US2454298A - Electronic tube - Google Patents

Description

Nov. 23, 1948. I H. A. ZAHL ETAL I 2,454,293

ELECTRONIC TUBE Filed July 29, 1945 2 Sheets-Sheet l INVENTOR HAROLD A ZAHL GLENN F. ROUSE 7 JOHN G/oRHAM Patented Nov. 23, 1948 ELECTRONIC TUBE Harold A. Zahl and Glenn F. Rouse, Long Branch, and John E. Gotham, Spring Lake, N. J.

Application July 29, 1943, Serial No. 496,654

4 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3'70 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to us of any royalty thereon.

This invention relates to improvements in electronic tubes, and more particularly to improvements in oscillator tubes for the generation of ultrahigh frequency energy.

A number of difficulties arise with high-power oscillator tubes working at ultrahigh frequency. It is difficult to obtain enough cathode area for adequate electron emission. There is a sharp break in the tuned filament circuit (with respect to radio frequency energy) between the relatively thin wire leads of the cathode and the more massive external part of the filament-tuning circuit.

One particular oscillator tube which is efilcient and desirable in many respects is the tube disclosed and claimed in a copending application of Harold A. Zahl, Serial No. 473,556, filed January 25, 1943. This tube raises a difficulty because, in order to obtain adequate cathode emission, four electrode assemblies or so-called barrels have been employed, instead of two. The four filaments require four pairs of leads, and four glass stems to seal the leads, all of these stems being located relatively close together, thus making the tube a difficult glass-blowing job and assembly job.

One object of the present invention is to generally improve electron emission tubes. Another object of the present invention is to overcome the difficulties and disadvantages pointed out above. Another object of our invention is to obtain maximum cathode emission with minimum power consumption for cathode heating. Another object of our invention is to provide a cathode-tuning circuit which is very efiicient for radio frequency oscillation. Still another object of our invention is to provide an efiicient tube of simplified construction.

To accomplish the foregoing objects and other objects, some of which hereinafter appear, our invention resides in the electron tube elements and their relation one to the other as are hereinafter more particularly described in the following specification. The specification. is accompanied by drawings in which: s

Figure 1 is a front elevation of an electronic tube embodying features of our invention;

Figure 2 is an end elevation of the same;

Figure 3 is a longitudinal section through a cathode unit made in accordance with our invention;

Figure 4 is a longitudinal section through the anode lead of the tube;

Figure 5 is a schematic diagram explanatory of a feature of the tube;

Figure 6 is a modification thereof;

Figure 7 is a diagram schematically showing the external tuned circuits of the tube;

Figure 8 is a plan view of the anode structure of the tube;

Figure 9 is a front elevation of the same;

Figure 10 is an end elevation of the same;

Figure 11 shows a detail of the anode structure;

Figure 12 is a plan view of the grid structure;

Figure 13 is a front elevation of the same;

Figure 14 is a transverse section taken approximately in the plane of the line l4-l4 of Figure 12; and

Figure 15 is a section taken approximately in the plane of the line l5-l5 of Figure 3, and is explanatory of a step in the fabrication of the cathode unit.

Referring to the drawing, and more particularly to Figures 1 and 2, the particular tube there shown comprises spaced anodes l2, connected by anode-to-anode circuits or loops l4. Grids I6 are disposed within the anodes l2 and are connected by tuned grid circuits or loops l8. Cathodes (not visible in Figures 1 and 2) are disposed within the grids I6 and are carried at the upper ends of tubular cathode leads 20. The anodes are supported by anode leads 22, and the grid circuits are supDQrted by leads 24.

The operation of this particular tube may be explained with reference to schematic Figures 5, 6 and 7. Figure 5 shows how the anodes I2 are connected by a preferably U-shaped resonant anode circuit I4, while the grids [6 are connected by a second preferably U-shaped resonant circuit [8. The cathodes are indicated at 26. Referring now to Figure 6, it will be seen that the circuit is' substantially the same, except that two tuned grid and anode loops have been provided on opposite sides of the grids and anodes. It will be understood that the oppositely-directed anode circuits l4 correspond to the structural parts [4 shown in Figures 1 and 2, and that the oppositelydirected grid circuits [8 correspond to the structural parts l8 shown in, Figures 1 and 2.

