US2352635A - Electron discharge device - Google Patents

Description

July 4, 1944. J. c. IRWIN 2,352,635l

ELECTRQN DiscHARGE DEVICE Filed Dc. s1, 1942 ATTORNEY Patented July 4, 1.944

UNITED sTATEs PATENT OFFICE ELECTRON 2,352,635 DISCHARGE DEVICE s John C. vIrwin, Roosevelt,N. Y., asslgnorto Bell Telephone Laboratories, Incorporated,

New

York, N. Y., a corporation of New yYork v Application December 31, 1942, Serial No. 470,809

(Cl. Z50-27.5)

Claims.

This invention relates -to electron discharge devices and more particularly to such devices for the generation and amplification of ultrahigh frequency energy.

In ultra-high frequency transmission systems, of the order of 150 megacycles, thel electrodes of the discharge device are of relatively 'small dimensions in order to accelerate the electron transit time between the source and the output electrode. Such minute dimensional requirements impose various construction difculkconnected to one end of the cathode.

ties in the assembly of the electrodes to main,

tain the characteristics'of the device -sumciently stable to operate with high eiiciency at the power output or energy level required for such devices. i

When the` electrodes are individually supported in coaxial relationin an evacuated containing vessel by their respective leading-in c onductors, certain electrodes, particularly the cathode and control electrode,V and especially the cathode, if it is in lamentary form, are easily distorted 'by temperature strains or mechanical stresses whereby 'the uniform spacial inter-relation of the electrodes, which controls thestable characteristics in the operation of the device, is temporarily altered or permanently changed to such an extent that the efficiency and usefulness of the device in the designated system is materially affected.

An object of this'nvention is to L stabilize the electrical characteristics jof an electron discharge` device intended for operation in thev ultra-high frequency range. Another object of the invention is to insure coaxial relation between the small dimensional electrodes of the device without reducing the Y output elciency thereof. A further object of the invention is to maintain constant linearity in the relation-ofthe cathode or lament with respect to other co7-V operating electrodes.

The invention is applicable to electron discharge devices which include a plurality of small diameter electrodes in coaxial relation, the electrodes being supported from Aa base 'of an enclosing vessel by distributed conductors extending thereinparailel to the electrodes. 'I'he electrodes generallycomprise a central linear lamentary cathode :surroundedby the cage. control electrode or grid which is enclosed by an output electr'ode or anode, the adjacent electrodes vbeing inY close proximity in ordertol diminish the electron transit -tinife and the di mensional conguration being such as .to pro? ing electrodes while permitting the spring to normally compensate for difference in temperature conditions imposed on the cathode.

'A feature of the invention relates to the additional alignment of the control electrode with respect to the cathode and anode. The spacer member is provided with a guiding opening in which one end of the grid cage is situated where- .by the grid is maintained in constant uniform relation to the other electrodes and the grid is free from distortion due to excessive temperature changes. l.

A further feature ofthe invention pertains to 'the shielding effect produced bythe slot between the integral upright guides when sputtered conducting material is deposited on the spacer member. Since the spacer member is solely in contact with the control electrode any deposit formed on the surface thereof will not create a leakagepath to an adjacent electrode because such other electrodes are isolated therefrom.

The tension spring of the filamentary cathode is laterally free from the surfaces in the slot and since these surfaces are not exposed to the sputtered material, a leakage path rcannot extend to the cathode.

Another feature of the invention relates tothe offset -support of 'the spacer member to further reduce leakage loss and thereby increase the eiciency of operation ofthe device. The insulating member is attached to an upright support which is connected solely 'to the cage grid and the point of engagement is offset from the grid 'opening and the guiding projections for the tension spring. This construction facilitates the location of the electrodes with respect to their supporting conductors in the device and the relation of the insulating spacer with" respect to the electrodes vand the filament tensioning spring without endangering the high'resistance paths between the.. various electrodes;

These and other features of the invention will be more clearly ascertained from the "following detailed description when considered with the accompanying drawing.

Fig. 1 illustrates in perspective a device made according to this invention with the enclosing vessel broken away to show the internal assembly of the electrodes;

Fig. 2 is a view, in elevation, of the device of Fig. 1 with the vessel shown in cross section and portions of the conductors brgken away to illustrate the connection of the lament to the supports at opposite ends; g

Fig. 3 is a top plan view of the coaxial electrodes, on an enlarged scale, with the spacing insulator shown in phantom relation to the electrodes;

Fig. 4 shows the insulating spacer of' this invention in an enlarged perspective view and the portions of the other elements in the device cooperating therewith;

Fig. 5 is a partial view of the spacer inrear elevation to illustrate the relation of the; tensioned spring in the guiding slot of the spacer; and

. Fig. 6 isa plan view of a portion of the inside of the base of the device of this invention taken along the line 6-6 of Fig. 2 showing the position of conductors in the base.

