US2572031A - Electrode and envelope assembly for multielectrode space discharge devices - Google Patents

Description

Oct. 23, 1951 H. R. .mcolual JR 2,572,031 -ELECTRODE AND ENVELOPE ASSEMBLY FOR MULTIELECTRODE SPACE; DISCHARGE DEVICES A Filed Jan. 26, 1949 2 sHEETjsfsHEET 1 Oct. 23, 1951 H. R. JAcoBus, JR 2,572,031

ELECTRODE AND ENVELOPE ASSEMBLY FOR MULTIELECTRODE l SPACE DSCHARGE DEVICES Filed Jan. 26, 1949 2 SHEETS-SHEET 2 /ITTURNEY Patented Oct. 23, 1951 ELECTRODE AND ENVELOPE ASSEMBLY FOR MULTIELECTRODE SPACE DISCHARGE DEVICES Herbert R. Jacobus, Jr., White Plains, N. Y., as-

signor to Sonotone Corporation,

Elmsford,

N. Y., a corporation of New York Application January 2c, 1949, seriaiNo. 12,985

7 Claims.

This invention relates to electron space charge devices in which an electrode assembly comprising an anode, av cathode and at least one grid or control electrode interposed between the cathode and the anode, are enclosed in a hermetically sealed envelope, and more particularly to such electron discharge devices which are known commercially as "subminiature electron tubes, although some of the features of the invention are applicable to electron space discharge tubes other than subminiature tubes.

Among the objects of the invention are subminiature tubes embodying novel features which make it possible to materially reduce their overall volume and to simplify the critical problems connected with their manufacture and to maire it possible to manufacture such tubes on a mass production basis. with a high degree of uniformity of their operating characteristics.

. The foregoing and other objects of the invention will :be best understood from the following description of exemplications thereof, reference being had to the accompanying drawings, where- 1n:

Fig. 1 is a vertical cross-sectionalview of one form of a multi-electrode subminiature tube exemplifying the invention, the tube being shown in a scale of about l to 8;

Fig. 2 is across-sectional View of the tube along line 2 2 of Fig. 1;

Fig.. 3 is a vertical crossrsectional and partially elevational view of the same tube along line 3 3 of Fig. 2;

Figs. 4 and 5 `are cross-sectional-views along lines 4-4 and 5 -5 of Fig. 1, respectively, Fig. 5 showing the bottom spacer in phantom by dashdot lines;

Fig. 4-A is a plan view of the upper spacer of the tube;

Fig. 6 is a perspective View of the electrode assembly of the tube, as seen from the top;

Fig. 7 is a perspective view of the bottom part of the electrode assembly; e

Fig. 8 is an elevational view of the transverse, flat end wall or stem of thertube envelope with the electrode contact leads sealed therethrough before their inner ends are joined to the electrodes of the electrode assembly; y

Fig. 9 is a top"view of the end row or stem shown in Fig.8;

Figs. l and l1 Vare elevational and plan views of the anode structure of the tube shown in Figs. 1 to '7; j

Figs. 12 and 13 are elevational'and plan views of the auxiliary electrode of .the tube shown in Figs. 1 to .7; and

Fig. 10-A is a detailed View similar to Fig. 1, I

showing a modified construction, in which a part of the anode positioned adjacent to a grid post', is shaped to form an outwardly facing getter compartment.

There are many applications requiring multielectrode electron amplifier tubes of the sub-` miniature type,v having extremely small dimensions and able to operate with a high degree o'f eiciency and with uniform desirable operating characteristics. Among such applications are.

hearing-aid ampliers, proximity fuses, and

radio broadcast receivers of a miniature'size suitable for hidden wear in the pocket ofl the user, and other applications in which a minimum of space is a critical factor. Although the principlesv of the invention are applicable to other types of subminiature tubes, and some aspectsyof the.V

invention are of a broader scope, their Vapplication will be described in` connection witha pentode-type tube shown in Figsl through '7,V

which has a very wide use as a voltage gain and power amplifier.

The tube shown comprises an evacuated, generally elongated tubular envelope II of vitreous plane vertical to the `plane of the stem.l The.

wafer-like lead stem i9 extends in a direction transverse to the envelope and is fused to its lower endborder. i

The electrode assembly comprises a filamentary cathode 2I.`a control grid 2,2, a screen grid 23, and an anode 24, all extending longitudinally y generally parallel to a common axis of the elec'-` trode assembly, as seen in Figs. l and 2, and an additional auxiliary electrode structure having' two auxiliary electrodes or electrode sections 25, 26, interposed across the electron path between the anode 24 and the screen grid 25.- In the-tube shown, the filamentary cathode 2l is madeof a thin filament of a refractorymetal such as tungsten, provided with an oxide coating which'emits electrons when the nlament is heated Vto {an elevated temperature.

mounting portions in the form yof metal strips The two opposite ends "ofthe filamentary cathode ZI are' provided'with or tabs 21 to which the ends of the lament are secured as by welding, and which are in turn secured to cathode supports which support the lamentary cathode in its proper operative position.

