US3441438A - Method to form hot cathodes - Google Patents

Method to form hot cathodes Download PDF

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Publication number
US3441438A
US3441438A US461532A US3441438DA US3441438A US 3441438 A US3441438 A US 3441438A US 461532 A US461532 A US 461532A US 3441438D A US3441438D A US 3441438DA US 3441438 A US3441438 A US 3441438A
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US
United States
Prior art keywords
sleeve
cathode
temperature
coating
form hot
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
US461532A
Inventor
Eberhard Weiss
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International Standard Electric Corp
Original Assignee
International Standard Electric Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by International Standard Electric Corp filed Critical International Standard Electric Corp
Application granted granted Critical
Publication of US3441438A publication Critical patent/US3441438A/en
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Classifications

    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S228/00—Metal fusion bonding
    • Y10S228/903—Metal to nonmetal

Definitions

  • This invention relates to a method for forming hot cathodes of electron discharge devices having an emissive coating of alkaline-earth metal oxides.
  • the cathodes are heated for approximately five minutes to a temperature of 1,000 1,200 0, either with or without drawing current and thereafter the temperature of the cathode is reduced in steps to the operating temperature within approximately 30 minutes.
  • a particularly large evaporation of barium occurs due to the high temperature and the length of time at which the temperature continues.
  • the evaporation of the emissive coating causes faults in the insulation and a reduction of emission.
  • the barium evaporation is reduced.
  • this requires excessive time, which is not economical for mass production.
  • the cathode sleeve is heated in approximately 2-10 seconds, depending on the heat inertia caused by the material of the sleeve, to 1,200 C., in order to obtain a maximum difference between the temperature of the cathode sleeve and the temperature of the emissive coat.
  • the heat is thereupon interrupted and switched on and off repeatedly up to a few hundred times.
  • the cathode Due to the sudden heating of the cathode, a high temperature gradient is obtained between the cathode sleeve and emissive coating as well as within the emissive coat from the end of the sleeve to the surface of the coat.
  • the sleeve having reducing means such as magnesium, carbon, or silicon for the alkaline-earth metal oxides, reaches a very high temperature so that these metals quickly diffuse into the coating, while the interior and surface of the emissive coating remain correspondingly colder,
  • Patented thereby limiting the evaporation of barium set free by the reducing means. Due to the saturation of available barium in the emissive coating, emission is obtained in a short time, which was not possible in the prior art. In some special cases, the sleeve should be cooled down to 300 C. before switching on the heat again.
  • the cathode sleeve expands in all directions. This expansion causes the holes in the mica-discs in which the cathode sleeve is supported to be forced open.
  • the cathode sleeve applies soft pressure to seat in the holes of the mica disc, while during operating temperatures a natural fitting seat is obtained.
  • a method for forming hot cathodes of electric discharge devices having a cathode sleeve and an emissive coating of alkaline-earth metallic oxides comprising rapidly heating the cathode to about 1,200 C. within 2 to 10 seconds, and repeatedly interrupting the heating for a sufficient time by switching the heat on and off from onehundred to several hundred times to provide a maximum temperature difference between the cathode sleeve and emissive coating to minimize evaporation of the emissive coating.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
  • Solid Thermionic Cathode (AREA)

