US3449616A - Tubular mesh cathode for high-power electronic tubes - Google Patents

Tubular mesh cathode for high-power electronic tubes Download PDF

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Publication number
US3449616A
US3449616A US562608A US3449616DA US3449616A US 3449616 A US3449616 A US 3449616A US 562608 A US562608 A US 562608A US 3449616D A US3449616D A US 3449616DA US 3449616 A US3449616 A US 3449616A
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Prior art keywords
cathode
plates
tubular
plate
portions
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US562608A
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English (en)
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Jean M Sarrois
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Compagnie Francaise Thomson Houston SA
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Compagnie Francaise Thomson Houston SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/15—Cathodes heated directly by an electric current
    • H01J1/18—Supports; Vibration-damping arrangements

Definitions

  • a cathode for high-power electronic tubes includes a plurality of tubular wire mesh portions, the axial length of each portion being shorter than their respective diameters. The ends of the mesh portions are xed to the edge of circular plates so that sagging and other undesired deformations of the cathode when the tube is hot are substantially eliminated.
  • the present invention relates to improvements in lamentary or directly heated cathodes, and in particular to cathodes of this type intended to operate in high-power electronic tubes.
  • Filamentary cathodes for high-power electronic tubes often have the appearance of a tubular cage constituted by a mesh of tungsten wires stretched between two circular plates, the ends of these wires being soldered or Welded to the periphery of the plates.
  • the wires are distributed in two layers wihch are respectively inclined in opposite directions with respect to a generating line of the cylinder so as to form a lmesh (mesh cathode).
  • This type of cathode has practically no radial deformation when hot, if certain conditions are complied with, and in particular if the angle of inclination of the helical wires is greater than 60 with respect to a generating line, and if one takes the precaution of soldering or welding the wires together at the points where they intersect.
  • the height of the cathode is relatively large and, at operational temperatures, the tungsten Wires sag under their own weight so that the base of the cathode becomes enlarged while its upper part narrows.
  • the grid becomes locally overloaded and this may lead to its destruction.
  • the present invention provides a llamentary cathode for electronic tubes in which the emissive part is constituted by a tubular structure made of a mesh of metallic wires attached to the edge of circular plates, said mesh resulting from helical Winding of the wires in opposite direction of two layers of wires.
  • the emissive part of the cathode comprises at least two portions of metal wire mesh tube in alignment on a common axis, and the ends of each portion are respectively fixed to the edge of two circular plates which are spaced axially by a distance smaller than their diameter.
  • the cathode is constituted of a plurality of superposed portions of metal mesh tube, having their ends attached to rigid plates. Under these conditions, each portion acts as an elementary emissive part, and it does not undergo any harmful notable deformation under the etfect of heat, because its height is smaller than its diameter.
  • deformation is as small as possible, it is recommended to observe the abovementioned directions and in particular to construct the metal mesh tube with layers of wires which are inclined respectively in opposite directions at more than 60 with respect to a generatix of the tube.
  • the cathode according to the present invention may take various forms.
  • the e-missive part of the cathode may be constituted by an uninterrupted tubular body composed of a mesh of metallic wires.
  • the emissive part of the cathode is iixed on the one hand to plates arranged at its ends (and plates) and on the other hand to plates arranged in its tubular space (intermediate plates) at axial distances which are shorter than the diameter of the tube. Each intermediate plate is then a common support for two adjacent portions of the cathode.
  • the emissive part of the cathode may comprise a plurality of sections of metal wire mesh tube.
  • two adjacent sections may be connected to a common intermediate plate but they may also be respectively connected to two separate intermediate plates.
  • the two separate intermediate plates are in the form of flat-bottomed dishes and they are connected by their dished portions.
  • the edges of the dishes are slightly separated and delimit a zone which, during the opeartion of the cathode, remains relatively cold and supplies no electronic emission.
  • an electronic tube containing such a cathode it is then possible to reinforce the control by rigid rings ensuring the cylindrical shape of this electrode which is fragile. These rings are placed opposite the intermediate plates and consequently they are not directly subjected to the electron bombardment of the cathode, nor to its thermal radiation. They are relatively cold and ensure, by conduc-tion, the cooling of the grid wires.
  • the elementary portions of the cathode may be fed in series or in parallel.
  • the plates are supported by current input conductors which may be constituted either by rigid rods, or by a system of coaxial conductors.
  • current input conductors which may be constituted either by rigid rods, or by a system of coaxial conductors.
  • FIGURES 1, 2 and 3 are sectional views illustrating respectively three different embodiments of a cathode according to the present invention.
  • FIGURE 1 shows a cathode according to the present invention comprising an emissive element 1, formed Jby three portions such as 30 connected in series by the structural elements.
  • the emissive element 1 which is tubular in shape and has the appearance of a mesh, is produced by two thoriated tungsten wires wound helically in opposite directions, with an inclination greater than 60 on either side o'f a generatrix (t-wo layers of thoriated tungsten Wires). lAt its ends, the emission element 1 is closed by circular end plates 2, 3, made of molybdenum.
