US2512620A - Electron discharge tube structure - Google Patents

Description

June 27, 1950 D. v. EDWARDS ELECTRON DISCHARGE TUBE STRUCTURE 3 Sheets-Sheet 1 Filed Aug. 15, 1948 n m w mm 8 Q v V M Nv k wmw 3 Q Q nm my! Q 2 m X n z w June 27, 1950 D. v. EDWARDS ELECTRON DISCHARGE TUBE STRUCTURE 3 Sheets-Sheet 2 Filed Aug. 15, 1948 wl n 2 all n 2 w o 2 m Q mWF M 2 M Z ZmveZtir Qttorneg June 27, 1950 D. v. EDWARDS mzcmou DISCHARGE TUBE STRUCTURE" 3 Sheets-Sheet 3 Filed Aug. 13, 1948 Fla Enventor PIC-11.11.

Patented June 27, 195

Donald V. Edwards, Montclair, N. J assignor to Electrons, Incorporated, Newark, N. J.-, a cor-' poration of Delaware Application August 13, 1948, Serial No. 44,113

This invention relates to controllable electron dischargedevices of the high vacuum triode type operating in a cross-magnetizing magnetic field.

In one type of a controllable electron discharge tube, such as disclosed for example in the prior application of D. V. Edwards and D. C. Winters, Ser. No. 768,606,- filed August 14, 1947, a plurality of filamentary cathodes and grid bars in alternate relationsare associated with the opposing planar surfaces of an anode in a cross magnetizing field to provide a tube of the triode type, conveniently termed a magnatriode, in which a range of relatively high positive potentials on the grid bars may be used to increase the space current for a given anode to cathode spacing and difference of potential, without significant or objectionable electron current to the grid bars.

The primary object of this invention is to provide a tube of this type in which the tube elements and associated parts are organized and arranged to obtain a strong magnetic field on the inter-electrode space by using anodes of magnetic material to constitute thewalls of an evacuated envelope, and in which adequate provision is made for supporting and insulating the electrodes, while permitting adequate heat dissipation and individual thermal expansion of these electrodes, and providing external connections for the control element of the tube and the heating circuit of the cathodes.

Further objects, characteristic features and attributes of the invention will be in part apparent, and in part pointed out as the description progresses.

One typical embodiment of the invention is illustrated in the accompanying drawings, in which- Fig. 1 is a general isometric view of the tube, with parts broken away.

Fig. 2 is a side view of the tube including a longitudinal vertical section through the upper half.

Fig. 3 is a longitudinal horizontal section of upper cathode supporting slide, with parts separated.

8 Claims. (Cl. 25027.5)

2 Fig. 9 is a side view of the cathode assembly. Fig. 10 is a vertical section through the oathode assembly on the line Ill-J0 of Fig. 9.

Fig. 11 is a side view of the grid bar assembly.

Fig. 12 is an end view of the grid bar assembly.

In general, the tube of this invention comprises an evacuated envelope of a general rectangular form having metallic side walls of magnetic material, which constitute the anode for the tube and also pole pieces for a permanent magnet or other equivalent source of magneto-motive-force to provide a strong magnetic field between these side walls and anode surfaces. A multi-cellular arrangement of a plurality of linear or filamentary cathodes and flat elongated grid bars, arranged alternately in parallel relation to provide a grid bar surface on the opposite side of each cathode, is disposed between the magnetic side walls of the tube envelope. The magnetic field is directed at right angles to the anode surfaces and the axes of the cathodes, and generally parallel withthe surfaces of the grid bars, so that electrons drawn from the cathodes by positivepotentials on the grid bars are directed or focused into beams or streams extending to the anode surfaces but largely, if not entirely, escap-.

ing the grid bars. The plurality of equally spaced filamentary cathodes are connected at.

