US1991197A - Electron discharge device - Google Patents

Description

Feb. 12, 1935.

A. H. DENZLER ELECTRON DISCHARGE DEVICE 2 Sheets-Sheet 1 Filed Jan. 7, 1932 ATTORNEY Feb. 12, 1935. A. H. DENZLER ELECTRON DISCHARGE DEVICE Filed 1952 2 dheets-$hee-t 2 FIG. 3

Wdiliuv 1 UNITED STATES' PATEN Patented Feb. 12, 1935 T" cB VEL crRoN nrsonARGE DEVICE Arthur H. Denzler, Union City, N; J., assignor to Bell Telephone Laboratories, Incorporated, New York, Y., a corporationof New York Application January 7, 1932, Serial No, 585,204 5 cmims; (01. 250-275) This invention relates to electron discharge de vices, and more particularly tosuch devices employing an equipotential, indirectly heated cathode. 1 1 1 1 1 In discharge devices employing an equipotential cathode which is: usually in the form of a metallic cylinder coated with emission material,

a heater element which may carry alternating current isprovided within the metallic cylinder to convey. the heat either by conduction or radia tion so that the cathodeattains a proper operating temperature for emissionof electrons. Usu ally the heaterelement is confined in an insulator of quartz or other. material which is interposed between the heater and the cathode cylinder.

In this type of construction, considerable time is required for-the cathode to attain a uniform and efficient temperature for the emission of electrons totheuother electrodes in the device, and in devicesof the power type the time element is almost prohibitive to warrant the productionof dis-1 charge devices employing this cathode assembly. An object of this inventionis to decreasethe time element between the application of current to theiheater and the attainment, of uniform and 1 eflicient emission ,of electrons from the cathode surface. 1 1- 1 Anotheriobject 1 of this invention relates .to the fabrication of a' cathode assembly wherebythe enclosed elements may be easily denudedof gas;

In one'embodiment of this invention; an electron discharge device comprises a plateelectrode 1 1 1 ".The cathode assembly in one aspectof the in- 1 vention comprises a central supporting rod earrying a sleeve insulating member on which a heater element is wound helicallyyand a cylindrical-metallic cathode sleeve surrounding the heater element and spaced therefromby end disc 1 members.1 The endv membersserve to space the cathode sleeve from the heater so thatradiation of heat from the heater isdirectly to the cathode sleeve which carries an outer surface. 1

port of the cathode sleeve by a leading-in wire extending fromthe stem, thelsleeve being spaced slightly from atleastoneof the disc members to form a passageway tothe interior of the cylinder.

This construction-permits the complete removal of occluded gases from the internal elements of 1 the cathode assembly during the manufacture of the device. I ,1

The invention and the features thereof. will be understoodmore clearly from the-followingde tailed description with reference to the accompanying drawings in which: 1 1. 1

Fig. l is a perspective view of an electron discharge device illustrative of one embodiment of this invention with a portion .of the enclosing vessel and-theanode broken away to show 1 the 1 innerelectrodes more clearly; 1 1 1 1 1 Fig.v 2 is a side view of oneend of the electrode assembly of the device shown in Fig. 1 showing in detail the support of the insulator from thean- 1 ode; 1 1 1 Fig, 3 is a plan View of the electrode assemblyof Fig. 2 showing the relation of theelectrodes; and Fig; 41 is an enlarged viewinwcros's-section of the cathode assembly constructedin accordance with .this. inventionand employed in the device showninFig.1. 1 1-1 Referring now to Fig 1,1 of the drawings, an

, electron discharge: deviceillustrative of one embodiment ofthis invention is shown comprising anenclosing vessel 10 which is secured to an in sulating base llgcarrying terminal prongs 12. The vessel 1011s provided with a reentrant stem 1 13 which terminates in a press 14 from which thecathode and the control electrodeor grid are supported. -A- split metallic collar or band conabout the stem 13 by a bolt l'land nut 18, respec 1 tively, onlyone of" each being shown. A plurality of upright members, such as wire rods 19 are attached to the collar and bent toward each other toprovide parallel arms 20 which embrace the extensions of a cylindrical anode; The anode may be formed of perforated sheet metal, such sisting of similar opposed arcuate portions 15 1 7 having juxtaposed-integral flanges 16 is clamped as nickel, and comprises opposed semi-cylindrical 11 sections 21 joined by integral flanges 22 which are disposed in face to face relationand are secured, as by weldin'g,'between the parallel (arms 20 of the rods 19. Theperforations in the anode prevent, the confinement of heat withi'n the 1anode,'and therebyexpedite the cooling ofthe anode during the operation of the device. As a result, thegrid of the device operates at a relatively low temperature and secondary e1ec-' tronyemission from the grid is'reduced. I The flanges 22 are preferably relatively large to in- 1 crease-the radiating surface ofthe anode andto thereby further expedite the cooling of the anode.

1The anode may also be'provided' with a black anode.

coating, such as carbon or an oxide of the metal, to increase heat radiation.

