US3574910A - Method of manufacturing an indirectly heated disclike cathode and cathode manufactured by said method - Google Patents

Method of manufacturing an indirectly heated disclike cathode and cathode manufactured by said method Download PDF

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Publication number
US3574910A
US3574910A US695410A US3574910DA US3574910A US 3574910 A US3574910 A US 3574910A US 695410 A US695410 A US 695410A US 3574910D A US3574910D A US 3574910DA US 3574910 A US3574910 A US 3574910A
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United States
Prior art keywords
support
holder
cathode
metal powder
heating element
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Expired - Lifetime
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US695410A
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English (en)
Inventor
Adrianus Kuiper
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US Philips Corp
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US Philips Corp
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    • 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

Definitions

  • the invention relates to a method of manufacturing an indirectly heated disclike cathode consisting of a support for the emitting material which is secured to a metal holder containing the heating element, the space between the heating element and the support being filled with a sintered metal powder.
  • the invention furthermore relates to a cathode manufactured by the said method.
  • the heat transfer between the heating element and the support for the emitting layer of a cathode can be improved when the space between the heating element and the support is entirely filled with sintered metal powder, for example, nickel powder.
  • sintered metal powder for example, nickel powder.
  • a drawback of the known constructions is, however, that as a result of the difference in coefficients of expansion of the various components the sintered metal powder easily works loose from the surface of the support and/or from the surface of the heating element.
  • a heating element is to be understood to mean in this connection a filament which is coated with insulating material, generally aluminum oxide.
  • Another drawback is that the heat content of the cathode is considerably increased by the comparatively large quantity of metal powder, which causes a prolongation of the heating up time.
  • the working loose of the metal powder causes ungovemable changes in the distribution of the cathode temperature and/or local overheating of the heating element. It is known to avoid this by making the sintered metal layer porous and somewhat flexible by using a mixture of coarse granular powder of, for example, nickel and a small quantity of fine grains of a different metal, for example, molybdenum or palladium. By heating above the alloying temperature of the metals the fine granular metal connects the coarse grains locally so that a porous mass is obtained. Although as a result of this the working loose of the metal powder can be avoided, the drawback remains of the increase of the heat mass while the method is complicated.
  • the holder for the heating element is formed like a cap the end face of which comprises an aperture, which holder is welded against the support with its end face in such a manner that as a result of the pressure and the local heating during welding, a gap having a wedgelike cross section is formed between the inwardly directed edge of the end face and the support, after which the heating element which is dipped in a suspension of a suitable metal powder, is provided in the holder and the metal powder is released, for example, by dipping the support with the holder in a solvent for the suspension medium of the metal powder, so that it flows into the space between the support and the heating element and into the gap and fills it after which the solvent and the suspension medium are removed by heating and the metal powder is sintered after which the support is provided with emitting material.
  • the lower side of the holder is preferably closed by means of a cover. This cover preferably consists of metal and may be formed integral with the holder. Alternatively, a
  • FIG. 1 is a perspective view of support and a holder prior to welding
  • FIG. 2 is a cross-sectional view during welding of the holder to the support
  • FIG. 3 shows the holder and the heating element prior to assembling
  • FIG. 4 is a cross-sectional view of a cathode according to the invention.
  • reference numeral 1 denotes the support for the emitting material
  • 2 denotes the holder for the heating element 8.
  • the end face 3 of the holder 2 comprise an aperture 4.
  • a cover 5 is formed integral with the holder 2 as well as the connection strips 14,
  • the holder 2 is forced against the support 1 with the edge of its end face (FIG. 2) by means separate welds may alternatively be used.
  • the edge 3 bends inwardly so that a gap 12 which in this case is annular and has a wedgelike cross section is formed within the edge 3 and the support 1.
  • the heating element 8 consisting of a tungsten filament 10 which is embedded in aluminum oxide, is dipped in a suspension consisting of nickel powder and a binder, for example, nitrocellulose, so that a layer 9 of this suspension covers the heating element 8.
  • the heating element 8, after drying of the layer 9, is forced into the holder 2, the cover 5 is closed and the assembly is dipped in a solvent of the said binder, for example, acetone.
  • the binder dissolves and the metal powder flows into the cavity between the element 8, the support I and the holder 2 fills the wedgelike gap 12.
  • the metal powder is then sintered, during which the binder burns away.
  • the sintered metal particles provide a ready heat conduction between the element 8 and the support 1 without the heat content of the cathode being increased noteworthily.
  • the expansion also is negligible so that working loose of the layer of metal powder from the support does not occur, the more so since the thin-walled edge 3 is flexible so that mechanical stresses in the material remain small.
  • the support 1 is then provided with a layer 11 of barium strontium carbonate and the connection strips 14 are bent to the correct shape after which the cathode, a cross section of which is shown in FIG. 4, can be incorporated in an electron gun or a discharge tube.
  • the diameter of the cathode was 1.2 mm., the thickness 0.33 mm.
  • the holder 2 was of a nickeliron alloy, the coefficient of expansion of which is approximately 70 X10 and which corresponds to that of the tungsten of the filament 20.
  • the thickness of the support was 50 microns, the wall thickness of the holder 2 was 20 u.
  • the grain size of the nickel powder 9 was from 1 to 10 1..
  • a porous support I compressed from tungsten powder may alternatively be used and afterwards be impregnated with emitting material.
  • a profiled support 1 may alternatively be used which may comprise an emitting pill.
  • nickel powder 9 a powder of any of the commonly used known metals, for example, tungsten, palladium, or molybdenum may be used.
  • a method of manufacturing an indirectly heated disclike cathode consisting of a support for the emitting material which is secured to a metal holder containing a heating element, the space between the heating element and the support being filled with a sintered metal powder, comprising the steps of welding an end face of a cup-shaped holder for the heating element along an inwardly directed edge to the support to form therewith a gap having a wedgelike cross section between the inwardly directed edge of the end face and the support, said end face having an aperture therein, thereafter dipping the heating element in a suspension of a metal powder, placing the heating element with the metal powder thereon in the holder, dipping the support with the holder in a suspension medium of the metal powder to fill the gap between the support and the holder, heating the support and the holder to remove the suspension medium, sintering the metal powder, and thereafter providing the support with an emitting material.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)
  • Powder Metallurgy (AREA)
US695410A 1967-01-25 1968-01-03 Method of manufacturing an indirectly heated disclike cathode and cathode manufactured by said method Expired - Lifetime US3574910A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6701138A NL6701138A (nl) 1967-01-25 1967-01-25

