US3911309A - Electrode comprising a porous sintered body - Google Patents

Electrode comprising a porous sintered body Download PDF

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Publication number
US3911309A
US3911309A US396446A US39644673A US3911309A US 3911309 A US3911309 A US 3911309A US 396446 A US396446 A US 396446A US 39644673 A US39644673 A US 39644673A US 3911309 A US3911309 A US 3911309A
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Prior art keywords
zone
sintered
electrode
percent
tungsten
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US396446A
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English (en)
Inventor
Ulrich Kummel
Manfred Mair
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Osram GmbH
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Patent Treuhand Gesellschaft fuer Elektrische Gluehlampen mbH
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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
    • H01J61/073—Main electrodes for high-pressure discharge lamps
    • H01J61/0732—Main electrodes for high-pressure discharge lamps characterised by the construction of the electrode

Definitions

  • the first zone consists of a refractory material I UNlTED STATES PATENTS which has been sintered at a temperature higher than 2,492,142 12/1949 Gcrmeshausen 313/346 R the temperature of the arc discharge to form a 2 83(),218 4/1958 Bcggs 313/346 R tered interconnected porous material.
  • the second 2,975,322 3/1961 Cockrill 313/346 R zone consists of a sintered porous mixture of refrac- 3,()l0,046 ll/l96l Dailcy et al 313/346 R tory material and emissive materiaL 3,076,915 2/1963 Gal et al. 313/346 R 2 3,244,929 4/1966 Kuhl 313/346 R X 21 Claims, 2 Drawin Flgul'es US. Patent Ot. 7,1975 3,911,309
  • FIG. 2
  • Electrodes having a sintered body are known.
  • British Pat. No. 943,535 discloses a porous cathode body composed of tungsten which is saturated with an emissive substance.
  • the cathode body also contains a second emissive substance having a lower electron work function disposed in recesses of the surface facing the arc discharge. This second emissive substance is used for initiation of the arc discharge.
  • US. Pat. No. 3,244,929 discloses a sintered electrode body composed of several zones formed from different emissive mixtures. These mixtures are compressed and sintered about an electrode rod.
  • the zones of higher electron work function and heat resistance are provided in the direction of the space which contains the discharge arc during operation.
  • the zones having a, lower electron work function are positioned away from the space adapted to be occupied by the arc discharge during operation, i.e., the zones of lower work function are at the other side of the electrode.
  • the emissive characteristic of an electrode which are most satisfactory during operation of the arc discharge are different from the emissive characteristics which are most satisfactory for initiating said are discharge.
  • the aforedescribed prior art constructions provide electrodes having at least two surfaaces having different emissive characteristics, one more suitable for initiation of the arc, and the other more suitable for operation of the arc.
  • the present invention provides an improved electrode for discharge lamps having superior characteristics for initiation of the arc and operation of the are.
  • the present invention provides a sintered electrode for use in gaseous and/or vapor discharge lamps and, particularly, high-pressure lamps.
  • the sintered electrode contains a central electrode rod having one portion substantially enclosed by two contiguous porous sintered zones each of which has an exposed outer surface.
  • the exposed outer surface of the first zone is positioned in the direction of the electric arc discharge during operation of the lamp and in closer proximity thereto during operation than the outer surface of the second zone.
  • the first zone consists of a sintered interconnected porous refractory material which has been sintered at a higher temperature than the temperature reached during service of the discharge lamp, i.e., at a higher temperature than the temperature of the are discharge proximite the electrode surface.
  • the second zone consists of a sintered mixture of refractory material and emissive material.
  • Both zones may be formed by sintering high temperature refractory metals, e.g., tungsten, or high temperature refractory metallic compounds, e.g., zirconium carbide, lanthanum boride, etc.
  • high temperature refractory metals e.g., tungsten
  • high temperature refractory metallic compounds e.g., zirconium carbide, lanthanum boride, etc.
  • the first zone which does not contain emissive material during preparation of the electrode has a density of between 8 and 16 grams per cubic centimeter when using tungsten as the refractory material.
