US2000938A - Electron discharge device - Google Patents

Description

May 14, 1935. c E, FAY

ELECTRON DISCHARGE DEVICE Filed May 12, 1935 INVENTOR C. 5. FA)

A TTORNEV Patented May 14, 1935 "UN TED: STA

" "nrno'rnon DISCHARGE DEVICE virrational;

Cliiiord E. my; South Orange, N.';J.,, assignor to Bell Telephone Laboratories, Incorporated, New Kerk; N.'Y., a corporation of;New York Application May- 1-2; 1933; Serial 1%; 670,692

foclaims potato-27.5 W V 1 This invention relates toelectron' discharge de-;

vices :and more particularly to such devices adapted forthe generation of ultra-high frequency' oscillations and-commonly known in the 5- art asBarkhausen' oscillators.

3 andthereby to increase-the'powercapacity of the device; ii T 1 Another, object the operating characteristics Barkhausenoscillators. -In one embodiment of this invention, an elec -v tron dischargedevicecomprises aicylindrical electrode, a cathode and an output or'grid' elecand" efficiency of trode within-the cylindrical electrode andextendingsbeyond the ends thereon; 1 a

The cathode comprises-a linearinlamentsupported at its ends and disposed coaxiallywithin the cylindrical electrode; The output electrode comprises a pair of spaced .tubularmembers positioned, beyond the ends ofithet cylindrical electrode and a plurality' of parallel; linear wires extending between the tubular membersiand disposed in a cylindrical boundarycoaxial with-the cathode and the cylindrical electrode. v :In accordance with a feature of this invention, the parameters of the electrodesare correlated so that azrelativelyhighioperating efliciency is ob- In accordance with'another feature" of this in vention, heat radiating members are associated with output electrode in order to'dissipate the heat therefrom; In one form the members may comprise metallic discs of relatively large area; mounted on the tubular members of the output electrode assembly. y 1 p I In accordance witha iurtlierfeature of this in# vention; a plurality of imperforatetubular. memebers are mounted on the cathode, and surround the portionsthereof extending beyond the ends of the cylindrical electrode. Thesefmembers serve to confine th'e electron flow to adesired path and prevent the flow of electrons to the; tubularmembars in the output electrode assemblyQ; j y r: The invention and the, various features thereof understood more clearly and! fully from capacity of devices of this'type is lim- I w 'electrode;and"

or this inventicn'is ts improve wires :34.

' traction of the rods 20 the following detailed description with reference to the accompanying drawing in which: 1 4 Fig.1 is a perspective view of'an electron-;dis-; charge device illustrative of this-vinventiong with I portions-of the enclosmgvesseland ot'the elec-. trode structures brokenaway to show details of construction more clearly; V Fig. 2 is an enlarged end Viewof'the electrode assembly showing the relative disposition of? the g cathode and the output electrode, filament-leads 10 and-the heat radiating membersfor the output;

in cross-section showing and output electrode ras rFigL3 is a side view details of the cathode sembli'es. a y, Us

Referring? to the drawing, the device shownisi of the-type adapted for the generation-'oi"ultra'-' I high: frequency oscillationsand commonly known as a Barkhaus'en oscillator. It comprises evacuatedenclosing vessel l0 havinga reentrant "20 stem H which. terminates in a"press I2." A pair ofibentlor substantially inverted Leshap'ed wires t3 are embedded at 'one'end in the press l2 and 1 have secured thereto a pair; of parallel metallic rods or uprights l4. A single linear fi1amentl5 25. of tantalum, tungstenror' other material having good electroniemitti'ng characteristics, is secured at its ends to'the rods or uprights and serves as the cathode of "the device. 'The" heating cur-' rent for. the. cathode may be supplied through leading-in conductors .Hi connected to the 'A bent wire i1 is embedded at one end inthe press 12 and at the other endin 'an'insulating bead IS, the wire' i! being disposed; in a planeat, substantially rightfangles to the plane of the wires l3. A metallic-ribbon i9 is secured at one end to a rod Zillembedded in-the insulating bead l8, and at the other end to another rod 2l"sealed in the end of .the enclosing vessel 10' as shown at;22; The'ribbon l9 is'p'referably flexible a'nd bowed to allow longitudinal expansion and con and 2| with temperature variations.- r J 1. I A cylindrical electrode 23'ha'ving 'aflange 24 is supported from rigid L-shaped wires 25 se? curedyas by welding, to the rod 20 and .to the flange 24 and a reinforcing rod or wire 4| on the'flange. The electrode 23 may be of sheet molybdenum, the surfaces of which areroughened by carborundum blasting to increase the heat radiation therefrom, and. is disposed-about and spaced coaxially with respect :to the filement [5. l i A bent wire PATENT- 26' is embedded'at one endin the press l3 and carries an insulating bead 21. A bowed flexible metallic ribbon 28, similar to the ribbon I9 is connected between a rod 29 embedded in the insulating bead 2'! and a rod 30 sealed in the enclosing vessel It as shown at 3!. A U-shaped wire support 32 is secured to the rod 29 and is rigidly held in position by braces or rods 33 secured'thereto and .to the rod 29.

An output or grid electrode assembly is carried by the support 32 and comprises a pair of cylindrical metallic collars 34 connected to the arms of the support 32 by short rigid wires 35,

only one of which is shown in Fig. 1. The'collars 34 encircle the ends of the filament lfiand have secured thereto a plurality -01 equally spaced parallel wires 38 whichmay be of tungsten and are disposed parallel to the filament l5 and arranged in a cylindrical boundary coaxial with the filament. Y

Thisconstruction provides a substantially noninductive electrode and inasmuch as the wires 36 are symmetrical at all points with respect to the filament IS a uniform field between the filament and the wires is obtained with a resultant uniformityof electronic action. Furthermore, this construction facilitates the conduction of heat from the center portion of the wires 36 to the ends-thereof and thereby enables the dissipation ofthe heat by, radiation.

