US2572032A - Electrode and envelope assembly for multielectrode space discharge devices - Google Patents

Description

Oct. 23, 1951 H. R. JACOBUS, JR, ETAL 2,572,032

' ELECTRODE AND ENVELOPE ASSEMBLY FOR MULTIELECTRODE SPACE DISCHARGE DEVICES Filed Jan 26, 1949 2 SHEETSSHEET 2 IJYVENTOR.

Patented Oct. 23, 1951 ELECTRODE AND ENVELOPE ASSEMBLY FOR MULTIELECTRODE SPACE DISCHARGE DEVICES Herbert R. J acobus, J L, White Plains, and Harold L. Lipschultz, New York, N. Y., assignors to Sonotone Corporation, Elmsford, N. Y., a corporation of New York Application January 26, 1949, Serial No. 72,986

7 Claims.

This invention relates to electron space charge devices in which an electrode assembly comprising an anode, a 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 make 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 exemplifications thereof, reference being had to the accompanying drawings, wherein:

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

Fig. 2 is a cross-sectional view of the tube along line 2-2 of Fig. 1;

Fig. 3 is a vertical cross-sectional and partially elevational view of the same tube along line 33 of Fig. 2; 7

Figs. 4 and 5 are cross-sectional views along lines 4-4 and 55 of Fig. 3, respectively;

Figs. 6 and 7 are detail cross-sectional views of the upper and lower parts of the tube along lines 6-6 of Fig. 4 and lines 'I-'I of Fig. 5, respectively;

Figs. 8 and 9 are perspective views of the electrode assembly of a tube similar to that of Figs. 1 to 7, as seen from the top and bottom, respectively, with a modified anode arrangement, parts of the envelope and of the electrodes being broken away;

Figs. 10 and 11 are elevational and plan views of the anode structure of the tube shown in Figs. 1 to '7; and

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

There are many applications requiring multielectrode electron amplifier tubes of the subminiature type, having extremely small dimensions and able to operate with a high degree of efiiciency andwith uniform desirable operating characteristics. Among such applications are hearing-aid amplifiers, proximity fuses, and radio broadcast receivers of a miniature size suitable for hidden wear in the pocket of the user, and other applications in which a minimum of space is a critical factor. ciples of the invention are applicable to other types of subminiature tubes, and some aspects of the invention are of a broader scope, their application will be described in connection with a pentode-type tube shown in Figs. 1 through 13, 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 material such as glass, which encloses an electrode assembly generally designated I2, having a plurality of electrodes which are connected to a plurality of leads I3, I4, I5, I6 and I1, her- .metically sealed through an electrically insulated terminal end wall portion I8 of the envelope to provide external circuit connections to the electrodes. The terminal end wall portion I8 is made in the form of a wafer-like stem of Vitreous material sealed around portions of lead conductors I3 to I! held generally aligned in a plane vertical to the plane of the stem. The wafer-like lead stem I8 extends in a direction transverse to the envelope and is fused to its lower end border.

The electrode assembly comprises a filamentary cathode 2|, a control grid 22, a screen grid 23, and an anode 24, all extending longitudinally generally parallel to a common axis of the electrode assembly, and an additional auxiliary electrode structure having two auxiliary electrodes or electrode sections 25, 25, interposed across the electron path between the anode 24 and the screen grid 23. In the tube shown, the filamentary cathode 2| is made of a thin filament of a refractory metal such as tungsten, provided with an oxide coating which emits electrons when the filament is heated to an elevated temperature. The two opposite ends of the filamentary cathode'ZI are provided with mounting portions in the form of metal strips or tabs Although the prin-- v 2'! to which the ends of the filament are secured as by welding, and which are in turn secured to cathode supports which support the filamentary cathode in its proper operative position.

The two grids 22, 23 are made of very fine 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 posts '28, and the outer grid 23 being similarly wound and supported on two outer side rods or grid posts '23. The grid pests of such subminiature tubes are usually formed of thin Wires, for instance, the inner grid posts of wire about .015" diameter, and the outer grid posts of, wire. about .020" di ameter.