  • the preferred density is from 10 to 14 grams per cubic centimeter.
  • the second sintered zone contains an emissive substance with the refractory material.
  • the relative amounts, for example of a refractory material such as tungsten, and the emissive material vary from about 30 .to percent by weight of refractory material to about 70 to 30 percent by weight of the emissive material. The percent by weight is based on the total.
  • the preferred ratio is 50-+50 weight percent of each.
  • the emissive material or substance includes those known to the prior art to be suitable for this purpose, such as the oxides of barium, calcium and thorium, and
  • the first zone has a sintered structure of interconnected pores.
  • the second 'zone which is contiguous with the first zone has a refractory metal skeleton and contains emissive material in interconnected pores. Because of the contiguous relationship of the two zones, the emissive material from the second zone flows into the outer first zone and to the surface thereof during operation. This prevents sputtering of the refractory material at the position or positions at which the arc discharge appends during operation of the lamp:
  • the terms appends and appended refer to the position at which the arc discharge makes contact with the sur face of the electrode during operation of the lamp and alsothe position at which contact is made during ig nition of the lamp.
  • the arc apperidsto the second zone during initiation of the discharge and occurs immediately when the arc strikes or forms.
  • The are appends to the outer surface of the first zone during operation of the lamp.
  • the second zone is positioned within a cavity of the first zone which is shaped as a cap over the second zone.
  • the outer surface of the firstzone i.e., the cap, may have such shapes. as a cylindrical. surface, a conical surface or a frustoconical shape.
  • the opening of. the cap in which the second zone material is encompassed faces away from the direction of the arc discharge during operation of the lamp.
  • the electrode rod which is preferably centrally positioned in the sintered electrode either protrudes with its end extending through the cap-shaped first zone in the direction of the arc discharge during operation, or it may terminate with the cap-shaped zone.
  • This preferred embodiment provides a second zone for initiation of the are having an exposed surface of large area extending in the direction away from the arc discharge during operation.
  • FIG. 1 is a section through one preferred embodiment of the electrode
  • FIG. 2 is a section through another preferred embodiment of the electrode.
  • the electrode rod 1 of thoriated tungsten having a diameter of 1.2 mm projects with its tip 2 approximately 1.5 mm out of the sintered body 3.
  • the sintered body 3 is of cylindrical shape. Its length of about 5 mm is slightly larger than its diameter. It comprises a first zone 4 and a second zone 5.
  • the first zone 4 has the shape of a cylindrical cap with bell-shaped cavity 6. It is made of finely sintered porous tungsten with a density of 12 g/cc. The cavity is almost completely filled with a sintered emissive mixture of 50 wt. percent of tungsten and 50 wt. percent of a mixture of oxides of barium, calcium, and thorium which forms the second zone 5.
  • the outer surface 7 of the first zone 4 within the lamp is located more closely to the discharge than the outer surface 8 of the second zone 5.
  • the first zone 4 has the shape of a conical cap 9.
  • the electrode rod 1 terminates with its tip 2 within the surface boundary of cap 9.
  • the sintered electrodes of the present invention are advantageous prepapred using powder metallurgic techniques.
  • the first electrode zone has particularly superior mechanical and high temperature properties.
  • the sintered material having interconnected pores is suitably prepared by admixing the refractory material, e.g., tungsten, or zirconium carbide, with a powdered material which will not alloy with the refractory material and which has a sufficiently low boiling point so that it will vaporize during sintering.
  • Suitable low temperature materials include zinc, copper, gold, etc.
  • zinc is particularly suited as the low boiling point material because it additionally functions as a pressing aid during the pressing of the shaped body.
  • the mixture of the refractory material and the low boiling point material is pressed to the desired shape using conventional powder metallurgical techniques.
  • the electrode rod may be pressed into the sintered body at the same time.
  • the slug is sintered at a temperature above the vaporization temperature of the low boiling point material.
  • the low boiling material evaporates leaving a sintered, porous, skeletal structure which is then subjected to a higher temperature sintering, with temperatures up to 2600C.
