US2520955A - Trapezoidal cavity magnetron - Google Patents

Description

E. C. OKRESS EI'AL TRAPEZOIDAL CAVITY MAGNETRON Filed Oct. 15, 1942 INVENTORS z ATTORNEY Sept. 5, 1950 Patented Sept. 5, 1950 2,529,9 5 TRAPEZOlDAL CAVITY Ernest C. O kress and Ilia E. Mouromtseff, Montclair, N. J., assignors to Westinghouse Elec ic Corporation, East Pittsburgh, 2a.; a corpgration of Pennsylvania Application October 15, 19.42, Serial No. 462, 13.?

4. Claims. (01. 250,27 .5)

This invention relates ;to generators of high frequency electricity, -and particularly those of the type called magnetrons.

The principal objectrof our invention, generally considered, is an improved nagnetron for energy in the regionof centimeter wavelengths and amethod of manufacture.

Another object of our invention is the manufactureo'f .magnetrons by a method which avoids the necessity of very accurate machining.

.A further object of our invention is to simplify and cheapen the construction of magnetrons.

A still further object of our invention is to increase the permissive tolerances in the manufacture of magnetrons.

Other objects and advantages of the invention, relating to the particular arrangement and construction of the various parts, will become apparent as therdescription proceeds.

Referring to the drawings Fig. 1 is a sectional View onthe line I-I of Fig. 2, in the direction of the arrows, with parts in evelation, of a magnetron embodying our invention.

Fig. 2 is a perspective view on the line -II--II of Fig. 1, in the direction of the arrows, with parts in elevation.

Fig. 3 is a sectional perspective View of a blank which is desirably used in manufacturing the body member of the magnetron.

Fig. 4 is a perspective View of oneof the partition elements of a magnetron embodying our inyention.

Fig. :5 is a fragmentary view corresponding to Fig. l but showing a modification.

As pointedout in the Okress application, Serial No. 460,376, filed October 1, 19.42, and owned by the assignee of the present application, resonant cavity magnetrons, such as those in the 10 centimeter range, have previously been constructed as there illustrated in Fig..12, that is, with generally cylindrical cavities disposed about ,a central pocket adapted to receive the cathode andcommunicating therewith.

In said application it is shown how accurate machining may be avoided by a modified construction in which slots took the place of the generally cylindrical cavities, three forms being theredisclosed; first, in which-the slots were, of generally uniform Width and separated by partitions generally trapezoidal or sector shaped in section on a plane perpendicular to the axis; second, in which said slots were generally trapeaoida l or sector and separated by generally trapezoidal or sector shaped partitions; and

ma ne n H cqn ins a housing d 01' third, in which said slots are generally trapezoidal or sector shaped and separated by relatively thin partitions or suchgenerally rectangular in section. it is also shown that such ;'i I nproved constructions resulted, not only 'in avoidns accurate maichining but also n substantially reducing ;thewavelength sensitivity.

In accordance with the present invention we havedevised an improvedconstruction of magnetrqns with generally trapezoidal or sector ap d a itie as w l aw mpmv methed 9 manufacture.

' Reierr-ing to the drawings in detail, and first considering the embodiment of our invention anode portion t; of oxygen-free, high-conductivity copper having relatively thin, that is, considerablythinner than the radial thickness of said .body 2, plates or vanes l fi, t, :5, 1s, :1, s, is. and 2i refe b f rm e en u s eepe alloy (described by smith in I. and

. 'I fech. Pub. N 0.3.7.0) which platesdefine generally triangular, trapezoidal or sector shaped pockets 23%, 24, 25, 26,171, .28, 29 and BlitherebetWeen, all

of saidpoclgets communicating with a central chamber or pocket 32 where an oxide coated n cke ase cathe .33 i p tioned.