The grid posts as well as the cathode 2 anode 24 and the two auxiliary electrodes 28 of the electrode assembly are held in their operative position by two similar generally fiat sheet-like insulating spacer elements 33, 32, made of a material having a high dielectric constant. The two sheet-like spacers 3f, 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 2A is made of sheet metal, and is arranged to receive the electrons emitted by the cathode filament under the controlof the control electrode, in a manner well known in the art. In all prior subminiature tubes the anode was held 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 made of sufficient width to serve as an anchorage not only for the grid posts but also for the junction elements of the anode.

According to one phase of the invention, a material reduction of the width and the over-all volume of the electrode assembly-a critical factor in subminiature tubes-is made possible by providing the exposed peripheral edge regions of the two insulating spacers 3!, 32 with spaced retainer recesses 33, and by forming the opposite boundary edges of the anode sheet structure 24 with a plurality of spaced sheet tongue portions interlockingly engaging and interfitting with the retainer recesses of the two spacer members, so as to secure the two spacers 31, 32 to the unitary tubular anode sheet structure and join. them into a self-supporting assembly structure.

As shown in Figs. 1 to 9, and in detail in Figs. and 11, the anode 24 is made in the form of a cylindrical tubular sheet structure of thin refractory metal, 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 SI, 32, so as to secure the two spacers 3|, 32 to the upper and lower ends of the tubular anode 24 and join them into a self-supporting assembly.

The junction tongues 34, 35 of the anode are provided with intermediate shoulder portions 36 against which the two spacers 3|, 32 abut when they are joined to. the anode structure, to provide annular gap spaces between the major part .of

the circular boundary edges of the anode 2.4 an

the facing portions of the mica spacers 3|, 32, and limit to a minimum the 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., in order to de-gas it. On the other hand, the mica insulating spacers comprise hydrates which decompose when heated to an excessive temperature, weakening the spacer sheet structure and reducing its resistance to electric leakage, a phenomenon known as puffed mica. By limiting the contact area between the relatively large anodesheet, structure and the mica insulating spacers joined thereto to the small edge surface portions of the junction tongues of the tubular anode and the recess edge-regions of the spacers, the flow of heat from the anode maintained at a high temperature to the spacer body, is kept down, and damage to the mechanical and insulating characteristics of the insulating spacers 3!, 32 is avoided.

The annular gap spaces between the circular boundary edges of the anode 24 and the insulating spacers 3!, 32 provide windows through which the interior elements of the electrode assembly enclosed by the anode, and their proper mounting and spacing, may be illuminated and visually inspected.

The interlocking engagement of the anode junction tongues 34, 35 with the peripheral retainer recesses 33 of the two spacers 3|, 32 provides a good mechanical interconnection there between and joins them into a self-supporting mechanical structure, provided the anode tongue portions 34, 35 are slightly bent in inward direction after the two spacers 3|, 32 have been fitted with their recesses over the tongues againstthe tongue shoulders 36. 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. 1 to 9, to provide a stronger interconnection between the anode 24 and the two spacers 3!, 32, both anode tongues or only one anode tongue, such as tongue 34, of each 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 bringing the tongue portion overlying the spacer into direct contact engagement therewith.

As shown in Figs. 8 and 9, to decrease the area of heat transmission between the metallic anode structure, which has to be heated to a high-degassing temperature, and the insulating spacers 31,32, the anode junction tongues 34, 35 may be slit along their length into two tongue sections 51, 58, one slit narrow tongue section 51 of each slit being bent over the outer surface of the recess edge region 33 of the respective spacers 31!, 32 engaged thereby, the other narrow tongue-section 58' projecting outwardly away from the spacer surface. This arrangement'assures that the two spacers are held in engagement along their relatively long recessed edges with a relatively long abutting region of the junction tongues engaging the edge recesses 33 while only a narrow part of the width of the metallic junction tongues 34, 35 of the anode is bent over the outer surface of the respective insulating anode spacers 3 I, 32 to provide strong mechanical retainer elements retaining the two spacers in their interlocked engagement with the tubular anode structure.

As shown in Figs. 1 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 tubular envelope H 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 l8 thereof with the leads sealed therein is properly joined and sealed to the side walls of the envelope.

In the tube of the invention, an auxiliary elec trode structure formed of the two auxiliary elec trodes 25, 26 of sheet metal, is utilized as a shielding or suppressor electrode for shielding the electron discharge space against secondary electron emission from the anode, and for giving the tube the desired operating characteristics.