'Indevices'oi the type described, the electrode 23 is usuallyoperated at zero potential, or at a slightly negative potential with respect tothe filament l5'and the grid or output electrode is very'smallsurface area and is spaced veryrclose to the filament. For example, in a device capable of producing oscillations of a wave length of the order of ltlcentimeters', the gridor output electrode may have an inner diameter of 0.156 inch, the gridwires being'0.010 inch in diameter, and the filament may be 0.008 inch in diameter.

During the operationof the device, the grid be-; comes heated and the power output of the device is therefore limitedby the temperatures which the grid' electrode can safely withstand. In

order to increasethe power capacity of the de-,

vice, means are provided, in accordance with a feature of this invention, to dissipate the heat fram the grid electrode. Forthis purpose, a pair of vanes or annular discs 31 of relatively large,

area, and of a material having good heat'radiatingchara'cteristics, for example, molybdenum or nickel roughened by carborundum blasting, are

disposed adjacent the ends of the grid wires 36 and are thermally coupled thereto. 'The disc 31 may be disposed in contact with the collars 34 and may be connected to the collars by a plurality of bent wires 38 of good thermal conductivity. In order to insure uniform operating'charac teristics and a relatively high operating efliciency, the collars 34 are preferably disposed beyond the ends of the electrode ,23. To substantially prevent the fiow of electrons'to the collars'a'nd there by to confine the electrons emitted from the filament I5 to paths embracing the wires 36 of the output electrode, the end portions of the filament within the collars 34 may be surrounded by tubular sleeves 39 of nickel or the like, secured to the uprights I4 by tabs 40.

The efficiency of devices'of the Barkhausen oscillator type is dependent to a material extent upon the relative diameters of the grid electrode and the electrode 23." Particularly goodresults are obtained with devices in which the diameters of the electrode 23 and of the output or grid electrode are in the ratio of substantially 3.6 to 1. Variations of plus or minus 10% in this ratio, that is, the ratios being between approximately 3.2 to 1 and 4.0 to 1, have been found to be not particularly detrimental.

Although a'specific embodiment ofthis invention has been shown and described, it is to be understood, of course, that many modifications may be made therein without departing from the scope and spirit of this invention as defined in the appended claims.

What is claimed is:

1. An electrode assembly for electron discharge devices, comprising a pair of spaced metallic cylindrical members, a plurality of wires extending between and secured at their ends to said members, said wires constituting an electrode, metallic discs of relatively large area adjacent said cylindrical members, and a plurality of members of high thermal conductivity connecting said cathode, and a cylindricalelectro'de encircling said output electrode and disposed coaxially therewith, the ratio of the diameters of said second cylindrical electrode and said output electrodebeing between 3.2 to l and 4.0 to 1.

3. A Barkhausen oscillator comprising a cathode, a cylindrical output electrode encircling said cathode, and a cylindrical'electrode encircling said: output electrode and disposed coaxially therewith, the ratio of the diameters of said second cylindrical electrode and said output elec trode'being substantially 3.6 to l. V 4. A Barkhausen oscillator comprising a cathode, a cylindrical electrode encircling said cathode and disposedcoaxially therewith, and an output electrode intermediate said cathode and said cylindrical electrode including a plurality of parallel wires mounted in a boundary coaxial with said cathode, the ratio of the diameters of said cylindrical electrode and said' boundary being substantially 3.6 to 1. V

5. An electron discharge device comprising an enclosing vessel having a stem, a plurality of wires extending from said stem, a cathode mounted on said wires, a plurality of supporting members embedded in said stem at one end and anchored at the other end to said enclosing vessel at points remote from said stem, each of said supporting members having a flexible portion, an electrode carried by one of said members and encircling said cathode, and another'electrode carried by another of said members encircling said first electrode and coaxially disposed therewith.-

6. An electron discharge device comprising an enclosing vesselhaving a stem, a plurality of supports extending from said stem, a filament extending between two of said supports, a cylindrical electrode carried by another of said supports, and encircling said filament, a pair of tubular members carried by another of said supports and encircling said filament, and an electrode extending between and secured to said tubular members.

'7. A Barkhausen oscillator comprising an enclosing vessel having a stem, a cylindrical electrode supported from said stem, a linear filament disposed coaxially within said electrode and having portions extending beyond the ends thereof, sleeve members encircling said portions, a support extending from said stem, a plurality of mounted in a cylindrical boundary coaxial with said filament.

8. An electron discharge device comprising an enclosing vessel having a stem, a plurality of supports extending from said stem, a filament extending between two of said supports, a cylindrical electrode carried by another of said supports, a pair of spaced metallic cylindrical members carried by another of said supports, a plu rality of wires extending between and secured at their ends to said members; said wires constituting an electrode, and metallic vanes of relatively large area mounted'on said members.

9. A Barkhausen oscillator comprising an en,-

closing vessel havinga stem, a cylindrical elec-' trode supported from said stem, alinear filament disposed coaxially within said electrode and having portions extending beyond the, endsthereof, sleeve members encircling said portions, a support extending from said stem, a plurality of tubular members carried by said support and encircling said sleeve members, a plurality of f wires extending between and secured to said tubular members, said wires being disposed parallel to one another and to said filament and mounted in a cylindrical boundary coaxial'with said 7 filament, metallic discs of relatively large area adjacent said tubular members, and a plurality 'of members, of high thermal'conductivity con-

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