US3477110A - Method of making electron discharge device cathodes - Google Patents

Method of making electron discharge device cathodes Download PDF

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Publication number
US3477110A
US3477110A US531621A US3477110DA US3477110A US 3477110 A US3477110 A US 3477110A US 531621 A US531621 A US 531621A US 3477110D A US3477110D A US 3477110DA US 3477110 A US3477110 A US 3477110A
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US
United States
Prior art keywords
wire
former
aluminate
tungsten
cathode
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US531621A
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English (en)
Inventor
Walter John Honeyball
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Teledyne UK Ltd
Original Assignee
English Electric Valve Co Ltd
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Filing date
Publication date
Application filed by English Electric Valve Co Ltd filed Critical English Electric Valve Co Ltd
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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
    • H01J1/14—Solid thermionic cathodes characterised by the material
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
    • H01J23/02—Electrodes; Magnetic control means; Screens
    • H01J23/04—Cathodes
    • H01J23/05—Cathodes having a cylindrical emissive surface, e.g. cathodes for magnetrons
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
    • H01J9/042—Manufacture, activation of the emissive part

Definitions

  • An electron discharge tube thermionic cathode is made by winding a tungsten or molybdenum wire as a helix with spaced turns on a cylindrical former having a surface of alumina. Aluminate material is melted onto the wire winding to cover it, to penetrate the spaces between the turns and to amalgamate with the alumina. Thus the winding is encased in a solid mass when cooled.
  • This invention relates to cathodes for electron discharge devicesparticularly though by no means exclusively for magnetrons-and has for its object to provide improved cathodes of the kind in which aluminate material constitutes the electron emitting substance.
  • Cathodes of this kind will hereinafter be termed aluminate cathodes.
  • Aluminate cathodes are well known and present the advantages of high thermionic emission and good robustness, being capable of withstanding considerable maltreatment.
  • Known aluminate cathodes consist essentially of a carrier body of porous tungsten or molybdenuma socalled tungsten or molybdenum sponge-which has been impregnated with aluminate material, usually aluminate of barium, strontium or calcium or a mixture of these aluminates.
  • These known aluminate cathodes have, however, the defect of being diflicult to manufacture and therefore costly, especially in the larger sizes.
  • they are necessarily indirectly heated and require the inclusion of a high temperature heater to maintain an operating cathode temperature, when in use, of about 950 C.
  • the present invention seeks to provide improved aluminate cathodes which do not present these defects.
  • a tungsten, molybdenum or tungsten-molybdenum alloy wire is wound helically on the alumina surface of a cylindrical former, and aluminate material is melted on the wire to cover it and penetrate between its turns and to amalgamate with the alumina at the surface of the former.
  • the aluminate material may be aluminate of barium, strontium or calcium or a mixture containing two or more of these aluminates.
  • a tungsten or molybdenum or tungsten-molybdenum wire is wound as a helix on a cylindrical former having a cylindrical surface of alumina, the turns of the helix being spaced a little apart, and the aluminate material is melted on to the 3,477,110 Patented Nov. 11, 1969 wire winding to penetrate the spaces between the turns thereof and encase them, or nearly so.
  • the molten aluminate amalgamates with the alumina surface of the former and, when cooled, encases or nearly encases the Wire in a solid mass.
  • the former may be a ceramic former of alumina or it may be a metal former coated with ceramic alumina.
  • a directly heated cathode is required the ends of the wire are left projecting out of the mass to serve as connections for passing heater current through the wire.
  • a heater is provided.
  • the former may be made as a sleeve with a heater winding on its inner surface.
  • a mesh of tungsten or molybdenum or tungstenmolybdenum wire and aluminate material is melted on to the mesh.
  • the wire mesh with its aluminate material carried thereby may, if desired, be sintered on to a ceramic core or former or it may be used as a cathode without such a core or 'former, depending upon the shape and size of the cathode.
  • the cathode may be directly heated by using the wire to carry heating current or an independent heater may be provided.
  • Such a heater may, if desired, operate mainly by radiation heating e.g. it could be constituted by a heating wire spaced from the cathode proper and designed to be operated at a suitably high temperature for radiation heating.