oax a t rm na o Out e d '34 i th p s embod ment ssh wn t one by having its inner end portion curved or looped back on itself and connected to the inner peripheral portion of the housingmember, as indicated at .55. ilnthe present instance the terminalmember .34 has i a e fi itap fill =pQ 1liQ i0m l9 tungsten and its small or inner portion formed of electrolytic copper, and is enclosed in a tuh lar o a nstfiiha ins a a l flan e 3! threaded as indicated at 38 for a coaxial capacitive cable coupling, which may correspond with the threaded portion 25. of the Rigrodet al. inte t, ,lio zg osml, dated Sept. 24, 1946. This ea in ...d r b thread n c ed r t cylindr c Iwrti. v l a nd e '38- .Th t mi a is de ir en w t respeet th es nsi a by e n of a min #lp l or soft'borosilieate glass bead 4! between t sam an a, c li drica .q n u m mbe A wh ch m y befo' n v of .K va (w ic s-a alloy containing 28.7 to 29.2% nickel, 17.3 to 1 -53% Qba 2i9 t .14% ir no mor tha .06% carbon, not more than .5% manganese, and not more than .2% silicon) or other suitable ma- ,terial. The inner end of this conductor member is desirably connected by eutectic gQld-copper 3 solder to a steel ring 43 and the combination secured to the flange portion 37 by BT solder, as shown most clearly in Fig. 1. 31" solder melts at about 779 C. and is 72% silver and 28% copper.

The cathode 33 in the present embodiment is shownas consisting of a helicaltungsten filament 44 enclosed in an electron-emitting housing 45 composed of a mixture of oxides of strontium, barium and calcium on a nickel sleeve and supplied with power from a suitable source by tungsten leads 45 and 47.. These leads project through copper casings 48 and 49, held in place as described in connectionwith the Okress application, Serial No. 460,376, previously referred to, which also shows how the power may be supplied to the cathode including the use of filters.

Figs. 3 and 4 show the blanks which are desir ably employed to make the magnetron body during the process of manufacture. After the design, we desirably start with a plurality of plates 5i, desirably of uniform thickness and numerically corresponding with the pockets, in this instance eight. These plates are desirably formed of selenium copper alloy or other similar metal, and are relatively thin although sufficiently heavy to provide a rugged construction.

We then take a shell portion 52 which is generally cylindrical on its exterior, but relatively thinned toward its ends as indicated at 53 and 54,

to leave an inwardly extending annular boss 55. This boss is, in turn, slotted or grooved longitudinally or parallel to the axis, as indicated at 56 to a width so as to snugly receive the plates 5! and leave inwardly extending sections 57, nu

merically corresponding with the number of pockets desired in the finished magnetron, in this instance eight. The plates 51 are then fitted in the slots 55, as by means of a jig, and soldered in place as indicated at 58. This soldering is desirably effected with the use of BT solder or upper and lower copper cover members 59 and BI to the body, as shown in Fig. 2, with RT solder applied at the joints. RT solder melts at about 682 C. and is 60% silver, 25% copper, and

15% zinc. The whole assembly may be exposed in a hydrogen furnace and brought to the melting temperature of the solder, that is not high enough to melt the interior BT soldered connec-= tions, in order to effect such a union.

Referring now to the embodiment of our in- I vention illustrated in Fig. 5, there is shown a magnetron Ii consistingof a body or anode portion 2 which, like the magnetron II, is desirably formed of copper and has selenium copper alloy partitions, like the partitions of the preceding embodiment, only those numbered 15 Hi Il and I8 being shown, projecting inwardly from the peripheral portion 22 and separated by pockets like those of the preceding embodiment,

only those pockets numbered 25 26 2'! and 28 being shown. 'All of these pockets communicate with a central chamber 32 where a cathode may be positioned as in the first embodiment.

In the present embodiment, the housing or anode member !2 is formed by taking a plain hollow cylinder and connecting radially projecting partition wall members in place by means of BT solder, indicated at 58*, said plates being desirably held with their outeredges, as by means of a jig, in abutting engagement with the inner surface of the cylindrical outer member 22 while in a hydrogen furnace where the soldering is effected, as in the preceding embodiment.

In the present embodiment we have shown an alternative terminal 34 which, like the terminal 35 of the Okress application, Serial No. 460,376, previously referred to, has large and tapering portions desirably formed of tungsten and a small or inner portion formed of electrolytic copper;

and enclosed in a tubular copper casing 36 corresponding with the casing 36 of the preceding embodiment, and centered with respect thereto in a similar manner.

In the present embodiment, however, the inner portion of the terminal 37 5*, instead of being bent back on itself and connected to the outer cylindrical portion of the housing, extends to one of the partition plates, such as that designated Hi passing into a recess 35 thereof, and secured thereto in any desired manner, as by means of BT solder. It will be noted that such. a coupling may be used in the preceding embodiment, or that of the preceding embodiment used in this embodiment, interchangeably, within the spirit and scope of our invention.

