US2454330A - Positive grid oscillator - Google Patents

Description

J. w. McNALl. ErAL POSITIVE GRID OSCILLATOR Nov. 23, 1948.

3 Sheets-Sheet l Filed April 13. 1944 INVENTORS .IM ,vf/wuz 9- I. HID/G Nov. 23, 1948. J. w. McNALl. ETAL PosITIvE GRIDy oscILLAToR med April 1:5, 1944' s suma-snm z ATTORNEY Nov. 23, 1948. J. w. McNALl. Erm.

POSITIVE GRID OSCILLATOR Filed April 15. 1944 1' Shoots-Sheet 3 ,um hm ArroRNEY Patented Nov. 23, 1948 POSITIVE GRID OSCILLATOB John W. McNall, East Orange, and Alfred H.

Laidig, Bloomfield, N. J., assignors to Westinghouse Electric Corporation,` East Pittsburgh, P a., a corporation of Pennsylvania Application April-13, 19,44, Serial No. 530,890

s claims. 1

'rms invention relates to positive-grid oscu-v lators, also known as retarding field oscillators, and is directed to structural features of such an oscillator of .particular applicability in the more generic disclosure of concurrently filed application of co-inventor herein J. W.McNall, Serial No. 530,889, filed April 13, 1944. j

Electrode spacing having commensurate relation to electron transit distance between the phase `shifts of the oscillation period, introduces problems of mounting, fabrication, adjustment, tuning,` and so forth, not encountered in usual oscillators, especially when the period of oscillation chosen is in the ultra high frequency range. Broadly, the present invention is directedA to the -solution of the several problems enumerated.

More specically, an object of the invention is to provide a hollow body resonant cavity positivegrid oscillator.

4 Another object of the invention is to provide for a grid between cathode and anode each elec-I trically a part with the resonator wall but, as to D. C. potential, electrically separate from either cathode or anode.

'A further object of -the invention is to provide a resonator the wall of which, together with the cathode, anode and positive grid will constitute a self-contained oscillatory circuit capable of hav- 2 mate physical and electrical relation of electrodes;

Figure 4 is a longitudinal sectional view of a hollow body resonant cavity positive-slid oscilmodied construction of hollow body resonant.

lator which is tunable and wherein all electrodes are insulated for separate application thereto o! D. C. potentials;

Figure 5 is a plan of Figure 4;

Figure 6 shows diagrammatically the approximate physical and electrical relation of electrodes of the construction of Figure 4; Y

Figurev 'l is a longitudinal section of af further iustrated 1n said drawing and giving attention ining a D. C. potential on' the positive grid diifering from that on the cathode and anode.`

Yet another object of the invention is to prol vide in a resonant cavity construction` of tube, a

positive -grld rigidly mounted and accurately spaced lbetween a closely spaced cathode and vselector grid. v r

A still .further object of the invention is to provide for adjusting the spacings of cathode to posi- 4 tive grid, selector grid to positive grid and anode yrecitation thereof and by inference from the context.

Referring to the accompanying drawings in which like numerals of reference lindicate similar parts throughout the several views:

Figure 1 is alongitudinal sectional view of aV hollow body resonant cavity positive-gridoscillator embodying tion;

Figure 2 is a cross-section thereof on line II-II;

. Figure 3 shows diagrammatically the approxithe broad concept of our invenitially to Figures 1 to 3, a hollow body resonant cavitypositive-grid oscillator is shown wherein the hollow body l5 is all metal and constituted as a cylindrical outer wall I6' having disc-like end walls Il and i8 sealed at theends of the cylindrical wall. At the mid-part of and sealed to said end walls are collars I9, .20, respectively, which are re-entrant in the sense that they project intov the hollow bodyv coaxially therewith, so their inner `ends are directed toward each other within the body, said ends being parallel to each other and to the end walls of the resonator. Said collars each have a part thereof,'which may be termed an extension of the collar, which projects outwardly from the end wall of the resonator, each said extension having an, appropriate seal therebeyond for maintaining internal vacuum in the y resonator and collars.