The two grids 2,2, 23 'are made `of very line refractory metal wire, for instance, tungsten wire about .001 and .0015" in diameter, the inner grid 22 being wound as a helix on and secured to two inner side rods or grid posts28,l andA the outer grid 23 being similarly ,woundand sup-- ported on two outer side rods or grid posts 29. The grid posts of such subminiature tubes are usually formed of thin wires, for instance, the inner grid posts of wire aboutl'" diameter, and the outer grid posts of wire about .020" diameter.

The grid posts as well as the cathode 2|, anode 24 and the two auxiliary electrodes 26 of the electrode assembly are held fin their operative position by two similar generally flat sheet-like insulating spacer elements 3|, 32,'made of'a material having a high dielectric constant. The two sheet-:like spacers 3|,32 are provided with apertures or openings engaged by junction or supporting` ends of the grid posts and of the other electrodes which are joined by the spacers into a self-'supporting electrode assembly.

"The-anode 24 is made of sheet metal, and is arranged to receive/the electrons emitted by the cathode filament under the control of the control electrode, in a manner `well known in the art. In all prior subminiature tubes the anode was vheld in its properly spaced operative position relatively to the other electrodes of the electrode assembly by junction portions or supporting rods seated in openings of the insulating spacers. Since the anode structure of such tubes forms the outermost part of the electrode assembly, the insulating supporting spacers on which the opposite ends of the anode supporting rods are retained, had to be madeof suflicient width to serve as an anchorage not only for the grid posts but also for the junction elementsof the anode.

According to one phase of the invention, a material reduction of the width and the over-,all volumepf the electrode assemblya critical factor in subminiature tubesismadeV possible by providingan exposed peripheral edge regions of the two insulating spacers 3|, A32 with spaced retainer recessesv 33, and by forming the opposite boundary edges of theanode sheet structure 25.- witha pluralityof spaced sheet tongue portions interlockingly engaging and .intertting with the retainer recesses of the two spacer members, so as to secure the two spacers 3|,.32 to the unitary tubular anode sheet structureand join them into a self -supporting assembly structure.

As shown in Figs. l to -7, andin detail in Figs. l-,and 1l, the anode 24is mad-e in the form offa cylindrical tubular sheet structure of thin refractoryimetal, such as nickel. Each of the opposite generally circular boundary edges of the anode 24 has two spaced sheet ears or tongues 34,-35, interlockingly engaging and interfitting with the two spaced retainer recesses 33 -of the two opposite spacer members 3|, 32, so as to secure the two spacers 3|, 32 to the upper and lower-ends ofthe tubular anode 24 and join' them into a self-supporting assembly.

,The` junction tongues 34,135 of the anode are provided with intermediate shoulder portions 3S againstywhich the two spacers 3|, 32 abut when they-are joined to the anode structure, to provide `in order to de-gas it.

4mica insulating spacers comprise hydrates which annular gap spaces between the major part of the circular boundary edges of the anode 24 and the facing portions of the mica spacers 3|, 32, and limit to a minimum th-e area along which they make direct contact with the metallic anode.

As is well known, as a part of the` evacuation process, the metallic anode structure has to be heated to a high temperature of about 900 C., On the other hand, the

decompose when `heated to an excessive temperature, weakening the spacer sheet structure and reducing its resistance to electric leakage, a phenomenon known as pulled mica. By limiting the contact area between the relatively large anode sheet structure and the mica insulating -Vspacers joined thereto to the small edge surface Aand spacing, may be illuminatedrand visually inspected.

The interlocking engagement of Ythe anode junction tongues 34, 35 with'the peripheral retainer recesses 33 of the two spacers.3|, 32 provides a good mechanical interconnection therebetween and joins vthem into a self-supporting mechanical structure, provided the anode tongue portions 34, 35 are slightly bent in inward 'direction after the two spacersZ-H, 32have been fitted with their recesses over the tongues against the tongue shoulders 38. It is not necessary to bend the end portions of the anode tongues 34, 35 over the outer surfaces of the spacers in order to provide such good operative mechanical interconnection between the anode and the two spacer elements so supported thereon.

As shown in Figs. l to 7, to provide a stronger interconnection between the anode 24 and the two spacers 3|, 32, both anode tongues cronly one anode tongue, such as tongue 34, of eachv boundary edge of the anode, may be bent as much as about against the outer surface of the respective adjoining spacer members 3|, 32, without l bringing the tongue portion overlying the spacer into direct contact engagement therewith.

As shown in Figs. l to 5, each of the insulating sheet spacers 3|, 32 is also provided with resiliently yieldable spacer projections 39 which ,are shaped to engage the inner surface of the tubu- .lar envelope and serve to maintain the anode and the entire electrode assembly in the properly spaced and aligned position within the envelope when the electrode assembly is inserted into the envelope from the bottom end thereof before the :stem portion i8 thereof with the leads sealed therein is properly joined and sealed to the Vside walls of the envelope.

In the tube of the invention, an auxiliary electrode structure formed of the two auxiliary electrodes 25, 23 of sheet metal, is utilized as a shieldingor suppressor electrode for shielding the elec-x tron discharge Space against secondary electron emission Yfrom the anode, and `for giving the tube the desired operating characteristics.

As shown in Figs. 1 to 7, and ingdetailfin Figs.

