US2460484A - Electrode unit assembly - Google Patents

Description

Feb. 1, 1949. F. H. BEST ET AL ELECTRODE UNIT ASSEMBLY Filed March 5, 1 948 ATTORNEY Patented Feb. 1, 1949 ELECTRODE UNIT ASSEMBLY Fred H. Best, Mountainsideg' and John R. Pierce, Millburn, N. Ji., assignors to Bell Telephone Laboratories, incorporated, New York, N. Y., a corporation of New York Application March 5, 1948, Serial No. 13,256

(Cl. Z50-27.5)

l() Claims. l

This invention relates to electron discharge devices and more particularly to such devices especially suitable for use in ultra-high frequency communication and television systems.

An object of the invention is to attain Vhigh transconductance and high ratio of transconductance to capacitance together with high power output in electron discharge devices for use in broad-bandl television systems, pulse modulation and other ultra-high frequency applications.

Another object of the invention is to insure relatively close spacing between input and control electrode areas to produce high figure of merit ratings for power output devices.

A further object of the invention is to increase Y the eective areas of the cooperating electrodes in the device without sacrificing relatively close space relation over extensive areas of the electrodes.

Another object of the invention is to utilize the unitary mounting of a continuous helical Vwire element on the cathode assembly, which is completely insulated therefrom, as the carrier of high frequency wave energy traveling along the wire to increase the amplified output of the device, in accordance with the traveling wave principle as set forth in a copending application Serial No. 640,597 filed January 11, 1946, of J. R. Pierce.

These and other objects of this invention are realized. by constructions ci the electrode assemly in the device in which a control electrode or element of a relatively iine wire helix is mounted in close parallel relation to the effective emission surfaces of a large area cathode element by an insulating assembly supported in juxtaposition to the cathode surface and in contact therewith, to positively insure that the relation between the electrodes be uniform and stable during operation. lThis is accomplished, in a particular embodiment of the invention, by constructing the cathode of a hollow metallic body, of generally rectangular cross-section and having longitudinal flange portions at opposite and medial points along the short dimensions of the cathode. The configuration of the cathode surface together with the flanges form corner pockets or ridges which provide parallel seats for a Yplurality of insulating rods of suitable dimensions to fit into the seats. larger than the height dimension measured from the flange portion of the cathode so that the rods project beyond the main parallel surfaces of the cathode. A wire helix wound over the rods will be uniformly spaced from the cathode i The diameter of the rods is slightly surfaces and completely insulated therefrom to serve as the control electrode or grid. The pitch, number of turns and lateral relation of the grid determines the high transconductance characteristics of the device. The associate anode 0r output electrode may be mountedin close parallel relation to the main cathode and grid surfaces byvjoining two sections in opposed relation on opposite sides of the unit assembly of the grid and cathode and mounting the combined structure between spacing insulating discs to form an integrated unitary ensemble.

A feature of this construction is that the power output of the device may be increased to any desired value merely by increasing the dimensional areas of the electrodes with the assurance of obtaining accurate space relation of the cooperating electrodes and maintaining stable relation between the electrodes.

Another feature of the invention relates to the collateral space relation of the adjacent turns of the control electrode with respect to an elongated area cathode surface, since the cathode construction together with the insulating spacer rods determine the close'spacing of the grid to insure a relatively high transconductance component and low interelectrode capacitance characteristics in the operation of the device.

A further feature of the invention relates to the support of the grid turns in the unit assembly when the grid is employed as an element of a triode or multiple electrode power discharge device. In addition to the winding of the wire as a helix around the cathode and insulating rod assembly, metallic strips may be interposed between the winding and the rods along the short dimensions wherein a fusible metal coating on the wire or the strips provides a means of anchoring the turns of the grid to the strips during the high temperature processing of the device to insure positive relation of the respective turns of the grid to increase the stability of the grid helix,

These and other features and advantages of f' the invention will be more clearly understood construction of the internal unitary assembly of the electrodes;

Fig. 2 shows the unitaryA electrode assembly removed from theenclosing vessel and illustrated e@ from a dilferent angle than shown in Fig. 1, with one of the anode sections removed and portions of the rods and cathode broken away to clearly set forth the components of the assembly;

Fig. S is a view of Fig. 2 taken on the line 3 3 and showing all the electrodes in cross-section with their cooperating supporting .structure and the terminal conductors associated with the electrodes;

