US2496887A

US2496887A - High-frequency electrical apparatus

Info

Publication number: US2496887A
Application number: US601123A
Authority: US
Inventors: Richard B Nelson
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1945-06-23
Filing date: 1945-06-23
Publication date: 1950-02-07
Anticipated expiration: 1967-02-07

Description

Feb. 7, 1950 R. B. NELSON 2,496,887

HIGH-FREQUENCY ELECTRICAL APPARATUS Filed June 25, 1945 vll/l//l//ll/l/l/ Figbdl.

Inventor: Richard B. Ne\sor1,

y ap-,Z5 AttOTT-ley.

Patented Fel. 7, 1950 HGH-FREQUENCY ELECTRICAL APPARATUS Richard B. Nelson, Schenectady, N, Yr, assigner to General Electric Company, a corporation of` New York Application J une 23, 1945, Serial No. 601,123

(Cl. 25d-27.5) l

16 Claims.

My invention relates to high frequency electrical apparatus and more particularly to improved space resonant structures and tuning mechanisms therefor. While not limited thereto, my invention is particularly adapted for tunable magnetron anode structures.

A variety of tunable magnetron constructions have been proposed in which one or more tuning elements are moved with respect to the space resonant anode structure to vary the effective inductance and capacitance of the Various circuits of the anode structure. An arrangement for varying both the inductive and capacitive components of the resonant circuit including a pair of tuning disks arranged on opposite sides of the resonant anode structure is described and claimed in my application Serial No. 566,288, led December 2, 1944, now Patent No. 2,424,496, dated July 22, 1947, and assigned to the assignee of the present invention. In arrangements of this type the somewhat complicated tuning structure introduces a number of additional resonant circuits which are a source of considerable power loss. This structure is also diflicult to cool eiciently so that the power output of the device is limited. In accordance with the present invention, an improved resonant structure is provided which is shaped so that both the inductive and capacitive reactance components may be controlled by a single tuning member.

It is an object of my invention to provide a new and improved space resonant str-ucture.

,It is another object of my invention to provide a new and improved tunable space resonant structure.

It is still another object of my invention to provide a new and improved tunable magnetron construction.

In accordance with the illustrated embodiment of my invention, I provide an improved magnetron construction in which the space resonant anode may be considered as a modification of the radial vane type in which each of the Vanes is partially cut away so that the cross section of the vane in a radial plane is essentially J-shaped. The longer arm of each of the J-shaped vanes is secured to the wall of the enclosing envelope and the shorter arm extends a portion of the distance from the end of the vane towards the wall of the envelope. A substantially planar tuning member is received between the arms of the anode sections and is axially movable with respect to the structure by an improved supporting structure including essentially an end wall of the envelope. This wall is sealed to the ductor.

side Wall of the envelope by a flexible bellows and is moved with respect thereto by an adjusting collar which is threaded to an extension of the envelope. The collar is rotatably carried by a hub extending from the movable end wall of the envelope. In the particular embodiment illustrated, the vanes are formed of copper tubing which is bent into the desired form and mounted on the envelope wall with the ends thereof communicating with a header formed on the exterior of thetube wall and providing passages for cooling uid. Certain features of this tubular anode vconstruction are described and claimed in my application Serial No. 601,122 led concurrently herewith and assigned to the assignee of the present invention.

For a better. understanding of my invention, reference vmay be Vhad to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. In the drawing, Fig. 1 is an elevational view, in section, of a magnetron device embodying my invention, Fig. 2 is a sectional View taken along the line 2 2 of Fig. l, and Fig. 3 is a sectional view takenvalong the line 3-3 of Fig. 1.

Referring now to the drawing, the magnetron device embodying my invention includes a gen erally cylindrical envelope I formed of copper or other good conducting material. Although the discharge device is illustrated in the drawing with the axis of the envelope horizontal, it is preferable that the device be mounted with the axis vertical and in the folowing descriptionV the parts are referred to as if the tuning mechanism were at the upper end of the device. The envelope is closed at its lower end by a wall 2 preferably formed of fernico or sheet steel and having a marginal flange 3 which is adapted to be welded or otherwise bonded to a fernico or sheet steelextension 4 formed on the lower end of the cylindrical member Il. The end wall 2 is provided with a centrally located aperture surrounded by a depending circular ange 5 to which a cathode mount 6 is sealed by means of a cylindrical insulator 'I. The cathode mount 6 includes a circular header 8 to which is bonded a fernico sleeve 9. The other end of the sleeve 9 is sealed to the lower end of the insulating cylinder 1. The cathode proper includes a pair of helical wires I0 and I I which are wound in bilar relation and joined at their upper ends to the upper end of a conductor I2 which provides a support and direct current cathode supply con- The conductor I2 is received in an opening formed in the center of a ferromagnetic member I3 having a generally d-umbbell shape cross section, as shown in Fig. 3, and which is supported at its lower end by the header 8. End shields I4 and I5 are also supported from the conductor I2. The free ends of the cathode elements ID' and II" are joined to-molybdenum inserts I6 andI'I received;respectively, inthe ends of steel rods I8 and I9 which are received in the openings provided by the restricted portion of the dumbbell shaped member I3. Theserods are provided at the lower ends with fer'riico' sleeves and 2l, respectively, which are sealed by

