US2530185A - Electron discharge device - Google Patents

Description

Nov. 14, 1950 H. L. STEELE, JR

ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 1 Filed Nov. 4, 1944 INVENTORI H. z, .SrEEAE, J76.

ATTORNEY Nov. 14, 1950 H. L. STEELE, JR

7 ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 2 Filed Nov. 4, 1944 INVENTOR W 5 1 W H m V E N R Q T A Patented Nov. 14, 1950 ELECTRON DISCHARGE DEVICE Howard L. Steele, Jr., Bloomfield, N. J., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 4, 1944, Serial No. 561,890

This invention relates to electron discharge devices of the character known as magnetrons, and more particularly to tuning means for the same. v

Considerable attention has been directed recently to the possibilities of tuning magnetrons that the output therefrom may be varied as to wave length. Efforts to accomplish this desideratum have been largely confined to provision of movable members, usually in the resonant cavities, but the results have been unsatisfactory from the standpoint of loss of power attendant upon introduction of obstacles in the cavities tending to interrupt or impede the magnetic flux therethrough. According to the present invention, means are provided for varying the internal or tube capacity, and consequently the output frequency, without appreciable loss of power output. Thus, the objectives of tuning and maintaining high rating of output are advantageously solved.

More specifically, an object of the invention is to utilize strapping of the segments as the capacitative tuning means.

Another object of the invention is to require transmission of a minimum amount of motion from the exterior to the interior of the device for tuning purposes.

A further object of the invention is to require minimum alteration of dimensions of presentday magnetrons to adapt the same to include the invention.

Yet another object of the invention is to provide effective, simple and wide-range electrical tuning means for a magnetron.

Other objects of the invention will appear to those skilled in the art as the description progresses, both by direct recitation thereof and by inference from the context.

Referring to the accompanying drawings in which like numerals of reference indicate similar parts throughout the several views;

Figure 1 is a vertical central sectional view of a magnetron constructed in accordance with and showing the preferred form of tuning means of the present invention;

Figure 2 is a cross-sectional view taken on line 11-11 of Fig. 1;

Figure 3 is a detail sectional view of a part the magnetron as on line III-III of Fig. 2;

Figure 4 is a perspective view of the straps or rings and indicating angular relationship thereof when assembled in the magnetron;

Figure 5 is a detail cross-section of the engaging shoulders of the anode;

strap-- 11 Claims. (Cl. 250-27.5)

Figure 6 is a cross sectional view correspondin to Fig. 1 and showing a modified-construction of tuning means therein;

Figure 7 is a cross sectional view on line VII-VII of Fig. 6;

Figure 8 is a plan with cover or end plate removed of a magnetron having a modified construction of tuning means therein;

Figure 9 is a vertical sectional view corresponding to Fig. 6 and showing a further modified construction of tuning means.

Figure 10 is a sectional plan of yet another construction tuning means. 1

Figure 11 is a perspective view of a strap sectio as utilized in the construction of Fig. 10; and

Figure-l2 is another perspective view of the strap section modified for electrical tuning.

Referring now specifically to the embodiment of the invention illustrated in the several figures, and with attention initially devoted to Figs. 1 to 5, the reference numeral I0 designates a cylindrical metallic magnetron body, the ends whereof have cover or end plates H sealed thereon that the interior may be evacuated. Within and as an integral part of said body is the usual magnetron anode structure [2 of generally cylindrical shape but shorter than the outer part of the body so as to provide end spaces [3 between the anode and said end plates H. The anode structure'is axially hollow to provide a cathode cavity for a cathode l4 and radiating from this cathode cavity are a plurality of resonant cavities [5, each having, in the form shown, a cylindrical portion parallel to the cathode cavity and each having a longitudinal constriction or slot opening into the cathode cavity. A desired capacitance exists across the constricted space between the cavity faces, and a concentration of E-lines will exist thereat in use. The walls between cavities are generally designated segments or vanes IS. The ends of the cathode cavity and the ends of said resonant cavities, including said constrictions, open into the end spaces l3. Cathode l4 passes axially through the cathode cavity, adequately spaced from the anode, and is supported In the pre--' 3 ferred form of the present invention, however, the strapping of both series of alternate sections is accomplished at a single end of the anode. Accordingly, at one end of the anode body, and here shown at the upper end and at the edge of the segments next the cathode cavity, there is provided an annular stepped recess providing what may be termed a deep step i9 and a shallow step 20. The deeper step is nearest the cathode and the shallow step is of larger diameter than the deep step. A cylindrical riser wall 2| extends from the rear of the deep step to the front edge of the shallow step, and a cylindrical riser wall 22 extends from the rear of the shallow step to the end face of the anode body or segments thereof.

