US1976553A - Electron discharge tube - Google Patents

Description

Oct. 9, 1934. w. T. GIBSON ET AL ELECTRON DISCHARGE TUBE Filed Feb. 5. 1932 Q w r GIBSON WVENTORSA H. BOUL ESTREAU A T TORNE V Patented Oct. 9,, 1934 ravage? ELECTRON DISCHARGE TUBE William T. Gibson and Antoine. H. ,Boulestreau, Paris, France, assignors to, Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application February 3, 1932,-Serial No. 590539 4 In France April 27,1931

Claims. (Cl. 250-275) lhe present invention relates to electron discharge tubes and particularly to high .power tubes.

provements in the various elements forming an electron discharge tube and new arrangements.

of the different elements so as to produce an improved tube having a large number. of desirable characteristics. l I 110.:. It is well-known that in high power vacuum 'tubesit is necessary for the spacing of the various electrodes to be relatively small so that the tubes may, have the'desired electrical characteristics. i5,the cathode andqgrid are very near, short circuitsare often produced between the filament and the grid which disrupt operationtof the device. It has been found thatamong thefrequent causes of such. short circuits there are, on-the 29jone hand, theunequal expansion. of various ele- Y merits-of, the tube, for example, the filament expanding more than the grid, Fand on the other hand, electrodynamic forces develop between the variousconductors forming thetcathode. These uelectrodynamic forces in the case of high power tubes are often sufficiently' great. to I separate very considerably :the conductors forming the" cathode, and even sometimes to cause untimely contacts between the elements of the cathode 30. andother elements, of .the tubes An object of .the invention is to providea vacuum. tube particularlyadapted for high pow'er and for, very high frequencies and in which the above disadvantages are eliminated.

'Anotherobject of the invention is to provide-a vacuum tube of the type-mentioned, whichmay be of exact and simple construction-and which can be easily mounted and sealed, for example, by means of a rotary machine. 40 ".Another object of the invention isto provide an improved arrangementof the various elements-- of such a tube permitting, of very great precision in the arrangement and fixing of the elements.

In order to explain .the nature and the various aspects ofthe present invention, a :number of l characteristic features of the .invention will be setforth and it should, of course, be under stood that one vor more of these characteristics maybe employed eithersingly or in combination. Moreover, a vacuum tube comprising the characteristics of the invention will be described'in detail and it should be noted that'in thecourse of the description ofthistube a number of equally important characteristics of theinventionwill be indicated: a.

However,.when the. electrodes such as According to one of the characteristics of the invention, the various elements of an electron discharge tube are arranged symmetrically, for The invention particularly relates .to im example, concentrically, with respect to an'axis which may be established during the mounting' fio T veniently mounted, for example, by a'special rotary machine. J

Another feature of the invention relates-to a vacuum tube comprising a cathode supported by, two tubular concentric conductors also serving "j to supply current'to the cathode and moreover,

a control electrode supported bya tubular con- 10 ductor serving as electrical connection for the V ..control electrode, the cathode and the control 3 electrode being preferably arranged about'the same axis.

.the cathode of a vacuum tube-of the type descrbed is supportedat one end by two tubular concentric conductors serving to supply the current to the cathode, and at the other end, is

supported by means of one or-more metallic rods- 5 3 supported by the tubular conductor serving "as support and electrical connection for the grid, means being provided toapply a well-defined tensioning force-to the metallic rod supporting; '7

the cathode.