Referring to the drawing and particularly tov Fig. 1, the ultra-high frequency discharge device. of this invention comprises a hollow vitreous container of the hard glass type, such as borosilicate glass, Awhich forms a highly evacuated receptacle for the various electrodes enclosed therein. This vessel is formed of a molded dish stem In sealed.

preferably of tungsten, is sealed in an axial position of the stem, another conductor I4 is offset with respect to conductor I3 but in the same plane thereof and a pair of conductors l5 and I6 are sealed in parallel relation on the opposite side of conductor I3 and disposed in a transverse plane on opposite sides of the plane extending through conductors I3 and I4. A short filamentary cathode I1 is mounted parallel to the axis of the device and substantially coincident with the bisecting point of the planes of the conductors I3 to I5v inclusive, and is held -in rigid position at the lower end by welding to the end of a radial Wire arm I8, which is iixed in one end of a strap bracket I9 which has the other end 20 embracing the'einner end of conductor I3;v The op.- posite end of the lamentary cathode I1 is held under tension by a cantilever spring 2|, of molybdenum wire, secured to an extension 22 projecting on the inner end oficonductor I4. The cathode -I1 serves as the electron source of the triode and is preferably formed of tungsten or thoriated tungsten to withstand the high temperatures incident to the operation'of the device and to supply a copious flow of electrons for the discharge path to the output electrode. Furthermore, the cathode is of relatively small dimensions to decrease the spaced relation with the other cooperating electrodes of the triode and to provide a structure of minute dimensions to produce energy radiation in the microwave range.

The cathode is surrounded by a.A coaxial control electrode or grid formed of a plurality of parallel molybdenum wires 23 secured in a circular Iboundy 'fof conductor] 5 as shown at 28 in Fig. 3. The

cductor I5 is also provided with a smaller diameter extension rod or support 29 which carries at its upper end a rectangular insulating block or spacer member 30, the block being provided with a circular opening to form a guiding sleeve or seat for the collar 24 of the grid. The block is securely held on the extension 29 by a strap wire 3,I extending through the block and being welded to the extension on oppositesides of the block. The control electrode or cage grid surrounding the filamentary cathode is coaxially mounted with respect to the cathode yetis permitted to expand and contract due to temperature changes by reason of the sliding support of the grid at the top of the assemb1y.-This construction materially improves the operation of the device since thegrd, which is necessarily a frail structure, is prevented from being distorted by mechanical` stresses or .temperature changes.

The aforementioned coaxial electrodes are surprovide radiating fins for dissipating the heat energy generated `in the device. The outer surface of the arcuate portions 32 and the ns 33 may be roughened, by Sandblasting, to increase the heat radiation of the anode. A pair of the tangential plates extending from the anode in line with the conductor I6 are shortened and provided With a tubular socket 34 through which extends a rod 35 which is welded to the top of thesocket and at the lower end is rigidly fixed in the inner end of conductor I6. A getter mounting 36 may be attached to the upper end of the extension 22 on conductor I4, to facilitate the maintenance of a high vacuum in the vessel after the` completion of the exhaust of the vessel throughthe tip I2. The construction of the individually supported electrodes and the distribution of the short conductors in the stem provide high leakage resistance between the cooperating electrodes and their leading-inconductors which contribute to the trouble-free operation of the device in ultra-high frequency systems with low loss of energy output due to spurious leakage paths within the device.

In order to proportion the electrode dimensions tooperate with eiliciency in microwave systems cordingly there is greatdanger of the shorting of thefilament against the grid. With a l/-inch y diameter anode, as set forth in the typical example, the grid has an inside diameter of 50 mils or .050 inch and the lamentary cathode has a diameter of 8.5 mils or .0085 inch. The space rewith respect to the grid, due to the elongation thereof .under varying temperature conditions which is generally compensated by the cantilever spring 2l which maintains the cathode under uni- .formtension. However, mechanical and temperature stresses in the spring cause lateral displacement of the spring and therefore changes the axial position of the cathode with respect to the cooperating electrodes. This diillculty is overcome, in accordance with this invention, by the provision of limit projections or posts von the insulating block 30 to prevent lateral movement of the spring 2l and thereby insure axial symmetry oi' the cathode with respect to the cooperating electrodes.

These limits posts are formed as integral projections 31 and 38 which extend upright from the edge f the insulating plate 30 in parallel relation on opposite sides of the spring 2| and interme- 'diate the ends `thereof between the cathode I l and the support 22. The integral posts form a guiding slot 39 in which the spring 2| is freely movable in a vertical direction since the spring diameter is .025 inch and the slot width is .0 28 inch. However, the spring is considerably limited in lateral movement and consequently the viliamentary cathode I1 is accurately ymaintained in axial position with respect to the cooperating electrodes. This construction insures constant linearity of the cathode with respect to the grid thereby maintaining the electrical constants of the device more uniform to produce higher emciencies in the power output.