  • Two other intermediate circular plates 4, 5, also made of molybdenum, are located in the tubular space of the emissive element 1, so that the distance between any adjacent two plates is smaller than their diameter.
  • the plates 2 to S are connected to support rods arranged in the longitudinal direction of the cathode.
  • the support rods are divided up into a rst group of two rods 6, and a second group of two rods 7.
  • a terminal part (not shown in the figure) of the two groups of rods is rigidly fixed to the electrode supporting stem of an electron tube (not shown).
  • the rods 6 are xed to the plate 2 at the upper end (in the gure) of the cathode, whilst the rods 7 are Xed to the lower plate 3.
  • the rods 6 successively pass through the intermediate plates 4, and the lower plate 3.
  • the rods 6 are electrically insulated from these plates by discs 8, made of ceramic material, sealed to the plates.
  • the intermediate plates 4, 5 are rigidly attached to the rods ⁇ 6 ⁇ by means of nuts 9 gripping the insulating discs 8.
  • a cathode which comprises three portions, delimited by the four circular plates 2 to 5.
  • each portion is of a .height smaller than its diameter, and this ensures that the wires constituting the emissive element of the cathode will not undergo, when they are hot, any substantial sagging action, which is harmful to the good retention of a cylindrical form of the cathode.
  • the three portions of cathode are fed in series by means of rods ⁇ 6 and 7 serving as current input conductors.
  • FIGURE 2 shows another embodiment according to which two cathode portions 31 and 32 are separated by a double plate 10- constituted by twoelementary plates 10a and 10b, each in the form of a ⁇ flat-bottomed dish, which are joined, for example riveted, as shown, at their dished portions so that the periphery of the double plate 10 comprises two separated rims.
  • the emissive part of the cathode is formed by two tubular sections 11 and 12 of metal wire mesh. The ends of the tubular meshed portion 11 are attached to the periphery of an upper plate 13 and to the upper rim of the plate 10, whilst the ends of the section 12 are attached to the periphery of a lower plate 14 and to the lower rim of the plate 10.
  • the plates 10, 13, 14 are supported by coaxial tubular columns 17, 18, 19 respectively, serving both as support means and as current input conductors.
  • the coaxial columns 17, 18, 19 are connected to the electrode supporting stem of an electronic tube having a metal-ceramic envelope comprising connecting rings 20, 21, 22, 2.3 sealed to ceramic spacer cylinders such as 27.
  • the two cathode portions 11 and 12 have their ends connected to current input conductors; consequently, it is possible to feed them either in series or in parallel as desired.
  • the tubular column 17 supporting the double plate 10 is pierced by perforations 24.
  • perforations 24 permit more rapid cooling by radiation of the central column 18, after the cathode is turned off.
  • the tungsten wires having a very low thermal inertia, are very quick to cool, and may be subjected to stretching if the columns 17 and 18 were still at high temperature and thus heat expanded.
  • the perforations 24 vmade in the column 17 permit the thermal radiation of the column 18 to be effected towards the outside.
  • An annular insulator 26 is placed between the columns 17 and 18 above the perforations 24 to limit the deformations which could result from transverse shocks which are produced in the course of handling of the electronic tube containing such a cathode.
  • the cathode is shown surrounded by a control grid 16.
  • a zone 15 between the peripheral rims of the plate 10 remains relatively cold during the opeartion of the cathode and consequently is not subject to electronic emission.
  • This ring is not directly subjected to electron bombardment or by the thermal radiation of the cathode. It thus also remains relatively cold and ensures a cooling of the grid w1res.
  • FIGURE 3 illustrates a modication of the cathode shown in FIGURE 2.
  • the plates 10, 13, 14 are supported by two coaxial tubular columns 26, 27 whose lower ends (not shown in the figure) are connected to an electrode supporting stem of an electronic tube (not shown).
  • the upper end of the internal column 26 is connected to the plate 10, whilst the upper end of the external column 27 is connected to the plate 14.
  • the plate 13 is rigidly connected to the plate 14 by means of three rods such as 28, fixed at three points which are angularly equidistant about the plates 13 and 14, and traversing the plate 10 through insulating holes 29.
  • the two portions of cathode 11 and 12 are connected in parallel by the support structure, the columns 26, 27 constituting the two conductors necessary for supplying the current.
  • a cathode for electronic tubes comprising:
  • a generally tubular structure consisting of a plurality of separate tubular metal wire mesh portions mounted in axial alignment, the axial lengths of each of said tubular mesh portions being shorter than their respective diameters;
  • At leastA one substantially circular intermediate plate located in axial alignment with said tubular mesh portions and mounted between said rst land second end plates, said intermediate plate being attached to an intermediate end of at least one of said tubular mesh portions forming said structure.
  • Cathode according to claim 1 comprising a plurality of substantially circular intermediate plates and wherein the adjacent ends of two adjacent tubular mesh portions are connected to separate adjacent plates.
  • Cathode according to claim 1 further comprising a plurality of tubular columns supporting the plates, said tubular columns forming a system of coaxial conductors.
  • Cathode according to claim 3 further comprising a base coaxial with said system of coaxial conductors to support said system of coaxial conductors, said base forming the stem of a metal-ceramic tube.
  • Cathode according to claim 1 including rigid rods supporting said plates and constituting current conductors.
  • Cathode according to claim 5 in combination with a grid in an electron tube, wherein the control grid sur- 736,542 rounds the cathode and comprises, in the zone of the 5 987,461 plates, at least one rigid ring to improve the cooling of 1229220 the grid wires.

