US2418117A - Electron discharge device - Google Patents

Description

Apri L 1 7-: D. A. s. HALE ET AL I 9 89 ELECTRON DISCHARGE DEVICE Filed May 29; 1944 3 Sheets-Sheet l 0.14.5. HALE MLRONC/ M/VENTORS' A TTORNEV April 194? D. A. s. HALE ET AL 2,413,117

ELECTRON DISCHARGE DEVICE Filed May 29, 1944 s Sheets-Sheet 2 DA .$.HALE

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INVENTORS' E KL. RONC/ A TTO/Q/VEV Patented Apr. 1, 1947 ELECTRON DISCHARGE DEVICE Douglas A. S. Hale, Ramsey, N. 5., and Victor L.

Ronci, New York, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application May 29, 1944, Serial No. 537,858

This invention relates to electron discharge devices and more particularly to indirectly heated cathode structures for such devices.

One object of this invention is to improve the construction of indirectly heated cathodes and, more specifically, to increase the insulation resistance between the heater and emissive elements in equipotential type cathodes Without deleteriously affecting the thermal efiiciency thereof, and to facilitate the fabrication of such cathodes and the mounting thereof in electron discharge devices.

Another object of this invention is to realize electrical symmetry of the cathode with respect to an associated electrode in electron discharge devices, such as of the magnetron type, operable at ultra high frequencies. I

In one illustrative embodiment of this invention, a cathode especially suitable for utilization in a multianode magnetron operable in the centimeter range comprises a cylindrical cathode sleeve or shell having an electron emissive coating on its'outer surface, and a helical heater filament within the cathode sleeve. 7

In accordance with one feature of this invention, the heater filament is supported in proximity to but spaced from the inner surface of the cathode sleeve, upon a plurality of insulating posts extending between a metallic closure at one end of the sleeve and an insulating disc at the other filament and the cathode sleeve.

" In accordance with another feature of this mvention, the metallic closure and the insulating the leading-in conductors aforementioned, and

the cathode sleeve has one end fixed to'the'metallic closure and its other end slidable uponthe insulating disc so that the sleeve can expand and contract freely longitudinally in accordance with I temperature variations. When utilized in a device, such as a centimeter range magnetron, wherein symmetry of the electrodes is highly important, the cathode sleeve is mounted so that normally, that is when it i unheated, it is un- Claims. (01.250415) disc are mounted in fixed space relation, as by .45

2 symmetrical by a predetermined extent withrespect to the transverse median plane of the electrode system. When the cathode is heated to the intended operating temperature, it expands longitudinally so that it becomes symmetrical with respect to the plane noted whereby electric and electronic symmetry of the cathode with respect to the cooperating electrode, for example the anode, during operation of the device is realized. The invention and the above noted and other features thereof will beunderstood more clearly and fully from the following detailed description with reference to the accompanying drawing in which: Fig. 1 is an elevational view in perspective of an electron discharge device and a protective element for parts thereof, illustrative of one embodiment of this invention, portions of the output structure being broken away' to show detailsflof construction;

Fig. 2 is a front View mainly in section of the device illustrated in Fig. 1; Fig. 3'is a side view, partly in section and partly broken away, of the device; Fig. 4 is a detail view to an enlarged scale of the cathode assembly included in the device illustrated in Figs. 1 to 3, a portion of the cathode sleeve being broken away and parts being shown in section to illustrate details of construction: and 7 Figs. 5 and 6 are end views, as seen from planes 5-5 and 6-45 respectively of Fig. 4, of the oathode structure.

Referring now to the drawing, the electron discharge device illustrated is a magnetron oscil-,- lator of the multianode type especially suitable for operation in the centimeter range and comprises a generally cylindrical metallic body or block l0, advantageously of copper, and closure discs ll sealed heremetically to the ends of the body or block NJ as by soldering. Extending from the body or block In and diametrically aligned are an output structure designated generally as l2 and an input conductor. structure designated generally as It. As shown clearly in Figs. 2 and 3, the'body or blocklll includes an internalcylindrical' portion of somewhat'shorter length then the body or block, which portion is provided with a plurality of substantially identical, cylindrical resonating cavities l5 having their longitudinal axes parallel and equally spaced. The cylindrical portion M,

as will be apparent. from'liig'z, defines a multianode element, the several anodes or anode segments having arcuate inner faces [6 which are arranged in a circular. cylindrical boundary. At

' another.