A strap in the form of a washer-like ring 23 is mounted on the deep step but in a manner to only contact the step in every alternate segment.

As the anode shown has eight segments, said ring 23 is provided with only four evenly spaced cars 24 for engagement with four alternate segments. Said ears project radially beyond the general peripheral outline of the strap and bend downward next their outer ends, as at 25, so that the only contact of said strap with the anode will be the contact of the said downwardly bent ear portions against the riser wall 2| of the alternate sections. and against the rear of the lowerstep. The strap is preferably secured in place by soldering the contacting bent ear portions to the riser wall. Similarly, an upper strap 23a is provided for the shallow step, this strap also having ears 24a with downwardly bent outer ends 250. Thereare likewise shown only four ears on this strap 2-30. and they are located in'theassembly to seat on the shallow step of the segments intervening between the segments engaged by the ears of the first-mentioned or lower strap 23. The alternating relationship of ears is indicated in Figure l. The ears of the upper strap fit against the riser of the shallow step and are soldered in place. Both straps are provided with large central openings for'appropriate clearance around the cathode. Attention is directed to the fact'that each segment makes contact with no other part of the device than the particular alternating sections to which the" ears are soldered, and the sections make no contact with each other, but rather provide a space, hereinafter referred to as the strap space, between the said straps.

The construction as thus far described provides", by virtue of the parallel straps and intervening strap space, a relatively high strap capacitance which parallels the capacitance of the cavity constrictions or slots. Electrons introduced into the slot space will change the capacitance between the straps. This change of capacitance is the result of the electrons changing the dielectric constant of the strap space and the change. will depend in extent upon the number of electrons in said strap space; more electrons in the space result in decreased capacity. As a part of the length of the cathode passes through the straps; it serves as a direct source of electrons thereat: for entry into said space. Control of quantity of electrons from the cathode to said strap space is obtained'by'interposing a grid 26.

It may be said at this point that utilization of the magnetron cathode as a source of electrons both for power and for tuning is conducive to simplicity and to effective and eificient operation, but itis within the scope of the invention to provide separate sources of electrons for these purposes if so desired. Furthermore, it may be pointed out that electrons emitted from the oathode travel in approximate cycloidal paths under the influence of the magnetic field, and when the magnetron is oscillating, electrons will follow the cycloidal paths and traverse the strap space, except as blocked or controlled by the grid.

Inasmuch as the grid 26 will be heated by radiation from the cathode and by bombardment of electrons, it is desirable to have the grid in the region of lowest operating temperature and least emission. This desideratum is agreeably satisfied by situating the grid next the end of the cathode, which also is the most desirable position for the straps; thus both conditions are satisfied. It is to be understood that nearness of the rid to the cathode may be made to meet conditions of both heat and electron emission so as to positionthe grid at the most optimum spacing between cathode and strap.

As one convenient means for mounting grid 26, a cylindrical ceramic 21 supporting both the cathode and grid may be provided. Said ceramic is shown as having successively smaller girth areas, the largest of which is next the top,- and each successive smaller girth portion thereby provides a downwardly facing shoulder. A metal ferrule 23 around the largest girth portion has a flange under the first shoulder and another flange at its upper end welded to an end plate 29 in turn secured to the lead-in rod I 1. One of the smaller or intermediate girth portions of the ceramic 2? receives and sustains the upper end of grid 26, and the next smaller or lower girth portion is shown receiving the end of the cathode thereon.

A lead-inconnection 30 is secured to the rid at the upper or secured part of the grid, the connection passing to the exterior without contact with the magnetron wall through a suitable fitting 3| which includes insulation as usual. The grid has a length shown as locating the lower end of the grid just below the lower strap. A potential may therefore be applied to the grid and varied as desired to vary the gradient at the grid-surrounded part of the cathode, thus controlling the number'of electrons that get into the strap space, and this introduces desired regulation of the strapspace capacity whereby control of the potential to the grid effects the desired tuning,

The construction of Figures 6 and 7 provides a magnetron body, anode, resonant cavities, end plates and end cavities as described in general above. although for simplifying disclosure, illustration of the cathode is omitted in these figures since its presence, support and function are in accordance with prior art practice. As shown, concentric cylindrical straps or rings 32 are mounted on the upper part of the anode body and within the end space. These straps are secured one to alternate segments ifia of the anode body and the other to the intervening alternate segments, said straps contacting only the alternate segments to which attached and being spaced from each other leaving a strap space therebetween. This strap space is upwardly open, that is, opens toward the end plate for the end space in which the straps are located. Said straps are preferably rigid and are soldered to the respective alternate segments. The capacitance between said straps exerts its influence on the internal or tube circuit and is therefore one of the factors determining the frequency and wavelength of the magnetron output.

