US3553521A - Indirectly heated cathode for an electron discharge tube with an insulated heating element - Google Patents

Indirectly heated cathode for an electron discharge tube with an insulated heating element Download PDF

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Publication number
US3553521A
US3553521A US701204*A US3553521DA US3553521A US 3553521 A US3553521 A US 3553521A US 3553521D A US3553521D A US 3553521DA US 3553521 A US3553521 A US 3553521A
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US
United States
Prior art keywords
heating wire
layer
heating element
discharge tube
indirectly heated
Prior art date
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
Application number
US701204*A
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English (en)
Inventor
Marinus Antonius Maria Bakker
Johannes Christiaan Duran
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US Philips Corp
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US Philips Corp
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Publication date
Application filed by US Philips Corp filed Critical US Philips Corp
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Publication of US3553521A publication Critical patent/US3553521A/en
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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
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H01J1/24—Insulating layer or body located between heater and emissive material
    • 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
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H01J1/26—Supports for the emissive material

Definitions

  • the invention relates to an indirectly heated cathode provided with a heating wire which is insulated by alumina from a support for the emissive material, while at least the surface of this support facing the heating wire consists of molybdenum.
  • the tungsten or molybdenum of a heating wire for an indirectly heated cathode may be attacked by oxygen, in which event the W or M00 formed evaporates and reacts with the insulating material consisting of alumina. The metal is then released and the insulation resistance of the insulating material gradually decreases. According to the known method, this is prevented by coating the tungsten or molybdenum heating wire with a suitable metal of the platinum group and by fusing this metal to the heating wire by a electrical current transient and strong heat treatment. It is emphatically stated that only molten layers of these metals are effective,whereas nonmolten layers of thesemet'als applied, for example, by electroplating may exhibit the said disadvantage to an even greater extent.
  • the layers In order to prevent the resistance of the heating wire from becoming unduly low, the layers must be extremely thin (at the most 1 11.). Platinum itself cannot be used, since at the high temperature of the heating wire it is dissolved in the molybdenum during the melting process, while rhenium has an unduly high melting temperature so that it cannot be fused to the heating wire.
  • the insulation resistance still decreases in cathodes in which at least the surface of the support for the emissive material facing the heating wire consists of molybdenum, especially if the support has a positive potential with respect to the heating wire.
  • a favourable effect may also be obtained by the application of a nonmolten layer of one of the said metals of the Pt group if the thickness of such a layer is 3 microns or more.
  • a Pt layer having a thickness of 3 microns is found to have a sufficient density. It has been found that due to the lower temperature of the sup port, only such a small quantity of Pt is dissolved in the Mo of the support and conversely that this doesnot give rise to dif' ficulties during the life of the cathode. ln this case, the comparatively thick metal layer does not give rise to difficulties either with respect to the resistance of the support so that such comparatively thick layers can be used without any objection.
  • the invention is preferably carried out in conjunction with the known method described.
  • reference numeral 1 denotes the support which in this case entirely consists of molybdenum.
  • Theheater body 2 consists of a heating wire 3 to which a layer 6 of rhodium, ruthenium or iridium having a thickness of less than 1 u is fused by the known method.
  • the heating'wire 3 is coated with alumina.
  • the support 1 is provided with an emissive layer 4 which preferably consists of a mixture of nickel powder and alkaline earth metal oxides.
  • the surface of the support 1 facing the heating wire 3 is coated with a platinum layer having a thickness of 5 p.. Instead pf platinum, also one of the other metals of the platinum group may be used for the layer 5
  • the layer 5 15 preferably applied by absorption of a platinum suspension or by electroplating.
  • a cathode according to the invention is particularly suitable for use in circuit arrangements in which a potential difference of more than 400 v. may occur betweenthe heating wire and the cathode support, the support 1 being positive with respect to the heating wire 3.
  • cathode Although only one embodiment of a cathode according to the invention has been described, the invention also applies to differently shaped cathodes, for example, dispenser cathodes. Furthermore, the emissive material may also be applied to a tubular support. Instead of A1 0 MgO may be used.
  • An indirectly heated cathode for an electron discharge tube provided with a heating wire which is insulated by means of a metal oxide from a support foran emissive layer, at least the surface of this support facing the heating wire consisting of molybdenum, said surface'having thereon a layer of at least one of the metals of the platinum group having a thickness of at least Bu.