` disc;shaped 'and with the axis of the disc coaxial to the axis of the collar and resonator body, thereby positioning the emitting surface transverse to that axis. The body of the cathode is a metallic hollow -body of revolution and consists of a cap portion of cup shape, the closed end of which constitutes the aforementioned disc-shaped part of the cathode andv at the periphery of which is a cylindrical ange 22. Said flange nts over and is secured to a cylindrical head 23 of a housing portion having a cylindrical torso 24 from the other end of which legs 2i project. The head 23 approximates the diameter of the re-entrant collar I9, whereas the torso 24 is of less diameter and the legs 25 spread to engage the inside of said collar and are spot welded or otherwise secured thereto. The inside of said collar I9 may be provided with a forwardly directed shoulder 26 for engagement by the ends of said legs 25, thereby serving to locate the cathode emitting surface precisely parallel to the said shoulder, which is in turn parallel to the end of said collar.

'I'his cathode structure is part of the wall of a resonant cavity, and the provisionof head 22 substantially the same diameter as collar I9 and separated therefrom by only a narrow peripheral gap, obtains virtual continuity of surface for high frequency oscillation and negligible impedance thereto across the gap, The structure, on the other hand has a tendency to prevent heat flow from the cathode to said collar, aiding, therefore in maintaining desired cathode temperature. 'I'his same cathode construction is employed likewise in the other tube constructions hereinafter described.

A heater filament 21 is shown within the cathode body, said filament being mounted on lead-in wires 28 which extend to the exterior through a glass press 29 formed as part of a re-entrant glass stem 30. The rim of said stem is sealed to the end margin of a suitable metallic ring 3I, the other end margin of which is secured, as by welding, to the margin of the end of the collar I9 protruding from the resonator body. Ring 3I is of material having substantially the same coeiiicient of expansion as the glass, a material manufactured under the trade name Kovar, in accordance with disclosure in Patent 2,062,335 of December 1, 1936, to Howard Scott, being the one preferred.

The other collar 20 is shown as having a grid 32 across the inner end thereof, this grid being distinguished herein from subsequently described grid by referring to it as the selector grid. Said selector grid is parallel to the cathode emitting surface and otherwise fulfills the requirements therefor as explained at length in said concurrently filed application.

Within said collar 20, spaced from the wall thereof and spaced from and parallel to said selector grid 32 is an electrode 33, which in the figure being described, is utilized as an anode. As here shown, said electrode 33 is in the form of a disc coaxial with the axis of the collar and resonator body and has a metallic stem 34 extending lengthwise of the collar and projecting from the outer end thereof for lead-in purposes. A domelike glass seal 35 is sealed to the stem 34 next the outer end thereof, the rim of the dome being sealed to a ring 36 in turn sealed, as by welding, to the said collar. Ring 36 may conveniently be a duplicate in size and material of ring 3I at the cathode end of the device.

In parallelism to and between the aforementioned selector grid and cathode, is another planar grid 31, herein distinguished for reference purposes by the appellation thereto of the title of positive grid. This positive grid 31 extends outwardly beyond the cylindrical region between said cathode and selector grid and toward the cylindricalwall I 6 of the resonator body. A plurality of supporting prongs or wires 38 project radially inwardly through said wall in the plane to said positive grid and have soldered orother attachment to said positive grid so as to rigidly mount the same in place. Said wires or prongs 38 are coaxially sealed, as `by glass beads 39, within tubes 40 soldered or otherwise secured in appropriate holes in the said cylindrical wall. This ccnstruction affords adequate insulation and support for the grid and. also provides a vacuum seal f orthe hole and Wire.` One of said wires may be utilized as an electrical connection for application ofdesired potential to the said positive grid. To prevent highfrequency radiation from leaking out by way of said wires, a suitable choke 4I is applied to each. i

Capacity coupling between the positive grid and the resonator wall for high frequency conduction continuity and for rendering the chamber resonant is provided in the form of cylindrical shells 42 spaced from the walls of the resonator body, a distance adequate to prevent passage of D. C. potential. These shells are coaxial with the resonator cylindrical wall and have inturned flanges 43 next the positive grid, said flanges being juxtaposed upon and secured to the said grid. Support for the said shells is obtained by the same radially disposed wires 38, which support the attached positive grid. From the construction shown of parallel and close association of cylindrical shells 42 to the cylindrical resonator wall I6, continuity for high frequency oscillation is provided and at the same time discontinuity for D. C. current flow is obtained. A coaxial line output 44 the center conductor of which loops into the resonator chamber is provided as usual with hollow body high frequency resonators.