Fig. 4 is an enlarged cross-section view or the various electrodes embodied in the device of Fig. l, taken on the line i-ll of Fig. l, to clearly show the unitary built-up construction of the cathode and grid, in accordance with this invention;

Fig. 5 is a cross-section view of a modified arrangement of the cathode-grid assembly in which separate medial ange extensions of the cathode are joined to opposed channel sections and tubular insulating rods support a helical coil electrode in relation to the active cathode surfaces; and

Fig. `6 shows another form of the vconstruction in `cross-section With rectangular insulating rods mounted at the corners of a modified arrange" Vment -of the cathode to attain the close space relation in accordance Awith this invention.

Referring to the drawings and particularly to Figs. 1 and 2, .the high frequency discharge device -of `this linvention is embodied in a specic structure of a'triode lamplifier tube in which a unitary mount or electrode assembly is enclosed in a highly evacuated glass vessel Il) having a cup stem Il with a central-exhaust tip l2 and a plurality Vof conductors Vl'sealed in a circular boundary in 'the stem. The unitary electrode mount extends within the vessel from the conductors 'which .support it and provides a relatively elongated structure having large electrode areas to attain zhigh power output inthe operation of the i device.

In order to secure optimum eiii'ciency in ultravhigh frequency operation at high 'power rating, -it 'is essential that the transconductance be rel- `atively high and the ratio of transconductance to vinterelee-trede capacitance be of a high order. These characteristics are readily Iobtained in low power devices vof short length since the space re- -lationand other attributes of the assembled electrodes can be accurately controlled to produce the results desired. However, when higher power output is required, it is necessary to increase the length of the electrodes. As the length of the electrodes-is increased, difficulties arise particularly lin relation tothe ne wire grid and cathode spacing for the grid is easily deformed by heat and mechanical stresses or strains. While it is Y of this invention is shown clearly in Fig. 4 that possible to obtain initial spacial relation of the grid latera'ls to the emissive surface of the cathode Yto realize high `transconductance values, such minute space relation, ofthe order of .001 to .063 inch, is generally destroyed when the device is placed in operation due to the temperature and mechanical conditions imposed on the fragile wire of the grid or control electrode.

higher `power outputs. This is effectively accomtheir longitudinal edges.

illustrates a particular embodiment which, however, Inay be modified in various ways to attain the Yresults of this invention. In the particular example shown in Fig. 4, the large area cathode is a hollow sleeve i4, preferably of a highly refractory metal such as molybdenum, which is formed'of two-channel-shaped portions l5 and I6 having angular 'flange projections Il and I8 along The projections are welded in abutting relation to form a box-like .or rectangular cathode body or base for serving as the electron emission source in vthe roperation of the device. The'coplanar medial anges Il and it 'formangle sockets or seats I9 at the four corners of the cathode body along the minor dimensions thereof, The structure also provides relatively large parallel areas along the major vdimensions which .may be coated with emissive material 20, such as barium and strontium oxides, to supply copious electron emission when heated 'to emission temperature, for example, by conyduction from an internal tungsten heater element 2| of 'hairpin configuration having an insulating :coating 22, preferably of a high dielectric composition such as aluminum oxide, thereon.

The cathode body or base is relatively strong since it is made of molybdenum so that high temn perature operation may be realized without danger -of war-ping or distortion. The box-like construction also increases the stability of the structure even though high temperature changes occur inthe operation of the device. The medial flange construction of the channel sections of the cathode provides equal angle seats or pockets at the four corners of the rectangular body which are Ycollaterally uniform in dimensions along the length of the cathode and are contiguously formed in angular relation to the main parallel surfaces of the cathode.