  • the high degree of porosity and the interconnected porous structure is maintained during such high temperature sintering.
  • the second zone is prepared utilizing a powder mixture of the refractory material, e.g., a metal such as tungsten, and the emissive material.
  • This powder mixture may be attached to the first zone.
  • the powder mixture of the second zone material may be introduced into the cavity of the first zone and the two sintered together at a lower temperature of up to about 2000C. This forms the emitter-containing second zone.
  • the sintering may be in two sequential steps as aforedescribed, or in a single 'sintering wherein the evaporation of the low boiling point material and the final sintering are achieved in a single continuous sintering operation.
  • sintered electrodes when compared with wire coil electrodes is that the sintered electrodes are cheaper and more simple to manufacture.
  • their stability at high electrical and thermal loads has been insufficient to attain a warranted lifetime of more than 5000 hours. Accordingly, they were not used in lamps with a wattage input exceeding 125 watts.
  • the electrodes of the present invention have superior service characteristics and are suitable for use in discharge lamps with a wattage input of 400 watts and even higher. This is possible because the high sintering temperature not only improves the mechanical properties and high temperature stability of the porous structure, but also improves the electrical conductivity thereof. As noted, the high temperature at which the first zone of the electrode is sintered results in a structure having high temperature stability without sintering resulting in closing of the pores even with a high load. As a consequence, the supply of successive doses of emissive material to the surface of the first zone from the second zone is assured during operation.
  • the sintering temperature of the first zone preferably ranges be tween 2400 and 2600C.
  • the sintering temperature of the second zone which includes emissive material of preferably barium oxide 19.5 percent by wt., calcium oxide 5.5 and thorium oxide 75.0 is between l600 and 2()OOC.
  • a sintered electrode for discharge lamps adapted to operate with an electric discharge are appended to an outer surface thereof, comprising a central electrode rod having one portion substantially enclosed by first and second contiguous porous sintered zones each of which has an exposed surface, said exposed surface of the said first zone being positioned in the direction of the arc discharge during operation of the lamp and in closer proximity thereto during operation than said exposed surface of said second zone, said first zone consisting of interconnected porous material refractory sintered at a temperature between 2400C and 2600C, and said second zone consisting of a sintered porous mixture of refractory material and emissive material.
  • said emissive material is at least one compound selected from the group consisting of barium oxide, calcium oxide, thorium oxide, and barium cerate.
  • said emissive material is at least one compound selected from the group consisting of barium oxide, calcium oxide, thorium oxide, and barium cerate.
  • a method of manufacturing a sintered electrode for discharge lamps adapted to operate with an electric discharge are appended to an outer surface thereof having a central electrode rod with one portion substantially enclosed by first and second contiguous porous sintered zones each of which has an exposed surface, said exposed surface of the said first zone being positioned in the direction of the arc discharge during operation of the lamp and in closer proximity thereto during operation than said exposed surface of said second zone; comprising admixing a powdered refractory material with a low boiling point material which does not alloy with said refractory material and which vaporizes at the sintering temperature of said refractory material; compressing said admixture in a shaped die around said electrode rod to form a pressed compact surrounding said electrode rod; sintering said pressed compact and electrode rod at a temperature above the vaporization temperature of said low boiling point material whereby said low boiling point material completely vaporizes; and then sintering at a higher temperature up to about 2600C to obtain an interconnected porous first zone substantially enclo
  • said electrode rod is thoriated tungsten
  • said refractory material in said first zone is selected from the group consisting of tungsten, zirconium carbide and lanthanum boride, and said low boiling point material is zinc.
  • said emissive material consists of barium oxide, calcium oxide and thorium oxide, and wherein the final sintering is at a temperature between 1600C and 2000C.