Electrode spacing and connections are dealt with more fully in the said concurrent application, for use of the device as a positive grid oscillator. Suffice it to say herein that, as indicated by Figure 3, the spacing of the several electrodes is related to electron transit time and here shown as such that an electron may travel from cathode 2I to positive grid 31 and from positive grid 31 to selector grid 32 substantially in the time required for oscillating phase shift of 180 each. Also spacing of the anode from selector grid 32 is substantially a distance representing transit time of an electron therebetween during a phase shift so the electron makes the round trip from said selector grid, to the anode and back to the selector grid during substantially a oscillating phase shift. Because of the metallic continuity from cathode mounting to selector grid mounting, those electrodes are shown in Figure 3 as connected. Other relationships and character of electrodes may, however, be provided as l found desirable or to carry out the operation of the device in any manner, such as described in said concurrently led application.

While Figures 1 to 3 illustrate the fundamental inventive concept, it is Within the scope of the invention to vary the spacings and electrical connections of the electrodes as found desirable. Furthermore, it may be stated that the electrode referred to herein as the anode occupies the position usually ascribed to an anode, and the term is thus used to distinguish it from other electrodes without restriction as to the functioning thereof. Said anode may be utilized for receiving electrons, may be utilized for reflecting primary electrons. or may be used to emit secondary electrons, and to indicate more definitely this inclusive characterization, may be more generally referred to as an electron-pulling electrode.

In Figures 4 to' 6, structure embodying the invention is shown wherein all electrodes are electrically insulated one from another and wherein the several electrodes have adjustment for spaca contact terminal.

the end wall of each section, is a hollow collar,V

the one for the cathode being identiiied by numeral ll and the oppositeone for the selector grid and anode being designated by numeral l. The inner ends of these two collars are directed toward each other within chamber 4I and said ends are parallel to .each other and to the end walls of the said chamber. A cathode 2| as previously described with cylindrical flange 22 on a head It of a housing having cylindrical torso 24 and legs 25, limited in position by shoulder 26 is carried by collar I8. the cathode, of course,

. having a heater 21 (see Fig. 6)

At the outside of end wall ll having collar 48 is a virtual extension 4l* of said collar to which a metallic ring 3| is secured by welding an end margin within said collar, the other end of said ring being Ysealed by the flare portion of re-en-` 3o The other collar Il is traversed at its inner end trant glass stem l0.

by selector grid 32 as in the construction previously described, said grid being secured to the collarand situated in parallel spaced relation to the cathode. Within said collar, spaced from the wall thereof and spaced from and parallel to said selector grid 32, is, using the term broadly. an anode I3 having a metallic stem 34* extending lengthwise of the collar and projecting beyond the far end thereof. In the, present showing said stem is made longitudinally adjustable, thereby enabling the anode to be moved toward and away from the selector grid.