As shown in Figs. 1 to 9, and in detail in Figs.

12 and 13, two auxiliary electrodes 25, 26 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 of the electrons from the cathode 2| across the two grid electrodes 22, 23 towards the facing arcuate regions of the circular anode 24. Each auxiliary shield electrode 25, 26 has a central wall portion 4| having elongated electron beam openings 42 confining the beam of electrons passing from the cathode to the anode. Each auxiliary shield electrode 25, 26 has 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 fiow 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 U. S. Patents to Schade, 2,107,520; Strutt 2,205,500; and Shoenberg 2,113,801; and in the British Patent No. 324,175-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 filamentary 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.

For satisfactory operation of such discharge tubes, it is essential that the efiective portion of the filamentary 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 filamentary 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 filamentary cathode are connected and held tensioned in the 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 filamentary cathode and of the cooperating supporting parts of the electrode assembly, and to readily join the aligned elements in positions in which they automatically operate to maintain the cathode in the desired operative tensioned condition.

As shown in Figs. 1, 2, '1 and 9, the lower mounting tab 21 of the filamentary cathode 2| is supported in its operative position by a generally L-shaped metallic connector strip 46 having one relatively long arm to which the mounting tab 21 of the filamentary cathode 2| is secured as by welding. The connector strip 46 has a shorter arm 41 angularly 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 in its 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. 1, 5 the longer arm of the connector strip 46 to which the bottom mounting,tab of the filamentary 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 substantiallyaligned with the end edge of the connector strip 46, the latter will automatically bias the bottom portion of the filamentary 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 9, by mounting the two auxiliary shield electrodes 25, 26 so that they extend between the narrow sides of the generally fiat or oblong grid electrodes 22, 23, in the manner shown, the bottom junction tongue 31 of the auxiliary shield 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 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 45, 51, as seen in Figs. 1., Sand 9, facilitates not only ready alignment of its ends with respect to the elements to which they have to be connected, but also greatly simplifies the problem of welding its short arm 41 to its supporting junction tongue 37. 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 48 of the connector strip and the outer surface of the spacer 32, while the other welding electrode is placed against the outer surface of the short connector strip arm 4'! held against the junction element 3?, in which position the welding current is passed between the welding electrodes.

As shown in Figs. 1, 3, 4, 6 and 8, the upper end of the filamentary cathode 2| is held tensioned and biased against the angular corner recess of the central opening 44 of the upper insulating spacer 3| by a tensioning connector structure including a reversely bent generally U-shaped connector rod 5| and a coil spring 52. One arm of the metallic U-shaped connector rod 5| is aihxed, as by welding, to the outwardly projecting junction tongue 31 of the auxiliary sheet electrode 25. The coil spring 52 comprises a plurality of helical turns coiled loosely around the freearm of the connector rod 5|, and has one spring end arm 53 restrained from movement by affixing it as by welding to a portion of the lower arm of rod 5|. The other end of the loose coil spring 52 terminates in a substantially straight relatively long spring arm 54 to the end region of which is secured as by welding, the upper mounting tab 21 of the cathode filament 2|. The supporting rod member 5| is held aligned in the direction of its length by the tongue portion 3'5 of the sheet electrode 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 toexert on the upper end of the filamentary cathode 2 for holding it biased against the corner recess of the supporting opening 3! 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 5! and secured thereto in its proper operative position in which its free spring arm 54 exerts the desired elastic and biasing tensioning forces on the cathode filament afiixed thereto. This arrangement facilitates the securing of the U-shaped rod member 5! of the cathode tensioning spring coil 52 in its proper aligned mounting position by merely aligning its lower arm against the projecting sheet tongue 3'| of the auxiliary sheet electrode 26 and welding them to each other by a simple welding operation. With the Ushaped rod member 5| so secured in its aligned operating position, its freely projecting other arm is ready to receive and hold the coil spring 52 in a position in which its free cathode tensioning arm 54 will automatically exert on the top end of the filamentary 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: supportingit 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 52 in the properly aligned position by merely aligning the end of the lower inward arm of the U-shaped supporting rod 5| with the edge of outwardly projecting junction'tongue 37 of the auxiliary sheet electrode ZS-with the inward rod arm extending substantially parallel to the adjacent outer surface of the spacer 3 |and to apply welding electrodes to the exposed surfaces of the overlapping portions of the tongue member 31 and the inward rod arm for welding them in the aligned position in which the free arm of the supporting rod will provide the proper aligning support for the coil spring 5|, in which position its free straight spring arm 54 exerts the desired cathode positioning and tensioning forces on the cathode filament 2|.

