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US2724070A - Cathode coating for electrical discharge devices and method for making the same - Google Patents

Cathode coating for electrical discharge devices and method for making the same Download PDF

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Publication number
US2724070A
US2724070A US335908A US33590853A US2724070A US 2724070 A US2724070 A US 2724070A US 335908 A US335908 A US 335908A US 33590853 A US33590853 A US 33590853A US 2724070 A US2724070 A US 2724070A
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US
United States
Prior art keywords
coating
cathode
weight
fused
zirconium dioxide
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
US335908A
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English (en)
Inventor
Thomas H Heine
Meister George
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CBS Corp
Original Assignee
Westinghouse 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
Priority to BE526330D priority Critical patent/BE526330A/xx
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US335908A priority patent/US2724070A/en
Priority to DEW12927A priority patent/DE967713C/de
Priority to GB2891/54A priority patent/GB739367A/en
Priority to FR1095943D priority patent/FR1095943A/fr
Priority to ES0213564A priority patent/ES213564A1/es
Application granted granted Critical
Publication of US2724070A publication Critical patent/US2724070A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/04—Electrodes; Screens; Shields
    • H01J61/06—Main electrodes
    • H01J61/067—Main electrodes for low-pressure discharge lamps
    • H01J61/0675—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode
    • H01J61/0677—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode characterised by the electron emissive material
    • 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
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2913—Rod, strand, filament or fiber
    • Y10T428/2933—Coated or with bond, impregnation or core
    • Y10T428/294—Coated or with bond, impregnation or core including metal or compound thereof [excluding glass, ceramic and asbestos]
    • Y10T428/2958—Metal or metal compound in coating