- to this plane.

opposite ends of the anode portion l4 and associated with the anode segments are arcuate conductors I! which, as described fully in the applications Serial No. 529,619, filed April 5, 1944, of James B. Fisk and Serial No. 517,669, filed January 10, 1944, of Victor L. Ronci, serve to assure oscillation of the device in a desired mode.

The output end structure I 2 comprises a metallic platform I8, for example of copper, afiixed to the body or block I as by brazing material indicated at I3. Hermetically joined to the platform I 8 is a cylindrical metal sleeve to which a vitreous stem 2| is sealed. The stem 2! has sealed thereto a conductor 22 which is connected at one end to a coupling or pickup loop 23. The loop is positioned in one of the cavities l5, advantageously midway between the ends thereof as shown in Fig. 3, and has one end fixed to the platform l8. The conductor 22 mounts a connector element having coaxial inner and outer metallic members 24 and 25 respectively and the sleeve 20 has afiixed thereto a cylindrical metallic member 26. In operation of the. magnetron, the connector element 24, 25 and the cylindrical member 26 are fitted to the inner and outer conductors respectively of a coaxial transmission :line.

The platform I8 and sleeve 26 may be encompassed by a protective metallic cylinder 21 which extends from a bracket '28 afiixed to the body in and fitted over the platform. Advantageously, the bracket 28 is provided with a rigid finger 23 which is adapted to engage a spring, not shown, on a mounting for the device and lock the device against accidental displacement.

*Extending from the body or block H! at points opposite the output end structure I2 are a pair of leading-in conductor assemblies for the cathode. Each of these assemblies comprises a rigid conductor 30 sealed to a vitreous stem 3! which in turn is sealed hermetically to a metallic sleeve 32. The sleeves 32, as shown in Fig. 3 may be threaded into the body or block [0 and brazed thereto, as indicated at 33, to form a hermetic seal therewith. The leading-in conductors 30 mount rigid metallic supports or rods "34a and 34b which are affixed to the conductors 30 as by sleeves or couplers 35 welded to the respective conductors and supports.

The supports or rods 34 mount a cathode, which, as shown in Figs. 2 and 3, is positioned coaxially within the anode member l4 and, as shown most clearly in Fig. 4, comprises a cylindrical metallic sleeve 36 having thereon a coating 31 of electron emissive material. One end of the sleeve 36 has fixed therein a metallic closure member or cap 38 and the other end of the sleeve is fitted 'slidably upon an insulating disc 39. for example of a ceramic. The closure or cap 33 is fixed, as by welding, to the support or rod 34a, one end of which, asshown at 40 in Fig. 5, may be flattened to providea large area of contact with the closure or cap 38. The outer face of the disc '39 is provided with a diametral channel or. groove 4|. ll-shaped in section, in which the support .or rod 34b is locked by a wire 42. It will be appreciated, then, that the closure or cap 38 and the disc 3.9 are mounted in fixed relation to one The sleeve 35, being secured to the closure or cap, is fixed at one end while the other .endis'slidable upon the disc 39. In the assembly of the device. the sleeve is'positioned in such-relation to the 'transverse'median plane of the anode portion l '4 that it is unsymmetrical with respect When the device is operated,

- 4 the cathode sleeve 36 expands and slides on'the disc 39 so that it becomes symmetrical with respect to the plane noted.

Inasmuch as the cathode sleeve is free to expand longitudinally, it will be appreciated that distortion or buckling of the sleeve is prevented. Thus, as will be apparent, when the device is operated the cathode sleeve remains in accurate coaxial relation with the anode faces I6 and,

furthermore, is symmetrical longitudinally with respect to these faces. Thus, exact mechanical and electrical symmetry of the anode and cathode during operation of the device is realized.

The cathode sleeve 36 has afiixed to opposite ends thereof a pair of dished metallic shields 43 which serve to prevent flow of electrons from the emissivesurface 31 to beyond the ends of the anode faces IE 01', viewed in another way, to confine the electrons to the region between the cathode and the anode surfaces It.