While the length of the cathode ld provides a relatively large surface area for the production of a copious supply of electrons from the emissive material 2l) on the parallel outer surfaces and the structuralconguration increases the stability of the emission surfaces to maintain constant linearity with respect to other cooperating electrodes, a principal function yof the cathode, in accordance with this invention, is to Yform a mounting base or foundation for the support of afsrnall diameter Wire helix serving as the control element or grid. Consequently relatively close lateral spacing, of the order of a few mils, is insured over the eiective emission surfaces to attain high transconductance values and high emciency in ultra-high frequency operation. The ne wire grid 23 is insulatingly mounted on the cathode by the continuous `winding of .001 inch gold-plated tungsten wire around four insulating rods or pillars 2li situated in the 'corner seats of the cathode formed by the angles I9 -created by the lia-nge portions and the short'wall sections Y of the cathode body. The rods are preferably made of high dielectric material, such as a ceramic composition of zirconium oxide, obtainable commercially as Zircon rods. These rods, as shown in Fig. 4, are of solid cylindrical construction. In a typical example, the height of the channel angles may be .040 inch and the rods have a diameter of '.045 inch so that the close spacing attained between the laterals 25 of the grid helix and the active coating 2E! on the cathode, assuming that this coating is .002 inch in thickness, is .003 inch. This construction, therefore, attains uniform space relation between the collateral surfaces of the grid-cathode assembly along the whole length of' the cathode.

In the triode shown in Fig. l, the lateral turns of the grid may be short-circuited to provide a uniform potential electrode by winding the wire over metallic bridging strips 26 of gold-plated nickel, extending between the pairs of parallel rods 2li. The laterals 25 of the grid 23 may be wound at the rate of 200 turns per inch and these closely spaced laterals may be held in uniform relation by fusing the turns to the bridging strips, for example in the high temperature treatment of the electrodes, so that the gold platings of the wire and strips are consolidated to rigidly anchor the laterals in position.

The combined assembly of the cathode and grid provides a unitary construction wherein the stability of the lateral turns of the grid is constant and uniform regardless of the area of the cathode. This is accomplished by determining the dimension of the minor axis of the cathode and the pillar supports for the grid. IThis produces accurate and relatively close space relation of the wire helix and cathode since the'insulating mountingA is controlled by the collateral relation of the rods with respect to the cathode foundation.

' In the construction shown in Fig` l., the rods 24 are longer than the cathode i4 and while the cathode forms the foundation support for the grid helix, the grid assembly including the rods also forms the mounting support for the cathode. "5'

As shown in Figs. 1 and 2, the combined cathodegrid assembly is mounted between end insulating spacer discs 2'! and 28, each of which is provided with a central rectangular metallic socket 29 on the inner surface thereof. These sockets are anchored to the discs by bent tabs exten-ding through the discs. The rods 24 are inserted in the sockets 29 with the ends of the rods in abutting relation to the surface of the discs to centrally mount the rectangular cathode-grid asi sembly within the electrode structure. A flexible connector strip 33 is attached to the lower end of the cathode sleeve as shown in Fig. 2, and extends through a circular opening 3l, shown in Fig. 3, for connection to a stub wire 32 which is attached to one of the conductors I3 in the stem. The internal heater element 2l extending into the cathode has terminations passing through the bottom of thel cathode and coupled to a pair of stub wires 32 which are connected to separate conductors I3 in the stem on opposite sides of the cathode conductor.

The output electrode necessary to complete the assembly of the triode tube, as shown in Fig. 1, is formed of a pair of channel or U-shaped sections, for example of molybdenum, spaced in parallel relation to the emissive surfaces of the cathode I4 in which the short side 33 is coextensivewith the cathode sleeve both along the length and width thereof. riheseY surfaces are spaced at a distance of the order of .020 inch from the lateral wires 25 of the grid to form the receptive surfaces of the output electrode of the device. The anode sections are also provided with relatively long heat radiation surfaces 3d to increase the heat dissipation of the device. The anode sections are held in spaced parallel relation by joined angular stub wires 35 adjacent opposite ends and on opposite sides of the large heat radiation "portionsj A plurality of upright support rods 3S are Welded to the outer ends of the anode sections and extend to the insulating discs 21 :and 28 where they are anchored by short metallic straps 3l on opposite sides of the discs to combine all the electrodes in a unitary structure and rigidly hold the cathode-grid assembly within the sockets 29 in the unit A getter mounting 38 is attached to the upper insulating disc 2-1 by an eyelet connection 39 and the anode assembly is connected to another conductor in the stem by a tie wire 49.

An electrostatic shield formed of two angular sections of sheet nickel is mounted about the lower end of the cathode-grid assembly with one section 4l extending above the lower insulator 28 and the other section Q2 extending below the insulator, both sections being welded to a plurality of conductors i3 extending from the stem, as shown in Fig. 3, and the helical grid being attached to the upper section lil by a strap 43, as shown in Fig. 2. The multiple connection to the grid as provided by the four connections extending from the stern, improves the efficiency of the triode tube when employed in grounded grid amplier circuits in high frequency operation.