Definitions

  • the present invention relates to electron emissive coatings for cathodes of electrical discharge devices and, more particularly, to an electron emissive coating for the fused type of cathode which may be used with instant start fluorescent lamps.
  • Fused cathodes are disclosed in Patent No. 2,476,590 to George S. Evans, dated July 19, 1949, and assigned 'to the same assignee as the present invention, in which the method for making fused cathodes is carefully outlined.
  • the fused cathode emission material therein described is barium oxide, and the life of a fluorescent lamp with a barium oxide fused cathode is greately increased over a lamp utilizing an unfused cathode when used in applications where frequent instant starting is required, such as a flashing sign.
  • Another object of our invention is to provide an electron emissive material adapted for use as a cathode coating in instant start fluorescen lamps, which coating will have a long life.
  • a still further object of our invention is to provide an improved method of preparing cathode coatings of electron emissive materials for electrical discharge devices.
  • cathode electron emissive coating which is composed of barium oxide and magnesium oxide, with or without zirconium dioxide.
  • Fig. l is a cut-away View of an instant start fluorescent lamp having a fused cathode utilizing our new emission material
  • Fig. 2 is a sectional view of an indirect heated type of cathode utilizing the fused emission material of this invention.
  • the accompanying drawing illustrates the use of our emission material in a fused cathode fluorescent lamp 10.
  • the lamp 10 has a light transmitting envelope 12 with bases 14 at each end of the envelope.
  • a cold-hot cathode or electron emissive coated electrode 16 is supported at each end of the envelope by lead-in conductors 18 sealed through a re-entrant stem press 20 and which make electrical connection to the base 14, thereby providing means for supplying power to the lamp.
  • This type of cathode is called a cold-hot" cathode, since the cathode is started cold and operated hot.
  • the cold-hot cathodode is a filamentary type cathode in which the refractory metal wire is wound into a minor coil, which in turn is wound into a major coil, thus forming a coiled-coil as is common in the art.
  • This coiled-coil refractory metal wire is preferably tungsten, but may be any suitable refractory metal, such as molybdenum. Fused on the inner coil of this coiled-coil refractory metal filament and adhering thereto is the emission material of our invention.
  • the sealed light transmitting envelope 12 encloses a small amount of mercury 22 to provide mercury vapor, and a filling of inert ionizable gas, such as argon, to facilitate starting.
  • a representative pressure of inert ionizable gas is 3.2 mm., and a representative operating mercury vapor pressure is 10 microns.
  • a fluorescent material 24 is coated on the inner side of envelope 12.
  • Fused cathodes used in instant start fluorescent lamps generally utilize alkaline earth oxides either singly or in combination with one or both of the other alkaline earth oxides.
  • the alkaline earth metal of the cathode is preferably barium and the cathode is made in accordance with the teachings of the heretofore-mentioned patent to George S. Evans.
  • a coating of barium carbonate or some other compound of barium which will reduce to the oxide is applied to the base metal of the cathode.
  • the application to the base metal may be accomplished by first ball milling the barium carbonate to a small particle size, mixing the carbonate with a binder, and spraying, painting or otherwise applying the coating to the base metal.
  • the decomposition of barium carbonate starts at about 500 C.
  • the temperature is quickly raised to liOO" C. so that the carbonate has small chance to totally or even appreciably decompose due to heating before 1100" C. is reached.
  • the carbonate is heated from 500 C. to 1100 C. within 30 seconds and preferably within 20 seconds, when heating an indirect heated type cathode as disclosed in the heretofore-mentioned patent to George S. Evans.
  • this heating time may be reduced to 10 seconds, since the refractory metal wire is in direct contact with the barium carbonate and more rapid heating is possible.
  • the fused electron emissive coating of the cathode contains magnesium oxide in addition to the barium oxide and may contain an addition of zirconium dioxide.
  • the minimum amount of barium oxide which may be used in our fused electron emissive coating is controlled by the minimum amount of barium carbonate which may be used in the original unfused coating mixture, and which is reduced to barium oxide upon fusion. It has been found that if there is less than 85 parts by weight of barium carbonate in the unfused mixture, the method of heat treatment hereinafter outlined will not result in a fused electron emissive coating such as is disclosed in the heretofore-mentioned patent to George S. Evans.
  • the parts by weight of barium carbonate should be used in the original mixture, if fusion is to be effected.
  • the parts by weight of magnesium oxide in the unfused coating mixture may vary from 1 to 15.
  • the parts by weight of zirconium dioxide in the unfused coating mixture may vary from to 14.
  • the totalparts by weight of the magnesium oxide plus the zirconium dioxide in the unfused coating mixture should not exceed 15
  • the resultant percentages of barium oxide, magnesium oxide and zirconium dioxide will fall within the limits shown in the following tables:
  • Coating mixture before fusion I Permissible parts Component; by weight Barium carbonate 85-99 Magnesium oxide 115 Zirconium dioxide 014 Magnesium oxide plus zirconium dioxide not to exceed 15 parts by weight.
  • Fused electron emissive coating Permissible parts Component by weight Barium oxide 81.5-98.5 Magnesium oxide 1.2-185 Zirconium dioxide 0 17.3
  • Magnesium oxide plus zirconium dioxide not to exceed 18.5 parts by weight.