The cathode sleeve 36 is heated during operation of the device by a heater element which comprises a helical filament 44 coated with insulating, e. g., ceramic, material and mounted upon a plurality, for example three, of tubular insulating, e. g., ceramic, posts or supports 45. The posts or supports 45 are threaded upon wires 46 which are afiixed at one end, as by welding, to tabs 41 on the closure or cap 38 and are locked at the other end to the insulating disc 39 by wire strips 48 welded to the posts at this end. As shown in Fig. 4, the insulating supports 45 are fitted at one end in apertures in the insulating disc 39.

One end of the heater filament 44 is connected, as by welding, to the support or rod 341); the other end of the filament is affixed, as by welding, to a tab 43 integral with the cap 38 and, thus, is connected electrically to the cathode sleeve 36 and to the support orrod 34a.

It will be noted that the heater element is mounted in proximity to but spaced from the cathodesleeve 35. The support of the heater filament by the ceramic posts 45 assures good insulation of the body of the heater filament from the cathode sleeve and enables the attainment of such good insulation without deleteriously affecting heat transfer from the heater filament to the cathode. Thus, the cathode structure is both thermally efilcient and electrically advantageous.

Furthermore, the construction described lends itself to facile fabrication as a unitary assembly which can be mounted readily within the body or block It].

In the fabrication of the cathode assembly, the shields 43 and closure or cap 33 are afiixed to the .cathode sleeve 35 and the support or rod 34a is then is welded to-the tab 49. The insulating disc .39 is fitted onto the posts 45 and the flange thereon is held'in spacedrelation to the adjacent end of the cathode sleeve by a suitable spacer or gauge, after which the other end of the heater filament and the wire 42 are afiixed to the support or post 34b. The wire strips 48 are then welded to the respective wires 46 to lock the insulator 39 in position.

The unitary assembly thus formed isinserted into the body or block 10 and the supports or rods 34 are affixed to the leading-in conductors 30, with the cathode positioned in coaxial relation with the anode surfaces lit by a suitable u e. Subsequently, the closures I! are affixed to the body or block [0.

The interior of the device is highly evacuated as by way of an exhaust connection including a metallic sleeve 50 hermetically joined to the body or block ii], as by brazing material indicated at and a vitreous closure 52 sealed hermetically to the sleeve 50.

The leading-in conductor assemblies and the exhaust connection may be protected against damage during the handlin or use of the de vice by a metallic guard member 53 afiixed to the body l0 and a substantial vitreous cap as secured to the guard member 53 and having therein terminals 55 to which the conductors 30 are connected.

Although a specific embodiment of this inven tion has been shown and described, it will be understood that it is but illustrative and that various modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

1. A cathode structure comprising a pair of supports mounted in fixed spaced relation, a pair of disc members each fixed to a respective support, a cylindrical cathode member having one end fixed to one of said disc members and its other end slidably fitted upon the other of said disc members, and a heater element within said cathode member.

2. A cathode structure comprising a hollow, elongated cathode member, a pair of closure members at opposite ends of said cathode member, insulating posts extending between and supported by said closure members, and a helical heater filament supported upon said posts in proximity to the inner surface of said cathode member.

3. A cathode structure comprising a cylindrical cathode member, a metallic closure at one end of said cathode member, an insulating closure at the other end of aid cathode member, a plurality of insulating posts extending between and supported by said closure members, a helical heater filament within said cathode member and supported upon said posts, said cathode member allel wires extending between said closures, each.

of said wires having one end fixed to one of said tabs and its other end portion extending through one of said apertures, means locking said wires in position with respect to said insulating closure, tubular ceramic sleeves threaded on said wires, and a helical heater filament mounted on said sleeves and having one end connected to said metallic closure and its other end extending through said insulating closure.

5. A cathode structure comprising an insulating disc, a metallic disc, a pair of leading-in conductors mounting said discs in fixed, aligned, parallel relation, insulating posts extending between said discs and supported thereby, a heater filament encircling said posts and supported thereon, said filament having its ends connected to said conductors, and a cylindrical cathode sleeve encompassing said filament, one end of said sleeve being fitted upon said metallic disc and affixed thereto and the other end of said sleeve being slidably fitted on said insulating disc.

DOUGLAS A. s. HALE. VICTOR L. RONCI.

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

UNITED STATES PATENTS Pike Aug. 29, 1933

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