12 and 13, two auxiliary shield electrodes 25, 2'6 are made of elongated strips of a refractory sheet metal, having at its opposite end edge portions junction tongues 31 seated in elongated openings or slits 38 of the opposite insulating spacers 3|, 32 for holding the sheet electrodes 25, 26 in their proper operative position within the electrode assembly. The two auxiliary shield electrodes 25, 26 are positioned so that they provide wide sheet surfaces which are spaced from the cathode 2| and the anode 24 ,by about the same distance as the grid posts 29 of the screen grid 23, and which extend transversely across the path ofthe electrons from the cathode 2| acrossvthe two grid electrodes 22, 23 towards the facing arcuate regions of the circular anode 24. Each auxiliary sheet electrode 25, 26 has a central wall portion 4| Vhaving elongated electron beam openings 42 confining the beam of electrons passing from the cathode to the anode, and two wings or side wall portions 43 bent inwardly toward the region of the grid posts 29, so that when the two auxiliary electrodes 25. 26 are maintained at the cathode potential, the flow of electrons between the cathode 2| and the anode 24 will be confined to the two beam openings 42 of the opposite auxiliary electrodes 25, 26. Since the manner in which such auxiliary electron-intercepting electrodes operate is well known in the art-as described, for instance. in the U5 S. Patents to Schade, 2,107,520; Strutt 2,205,500; and Schoenberg 2,113 801; and in the British Patent No. 324,115- no further description of their operation is required. When used in space charge tubes operating as gain and power amplifier tubes, such auxiliary electrodes 25, 26 of the tube of the invention shown, are connected to the opposite ends of the lamentary cathode 2| and maintained at the cathode potential.

In the tube shown, the two insulating spacers 3|, 32 of the electrode assembly have in addition to the slit openings 38 for the junction tongues 31 of the auxiliary electrodes and the openings for seating the junction ends of the two sets of grid rods 28, 29, a generally central opening 44 of triangular shape to provide at the vertex of two angular edges thereof a positive seat against Which spaced seating portions of the cathode filament are held seated and positioned in proper spacing relatively to the other electrodes.

lor satisfactory operation of such discharge tubes, it is essential that the effective portion of the lamentary cathode 2| facing the operative portions of the other electrodes shall be held stretched under tension in a predetermined desired operative position. Because of the close electrode spacing, the problem of connecting the opposite ends of the thin nlamentary cathode to proper tensioning supports which hold the cathode filament tensioned and biased against the angular positioning recesses of the two spacers. is critical, particularly if such tubes are to be manufactured at low cost on a mass production basis.

' The required tiny connector elements by means of which the opposite ends of the lamentary cathode are connected and held tensioned in theY operative position to the electrode assembly, are so arranged as to make it possible to readily align the connector elements with junction elements of the iilamentary cathode and of the c0- operating supporting parts of the electrode assembly, and to readily join the aligned elements` in positions in whichv they automaticallyoperate tensioned condition.

A's shown in Figs. l, 2 and 7, the lower mounting tab 29 of thelamentary cathode 2| is supported in its operative position by 'a generally L- shaped metallic connector strip 416 having one arm to which the mounting tab 21 of the la-r mentary cathode 2| is secured as by welding. The connector strip 46 has an arm 41 angulally bent relatively to its longer arm and secured to the lower junction tongue 31 of the auxiliary electrode 25 projecting beyond the outer side of the lower spacer 32. The width of the connector strip arm 41 is substantially equal to the width of the projecting junction tongue 31 of the sheet electrode 25 to which it is secured, thereby enabling the operator to place them in aligned overlapped positions in which they are secured, as by welding. This connector strip arrangement obviates the necessity for using judgment and care when securing the connector` strip 46 inits proper operating position to the junction tongue 31 by means of which it is supported on the outer side of the electrode spacer 32.

As seen in Figs. l, 5 the arm of the connector strip 46 to Iwhich the bottom mounting tab of the lamentary cathode 2| is secured, is made of such length that when the filament mounting tab 21 is secured in a position where the edge of the tab 29 is substantially aligned with the end edge of the connector strip 46, the latter will automatically bias the bottom portion of the lamentary cathode 2| into seating engagement with the vertex of the angular recess of the opening spacer 44 through which it passes.

As seen in Figs. 1 to '1, by mounting the two auxiliary sheet electrodes 25, 26 so that they extend between the narrow sides of the generally flat or oblong grid electrodes 22, 23, in the manner shown, the bottom junction tongue 31 of the auxiliary sheet electrode 26 which serves as a support for the cathode connector strip 46, provides for a relatively long connector spring arm extending in a direction generally perpendicular to the desired direction of the biasing seating forces which are exerted by it on the end portion of the filamentary cathode 2| connected thereto. With this arrangement of the `auxiliary sheet electrodes 25, 26, the central portion 39 of each auxiliary sheet electrode provided with the beam opening 42 extends in a plane substantially perpendicular to the plane defined by the grid posts or the long axis of the grid electrodes 22, 23, and the L-shaped connector strip 46 connecting the junction tongue 31 of sheet electrode 26 to the cathode tab 21 of the cathode 2| provides a relatively long elastic biasing arm exerting the desired cathode biasing forces in the direction perpendicular to the direction of its length.