In both embodiments of our invention the portions l3, Id, etc. or l5 I6 etc. projecting inwardly from the peripheral portion 22 or 22 are all generally thin and of uniform thickness, like the slots 23 to 29, inclusive and 3! of the first embodiment of the Okress application, Serial No. 460,37 6, previously referred to, that is, the slots or pockets therebetween aregenerally triangular, trapezoidal, or sector shaped in section. In all the embodiments, however, the inner circumferential width of each pocket is uniform and may correspond with the uniform circumferential width of the separating partitions, notwithstanding the variation in outer circumferential width of these parts, although this correspondence is not essential.

Magnetrons with sector shaped pockets, like those of the present invention, are of lighter weight and have greater efficiency and power capacity than those with slotted pockets, relatively narrow, as illustrated in Fig. 1 of said Okress application, Serial No. 460,376, previously referred to. This is because the impedance of the generally triangular, trapezoidal or sector shaped slot or pocket at the slot aperture is much higher than that of the slot of uniform width, and hence such a pocket shape results in a much better match for the electronic field impedance than in the case of a magnetron with thin slots of uniform width. The wavelength sensitivity for pockets of the present embodiment, with regard to their structural parameters, is between that of the rectangular or thin slot and the conventional cylindrical cavity structure previously referred to.

From the foregoing, it will be seen that we have provided an improved magnetron and method of manufacture which avoids the necessity of accurate machining, simplifies and cheapens the construction, increases the permissive tolerances, and economizes in the use of material.

Although preferred embodiments of our invention have been disclosed, it will he understood that modifications may be made within the spirit and scope of the appended claims.

We claim:

1. A magnetron housing formed as an outer generally cylindrical hollow conductive portion having longitudinal grooves from which flat sided partitions project inwardly defining a central cathode cavity communicating with chambers generally sector shaped in section on a plane perpendicular to the axis and disposed thereabout, a cathode assembly disposed in said cavity, leads from said cathode assembly projecting through said hollow cylindrical portion to outside of said housing, an output lead extending into said housing in a generally radial direction, curved backward and united to the inner surface of said housing, and a conductor casing in contact with and projecting from said housing and disposed coaxial with respect to said lead.

2. A magnetron housing comprising a hollow cylindrical portion of oxygen-free high-conductivity copper from which parallel-sided walls of selenium copper alloy project inward in generally radial directions defining a central cavity communicating with pockets disposed therearound, the outer edge portions of said walls fitting in grooves in said cylindrical portion and secured in place by solder.

3. A magnetron comprising a cathode and a hollow cylindrical conductive portion housing said cathode, a plurality of parallel-sided Walls of conductive material difierent from that of said cylindrical conductive portion encircled thereby axially shorter than said cylindrical portion, and projecting from the inner surface thereoi in generally radial directions defining a central cathode cavity communicating with pockets disposed therearound, the outer edge portions of said Walls fitting in grooves in the inner surface of said hollow conductive portion and held in place by solder, and cover members secured to the parts of said cylindrical portion which project axially beyond said walls.

4. An electron-discharge device comprising: a cathode; and an anode structure spaced from and surrounding said cathode and including a plurality of anode members, each pair of adjacent anode members comprising vanes secured in inwardly opening slots in a peripheral portion of said structure, thereby defining therewith a cavity resonator, said vanes having substantially straight side walls defining cavities expanding for an appreciable distance between the inner and outer ends thereof, leads from said cathode projeoting through said anode structure to outside of said device, an output lead extending into said structure in a generally radial direction, curved backward and united to the inner surface of the outer portion of said structure, and a conductor casing in contact with and. projecting outwardly from said outer portion and disposed coaxial with respect to said lead.

ERNEST C. OKRESS. ILIA E. MOUROMTSEFF.

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

UNITED STATES PATENTS Number Name Date 1,547,836 Steenstrup July 28, 1925 1,666,833 Rhodes et al. Apr. 17, 1928 2,063,342 Samuel Dec. 8, 1936 2,129,713 Southworth Sept. 13, 1938 2,167,201 Dallenbach July 25, 1939 2,247,077 Blewett et al. June 24, 1941 2,270,777 Von Baeyer Jan. 20, 1942 2,295,396 George Sept. 8, 1942 2,304,186 Litton Dec. 8, 1942 2,408,235 Spencer Sept. 24, 1946 FOREIGN PATENTS Number Country Date 509,102 Great Britain July 11, 1939 215,600 Switzerland Oct. 16, 1941 527,131 France July 18, 1921

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