US2241345A - Electron emissive cathode - Google Patents

Electron emissive cathode Download PDF

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Publication number
US2241345A
US2241345A US215578A US21557838A US2241345A US 2241345 A US2241345 A US 2241345A US 215578 A US215578 A US 215578A US 21557838 A US21557838 A US 21557838A US 2241345 A US2241345 A US 2241345A
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US
United States
Prior art keywords
discharge
electrodes
envelope
core
electrode
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
US215578A
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English (en)
Inventor
Daniel S Gustin
George A Frecman
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CBS Corp
Original Assignee
Westinghouse Electric and Manufacturing Co
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 NL65805D priority Critical patent/NL65805C/xx
Application filed by Westinghouse Electric and Manufacturing Co filed Critical Westinghouse Electric and Manufacturing Co
Priority to US215578A priority patent/US2241345A/en
Priority to FR856372D priority patent/FR856372A/fr
Priority to GB17928/39A priority patent/GB530176A/en
Application granted granted Critical
Publication of US2241345A publication Critical patent/US2241345A/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
    • H01J61/073—Main electrodes for high-pressure discharge lamps
    • H01J61/0732—Main electrodes for high-pressure discharge lamps characterised by the construction of the electrode

Definitions

  • This invention relates to electric devices of the gaseous conduction type and more particularly to gaseous discharge devices of the high pressure mercury type and to the provision of electrodes therefore.
  • Electrodes consist of a metal provided with a suitable coating, such as barium or strontium carbonates or similar alkaline earth compounds. which material-gives oil. a copious flow of electrons. causing ionization of the rare gas to facilitate starting of the discharge when the electrodes are supplied with electrical energy.
  • Another object of the present invention is the provision of a high pressure gaseous discharge device having electrodes therein between which a discharge occurs upon the application of electrical energy which electrodes comprise a metal from which a copious now of electrons emanate to initiate a discharge, with the electron emissive metal held in place by a refractory material, the latter of which receives the impinging 10 Claims. (Cl. 176-126) would otherwise cause sputtering of the electron emissive component of the electrode.
  • Another object of the present invention is the provision of an electrode for a gaseous discharge device of the high pressure mercury type wherein the electrode is formed of a metal susceptible to a-copious flow of electrons to initiate refractory metal which assumes the discharge after initiation so as to protect the material having high electron emissivity from bombardment dumg operation of the device.
  • Another object of the present invention is the provision of an electrode for a gaseous discharge device of the high pressure mercury type having a core of material susceptible to a copious flow of electrons whichis'surrounded by a helix of refractory metal, thus forming openings for the egress of electrons from the core and shielding the core from bombardment during operation of the device.
  • a further object of the present invention is the provision of an electrode having a core of a metal in the free state susceptible to a copious flow of electrons surrounded by a helix of refractory metal to form openings for the egress of electrons from the core, and for the. purpose of high pressure mercury type constructed in accordance with the present invention.
  • Fig. 2 is a fragmentary view in cross-section and on an enlarged scale showing one embodiment of the electrode forming the subject matter of the present invention.
  • Fig. 3 is a sectional view taken on the line III-III of Fig. 2.
  • Fig. 4 is an elevational view partly in crosssection of a modification of the electrode assembly as shown in Fig. 2.
  • Fig. 5 is a sectional view taken on the line V--V of Fig. 4.
  • Fig. 6 is an elevational view showing a part of the electrode as shown in Fig. 4.
  • a gaspositive ions resulting from the discharge that eous discharge device of the high pressure cury type is shown in Fig. 1 which comprises an envelope 5 of quartz or hard glass having a high melting point so as to withstand the operating temperatures of the lamp.
  • a pair of electrodes 6 and I are disposed therein at opposite ends of the envelope and are supported by leading-in conductors 8 and 9.
  • an ionizable medium such as mercury vapor
  • an ionizable medium such as mercury vapor
  • a small quantity of rare gas may be introduced to facilitate starting.
  • the electrodes 6 and 1 may be of identical construction, and by reference to Fig. 2 they comprise a core 9 of a suitable thermionically active metal, as distinguished from metallic oxides or their other metallic compounds, such as thorium or a metal of the thorium group, which gives off a copious flow of electrons when heated to a comparatively low temperature.
  • a suitable thermionically active metal as distinguished from metallic oxides or their other metallic compounds, such as thorium or a metal of the thorium group, which gives off a copious flow of electrons when heated to a comparatively low temperature.
  • a suitable thermionically active metal as distinguished from metallic oxides or their other metallic compounds, such as thorium or a metal of the thorium group, which gives off a copious flow of electrons when heated to a comparatively low temperature.
  • a material such as tungsten or other refractory metal 10, having a lower electron emissivity than that of the core at the operating temperatures of the device
  • the partially covering refractory metal is in the form of a helix ID with adjacent turns slightly spaced from each other so as to provide openings for the egress of electrons from the coreof high electron emissive metal.