The generally L-shaped structure given to the cathode connector strip 46, 41, as seen in Figs. 1, 5 and 7, facilitates not only ready alignment of its ends with respect to the elements to which they have to be connected, but also greatly simplies the problem of welding its short arm 41 to its supporting junction tongue 31. To perform such welding operation, one of the welding electrodes may be placed against the inner surface of the bottom junction element 31 of the auxiliary sheet electrode 25 through the gap space between the longer arm 46 of the connector strip and the outer surface of the spacer 32, while the other Welding electrode is piaced against the outer surface of the short connector strip arm 41 held against the junction element 31, in which position the-welding current is passed .the welding electrodes.

between f .jAsfshoWn-in .Figs. 1,3, 4 and 6, the-upper .end offvtheifilamentary cathode 2| `is held tensioned and biased against the angular vcorner recess 4of the V-central opening 44 of the upper insuiating spaeri by a tensioning connector structure including a reversely bent generally U-shaped connector rod 5| and a coil spring 52. The Yrear portion of the lower arm of the metallic U-shaped connector rod 5| is aixed, as by welding',- to vthe outwardly projecting junction tongue 3'! of the auxiliary sheet electrode 2S. The coil spring 52 comprises al plurality of helical turns coiled looselyaround the vfree arm of the connector-rod 5|, and has one spring end arm 53 restrained from movementby aflix-ing it as by welding to a freely projecting portion of the lower arm of rod 5|. 'Ifhe-otherend of the loose coil spring 52 terminates a. substantially straight relatively long springaarm 54 to the end region of which isse-I cured asby welding, the upper mounting tab 2 oft-the cathode iilament 2|. The supporting rod member 5i is held aligned in the direction of its length by the'tongue portion 3? of the sheet Aelectrode 25 to which it is secured in a direction generally parallel to the direction of the biasing forces which the free spring arm 45 has to exert on the upper end of the filamentary cathode 2| for holding it biased against the corner recess of the supporting opening 37 of the top spacer 3|.

`Because of this arrangement, the coiled spring tensioning support member 52 of the cathode .support may be readily placed in its operative position on the U-shaped rod member 5i and secured .thereto in its proper operative position in which .its free spring arm 54 exerts the desired elasticand biasing .tensioning forces on the cathode filament afiixed thereto. This arrangement facilitates the securing of the U-shaped rod member 5| of theicathode tensioning spring coil52 in its proper aligned mounting position by merely aligning the rear end of the lower arm against the edge of the .projecting sheet tongue 3? of the auxiliary sheet electrode 2B and weld-ing them to each other by a simple welding operation. With the HJ-shaped rod member 5| so secured in its aligned-operating position, its freely projecting upper arm is ready to receive and hold the coil spring 52 in a position in which its free cathode tensioning arm 55s will automatically exert on the top end of the lamentary cathode 2| secured thereto, the desired tensioning and biasing forces which cause the filament portion passing through the .upper cathode opening 44 of the spacer 3| to be moved along the angular recess'edges to the corner seating recess and supporting it therein in proper operative tensioned position.

The arrangement of the connector rod 5| with its coil spring 52 shown, makes it possible for the operator to secure the U-shaped mounting rod of the cathode tensioning coil spring intermediate or center portion of the U.shaped supporting rod 5| in overlapped relation with the edge of outwardly projecting junction tongue 3? of the auxiliary sheet electrode 25, with the two rod arms extending substantially parallel to the adjacent outer surface of the spacer 3|, and to weld the rear portion of the inward rod arm to the overlapping portion of the tongue member 3'! by applying to the overlapping rod arm and tongue portions the welding electrodes and passing the welding current. When so welded, the two arms of the rod 5| project freely from electrode tongue 3i. The coil spring-52 may thereupon be readily slipped en the upperfre arm 52 in the :60 properly aligned position by merely aligning the of the rods and retained in a properly lalignedsupport,inwhich position the free straightspring arm Y54 exerts 'the desired cathode positioning and tensioning forces on the cathode lament 2 I. 5 To provide the desired aligned assembly, it is suiiicient to align the transverse intermediate junction section of the mounting rod member 5| with the edge of the sheet tongue 3i to which it -is to be secured, in av position in which the in- 10: ward-arm of the mounting rod 5| is placed-at some small distance from the insulating spacer 3| :substantially parallel to the plane of the spacer. The coil spring 52 is then readily slipped over the free end of the upper rod armof `rod member 5| until the free spring arm 54 is aligned withwthe-opposite edge of the sheet tongue,.as shown-in Fig. 4. Thereupon the other spring arm 53 is-.welded-to the inward rod arm of rodmember5|, in a position which automatically asgojfsures that the free arm of spring arm 54 will be held in a position in which it exerts, on the cathode filament 2| secured thereto, the desired tensioningY and sealing forces.

As shown in Figs. 1, 3, 4 and 8, the upper juncl tion tongues 35 of the tubular anode 24 has secured-thereto a getter support in the form of a metal strip 45| extending generally parallel above the outer surface of the upper insulating spacer 3|. The getter support strip El has formed thereina pocket 52 with an opening facing the adjacent side wall portion ofthe envelope and a body-of getter material held affixed within the pocket.

The getter support strip 6| is bent to 'generally conform to the tubular shape oi the envelope, and has a central portion provided with the getter pocket. E2. and two arms or wings extending therefrom soas to constitute barriers which confinev evaporated vapors of the gettermaterial to the 4o region of the envelope facing ,the outer surface of the getter support 6| and substantially prevent getter vapor from materially reducing the surface vleakage resistance of the insulating Spacer 3| .adjacent to which it extends.

