US3902093A - Cathode heater element with a dark heat radiating coating and method of producing such - Google Patents

Cathode heater element with a dark heat radiating coating and method of producing such Download PDF

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US3902093A
US3902093A US415256A US41525673A US3902093A US 3902093 A US3902093 A US 3902093A US 415256 A US415256 A US 415256A US 41525673 A US41525673 A US 41525673A US 3902093 A US3902093 A US 3902093A
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heater element
heat radiating
aluminum oxide
coating
producing
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US415256A
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Eberhard Weiss
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Nokia Deutschland GmbH
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International Standard Electric Corp
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Assigned to ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTERDAM, THE NETHERLANDS, A CORP OF THE NETHERLANDS reassignment ALCATEL N.V., DE LAIRESSESTRAAT 153, 1075 HK AMSTERDAM, THE NETHERLANDS, A CORP OF THE NETHERLANDS ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: INTERNATIONAL STANDARD ELECTRIC CORPORATION, A CORP OF DE
Assigned to NOKIA GRAETZ GESELLSCHAFT MIT BESCHRANKTER HAFTUNG reassignment NOKIA GRAETZ GESELLSCHAFT MIT BESCHRANKTER HAFTUNG ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: ALCATEL N.V.
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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
    • H01J9/08—Manufacture of heaters for indirectly-heated cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J29/00—Details of cathode-ray tubes or of electron-beam tubes of the types covered by group H01J31/00
    • H01J29/02—Electrodes; Screens; Mounting, supporting, spacing or insulating thereof
    • H01J29/04—Cathodes

Definitions

  • This object is attained by the use of a coating of insulating material applied to the filament which is completely porous and consists of a homogeneous dark colored sintered crystalline mixture of the insulating material, preferably aluminum oxide, A1 and of a refractory highmelting point metal such as tungsten.
  • the present heater element has proven to be completely satisfactory and has durable insulating properties.
  • An important advantage of this heater element is in the fact that it is particularly suitable for use in instant heat type cathodes.
  • the heater element As regards the manufacture of the heater element, one method has proved to be particularly favorable. This is characterized by coating the filament with a layer of aluminum oxide and by simultaneously effecting electrolysis. The resulting porous insulating layer is then dried, the heater element is thereafter impregnated with an aqueous ammoniumtungstate solution, rinsed in a suitable liquid (such as methanol) and then dried again. Finally, the heater element is heated in a nitrogen and hydrogen atmosphere with the insulating layer being sintered.
  • aqueous ammoniumtungstate solution such as methanol
  • FIGURE schematically shows the construction of an indirectly heated cathode.
  • a cathode tubing 3 has a cap 4 welded at one end which carries the emitting layer 5.
  • the structure is secured by the holder 6 which is mounted to a supporting disc 7.
  • the heater element consisting of the filament 2 coated with the insulating layer 1 is inserted into the tubing 3.
  • the filament 2 is coated with a layer of insulating material 1 which is porous throughout, with no intermediate layers, and consists of a dark colored sintered crystalline mixture of the insulating material aluminum oxide, Al O and of a refractory highmelting point metal such as tungsten.
  • the dark insulating layer 1 apart from the desired thermal properties, also provides very satisfactory results as regards insulating properties and long life, as well as only a very slight tendency toward melting during electrolysis.
  • the layer is applied or deposited as follows.
  • the heater element is dipped or immersed into a suitable coating bath containing a mixture of aluminum oxide, water, alcohol and salt, and the mixture is dissociated upon application of an electric voltage.
  • the aluminum oxide which floats in the bath, is precipitated onto the cathode, i.e. on the filament. Simultaneously, during this electrophoretic process, hydrogen appears on the cathode due to the electrolysis.
  • the mixture ratio it is possible to achieve a particular porosity for the precipitating oxide of aluminum which also has a particular elasticity.
  • the coated filaments are removed from the coating bath, and dried.
  • the dried heater elements are thereafter dipped into an aqueous ammonium-tungstate solution until the dried porous coat of insulating material is impregnated or saturated. In the course of a subsequent rising process, the heater element is again freed from a portion of the aqueous ammonium-tungstate solution.
  • a suitable rinsing liquid may be methanol. This is followed by a further drying process.
  • the heater element is heated in an oven having a nitrogen/hydrogen atmosphere up to a temperature of about 1500 to 2000C at which the insulating layer is sintered.
  • a cathode heater element comprising a conductive filament having a coating of a dark colored heat radiating insulating material, said coating being porous throughout and including a non-emissive homogeneous dark colored sintered crystalline mixture of aluminum oxide and tungsten.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)

Abstract

A cathode heater element is coated with a dark colored heat radiating porous layer of insulating material such as aluminum oxide and a refractory metal such as tungsten. The aluminum oxide is applied in an electrolytic bath, dried and impregnated with a tungstate solution. The layer is heated and sintered in a nitrogen hydrogen atmosphere. The heater element has improved heat transfer characteristics.