In Figs. 1 and 5 the inward arm of the U-shaped cathode mounting coil spring 52 is shown affixed to the outwardly projecting tongue portion 37 of the auxiliary sheet member 25 in a position in which the lower arm of the rod member 5! is substantially in direct engagement with the outer surface portion of the insulating spacer 3| bordering the opening through which the tongue 37. projects. With such arrangement, the lower arm of the mounting rod 5| operates to retain the spacer 3| and prevent axial displacement thereof. Such connection of the U shaped spring mounting rod 5| also facilitates alignment and positioning of the mounting rod 5| relatively to the sheet tongue 31 to which it has to be secured in order to provide a properly aligned mounting support for the coil spring 52.

However, to provide the desired aligned assembly it is sufficient to align the end of the inward arm of the mounting member 5| with the edge of the sheet tongue 31 to which it is to be secured, in a position in which the inward 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, as this will, by itself, automatically assure that the free arms of the U-shaped spring mounting rod 5| will provide the proper aligned mounting support for the cathode tensioning coil spring 52.

As shown in Figs. 1, 3, 6 and 13, the upper junction tongues 35 of the tubular anode 25 has secured thereto a getter support in the form of a metal strip 6| extending generally parallel above the outer surface of the upper insulating spacer 3|. The getter support strip 6| has formed therein a pocket 62 with an opening facing the adjacent side wall portion of the 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 of the envelope, and has a central portion provided with the getter pocket 62 and two arms or wings extending therefrom so as to constitute barriers which confine evaporated vapors of the getter material to the region of the envelope facing the outer surface of the getter support BI and substantially prevent getter vapor from materially reducing the surface leakage resistance of the insulating spacer 3| adjacent to which it extends.

To keep the height and size of the tube structure to a minimum,'the getter support strip BI is arranged'to constitute in effect a. short outward extension of an arcuate portion of the cylindrical anode structure. With such arrangement, the getter structure doe not increase the size of the electrode structure, since it occupies the region immediately above the outer surface of the upper insulating spacer which has substantially the same height as the region in which the cathode tensioning support elements 51, 52 are positioned.

Qne side wing of the generally arcuate getter support forms a junction portion 63 thereof,

which is secured as by welding to the anode junc- 'tion tongue 35. The junction portion 63 of the getter support strip BI is secured to the outwardly projecting tongue portion 35 of the anode in a position in which an edge of the junction portion 63 substantially engages the adjacent surface portion of the insulating spacer 3|, so as to retain the spacer 3| against displacement in axial direction away from the seating shoulder portion 38 of the tongue 35.

In order to prevent overheating of the insulating body of the spacer 3! when the getter strip BI is heated to the high temperature at which the getter body evaporates, the edge portion of the getter support strip 6| extending beyond its junction portion 63 is spaced by a small gap from the adjacent surface portion of the insulating spacer 3|, in the manner indicated in Figs. 1 and 3.

By the arrangement shown, the getter support with its getter is confined 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 confined, thus making it possible to reduce the over-all length or height of the tube to that occupied by the actual elements of the electrode assembly.

As shown in Figs. 1, 3, 6, and 9, the inward end portions of the conductor leads l3 to H are shaped by bending and are displaced from the plane in which they sealed through the fiat stem 8 of the envelope, so that the inner end portions of the several leads terminate substantially in a plane transverse to the tube axis, and engage outwardly projecting junction elements of the several electrodes to which they are secured by welding, as well as the outer surface of the bottom insulating spacer 32 of the electrode assembly. This arrangement of the electrode leads assures that when joining the stem 8 to the adjacent walls of the envelope, the stem is automatically aligned coaxially with and substantially parallel to the plane of the insulating spacer 32 of the electrode assembly at the desired proper minimum distance therefrom.