According to another characteristic of the invention, the two tubular concentric conductors serving as supports'and-electrical connections for the filaments are fixed on the envelope; of the tubejin the following manner. The outer conductor is sealed to'the vitreous-enveloped the 'tube while-the space between the two concentric tubular grid-support-conductor passes .while 1 0O through the" other portion the two concentric tubular filament-supporting conductors pass. a According to one feature of the inventiomin a vacuum tube of the type described, the filae mentis held under tension by means of a,rod..'

sliding in insulators fixed to the, tubular con-j duct-or which serves both as grid support and' electrical connection for the grid. 3 v

Another characteristic consists in the case'of a filament comprising several strands, in the provi 1'10 According to another feature of the invention, "15

sion of means to equalize the effort, for example, of traction, on each of the strands and to prevent the lateral displacement or harmful distortion of the strands. For this purpose, at one of the ends of the filament, the supporting system employed maybe mounted on a swivel and small balancing rods may or may not be provided.

Another feature of the invention consists of a vacuum tube comprising a tubular anode at each" extremity of which a glass portion may be sealed.

The anode may or may not be provided with a jacket for the circulation of a cooling fluid. One of these portions supports two concentric tubular conductors serving as a support for one of the ends of the cathode and electrical connections for the cathode. sealed to the anode is adapted to support a tubular conductor to which the grid is fixed, this tubular conductor serving to convey the current to the grid and also as a support for one or more rodson which the other end of the filament is fixed. Means may be provided and associated with the rod or rods to maintain the filament stretched.

According :to another feature of the invention, a jacket for the circulation of a'cooling fluid for the tube of thetype described comprises a metallicfmernber approximately concentric with the anode, arranged with respect to the anode so as.

to leave a free space forming a jacket for the circulation of a cooling fluid, the cooling fiuid being conveyed into the jacket by means of an inlet. placed approximately in the middle of the anode and; the removal of the cooling fluid being.

performed by means of twooutlets placed approximately at the two ends of the jacket. Pieces of suitable shape are provided inside the jacket to reduce the section or sections of passage of the cooling fluid in contact with the anode, or on the,

greater portion of the anode and to force the fluid to circulate at high speed in a thin layer so as to insure a maximum exchange of heat between the anode and the cooling fluid.

Other features of. the invention will be, seen on by referringto the following description'based' the attached drawingin which: r Fig. 1 shows a cross-sectional View of a high power vacuum tube employing the characteristics to the tubular conductor'Q and, on the other hand,

of the present invention;

Fig. 2 is a section perpendicular to "theraxis' of the vacuum tube on the line 'A-B of Fig- 1 showing the tubular conductor which acts as aand of the circulation jacket for the cooling fluid; Fig. 4 is aisection perpendicular to theraxis=of the vacuum'tube on the line EF of Fig. 1 show:- ingthe arrangement of a reflector v l Fig; 5 is-a cross-sectional view on the line G.I-I

f Fi Fig.- 6' is apartial crossesectional View on the line .I-rJ of Fig.- 1 showing in detail the arrangement of the rods for conveying current and fixing the cathode on the-concentric supporting conductors; and I I a Figs-L. 7,. 8 andfl are'enlarged views of the articulate support for one end of" the cathode.

Fig. 1 shows a longitudinal section-of an electron discharge tube employing the features of the present invention. 'In a general manner the tube shown in Fig. 1;is.a tube of the double-ended type, thatis to say,.the-ano de is iormedjby-ametallic The other glass portionrent to the cathode and may, in accordance with the drawing, be placed at one end of the vacuum tube, while the tubular conductor serving, among others, to convey current to the grid, is placed at the opposite end of the vacuum tube, that is to say, the latter tubular conductor is supportedby one-of the glass portions'sealed to the anode. It will be noted'that the anode is provided with a jacket for the circulation of cooling fluid of a particular type which will be described hereinafter in detail.

In Fig. 1, the tubular anode is'shown at 1 and .the two glass portions sealed to the ends of the anode 1 are shown at 2 and 2,. The electrical connections. to the cathode, illustrated in the form of filaments. 3', are established by means of two tubular. concentric conductors 4 andt5, sealed to member 6 soldered on the outer tubular conduc 130114. .The tubular conductor 4terminates in a the glass portion .2 .bymeans of aconical metallic serves to close the space comprised between the two tubular conductors. 4 and 5. Finally,'the end .of the conductor '5 is closed by means of a suitablev stopper, such as a copper disc 8, soldered to the conductor5.

he I

The manner in which the filaments are supported fromthe ends of the con- TL. ductors 4 and 5 will be described later in detail.