  • a cathode in accordance with this invention may be cylindrical with its thermionic emissive surface constituted by the cylindrical surface, or it could be approximately disc shaped e.g. with one face of the disc concave and constituting the thermionic emissive surface.
  • some improvement in thermionic emission can be achieved by mixing a small quantity of powdered tungsten or molybdenum or tungsten-molybdenum alloy with the aluminate material before melting it on to the carrier wire.
  • This metal powder spreads through the aluminate and by increasing the activation increases the emission.
  • the amount of added metal powder must not be so high as to increase electrical conductivity to the point at which the wire carrying the heating current is effectively shortcircuited.
  • FIGURE 1 is a sectional view of one form of a directly heated cathode made by the method of this invention
  • FIGURE 2 is a sectional view of one form of an indirectly heated cathode made by the method of this invention.
  • FIGURE 3 is a sectional view of another form of an indirectly heated cathode made by the method of this invention.
  • the cathode shown comprises a hollow former 1 made of ceramic (alumina) or of metal coated with alumina. Wound on the outside curved surface of the former is a single layer helix 2 of tungsten, molybdenum or tungsten-molybdenum alloy wire, the turns of the helix being spaced a little apart in the manner indicated. Aluminate material-barium, strontium or calcium aluminate or a mixture containing two or more of these aluminates-is then melted on to the wire helix so that it amalgamates with the alumina 1 and when cooled forms a solid mass 3 encasing the wire or (as illustrated) nearly so.
  • some tungsten molybdenum or tungsten-molybdenum powder may be added to the aluminate material before melting it on. If a directly heated cathode is required the ends of the wire may be bent out as shown at 4 to extend from the mass and serve as heating current connections. If an indirectly heated cathode is required a radiating or other heater (not shown) may be provided in manner known per se.
  • the melting on of the material 3 is preferably accomplished by an electric current but other methods of melting the said material may be adopted.
  • FIGURE 2 shows schematically a cathode generally like that of FIGURE 1 except that it is indirectly heated.
  • an alumina formerin this case in the shape of a fairly thin sleeve--with aluminate 3 encasing a carrier wire 2 wound on the former.
  • the heater is inside the former and consists of a winding 5 embedded in suitable material 6.
  • the heater connections are marked H and the cathode connection is marked C in FIGURE 2.
  • FIGURE 3 shows a further variant.
  • This cathode is shown as of the indirectly heated type and is approximately disc shaped with one face of the disc spherically concave and constituting the emissive surface.
  • 11 is an approximately disc shaped ceramic former with one face flat and the other spheriodally concave.
  • a similarly spheroidally shaped mesh 222 of tungsten, molybdenum or tungsten-molybdenum wire is provided on the concave surface of the former and aluminate substance 3 is melted on.
  • a heater winding 5 embedded in suitable material 6 is provided on the flat face of the former.
  • a method of making an electron discharge tube thermionic cathode comprising the steps of providing a cylindrical former having a cylindrical surface of alumina, winding a wire of a material selected from the group consisting of tungsten, molybdenum and tungstenmolybdenum alloy onto said former as a helix with spaced turns, melting aluminate material onto said winding so as to penetrate the spaces between the turns of said winding to blanket said winding and to amalgamate with the alumina of said former, and subsequently permitting the whole to cool to a solid mass.
  • a methodas claimed in claim 1 wherein a small quantity of powdered material selected from the group consisting of tungsten, molybdenum and tungsten-molybdenum alloy is mixed with the aluminate material before melting it on to the wire.
  • a method of making an electron discharge tube thermionic cathode comprising the steps of providing a former having a surface of alumina; applying onto said alumina surface a covering of wire material portions which are spaced a little apart and are electrically connected to one another, said wire material being selected from the group consisting of tungsten, molybdenum, and tungsten-molybdenum alloy; melting aluminate material onto said covering so that said aluminate material blankets said covering, penetrates the spaces between said wire material portions, and amalgates with said alumina surface of said former; and subsequently permitting the whole to cool to form a solid mass.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)
  • Microwave Tubes (AREA)
US531621A 1965-03-11 1966-03-03 Method of making electron discharge device cathodes Expired - Lifetime US3477110A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB10403/65A GB1129615A (en) 1965-03-11 1965-03-11 Improvements in or relating to electron discharge device cathodes