  • a fused cathode electron emissive coating which gives very good results in life tests consists of 87.5 parts or percent by weight barium oxide, 6.25 parts or percent by weight magnesium oxide, and 6.25 parts or percent by weight zirconium dioxide.
  • the base metal of the cathode may be coated with a material composed of, by weight, 90 parts barium carbonate, parts magnesium oxide, and 5 parts zirconium dioxide.
  • This coating material may be prepared and applied by ball milling a mixture of the carbonate and oxides into small particles, mixing with a binder as is well known in the art, and applying the resultant mixtures to the base metal by painting, spraying, or dipping.
  • the cathode is then heat treated in the same manner as de-' scribed heretofore for making fused cathodes of barium oxide; While we prefer to utilize barium carbonate, magnesium oxide, and zirconium dioxide as the batch cornponents of our cathode coating, any other compounds may beused which will decompose to the oxides of barium, magnesium and zirconium respectively, upon heating. Preferably the fused coating adheres to the inner coil only, and does not bridge the outer coils of the coiled-coil.
  • Control lamps had cathodes Whose emission material consisted of 87.5% by weight barium oxide, and 12.5% by weight zirconium dioxide, which is the fused cathode coating which has heretofore been the most satisfactory with respect to life.
  • the average life of the cathodes in the control lamps was approximately 4700 hours, while the average life of the cathodes in the lamps which embodied our new emission material was approximately 6882 hours, an increase of 46%.
  • a cathode for an electrical discharge device com prising a refractory metal coil and a fused coating there on and adhering thereto, said coating comprising barium oxide and magnesium oxide, said barium oxide being not less than 81.5% nor more than 98.5% by weight of said coating.
  • a cold-hot cathode for an electrical discharge device comprising a coiled-coil refractory metal wire and a fused coating thereon and adhering thereto, said coating comprising barium oxide and magnesium oxide, said barium oxide being not less than 81.5 nor more than 98.5% by weight of said coating.
  • a cathode for an electrical discharge device comprising a refractory metal wire and a fused coating thereon and adhering thereto, said coating comprising barium oxide, magnesium oxide and an addition of zirconium dioxide if desired, said barium oxide being not less than 81.5 nor more than 98.5% by weight of said coating, said magnesium oxide being not less than 1.2% nor more than 18.5% by weight of said coating, said zirconium dioxide being not more than 17.3% by weight of said coating, and the additive weights of said magnesium oxide and said zirconium dioxide not exceeding 18.5% by weight of the said coating.
  • a cold-hot cathode for an electrical discharge device comprising a coiled-coil tungsten wire and a fused coating thereon and adhering thereto, said coating comprising barium oxide, magnesium oxide and an addition of zirconium dioxide if desired, said barium oxide being not less than 81.5% nor more than 98.5% by weght of said coating, said magnesium oxide being not less than 1.2% nor more than 18.5% by weight of said coating, said zirconium dioxide being not more than 17.3% by weight of said coating, and the additive weights of saidmagnesium oxide and said zirconium dioxide not exceeding 18.5% by weight of the said coating.
  • a cathode for an electrical discharge device comprising a coiled-coil molybdenum wire and a fused coating thereon and adhering thereto, said coating comprising barium oxide, magnesium oxide and an addition of zirconium dioxide if desired, said barium oxide being not less than 81.5 nor more than 98.5 by weight of said coating, said magnesium oxide being not less than 1.2% not more than 18.5% by weight of said coating, said zirconium dioxide being not more than 17.3% by weight of said coating, and the additive Weights of said magnesium oxide and said zirconium dioxide not exceeding 18.5 by weight of the said coating.
  • a cathode for an electrical discharge device comprising a coiled-coil tungsten wire and a fused coating thereon and adhering thereto, said coating comprising barium oxide, magnesium oxide and zirconium dioxide, said barium oxide being about 87.5% by weight of said coating, said magnesium oxide being about 6.25% by weight of said coating, and said zirconium dioxide being about 6.25% by weight of said coating.
  • An indirect heated type cathode comprising a base portion of nickel and a fused coating thereon and adhering thereto, said coating comprising barium oxide and magnesium oxide, said barium oxide being not less than 81.5% nor more than 98.5% by weight of said coating.
  • An indirect heated type cathode comprising a base portion of nickel and a fused coating thereon and adhering thereto, said coating comprising barium oxide, magnesium oxide and an addition of zirconium dioxide, if desired, said barium oxide being not less than 81.5% nor more than 98.5% by weight of said coating, said magnesium oxide being not less than 1.2% nor more than 18.5% by weight of said coating, said zirconium dioxide being not more than 17.3% by weight of said coating, and the additive weights of said magnesium oxide and said zirconium dioxide not exceeding 18.5% of said coating.
  • An indirect heated type cathode comprising a base portion of an alloy of nickel-cobalt and ferrotitanium and a fused coating thereon and adhering thereto, said coating comprising barium oxide, magnesium oxide and an addition of zirconium dioxide if desired, said barium oxide being not less than 81.5% nor more than 98.5% by weight of said coating, said magnesium oxide being not less than 1.2% nor more than 18.5% by weight of said coating, said zirconium dioxide being not more than 17.3% by weight of said coating, and the additive weights of said magnesium oxide and said zirconium dioxide not exceeding 18.5% by weight of said coating.