The current isconveyed to the grid bymeans ofa tubular conductor 9, one end of which is flared to permit sealing of a glass portion 21 thereto.

. The pumping ofthe vacuum'tube maybeperformed by connecting a vacuum pump to the por- I tion 21 and sealing this portion when the. desired degree of vacuum has been obtained. A conical metallic portion 10 is soldered, on the one hand,

sealed to the glass portion 2.. .At one of the 'ex-' tremities of the tubular conductor 9 there is fixed,-

by means of the screw 33, an apertured disc 11 supporting thecontrol or grid electrode of the Y.

tube. The grid is constructed of a molybdenum wire 34, wound .helically, .as shown in Fig. 3, on four'rods 12 fixed on the disc 11. To prevent the relative position of the turns34' from varying,"

suitable means are provided to maintain the turns in position on the rod 12. I

Thecatho'de comprises a'plurality of' filaments 1 3 which are maintainedin position in the follow-''-" ing manner: .On the one hand, the concentric con , ductors 4 and 5 support rods 13 to which the filaments "3 are fixed, forming the cathode. These filaments are held'in position by means of V hooks 14 fixed to a particular'membe'r 151which' will be It will be noted that the disc 11 must be relaforming the cathode may be adjusted to a determined value, a spring 19 may be. provided and associated with the rod 16. Anut'20 whoseposition may be adjusted on a threaded portion-of the rod 16, serves to control the compression of the spring 19 and consequently the tension applied to the filaments 3 forming the cathode. The spring 19 may be formedof a metallic wire which retains its elasticity at high temperatures, for example,

tungsten, so as to maintain the desired tension on the sections of the cathode3. It will be noted that the tubular conductor 9 is provided with a series of holes 21, adapted to reduce the weight. of the member supported bythe glass portion 2, as well as the transmisison of heat from the grid towards the members sealed to the glass.

Z The arrangement-of the blocks of insulating material 17 and 18 is clearly shown in Fig. 2, which is a section of the tube along theline A-,B.

The blocks of insulating material 17 and 18 are fixed in position in the tube 9 by means of a sheath of the shape shown in the drawing. This sheath 35 is kept inside the tubular conductor 9 in the position shown in Fig. 1 by the reaction of'thespring 19; :The blocks 1'7 and 18 are each provided with a groove 38 in which: is'set. the metal of the sheath 35 which fixes the position of the blocks 17 andlB in the sheath. The position of the sheath. in the conductor 9 is fixed by means ofa bossl39 which. is applied to the flared portion of thetubular conductor9. The sheath 35 is provided withan extension serving as an electrostatic screen protecting the metal-glass sealing.

In order that the rod 16 may slide suitably in the insulating blocks 17 and 18, these blocks are each provided with a hole of a slightly larger, di-- ameter' than that of the rod 16 and a sheath formed of the same metal as the rod l6,forexam ple, a wire spiral with touching strands 36 is provided inside the opening so that the friction is .made between two metals of the same nature.