Publications (1)

Publication Number Publication Date
US3477110A true US3477110A (en) 1969-11-11

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US531621A Expired - Lifetime US3477110A (en) 1965-03-11 1966-03-03 Method of making electron discharge device cathodes

Country Status (5)

Country Link
US (1) US3477110A (enrdf_load_stackoverflow)
CH (1) CH443494A (enrdf_load_stackoverflow)
DE (1) DE1539896B1 (enrdf_load_stackoverflow)
GB (1) GB1129615A (enrdf_load_stackoverflow)
NL (1) NL6603090A (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3558966A (en) * 1967-03-01 1971-01-26 Semicon Associates Inc Directly heated dispenser cathode
EP0245982A3 (en) * 1986-05-16 1989-06-14 English Electric Valve Company Limited Directly heated cathodes
US5172030A (en) * 1988-01-20 1992-12-15 Eev Limited Magnetron
US7545089B1 (en) * 2005-03-21 2009-06-09 Calabazas Creek Research, Inc. Sintered wire cathode

Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1946603A (en) * 1929-05-09 1934-02-13 Electrons Inc Cathode for electrical discharge devices
US2175345A (en) * 1935-07-12 1939-10-10 Gen Electric Electric gaseous discharge device
US2287460A (en) * 1940-11-29 1942-06-23 Rca Corp Insulated heater and method of manufacture
US2589521A (en) * 1952-03-18 Heater
US2867032A (en) * 1950-10-27 1959-01-06 Sylvania Electric Prod Method for producing vacuum tube heater elements
US2878409A (en) * 1957-04-29 1959-03-17 Philips Corp Dispenser-type cathode and method of making
US3117249A (en) * 1960-02-16 1964-01-07 Sperry Rand Corp Embedded heater cathode
US3195004A (en) * 1960-08-19 1965-07-13 Rca Corp Cathode heater for electron discharge devices
US3201639A (en) * 1955-02-09 1965-08-17 Philips Corp Thermionic dispenser cathode
US3307241A (en) * 1963-10-14 1967-03-07 Litton Prec Products Inc Process for making cathodes

Patent Citations (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2589521A (en) * 1952-03-18 Heater
US1946603A (en) * 1929-05-09 1934-02-13 Electrons Inc Cathode for electrical discharge devices
US2175345A (en) * 1935-07-12 1939-10-10 Gen Electric Electric gaseous discharge device
US2287460A (en) * 1940-11-29 1942-06-23 Rca Corp Insulated heater and method of manufacture
US2867032A (en) * 1950-10-27 1959-01-06 Sylvania Electric Prod Method for producing vacuum tube heater elements
US3201639A (en) * 1955-02-09 1965-08-17 Philips Corp Thermionic dispenser cathode
US2878409A (en) * 1957-04-29 1959-03-17 Philips Corp Dispenser-type cathode and method of making
US3117249A (en) * 1960-02-16 1964-01-07 Sperry Rand Corp Embedded heater cathode
US3195004A (en) * 1960-08-19 1965-07-13 Rca Corp Cathode heater for electron discharge devices
US3307241A (en) * 1963-10-14 1967-03-07 Litton Prec Products Inc Process for making cathodes

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3558966A (en) * 1967-03-01 1971-01-26 Semicon Associates Inc Directly heated dispenser cathode
EP0245982A3 (en) * 1986-05-16 1989-06-14 English Electric Valve Company Limited Directly heated cathodes
US5172030A (en) * 1988-01-20 1992-12-15 Eev Limited Magnetron
US7545089B1 (en) * 2005-03-21 2009-06-09 Calabazas Creek Research, Inc. Sintered wire cathode

Also Published As

Publication number Publication date
DE1539896B1 (de) 1970-08-20
NL6603090A (enrdf_load_stackoverflow) 1966-09-12
CH443494A (fr) 1967-09-15
GB1129615A (en) 1968-10-09

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