  • the refractory metal may be in the form of a cylinder in contact with the outer surface of the core and provided with openings or grooves for the emission of electrons from the high electron emissive core.
  • the electrode thus formed is supported by th leading-in conductor 8 sealed through the envelope 5, and the inner end thereof may be welded or otherwise affixed to the electrode, although in the preferred embodiment the leading-in conductor is shown concentric with the helixof refractory metal and in contact with the latter and thecore of high electron emissive metal 9, as can be more clearly seen inFig.-3.
  • the electrodes Upon the initial application of electrical energy to the electrodes they are substantially cold and the resulting glow discharge therebetween is the result of the impression of a potential upon the electrodes in excess of the so-called breakdown voltage of the specific gas at the particular gas pressure employed and with the specific electrode spacings used.
  • the electrodes are subjected to ion bombardment and become incandesced thereby.
  • the core of thermionically active metal such as thorium, gives off a copious flow of electrons which initiates an arc discharge betwen the electrodes.
  • the refractory -metal such as tungsten
  • the refractory -metal partially covering the thorium functions as a shield protecting the material of higher electron emissivity from positive ion bombardment during operation of the device, despite the fact that the thorium naturally continues to give off electrons.
  • the core material of thorium not only has a high electron emissivity at the operating temperatures of the devices, but in addition it is protected by the surrounding helix of tungsten assuming the discharge, with the result that no sputtering of the thorium occurs which would otherwise deleteriously afiect the envelope with a resulting de crease in the efficiency of both the visible and invisible radiations generated, inasmuch as such radiations would be absorbed by the envelope 5 instead of being transmitted therethrough.
  • the core material of thorium since the core material of thorium is in its free state, it has no chemical effect on silica and a quartz or other hard glass envelope may be used without frosting, even should there 10 be a slight sputtering of the thorium.
  • sputtering is, as a matter of fact, substantially eliminated.
  • an electrode as above described may be employed, and in order to increase the current carrying capacity, as well as the heat dissipating characteristics of the electrode, it is only necessary to increase the amount of the refractory metal surrounding the core of therminonically active metal of thorium.
  • an additional helix 1! such as, shown in Fig. 6, formed of tungsten is accordingly threaded upon the helix ill of tungsten, as shown in the electrode of Fig. 2.
  • this increasing in current carrying. capacity and heat dissipating characteristics of the electrode may be made byscrewing on the outer helix, as shown in Figs. 4., 5 and 6, during the original assembly of the electrode and prior to its insertion and sealing into the envelope of the device.
  • the leading-in conductor 8 is provided with a cross-bar l3 to which is welded or otherwise amxed a looped support ll to which the thorium 9 and helices I0 and I2 of tungsten are secured.
  • a further advantage of an electrode constructed in the manner of the present invention resides in the fact that no treating previous to sealing of the electrode into the envelope is required and extreme precautions are unnecessary to prevent contamination from the atmosphere as is common in electrodes of the prior art employing barium or strontium carbonates or other alkaline earth compounds to prevent such contamination.
  • a gaseous discharge device of the high pressure mercury type is herein provided.
  • metallic electrodes which have a high electron emissivity to initiate the discharge and which are so constructed that the portion thereof having the high electron emissive characteristics is so protected or shielded from bombardment that sputtering of the electrode with frosting, or other deleterious effects, to the envelope is eliminated.
  • a high pressure discharge device comprising an enclosing envelope, an ionizable medium therein, and a pair of electrodes in said'envelope between which an arc discharge occurs during operation of said device, at least one of said electrodes comprising a metal having a high melting and vaporization point, together with high electron-emissive properties when heated to initiate anarc discharge at low applied voltage, and a refractory metal of higher work function shielding said electron-emissive metal from positive ion bombardment to prevent sputtering of the latter duringoperationof said device.
  • a high pressure dischargedevice comprising an enclosing envelope, an ionizable medium therein, and a pair of electrodes in said envelope between which an arc discharge occurs during operation of said device, at least one of said electrodes comprising a core of metal having a high meltin and vaporization point and substantially constant high electron-emitting properties when heated by the ensuing glow discharge to emit a copious flow of electrons and initiate an arc discharge at low applied voltage, and a refractory metal of higher work function shielding said metallic core from positive ion bombardment to prevent sputtering of the latter during operation of said device.
  • a high pressure discharge device comprising an enclosing envelope, an ionizable medium therein, and a pair of electrodes in said envelope between which an arc discharge occurs during operation of said device, at least one of said electrodes comprising a metal having a high melting and vapprization point, together with substantially constant high electron-emissive properties when heated to initiate an are discharge at low applied voltage, and a refractory metal of higher work function shielding said electron-emissive metal from positive ion bom- 3 bardment to prevent sputtering of the latter during operation and provided with openings therein for the egress of electrons from said electron-emissive metal.
