the operating temperature. Tantalum, molybdenum, nichrome or stainless steel are typical materials suitable for the grid bars, the particular material used being of course dependent upon rating and other characteristics of the tube.

The middle grid bar G2 is formed of two strips with their edge flanges overlapped and welded at their ends in a substantially equally spaced.

parallel relation from a center supporting'post I2, and that the flexible or-yieldable connections I4, I5 for the ends of these grid bars permit them to expand lengthwise individually under changes in temperature, without materially changing their relationship to each other or other parts of the tube.

There are two filamentary or elongated cathodes CI and C2 in the tube structure of this invention which respectively extend longitudinally between an adjacent pair of grid bars GI, G2 and G2 and G3, parallel with'the surfaces of these grid bars and spaced at substantially equal distances therefrom. As shown, these cathodes CI and C2 are in the form of flattened tubes disposed edgewise to' the grid bars (see Fig. 6) so as to have a cross section for resisting bending sidewise toward these grid bars, due to what may betermed the motor action characteristic of the magnatriode type of tube. For example, referring to the elemental tube unit of Fig. 2, it can be seen that the cathode C, when heated by current in the usual way, is ineffect a wire carrying current disposed in a magnetic field acting in the direction indicated by the arrow H; and in the same way that any wire carrying current in a magnetic field has a force exerted thereon, a force is exerted sideways upon this cathode C, inone direction or the other dependent upon the direction of flow of current tubular form disposed edgewise to the grid bar together; as shown in Fig. 6, and these strips are preferablyarranged to fit closely around the grid supported post I2 and are welded to this post at some intermediate point in their length. This affords a substantial support for the middle grid bar G2, and yet permits it to expand lengthwise when heated, Theother grid bars GI and G3 are connected at their upper and-lower ends by flexible cross connectors I4, I5 to the ends of the center grid bar G2, such connections leaving openings as shown in Figs. 5 and 6 for the cathodes CI, C2. As shown, each of these cross connectors I4, I5 comprises two additional angle pieces I4 I5 having vertical legs welded to the two strips respectively of the middle grid bar .G2, and their horizontal legs welded to the conas shown in Fig. 6 has its metal disposed in a cross section suitable for resisting this bending force due to motor action. It is desirable that they cathode CI. and C2 should effectively resist this motor action, otherwise the uniform space relation of thecathode to the grid bars is disturbed, and the operating characteristics of the tube may be adversely affected. Also, when the cathode is heated by an alternating current, as it is usually most expedient, this motor action tends to vibrate the cathode, and not only affect the operating characteristics of the tube, but also tend to weaken the cathode at its emissive temperature on account of metal fatigue.

In the particular arrangement illustrated, it is assumed that cathodes CI and C2 are tubes of nickel which are flattened, and then coated with a suitable emissive coating, preferably of the barium oxide type, such as disclosed for example in the prior patent to D, V, Edwards et al., No. 1,- 985,855, dated December 25, 1934. However, a single strip of tungsten, or thoriated tungsten, may be employed for the cathodes CI and C2.

In addition to the use of a cathode of a cross section suitablefor resisting the motor action above discussed, it is also desirable, on account of the limitations in the cross sectional area of the metal that can be advantageously employed, to provide a mounting support for these cathodes which will maintain tension lengthwise of these cathodes, after they are heated to the emissive temperature. Among other things, this endwise pull upon the cathodes prevents the motor action from causing sidewise displacement by warping or twisting the cathodes.

The structure illustrated for supporting the cathodes CI and C2 comprises two supporting rods 20 sealed in the stem I3 of the envelope E, and extending outside of this envelope through the usual gas-tight seals to afford external connections for the cathodes and their heating circuit.

enlarged or deformed, as indicated'at 23 in Fig.'

8, bywelding or the like, at points under the lower ends of these insulators, so that their downward movement is limited. Metallic strips 25, constituting what may be termed a cathode header, are formed and welded together to extend between the insulators 22, and have rings or collars 25 as shown in Fig. 5, which surround these insulating tubes 22 with a close but slidable fit thereon. The upper ends of these insulators 22 are formed with shoulders which support a cross member 26; and this cross member 26 is connected to the cathode header by a resilient element 2! (see Fig, 3), which serves to exert an upward pull on the cathode header 25 and apply to the cathodes Cl and C2 the desired tension when heated.