4') ture toa minimum, the getter supportstrip 5| is arrangedto constitute in effect a short outward extension of an arcuate portion of the cylindrical anode structure. With such arrangement, the getter structure does not increase the size ofthe electrode structure, since it occupies the regionimmediately above the outer surface of the upper insulating spacer which has substantially the same height as the opposite region Vin which the cathode tensioning support elements 5|, 52y are positioned.

One side Wing of the-generally arcuate-getter support 5| forms a junction lportion 63 thereof, which is-secured as by welding to the anode `junction -tongue .35. The junction portion 63 of the getter support strip 6| is secured to the outwardly projecting tongue portion 35 of the anoderin va position in which an edge of the junction portion 63 substantially engages the ad- 65 jacent surface portion of the insulating spacer.

tion of the getter support strip 6| extending beyond its `junction portion 63 is spaced by a small A:15s-gap from the adjacent surface, portion of ,the

To keep `the height and size of the tube struc- .aravaca-1 insulating spacer 3|, in the manner indicated in Figs. l and 3.

By the arrangement shown, the getter support with its getter Vis conned to a short region of the height of the tube substantially coextensive in height with the region in which the cathode tensioning supporting elements are conned, thus making it possible to reduce the overall length or height of the tube to that occupied by the actual elements of the electrode assembly.

With the stem arrangement of the invention described above, the inward portions of the leads may be readily so arranged that a substantialll7 straight or slightly bent lead portion extending from the stem in a direction generally parallel to the axis of the electrode assembly will provide a lead connection from the electrode to the external circuits. This assures a clean combined electrode and stem assembly, with all connector elements extending between the electrode assembly and the external terminal Vconnections being readily accessible for manipulation, and joining by welding or the like. In addition, this arrangement greatly increases the ruggedness of the combined electrode assembly, and gives all interconnecting elements between the electrode assembly and the base greatly increased structural strength for withstanding the strains imposed thereon when such tube is` exposed to the enormous acceleration forces in applications such as proximity fuses on projectiles.

In the form shown, the ends of the inward portions of leads I3, I and I6, which are parts of the main row of terminal leads I2 through I6, and the adjacent junction ends of the grid side rod 26 of the inner grid 22, the junction ends of grid side rod 2S of the outer grid 23, and the junction tongue 35 of the anode, respectively, all extend substantially parallel to the axis of the electrode assembly.

The inward portions of the two leads I'I, I8, which are aligned in a row which is generally transverse to the main row of leads I2 through I6, likewise extend into engagement with the junction ends 31 of the two shield electrodes 25, 26, to provide connections to the two shield electrodes and therethrough to the lamentary cathode 2I, the opposite ends of which are connected between shield electrode 25 and shield electrode 26.

The inward portionsof the several leads I3, I5, I6, I'I, I8, terminate substantially in a plane transverse to the tube axis, so that the inner ends of the several leads may be readily aligned adjacent the junction elements of the electrodes to which they are to be joined and respectively secured thereto by simple Welding operations.'

The outward portions of leads I1, I8, which are aligned in a plane transverse to the plane of the main row of leads I2 through I6, are cut off slightly beyond the outer at surface of the stem I9 as they emerge therefrom.

To provide external terminal connections to the electrodes to which the inward lead portions I'I, I8 are connected, the inner portions of leads I2 and I4 are bent to form connector elements which join their outward prong portions to the inward lead portions I'I, I 8, which provide the connections to the shield electrodes described above. It will be notedv that the inwardly bent portions I2, I3 extend near the inner ilat surface of the stem I9 at a sufficient distance there- 4from to permit easy welding of the bent ends of the inner leads I2, I3 to the straight inner portions of leads I'I,VI8.

10 By securing the inner ends of the several electrode leads I3, I5, I6, I'I, and I8, which are displaced from a plane, to the junction portions of the electrode assembly at points where they emerge beyond the outer surface of the bottom spacer 32, the ends of the inner lead extensions serve also as retainers which retain the lower 'spacer 32 against axial displacement relatively to the electrode assembly.

In such subminiature tubes, the close, critical spacing between the cylindrical anode 24 and the two auxiliary sheet electrodes 25, 26 with their electron beam dening openings 42 relatively to each other and to the other electrodes of the electrode assembly, makes it essential to assure that their relative shape and spacing is .not disturbed when the junction tongue portions of the electrode sheet members l24, 25 and 26 are bent or subjectedto strains while joining them into the electrode assembly described above, or through the forces exerted thereon by the connector elements joined thereto, such as the cathode bliasingand supporting connector elements 6,6, 5I, 52, joined to the Vtongue junction portions of the two auxiliary sheet 'electrodes 25, 26.

In accordance with one phase of the invention, the cylindrical tubularanode structure 24 is provided, at two spaced prtions of its length adjacent to the end regions thereof, with arcuate channel formations 55 extending in a direction transverse to its axial length, so as to materially increase the stiffness of the Vanode structure against deformation of its cylindrical shape when the tongue junction portions 34 there are bent in the procedure of joining the two insulated spacers 31, 32 to the opposite ends ofthe anode structure.