  • a high pressure discharge device comprising an enclosing envelope, an ionizable medium therein, and a pair of electrodes in said envelope between which an arc discharge occurs during operation of said device, at least one of said electrodes comprising a core of metal having a high melting and vaporization point, together with high electron-emitting properties when heated by the ensuing glow discharge to emit a copious flow of electrons and initiate an arc discharge at low applied voltage, and a refractory metal of higher work function surrounding said core and provided with openings for the egress of electrons from the latter when said electrode operates as cathode, and said refractory metal extending longitudinally of said electrode beyond said core in closer proximity to 5 the other of said electrodes for assuming the discharge and for shielding said core from positive ion bombardment when said electrode is operating as anode to prevent sputtering of the core with attendant blackening of the envelope during operation of said device.
  • a high pressure discharge device comprising an enclosing envelope provided with an ionizable medium therein, and a pair of electrodes in said envelope between which an arc discharge occurs during operation of said device, at least one of said electrodes comprising a core of metal having a high melting and vaporization point and operative when heated to emit a copious flow of electrons and initiate a high current are discharge at low applied voltage, and a refractory metal of higher work function surrounding said core and provided with openings for the emission of electrons from the latter when said electrode is operating as cathode, and said refractory metal beingoi sufllcientm'ass to dissipate heat generated by the discharge to maintain the temperature 01' said core below the melting point thereof and extending longitudinally of said electrode in closer proximity to the other electrode than said core forassuming the discharge and for shielding said core from positive ion bombardment when said elec trode is operating as anode.
  • a high pressure discharge device comprising an enclosing envelope provided with'an ionizable medium therein, and a pair of electrodes in said envelope between which an arc discharge occurs during operation of said device, at least one of said electrodes comprising a core of thorium operating when heated to initiate a high current are discharge at low applied voltage, and a helix of tungsten having spaced turns wound around said core to form interstices serving for the egress of electrons from said core during the period when said electrode is operating as cathode, and said helix serving to shield said core from positive ion bombardment to prevent sputtering of the latter when said electrode is operating as anode.
  • An electrode for a high pressure discharge device operable at commercial potentials during the entirelife of said device to initiate and sustain an arc discharge without causing blackening of the envelope of said device
  • a core of thorium having a high melting and vaporization point and substantially constant electron emissive properties when heated by the ensuing glow discharge to emit a copious flow of electrons and initiate an arc discharge at low applied voltage during the entire life of said device, and a helix of tungsten surrounding said thorium core and forming interstices for the egress of electrons from said thorium core and for shielding said thorium core from positive ion bombardment to prevent sputtering thereof during operation of said device.
  • a high pressure discharge device comprising an enclosing envelope, an ionizable medium therein, and a pair of electrodes in said envelope between which an arc discharge occurs during operation of said device, at least one of said electrodes being a non-activated electrode comprising a metal having a high melting and vaporization point together with high electronemissive properties when heated to. initiate and sustain a high pressure are discharge at low applied voltage, and means to prevent sputtering of said non-activated electrode during operation of said device.
  • a high pressure discharge device comprising an enclosing envelope, a pair of electrodes in said envelope adapted to carry the discharge current, at least one of said electrodes being a non-activated electrode of high melting and vaporization point comprising a metal of the thorium group having high constant, electronemitting properties when heated, an ionizable medium in said envelope comprising a starting gas ionizable at low applied voltage to produce a glow discharge with attendant heating of said electrodes by positive ion bombardment and to cause the initiation of a high pressure are discharge at the low applied voltage, and a vaporizable material in sufficient quantity to become vaporized by the application of electrical energy to the electrodes to sustain said are discharge at the resulting high pressure of the ionizable medium.
  • a high pressure discharge device comprising an enclosing envelope, 9. pair of electrodes in said envelope adapted to carry the discharge current. at least one of said electrodes comprising a non-activated electrode of high melting and vaporization point and having high constant electron-emitting properties when heated and provided with a portion for concentrating the arc discharge thereon to protect the remainder of the electrode mass from the direct action of the arc discharge, an ionizable medium in said envelope comprising a starting gas ionizable at low applied voltage to produce a glow discharge with attendant heating or said electrodes by positive ion bombardment and to cause the initiation of a high pressure arc discharge at the low applied voltage, and a vaporizable material in suflicient quantity to become vaporized upon the application of electrical energy to the electrodes to sustain said arc discharge at the resulting high pressure of the ionizable medium.