Means are provided for varying the capacitance between said cylindrical straps. In the showing of Figures 6 and 7 the means mentioned 7 comprises a cylindrical member such as sleeve 34, the wall thickness whereof is less than width of the strap space, and the diameter whereof is intermediate of the diameters of the two straps.

Consequently, by mounting the said cylindrical member coaxial to the straps, it may be moved into and out of the strap space in an axial direction. Said cylindrical member or sleeve 34 may be either a dielectric or a conductor, and as shown, is a dielectric. Use of a dielectric sleeve tends to lower the output frequency, whereas use of a metallic sleeve would tend to raise the frequency. By having like straps at both ends of the anode body, with a movable member or.

sleeve for each strap space, tuning effect can be applied at both, and said sleeves may then be both metallic, both dielectric or one metallic and the other dielectric.

Movement of the sleeve is effected by means of a screw shown fast upon a plate 36 with the rim of said plate annularly channeled to receive and hold the said sleeve. At the outside face of said plate is secured with a vacuum tight joint the lower end of a bellows 31, the upper end of which is sealed to the end plate. Depending into the bellows and rotatable in the end plate Ila is a nut 38 rotation of which moves the screw longitudinally. The nut 38 is made integral at its outer end with a dial or disc 39' shown of the same diameter as the magnetron body so as to be readily accessible in use for ported by alternate segments andthe other ring: connected to and supported by the intervening" alternate segments. In a sequential series within the strap space may be situated a plurality of short, parallel and electron emissive filaments or auxiliary cathodes 40. By heating these au'xiliary cathodes, electrons emitted will decrease the capacitance and tend to increase the frequency, since by well known formula,

21rvLC' where Linductance and C'capacity, it is possible by heating the cathode more or less to obtain desired adjustment of electron emission of the auxiliary cathodes and desired tuning.

Preferably, however, the emission of auxiliary cathodes 40 is grid controlled. For that purpose I show a grid 4| surrounding each auxiliary cathode. By appropriate application of voltage bias on the grids 4|, the number of electrons in the strap space may be varied and controlled.

The foregoing embodiments of the invention have structures relying upon capacitance between straps, but modification may be incorporated therein for utilizing capacity to ground. Exemplary of such modification, Figure 9 utilizes a single cylindrical strap 32b for alternate segments lfib, strapping of the other or intervening segments being effected by corresponding arrangement at the opposite end (not shown) of the anode body. A metallic sleeve 342) having plate 3% integral therewith is movable coaxially within said strap but out of contact therewith.

frequency Said plate and sleeve are operated by screwu35,

nut 38 g and dial 39 as previously described in connection with Figs. 6 and '7 and vacuum sealing is obtained by a bellows 31.

Other strappingconstructions than full cylin- V For instance, a

ders can be made tunable. prevalent form of strapping comprises arcuate echelon wires each of which connects alternate 1 segments, with successive wires in overlapping relation and with successive wires connecting different pairs of segments and constituting two series of straps. In order to introduce high capacitance in strapping of this character, I uti' lize instead of wires, as shown in Figures 10, 11 and 12, arcuate plates or sleeve sections 42 with feet 43 next their ends. Each anode segment I60 j has two holes 44, 45 in its end face, one hole 44 being closer to the axis than the other hole45.

The sleeve sections have one foot in the inner hole 44 of one segment and the other foot in the Interouter hole 45 of an alternate section. vening segments are-correspondingly strapped, thereby providing two series of overlapping straps for the alternate segments. Dielectric strap sections 46 are movable into and out of the strap spaces between sections in a rotative direction.

By greater insertion of the dielectric strap sections into the strap space, the capacitance is correspondingly increased. All of said strap sections 46 may be mounted from a ring 41 in the end space, said ring being oscillated by a lever 48 having appropriate exterior protrusion and vacuum sealing.

sulators is carried a filament or cathode 5|, which produces electrons roughly in, proportion to its temperature and which thereby changes the strap space capacitance and effects tuning. As

explained before, decrease of capacitance 'resulting from presence of the electrons in the strap space obtains increased frequency.