glass beads

22 and 23 to fernico sleeves'ZIl and 25of larger diameter which are, inlturn, brazed to the header 8. The current supply connections with the steel rods I8 and IS are provided by conductors 26 and 2'I which pass through the sleeves 20 and 2I in spaced relation with respect thereto and are received in recesses formed in the lower ends off'the steelrods.' With'tliis oonstr'uction'tle current supply circuits include the'ferro'mag-netic members I3, I8and I3' which provide-"a portion of` the magnetic circuit-for providing'` a' magnetic field in the interelectrode'- space. This: magnetic circuit also includes av cylindrical member 28 surrounding the members I3,' I8 and I9 and projecting into the" interior ofthe discharge device and an annular disk' 23 which is bra'zed/to the exterior of the' end wall- 2'. Apolefa'oef30 of theA magnet or electromagnet may be shaped to'v conform generally'with' the shape'ofthe disk 29 and to advantage may be slottedlat one'side to facili'- tate slipping it'- in plaoef around the supporting' flange 5 and the insulator 'I. The Vconstruction just described provides a very effective wayof' supporting and supplying; current to the cathode while at the Sametime'providingvr a magnetic circuit for distributing'the flux-in the desired-'relation with respect to thecathode;

The anode structure ofthe devicf'includesa plurality of space resonant circuits defined' by anode sections, each of which is?A of" generally JV-shaped *crossy section;

length of tubular conductor, such as'cppertubwhich is foldedl bacl;i on' itself tof provide radially extending# armv portions -32 and' 331 which? are received inopeningsiformed-mltlie wall ofY the' envelope I. TliLV tubingi isY shaped tov define' axially extending portions 34j andl 35 joined'- toY the outer ends'of thef'a'rm portions 3,2-'adl33a'tl one end and joined' to'a-'looppqrti'o'n 36p? at' the' other end.- Aigener'ally' trapezoidalishaped-member 3l is'brazed to thelowe` edgeoffea`ch"loo'pe'dl conductor 35 and together4 therewith-form the` short arm of the .I-shapedY anode'seotion The extended armof the member-'31 cooperating' with atuning member 42" provides"Y for an eieetive` variation of the capacitance of'ftlie various space'-v resonant circuitsv withthe positionof the tuning' member. The ends of' the armportions 32 and-33 received in the wall of theV envelope? I com'- municate, respectively, with 1".\as'sag'es'v 38 and-39 formed in a circular header39" which' surrounds the-envelope.v Thisheader may beforrned'in any' suitable way and in thfef illustrated embodiment is a copper ring which has1 been?machined to provide the pass'ages38 and-*.39 and!their-bra'zed'v to the exterior oftheenvelope". `F'Iu'idsupply connections and 4'I`V com'n'iunicateg` respectively; with

passages

38 and 39. In prior' constructions' it is common'practice to' connect cond'ucA'ti'vfely` all of the even numbered' sections at" their-inner# ends to provide one group of strapped sections' and A'skillustr'at'edfinv the? drawing; each anode section 3'I 'is-formed' from ato connect all of the odd numbered sections together to provide a second group. In the arrangement illustrated these straps are provided by conducting rods which join alternate sections and pass through the opening provided by the looped portion 36 of the intermediate anode section. This arrangement is' claimed' and more f'ullyy described in my above referred toc'opending application Serial No. 601,122.

