US2635210A

US2635210A - Magnetron

Info

Publication number: US2635210A
Application number: US651318A
Authority: US
Inventors: Millman Sidney
Original assignee: Individual
Current assignee: Individual
Priority date: 1946-03-01
Filing date: 1946-03-01
Publication date: 1953-04-14
Anticipated expiration: 1970-04-14

Description

April 14, 1953 5 MlLLMAN 2,635,210

MAGNETRON Filed March 1, i946 'l'l'l'l'l'l 0.0. SOURCE 0R MODULATOR FIG.5. FIG.5A

IN V EN TOR.

SIDNEY MILLMAN B Y b J WMM ,9- H 1 Patented Apr. 14, 1953 MAGNETRON Sidney Millman, Brooklyn, N. Y., assignor to the United States of America. as represented by the Secretary of War Application March 1, 1946, Serial No. 651,318

6 Claims. 1 This invention relates to ultra-high frequency generators of magnetron type in which ultra-high frequency oscillations are generated by a bunched plurality of resonators set into oscillation by high velocity electrons moving along curvilinear, orbital paths, these paths being followed by the electrons because of the joint action of the electric, magnetic and radio frequency electromagnetic fields.

It is an object of this invention to provide an improved ultra-high frequency magnetron with an anode structure having higher efficiency obtained by an increase in the L/C ratio of each cavity.

t is an additional object of this invention to provide simplified anodestructure and methods of manufacturing anodes for ultra-high frequency magnetrons.

The invention discloses an improved anode structure and the method of its manufacture which facilitates their production from a mechanical point of view. Moreover, it also results in the productionof an anode with superior electrical characteristics including higher circuit eniciency. The smaller losses are obtained by increasing the inductance L of the oscillating circuit accompanied by a decrease in its capacitance.

These and other features of the invention will be more clearly understood from the following detailed description and the accompanying drawings in which:

Figure l is a plan view of an anode block with anode vanes indicated by dotted lines,

Figure 2 is a side, cross-sectional view taken along line 22 of the anode block illustrated in Fig. l,

Figure 3 is a perspective view of a jig used in assembling the anode block and the vanes, the latter two being illustrated in Fig. 3 in section,

Figure 4 is a perspective view of an anode vane,

Figures 5 and 5-A are enlarged plan and side views of a portion of the anode ring and several vanes;

Figure 6 is a plan view of a magnetron withthe top cover of the anode removed;

Figure 7 is a vertical, cross-sectional view,

taken along line l-|, of the magnetron illustrated in Fig. 6.

.in Fig. 2. Bore is provided in the block for facilitating the subsequent assembly of the anode block illustrated in Figs. 1 and 2 is a fourteenvane block. The upper portion of the block as seen in Fig. 1 is provided with fourteen radial slots l2 which are cut in the block on a milling machine. The center lines of the slots i2 emanate from center 14 of the cylindrical block. and the sides of the slots are parallel to their respective center lines. The side View of two slots lzaand l2b are illustrated in Fig. 2. The slot axial length 21 extends beyond the anode portion IQ of the block. The milled slots l2 in the anode block are used for holding the anode vanes, one of which is illustrated in Fig. l. The vanes are made of copper and represent rectangular plates it of uniform thickness, 52. Edge 31 of the platerepresents the inner surface or a pole-piece of the anode resonator facing the cathode. The height 55 of the plate I8 may be either larger or equal to the depth 34 of the slots depending upon whether the upper and lower portions of the finished anode structure are leveled, upon the completion of the anode assembly, on a milling machine as will be described later. After completion of the milling operation of the anode block, rectangular plates l8 are inserted into the slots in the following manner: block In is placed on an assembling jig l9 illustrated in Fig. 3. The jig consists of a cylindrical base 20 and two

cylindrical pedestals

22 and 24. The diameter of pedestal 24 is made equal to the innerdiameter 58 of the assembled anode. The diameter of pedestal 22 is substantially equal to the inner diameter of bore I l in the anode block so that the block forms a tight sliding fit over the pedestal 22, and resting on the top surface of pedestal 20. The height of pedestal 22 isequal to the non-slotted height 26 of the anode The anode block in proper made by placing vanes in this block. The so block. Therefore, when block it) is placed on the jig, the flat bottom surfaces 2? of the slots i2 are on the same level with the flat circular area 28 of the jig. After the anode block has been mounted on the jig, in a manner illustrated in Fig. 3, the

anode vanes l8, whichform a tight sliding fit with the anode slots 12, are inserted into the slots so that the inner tips of the vanes rest against the cylindrical pedestal 24. The latter pedestal thus insures proper. centering of the vanes within the anode block. The circular surface 28 of the jig and the bottom surfaces 21 of the slots provide rest surfaces which align the lower edges 350i the vanes so that the inner tips Si of the vanes form a true cylindrical locus defining the outer boundary of the discharge space between the cathode and the anode of the magnetron, After the insertion and alignment of the anode vanes inthe anode block the latter is removed from the jig and placed into a hydrogen bottle for soldering the vanes to the block. A high melting point silvercopper may be used for completing this soldering operation. It is advisable that the soldering operation is performed in a hydrogen bottle to avoid any oxidation of the anode structure. Upon the completion of the soldering operation, the anode block is taken out of the hydrogen furnace, allowed to cool, and then placed on the milling machine. Here the excess portion of the copper block, represented by ring 32 in Fig. 2, is cut oil to a depth represented by a dimensional arrow'33 in Fig. 2. The milling operation also cuts off the bottom portions of the vane plates 18 which, as it will be remembered, projected beyond the depth of the anode portion proper I6. The same leveling operation is performed in the upper surface of th anode. This completes the manufacturing steps of the anode structure; a portion of the completed structure is illustrated on an enlarged scale in Figs. 5' and5-A.