Description

United States Patent Weiss 1 Aug. 26, 1975 [54] CATHODE HEATER ELEMENT WITH A 3,195,004 7/1965 Hassctt 313/345 X DARK HEAT RADIATING COATING AND 3,372,297 3/1968 Pearsall.... 313/337 1 3,401,297 9/1968 Feinleib 313/337 X METHOD OF PRODUCING SUCH 3,531,678 9/1970 Schiavone... 313/337 [75] inventor: Eberhard Weiss, Stuttgart, Germany 3,558,966 1/1971 Hill 313/345 3,737,714 6/1973 Theodosopoulos.... 313/337 1 Asslgneel lmernatlonal Standard Elecmc 3,765,939 10/1973 Reid 313/337 Corporation, New York, NY.
1 Filedl 1973 Primary ExaminerSaxfield Chatmon, Jr.
Appl. No.: 415,256
Foreign Application Priority Data Apr. 6, 1973 Germany .1 2317446 US. Cl. 313/345; 313/40; 313/340; 117/217 Int. Cl. H01J 1/14; H01J 19/10 Field of Search 313/337, 345, 340, 40, 313/41; 117/217 References Cited UNITED STATES PATENTS 4/1962 Etter 313/340 Attorney, Agent, or Firm-John T. OHalloran; Menotti J. Lombardi, Jr.; Edward Goldberg 5 7 ABSTRACT 1 Claim, 1 Drawing Figure CATHODE HEATER ELEMENT WITH A DARK HEAT RADIATING COATING AND METHOD OF PRODUCING SUCH BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater element with a dark colored heat radiating coat of insulating material for indirectly heated cathodes of electron tubes and method of producing such a heater element.
2. Description of the Prior Art In the case of indirectly heated cathodes, the nature of the coat of insulating material on the conductive filament of the heater element is critical. The proper functioning of the entire assembly including the television picture tube, requires an adequate separation of potentials between the filament and the cathode tubing on which the emitting layer is positioned. For this purpose, the oxide of aluminum has proven to be useful as a good insulating material. As is well known, aluminum oxide is generally applied to the filament by electrophoretic deposition which forms a compact white layer.
In order to obtain a good transfer of heat from the heater element to the cathode tubing, and particularly to the emitting layer, efforts have been made to utilize not only the heat conduction but also the heat radiation effect. Heat radiation, however, is impeded by the white color of the oxide of aluminum. Therefore, attempts have been made for converting the white pure oxide of aluminum into a good heat radiator by the addition of dark coloring materials. As known in the prior art however, there are objections to such a dark coloring because previous experience has shown that the insulating property of the filament coating deteriorated to an undesirable degree.
For this reason, it was tried to provide the filament with a first white layer of aluminum oxide which was thereafter subjected to an externally applied dark coloring by a suitable method. These steps however did not provide any improvement with respect to the transfer of heat from the filament to the surface of the heater element, and especially not with respect to the heat radiation, and on the whole, only represent a compromise.
SUMMARY OF THE INVENTION It is therefore the object of the present invention to provide a heater element whose heat transfer properties are improved by utilizing internal heat radiation.
This object is attained by the use of a coating of insulating material applied to the filament which is completely porous and consists of a homogeneous dark colored sintered crystalline mixture of the insulating material, preferably aluminum oxide, A1 and of a refractory highmelting point metal such as tungsten. In accordance with many tests using conventional methods, the present heater element has proven to be completely satisfactory and has durable insulating properties. An important advantage of this heater element is in the fact that it is particularly suitable for use in instant heat type cathodes.
As regards the manufacture of the heater element, one method has proved to be particularly favorable. This is characterized by coating the filament with a layer of aluminum oxide and by simultaneously effecting electrolysis. The resulting porous insulating layer is then dried, the heater element is thereafter impregnated with an aqueous ammoniumtungstate solution, rinsed in a suitable liquid (such as methanol) and then dried again. Finally, the heater element is heated in a nitrogen and hydrogen atmosphere with the insulating layer being sintered. The invention will now be explained with reference to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING The single FIGURE schematically shows the construction of an indirectly heated cathode.
DESCRIPTION OF THE PREFERRED EMBODIMENT As show in the FIGURE, a cathode tubing 3 has a cap 4 welded at one end which carries the emitting layer 5. The structure is secured by the holder 6 which is mounted to a supporting disc 7. The heater element consisting of the filament 2 coated with the insulating layer 1 is inserted into the tubing 3.
From the point of view of thermal behavior, it is essential for the temperature difference between the filament 2 and the emitting layer 5 to be as small as possible, so that the operating temperature is reached as quickly as possible after current has been switched on. For this purpose the filament 2 is coated with a layer of insulating material 1 which is porous throughout, with no intermediate layers, and consists of a dark colored sintered crystalline mixture of the insulating material aluminum oxide, Al O and of a refractory highmelting point metal such as tungsten. The dark insulating layer 1, apart from the desired thermal properties, also provides very satisfactory results as regards insulating properties and long life, as well as only a very slight tendency toward melting during electrolysis. The layer is applied or deposited as follows.
The heater element is dipped or immersed into a suitable coating bath containing a mixture of aluminum oxide, water, alcohol and salt, and the mixture is dissociated upon application of an electric voltage. The aluminum oxide, which floats in the bath, is precipitated onto the cathode, i.e. on the filament. Simultaneously, during this electrophoretic process, hydrogen appears on the cathode due to the electrolysis. By suitably selecting the mixture ratio it is possible to achieve a particular porosity for the precipitating oxide of aluminum which also has a particular elasticity.
After-having reached the desired layer thickness, the coated filaments are removed from the coating bath, and dried. The dried heater elements are thereafter dipped into an aqueous ammonium-tungstate solution until the dried porous coat of insulating material is impregnated or saturated. In the course of a subsequent rising process, the heater element is again freed from a portion of the aqueous ammonium-tungstate solution. A suitable rinsing liquid may be methanol. This is followed by a further drying process.
After this the heater element is heated in an oven having a nitrogen/hydrogen atmosphere up to a temperature of about 1500 to 2000C at which the insulating layer is sintered.
What is claimed is:
l. A cathode heater element comprising a conductive filament having a coating of a dark colored heat radiating insulating material, said coating being porous throughout and including a non-emissive homogeneous dark colored sintered crystalline mixture of aluminum oxide and tungsten.