Description

United States Patent 0 U.S. 'CL 117-223 2 Claims ABSTRACT OF THE DISCLOSURE A cathode sleeve and emissive coating are heated rapidly to about 1,200 C. with the heating being repeatedly interrupted to maintain a maximum temperature difference between the sleeve and coating to minimize evaporation of the coating.
This invention relates to a method for forming hot cathodes of electron discharge devices having an emissive coating of alkaline-earth metal oxides.
In a known forming method, the cathodes are heated for approximately five minutes to a temperature of 1,000 1,200 0, either with or without drawing current and thereafter the temperature of the cathode is reduced in steps to the operating temperature within approximately 30 minutes. In this method a particularly large evaporation of barium occurs due to the high temperature and the length of time at which the temperature continues. The evaporation of the emissive coating causes faults in the insulation and a reduction of emission. When using a low starting temperature the barium evaporation is reduced. However, this requires excessive time, which is not economical for mass production.
In order to avoid these drawbacks, according to the invention, the cathode sleeve is heated in approximately 2-10 seconds, depending on the heat inertia caused by the material of the sleeve, to 1,200 C., in order to obtain a maximum difference between the temperature of the cathode sleeve and the temperature of the emissive coat. The heat is thereupon interrupted and switched on and off repeatedly up to a few hundred times.
Due to the sudden heating of the cathode, a high temperature gradient is obtained between the cathode sleeve and emissive coating as well as within the emissive coat from the end of the sleeve to the surface of the coat. The sleeve, having reducing means such as magnesium, carbon, or silicon for the alkaline-earth metal oxides, reaches a very high temperature so that these metals quickly diffuse into the coating, while the interior and surface of the emissive coating remain correspondingly colder,
Patented thereby limiting the evaporation of barium set free by the reducing means. Due to the saturation of available barium in the emissive coating, emission is obtained in a short time, which was not possible in the prior art. In some special cases, the sleeve should be cooled down to 300 C. before switching on the heat again.
Due to the rapid switching of the heat on and off, the cathode sleeve expands in all directions. This expansion causes the holes in the mica-discs in which the cathode sleeve is supported to be forced open. The cathode sleeve, adjacent the holes, deforms inwardly so that the crosssection of the sleeve exactly corresponds to the form of a hole in the mica-disc. At the high forming temperature the cathode sleeve applies soft pressure to seat in the holes of the mica disc, while during operating temperatures a natural fitting seat is obtained.
This avoids the variations, pressure and chattering that normally occur due to poor fittings about the cathodes during operation of devices, formed according to prior methods. No play occurs between the cathode sleeve and the hole in the mica disc. There is also no excess pressure since the heat emanated at the sleeve end is smaller and the temperature of the cathode is higher and more uniform over its entire length. In addition, the method provides an extremely long life expectancy for the cathodes. Also, filament failures, which would occur after a short time of operation, are now found and eliminated when forming the cathode, as a result of the rapid switching.
What is claimed is:
1. A method for forming hot cathodes of electric discharge devices having a cathode sleeve and an emissive coating of alkaline-earth metallic oxides, comprising rapidly heating the cathode to about 1,200 C. within 2 to 10 seconds, and repeatedly interrupting the heating for a sufficient time by switching the heat on and off from onehundred to several hundred times to provide a maximum temperature difference between the cathode sleeve and emissive coating to minimize evaporation of the emissive coating.
2. The method of claim 1 wherein the sleeve is cooled down to a predetermined lower temperature before the heat is switched on again to provide said temperature difference.
References Cited FOREIGN PATENTS 7/1926 Great Britain. 12/ 1927 Great Britain.
WILLIAM L. JARVIS, Primary Examiner.
US461532A 1964-07-03 1965-06-04 Method to form hot cathodes Expired - Lifetime US3441438A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEST22348A DE1205628B (en) 1964-07-03 1964-07-03 Process for forming glow cathodes

Publications (1)

Publication Number Publication Date
US3441438A true US3441438A (en) 1969-04-29

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US461532A Expired - Lifetime US3441438A (en) 1964-07-03 1965-06-04 Method to form hot cathodes

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US (1) US3441438A (en)
DE (1) DE1205628B (en)
NL (1) NL6508590A (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3969279A (en) * 1974-08-13 1976-07-13 International Telephone And Telegraph Corporation Method of treating electron emissive cathodes

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3151347C1 (en) * 1981-12-24 1983-05-05 Standard Elektrik Lorenz Ag, 7000 Stuttgart Process for forming glow cathodes

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB239539A (en) * 1924-09-05 1926-07-08 Dubilier Condenser Co 1925 Ltd Improved process for making electron-emitting electrodes
GB272549A (en) * 1926-06-14 1927-12-08 Eugene Rouge A process for the production of electronic discharge tubes, and tubes produced by such process

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB239539A (en) * 1924-09-05 1926-07-08 Dubilier Condenser Co 1925 Ltd Improved process for making electron-emitting electrodes
GB272549A (en) * 1926-06-14 1927-12-08 Eugene Rouge A process for the production of electronic discharge tubes, and tubes produced by such process

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3969279A (en) * 1974-08-13 1976-07-13 International Telephone And Telegraph Corporation Method of treating electron emissive cathodes

Also Published As

Publication number Publication date
DE1205628B (en) 1965-11-25
NL6508590A (en) 1966-01-04

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