To prevent the helical spiral 36 from turning or being displaced, the ends of the wire forming this spiral may engage the holes 37 provided in the member 17, or any other fixing means may be employed. In Fig. -2 it will be noted that the member. l'7yis providedwith openings 41 which serve, in particular, tofacilitate the pumping of the tube and to lighten this member. 1 V r Special precautions have been taken to pre- 4 vent short circuits between the filaments and the grid under the influence of the considerable electrodynamic forces developed by'the heatingcurrent of the filaments. Figs. '7, 8 and 9 represent the arrangement employed for this purpose. This arrangement, moreover, is shown at 14 and 15in Fig. 1.. Referring particularly to Fig. 7, it will be noted that the rod 16, Fig. 1', is screwed into the member 42to which is'fixed, by means of three stays 43, a similar member 45 having a pin 46 with a spherical head 47. The' spherical head 47 engages the concave portion of an intermediate member 48 having three axles 49, 49 and49. clearly shown in Fig.8. -Each"of the axles carries transversely at its extremity a' rod, su'ch'as 50; at the ends of which are joined two hooks 51 and 52. The-rod 50 may oscillate around'the'axis 49. Inthe hooks 51 and '52. is fixed a bar 53 on which are soldered the filament strands; eachbansuch as 53, supports two filaments such as 3" and 3". A ring 54 passing in the hooks 14 maintains the spacing and the position of the filament strands. This ring is kept inside .the hooks- 14 by small hooks 54' soldered to the. end of the hooks 14. The operation of the. apparatus shown in Figs.

7, 8 and 9 is as follows: The pivot assembly47 and 48 enables'themember' 48 to take up such a position that theefiort of the spring 19 is equally distributed on the axle 49. The rod 15, in turn, equal y distributes between the strands 3 of the filament the effort exercised on the axle49. It may be noted that the extremity of the member 45-is provided with a tapped opening and a slot 55 permitting it to be fixed on'a tool for maintaining the filament in position when the? filament is not yet introduced in the tube and the rod 16 and the'mechanisms 14 and 15 have not contributed to maintain the filament in its definite position.

In order to insure the'cooling of the anode 1, a rpecial'arrangement lof coolingfiuid jacket is provided and illustrated in Fig. 1. Ashas'been seen above, 'theanode 1 may be'constructed by i be flared for a suitable distance so that these" rings may be soldered at 24 to the tube'forming means of 'a special copper. tube of suitable size the anode 1, and at 25 to the outer container 26 of the-cooling fiuidijacket'." This container26 may be suitably constructed by means of.a.- tube concentric with the tubular anode 1. 'The' shape of the outer'con'tainer of the circulating cooling yflui'djacket is clearly shown in Figs. 1 and '3. Al-.

though Fig. 3 shows an embodiment of theouter container of the coolingfiuid' jacket in the' form l of a tube of suitable s'ize, 'it is obvious that this container may be constructed, for example, of two semi cylinders suitably connected. When .the

container'26 is set in place according to Fig. l. T it"will be noted that between the outer surface of the tubular anode 1 and the member 26 there is an empty space permitting circulation of the cooling fluid for the anode lwhi'c'h is brought to a high temperature by electronic bombardment.

#In order that the cooling fluid" may circulate around the anode 1, in the'form of a thin film actuated at high speed, annular members 27 and .28 are'provided and arranged as shown in Figs.

- 1 and 3." Figs. '1' and 3 clearly show the shape and arrangement of these members with respect to theanode 1.' 'Thelmembers 2'7 and 28 are ar- .range'd'so'that a fairly small empty space exists between the interior of these" members andthe outs'ideo'f the anode. ."As this space determines .the thicknessof the layer of cooling fluid. the m'embers 27ian'd 28 may be kept at a: suitable ."d starlcefronitheanode 1 by means-of spacers 29. riveted or solderedto the members 2'7. and

23 3s clearlyi'shown in Fig; 3. The members 29 ;may bexforrned by means ofsmall angleirons coveringamore-or less igreat. lengthof, the membore 27 and 2a. The members: 27 and 2e are by a tube'in one piece, which enablesthe outer part of the Water .jacketto beset in place after the mounting of. the :elements of the vacuum 1 tube.