While the specific construction of the device in this invention is shown in a triode to attain higher power output, it is, of course, understood that the detailed construction of the cathodegrid assembly may be incorporated in multielectrode devices to attain still higher output in the operation of the device so that the invention need not necessarily be limited to a triode but may find application in various constructions to increase the power output.

Fig. 4 shows a particular embodiment of the cathode-grid assembly to attain relatively close spacial relation between the laterals of the grid and the adjacent active surfaces of the cathode, wherein high transconductance values are attained. In this construction, the hanged portions are formed integral with the channel sections of the cathode sleeve to secure the results of this invention in an expeditious manner.

Fig. 5 shows a different construction in which the flange portions are separate from the main channel sections of the cathode sleeve and the insulating supports of the grid helix are shown as a variation in the combined assembly of this invention. In this arrangement, the :dange extensions may be coplanar lateral strips it disposed between opposed channel sections l5 of the cathode or the flanges may be formed of a` single sheet of metal with a central slot extending along the r' length of the cathode, in which the channels s55 are welded to the strips intermediate the edges to provide the angle seats for a plurality of insulating sleeves lie which may be of a highly vitreous material, such as borosilicate glass. The diameter of the sleeves it in relation to the angle seats of the cathode assembly will determine the spacial relation of the laterals of a continuous helical wire il which is wound tightly around the rods d, to form a continuous coil element surrounding the cathode. The laterals are closely 7 spaced with. respect to thev cathode surf-ace' and uniformly spaced in insulatingY relation along the whole length of the cathode by the corner rodsmounted on the cathode.

Fig. 6 'shows a further modification of the cathode-grid assembly in whichA a channel-shaped section: 138 is provided with iiange extension d@ and is joined to* a pair of angle stripsY d by an'rv intermediate plate 5i. The plate and channel section'form an enclosurey for a heater element 2zlin. which the flat surface of the channel section; isthe only emitting surface. The angle corners; of the cathode construction. form seats for rectangular ceramic rods` 52` and the continuous helical Winding lll completely surrounds the cathode and insulator structure tofprovide relatively close spacing between the laterals of4 the helical electrode` 4l and the emissive surface of the cathode,

In both the modiications, the conti-ol element is a continuous helical coil in which the progressivefturns or lateralsl cooperate with the emissive cathode surface to provide. high transconductancevalucs inthe operation of the device wherein the. continuoushelix may have avariablepotential applied thereto for securing a high amplification output. according to the. traveling wave principle. Of course the structure shown in Fig. l may be modiiiedV tov servein the same capacity by eliminating the bridging strips 2S.

While several structural assemblies have been disclosed, inV accordance with. this invention,V it is, of course, understood that various modificationsmay be made in the speciiic structuresl disclosed without departing from the scope of. the l.

inventionfas defined in the appended claims.

What is claimed is: Y

1.. A unitary electrode assembly for electron discharge devices, comprising a metallic body oi' box-like conguraticn, ange extensions project.- ing from oppositely disposed surfaces of said body, a plurality of. insulating rodsin contact with said extensions and the adjacent surfaces of said body forming spacers in relation to the main surfaces of said body, and a winding having spaced turns s encompassing said body and rods andsupported by saidrods.

2 A unitary electrode assembly for electron discharge devices,v comprising a hollow metallic body of box-like coniiguration, ange Aextensions projecting from oppositely disposedr surfaces of said body atv medial points thereof, a plurality of insulating rods in contact with said extensions and the adjacent surfaces of said body forming oversize spacers in relation to the main parallel surfaces oi said body, longitudinal metallic strips bridging the gap between adjacent rods on opposite sides of said body, and a winding having spaced turns encompassing said body and rods and in Contact with said strips.