In the tube shown, the inner end of lead I3 is connected by a metallic connector strip 64 welded thereto, to the downwardly projecting junction tongue 37 of the auxiliary sheet electrode 26, which also serves as a terminal connection to the upper end of the filamentary cathode 2|. The inner end of lead [4 is secured as by welding to the outwardly projecting junction end of the grid rod 32 of the control grid 22. The inner end of the lead conductor 15 is secured as by welding to the adjacent downward junction tongue 31 of the other auxiliary sheet electrode 25 which also serves as the terminal connection for the lower end of the filamentary cathode 2|. The inner ends of leads [6 and l! are secured by welding to the adjacent junction end of grid post rod 29 of the outer grid 23 and to the downwardly projecting junction tongue 35 of the anode 24, respectively, thereby providing lead connections to the screen grid and to the anode.

Bysecuring several of the electrode leads 13 to the insulating spacers 3!, 32, and correspond- H, which are displaced from a plane, to the electrode assembly so that their inward ends also engage the adjacent outer surface portions of the spacer 32, they also serve as retainers which retain the lower spacer 31 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 defining 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 24, 25 and 26 arebent or subjected to 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 biasing and supporting connector elements 46, 5|, 52, joined to the tongue junction portions of the two auxiliary sheet electrodes 25, 26.

In accordancewith one phase of the invention, the cylindrical tubular anode structure 24 is provided, at two spaced portions of its length adjacent 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 anode structure against deformation of its cylindrical shape when the tongue junction portions 34 thereof are bent in the procedure of joining the two insulated spacers 3|, 32 to the opposite ends of the 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, 26 are provided with an elongated channel formation 48 generally parallel to their axial length for materially increasing their stiffness and substantially preventing disturbing deformations thereof and of their beam openings by bending or other forces applied to their junctiontongues 31.

In order to enable those skilled in the art to readily practice the invention, and without in any way limiting its scope, there are given below data for a tube of the invention, which proved highly satisfactory when used as a gain amplifier:

The insulating mica spacers 3|, 32 are about .006" 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 1125. The center distance between the inner grid posts is .065. The distance between the mounting slits of the auxiliary sheet electrodes is .120".

The cylindrical anode is of nickel or stainless steel sheet material, .005" thick and is .188" in diameter.

The 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".

The getter support is .093 high.

The cylindrical glass envelope has an inner diameter of .251", an outside diameter of 5, and a length slightly more than A".

The tube may be designed for operation with a filament current of 20 milliamperes, 15 milliamperes, or 10 milliamperes, with a voltage of .065 volt across the filament. When operating with a plate voltage and a screen voltage of 22.5 volts, and a plate current of 200 microamperes, it has a transductance of micromhos and a plate resistance of 1 megohm.

Similar tubes with a distance of .600" between inglylonger electrodes, will serve as a power tube. With the filament designed for operation with a filament 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 a plate current of 500 microamperes, has a transductance of 400 micromhos, and a pate resistance of 170,000 ohms. It has a power ou.put of 4.0 milliwatts at 12% distortion.

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 sunace facing upwardly. The junction ends of the two grid posts 28, 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 3'! 0f the two auxiliary suppressor sheet electrodes 25, 26 are then inserted into the junction slit 38 The bottom spacer 32 is then positioned above the so-assembled electrodes 22, 213, 24, 25, 26, and its openings and recesses are slipped over the bottom junction ends of the grid posts 28, 29, and the bottom junction tongues 37 and 34, of the suppressor electrodes 25, 26 and of the anode 24, respectively. With the several electrodes and the two spacers held in inverted position 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 is temporarily bent slightly inwardly, thereby assuring that the bottom spacer 32 will be retained in its assembled position on the cylindrical anode (Figs. 4 and 14).

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|, and the 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 3'! of the suppressor electrode 25 is slightly tilted in inward direction to assure that it does not make contact with the getter pocket 62 of the getter support 5| when the latter is secured to the assembly (Figs. 1, 2, 13)

After removing the electrode assembly from the assembly jig, the L-shaped cathode connector strip 43 is placed with its junction arm 41 in overlapping alignment against the coex tensive bottom junction tongue 37 of the suppressor electrode 25, and secured thereto by welding. The U-shaped spring-mounting rod 5| of the cathode tensioning coil spring 52 is placed in the aligned position shownwith its two arms aligned in the plane of the top tongue 31 of the suppressor electrode 26 and extending parallel to the plane of the spacer 3 |and with the inner arm of the rod 5| overlappingl aligned with one edge of the screen tongue 31 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 cathode filament 2|.