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  • Solid Thermionic Cathode (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
US562608A 1965-07-20 1966-07-05 Tubular mesh cathode for high-power electronic tubes Expired - Lifetime US3449616A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR25295A FR1455956A (fr) 1965-07-20 1965-07-20 Perfectionnements aux cathodes à chauffage direct

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US3449616A true US3449616A (en) 1969-06-10

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US (1) US3449616A (fr)
CH (1) CH443495A (fr)
FR (1) FR1455956A (fr)
GB (1) GB1136139A (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3560791A (en) * 1967-09-08 1971-02-02 Siemens Ag Mesh cathode for electron tubes
US3737711A (en) * 1968-11-21 1973-06-05 Varian Associates Electron tube having an improved filamentary cathode and support therefor and method of making same
DE2247364A1 (de) * 1972-09-06 1974-03-14 Bbc Brown Boveri & Cie Maschenkathode fuer elektronenroehren
US3943398A (en) * 1973-12-21 1976-03-09 Thomson-Csf Electronic tube with cylindrical electrodes
US3976909A (en) * 1975-07-11 1976-08-24 Rca Corporation Wire mesh cathode
US4443735A (en) * 1980-02-05 1984-04-17 Alexandrov Vladimir N Directly heated meshed cathode for electronic tubes and method of making
EP0637047A1 (fr) * 1993-07-27 1995-02-01 Thomson Tubes Electroniques Cathode à déclenchement et coupure rapides du chauffage et tube électronique à grille comportant une telle cathode