3. A. unitary electrode assembly for electron discharge devices, comprisingra hollow metallic body of box-like configuration, flange extensions projecting from oppositeiy disposed. surfaces of said body at medial points thereof, a plurality of insulating rods in contact with saidr extensions andthe adjacent surfaces of said body forming oversize spacers in relation. to the mainparallel surfacesof said body, longitudinal metallic strips bridging the gap between adjacent rods on opposite sides of said body, a helical wire winding having spaced turns encompassing said body and rods. and in4 contact with said strips, and means iixedly attaching the turns of said winding to saidstrips. k

4. A unitary electrode assembly forA electronI discharge devices; comprising; a hollow rectangular metallic' body having longitudinal medial flange portions extending outwardly from;the. short dimensional: sides thereof, insulating rods iitting into sockets formed by said iiange portions and the adjacent wallsv of said body, said rods having surfaces extending beyond the'planel surfaces of said body, and a wire helix conti-ne uously wound around said rods spacing the turns in close parallel rela-tion to the main surfaces ot saidbody.

5. A unitary electrode assembly for electron` discharge devices, comprising a hollowy rectan -gular mctallomember having a pair of 'similar channel portions withv oppositely disposed flange extensions at Vopposite edges, said portions being fitted together with .said ange extensions in abutting relation,V ceramic rods mounted in the angles formed. by said iiange extensions at Ythe four corners of said member, and a. helical wire element embracing said rodsand insulatingly spaced, thereby from said hollow member.

6l A unitary electrode assembly for electron discharge devices, comprising .a hollow rectangular metallic member having a pair ofl similar channel portions with oppositely disposed ii'ange extensions at opposite edges, said. portions being fitted together with said iiange extensions in abutting relation, ceramicrcds mounted in the angles formed by said flange extensions at the four corners of said member, said rods having a diameter slightly greater than. the smallest dimension of said channel portions, and a helical wire continuously'wound about said rods insulatingly spacing the turns thereof from said holiow member. Y

7. A unitary cathode-grid assembly for elec- Y tronY discharge devices, comprising a large hollow metallic cathode element of rectangular crosssection with flange portions yon opposite surfaces,

ceramic rods seated in the cornersof said element against said ilauge portions, said rods having a diameter slightly greater than half the dimension of said surfaces, and' a wire helix applied to said rods providing spaced turns in close spaced relation to the parallel" surfaces of said cathode element.

8.. An electronic discharge device comprising an enclosingvessel, an electrode assembly therein including a rectangular hollow cathode having intermediate ange portions parallel to the main surfaces thereof, insulating spacer members mounted in parallel relation on said flange portions, axhelical. wire element supported on and sur-rounding` said spacer members spacing the turns ofv said wire element in parallel relation to the main surfacesof said cathode, and an anode portion opposite each main surface oifsaid cathode with the laterals o said wire element therebetween.

9. An electron discharge device comprising an enclosingl vessel, an electrode mount therein including a central rectangular cathode of relatively long length having portions projecting outwardly therefrom along the axis thereof, a heater element enclosed within said cathode, a plurality of cylindrical insulating rods coextensive with said cathode and fitted in the corner angles formed by said portions, a helical wire grid surrounding said trods and insulatedirom said cathode by said rods,

said grid being unitarily supported by said cathyode,. and a pair of anode surfaces in parallel. and spaced relation. to said grid and cathode surfaces 9 and transverse to the angle portions of said cathode.

10. An electron discharge device comprising an enclosing vessel, a unitary multiple electrode mounting therein including a cathode, grid and anode, end spacer discs and conductors for the electrodes sealed in said vessel, said cathode being a hollow elongated metallic sleeve of two flanged channel portions in juxtaposed relation forming a cross-sectional configuration having angle seats at the corners thereof, insulating rods mounted in said angle seats and extending longitudinally beyond the ends of said sleeve, said rods in assembled relation increasing the Width dimensions with respect to said sleeve, longitudinal metallic strips along the outer boundaries of said rods, a helical wire grid embracing said rods and strips and spaced in parallel relation to the exposed surfaces of said sleeve, centrally mounted metallic sockets on said spacer discs receiving the ends of l said rods for supporting said cathode sleeve and grid, a heater element extending within said sleeve, a pair of U-shaped anode sections dis posed opposite the parallel grid and cathode surfaces, metallic spacer brackets joining said anode sections together, support rods for said anode sections extending to said spacer discs and locking said cathode-grid assembly` therebetween, leads from said anode, cathode and heater elements connected to individual conductors, an angular shield adjacent one of said spacer discs segregating the anode lead from the cathode lead, and a conductive connection between said grid and said shield, the remaining conductors being attached to said shield.

FRED H. BEST.

JOHN R. PIERCE.

No references cited.

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