In a separate sub-assembly operation, the upper mounting tab 27 of the cathode 2| is secured in aligned position to an end portion of the freespring arm 54 in a direction generally perpendicular thereto, so that when the spring coil 52 is placed on the free arm of U-shaped rod 5|, the free spring arm 54 will exert on the top end of the cathode filament 2| biasing and tensioning force in the direction of the plane defined by the grid side rods 28, 29.

The filamentary cathode 2| carried freely suspended in a vertical position by the end portion of the straight spring arm of the coil spring 5| is then dropped or threadedwith its lower and through the relatively large aligned central cathode openings of the two spacers 3|, 32 of the electrode assembly. The coiled turns of the coil spring 52 are then slipped over the free upper arm of the U-shaped mounting rod 5|. The lower cathode mounting tap 2'! is then welded to the end of the free arm of the L-shaped connector strip 43, the other arm of which has been previously secured in aligned overlapping position to the bottom tongue 3'! of the suppressor electrode 25. The short spring arm 53 of the coil spring 52 i then gripped and brought against the lower arm of the U-shaped mounting rod 5| and welded thereto in a position in which the free arm 54 of the coil spring 52 extends substantially above the grid side rod 28, which is next to the angular filament seating recess of the spacer opening 44 (Fig. 3). In this position the free spring arm 54 exerts the desired elastic tensioning and biasing forces which maintain the cathode filament 2| tensioned and biased to come into seating engagementwith the vertex of the angular recess of the cathode seat openings 44 of the two spacers 3|, 32.

The end portion 53 of the getter support strip 6| is then placed in overlapping alignment with the upper anode tongue 35, and welded thereto, the tongue 35 having been straightened before performing the welding operation, since the welded end of the getter strip 6| now serves to retain the spacer 3| against axial displacement.

By the foregoing operations, all the elements of the electrode assembly including the cathode and its tensioning and biasing support, are all joined and secured to each other into a complete self-supporting electrode assembly in which substantially all operative parts occupy their final operative position, in which the proper relationship and spacing of the individual electrode elements may be inspected and checked.

It will be apparent to those skilled in the art that the novel principles of the invention thereof will suggest various other modifications and applications of the same. It is accordingly desired that in construing the breadth of the appended claims they shall not. be limited 'to the specific 'exemplifications of the invention described above.

What 'is claimed is:

"1. .In an electron space discharge device: an assembly of electrodes extending longitudinally generally parallel to a common axis, including a filamentary cathode having a cathode junction end, and a sheet electrode having at one end a junction tongue; a, generally flat insulating spacer extending transversely to said axis for spacing the ends of said electrodes and having a plurality of spacer openings for receiving said cathode junction end and said junction tongue; a connector structure connected between said cathode junction. end and said Junction. tongue for tensioning said cathode and exerting seating forces restraining the cathode junction end against a cathode seat portion of the spacer opening receiving said cathode junction end; said connector structure comprising a U-shaped rod having two rod arms and a coil spring loosely held on one rod arm; said coil spring having at its loose end a spring arm secured to said cathode junction end; the end portion of the other rod arm being secured to said junction tongue in a position in which the end of said other rod arm is substantially aligned with the adjacent side edge of the junction tongue, and the two rod arms extend substantially parallel to the surface of the adjacent spacer and to the direction of said seating forces; said spring arm extending from a portion of said coil substantially aligned with the other side edge of said tongue; the other end of said coil spring being secured to said other rod arm.

2. In an electron space discharge device: an assembly of electrodes extending longitudinally generally parallel to a common axis, including a filamentary cathode having a cathode junction end, and a, sheet electrode having at one end a junction tongue; a generally fiat insulating spacer extending transversely to said axis for spacing the ends of said electrodes and having a plurality of spacer openings for receiving and positioning said cathode junction end and said junction tongue; a connector strip connected between said cathode junction end and said junction tongue for tensioning said cathode and exerting seating forces restraining the cathode junction end against a cathode seat portion of the spacer opening receiving said cathode junction end; said connector strip comprising two angularly disposed strip arms, one strip arm being secured to said cathode junction end, and the other strip arm being of a width substantial- 1yequal to the width of said junction tongue and being secured thereto in substantially overlapping alignment therewith, and carrying said one strip arm at a distance from said spacer.