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  • Discharge Lamp (AREA)
US215578A 1938-06-24 1938-06-24 Electron emissive cathode Expired - Lifetime US2241345A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL65805D NL65805C (zh) 1938-06-24
US215578A US2241345A (en) 1938-06-24 1938-06-24 Electron emissive cathode
FR856372D FR856372A (fr) 1938-06-24 1939-06-15 Cathode émettrice d'électrons
GB17928/39A GB530176A (en) 1938-06-24 1939-06-20 Improvements in or relating to electric discharge devices

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US215578A US2241345A (en) 1938-06-24 1938-06-24 Electron emissive cathode

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US2241345A true US2241345A (en) 1941-05-06

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US (1) US2241345A (zh)
FR (1) FR856372A (zh)
GB (1) GB530176A (zh)
NL (1) NL65805C (zh)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2477279A (en) * 1946-09-11 1949-07-26 Hanovia Chemical & Mfg Co Electrical discharge device
US2629065A (en) * 1948-05-14 1953-02-17 Westinghouse Electric Corp Overwound filament
US2667592A (en) * 1951-01-11 1954-01-26 Hanovia Chemical & Mfg Co Electrode for compact type electrical discharge devices
US2682007A (en) * 1951-01-11 1954-06-22 Hanovia Chemical & Mfg Co Compact type electrical discharge device
US2727169A (en) * 1950-03-22 1955-12-13 Gen Electric Thermionic electrode pulse lamp structure
DE962461C (de) * 1950-12-18 1957-04-25 Dr Hermann E Krefft Gluehelektrode fuer elektrische Hochdruck- und Hoechstdruck-Entladungslampen

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2477279A (en) * 1946-09-11 1949-07-26 Hanovia Chemical & Mfg Co Electrical discharge device
US2629065A (en) * 1948-05-14 1953-02-17 Westinghouse Electric Corp Overwound filament
US2727169A (en) * 1950-03-22 1955-12-13 Gen Electric Thermionic electrode pulse lamp structure
DE962461C (de) * 1950-12-18 1957-04-25 Dr Hermann E Krefft Gluehelektrode fuer elektrische Hochdruck- und Hoechstdruck-Entladungslampen
US2667592A (en) * 1951-01-11 1954-01-26 Hanovia Chemical & Mfg Co Electrode for compact type electrical discharge devices
US2682007A (en) * 1951-01-11 1954-06-22 Hanovia Chemical & Mfg Co Compact type electrical discharge device

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Publication number Publication date
NL65805C (zh)
GB530176A (en) 1940-12-06
FR856372A (fr) 1940-06-12

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