rlhe shape of the anode sections described above makes possible a novel arrangement of the tuning member and its associated mechanism which forms an important aspect of my invention. Referring now to the drawing, a tuning member inthe form of an annular disk 42 is received between the loop portion 3B of the anode members 3l and the radial arm portions including tubular conductors 32 and 33. This disk is arranged in parallel relation to and between the opposed surfaces provided by the radial arm portions 32 of the anode sections andthe members' 3lv which are' secured to the loop portions oi" the anode sections. The tuning member 4211s supported from a disk 43, preferably formed of copper, which may be considered an' end wall of' the tubular envelope I', by means of a continuous cylindrical conductor 44'. Withrths tuning structure, which'is'essentially a hollow cylinder with' one'end apertured to'receive the axially extendingportions of the anode sections, the' number of resonant frequencies introduced is a minimum andthe power loss in the tuning mechanism is very small. The cylinder 44" and end wall 43' are slightly smaller in diameter than the cylinder 45' which extends substantially beyond the end wall G3 and is in effect a continuation of thev 46 which hermetically seals the tub'e envelopeV and permits the desired relative' movement between tlie anode structure'and' the tuning structure including the tuning disk 42. prevent substantial leakage of electromagnetic' flux past' the tuning member 472'and'the supporting cylinder 44 a cylindrical extension 4'I`is'providedonthe inner wall of the envelope with the upper edge thereof ush with the'upper edge of the radial arm portions' of the anode sections.' This extension may bel formed integrally with the tube envelope I if desired. l

Movement' of the tuning structure is effected by a threaded bushing' 48' which is secured to the outer race 49 of a ball bearing 5D. The threaded portion of the bushing is received in an adaptor 5I which rests on a shoulder formed on the Lipper end of the extension d5' of the envelope of the device. The inner race 52 of the bearing is clamped in fixed relation" with respect to a hub 53? whichv is bonded tothe upper side of the end wallv 43. The' clamping' is eiected by a disk-like melnber'n which issecured tof the upper end'of the hub to clamp the'in'ner race 52 of the bearing against a shoulder' formed on the hub 53; As? illustrated in the drawing, the hub is provided with axially extending passages which are joined at their lower ends'by a groove for the reception of a U-sh'a'p'ed tube 51 which is" placed in position in the hu'b'befo're' it is bonded to theend wall 43i The tube 5'I forms a passage for circulating cooling fluid through the tuning structure to' extract heat therefrom generated by high frequency currents low reluctancepath' for the axial magnetic flux- In order to' are omitted during the exhaust and 'for this' reason the central opening 59 in the hub 53 is threaded to permit it to be retained in position with respect to the tube envelope byv a suitable jig (not shown).

l, High frequency electrical energy may be extracted from the device by a Vsuitable output circuit coupled with the space resonant structure. In the illustrated embodiment this output is of thel concentric type and includes an inner conductor 6D having a looped portion 6l bolted or otherwise secured to one of the anode sections as shown at 62. The outer conductor 63 of the output line is joined to the tube envelope and terminates in a radially extending flange '64. A cylindrical sleeve 65 is joined at one end to the flange 64 and sealed at the other end to a body of glass 66 which is, in turn, sealed to a conductor 61 which forms an extension of conductor 60. The conductor 61, as illustrated, is larger than the conductor 60 and is hollow to receive a iuid supply conduit 68. The collar 65 is electrically connected with an outer conductor -69 of the `output transmission line by an adaptor 10. As illustrated, the outer end of the conduit 61 is slotted in the region beyond the glass seal 66 to provide passages 1l for the cooling fluid introduced by the conduit 68. This fluid is allowed to escape through similar passages 1l formed at the end of conductor 69 adjacent the adaptor 10. Air or other cooling fluid is introduced to the conduit 68 through a fitting 12, a section ofinsulating conduit 13 and a passage 14 formed in a conductor 15 which forms an extension of conductor 61 and provides the central conductor of the output transmission line.

Evacuation of the envelope is accomplished through an opening 16 formed in the wall of the device and surrounded by an outwardly extending sleeve 11 which is closed by a header 18 and an exhaust tube 19. The header 18 also provides a support for a getter 80 having one end connected with the header through a conductor 8| and the other end sealed to the header by means of a conductor 82 sealed to a collar 83 by a body of glass 84. The conductor 8l also provides a support for a shield 85 which prevents the getter material from depositing on the interior of the envelope.

