US2458802A - Magnetron assembly and method - Google Patents

Description

Jan. 11, 1949.

P. 1.. SPENCER 2,458,802

MAGNETRON ASSEMBLY AND METHOD Filed March 50, 1942 5y (SQ/71AM,

wrney Pawn 'L @verwew Y Patented Jan. 11, 1949 MAGNETRON ASSEMBLY AND METHOD Percy L. Spencer, West Newton, Mass., assignor to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application March 30, 1942, Serial No. 436,891

18 Claims. 1

This invention relates to a magnetron, and more particularly to a magnetron in which the (dimensions and configurations of the internal structure determine the frequency of the oscillations generated.

Magnetrons of the foregoing type have heretofore been constructed by carefully machining the casing or anode structure out of a solid block of copper. Since the frequencies intended to be generated by such magnetrons are of wave lengths of the order of centimeters or even fractions thereof, minute changes in the dimensions of any part of such structure would produce large changes in the frequencies generated. Therefore, in order to produce the proper frequency and also to keep various oscillating parts of the structure at the same natural frequency, the machining had to be carried out with extreme accuracy. This made the manufacture of such magnetrons slow and expensive.

An object of this invention is to devise a magnetron structure which can be made rapidly and inexpensively without sacrificing the accuracy with which the component parts are made.

Another object is to devise a magnetron structure and a method of making the same which can be carried out on a mass production basis by relatively unskilled operators.-

The foregoingand other objects of this invention will be best understood from the following description of an exemplification thereof, reference bein had to the accompanying drawings,

wherein: I

Fig, 1 is a longitudinal cross-sectional View of a magnetron constructed in accordance with my invention; 7

Fig. 2 is a top view of one of the stamped laminas from which the magnetron casing is constructed;

Fig. 3 is a top view of another of the stampe laminas from which the magnetron casing is constructed;

Fig. 4 is a top view of one of the stamped end caps of the magnetron of Fig. 1; and

Fig. 5 is a view of an assembly jig illustrating the method of assembling the laminas.

The magnetron illustrated in thedrawing com prises an envelope structure forming the anode of the magnetron, a cathode structure '2, and a pair of end caps 3 and 4. The anode structure is so arranged that when the device is placed between magnetic pole pieces 5 and 6, oscillations are generated, the frequency of which is determined by the geometry and internal structure of the anode assembly. These oscillations are picked 2 up by a coupling loop I, and are led to a suitable utilization device.

As pointed out above, heretofore the entire casing of the magnetron had been made of carefully machined parts, thus rendering the manufacture very slow and expensive. In accordance with my invention I construct the casing of all stamped parts. Thus the anode structure is made up of a plurality of flat stamped laminas 8 and 9. Each lamina is formed with a central opening I 0 and a plurality of radial slots, each terminating in a circular opening 12. The laminas 8 and 9 are intended to be stacked alternately. Each lamina 8 is of smaller outer diameter than that of each lamina 9, leaving projecting portions of the laminas 9 which from cooling fins for the final form of the magnetron. In a practical example, each lamina 8 may be about two inches in diameter and each lamina 9 may be bout three inches in diameter, while the thickness of each of them may be about .070 inch. These laminas are formed of some suitable conducting material which may be readily and accurately stamped. I'prefer to use copper.

The dies for stamping the laminas 8 and 9 may be made very accurately, and large numbers of such laminas can be stamped out of sheet copper with such dies. The dimensions of the openings H] and I2 and of the slots H are critical in such a device. However, with the use of such accurate dies, these critical dimensions are readily obtained in the stamping of the laminas.