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0101108B1 (fr) * 1982-07-27 1987-01-21 BBC Aktiengesellschaft Brown, Boveri & Cie. Tube électronique, en particulier tube émetteur

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2456649A (en) * 1943-06-12 1948-12-21 Glenn F Rouse Cathode
GB653707A (en) * 1947-08-15 1951-05-23 Philips Nv Improvements in or relating to electric discharge tubes comprising an indirectly heated cathode
GB736542A (en) * 1952-03-28 1955-09-07 Edison Swan Electric Co Ltd Improvements relating to thermionic cathodes
US2882436A (en) * 1955-04-02 1959-04-14 Philips Corp Electric discharge tube and cathode therefor
FR1229220A (fr) * 1958-07-01 1960-09-05 Siemens Ag Cathode pour tubes électroniques
US3172002A (en) * 1960-11-21 1965-03-02 Rca Corp Cathode mount and method of fabrication
GB987461A (en) * 1962-05-31 1965-03-31 Standard Telephones Cables Ltd Thermionic valves

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2456649A (en) * 1943-06-12 1948-12-21 Glenn F Rouse Cathode
GB653707A (en) * 1947-08-15 1951-05-23 Philips Nv Improvements in or relating to electric discharge tubes comprising an indirectly heated cathode
GB736542A (en) * 1952-03-28 1955-09-07 Edison Swan Electric Co Ltd Improvements relating to thermionic cathodes
US2882436A (en) * 1955-04-02 1959-04-14 Philips Corp Electric discharge tube and cathode therefor
FR1229220A (fr) * 1958-07-01 1960-09-05 Siemens Ag Cathode pour tubes électroniques
US3172002A (en) * 1960-11-21 1965-03-02 Rca Corp Cathode mount and method of fabrication
GB987461A (en) * 1962-05-31 1965-03-31 Standard Telephones Cables Ltd Thermionic valves

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3560791A (en) * 1967-09-08 1971-02-02 Siemens Ag Mesh cathode for electron tubes
US3737711A (en) * 1968-11-21 1973-06-05 Varian Associates Electron tube having an improved filamentary cathode and support therefor and method of making same
DE2247364A1 (de) * 1972-09-06 1974-03-14 Bbc Brown Boveri & Cie Maschenkathode fuer elektronenroehren
US3875445A (en) * 1972-09-06 1975-04-01 Bbc Brown Boveri & Cie Meshed cathode for electron tubes of the grid-controlled type
US3943398A (en) * 1973-12-21 1976-03-09 Thomson-Csf Electronic tube with cylindrical electrodes
US3976909A (en) * 1975-07-11 1976-08-24 Rca Corporation Wire mesh cathode
US4443735A (en) * 1980-02-05 1984-04-17 Alexandrov Vladimir N Directly heated meshed cathode for electronic tubes and method of making
EP0637047A1 (fr) * 1993-07-27 1995-02-01 Thomson Tubes Electroniques Cathode à déclenchement et coupure rapides du chauffage et tube électronique à grille comportant une telle cathode
FR2708379A1 (fr) * 1993-07-27 1995-02-03 Thomson Tubes Electroniques Cathode à enclenchement et coupure rapides du chauffage et tube électronique à grille comportant une telle cathode.
US5666018A (en) * 1993-07-27 1997-09-09 Thomson Tubes Electroniques Cathode with fast heat switch-on and switch-off mechanism and grid-type electron tube including such a cathode

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Publication number Publication date
GB1136139A (en) 1968-12-11
CH443495A (fr) 1967-09-15
FR1455956A (fr) 1966-05-20

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