their ends to upper and lower supporting elements or slides, which are resiliently supported by upper and lower metallic header bars of substantial cross-section for conduction of heat as well as heating current for the cathodes, so that an endwise pull is maintained on the cathodes when they are heated. The grid bars, one more in number than the cathodes, are supported with a yieldable or sliding connection for thermal expansion to upper and lower grid bar supports, which are attached to blocks of steatite or like heat resistant insulating material slidably supported from the upper and lower headers, so as to insulate the grid bar assembly from the oathode assembly and also permit longitudinal thermal expansion of the grid bar assembly. The bars or plates of magnetic material, constituting the side walls of the evacuated envelope, provide closely spaced opposing planar anode surfaces, between which the cathodes and grid bars are disposed; and the upper and lower headers for supporting these cathodes and grid bars are preferably located outside of the space between these anode bars or plates. Elongated metallic caps or covers and metallic pieces or blocks, brazed or soldered to the anode bars, complete the tube envelope; The end bars support the 3 upper and lower cathode and grid bar supporting header bars, with appropriate glass-to-metal seals to electrically isolate the anodes, cathodes and grid bars and afford external electrical connections for the cathode heating circuit and grid circuit.

Considering more in detail the typical tube structure illustrated, the side bars or plates A constituting the side walls of the evacuated envelope and anodes for the tube, may have the cross section of a conventional channel iron, affording the desired flat anode surfaces with projections to facilitate applying magneto-motiveforce from a permanent magnetor the like to these side bars. It is contemplated that these side bars A may be made of an iron or steel having the appropriate permeability and. electrical,

conductivity. These side bars A form the pole pieces of a closed magnetic circuit including a a suitable source of magneto-motive-force, which as shown comprises magnetized blocks 4 of a permanent magnet steel, such as Alnico, and a soft iron back-yoke. It will bev evident that the structure provides a strong magnetic field in the gap between the side bars A.

The ends of these side bars A are formed with a notch or shoulder, as indicated at 6 in Fig. 1; and end pieces or blocks 1., 8 of copper or other; suitable metal are fixed to the ends of these side bars A by a brazing. or soldering operation. Upper and lower caps or covers 9, IU- of a rectangular; cross section are brazed or soldered along their edges to the side bars A and at their ends to the end pieces 1, 8 to complete a metal en-. velope for the tube.

The cathode assembly, shown in Figs. 9 and 10, and in part in Fig. 8, comprises a plurality. of linear or filamentary cathodes C, preferably of thoriated tungsten. As shown, these cathodes C are, of a rectangular cross section disposed flatwise to the anode surfaces A and edgewise to the grid bars G, as shown in Fig. '7, so as to withstand sidewise bending in a direction parallel with the anode surfaces. due to the reaction of the'magnetic field ofv the heating current through these cathodes with the strong magnetic field in which these cathodes are disposed; The particular form of the cathodes for the tube of this invention is not material, so long as these cathodes are capable of providing the desired electron emission when heated by heating current, and have a cross section suitable for withstanding sidewise bending under the influence ofv the motor action characteristic of this type of tube.

The plurality of cathodes C are supported at their ends by supporting elements or slidesv S, which. comprise two plates M of molybdenum or like metal formed with spaced projections or teeth IS with bent ends, as best shown in Fig. .8. The ends of the cathodes C are welded between the bent'ends of these projections 1'5. These cathode slides S are connected: at intervals by flanged cross plates 16 welded thereto.