The external wiring is schematically shown in Figure '7. For the sake of clarity this is based on the simplified showing of Figure 5. In Figure 7, it will be seen that external anode leads 22 are shorted by an adjustable shorting bar 28. The anodes may be operated at either ground potential or at a high positive potential (with restem or other suitable metal.

'spect to direct current) and this is applied by means of a lead 3B. The cathode leads 2!] are tuned by means of an adjustable shorting :bar 322, and the cathodes may be connected either to ground or to a source of high negative potential (with respect to direct current). In the present case they are grounded at 3d. An appropriate grid biasing potential may be applied to the grids through another connection 24.

The power output from the tube may be taken from either the anode circuit or the cathode circuit. This may be done by means of an appropriate transmission line, but in the present case the output is schematically shown as being delivered directly to the poles of an antenna 38.

The features of the present invention relating to the cathode unit may be described with reference to Figure 3 of the drawing, in which t e cathode 26 is a cylinder made of a. suitable cathode metal (for example, sheet nickel) and is secured in coaxial relationto a tube 38 made of a suitable lead-in metal (for example, Kovar).

' The cathode cylinder is closed at the top by means of a flanged disl; or cap dfi. Tube SS preferably has a diameter approaching that of the cathode,

and in the specific unit illustrated the structure appears to be one continuous element, the difference in thickness for the cathode being very slight, alt ough exaggerated in the drawing for the sake of clarity. The coaxial relation of the cathode and cathode lead is very desirable for eiiicient conduction of high radio frequency energy, and constitutes one of the main advantages of thepresent improved cathode unit.

' The heating filament 32 may be made of tung- To energize the filament, a pair of leads may be used within'the tubetEb-ut we prefer to connect the upper end of the filament to the disk'fillas shown, sothat --the circuit may be completed by the addition of a single wire i i running through tube 38. This wire is supported near its lower-end-bymeans of an insulation orglass bead Ma. 'The wire 44 and glass bead are preferably substantial in dimension so that-the wire will require no further support to'keep-it in the-desired preferably coaxial position. The lower end'of filamentfiz-is 1 connected to the upper end of wire i i by meansof a small metallic connector'tfl.

This is-generally cylindrical andprovided'with a small'hole at the top to receive the lower end of the filament, and a large hole at the bottom to receive the top end of --wire 44.

To-assem'ble the parts of the tuba-the upper end of thefilament-is welded to disk-Ml before disk idis welded to cylinder ZB. The lower end of filament d2 iswelded to connector d8 before cylinder "2% is secured to tube 38. secured within tube 33 by means of glass bead 46 before the cathode assembly is secured to the The wire 44 is lead 38. The twoassemblies are then put'together, the-lower end of the cathode cylinder26 icing welded to the upper end of tube-3B. Diametrically opposed holes-i! are provided near the upper end of tube 38, and by working through these holeathe operator makes sure that connector i8 is in proper position on wire 4d, followof the main envelope.

tate sealing to the glass envelope.

An important benefit of the cylindrical cathode i its large area, thus making possible substantial electron emission. However, to heat a large ndrical cathode instead of a thin filament raises considerable difilculty. We have found that it is feasible to use an oxide coating for the cathode even though the cathode is used in a relatively powerful oscillator for transmission When using an oxide coating, the cathode will operate at relatively low temperature and the cathode may therefore be suficiently heated without difilculty by means of a simple internal heater filament, as above described. An appropriate coating of barium or strontium carbonate or a combination of these compounds is applied to the cathode surface, from which the desired oxide coating is later formed while the tube is on the pump. The carbonate coating may conveniently be applied after completion of the structure of the cathode unit,

The anode structureis illustrated-in Figures 9. and 10 of the drawing. The anodes are sheet anodes are secured. on opposite sides of the anode circuits or loops. More specifically, the loops are made of channels 58 and 60,'closed at the ends by U-shap-ed pieces 62. The inwardly-turned flanges (i i of the channels-are cut away at the center as indicated at 66, thus facilitating bending of the-metal to conform to the cylindrical anodes 58. Top and bottom plates 68 and 10 may be secured toitheanodes, and have their inwardly-directed "ends overlaying the channels The anodes maybe completed by cooling fins 'M, which in the present case are troughshaped pieoesof metal having bent-over ends. The backs of the troughs are secured to the outside of the cylinders 56,while the ends are secured to the top and bottomplatesfit and H1. vIt will be understood that all of thelparts of thestructure are secured together by welding'or other appropriate method.