Claims (1)

1. A CATHODE HEATER ELEMENT COMPRISING A CONDUCTIVE FILAMENT HAVING A COATING OF A DARK COLORED HEAT RADIATING INSULATING MATERIAL, SAID COATING BEING POROUS THROUGHOUT AND INCLUDING A NON-EMISSIVE HOMOGENEOUS DARK COLORED SINTERED CRYSTALLINE MIXTURE OF ALUMINUM OXIDE AND TUNGSTEN.
US415256A 1973-04-06 1973-11-12 Cathode heater element with a dark heat radiating coating and method of producing such Expired - Lifetime US3902093A (en)

Applications Claiming Priority (1)

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DE2317446A DE2317446C3 (en) 1973-04-06 1973-04-06 Method of manufacturing a heating element for an indirectly heated cathode

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US (1) US3902093A (en)
JP (1) JPS5513102B2 (en)
BE (1) BE813271R (en)
CA (1) CA1032592A (en)
DE (1) DE2317446C3 (en)
ES (1) ES425053A1 (en)
FR (1) FR2224866B1 (en)
GB (1) GB1461495A (en)
IT (1) IT1007777B (en)
NL (1) NL7404521A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4079164A (en) * 1975-11-07 1978-03-14 Hitachi, Ltd. Base metal plate for directly heated oxide cathode
US4208208A (en) * 1977-11-18 1980-06-17 Hitachi, Ltd. Nickel alloy base metal plate for directly heated oxide cathodes

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4000435A (en) * 1975-06-20 1976-12-28 Westinghouse Electric Corporation Electron gun cathode with a fast warm-up characteristic
DE2835490C2 (en) * 1978-08-12 1986-09-18 Standard Elektrik Lorenz Ag, 7000 Stuttgart Process for the production of an indirectly heated cathode
DE2938248A1 (en) * 1979-09-21 1981-03-26 Standard Elektrik Lorenz AG, 70435 Stuttgart HEATING ELEMENT FOR AN INDIRECTLY HEATED CATHODE
JPS573039U (en) * 1980-06-06 1982-01-08
DE3029853C2 (en) * 1980-08-07 1982-08-26 Standard Elektrik Lorenz Ag, 7000 Stuttgart Wehnelt cathode indirectly heated by electron impact
DE19828158C1 (en) * 1998-06-24 1999-11-25 Siemens Ag Indirectly heated cathode, especially for X-ray tube