The tightness of the jacket is obtained simply by means of two annular jointsibetween members 26 and 24 and 26and 23, The circulation of the cooling fluid is-made in the following-- manner: The cooling-fluid,for'example, water,

arrives under pressure through the tube-32. and

is displaced according to" the arrows shownin Fig. 1. The cooling fluid in passing in the relatively narrow annular space between the anode 1 and-the guide members .27 and 28 takes on. a high. speed and rapidly disperses the heat pro-' duced by electronic bombardment. 'It, is con--- sequently possible to'increase the power which .the filaments are regularly arranged at each of may be dissipated in an anode of given dimensions.

the shape of the members 22 and 23, shown on the figure, no fluid circulation'is produced in this space. It will be noted that the cooling fluid is introduced into the jacket 26 approximately in the "middle'while 'theoutlet of :the fluid is at:

both ends'of the jacket 'soas to. reduce the load-1 ing loss and consequently the pressure necessary to obtain'the very'activetcirculation of cooling fluid; It will thus be seen that'in-accordanceiwith the foregoing, the arrangement described comprises'a jacket for the cooling .fluidparticularly adapted for a doubleended tube, and adaptbeing conveyed'to the jacket by means; of atube placedapproximately in themiddle of the: jacket, the'fiuid'beingremoved by means of at leasttwo .outlets placed i'approximately' at opposite ends of thezjacket and means :b'eing provided toinsure the circulation of the cooling fluid in the form of a fine layer of very rapid circulation, so as'to' insure a maximum tra'ns'ferofheat between the anode land the cooling fluid;

' Fig.33 shows a sectionof the tube along line C-D. In Fig. 3 the outer container of the cool--- ing fluid jacket is shown at 26 and the member 27 is designated by the-same reference in Fig. 3 as Fig. 1.

This'figure clearly shows a. screen 56 employed to reflect the'heat radiated from the cathode 3:fr.om the tubular conductors! and 5 and from the glass portion 21.- (This screen consists of the .molybdenumldisc fixed on three of the'rodsfl3 supporting the filaments; vThe openings-provided inth'e I Y I r 3 circular screen 56 for the passag'e of the "three- 9n the "thus festgbhghed The other rods 13 are shown in the-figure at l3':;-13"- ands" 13" The screen 56"is fixed in' position-'onthese' rods by suitable. means, -such 'forexample, as" by means of helicalsprings 57 fixed on the" rods '13.-

In'ord'er'to give mo're rigidity to"the"screen:.56; Ia

molybdenum" ring is fixed by means of'claws'58;

58' and '58' on theperip-hery'of the screen; It will be seen'that'the screen56 is brought to the potential of the three rods 13.; 13" and 13" supporting the filaments. Sincethere is a difference of potential betweenthe two opposite extremities Fig.6 the conductors servingas'filamentsupports The space beyond the guide members 27. and 28 is filled, with cooling'fluid, but in View of conductor 4 by means of block members4', 4

' may be set in position with great precision. a

It will be. noted thatthemember- 27. is formed by means of two semi-cylinders 2'7 and 27' fixedin position bysuitable means, such as clamps 271-,'as is clearly shown in Fig. 3; The four rods supporting the grid areshown atr12 and the six filaments forming the cathode are' shown- Fig. 4 'is a section of Fig. 1 along line E -F.

- of the filaments, it is necessary for thethree other" rods supporting thBLOthBl extremitiesofthe filamentstopass through the screen without making contact therewith becausezin the latter'case the 1 filaments would be short-circflitedL- For this purpose-the screen 56 is provided with openings 131, 13'1 and-l3 '1 whose diameters are greater than the diameters of the supporting rods 'of the fila' .L'V) i V I 7 Figs: 5 and 6 are sections of the tube of Fig. 1

along: lines G'H and I'J, respectively; serving to explain the fixing: of the filament support rods on the'tubular' conductors 4 and 5, which act as supports and-conveycurrent to the filaments. vIn areshown at 4and 5. As has been seen in the description of Fig. 4; the six conductors forming the peaks of a hexagon andfixed to six metallic rods such as"13:and 13"; three of these :rods are connected .to the tubular" conductor 4; 'for texampl'e, and'the'three others are connected to-the other tubular -conductor 5r' Fig. 6 shows-that three filament rods are supported by the tubular -1 O0 and 4 screwedonithe conductor 4. Thero'ds- 131 are'soldere'd tothe arc in the members'4, 4",