The end caps 3 and 4 likewise can be stamped from sheet copper. However, the dimensions of these caps are not as critical as those referred to above. The caps 3 and 4 are each made with a central dish-shaped portion l3 surrounded by an annular rim M. The upper cap 3 is provided with two conducting pipes l5 and I 6 which are hermetically sealed through the sides of the dishshaped portion l3. Sealed to the outer end of the pipe I5 is a glass seal I! through which a pair of cathode lead-in conductors l8 and I9 extend. The cathode 2 comprises a sleeve 20 of a suitable conducting material such as nickel, and bearing a suitable emissive coating on the external surface thereof. A desirable coating arrangement is that described and claimed in my copending application, Serial No. 412,993, filed September 30, 1941, now Patent No. 2,411,601, dated November 26, 1946. A heater 2| is supported within the sleeve 29 by having its ends extend through insulating blocks 22 mounted in opposite ends of the sleeve 20. The ends of the heater 2| preferably carry tantalum shields 23 which tend to prevent electrons emitted from the cathode from passingv out through the ends of the central opening to the caps 3 and 4. The lead-in. conductor !8 is connected to the upper extended end of the heater. The lead-in conductor I9 is connected to the sleeve 20 by a connector extending through an opening in the shield 23. The lower shield 23 may also be connected to the sleeve 20. By the above arrangement, the lead-in conductors l8 and I9 may serve as the heater current leads, the lead-in conductor 59 also serving as the cathode lead. The conductors l8 and I9 also serve to support the cathode structure. In order to steady and center the cathode structure, a mica guide plate'24 is mounted Within the end cap 4. The guide plate 24 may be supported in any convenient manner, as. by a plurality of supporting studs 25 fastened to the cap 4. The guide plate 24 has a central opening into which the lower extendedend of the heater 2 may be inserted during assembly.

The conducting pipe preferably extends through thewall of the cap 3 and into the interior of the magnetron structure. The outer end of the pipe l6 carries a glass seal 26 through which is sealed a lead-in conductor 21. The inner end of the conductor 2'! is" bent, passes through an opening in the sidewallof the tube 56, andis connected to one end of the coupling loop 1. The other end of the coupling loop may be connected to the. outer wall of the pipe l6. Loop 1 is in a plane at right angles to the plane of Fig. 1', and thus is inductively coupled to one of the bores formed by the aligned openings l2 of the laminae 8 and 9. The pipe [6 may also have an additional conducting pipe 28? connected thereto. This conducting pi'pe surrounds the conductor 2-? and forms a concentric transmissionline therewith so that the oscillations produced by the device may be transmitted to the desired point.

In order to form the anode structure, alternate Iaminas 9 and 8 maybe assembled in a stack on an assembly jig. 29', as shown, for example, in Fig. 5. Preferably the end lamina'so'i such a stacl arethelargelaminas 8'. The jig 29. maybeprovidedwith a central pin 30 corresponding to the openings HI, and with a plurality of pins 3|" cor responding to the openings l2. In this way, merely by stacking the l'arninas on the jig 29,

thecorresponding openings in the laminas are aligned with each other; forming a'central bore in which the cathode is to be supported, and a plurality ofbores corresponding to the openings I2. Likewise the slots H are aligned, formingradial passages interconnectingthe central bore with the plurality of surroundingbores.

While assembling the laminas on the jig '29-, a. thin ring. of suitable solder, such as silver, is inserted between each adjacent lamina. These solder rings need only be placed at the outer edges of the laminae 8,.extending from the outside perimeter thereof to a point: somewhat short'of the outer edge ofthe openings l2. The'thickn'ess of each solder ringmay be about .002 inch, for example. If desired, tin may be used as the soldering metal.

After the: laminas? and. solder rings have been assembled on the jig 29; they are clamped together, and the assemblyis passed through a hydrogen' furnace. This causes the solder to melt, andifuses' thestack of laminas into herm'etical ly-tight unitary block. is removed before the assembly is placed in" the furnace; although it may be left in place until after the assembly. is removed from the furnace;

Preferably the. jig 29" through'the' hydrogen furnace.-

In the latter case the pins 30 and 3! may be oxidized or graphitized on their surfaces in order to prevent any solder sticking thereto.

The cap 3 is assembled with the pipes l5 and i6 carrying their respective seals and lead-in conductors. These pipes are preferably soldered in place by means of silver solder. The cathode assembly may then be mounted on the lead-in conductors I8 and i9, and the coupling loop 1 maybe mounted on the lead-in conductor 21 and the pipe Hi. The cap 4 is assembled with the guide plate 24, and is then soldered in place on the lower end of the anode block. The upper cap 3 is then placed in position, care being taken that the lower extended end of the heater 2! projects through the central opening in the guide plate 24. Thereupon the cap 3 may be soldered in place on the anode block. The magnetron may then be evacuated and freed of occluded gases in accordance with the usual practice, and the cathode may be properly activated, which completes the construction.