This resilient element 21 may be a, spirally wound wire 'of tungsten, molybdenum or like material, which after being subjected to a baking and de-gassing procedure, is further deformed to give the desired tension, and then'attached to the cross member 28 and the cathode header 2'! by welding or mechanical interconnection of parts. For certain types of tubes, it may be expedient to employ springs of steatite or quartz, or otherwise adopt materials and practices of the art to provide a resilient element capable of giving the desired tension'after the tube assembly is subjected to the appropriate procedure for activation of the cathodes and de-gassing the parts.

The two cathodes Cl and C2 are welded at their upper ends to the cathode header 25. For this purpose, the ends of these tubes may be flattened, and an additional piece employed to form a sandwich weld and facilitate welding operation, as indicated in Fig. 7. The lower ends of the two cathodes Cl and C2 are welded respectively to-separate piices or brackets ii and 32, which in turn are welded to the supporting rods 20.

With this arrangement, it can be seen that the heating current supplied to the cathode supporting rods 20, will flow through the lengths of the cathodes Cl and C2 in series. For example, the

' heating current may flow upward in the cathode Cl and downward in the other cathode C2, the cathode header 25 constituting an electrical connection between the upper ends of these cathodes. The insulating tubes 22 serve to electrically isolate the cathode header 25 and the upper ends of the cathodes Cl and C2, from the supporting rods 20, to which the lowerends of these cathodes are attached. It can be seen that the only voltage applied across these insulators 22 is that of the heating circuit for the cathodes. 'Also, these insulators 22, as well as the resilient element 21, are located in the upper end of th tube somewhat remote from the high temperature area of the tube. The anode A for the tube structure of this invention preferably comprises a sheet of tantalum, molybdenum or similar metal of a width corresponding approximately with the lengths or the gridbars and cathodes, which is bent or rolled and 8 welded together, as indicated at 35 in Pig. 5, into a tubular form having an outside dimension slightly less than the inner walls of the tube envelope E. This anode A is held in place and principally supported by engagement with the walls of the envelope E, but is maintained out of direct contact with the glass walls of the envelope for the greater part of its area, and except for some widely separated points of contact of limited area suitable for affording the desired friction with the envelope walls to hold the anode in place. In the arrangement shown, a filament or wire 35 of a suitable heat resistant material is wrapped around the anode A in a number of turns, with these turns welded to the anode at a number of points. One type of spacing element suitable for this purpose comprises a wire of tungsten or the like coated with aluminum oxide or like heat resistent material. Another expedient is to wind around the anode A a round filament or strip formed of closely wound turns of fine wire. Other expedients, in the way of spaced protuberances formed in the anode itself, or separator pieces or strips attached to the outer surface of the anode A may be employed to accomplish a particular result. The purpose of these expedients just described is to hold the sheet metal anode A in place by its frictional engagement with the inner walls of the glass envelope E, but maintain such a space between-the greater part of the surface of this anode and these glass walls that heat will be dissipated from the anode by radiation through. these walls, rather than by conduction, so that the anode may be operated at a high temperature without overheating the glass 'walls of the envelope E.

The necessary external electrical connection to the anode A may be made in any convenient manner, such as by a rod 31 welded thereto and in turn welded to a lead-in wire 38 sealed in the envelope in the usual way at its upper end opposite the press li supporting the grid bars and cathodes. Such location of the lead-in connection for the anode at the opposite end of the envelope from the lead-in connections for the cathode enables high anode voltages to be empioyed.

Various expedients may be employed to assemble the tube structure shown. For the particular type of envelope and seals illustrated, it is contemplated that a lead-in connection. 38 of sumcient length will be threaded through the opening for its seal lengthwise of the envelope E prior to forming of the press I! at the lower end of this envelope. After the weld between the anode con-.

nection I1 and this lead-in wire 38 is made, the anode A may he slipped into the envelope E, and the seal ior the lead-in wire 38 formed. It is contemplated that the anode A will be suiliciently like the envelope E in dimensions that the spacing elements, such as the wire 35 wrapped around this envelope, will contact with the walls of the envelope at a suflicient number of points to hold it in place. In this connection, it is assumed that the wire 35 will be loosely wrapped around the envelope and welded thereto at various points to provide turns yieldable for portions of their length, so as to afford the desired supporting contact between such portions of the wire 35 and the walls of the envelope. If this spacing element is a strand or strip of finely coiled wire, the resiliency of the coils assist in providing the desired frictional engagement.