4; thecorrespbn'ding rod's arethen placed at 120 'degreesfr'om'each-"other. The three other filament rods' are supported by means of a tri-' angular member-59; Fig; 5, 'and are also 120 ole-' greesfrom each other but the member 59 is arflranged with respect'to' the members 4', '4" and 4 so that each filament supporting. rodformsi an angle of 60"degree's with thefollowingrod or with that immediately preceding it. The member "59 is fixed by means of a screw '60; Fig. 1', on the tubular conductor 5. it will-thus be'seen that I the whole forms'an extremely rigid unitwhich In order toprotect theglasssheath and particularly at the points where the'portions- 2 and 2' are sealedto theanode; metallicelectrostatic screens Gland 62 may be'provided as shown' in Fig."l'I Thef'ree ends of these screens are'turned back so as to form a flange permitting of the-increase ofrigidity of the screen and the decrease Io'fthe intensity'of the electric field'on the'edge' of-the screen and'consequently ofthe possibility- Screens 61 and 62" are also fixed of discharge.- 7 to the ends of the grid, to'limit' the electron dis charge to the cooled portion ofthe anode.

The fabrication of atube such'a's'that' in Fig. 1 maybe carried out inthe following manner:

The concentricfltubular conductors '4' and 5 are assembled with'thefimembers' 4', 4", 4" and 59 i and the corresponding filament-supporting rods;

a rod is thenintroducedinto the tubeand fixed in position'in the conductor 5. At the end of this rodwhich forms a mounting'tool is"'fixed"a'slot"135 '55 of the swivel member l5, servingto' support one of the ends of the filament. The filament istheh fixedin the slot 55 of the member..-l5 so that'the mounting-pf, the filament may berealizedp ,A sufficient tension will. be applied to the. filament by manipulating the nut -20 associated with the- 140 filament and concentric tubular conductors 4; and 5 into the tubegthen screw tlierod lfi. into the .upp erend of the-member 15, and after sealing the tube, to-withdraw the' -rod, serving as a tool anode, means rigidly fixing and spacing the "'5 stran ds ofsaid cathode at one end, supporting means coupled to the strands of said cathode at the other "end, and means includingjarigid universally movable member supporting said secd m n 2; An-electron discharge device comprising an anode, rigidly supported bilateral members, one of said members having a pivot extending therefrom, an intermediate member disposed between I I said bilateral members and rockably supported on said pivot, and a multi-section filament supported by said intermediate member.

3. An electron discharge device comprising an anode, rigidly supported bilateral members, an

intermediate member disposed between said bilateral members, means rockably mounting said intermediate member on one of said bilateral members, radial arms extending from said intermediate member, and a plurality of filament sections 7 carried by said arms.

4. An electron discharge device comprising an anode, rigidly supported bilateral members, an intermediate member yieldingly supported between said bilateral members, radial arms extending from said intermediate member, swinging bars sc -carried by said arms, and uniform lengths of filament joined to the opposite ends of said bars.

5. An electron discharge device comprising an anode, rigidly supported bilateral members positioned in the axis of said anode, an intermediate 35 member yieldingly supported between said bilateral members, swinging bars carried by said intermediate member and extending beyond the edge of said bilateral members, hooks extending from said bars, and a filament section supported by "each hook.

6. An electron discharge device comprising an anode, rigidly supported bilateral members positioned in the axis of said anode, an intermediate member yieldingly supported between said bilat- 4'5" eral members, swinging bars extending from said intermediate member, hooks extending from the ends of said bars, parallel filament sections supported by said hooks, and a spacing member associated with said hooks.