It will be seen that in the completed assembly the anode structure'is provided with a plurality of wedge-shaped arms, the faces of which are adjacent the cathode and cooperate as anode sections with the cathode. A capacity exists between the cathode 2- and each such anode face. Also capacitanc'e's exist between the side walls of each of the aligned slots H. The inner walls of the aligned openings 12 constitute inductances. When" the magnetron is energized and placed'between the pole pieces 4 and 5, it generates os'cillations as mentioned above; The frequency of these oscillations is determined by the inductances and c'apacitances above mentioned. These inductances and capacitanc'es constitute resonant circuits at the desired frequency, and each of the resonant circuits cooperates with each other resonant circuit to contribute to and enhance the oscillations produced by the tube as a whole.

A magnetron as constructed above is readily made sothat each of the resonant circuits has exactly the proper natural frequency Without the expensive and time-consuming machining which heretofore had been necessary. If increased accuracy is desired, the anode structure might be placed in a coin" or sizing die after it has been In this Way any slight inaccuracy in size of parts is eliminated by pressing the metal of the anode block to the exact size as determined by the sizing die. All of the' operations required to produce a magnetron as described' above may be performed by relatively unskilled operators, and lend themselves readily to mass' production methods. The time for making m'a'gnetrons is greatly decreased over that which had heretofore been necessary, and the cost thereof isgreatly decreased.

Of course it is to be understood that this invention is not limited to the particular details as described above as many equivalents will suggest themselves to those skilled in the art. It is accordingly desired that the appended claims be given a broad interpretation commensurate with the scopeof the invention within the art.

What is claimed is 1 1. An electron discharge device comprising a metal envelope enclosing an elongated cathode and electrode elements between which a space discharg'e'is adapted to take place, said envelope being formed integrally with said electrode elements, end caps on said envelope, one end of said cathode beingc'arried by one of said end caps, a projection on the other end of said cathode, and an insulating plate carried by the other of said end caps, said plate having an opening into which said projection of said cathode extends.

2. An electron discharge device comprising a metal envelope enclosing electrode element-shetween which a space discharge is adapted to take place, said envelope being formed integrally with certain of said electrode elements forming an electrode structure having a configuration con.- stituting capacitance and inductance. elements forming circuits which are adapted to have oscillations set up therein, and an end cap for said envelope, said end cap carrying a coupling loop held adjacent one of said inductance elements, one end of said loop being connected to said end cap, the other end of said loop being connected to a conductor insulatingly sealed through said end cap.

3. A discharge tube comprising a cathode surrounded by a laminated anode block, said anode block consisting of a series of stacked laminas, each lamina having a central cathode space, and a plurality of spaces interconnected with said cathode space and forming coupled cavity resonators.

4. An electron discharge device comprising a cathode, a laminated anode block adjacent said cathode, said anode block comprising a series of stacked laminas, each lamina having a cathode space, and a space forming a cavity resonator connected to said cathode space.

5. An electron discharge device comprising an envelope containing a cathode surrounded by a laminated anode block, said anode block comprising a series of stacked laminas, each lamina having a central cathode space, and a plurality of spaces interconnected with said cathode space and forming coupled cavity resonators, said anode block constituting a wall member of said envelope, certain of said laminas being of increased diameter extending beyond other of said laminas and forming cooling fins.

6. The method of forming a laminated anode block of an electron discharge device having a cathode space and a cavity resonator, said method comprising forming a plurality of copper laminas, each having a cathode space, and a space forming a cavity resonator, stacking said laminas into the anode configuration with an intervening lamina of silver solder between each lamina, placing said stacked laminas in an atmosphere comprising hydrogen, and raising said stacked laminas to a temperature at which said solder laminas fuse.

'7. The method of forming a laminated anode block of an electron discharge device having a cathode space and a cavity resonator, said method comprising forming a plurality of sheet metal laminas, each having a cathode space, and a space forming a cavity resonator, stacking said laminas into the anode configuration with an intervening lamina of silver solder between each lamina upon a jib having aligning members projecting into said cathode space and said cavity resonator for maintaining said laminas in the desired configuration, said aligning members having surfaces which are nonadherent to said solder when said solder is fused, and raising said stacked laminas to a temperature at which said solder laminas fuse.