The grid bars and cathodes are mounted and s assembled on the supporting rods l2 and a, the

- 9 welding of the brackets SI and 32 for the cathode being made after the desired tension for the spring 21 has been established. This assembly of grid bars and cathodes on the supporting rods l2 and 20 may then be inserted within the anode A inside of the envelope E; and after alignment of the parts, and while the rods l2 and 20 are held in a suitable clamping device, the glass of the envelope E may be softened and the press I! formed by a die block or the like in accordance with recognized practice.

After the assembly and mounting of the tube has been completed, it is subjectedto the appropriate procedure for thorough out-gassing, activation of the cathodes and evacuation, using for this purpose an exhaust tube indicated at 4, to be later sealed oil in the usual way. Such exhaust and cathode activation procedure to establish a high vacuum may be in accordance with recognized and established practice, without any special or unusual steps. It is generally expedient to provide a preliminary de-gassing by heating in a vacuum system the wire used for forming the spring 21; and if desired, such preliminary de-gassing can be applied'to advantage to some of the other parts, thereby avoiding the need for heating such parts to as high a temperature for as long a time during the final operation of outgassing and evacuating the tube. In this connection, it will be noted that the anode is a continuous tube, and hence may be readily heated to the appropriate out-gassing temperature by induction heating or bombing, while other parts,

such as the insulators 22 and spring 21; are kept at lower temperatures.

From the foregoin explanation in connection .assembly afiords the desired stability and the spaced relationship of the essential parts under operating conditions, together with an electrical isolation or insulation between the electrodes permitting the use of high voltages.

It should be understood that the specific construction/ and arrangement of parts shown and described are merely typical or representative of the invention and are susceptible to various changes without altering their purposes and functions. For example, instead of sealing the grid bar and cathode supporting rods I 2 and 20 into the press l3 of the envelope E after these grid bars and cathodes have been mounted on these supporting rods, these rods may be sealed in a separate stem mount, the grid bars and cathodes mounted and ali ned on the rods, and then the stem mount fused to thewalls of the envelope E,

in accordance with well known practice. This is merely one example of how the structure illustrated may be changed or adapted in accordance with the skill and practices of the art as may be expedient; and it should be understood that various modifications, adaptations and additions may -10 tiall equally spaced parallel relation and connected at their ends by flexible members with said grid supporting post, a. plurality of elongated thermionic emissive cathodes one between each adjacent pair of grid bars and extending substantially parallel therewith, means supporting said cathodes at their ends and maintaining an endwise tension thereon when heated, and an anode around said grid bars and cathodes, said supporting means for said cathodes including insulators located outside of said anode electrically isolating the opposite ends of said cathodes to permit heating current to be conducted lengthwise of said cathodes in opposite directions.

2. An electron discharge tube of the character described comprising, a box-like anode, a multicellular structure of fiat elongated grid bars and filamentary cathodes arranged alternately in substantially parallel relation inside and between opposing surfaces of said anode, a plurality of parallel supporting rods for said cathodes, a cathode header resiliently supportedby said rods near one end thereof and insulated therefrom, said cathodes being secured at one end to said header at spaced intervals, means connected with said supporting rods for anchoring thereto the other ends of said cathodes, and other supporting means cooperating with the ends of said grid bars to position them in a predetermined relation to said cathodes and anode.

3. An electron discharge tube of the character described for use in a cross-magnetizing magsaid means including a movable cathode header secured to one end of all of said cathodes and resilient means acting on said header to provide heated.

be made with respect to the specific embodiment 4. An electron discharge tube of the character described comprising, a plurality of substantially equally spaced filamentary cathodes disposed in a common plane between opposing anode surfaces, a pair of supports for said cathodes, means anchoring said cathodes separately at one end to said supports, a cathode header secured to the other ends of said cathodes, insulators on said supports supporting the ends of said header to permit movement thereof lengthwise of the cathodes, and means including a resilient element between said insulators and said header for exerting an endwise pull on the cathodes when heated.