Support for the stem Il* is from the resonator end wall Il at the outside of which protrudes a virtual extension Iil ci collar 49, a metallic ring 3l being welded or otherwise secured to said co1.- lar. The outer end of said ring has a glasscollar 5l sealed thereto and to the far end of the glass collar is another ring 5I, which in turn has secured vacuum tight at itsfar end an annulus 'i2 screw threaded at its outside and connected vacuum tight at its inside to the said stem by a ilexible diaphragm I3. Outside the threaded annulus is an internally threaded knob Il having an end wall rotatableupon the stem and engaging a shoulder I! formed on the stem. Outward displacement of the knob longitudinally of 'the stem is prevented by a cap IB held on the said stem by a set screw or otherwise as found desirable. The outside of said knob is provided with an insulating covering Il to avoid subjecting the operator to potential applied to the stem by'way of cap 56 which is conveniently used as In the showing of Figure`4, the end walls 41 for the resonator body are made movable with respect to the positive grid 31. As in the previously described construction. said positive grid extends between the cathode 3| and selector grid 32 parallel thereto and radially outward to the vicinity of the cylindrical side wall of the resonator, andjin this instance is shown projecting between -the facing ends of the side wall sections. Capacity coupling between said positive grid and the resonant is provided. as before. in the form of -cylin drical shells il* spaced each from one said resonator wall section a distance adequate to prevent passage of D. C. potential.` These shells are coaxial with the respective sections ofthe resonator.Y within which situated. and are shown with outturned iianges It* next the .positive grid, said flanges being-juxtaposed upon and secured to the vsaid grid at its peripheral margin. Support for said grid and shells is obtained by of radial wires Il, which are introduced through glass seals in this instance formed` integrally with a glass ring Il coaxially situated around, but-spaced outwardly from the periphery of said positive grid I1 and outside and spaced from resonator walll sections 46. At top and bottom edges of this glass ring in virtual continuation thereof are metallic rings having substantially the same coefiicient of expansion as the glass ring and preferably of the aforementioned Kovan At' the marginof each said metallic ring Il remote from the marginsealed in the glass, is secured. as by welding. an annulus I0 the outer periphery of which is screw threaded and receives a threaded collar Il, the other end of which is ilanged'inward. as at I2, to overlie the end wall Il of the resonator. The outside of thiscollar 6I is covered with insula'tion B3 that it maybe grasped and operated with immunity to electrical shock to the operator. Between saidannulus Il and end wall 41 afiiexible member or bellows M is secured vacuum tight, said bellows'preferably exerts reilient pressure longitudinally or axially thereof, thereby tending to separate the end wall I1 from the annulus when unscrewing the collar 6|. The selector grid mounted on re-entrant collar I! from end wall 4l is thus adjustable with respect to the positive grid I1, and similarly cathode 2l is independently adjustable with respect to said positive grid. construction accomplishes a support of each ectrode electrically insulated from support for all other electrodes.

Whilethe constructions so far described utilize hollow body resonators which are included within the evacuated region, the invention also contemplates the use of resonators exterior to the evacuated region. Such a-construction isshown by Figures 7 to 9, wherein theevacuated region is confined to a cartridge-like enclosure. As shown, the construction is substantially an adap tation of the collars Il and 20 of Figure l, prov viding a glass seal-.betweenv the collars, said seal supporting thepositive grid.

Describing the showingofFigures'l to 9 more in detail, axially aligned metallic collars i6, Il

are provided the facing ends of which are parallel. One of these collars, 66,-'su'pportsa cathode 2| in front thereof in accordance with descriptions heretofore given in connection with constructions of the other ilgures of the drawings, and corresponding reference numerals from Figure' l are applied without repetition of the description.

Similarly, the other collar 81 hasa" selector grid atits inner-end and contains an electrode for distinguishing purposes-again called an anode) supported by a stem sealed through al glass dome,

and reference numerals from Figure 1 are again applied without repetition of description. Difference in the collars from the showing of Figure 1 exists in the provision of radial fianging or enlargement of said collars at 88 inthe vicinity of sealing of the Kovar" rings ll and J6 thereto. Virtual extensions I9 of said collars project from the said enlargements in directions away from each other and coaxially to and around said rings. Projecting toward each other from said enlargements and situated around said collars are glass rings 10 for insulating and sealing purposes. The outside diameter of these glass rings is substantially the same as for the extensions 69. A washer-like conductive plate 1| has its inner margin situated between and sealed to the contiguous ends of the glass rings 10, said plate extending radially outward from said rings and having an outer peripheral cylindrical rim 12 thereon the outer face whereof is screw threaded. 'I'he inner margin of the said plate next the said rings has the positive grid 31 secured thereto, said grid being situated between and parallel to the cathode and selector grid.

The said collars 66, B1 and their extensions 69 constitute inner cylindrical walls for an annular resonator chamber 13, the outer wall of which is composed of cylindrical sections 14 having contiguous ends flanged, as at 15, and seated against plate 1I within rim 12 thereof. Clamping nuts 16 on the said rim engaging the outer flat faces of said ilanges clamp the said sections in axial alignment coaxially to the inner wall of the resonator.

The outer ends of the resonator chamber are closed with insulating spacers 11. Within the chamber 'I3 next each outer end thereof is an inwardly facing piston 18 having sliding contact with one cylindrical wall of the resonator and having capacitative relation to the other cylindrical wall thereof so as to pass high frequency current but prevent passage of the D, C. low y potential. Arbitrarily we show contact of the piston with outer wall 14 and capacitative relation to wall 69 but this arrangement may be re versed if desired. Each piston is carried by a plurality of plunger rods 19 which extend outwardly through the spaces 11 and are attached to a wheel-like controlling handle y80. An output coupling 44 is provided as before, to take advantage of the generated power.