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  • Discharge Lamp (AREA)
US396446A 1972-09-18 1973-09-12 Electrode comprising a porous sintered body Expired - Lifetime US3911309A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2245717A DE2245717A1 (de) 1972-09-18 1972-09-18 Elektrode mit einem poroesen sinterkoerper

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US (1) US3911309A (uk)
JP (1) JPS4970478A (uk)
DE (1) DE2245717A1 (uk)
FR (1) FR2200618B1 (uk)
GB (1) GB1438524A (uk)

Cited By (19)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4097762A (en) * 1975-08-14 1978-06-27 International Telephone & Telegraph Corporation Xenon arc discharge lamp having a particular electrode composition and wherein the arc discharge is obtained without heating the electrode
US4229873A (en) * 1978-09-15 1980-10-28 Bykhovskij David G Method of producing nonconsumable electrode for use in arc techniques
US4246682A (en) * 1977-12-06 1981-01-27 U.S. Philips Corporation Method of making cathode support nickel strip
US4275123A (en) * 1978-05-05 1981-06-23 Bbc Brown Boveri & Company Limited Hot-cathode material and production thereof
US4415835A (en) * 1981-06-22 1983-11-15 General Electric Company Electron emissive coatings for electric discharge devices
US4487589A (en) * 1981-06-22 1984-12-11 General Electric Company Method of preparing electron emissive coatings for electric discharge devices
US4494035A (en) * 1980-11-07 1985-01-15 Thomson-Csf Thermoelectric cathode for a hyperfrequency valve and valves incorporating such cathodes
EP0249196A2 (en) * 1986-06-11 1987-12-16 TDK Corporation Discharge lamp device
EP0253316A2 (en) * 1986-07-15 1988-01-20 TDK Corporation Cold cathode type discharge lamp apparatus
WO1996002062A1 (en) * 1994-07-11 1996-01-25 Rank Brimar Limited Electrode structure
US5774780A (en) * 1994-11-27 1998-06-30 Bayerische Metallwerke Gmbh Process for production of a shaped part
US5844365A (en) * 1996-03-22 1998-12-01 U.S. Philips Corporation High pressure metal halide lamp
EP0917179A2 (de) * 1997-11-11 1999-05-19 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Elektrodenbauteil für Entladungslampen
US5929565A (en) * 1996-02-23 1999-07-27 Ushiodenki Kabushiki Kaisha Short arc discharge lamp having anode with tungsten coating thereon
WO2007135008A2 (de) * 2006-05-22 2007-11-29 Osram Gesellschaft mit beschränkter Haftung Elektrode für eine entladungslampe sowie ein verfahren zum herstellen einer derartigen elektrode
US20100039035A1 (en) * 2006-12-18 2010-02-18 Adam Kotowicz Electrode for a Discharge Lamp
US8018155B2 (en) * 2005-09-02 2011-09-13 Sony Corporation Short arc type high voltage electrical discharge electrode, short arc type high voltage electrical discharge tube, short arc type high voltage electrical discharge light source apparatus, and their manufacturing methods
CN102366837A (zh) * 2011-08-10 2012-03-07 厦门虹鹭钨钼工业有限公司 一种高压气体放电灯用钍钨-钨复合电极的制作方法
WO2019056026A1 (de) * 2017-09-22 2019-03-28 Plansee Se Kathode

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2079036A (en) * 1980-06-20 1982-01-13 Gen Electric Electron emitting coating in metal halide arc lamp
JP5024466B1 (ja) * 2011-03-10 2012-09-12 ウシオ電機株式会社 ショートアーク型放電ランプ

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2492142A (en) * 1945-10-17 1949-12-27 Kenneth J Germeshausen Electric system embodying coldcathode gaseous discharge device
US2830218A (en) * 1953-09-24 1958-04-08 Gen Electric Dispenser cathodes and methods of making them
US2975322A (en) * 1958-12-29 1961-03-14 Raytheon Co Indirectly heated cathodes
US3010046A (en) * 1952-02-26 1961-11-21 Westinghouse Electric Corp Cathode structure
US3076915A (en) * 1954-12-24 1963-02-05 Egyesuelt Izzolampa Cathode assembly and method of making same
US3244929A (en) * 1961-01-02 1966-04-05 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Multi-work function cathode
US3558966A (en) * 1967-03-01 1971-01-26 Semicon Associates Inc Directly heated dispenser cathode
US3656020A (en) * 1970-11-18 1972-04-11 Spectra Mat Inc Thermionic cathode comprising mixture of barium oxide, calcium oxide and lithium oxide
US3661536A (en) * 1966-03-11 1972-05-09 Tokyo Shibaura Electric Co Tungsten materials

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3243637A (en) * 1962-10-31 1966-03-29 Gen Electric Dispenser cathode

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2492142A (en) * 1945-10-17 1949-12-27 Kenneth J Germeshausen Electric system embodying coldcathode gaseous discharge device
US3010046A (en) * 1952-02-26 1961-11-21 Westinghouse Electric Corp Cathode structure
US2830218A (en) * 1953-09-24 1958-04-08 Gen Electric Dispenser cathodes and methods of making them
US3076915A (en) * 1954-12-24 1963-02-05 Egyesuelt Izzolampa Cathode assembly and method of making same
US2975322A (en) * 1958-12-29 1961-03-14 Raytheon Co Indirectly heated cathodes
US3244929A (en) * 1961-01-02 1966-04-05 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Multi-work function cathode
US3661536A (en) * 1966-03-11 1972-05-09 Tokyo Shibaura Electric Co Tungsten materials
US3558966A (en) * 1967-03-01 1971-01-26 Semicon Associates Inc Directly heated dispenser cathode
US3656020A (en) * 1970-11-18 1972-04-11 Spectra Mat Inc Thermionic cathode comprising mixture of barium oxide, calcium oxide and lithium oxide

Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4097762A (en) * 1975-08-14 1978-06-27 International Telephone & Telegraph Corporation Xenon arc discharge lamp having a particular electrode composition and wherein the arc discharge is obtained without heating the electrode
US4246682A (en) * 1977-12-06 1981-01-27 U.S. Philips Corporation Method of making cathode support nickel strip
US4275123A (en) * 1978-05-05 1981-06-23 Bbc Brown Boveri & Company Limited Hot-cathode material and production thereof
US4229873A (en) * 1978-09-15 1980-10-28 Bykhovskij David G Method of producing nonconsumable electrode for use in arc techniques
US4494035A (en) * 1980-11-07 1985-01-15 Thomson-Csf Thermoelectric cathode for a hyperfrequency valve and valves incorporating such cathodes
US4487589A (en) * 1981-06-22 1984-12-11 General Electric Company Method of preparing electron emissive coatings for electric discharge devices
US4415835A (en) * 1981-06-22 1983-11-15 General Electric Company Electron emissive coatings for electric discharge devices
EP0249196A2 (en) * 1986-06-11 1987-12-16 TDK Corporation Discharge lamp device
EP0249196A3 (en) * 1986-06-11 1990-04-04 TDK Corporation Discharge lamp device
EP0253316A2 (en) * 1986-07-15 1988-01-20 TDK Corporation Cold cathode type discharge lamp apparatus
EP0253316A3 (en) * 1986-07-15 1990-03-21 TDK Corporation Cold cathode type discharge lamp apparatus
US5874805A (en) * 1994-07-11 1999-02-23 Digital Projection Limited Electrode structure including a rod comprising refractory metal and having a greater thermal conductivity material
WO1996002062A1 (en) * 1994-07-11 1996-01-25 Rank Brimar Limited Electrode structure
US5774780A (en) * 1994-11-27 1998-06-30 Bayerische Metallwerke Gmbh Process for production of a shaped part
US5929565A (en) * 1996-02-23 1999-07-27 Ushiodenki Kabushiki Kaisha Short arc discharge lamp having anode with tungsten coating thereon
US5844365A (en) * 1996-03-22 1998-12-01 U.S. Philips Corporation High pressure metal halide lamp
EP0917179A2 (de) * 1997-11-11 1999-05-19 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Elektrodenbauteil für Entladungslampen
EP0917179A3 (de) * 1997-11-11 1999-05-26 Patent-Treuhand-Gesellschaft für elektrische Glühlampen mbH Elektrodenbauteil für Entladungslampen
US6211615B1 (en) 1997-11-11 2001-04-03 Patent-Truehand-Gesellshaft Fuer Elektrische Gluelampen Mbh Powder metal electrode component for discharge lamps
US8018155B2 (en) * 2005-09-02 2011-09-13 Sony Corporation Short arc type high voltage electrical discharge electrode, short arc type high voltage electrical discharge tube, short arc type high voltage electrical discharge light source apparatus, and their manufacturing methods
WO2007135008A3 (de) * 2006-05-22 2008-01-24 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Elektrode für eine entladungslampe sowie ein verfahren zum herstellen einer derartigen elektrode
US20090121634A1 (en) * 2006-05-22 2009-05-14 Osram Gesellschaft Mit Beschrankter Haftung Electrode for a Discharge Lamp and a Method for Producing Such an Electrode
WO2007135008A2 (de) * 2006-05-22 2007-11-29 Osram Gesellschaft mit beschränkter Haftung Elektrode für eine entladungslampe sowie ein verfahren zum herstellen einer derartigen elektrode
US20100039035A1 (en) * 2006-12-18 2010-02-18 Adam Kotowicz Electrode for a Discharge Lamp
US8138662B2 (en) * 2006-12-18 2012-03-20 Osram Ag Electrode for a discharge lamp
CN102366837A (zh) * 2011-08-10 2012-03-07 厦门虹鹭钨钼工业有限公司 一种高压气体放电灯用钍钨-钨复合电极的制作方法
WO2019056026A1 (de) * 2017-09-22 2019-03-28 Plansee Se Kathode

Also Published As

Publication number Publication date
DE2245717A1 (de) 1974-03-28
GB1438524A (en) 1976-06-09
FR2200618B1 (uk) 1977-02-25
FR2200618A1 (uk) 1974-04-19
JPS4970478A (uk) 1974-07-08

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