.5. An electron discharge triode of the character described for use in eras-magnetizing fields, comprising a plurality of fiat elongated grid bars arranged at substantially equally spaced intervals in parallel relation, a plurality of supporting rods outside of said grid bars and extending beyond the ends thereof, a cathode header extending between said supporting rods adjacent one end of said grid bars, means including insulating elements slidably supporting said cathode header on said supporting rods, a plurality of filamentary thermionic emissive cathodes disposed one between each adjacent pair of grid bars and secured at one end to said header, means anchoring the other auasre' l1 ends of said cathodes tosaidsnpportingrodaand means including a resilient element interposed between said headerandsaidsupportingrodsfor exerting'tensiononsaidheadertoprovidean endwise pull onsaidcathodeswhenheated.

dAhardvacuumiriodeformeinacrossmagnetisingmagncticiieldcomprisingthreeelongated iiat grid bars arranged at mbstantially equally spaced intervals in parallel relation, two

vfilamentarycathodesextendinglengthwisehe- 12 athodes andeiongatedflatgridbarsdisposedin parallelrelationwithinsaid anode,andmeans attheotherendofsaidenvelopeprovidingsup- 7.Atubestructureofthecharacterdescrlbed for use in cross-magnetizing magnetic fields comprising, a box-like anode having opposing parallel surfaces disposed in planes parallel with the lines of force of the magnetic field, a plurality of narrowelongatedflatgridbarsarrangedinparaliel relation between said anode surfaces at substantially equally spaced intervals, a plurality'of filamentary cathodes of flattened nickel tubing coated with a thermionic emissive coating and disposed edgewise to said anode surfaces, means supporting said cathodes one between each adjacent pair of said grld bars to extend lengthwise thereof throughout their length, said means in cludinga metallic header to which said cathodes areconnectedatoneendandaresilientelement acting on said header for maintaining tension on said cathodes.

8. Atube structureotthechamterdescribed, comprising with a plurality of spaced parallel filamentary thermionic emissive cathodes, a plurality of elongated grid bars disposed in parallel relation at substantially equally spaced intervals on oppodte sides of said cathodes, a singlesupporting rod for said grid bars extending longitudinally thereof and attached to an intermediate grid bar, andresilient supports connecting together said gridbarsatthelrendssaidsupporishavmg openings for the cathodes,

9. An electron discharge tube of the character decribed comprising, a plurality of filamentary thermionic emissive cathodes disposed in a substantially equally spaced parallel relation in a common plane between opposing anode surfaces, and a plurality of elongated flat grid bars disposed in parallel relation .at substantially equal distancesbetweensaidcathodeasaidgrldbars being formed with flanges for lateral stillness, flexible elements connecting said grid bars together at their ends with openings for said cathports and lead-in connections for said cathodes 11. Anelecirondischargetubeofthetypedescribed comm-icing, a plurality of filamentary thermionic emissive cathodes and list elong ted rfii bars arranged alternately in parallel relaticn, a glass envelope, means providing separate lead-in connections and supports for said grid bars and cathodes from one end of said envelope,

a sheet metal anode surrounding said grid bars andcathodesandsmmortedbythewallsofthe envelope but separated therefrom by heat resistant spacing elements. and a lead-in connecflonforsaidanodeattheotherendofsaid envelope.

12. An electron discharge tube of the character described comprising, a plurality of cathodes and grid'bars in a multicellular assembly, a glass envelope of general elliptical cross section, a. sheet .1

metal anode of non-magnetic material surrounding said assembly, of cathodes and grid bars within said envelope, said anode being closely spaced to the inside sin-fac of said envelope, and heat resistant elements attached to the outer surface of said anode and contacting with the walls of said glass envelope at a plurality of points to maintain said anode in position within the envelope, and a lead-in connection for said anode extending through a gas-tight seal in said envelope.

13. An electron discharge tube of the characacter dwcribed, comprising a flattened glassenvelope of general elliptical cross section, an anode made of a thin sheet of non-magnetic metal and shaped to conform with the inner surface of said envelope, and a plurality of turns of a heat insulated wire around said anode contacting with v the surface of said envelope to provide a support for said anode while maintaining said anode out of contact with the walls of said envelope for a large part of its area to permit direct radiation of heat from the anode through the walls of the envelope.