Furthermore, in accordance with a phase of the invention, the two side wall portions 43 of each of the auxiliary sheet electrodes 25, 26are provided with an elongated channel formation 48 generally parallel to their axial length for materially increasing their stiffness and substantially preventing disturbing deformations theref* of and of their beam openings by bending or other forces applied to their junction tongues 3l.

In order to enable those skilled in the art'to readily practice the invention, and without in any way limiting itsscope', there are given be'- low data for a tube of the invention, which proved highly satisfactory when used as a gain amplier:

The insulating mica spacers 3I, 32 are about .006l to .010 thick, and are .220 in diameter, and are spaced by a distance of .315". The center distance between the outer grid posts is .125". The center distance between the inner grid posts is .065. The distance between the mounting slits of the auxiliary sheet electrodes is .120". i

The cylindrical'anod'e is of nickel or stainless steel sheet material, .005 thick and is .188,in`

diameter.

rlhe auxiliary sheet electrode is made of nickel or stainless steel sheet material .007 thick, their width is .143, and their beam opening is .25" by .062. l

The getter support is .093" high.

The cylindrical glass envelope has an .inner diameter-of .251, an outside diameter of W16, and a length slightly more than y The tube may be designed for operation with a filament current of 20 milliamperes, l5 milliamperes, or 10 milliamperes, with a voltage of .065v volt across the filamentl When operatingwith 11 affplate 'voltage anda screen voltage of 22.5 volts, andfa plate current of 200 microamperes, it has aftransductance of 100 micromhos and a plate resistance of 1 megohm.

Similar tubes with a distance of .600 between the' insulating spacers 3|, 32, and correspondinglyk longer electrodes, will serve as a power tube. Withthe filament designed for operation with a lament voltage of 1.25 volts and a filament current of '.020 ampere, such power tube operating with a plate voltage and screen voltage of 22.5 volts and a control grid Voltage of volts, and avplate current of 500 microamperes, has a trans'- ductanceof 400 micromhos, and a plate resistance of 170,000 ohms. It has a power output of'4.0 milliwatts at 12% distortion.

Asy indicated in Fig. 10-A, an outwardly facing surface portion of the sheet metal of the anodeother than that facing the electrode beam opening of a shield electrode-may be formed as by a shaping operation into an outwardly facing getter pocket E2| similar to the getter pocket off the getter support 6| for holding a body of getter material which is evaporated subsequent to the evacuation and sealing operation. Since the mass of the anode is extremely small, and of the order of the mass of the getter supports generally used in tubes, such arrangement eliminates the necessity of a separate getter support, in accordance with the principles of the copending Herbert D. Suesholtz et al. application Serial No. 633,670, filed December 8, 1945, now Patent No. 2,464,272.

The subminiature tube of the invention of the type described, may be readily manufactured by the following procedure:

The upper insulating mica spacer 3| is placed with its top surface on an upwardly facing assembly jig with its inner surface facing upwardly. The junction ends of the two grid posts 23, 29 of the inner grid 22 and the outer grid 23, respectively, are then inserted into the corresponding openings of spacer 3|. The junction tongues 31 of the two auxiliary suppressor sheet electrodes 25, 26 are then inserted into the junction slit 3,8 of the upper spacer 3|, whereupon the cylindrical anode 24 is slipped over the so-positioned electrodes 22, 23, 25, 25 and the junction tongues 34, 35 of the anode 24 are inserted into the recesses 33 of the top spacer 3| while held in position on the assembly jig.

The bottom spacer 32 is then positioned above the .so-assembled electrodes 22, 23, 24, 25, 26, and its openings and recesses are slipped over the bottom junction ends of the grid pests 2-, 29, and the bottom junction tongues 31 and 34, 35 of the suppressor electrodes 25, 26 and of the anode 24, respectively. With the several electrodes and the two Vspacers held in inverted positionv on the assembly jig, the anode junction tongue 34 is bent about 90 over the outer surface of the bottom mica spacer, and the other anode tongue 35 is temporarily bent slightly inwardly, thereby assuring that the bottom spacer 32 will be retained in its assembled position on the cylindrical anode (Figs. 1, and 9).

The electrode assembly is then turned 180 to bring the top spacer 3| to a position in which it faces upwardly. The upper anode junction tongue 34 is then bent about 90 over the outer surface of the spacer 3|, andthe other anode junction tongue 35 is temporarily slightly tilted inwardly to assure that the upper spacer 3| is retained on the cylindrical anode 24 (Figs. 3, 13) In'addition, the top junction tongue 31 Aof the 12 suppressor electrode 25 is slightly tilted ininward direction to assure that it does not make contact withthegetter pocket t2V of the` getter support 5| when the`latter is secured to the assembly (Figs. 1, 2, 13). v

After removing the electrode assembly from the assembly jig, the L-shaped cathode connector strip 45 is placed with its junction arm 47 in overlapping alignment against the coextensive bottom junction tongue 37 of the suppressor electrode25, and secured thereto by welding. The U-shape'd spring-mountingrod 5| of the cathode tensioning coil spring 52 is placed in the aligned position shown, with its two arms aligned in the plane of the top tongue 3'! of the suppressor electrode 26 and extending parallel to the planeof the spacer 3 and with the inner arm of the rod 5| overlappingly aligned with one edge of the screen tongue v3l secured thereto by welding, so that the upper free arm of rod 5| extends generally parallel to the plane of the biasing forces exerted by the free spring arm 54 on the cathodelament 2|.