3. In an electron space discharge device: an assembly of electrodes extending longitudinally generally parallel to a common axis, including a filamentary cathode having two opposite junction ends, and two sheet electrodes each having at its opposite ends a junction tongue; two generally fiat insulating spacers each having a plurality of spacer openings for receiving the cathode junction end and the junction tongues of said sheet electrodes and spacing the other of said electrodes; a connector structure at one end of the electrode assembly connected between one cathode junction end and the junction tongue of one sheet electrode for tensioning said cathode and exerting seating forces biasing the adjacent cathode junction end against a cathode seat portion of the spacer opening receiving said cathode junction end, and a connector strip at the other end of the electrode assembly connected between the other cathode junction end and the junction tongue of the other sheet electrode; said connector structure comprising a U-shaped rod having two rod arms and a coil spring loosely held on one rod arm, said coil spring having at its loose end a spring arm secured to the adjacent cathode junction end; the end portion of the other rod arm being secured to its junction tongue in a position in which the end of said other rod arm is substantially aligned with the adjacent end of the tongue, and the two rod arms extend substantially parallel to the surface of the adjacent spacer and to the direction of said seating forces; said spring arm extending from a portion of the coil substantially aligned with the other side edge of the tongue to which the rod" is secured; the other end of said coil spring being secured to said other rod arm; said connector strip comprising two angularly disposed arms, one strip arm being secured to the adjacent cathode junction end and the other strip arm being of a width substantially equal to the width of the cooperating junction tongue and being secured thereto in substantially overlapping alignment therewith for carrying saidone strip arm at a distance from said spacer.

4. In an electron space discharge device: arr assembly of electrodes extending longitudinally generally parallel to a common aXis including a tubular anode of sheet metal and at least twoadditional electrodes surrounded by the anode; two spaced generally fiat sheet-like insulating spacers extending transversely to said axis and holding the opposite ends of said electrodes in; closely spaced operative positions and spaced from each other; each of said spacers having along its exposed peripheral edge at least two spaced retainer recesses each of small depth and. relatively large width; each of the opposite ends of said tubular anode having at least two junction sheet tongues extending therefrom and in-- terlinkingly engaging and interfitting 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, at least one of said junction tongues at each end of the anode having two: separated tongue sections, one tongue. section. being angularly bent over the spacer surface and? the other tongue section extending away there-- from.

5. In a space discharge device as claimed im claim 4, said assembly of electrodes including a metallic element secured to said other tongue: section of said one tongue extending away from the bent-over tongue section.

6. 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 filamentary cathode and at least two additional electrodes and a tubular anode of sheet metal surrounding all said electrodes; two spaced, generally flat sheet-like 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; said spacer having four peripherally displaced spacer projections aligned adjacent said four outward spacer openings and engaging the inner surface of the envelope for spacing said assembly from the envelope; each peripheral edge of said spacers having at least two spaced retainer recesses each of small depth and relatively large width and positioned between two spacer projections thereof; 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 interfitting the two spaced recesses of said two spacersfor securing said two spacersto said anode and joining them and said electrodes into a self-supporting electrode assembly, at

anode having two separate tongue sections; one" tongue section being angularly bent over the spacer surface and the other tongue section extending away therefrom.

7. In a space discharge device asclaimed in claim 6, said assembly of electrodes'i ncluding a metallic element secured to said other tongue section of said one tongue extending away from the bent-over tongue section.

HERBERT R. JACO'BUS', JR. HAROLD L. LIPSCHULTZ.

REFERENCES CITED file of this patent:

Number 2350303 2355,083 2,402,797 2,433,410" 2,45%?{8'61' 2,464,241 f 2, 16 1,272 23761940 2,486,829 The following references" are of record in the 2,487159'2' Name Date Schade Feb. s, 1933 Rockwood Dec. 16, 194} Seeln Sept. 22, 1942 West May 30, 195151 Krim Aug. 8, 1944 Wood June 25, 1946 Walkere't al. Dec. 30, 194? Wood -Jan. 25, 1949 Krim Mar. 15, 1949 Sue'sholtz Mar; 15, 1949 Wood July 19, 1949 Nov. 1, 1949 Rishe ll Nov; 8. 1949'

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