14. An electron discharge tube of the character described for use in a magnetic field acting substantially at right angles to the axis of the cathode of the tube comprising, an evacuated envelope, a plurality of filamentary thermionic emissive cathodes and flat elongated grid bars arranged alternately in parallel relation with the said envelope, a pair of parallel supporting posts sealed in one end of said envelope and constituting supports and lead-in connections for said cathodes, a pair of steatite insulators on said posts near one end,a cathode header to which odes,andmeanssupportingsaidgridbars,said

eralellipticalcrosssectimasheetmctal anode within said envelope supported by thejwalls thereof but separated from said wallsfby heat resistant elements, a lead-in connection for said anode at one end of said envelope. at multicellunctic field comprising, a glass envelope of gensaid cathodes are connected at one end, said header being slidably mounted on said insulators for movement lmgthwise of the cathodes, said cathodes being connected at their other ends to sail posts, and resilient means cooperating with saidpostsandsaidheadertoexertan endwise pull on said cathodes.

15. An electron discharge tube of the character described comprising, a multicellular assembly of a plurality of filamentary cathodes and elongatedgrid bars arranged alternately in parallel relation, a single su rting rod for said grid bars extending longitudinally thereof and attached to an intermediate grid bar, means connectingsaidgridbarstogetherattheirendsto permit endwise expulsion thereof, and means in- -larstructureofiiiammtarythermionicemissive 7i clodhigapah-ofsupportingpostsoutsideofsaid 13 grid bars and supporting said cathodes at their ends.

16. An electron discharge tube comprising three elongated grid elements disposed at substantially equal distances in parallel relation, a pair of filamentary cathodes extending lengthwise of said grid elements at substantially equal distances therefrom, a supporting rod for said grid elements, and a pair of supporting rods and insulators thereon for supporting said cathodes and connecting them in series for heating current supplied to said pair of supporting rods.

17. An electron discharge tube comprising a glass envelope of flattened cross-section with two of its walls in a relatively close spaced parallel relation, an assembly of a plurality of filamentary cathodes and elongated grid elements in parallel relation, an anode around said assembly having its outer surface closely spaced to the inner walls of said envelopes, and spacing elements attached to the outer surface of said anodes and having frictional contact with the envelope walls over a limited portion of the anode surface for supporting said anode by said envelope while permitting heat from the anode to be dissipated largely by radiation through the envelope walls.

18. A controllable electron discharge tube of the hard vacuum type for use in a cross magnetizing magnetic field comprising, an envelope with a stem mount at one end, a multicellular assembly of a pair of filamentary cathodes and a plurality of elongated grid bars arranged alternately in substantially equally spaced parallel relation, a single supporting post supporting said grid bars and sealed in said stem mount of the envelope, a pair of cathode supporting rods extending lengthwise of said assembly and sealed in said stem mount in the envelope, said cathodes being connected at one end separately to said rods, an electrical connection between said cathodes at their other ends, and means including heat resistant insulating material connected with said rods and acting to slideably support said cathodes at their electrically connected ends.

19. A tube structure for use in a cross magnetizing magnetic field comprising, a box-like anode, an assembly of elongated grid bars and filamentary cathodes arranged alternately in substantially equally spaced parallel relation inside said anode with said grid bars edgewise to opposing surfaces of said anode, an envelope of flattened cross-section with two of its sidewalls closely spaced to said opposing surfaces of said anode, a single grid supporting post sealed in one end of said envelope and attached to one of said grid bars, flexible means connecting said grid bars at their ends to permit independent endwise expansion, a pair of cathode supporting rods sealed in said end of the envelope, and means supporting said cathodes on said rods and permitting heating current to be conducted from said rods lengthwise through th cathodes.

DONALD V. EDWARDS. WARREN G. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,748,175 Holden Feb. 25, 1930 1,754,120 Robinson Apr. 8, 1930 2,221,743 Wagner Nov. 12, 1940 2,248,712 Litton July 8, 1941 2,332,977 Skellett Oct. 26, 1943

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