Publications (1)

Publication Number Publication Date
US3574910A true US3574910A (en) 1971-04-13

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ID=19799112

Family Applications (1)

Application Number Title Priority Date Filing Date
US695410A Expired - Lifetime US3574910A (en) 1967-01-25 1968-01-03 Method of manufacturing an indirectly heated disclike cathode and cathode manufactured by said method

Country Status (10)

Country Link
US (1) US3574910A (nl)
AT (1) AT276575B (nl)
BE (1) BE709773A (nl)
CH (1) CH470077A (nl)
DK (1) DK118299B (nl)
ES (1) ES349611A1 (nl)
FR (1) FR1555931A (nl)
GB (1) GB1159233A (nl)
NL (1) NL6701138A (nl)
SE (1) SE325341B (nl)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3117249A (en) * 1960-02-16 1964-01-07 Sperry Rand Corp Embedded heater cathode
US3227911A (en) * 1963-10-24 1966-01-04 Eitel Mccullough Inc Indirectly heated cathodes
US3265495A (en) * 1961-02-07 1966-08-09 Csf Method of manufacturing cathodes
US3341917A (en) * 1963-04-30 1967-09-19 Matsushita Electronics Corp Method of manufacturing cathodes for electron tubes

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3117249A (en) * 1960-02-16 1964-01-07 Sperry Rand Corp Embedded heater cathode
US3265495A (en) * 1961-02-07 1966-08-09 Csf Method of manufacturing cathodes
US3341917A (en) * 1963-04-30 1967-09-19 Matsushita Electronics Corp Method of manufacturing cathodes for electron tubes
US3227911A (en) * 1963-10-24 1966-01-04 Eitel Mccullough Inc Indirectly heated cathodes

Also Published As

Publication number Publication date
FR1555931A (nl) 1969-01-31
NL6701138A (nl) 1968-07-26
DK118299B (da) 1970-08-03
GB1159233A (en) 1969-07-23
AT276575B (de) 1969-11-25
CH470077A (de) 1969-03-15
DE1614307A1 (de) 1970-07-09
DE1614307B2 (de) 1976-01-02
SE325341B (nl) 1970-06-29
BE709773A (nl) 1968-07-23
ES349611A1 (es) 1969-10-01

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