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3029360A (en) * 1958-04-29 1962-04-10 Rca Corp Heater wire coating process
US3195004A (en) * 1960-08-19 1965-07-13 Rca Corp Cathode heater for electron discharge devices
US3372297A (en) * 1964-09-28 1968-03-05 Varian Associates High frequency electron discharge devices and thermionic cathodes having improved (cvd) refractory insulation coated heater wires
US3401297A (en) * 1965-08-23 1968-09-10 Varian Associates Thermionic cathodes for electron discharge devices with improved refractory metal heater wires
US3531678A (en) * 1968-06-24 1970-09-29 Raytheon Co Heater with boron nitride coating
US3558966A (en) * 1967-03-01 1971-01-26 Semicon Associates Inc Directly heated dispenser cathode
US3737714A (en) * 1964-12-18 1973-06-05 Sylvania Electric Prod Dark coated heater for vacuum tube cathode
US3765939A (en) * 1972-05-10 1973-10-16 Gte Sylvania Inc Method of coating cathode heaters

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1017292B (en) * 1956-07-18 1957-10-10 Telefunken Gmbh Aluminum oxide coating for the heating wire of indirectly heated cathodes of electrical discharge tubes and a method for producing an insulating coating on a heating wire
DE1146594B (en) * 1961-10-31 1963-04-04 Standard Elektrik Lorenz Ag Two-layer insulation coating for the heating element of indirectly heated cathodes of electrical discharge tubes and process for its production
DE1133835B (en) * 1961-12-16 1962-07-26 Telefunken Patent Process for the production of an indirectly heated cathode for an electrical discharge tube
BE626373A (en) * 1961-12-22
NL281567A (en) * 1962-07-30
DE1281038B (en) * 1962-08-01 1968-10-24 Telefunken Patent Process for the production of an indirectly heated cathode for an electrical discharge tube
US3246197A (en) * 1962-10-02 1966-04-12 Westinghouse Electric Corp Cathode heater having an aluminum oxide and tungesten coating
US3500454A (en) * 1967-11-16 1970-03-10 Sylvania Electric Prod Insulator heater coating for heater-cathode assembly

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3029360A (en) * 1958-04-29 1962-04-10 Rca Corp Heater wire coating process
US3195004A (en) * 1960-08-19 1965-07-13 Rca Corp Cathode heater for electron discharge devices
US3372297A (en) * 1964-09-28 1968-03-05 Varian Associates High frequency electron discharge devices and thermionic cathodes having improved (cvd) refractory insulation coated heater wires
US3737714A (en) * 1964-12-18 1973-06-05 Sylvania Electric Prod Dark coated heater for vacuum tube cathode
US3401297A (en) * 1965-08-23 1968-09-10 Varian Associates Thermionic cathodes for electron discharge devices with improved refractory metal heater wires
US3558966A (en) * 1967-03-01 1971-01-26 Semicon Associates Inc Directly heated dispenser cathode
US3531678A (en) * 1968-06-24 1970-09-29 Raytheon Co Heater with boron nitride coating
US3765939A (en) * 1972-05-10 1973-10-16 Gte Sylvania Inc Method of coating cathode heaters

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4079164A (en) * 1975-11-07 1978-03-14 Hitachi, Ltd. Base metal plate for directly heated oxide cathode
US4208208A (en) * 1977-11-18 1980-06-17 Hitachi, Ltd. Nickel alloy base metal plate for directly heated oxide cathodes

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ES425053A1 (en) 1976-11-16
FR2224866B1 (en) 1978-11-03
NL7404521A (en) 1974-10-08
JPS5513102B2 (en) 1980-04-07
DE2317446B2 (en) 1977-08-18
JPS5052962A (en) 1975-05-10
DE2317446A1 (en) 1974-10-24
GB1461495A (en) 1977-01-13
DE2317446C3 (en) 1983-11-10
BE813271R (en) 1974-10-04
CA1032592A (en) 1978-06-06
FR2224866A1 (en) 1974-10-31
IT1007777B (en) 1976-10-30

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