Although the features and advantages which characterize my invention are believed to be readily understood from the foregoing detailed description of the illustrated embodiment, a brief description of the operation of the device may further emphasize them. As is well understood, electrons emitted by the cathode elements I and I I move in the interelectrode space under the resultant action of an electric field produced by voltage applied between the anode and cathode and an axial magnetic eld produced in the interelectrode space by pole pieces 3D and 58. The resultant motion of these electrons is effective to excite the anode structure into os-cillation at a high frequency dependent in part upon the geometry of the anode and in part by the position of the tuning structure including the tuning di'sll:` 42. With the disk in the intermediate position shown, the magnetron will operate at an intermediate' frequency. As the tuning member is moved downwardly toward'the radial arm portions of the anode members, the electromagnetic flux linking the various circuits dened by the anode sections is gradually cutoff, thereby decreasing the inductance of the anode members. At the same time the distance between the disk 42 Vand Athe members 31 which form extensions of theoverhanging portions of the anode sections is increased, thereby decreasing the capacitance between the anodes and the disk 42', which latter has very little high-frequency voltage. Since the resonant'frequency of the anode structure is determined by the product of the inductance and capacitance'ofl the resonant elements, a downward motion of disk 42, by decreasing both inductance and capacitance, causes a large increase in the operating frequency. Conversely, as the disk is moved upwardly the capacitance is increased and the inductance is increased, with the result that the operating frequency is decreased.

Magnetron devices embodying the present invention may be tuned over a wide range and op` erated at high power. The tuning range is large partially because of the relatively smaller distributed -capacity of the J-shaped anode sections as compared with the conventional vane type sections and because of the effectiveness of the single tuning disk as a tuning element for both the inductive and capacitive reactance components. The tuning structure is essentially a hollow cylinder yhaving continuous walls except for the apertured end which receives a portion of the resonant anode, and for this reason has very few resonant frequencies associated with. it whichl tend to absorb power and lower the tube elfi-` ciency as well as to generate unwanted heat. The tuning structure is also well suited for cooling because of the relatively large heat conducting paths which are connected with the tube en velope and which may be fluid cooled, as illus trated in the drawing. The incorporation in the magnetic circuit of a part of the support for the tuning structure and of a portion of the supportv and lead-in for the cathode also improves the distribution of the flux in the interelectrode space. It is believed apparentlthat the combination of these features produces a high frequency device of high eciency-,relatively large power output, and wide tuning range.

While I have shown and described a particular embodiment of my invention. it will be obvious to those skilled in the art that changes and modicationsQmay-'be made without departing from my invention-Ain its broader aspects. and I. therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What l claim as new and desire to secure by Letters Patentof the United States is:

- 1. A high frequency device comprising a sub stantially planar tuning member, a space reso-l nant structure including a plurality of sections mounted in spaced relation to denne a plurality of coupled space resonant circuits, each of said sections having a substantially J-shaped cross section vin a plane perpendicular tosaid tuning memberwith the arms of said J extending subn stantially parallel to and on opposite sides of said tuning member, and means connected with said tuning member for moving said tuning to each other and with respect to the rst mentioned ferromagnetic member.

14. An electric discharge device of the magnetron type including an envelope, a tuning member, a space resonant anode structure mounted in said envelope and including a plurality of anode sections, the walls of said anode sections dening coupled. space resonant circuits having physically displaced portions contributing respectively the predominately capacitive and predominately inductive components of the resonant circuits, said portions being positioned oppositely with respect to said tuning member so that said member may be moved toward one of said portions of each of said anode sections as it moves away from the other of said portions, and means for moving said member.

15. A tunable magnetron device comprising a resonant electrode structure including a generally cylindrical array of radially extending circumferentially spaced anode sections defining a plurality of coupled space resonant circuits, said anode structure including a circumferentially extending recess, an annular tuning member positioned in said recess and means joined to said tuning member and extending generally in an axial direction with respect to said anode for moving said tuning member axially with respect to said anode so that said tuning member moves away from one surface of said recess as it moves toward the opposed surface of said recess.

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

UNITED STATES PATENTS Name Date Dallenbach July 25, 1939 Dow July 16, 1946 Spencer Sept. 24, 1946 Hagstrum Apr. 8, 1947 De Walt July 29, 1947 FOREIGN PATENTS Country Date Switzerland May 1, 1940 Switzerland 1 Oct. 1, 1941 Number Number Disclaimer 2,496,887.Rz`chard B. Nelson, Schenectady, N. Y. HIGH-FREQUENCY ELECTRICAL APPARATUS. Patent dated Feb. 7, 1950. Disclaimer filed Aug. l0, 1950, by the assignee, General Electric Company. Hereby enters this disclaimer of claims 9, l0, and l1 of Said patent.

[Ocz'al Gazette September 1.9, 1950.]