In a separate sub-assembly operation, the upper mounting tabv 2 of the cathode 2| is secured in aligned position to an end portion of the free spring arm 54 in a direction generally perpendicular thereto, so that when the spring coil 52 is placed on the freearm of U-shaped rod 5|, the free spring arm 54' will exert on the top end of the cathode filament 2| biasing and tensioning forces in the direction of the plane deined by the grid side rods 28, 29.

The lamentary cathode 2| carried freely susi'- pended in a verticalpos'ition by the end portion of the straight spring arm of the coil spring 5| is then dropped or threaded with its lower end through the relatively, large aligned central cathode openingsof the two spacers 3|, 32 Yof the electrode assembly. The 'coiled turns of the coil spring 52 are thenxslipped over the free upper arm of the U-shaped mounting rod 5|. The lower cathode `mounting tap 27 is then welded to theend of the free arm of the L.shaped connector strip 45, the other arm of which has been previously secured in, aligned loverlapping position to the ,bottom tongue 3l of the suppressor electrode 25. lthe4 short spring arm 53 of the coilv spring 52 is` then gripped and brought against the lower arm of the U-shaped mounting rod 5| and welded thereto in av position in which the free arm 54f,of the coil spring 52 extends substantially aboveth'e grid si'de rod jwhic'n is next to the 'angularlar'nent seating recess .of the'spacer"openingI 44 A (F'ig 3). YIn this lposition the free spring"`ari`n`5lexerts the desired elastic tensioning"andfvbiasingforces which maintain the cathode lanientZl tensionedA and biased to come into seatingffengagement with the vertex of the angular recess of' the cathode seat openings 44 of the two Ispacers 31, 32.', v

VThe end portion 530i the' getter support strip 6| is then placed in' 'overlapping alignment with the upper anodetongue'" 35;' and 'welded thereto, ther tongue 35 Yhavingbeen straightened before performing the ,welding operation, since the welded endof the" getter istripY 5| now serves (to, retain the spacer l3| against axial displacement.

Bytthe .foregoing4 operations,v all the: elements of the electrode assembly including the cathode and its tensioning"A and'biasing support, are all joined 'and secure'd`tofeachrothr into a coin'- plete, self -supporting electrode'assembly in whichv substantially" all"- oprat'ive partsvk occupy their iinal operative position, in which'the prprfr# `28 of the inner grid 22.

iarzagsl '13 ationship and spacing of the individual electrode elements may be inspectedand checked.

The electrode leads are welded to the junction ends of the several electrodes as a part of the assembly operation described above, as follows:

Lead I6 is welded to the adjacent junction end of grid rod 29 of the outer grid 23. Lead I4 is welded to the adjacent junction end of grid rod Lead H is welded to the junction tongue 35 of the anode 24, which has been previously bent to retain the spacer, but which has been straightened out before performing the welding operation, since the inner ends of at least two of the electrode leads I3 to I1 now serve to retain the spacer 32 against axial displacement. A connector strip or ribbon 34 has one end thereof welded to the junction tongue 31 of suppressor electrode 25, and the other end of the connector ribbon 34 is welded to the inner end of the lead conductor I3. The inner end of lead l5 is then welded tothe bottom junction tongue 3i of the suppressor electrode 26.

With the foregoing operation, the electrode assembly has been joined by the electrode lead conductors to the transverse lead stem I8 through which they are sealed, with all elements of the co-completed assembly held in their nal operative position, in which their relationship and spacing may be inspected and checked. Notwithstanding the extremely close spacing o the tiny electrodes of the sub-miniature `tube of the invention, the foregoing assembly operations may be readily performed by relatively unskilled labor after only short training, and the entire sequence of the foregoing assembly operations requires less tirne than reading the yforegoing description thereof.

It will be apparent to those skilled in the art that the novel principles of the invention d isclosed herein in connection with specic exemplications thereof will suggest various other modifications and applications of the same.Y It is accordingly desired that in construing the breadth of the appended claims they shall not be limited to the specific exempli-ications ofthe invention described above.

I claim:

1. In an electron space discharge device housed in a sealed tubular envelope: an assembly of electrodes extending longitudinally generally parallel to a common axis including a tubular anode of sheet metal, and at least two additional electrodes and a rllamentary cathode surrounded by the anode; two spaced, generally flat sheetlike insulating spacers extending transversely to said axis and having two transversely disposed rows of spacer openings holding the opposite ends of said electrodes in their operatively spaced positions; each of said two rows of spacer openings including a common central spacer opening and two outward spacer openings spaced by a distance from said central spacer opening; each spacer having four peripherally displaced spacer projectionsl aligned with said four outward spacer openings and engaging the inner surface of the envelope for spacing said assembly from the envelope; the peripheral edge or" each spacer having at least two spaced retainer recesses each of small depth and relatively large width and positioned between two spacer projections thereof in positions angularly displaced relatively to said two rows of spacer openings; each of the opposite ends of said tubular anode having at least two junction sheet tongues extending from the edge thereof and interlockingly engaging and interiitting the two spaced ref'cesses of said two spacers for securingsaid two spacers to said anode and joining them and said electrodes into a self-supporting electrode assembly. y

2. In a space discharge device as claimed in` claim 1, at least a portion of one tongue of each end of said tubular anode being bent over the exterior surface of the edge portion of the spacer recess engaged thereby for xing said one spacer against axial displacement, a getter structure of sheet metal having a sheet portion secured to the other tongue at one end of said anode and extending over an adjacent outer surface portion of the spacer for fixing said spacer against axial displacement; an electrode lead secured to the other tongue at the other end of said anode and extending over and adjacent outer surface portion of the spacer for xing said spacer against axial displacement.