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  • Solid Thermionic Cathode (AREA)
US701204*A 1967-02-17 1968-01-29 Indirectly heated cathode for an electron discharge tube with an insulated heating element Expired - Lifetime US3553521A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL676702376A NL153018B (nl) 1967-02-17 1967-02-17 Indirect verhitte kathode.

Publications (1)

Publication Number Publication Date
US3553521A true US3553521A (en) 1971-01-05

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ID=19799315

Family Applications (1)

Application Number Title Priority Date Filing Date
US701204*A Expired - Lifetime US3553521A (en) 1967-02-17 1968-01-29 Indirectly heated cathode for an electron discharge tube with an insulated heating element

Country Status (8)

Country Link
US (1) US3553521A (de)
AT (1) AT276576B (de)
BE (1) BE710828A (de)
CH (1) CH468713A (de)
ES (1) ES350511A1 (de)
FR (1) FR1553520A (de)
GB (1) GB1150409A (de)
NL (1) NL153018B (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3881126A (en) * 1974-03-06 1975-04-29 Gte Sylvania Inc Fast warm-up cathode assembly
US3883767A (en) * 1974-02-08 1975-05-13 Gte Sylvania Inc Heater for fast warmup cathode
US4291252A (en) * 1978-11-29 1981-09-22 Hitachi, Ltd. Electron tube cathode
US4401919A (en) * 1980-08-07 1983-08-30 Itt Industries, Inc. Indirectly heated Wehnelt cathode
FR2557356A1 (fr) * 1983-12-22 1985-06-28 Philips Nv Cathode a oxyde

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1719988A (en) * 1923-01-26 1929-07-09 Westinghouse Lamp Co Electron device and the like adapted for alternating current
US2733378A (en) * 1956-01-31 Thermionic cathodes for electronic discharge devices
US2878410A (en) * 1954-11-09 1959-03-17 Gen Electric Electronic tube structure
US3268305A (en) * 1964-08-17 1966-08-23 Sylvania Electric Prod Composite wire
US3283195A (en) * 1962-02-14 1966-11-01 Philips Corp Cold-cathode glow-discharge tube
US3401297A (en) * 1965-08-23 1968-09-10 Varian Associates Thermionic cathodes for electron discharge devices with improved refractory metal heater wires

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2733378A (en) * 1956-01-31 Thermionic cathodes for electronic discharge devices
US1719988A (en) * 1923-01-26 1929-07-09 Westinghouse Lamp Co Electron device and the like adapted for alternating current
US2878410A (en) * 1954-11-09 1959-03-17 Gen Electric Electronic tube structure
US3283195A (en) * 1962-02-14 1966-11-01 Philips Corp Cold-cathode glow-discharge tube
US3268305A (en) * 1964-08-17 1966-08-23 Sylvania Electric Prod Composite wire
US3401297A (en) * 1965-08-23 1968-09-10 Varian Associates Thermionic cathodes for electron discharge devices with improved refractory metal heater wires

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3883767A (en) * 1974-02-08 1975-05-13 Gte Sylvania Inc Heater for fast warmup cathode
US3881126A (en) * 1974-03-06 1975-04-29 Gte Sylvania Inc Fast warm-up cathode assembly
US4291252A (en) * 1978-11-29 1981-09-22 Hitachi, Ltd. Electron tube cathode
US4401919A (en) * 1980-08-07 1983-08-30 Itt Industries, Inc. Indirectly heated Wehnelt cathode
FR2557356A1 (fr) * 1983-12-22 1985-06-28 Philips Nv Cathode a oxyde
US4904897A (en) * 1983-12-22 1990-02-27 U.S. Philips Corporation Oxide cathode

Also Published As

Publication number Publication date
NL153018B (nl) 1977-04-15
DE1639341B2 (de) 1976-02-12
CH468713A (de) 1969-02-15
FR1553520A (de) 1969-01-10
NL6702376A (de) 1968-08-19
ES350511A1 (es) 1969-05-16
GB1150409A (en) 1969-04-30
DE1639341A1 (de) 1971-04-08
BE710828A (de) 1968-08-16
AT276576B (de) 1969-11-25

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