Reverting to Figures 1 and 2, the anode structure is supported by the anode leads 22, which extend-upwardly throughthe glass envelope of the tube. The-leads=22 are connected to the anode structure by means of yoke-shaped pieces yoke isprovidedwith an internal-threaded boss 8!], the'lower end of which is slit to straddle the yoke ldand is secured thereto, as by means of a pin 82 which is preferably welded in position.

The anode lead itself is shown in Figure l, in which it will be seen that the lower part 84. is solid and is threaded at85 to mate with the threaded hole 88 of the yoke (Figures'lO and 11). The upper part' ll (Figure 4). of the anode lead is tubular and is preferably made of Kovar to-facili- The solid part 84 and the tube 90 are secured together, as by means of welding or the use of a pin 92, or both. The upper'end of tube 90'is sealed'by' a plug'94, which may be welded in position.

The grid structureis-shown in'Figures 12, 13 and 14 of the drawing. Thegridsare made of vertical wires H10, the lower ends of Whichare welded on the outside of a short tube or mandrel I02. The wires are preferably in pairs, that is, relatively long wires are reversely bent at the top, and the open lower ends are secured to the mandrel. The upper ends may be bent inwardly to partially close the upper end of the grid, as is best shown at I04 in Figure 12. The resulting wire cage may be reenforced by circular wires I06.

The grid circuit structure is made of metal channels I08 and III), closed at the ends by U-shaped pieces II2. Sheet metal ears H4 are added at the ends to receive the support wires 24 (Figures 1 and 2), which pass through the glass envelope of the tube.

The grids are secured to the grid circuits by pieces of sheet metal I I6 (Figure 12), which are bent around the mandrels I02. The ends of the pieces H6 are turned outwardly and are secured directly to the outside of the channels I08, IIO. It will be understood that the supports IIG are so dimensioned as to locate the grids coaxially within the anodes.

Reverting to Figures 1 and 2, it will be seen that the glass envelope I20 is generally cylindrical, with the tuned circuits I4 and I8 disposed longitudinally thereof. The envelope is exhausted through a tubulation I22. The grid leads 24 pass through downwardly-projecting glass stems I24. These are spaced widely apart and are far from the other stems of the tube. The anode leads 22 pass through upwardly-directed glass stems I26. These are remote from the other stems, thus facilitating the glass-blowing operation, and insuring against breakdown under high voltage. The cathode leads 20 pass downwardly through glass stems I28. These are remote from the other stems, and are far more convenient to make than is the case with the four-barrel tube of the patent application, Serial Number 473,556, aforesaid, in which four independent glass stems are located in closely adjacent relation.

It may be helpful to set forth the specific dimensions of a few tubes made in accordance with the present invention. These tubes were designed to oscillate at about 600 me. In the case of the particular tube illustrated, the cathode was made of 0.005" thickness nickel and had a diameter of 0.395". The overall length of the cathode was 1%". The effective or oxide-coated length of the cathode Was 1". The cathode can was mounted on a seamless nickel-plated Kovar tube, having a diameter of 0.375".

The sides of the grid loop were made of 0.010" channeled tantalum, the vertical inside width of the channel being A. The ends were closed by U-shaped pieces of tantalum having a thickness of 40 mil. The length of the grid loop was 4" inside, and the width of the grid loop or spacing between its sides was inside. The inside diameter of the grid cage was 0.528". The length of the grid cage was 1%". The cage was made of 20 equally-spaced wires, the wires being 12 mil 6 ode was 1", and the spacing between centers of the two anodes was 1%".

In another example having a larger barrel, the cathode was made of 0.005" thickness nickel formed on a mandrel having a diameter of 0.515". The overall length of the cathode was 1%. The effective or oxide-coated length of the cathode was 1". The cathode can was mounted on a seamless Kovar tube, having a diameter of The grid loop was dimensioned as before. The diameter of the grid cage was 0.635" 0. d. and 0.611" 1. d. The overall length of the grid cage was 1%". The cage was made of 32 equallyspaced wires, the wires being 12 mil platinumclad molybdenum. The grid was made on a copper mandrel having a diameter of 0.629".

The anode loop was dimensioned as before. The anode tubes were made of 0.020" tantalum having an inside diameter of 0.794". The length of the anode was 1" and the spacing between centers of the two anodes was 1%,".