The upper and lower headers, for supporting the cathode assembly, and also the grid bar as sembly later described, are relatively heavy bars B of rectangular cross section of copper or like metal having good thermal as well as electrical conductivity. These bars B extend through larger holes in the end pieces I, 8 of the envelope, and are attached to these-end pieces by a gas tight seal permitting endwise thermal expansion of these bars. As shown, these seals areof the glass-metal type, with-the seal for one end of each header bar includinga metallic bel 4 lows or corrugated tube 25 to permit the desired expansion. Referring to Fig. 2, the fixed seal at the right-hand end of each header bar B comprises a sleeve 18 of Kovar, or similar metal adapted to make a seal with glass, which is attached to the end piece 8. A flanged collar l9 of like sealing metal is attached to the header bar B; and a glass tube 20 of the appropriate length for the voltages involved is sealed in accordance with the usual practice to the Kovar sleeve [8 and collar [9. The seal at the lefthand end of each of, the header bars B, providing for their endwise expansion, is of the similar type, including a flanged Kovar sleeve 22 and flanged collar 23, together with an attached glass tube 24; but the collar 23, instead of being directly connected to the header bar B is attached to the end of a thin metal tube 25 having crimped or corrugated walls to constitute in effect a metallic bellows, and the other end of this tube 25 is attached to a shoulder on the header rod B. It can be readily seen that this structure serves to support and insulate the header bars B from the end pieces I, 8 of the envelope, with the appropriate gas tight seals, while also allowing for endwise expansion and contraction or these header bars as their temperature'changes.

Each of the header bars B is formed with a plurality of recesses, as best shown in Fig. 2, for

receiving coiled springs 28 to engage the crossconnecting members l6 of the cathode slides S (see Figs. 2 and 8-). In other words, the upper and lower slides S, to which the cathodes C are connected as shown in Figs. 9 and 10, are pushedapart by the coil springs 28. These springs 28 are made of a suitable alloy capable of retaining its resiliency after being heated to-a temperature suitable for degassing; and the parts are proportioned so that these springs 28 exert a, substantial endwise pull uponthe cathode C after they have been heated tothe desired emit ltingt temperature and expanded lengthwise.

This endwise pull upon the cathode-C, together with the cross" section of these cathodes as previously explained, serves to maintain the desired spacing between these cathodes C and their associated grid bars G,'in spite of the motor action tending to bend these cathodes sidewise. with respect to' the grid bars; In-thisconnection, the spring pressure is applied to the cathode'sli'des as a whole; but thedimensions of the individual cathodes C are made so nearalike, and the oath-' ode slides S when heated have sufiicient" flexi bility, that the endwise pull will be distributed" equally to the individual cathodes to the desired degree.

The connection between, the header bars B and the cathodeslidess for conduction of heating current is obtained in the structurejillustrated by-fiexible clips 3! ofmolybdenumor the like. Each of these clips" ttL'four as shown, has flanges welded to the plates 14 of they cathode slidersisee Fig; 8): A slotted'end 3,} of theclip Si] is welded tothe header bar B; and a bent loopof the clip lies-in a recess in the header bar.

These clips 30 afiord the desired electrical con'-' nection for conduction of heatingv current, and

also allowendwise thermal expansion of the header bars B. It can be readily seen that heatingcurrent will flow through the cathodes C' in multiple when a suitable source of, heating cur-" rent is connected to the upper and lower header bars B. Also-,these headerbarsB serve. to conduct heat to the outside of the tube envelope;

Each of the upper and lower cathode support- 5. ing slides S is anchored at its middle to the corresponding header bar B by a'flexible bracket 32 (see Figs. 2, 3 and 5); and this bracket is fastened in a suitable manner, such as by riveted pins or screws to the header bar B, and is welded to the side plates M of the cathode slide S.

The grid bar assembly, shown in-Figs; 11 and. 12, comprises upper and lower grid supports 34, 35 formed with equally spaced transverse slots to receive the ends of the elongated flat grid bars G. In order to prevent edgewise movement of the grid bars out of the transverse slots in these supports 34, 35, a pair of strips 36 of stainless steel or the like are welded to the edges of these grid bar supports, so as to leave in effect a socket in which the associated end bar of the grid is seated. Each grid bar G is attached at one end only to one of the grid bar supports 34, 35 by a small bracket or connector 31, preferably somewhat flexible, which affords the desired electrical connection to the grid bars, while the other end of the grid bar G has a sliding fit in a socket in a grid bar support. The dimensions and clearance are selected so that each grid bar may expand lengthwise when heated. These grid bars may be formed, if desired, with a longitudinal stiffening rib (not shown), and are preferably oxidized or coated to reduce their emissivity.