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  • Discharge Lamp (AREA)
US335908A 1953-02-09 1953-02-09 Cathode coating for electrical discharge devices and method for making the same Expired - Lifetime US2724070A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
BE526330D BE526330A (xx) 1953-02-09
US335908A US2724070A (en) 1953-02-09 1953-02-09 Cathode coating for electrical discharge devices and method for making the same
DEW12927A DE967713C (de) 1953-02-09 1953-12-29 Emissionselektrode fuer elektrische Entladungsroehren und Verfahren zur Herstellung dieser Elektrode
GB2891/54A GB739367A (en) 1953-02-09 1954-02-01 Improvements in or relating to electron emissive electrodes for electrical dischargedevices
FR1095943D FR1095943A (fr) 1953-02-09 1954-02-05 Revêtement cathodique pour appareils à décharges électriques, et procédé de fabrication
ES0213564A ES213564A1 (es) 1953-02-09 1954-02-08 Mejoras introducidas en los electrodos emisores para tubos de descarga eléctrica

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US335908A US2724070A (en) 1953-02-09 1953-02-09 Cathode coating for electrical discharge devices and method for making the same

Publications (1)

Publication Number Publication Date
US2724070A true US2724070A (en) 1955-11-15

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Family Applications (1)

Application Number Title Priority Date Filing Date
US335908A Expired - Lifetime US2724070A (en) 1953-02-09 1953-02-09 Cathode coating for electrical discharge devices and method for making the same

Country Status (6)

Country Link
US (1) US2724070A (xx)
BE (1) BE526330A (xx)
DE (1) DE967713C (xx)
ES (1) ES213564A1 (xx)
FR (1) FR1095943A (xx)
GB (1) GB739367A (xx)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2858470A (en) * 1955-02-02 1958-10-28 Bell Telephone Labor Inc Cathode for electron discharge devices
US2963450A (en) * 1958-03-17 1960-12-06 Interlectric Corp Filament coating composition
US2985946A (en) * 1955-05-10 1961-05-30 Philips Corp Indirectly heated cathode
US3427491A (en) * 1966-04-20 1969-02-11 Matsushita Electronics Corp Discharge tube
US3427492A (en) * 1966-04-20 1969-02-11 Matsushita Electronics Corp Discharge tube satisfactorily low in radio-interfering noise
US3523915A (en) * 1966-03-21 1970-08-11 Commissariat Energie Atomique Electrically conductive ceramic material and method of preparation
US3951874A (en) * 1974-07-10 1976-04-20 International Telephone And Telegraph Corporation Method for preparing electron emissive coatings
US3953376A (en) * 1974-07-10 1976-04-27 International Telephone And Telegraph Corporation Method for preparing emissive coating for electrodes
US4031426A (en) * 1974-07-10 1977-06-21 International Telephone And Telegraph Corporation Emissive coating for electrodes
US4210839A (en) * 1978-03-13 1980-07-01 Westron of Canada Limited Mercury lamp for promoting plant growth
US4251569A (en) * 1975-10-22 1981-02-17 Gte Products Corporation Method of coating arc discharge lamp electrode
WO2012060998A1 (en) * 2010-11-03 2012-05-10 General Electric Company Electron emission material

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5744905A (en) * 1994-12-23 1998-04-28 Philips Electronics North America Corporation Emission materials for discharge lamps and method for manufacturing electrode structures with such materials