8. The method of forming a laminated anode block of an electron discharge device having a cathode space and a cavity resonator, said method comprising forming a plurality of copper laminas, each having a cathode space, and a space forming a cavity resonator, stacking said laminas into the anode configuration with an intervening lamina of silver solder between each lamina upon a jig having aligning members projecting into said cathode space and said cavity resonator for maintaining said laminas in the desired configuration, said aligning members having surfaces which are non-adherent to said solder when said solder is fused, placing said stacked laminas'in in an atmosphere comprising hydrogen, and raising said stacked laminas to a temperature at which said solder laminas fuse.

9. An electron discharge device comprising a tubular anode, a cathode in and coaxial with said anode, said anode comprising a plurality of individual discs of sheet metal with central holes corresponding in size and shape with the desired internal cross-sectional size and shape of said anode, said discs being stacked with said holes in registry and being hermetically joined together, the inner edges of the discs being exposed directly to said cathode.

10. An electron discharge device comprising a hollow anode electrode, the walls of said elec trode being laminated, the laminas extending transversely through the wall of the electrode to its outside surface from its inside surface, and the laminas being hermetically sealed together.

11. An anode comprising a plurality of stacked metal discs, the discs having registering irregular shaped openings within the peripheries of the discs, the size and shape of the holes corresponding to the desired cross-sectional configuration of the inner wall of the anode, the contacting faces of the discs being hermetically sealed together.

12. An anode comprising a laminated tubular member, the laminas of the member comprising metal discs with central openings stacked in parallel planes transverse to the axis of the memher with the sides of the discs in contact and with some of the spaced discs in the stack extending outwardly beyond the outer wall of the member.

13. A laminated tubular anode, the laminas of the anode comprising silver-plated sheet copper discs with registering openings, the silver surfaces of the discs being hermetically sealed toether.

14. An electron discharge device comprising a tubular anode, a cathode concentric with and in the anode, said anode comprising a plurality of metal discs hermetically joined along their peripheries, each disc having a central hole and a plurality of radially extending slots from said hole, the discs being stacked with the slots of each of said discs being disposed one above the other to provide cavities, of the desired longitudinal configuration, about said cathode.

15. A laminated tubular anode, the laminas of the anode comprising a plurality of thin sheet metal discs, the discs each having a round hole and a communicating narrow slot, the holes and slots being in registry in the stack of discs to define a cylindrical bore and an elongated narrow cavity extending longitudinally of the anode.

16. The method of fabricating a tubular envelope wall for an electron discharge device, the wall having spaced cooling fins on its outside surface and having an electron collecting area of any desired configuration on its inside surface, comprising cutting two groups of metal discs of differ ent diameters, cutting holes having the desired configuration in the first group of metal discs, cutting holes having said configuration in the sec- 0nd group of Inetaldiscs, stacking andinterleav-- ing thediscs of the two groups with their, holesin registry, and hermetically joining, the. discs.

17. A fabricated tubular envelope wallfor an electron discharge device comprising a first group of metal discs having holes of the desiredconfiguration in said discs, a second group of metal discs having outside diameters larger than the outside diameters of said first group ofmetal discs and having holes cut in the discs corresponding to the holes of said first group of metal discs, the discs of the two groups being, stacked and interleaved, with the holes ofthe discs in registry, and the discs all being hermetically joined together.

18. A cathode mounting comprising a cathode, afilament within said cathode with the ends of the-filament projecting at the ends of the cathode, a support opposite the end of the cathode, one end of said filament, being within and held by said support, and a conductive plate between said support and cathode and secured to said last-named end.

PERCY L. SPENCER.

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

UNITED STATES PATENTS Number Name Date 1,684,947 Daumann Sept. 18, 1928 1,787,082 McCullough Dec. 30, 1930 1,879,544 Scognamillo et a1. Sept. 27, 1932 2,043,733 I Brasch et al June 9, 1936 2,063,342 Samuel Dec. 8, 1936 2,121,598 Kerschbaum et a1. June 21, 1938 2,183,157 Samuel June 20, 1939 2,186,127 Samuel Jan. 9, 1940 2,289,984 Mouromtseff et a1. July 14, 1942 2,305,781 Helbig Dec. 22, 1942 FOREIGN PATENTS Number Country Date 216,562 Great Britain May 23, 1924 509,102 Great Britain July 11, 1939

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