The upper and lower grid bar supports 34, 35 are rigidly connected at their ends by a metal bar or strip 39 of Nichrome or like metal; and each of these bars 39 is attached in a, suitable manner, such as by the rivets shown, to bars or blocks 40 of steatite or like heat resistant insulating material. The ends of these insulating blocks 40 of the grid bar assembly have a slidable fit in grooves in the upper and lower header bars B (see Fig. 2).

To provide an external connection to the grid bar assembly a flexible strip or rod 42 is attached at one end to the grid bar assembly, as shown in Fig. 11, and extends through a seal in oneend piece I, as shown in Fig. 2. This seal comprises a Kovar sleeve 43 and a conical glass cap 44, conveniently provided with the exhaust tubulation indicated at 45, a portion of the grid lead or connector 42 passing through the glass cap 44 being of course of the appropriate material to afford the desired gas tight seal.

In assembling the parts of the tube structure illustrated, it is convenient to attach the ends of the cathodes C to the slides S, and assemble the grid bar assembly of Figs. 11 and 12, except for the lower grid bar support 35. The grid bars G may then be positioned between the cathodes C, the lower grid bar support 35 attached, and the header bars B inserted in the space in the cathode sliders S. The springs 28 may now be applied, and the cross connecting members l6 welded in place after applying the appropriate compression to these springs. This assembly of the grid bars G and cathodes C with the header bars B can then be positioned between the side bars A of the envelope, and the covers or caps 9, l0 and end pieces I, 8 applied to complete the envelope assembly. The various metallic parts are brazed or soldered together, using a silver solder or the like in accordance with recognized practice. The requisite degassing of the various metallic parts may be accomplished by baking, together with induction heating. After the degassing and exhaust procedure, the cathodes may be activated in the usual way. It is desirable to obtain thorough degassing and a high vacuum.

From the foregoing it can be readily seen that the tube structure of this invention affords a compact and efilcient multi-cellular organization affording facilities for heat dissipation and thermal expansion in a manner permitting a tube of the magnatriode type, such as'disclosed in the prior application of D. V. Edwards and D. C. Winters, Ser. No. 768,606, filed August 14, 1947, to be constructed for high power ratings.

The particular structure and arrangement of parts illustrated and described represents only one typical embodiment of the invention; and it should be understood that various adaptations, modifications and additions may be made withou departing from the invention.

What I claim is:

l. A controllable electron discharge tube for use with a source of magneto-motive-force com-' prising, a metal envelope having closely spaced side walls of magnetic material constituting opposing planar anode surfaces, a plurality of filamentary cathodes in parallel relation at equally spaced intervals midway between said anode surfaces, a plurality of elongated fiat grid bars one more in number than said cathodes disposed in parallel relation edgewise to said anode surfaces and providing a grid surface on the opposite side of each cathode, and means including headers of a substantial cross section for heat conduction supporting said cathodes and grid bars in a predetermined insulated relationship, said cathodes and grid bars being supported by said headers through yieldable connections permitting indi vidual endwise thermal expansion.

2. An electron discharge tube comprising, an anode of magnetic material having opposing planar surfaces and constituting walls of an evacuated envelope, a. plurality of filamentary cathodes between said anode surfaces and having a cross section to resist sidewise bending in a direction parallel to said surfaces, upper and lower headers of a material and cross section for conduction of heat as well as current extending through seals to the outside of the envelope, and means including coil springs supporting said cathodes at their ends by said headers and exerting an endwise pull thereon when heated.