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1830825A (en) * 1928-11-20 1931-11-10 Kemet Lab Co Inc Cathode
US2018993A (en) * 1930-06-03 1935-10-29 Sirian Lamp Co Electrical discharge material and method of manufacturing it
GB624009A (en) * 1942-11-14 1949-05-26 Philips Nv Improvements in or relating to electric discharge tubes
US2476590A (en) * 1943-07-03 1949-07-19 Westinghouse Electric Corp Cathode coating
US2530394A (en) * 1947-06-05 1950-11-21 Sylvania Electric Prod Electrode coating for discharge devices
US2542352A (en) * 1947-06-10 1951-02-20 Gen Electric Lead wire for fluorescent lamps

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1453267A (en) * 1918-11-29 1923-05-01 Forest Radio Telephone & Teleg Electron-emitting cathode and method of making the same
BE335031A (xx) * 1926-06-14
DE600129C (de) * 1926-07-11 1934-07-14 Osram G M B H Komm Ges Oxydkathode
DE597580C (de) * 1928-05-01 1934-05-26 Osram G M B H Komm Ges Elektrische Leucht- oder Ultraviolett-Bestrahlungsroehre
DE627520C (de) * 1929-05-05 1936-03-17 Osram G M B H Komm Ges Elektrische Entladungsroehre beliebiger Fuellung mit Gluehelektroden und Entladung durch die positive Saeule
US2266662A (en) * 1931-11-21 1941-12-16 Gen Electric Discharge device
NL41599C (xx) * 1934-10-27
BE440175A (xx) * 1936-09-03

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1830825A (en) * 1928-11-20 1931-11-10 Kemet Lab Co Inc Cathode
US2018993A (en) * 1930-06-03 1935-10-29 Sirian Lamp Co Electrical discharge material and method of manufacturing it
GB624009A (en) * 1942-11-14 1949-05-26 Philips Nv Improvements in or relating to electric discharge tubes
US2476590A (en) * 1943-07-03 1949-07-19 Westinghouse Electric Corp Cathode coating
US2530394A (en) * 1947-06-05 1950-11-21 Sylvania Electric Prod Electrode coating for discharge devices
US2542352A (en) * 1947-06-10 1951-02-20 Gen Electric Lead wire for fluorescent lamps

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2858470A (en) * 1955-02-02 1958-10-28 Bell Telephone Labor Inc Cathode for electron discharge devices
US2985946A (en) * 1955-05-10 1961-05-30 Philips Corp Indirectly heated cathode
US2963450A (en) * 1958-03-17 1960-12-06 Interlectric Corp Filament coating composition
US3523915A (en) * 1966-03-21 1970-08-11 Commissariat Energie Atomique Electrically conductive ceramic material and method of preparation
US3427491A (en) * 1966-04-20 1969-02-11 Matsushita Electronics Corp Discharge tube
US3427492A (en) * 1966-04-20 1969-02-11 Matsushita Electronics Corp Discharge tube satisfactorily low in radio-interfering noise
US3951874A (en) * 1974-07-10 1976-04-20 International Telephone And Telegraph Corporation Method for preparing electron emissive coatings
US3953376A (en) * 1974-07-10 1976-04-27 International Telephone And Telegraph Corporation Method for preparing emissive coating for electrodes
US4031426A (en) * 1974-07-10 1977-06-21 International Telephone And Telegraph Corporation Emissive coating for electrodes
US4251569A (en) * 1975-10-22 1981-02-17 Gte Products Corporation Method of coating arc discharge lamp electrode
US4210839A (en) * 1978-03-13 1980-07-01 Westron of Canada Limited Mercury lamp for promoting plant growth
WO2012060998A1 (en) * 2010-11-03 2012-05-10 General Electric Company Electron emission material

Also Published As

Publication number Publication date
GB739367A (en) 1955-10-26
FR1095943A (fr) 1955-06-07
DE967713C (de) 1957-12-05
ES213564A1 (es) 1954-06-16
BE526330A (xx)

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