I claim:

1. A magnetron comprising an anode body,

having end spaces at the ends thereof and having a cathode cavity and cavity resonators extending 1 I from one end space to the other and having a cathode in said cathode cavity, said anode body providing segments between successive. cavity resonators, strap means connecting alternate segunents, said strap means providing an adjacent "strap. space, and electronic means operative in 1 said strap space for changing the capacitance in said strap space.

2. A magnetron comprising an anode body having end spaces at the ends thereof and having a cathode cavity with a cathode therein and having cavity resonators extending from one end space to the other and having segments between successive cavity resonators, straps at one end space each strap being connected to alternate segments, and electronic capacity-changing means adjacent to said straps and effective therebetween to change capacity between said straps.

3. A magnetron comprising an anode body having end spaces at the ends thereof and having a cathode cavity with a cathode therein and having cavity resonators extending from one end space to the other and having segments between successive cavity resonators, straps at one end space each strap being connected to alternate segments, and rid controlled electronic capacitychanging': means adjacent to said straps and effective. therebetween for changing the. capacity between said straps,

4. A magnetron comprising an anode body having end. spaces at the ends thereof and having a cathode cavity and cavity resonators radiating from the cathode cavity and extending from one endspace to the other and having a cathode in said cathode cavity, said anode body providing segments between successive cavity resonators, straps at one end space providing strap space between said straps and said strap space having an opening at its edge communicating with said endv space, a' gridopposite said opening, and means in proximity to said opening for supplying electrons to said strap space under control of said grid.

5. Amagnetron comprising an anode body having end spaces at the ends thereof and having an axial cavity and cavity resonators radiating from the axial cavity and extending from one end space to the other, said anode body providing segments between successive cavity resonators, straps perpendicular to the axial cavity next to one endv space and one strap joining alternate segments and the other joining the intervening segments, said straps being annular and thereby providing central openings, a grid in said openings, and a, cathode in said axial cavity and in part within said grid.

6. A magnetron comprising an anode body having an axial cavity and cavity resonators radiating from the axial cavity, said anode body providing segments between successive cavity resonators, straps extending beyond said axial cavity and each joined to different segments from the other, and cathodes disposed between said straps. for changing the capacity therebetween.

7. A magnetron comprising an anode body having an axial cavity and cavity resonators radiating from the axial cavity, said anode body providing segments between successive cavity resonators, coaxial straps extending beyond said axial cavity and each joined to different segments from the other, and cathodes disposed be- 8 and grids around said cathodes for controlling electron flow and change of capacity.

9. A magnetron comprising an anode body having an axial cavity and cavity resonators-radiating from the axial cavity, said anode body providing segments between successive cavity resonators, arcuate plate sections, one from each segment to an alternate segment therebeyond, and dielectric means adjustably insertable between successive said sections for capacity control therebetween.

10. A magnetron comprising an anodebody having an axial cavity and cavity resonators radiating from the axial cavity, said anode body 7 providing segments between successive cavity resonators, a cylindrical strap projecting from said segments coaxial with said axial cavity, and a capacity-changing sleeve insertable in said cylindrical strap, said sleeve having. a bottom wall there-across also insertable in said cylindrical strap.

11. An electron-discharge device comprising: a cathode; an anode structure, spaced from said cathode, and incorporating a cavity resonator; a pair of spaced conducting members electrically connected to points of opposite polarity on said cavity resonator; an electron-source disposed intermediate said conducting members for creating a space charge therebetween; and means adjacent said electron-source and said conducting members for establishing a magnetic field transversely of the path between said electron-source.

and said conducting members.

HOWARD L. STEELE, JR.

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

UNITED STATES PATENTS Number Name Date 2,115,521 Fritz et' al. Apr. 26, 1938 2,144,222 Hollmann Jan. 17, 1939 2,154,758 Dollenbach Apr. 18, 1939 2,241,976 Blewett et al. May 13, 1941 2,243,829 Brett et a1 June 3, 1941 2,408,235 Spencer Sept. 24, 1946 2,408,903 Biggs Oct. 8, 1946 2,409,913 Tonks Oct. 22, 1946 2,414,084 Bowen Jan. 14, 1947 2,414,085 Hartman Jan. 14, 1947 2,422,465 Bondley' June 17, 1947 FOREIGN PATENTS Number Country Date Great Britain Apr. 2, 1936

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