In still another tube, the cathode diameter was increased still further from 0.515" to 0.652". In both of these cathode units, the Kovar cathode lead was kept at a diameter of only thus necessitating an inward step (preferably sloping or frustro conical) between the cathode can and the Kovar lead. This was done mainly because seamless Kovar tubing is not at present available in sizes larger than and we encountered difliculty in maintaining proper vacuum when using seamed instead of seamless Kovar tubing. Moreover, there is greater difiiculty in sealing a glass stem to a lead when the diameter is too great. It should be noted, however, that even with a reduction in diameter between the cathode and the tubular lead, there still remain the important advantages that the lead is symmetrically and coaxially related to the oathode, and that the lead is a large-diameter, efficient conductor for ultrahigh frequency energy.

It will be understood that the foregoing specific dimensions are given solely by way of exemplification, and not in limitation of the invention.

It is believed that the construction and assembly of our new electronic tube, as well as the advantages thereof, will be apparent from the foregoing detailed description. It will also be understood that our new cathode unit is of value for use in tubes different from that here disclosed, although it is of particular value for the present tube.

It will be apparent that while we have shown and described our invention in a preferred form, changes and modifications may be made in the structure disclosed without departing from the spirit of the invention as sought to be defined in the following claims.

We claim:

1. An oscillator tube for generating ultrahigh frequencies, said tube comprising an elongated envelope, an approximately elliptical circuit disposed inside the envelope in the direction of the axis of the envelope, a second approximately elliptical circuit disposed generaly parallel to the first, anodes secured directly on the outside of each side of said first circuit, a grid disposed within each anode, the ends of said grids projectin-g beyond the ends of said anodes and being secured directly to the sides of said second circuit, cathodes inside said grids, each cathode including a cylindrical can having a heating filament therein, tubular cathode leads extending from the cathodes transversely of the enveloped axis through the side wall of the envelope, additional 7 filament-heating leads running through said tubular cathode leads, grid-leads extending through .the envelope, and anode leads extending from the 'the envelope in the direction-of theaxis of the envelope, a second approximately elliptical cirouit disposed generally parallel tothe firstlin revgeneratively-coupled relation thereto, anodes secured'directlyon the outside ofeach'side-of said first circuit, a grid disposed within each anode,

the ends of said grids projecting beyond the ends of said anodes and beingsecured directly to the sides of said second circ'uin cathodes inside'said grids, each cathode including an oxide-coated cylindrical can having a heating filament therein, tubular cathode leads extending from the cathodes transversely of the envelope axis through the sidewall of the envelopasaid tubular cathode leads having a diameter substantially equal to that of the cathode cans, additional filament-heating leadsrunning through-said tubular cathode leads, grid leads extending from the remote ends of the grid circuit through the envelope, and tubular anodeleads extending from the anodes through the envelope in a'direction transverse to the envelope axis.

3. A cathode structure comprising a tubular member, a heating filament at one end-of said member, a filament lead extending from the other end of said member to a point therein in the Vicinity of said filament, said member-havingian aperture at said point 'to permit entry of a tool for fastening said filament to said lead.

4-. A cathode structure comprising a tubular member, a'heating filament at one end of said member, one end of said filament being co ected to said member, the other end of said fi ament having a connector welded thereto, a fil ment lead'extending from the other end of said ember to-a point therein in the vicinity of said connector, said member having an aperture at said point to permit entry of a tool for fastening said connector to said lead.

HAROLD A. ZAHL. GLENN F. ROUSE. JOHN E. GORHAM.

REFERENCES CITED The followingreferences are'of record in the rfile of this patent:

UNITED STATES PATENTS Number Name Date 1,650,232 Pickard Nov. 22, 1927 1,877,708 West Sept. 13, 1932 1,886,705 Lucian Nov. 8, 1932 1,924,319 Hull Aug. 29, 1933 1,997,019 Schloemilch Apr. 9, 1985 2,006,904 Runge et al July 2, 1935 2,057,170 Usselman Oct. 13, 1936 2,108,640 Bieling Feb. 15, 1938 2,224,649 Harris Dec. 10, 1940 2,239,303 'Purrington Apr. 22, 1941 2,367,332 Bondley Jan. 16, 1945 FOREEGN PATENTS Number Country Date 601,155 France Nov. 26, 1925 Certificate of Correction Patent No. 2,454,298. November 23, 1948. HAROLD A. ZAHL ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 50, for 1%" read 1% column 6, line 74, claim 1, for enveloped read envelope;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of April, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

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