While the invention has been described in con` nection with a particular embodiment of the fea.- tures disclosed in the device, it is, of course, understood that various modiilcations may be made in the detail assembly without departing from the scope of the invention as defined in the appended claims. y

What is claimed is:

1. -An electron discharge device comprising an enclosing vessel containing a plurality of electrodes including a linear i'ilamentary cathode, conductors in said vessel connected to one end of the respective electrodes, a conductor and a tenconductors in said vessel connected to one end of the respective electrodes, a conductor anda ten-r sion spring attached thereto connected to the other end of said cathode to support said cathode linearly with respect to said other electrodes; and an insulating support on the opposite end of another of said electrodes, said support having guiding means restricting lateral vmovement of said'sprlngwhereby the linearity of said cathode is maintained constant.

3. lAn electron discharge device comprising anA enclosing vessel containing a plurality of electrodes including a linear lamentary cathode, conductors in said vessel connected to one end of the respective electrodes, a conductor and a cantiliver spring attached thereto connected to the other end of said cathode to support said cathode linearly with respect to said other electrodes, an insulating support on 'the opposite end of another of said electrodes, and posts extending from said .support forming a gindewayfor said spring to restrict lateral movement thereof.'4 l

4. An electron discharge device comprising an enclosing vessel containing a plurality of `electrodes including a linear iilamentary cathode, conductors in said vessel connected to on'e end of the respective electrodes, a conductor and a cantilever tension spring attached thereto con` nected to the other end of said 'cathode to support said cathode linearly with respect to said other electrodes, and an insulating support on the opposite end lof another of said electrodes, said support having integral projections in close parallel relation forming e slot for said spring, said spring being freely movable in said slot in a direction coincident withthe tension applied thereto. l

5. An electron discharge device comprising an enclosing vessel containing a plurality o f electrodes including a linear filamentary cathode,

n conductors in said vessel connected to one end of the respective electrodes, a conductor and acantilever tension spring attached thereto con- A vnected to the other end of said cathode for supporting said cathode linearly with respect to said other electrodes, and an insulating spacer member on the 'opposite end of another of said electrodes, said member having integral projections I inl close parallel relation forming a slot for said spring, said slot having, a width slightly greater than the diameter of said spring.

6. An electron discharge device comprising an enclosing vessel containing a plurality of-electrodes including a linear illamentary cathode, conductors in said vessel connected to one end 0i' the respective electrodes, a conductor and a cantilever tension spring attached thereto connected to the other end of said cathode to sup-v port said cathode linearly with respect to said other electrodes, said spring extending in a direction toward the electrodes at an angle to the axis thereof, x an insulating spacer member on the opposite end of another of said electrodes, and integral projections on said spacer member' mounted `on opposite sides of said spring intermediate said cathode and said conductor sup-` porting said spring. y

7. An electron discharge ydevice comprising a vessel enclosing a plurality of'electrodes including a lament and a grid surrounding said filament, an insulating spacer member having an opening embracing one end of said grid, a, cantilever tension spring attached to said illament and V extending outwardly adjacent one side of said spacer member, and limiting means on said spacer member positioned on opposite sides of said tension spring and intermediate the ends' thereof to prevent lateral displacement of said spring with respect to the axial line of said grid.

8; An electron discharge device comprising an enclosing vessel containing a plurality of electrodes including a filamentary cathode and a cylindrical grid 'surrounding said cathode, collar members on opposite ends of said grid, a supporting conductor parallel to said grid, an insulating spacer carried by said supporting conductor and engaging. one of said end collars, and a strap connector extending between said conductor andthe collar member on the opposite end of said grid. 9. An electron discharge device comprisinga vessel enclosing a plurality of electrodes including a. lamentary cathode and .a .cylindrical grid surrounding said cathode, said ,grid having co1 lars on opposite ends thereof, a supporting oon- `ductor parallel to said grid, an .insulator member having an opening forming an annular seat for a collar` on oneend .of said grid, and a metallic connector having a portion attached to the side of said conductor and :a portion attached to the rim of said other collar on said grid, the connector being bent at right angles intermediate said portions.

10. An electron discharge device comprising an enclosing vessel, a linear lamentary cathode mounted therein parallel to the axis of said vessel, a cylindrical grid surrounding said cathode `and uniformly spaced therefrom, a cylindrical Kanode surrounding said grid, conductors in said vessel connected to one end of the respective electrodes, a conductor and a cantilever tension lspring attached thereto connected to the other vend of said cathode to support said cathode linearly with respect to said other electrodes, an insulating spacer plate having an opening engaging the opposite end lof .said grid and being supported by the grid conductor, a metallic strap extending between .-said grid conductor and the opposite zend of .said grid, :ad integral uupright posts on said plate forming a guiding slot for said spring, said posts being mounted on one edge of said plate in line with the projection of said cantilever spring.

JOHN C. IRWIN.

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