3. An electron discharge tube comprising, a permanent magnet, an iron anode having closely spaced parallel surfaces forming the pole pieces of said magnet, a plurality of filamentary cathodes and control elements mounted alternately between said anode surfaces, metallic heat conducting headers supporting and insulating said cathodes, a supporting element for said control elements, said supporting element being supported by and insulated from said headers, said control elements having yieldable connections with said supporting elements permitting their independent endwise thermal expansion, and means including caps and end pieces attached to said anode forming a metallic evacuated envelope, said headers and a separate connector for the control elements extending through seals in said caps to the outside of the envelope.

4. An electron discharge tube comprising, a permanent magnet, an anode having closely spaced opposing parallel surfaces and forming walls of an evacuated envelope, said anode being of a magnetic material and constituting the pole pieces of said magnet to afford a strong magnetic field between said anode surfaces, and a plurality of filamentary thermionic emissive cathodes and control elements mounted alternately between said anode surfaces for providing controllable space current to said anode, said magnetic field having a. strength to focus the electrons; of such space current into: beams largely escapingsaid control elements for a range-of rel.-

atively high positive potentials thereon with.

respect to the cathodes.

5. An electron discharge tube comprising, an-

iron anode having closely spaced opposing parallel surfacesand forming Walls of an evacuated envelope, a plurality'of linear cathodes at intervals between said anode surfaces, headers supporting said cathodes at their ends and extending through. seals to'the outside of the envelope, and

anlassembly' of parallel flat grid bars one morein number than said cathodes providing a grid bar surface on the opposite side of each cathode, said grid bar assembly including heat resistant insulator elements slidably supported by said headers.

6. A high. vacuum controllable electron discharge tube. comprising, an anode of elongated fiat iron bars forming parallel'walls of an evacuated envelope, a permanent magnet contacting said bars to provide a strong magnetic field transversely thereof, means including caps and end. pieces attached to said bars forming an evacuated envelope, and a plurality of linear cathodes and control elements mounted alternately within said envelope in the space between saidbars for providing a controllable space current to said anodes, said magnetic field having a strength to direct the electrons of the space current along paths largely escaping said control element in spite of a range of relativel high positive. potentials thereon.

7. A controllable electron discharge tube comprising, an evacuated metal envelope having closely spaced parallel side walls of a magnetic material constituting anode surfaces, a multicellular assembly of linear cathodes and grid bars mounted alternately between said anode surfaces with a grid bar surface on the opposite side ofeach cathode in a plane at right angles to said anode surface, means supporting said cathodes and gridbarsinsulated from each other inv a pm:- determined space relationship, said cathodes and grid bars; having; a slidable connection with said supporting means to permit their endwise ther-- mal expansion, and means including metal-toglass seals providing separate insulated externalelectrical: connections for said grid bars and a heating. circuit: for said cathodes.

8. An electron discharge tube comprising a source of magneto-motive-force, an anode comprising a plurality of elongated iron bars with. closely spaced opposing parallel surfaces, said' bars. formingwalls of an evacuated envelope andalsoconstituting pole pieces for said source of. magneto-motive-force, a plurality of. filamentary" cathodes, means including metallic heat conducting. headers extending through seals in said envelope supporting said cathodes in parallel relation at intervals between said anode surfaces,v said means comprising yieldable connections per-- mitting individual endwise expansion ofsaid cathodes, an assembly of a plurality of grid barsv one more in number than said cathodes providingagridbar surface on the opposite side of eachcathode, and means supporting said grid bar aS- sembly by said headers but insulated from said cathodes: and anode and providing for endwiseexpansion of said: grid bars individually and also longitudinal expansion of the grid bar assembly.

DONALD V. EDWARDS.

REFERENCES CITED The following references are ofv record. in. th file of this patent:

UNITED STATES PATENTS Number Name Date 1,657,57a Hazeltine Jan. 31, 1928.- 1-,803,184 Hazeltine Apr. 28, 1931 1,980,937, Dodge, Jr Nov. 13, 1934 2,248,712. Litton July 8, 1-941

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