3. In an electron space discharge device: an assembly of electrodes extending longitudinally Igenerally parallel to a common axis, including a and at least one grid electrode extending between said cathode and said two sheet electrodes; two spaced generally flat sheet-like insulating spacers extending transversely to said axis and holding the opposite ends of said electrodes in their operatively spaced positions; the opposite ends of said two sheet electrodes having junction tongues extending through openings of said spacers; opposite end portions of said cathode extending through cathode openings of said spacer and being held biased against cathode seats of said cathode openings; one connector structure being connected :between one cathodev end of said cathode and one junction tongue of one sheet electrode at one end of said electrode assembly, and an additional connector structure connected between the other end of said cathode and a junction tongue of the other sheet electrode at the other end of said electrode assembly the arms of said U-shaped rod extending substantially parallel to the surface of the adjacent spacer and to the direction of the biasing forces restraining and holding said cathode against said cathode seats.

4. In a discharge device as claimed in claim 3, said U-shaped rod being secured to said junction tongue in a position in which the transverse portion of said U-shaped rod extending between its two arms is substantially aligned with the adjacent side edge of the junction tongue to which it is secured.

5. In an electron space discharge device: an assembly of electrodes extending longitudinally generally parallel to a common axis, including a tubular anode of sheet material, two additional sheet electrodes located between opposite portions of said anode, a filamentary cathode positioned between said additional sheet electrodes, and at least one grid electrode extending between said cathode and said two sheet electrodes;

two spaced generally flat sheet-like insulating Spacers extending transversely to said axis and holding the opposite ends of said electrodes in their operatively spaced positions; the opposite ends of said two sheet electrodes having junction tongues extending through openings of said spacers; opposite end portions of said cathode extending through cathode openings oi said spacer and lbeing held biased against cathode seats of said cathode openings; one connector structure being connected between one cathode end of said cathode and one junction tongue of one of said sheet electrodes at one end of said electrode assembly, and an additional connector structure connected between the other end of said cathode and a junction tongue of the other sheet electrode at the other end of said electrode assembly for exerting biasing forces holding two spaced seating regions of said cathode tensioned and biased against said cathode seats, said spacer openings forming parts ofv two rows of spacer openings of each spacer, each row including two outer spacer openings spaced from the center of the spacer; each spacer having four peripherally displaced spacer projections aligned with said two rows of spacer openings and engaging the inner surface of the envelope for spacing said assembly from the envelope, and each spacer having along its edge at least two spaced retainer recesses, each recess being o`f small depth and relatively large width and being positioned between two spacer projections in positions angularly dispiaced relatively to said two rows of spacer opening; each ofthe opposite ends of said tubular anode having f at least two junction sheet tongues extending from the edge thereof and interiinizingiy engaging and interfitting with the two spaced recesses of said two spacers for securing said two spacers to said anode and joining them and said electrodes into a self-supporting electrode assembly.

6. In a discharged device as claimed in claim 5, said U-shaped rod being secured to said junction tongue in a position in which the transverse portion of said U-shaped rod extending between its two arms is substantially aligned 16 with the adjacent side edge of the junction tongue Vto which it is secured.

7. In a space discharge device as claimed in claim 5, at least a portion of one tongue ofeach end of said tubular anode being bent over the' exterior surface of the edge portion of the spacer' recess engaged thereby for xing said spacer against axial displacement, a getter structure of sheet metal having a portion secured to the other tongue and extending over an adjacent outer surface portion of the spacer engaged by said other tongue for fixing said spacer against axial displacement, each of said sheet electrodes having along a central wall region thereof an aperture for passing a beam of electrons 'between the cathode and the anode, the two side Wall regions adjoining the aperture of eachof said sheet electrodes having'each a lengthwise channel formation extending parallel to said axis for materially increasing the stiiiness of the central regions of said sheet electrodes and preventing deformation of their apertures by mounting strains.

HERBERT R. JACOCBUS, JR.

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

UNITED STATES PATENTS Number Name Date 2,107,520 Schade Feb. 8, 1938 2,266,080 Rockwood Dec. 16, 1941 2,274,554 Krim Feb. 24, 1942 2,296,579 Seelen Sept. 22, 1942 2,350,003 West May 30, 1944 2,355,083 Krim Aug. 8, 1944 2,402,797 Wood June 25, 1946 2,433,410 Walker et al Dec. 30, 1947 2,459,861 Wood Jan. 25; 1949 2,464,241 Krim Mai. 15, 1949 2,464,272 Suesholtz Mar. 15, 1949 2,476,940 Wood July 19, 1949 2,486,829 Ewing Nov. 1, 1949 2.487.592 Rishell Nov. 8, 1949

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