The radial length 5! of the anode vane is determined by the wave length of the magnetron,

while its thickness 52 and opening 53 of the anode cavity are controlled by the running wave oscillations typical of this type of anode structure. If t is the vane thickness and a. is the cavity opening, the ratio of t/a should be equal at least to unity; the efliciency improves with the increase in this ratio; this ratio may be as high as 2; for short wave magnetrons (12 cms.) the optimum value of this ratio was found to be in the order of 1.8.

Referring now to Figs. 6 and '7, after completion of the assembly and finishing of the anode block i0 it is inserted into a copper shell 666. The anode forms a tight sliding fit with the shell and upon the insertion of the anode into the shell, with the aid of proper jigs, the shell and the anode are soldered together by means of RT solder (16% silver, copper, 15% zinc) which has a lower melting point than the BT solder previously used for soldering the anode vanes to the anode block. Anode block 666 is made of oxygen-free, high-conductivity copper which is provided with recesses Bill and 602 for holding tightly fitting bronze or copper shell-covers 694 and 606. These covers, upon the completion of the assembly of the magnetron, are soldered to the anode shell with one of the above-mentioned solders to make an air-tight joint with the shell.

The upper end space 669 of the magnetron is used for inserting the coupling loop 6H] and a concentric line 612. The line includes a tapered, copper sleeve 6M, forming an airtight joint with the shell, metallic eyelet M6 in a glass seal 618 with the center conductor 620 of the line projecting through the glass seal. Conductor 626 terminates in the coupling loop 616 which is placed directly above one of the resonating cavities of the anode as illustrated more clearly in Fig. 6. One end of the loop is connected to the inner end of the copper sleeve 614 in the usual and this coaxial relationship. is maintained by

glass seals

628 and 629 respectively. The cathode itself consists of a nickel cylinder 630 coated with electron-emitting oxide or a mixture of several oxides. The cathode is provided with two hats for shielding the discharge space from the end spaces. Within the nickel cylinder 630 of the cathode is a heater coil, not visible in any of the figures, which is connected to the cathode conductors 621 and 622 by jumpers 6'3! and 632, which complete the circuit of the cathode. While conventional radial type of cathode structure has been illustrated in'the figures, itis to be understood that the package-type or soldering iron type of cathode structures could be used for accomplishing the desired result. Moreover, when the radial type of the cathode structure is used, it may have the provisions for maintaining properly centered position of the cathode with respect to the anode at the operating temperatures of the magnetron, such as those described in the application for patent of Polykarp Kusch, Serial No. 604,071, filed July 9, 1945, entitled Coaxial Cathode Lead for Magnetron. Two

polepieces

633 and 634 are placed directly on the plates 604 and 666 of the shell, these pole-pieces being directly connected to the permanant magnets not illustrated in the figures. The magnets furnish the necessary magnetic field for the discharge space of the magnetron. I

From the foregoing it will be apparent to those skilled in the art that I have provided an improved magnetron and the method of manufacturing the latter. The disclosed method simplifies the manufacturing techniques of the anodes. Besides facilitating the manufacturing techniques, I have also produced a magnetron having higher electrical eficiency and higher power capacity. The higher efficiency is obtained because of the inherently lower losses in the disclosed anode structure. The higher power capacity is obtained because of the higher circuit efficiency.

While the invention has been described with reference to several particular embodiments, it will be understood that various modifications of the apparatus shown may be made within the scope of the following claims.

I claim:

1. An anode for an ultra-high frequency magnetron comprising 'a plurality of conductive wedge-shaped elements mounted in a circle and spaced from one another and a like plurality of conductive vanes disposed between and connected to said elements forming a composite ring,

said vanes extending from the inner surface of said ring and forming with the inner surfaces of said elements cavity resonators of sector-shaped cross-sections.

2. An anode as defined in claim 1 in which the ratio of the thickness of said vanes to the air-gap between the inner ends of said vanes is between unity. and two.

3. An anode for an ultra-high frequencymagnetron comprising a plurality of conductive wedge-shaped elements mounted in a circle and uniformly spaced from one another and a like plurality of rectangular metallic vanes radially disposed with respect to said, circle between said wedge-shaped elements and electrically connected to saidelements forming a composite said anode, said block being provided with a plurality of radial slots extending radially therethrough and axially at least along the entire length of said first bore.

5. An anode block for a magnetron anode having a plurality of cavity resonators therein, said block being provided with first and second cylindrical bores coaxially aligned, the radius of said first bore being smaller than that of said second bore and being equal to the outer radius of the cavity resonators of said anode, said block being provided with a plurality of radial slots extending radially therethrough and axially at least 7 along the entire length of said first bore, said slots being dimensioned for holding vanes which form the cavity resonators of said anode.

6. A magnetron anode comprising, an anode block provided with first and second coaxially aligned cylindrical bores, the radius 01 said first bore being smaller than that of said second bore, said block being provided with a plurality of radial slots extending axially along the entire length of said first bore, and an equal plurality of vanes disposed respectively within said slots and extending the entire axial and radial lengths of said slots into the center of said block, the spaces between said vanes forming a plurality of cavity resonators disposed within and extending the entire length of said first bore.

SIDNEY MILLMAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,063,342 Samuel Dec. 8, 1936 2,247,077 Blewett et a1. June 24, 1941 2,305,781 Helbig Dec. 22, 1942 2,408,238 Spencer Sept. 24, 1946 2,410,396 Spencer Oct. 29, 1946 2,416,899 Brown Mar. 4, 1947 2,520,955 Okress et al. Sept. 5, 1950 2,542,966 Randall et al. Feb. 20, 1951 FOREIGN PATENTS Number Country Date 509,102 Great Britain July 11, 1939