An insulating member 23, such as lavite, is a rality of relatively large apertures 28 to prevent the confinement of heat adjacent the member and:

thereby to prevent excessive heating of the insulating member. v

A plurality of rigid uprights 29, such as wire rods, are supported from rigid wires 30 embedded in the press 14, and extend within the anode 21 parallel to the longitudinal axis thereof. Thefree end of each of the uprights 29 extends through oversize bores 31 in the insulating member 23 so that the uprights may expand and contract freely along their lengths with temperature variations during the operation of the device. A helical wire control electrode or grid 32, which may be of carbonized molybdenum, is supported upon the vuprights 30 by welding theturns thereof to the uprights, and is concentrically disposed within the anode 21. A leading-in conductor 33 for the grid '32. is sealed in the press 14 and is connected to one of the terminal prongs 12 on the base.

An equipotential heater type cathode assembly, shown in detail :in Fig. 4, is disposed concentrically within the anode-21 and grid 32 and com prises a-central supporting rod 34, which may be of molybdenum, butt-weldedto a bent rigid support 35 of greaterdiameter than the rod 34 and preferably of nickel, which is secured at its free end to a wire stub 36 embedded in the pressll. An insulating .disc or block.37 which may be of magnesiumoxide known as magnesia, is seated upon the shoulder formed by the edge of the support 35, and in turn has seated thereupon an insulating sleeve 38, such as 'of magnesium oxide, which is disposed about the supporting rod 34. Another insulating disc or block 39 en circles the supporting rod 34 and rests against the end of the sleeve 38. A helically wound heater element 40-, preferably of tungsten wire,

is disposed about and in contact with the insulating sleeve 38 and extends between the insulating discs 37 and 39. An extension 41of the heater nickel, is coated with barium and strontium oxides 52 which serve as a source of electrons when heated. The cathode sleeve is disposed about the supporting rod 34, andsupported from a rigid wire stub 46 embedded in the-press by a. rigid wire link 47. The wire46 is electrically associated with one of the terminal prongs ;12 on the base by a-leading-in conductor 48 sealed in the press.

As is clearly shown in Fig. 4, the inner diameter of the sleeve 45 is slightly greater than the diameter of the insulating discs 37 and 39. .The sleeve 45 is supported longitudinally solely through the wire 47 and is spaced from the heater 40 by the discs 37 and 39. The clearance between the sleeve 45 and the discs 37- and 39 enables the removal of gases from the interior of the sleeve 45 and the denuding of the heater element 40 and insulating sleeve 38 during the evacuation treatment of the device and thereby insures a high vacuum within the enclosing vessel 10. The sleeve 45 is heated substantially by direct radiation of heat from the heater element 40 without the intermediary of an insulating body as in cathodes of this type known heretofore. This enables a very eiiicient and quick heating of the cathode sleeve 45 to the temperature necessary for uniform and efficient emission of electrons and the time element in heater type cathodes is substantially reduced.

The free end of the central rod 34 extends through a bore in the insulating member 23 and forms a sliding fit with the block, so that the rod may expand and contract freely along its length and the proper position of the cathode with repect to the grid and anode is maintained.

An annular grooved support 49 is mounted on a wire 50 carried by a metallic strip 51 secured to the collar and carries a vaporizable mate-. rial, such as magnesium. This material is vapor- .ized during the evacuation treatment of the device to fix residual gases within the enclosing vessel 10.

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

What is claimed is:

1. An electron emitter for discharge devices comprising a sleeve insulating member, a perforated disc at each end of said membena heater wire wound on saidmember, a cylindrical oathode surrounding said member and discs, and-a support extending loosely through said member and discs, said heater wire having an end portion extending through said discs, and fastened to said support to prevent movement of said member and discs in one direction, and said support including means for limiting the movement of said member and discs thereon in the opposite direction. i 1

2. An electron emitter for discharge devices comprising a metallic supporting standard having a shoulder thereon, an insulating disc seated on said shoulder, an insulating sleeve encircling said rod and seated upon said disc, another insulating disc seated upon the endof said-sleeve,

a spiral heater wire around said sleeve, said heater having end portions extending throughsa'id discs, one of said end portions being electrically connected to said standard, leading-in conductors secured to'said standard and to'the'other end portion of said heater wire, and a metallic sleeve surrounding said heater element and said discs and having an emissive coating on its outer surface. v

3. An electron emitter for discharge devices comprising a central support, an insulating member surrounding said support, a heater element on the surface of said member, spacing insulating blocks surrounding said support at the ends of said member, said heater element engaging said blocks to maintain said member and blocks in position on said support, a cathode sleeve surrounding said support, insulating member, blocks and heater element, and a longitudinal support separate from said central support and spacing blocks maintaining said cathode sleeve in position.

4. In an electron discharge device, an enclosing vessel having a stem, a metallic standard extending from said stem, an insulating sleeve on i said standard, an insulating disc at each end of said sleeve, said standard including means, supporting said sleeve and said discs, a heater wire wound on said sleeve having one end electrically connected to said standard, leading-in conductors embedded in said stem and secured to said standard and to the other end of said heater wire, a cathode sleeve encircling said insulating sleeve and said discs, and a leading-in conductor extending from said stem and supporting said metallic sleeve.

5. An electron discharge device comprising an enclosing vessel having a stem, an anode supportedfrom said stem, a push-type insulator carried by said anode, a grid within said anode andsupported by said stem and insulator, a

metallic support rod extending from said stemand seated in an aperture in said insulator, an

insulating sleeve surroundingsaid rod, insulating discs at opposite ends of said sleeve, a heater wire in conductor extending from'said stem and supporting saidcathode. 1

ARTHUR H. DENZLER.

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