Spacing of the electrodes and constitution of the so-called anode as electron receiving, reflecting or multiplying may be carried out in accordance with the disclosure of said concurrently filed application, wherefore specific showing of spac ing of electrodes in Figures 3, 6 and 9 herein is to be considered illustrative rather than restrictive.

It will be noted with respect to -all showings herein that special care has been taken of making parts on opposite sides of the positive grids as nearly identical as possible, thereby reducing the number of different parts to be fabricated, and lowering costl of tools, dies and xtures in manufacture of the device.

We claim: f

1. An electronic device comprising a cylindrical outer wall having end walls, said cylindrical outer wall and end walls forming a hollow enclosure, collars projecting from said end walls toward each other within said enclosure coaxial with said cylindrical outer wall, an electronpulling electrode within and next the inner end of one of said collars and electrically insulated therefrom, a grid iixed to the electrode-containing collar in spaced parallelism to said electronpulling electrode, a second grid parallel to and spaced from the first said grid and having a part therefrom projecting radially through the said cylinder, and a cathode parallel to and on the opposite side of the second grid from the rst grid and axially aligned with said electron-pulling electrode for directing electrons through the said grids toward said electrode.

2. An electronic device comprising a cylindrical outer wall having end walls, said outer wall and end walls forming a hollow enclosure, a grid transverse to said cylindrical outer wall and parallel to said end walls dividing said enclosure substantially in half and forming the said enclosure into two resonators, collars projecting from said end walls toward each other and toward said grid and coaxial to and within the respective resonators and forming innerl cylindrical walls therefor, an electron-pulling electrode within and electrically insulated from one said collar, a cathode carried by the other said collar, and capacitative coupling in the electrical circuit between said grid and collar and interposed between said outer cylindrical wall and said inner cylindrical walls of each resonator for providing continuity of circuit for high frequency and interposing thereby interruption to circuit path for lowirequency current from said grid to said collars.

3. An electronic device comprising a pair of aligned cylinders, cnd walls at the outer ends of said cylinders, a fixed grid transverse to the axis of said cylinders and at a plane between inner ends of said cylinders, said grid having a peripheral portion projecting between said inner ends of the cylinders, collars coaxial with said cylinders and projecting toward each other and toward said grirlfrom said end walls, a grid at the inner end of one of said collars, said grids being parallel to eachother, an electron-pulling electrode within the` collar having the grid, and a cathode carried by the opposite collar from the one having said electrode therein, said cathode having electrical continuity with the collar carrying the same, and one of the grids having electrical continuity with the other of said collar.

4. An electronic device having a cathode and an opposed electron-pulling electrode and having a hollow body resonator, re-entrant coaxial collars therein, the inner ends whereof are directed toward each other, said hollow body resonator comprising an outer shell in electrical continuity with said collars and providing an inner shell capacitatively coupled with respect to the outer shell, thereby providing high frequency electrical continuity, and a grid physically and electrically joined to the said inner shell and situated between the said inner ends of the re-entrant co'- axial collars. y

5. An electronic device having a cathode and an opposed electron-pulling electrode and having a hollow body resonator having end walls, means providing electrical discontinuity of one end wall to the other, each of said end walls having an outer shell section as part of the resonator body and cach having-a re-entrant collar within said shell section, an inner shell capacitatively coupled with respect to both said outer shell sections, and a grid physically and electrically joined to the said inner shell and situated between the said outer shell sections and said re-entrant collars out of electrical contact therewith. I

6. An electronic device comprising coaxial collars having ends directed endwise toward each other, one having a cathode at its end and the other having a grid at its end, `said collars each having an enlargement thereon, a second grid' between said ends of the collars, insulating rings between said enlargements and said second grid supporting said second grid and sealing the in- REFERENCES CITED v The following references are of record in the le of this patent:

Number UNITED STATES PATENTS Name Date Dallenbach Aug. B0, 1938 Dllenbach July 25, 1939 Varian et al June 30, 1942 Litton Oct. 13, 1942 H8611 May 21, 1946

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