'7. An electron discharge device comprising an anode, rigidly supported bilateral members positioned in the axis of said anode, an intermediate member disposed between said bilateral members, means supporting said intermediate member fifilifrom one of said bilateral members allowing universal movement of said intermediate member, swinging bars carried by said intermediate member, hooks extending from said bars, parallel filament sections supported by said hooks, and a ring aflixed to said hooks to insure uniform spacing between said filament sections.

8. A double-ended electron discharge power tube comprising an external anode, glass portions sealed thereto at opposite ends, a single tubular .conductor extending from one of said glass portions, concentric tubular conductors extending from the opposite glass portion, a helical grid within said anode and supported from said single tubular conductor, and a multi-strand filament ;Within said grid and anode supported from said concentric conductors at one end, and means supporting the other end of said filament by said single tubular conductor.

9. A double-ended electron discharge power tube comprising an external anode, glass portions sealed thereto at. opposite ends, 'a'single tubular member extendingfrom one of said glass por"- tions, concentric 'tubul'ar conductors extending from said otherv glass portion, a plurality "of straight filament sections attached to each of said concentric conductors, and a yielding support carried by said tubular member and conne'ctedto' said filament sections. I I v l0. A double-ended electron discharge power, tube comprising the combination of'an'exter'nal anode, glass portions sealed thereto at opposite ends, a single tubular member extending from one of said glass portions, concentric tubular conductors extending from said other glass portions, a plurality of straight filament sections attached to each of said concentric conductors, a guide member in said single tubular member, a. rigid rod extending through said guide member, a supporting member attached to said rod and to said filament sections, and resilient supporting means for said rod in contact with said guide member.

11. A double-ended electron discharge power tube comprising an external anode, glass end portions sealed thereto at opposite ends, inner and outer concentric tubular conductors extending from one of said glass portions, a plurality of segmental blocks attached to one end of said outer conductor, a triangular block attached to one end of said inner conductor, a plurality of filament sections attached to said blocks, supporting means for said sections at the opposite ends thereof, and means coupling one section attached to said triangular block to a section attached to a segmental block.

12. An electron discharge device of the higher power type comprising an envelope formed of a metal portion and a glass portion, the metal portion serving as the anode of the device, inner and outer concentric tubular conductors extending from said glass portion, a plurality of straight filamentary sections supported in said metal portion, said sections being arranged in a circular boundary about an axis of said metal portion, alternate sections of said filament being connected to said inner and outer concentric conductors, and a heat shield interposed between said filament sections and said tubular conductors, said heat shield being supported by said filament sections extending from said inner conductor and having apertures allowing the free passage of said filament sections extending from said outer conductor.

13. A double-ended electron discharge power tube comprising an external anode, glass portions sealed thereto at opposite ends, a single tubular conductor extending from one of said glass portions, concentric tubular conductors extending from the opposite end portion, a plurality of guide members within said single tubular conductor, a sheath Within said tubular conductor for positioning said guide members therein, a rigid rod extending through said guide members, a plurality of filament sections extending between said concentric tubular conductors and said rod, "14o said single tubular conductor having a boss limiting the movement of said sheath in one direction, and adjustable resilient means engaging said support rod for limiting the movement of said sheath and guide members in the opposite direction.

14. An electron discharge tube comprising, an external anode, a glass portion sealed thereto, a filament within said anode supported from said glass portion, a cooling jacket surrounding said 150 lie from said glass portion, a conical metallic seal joi in said glass portion and said tubular member, a. second tubular conductor within said first tubular conductor, a multi-strand fiian ent supported within said anode by said tubular conductor s annular troiigheshaped insulating member sealed. to the end of said first tubular member, a conical, metallic seal joining said in-A s'ultwting member to said second tHbUIQI COIIdJ-ICT tor, and a. closure member fitted to the end ofsaid second tubuierieonducton r V WILuAM'T. GIBSON.

v ANTOINE H. BQULESTREAU,

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