US3510190A - Method of treating an electrode,of which at least one portion contains thorium oxide in its surface - Google Patents

Method of treating an electrode,of which at least one portion contains thorium oxide in its surface Download PDF

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Publication number
US3510190A
US3510190A US612506A US3510190DA US3510190A US 3510190 A US3510190 A US 3510190A US 612506 A US612506 A US 612506A US 3510190D A US3510190D A US 3510190DA US 3510190 A US3510190 A US 3510190A
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Prior art keywords
electrode
electrodes
treating
thorium oxide
discharge
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Expired - Lifetime
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US612506A
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English (en)
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Andre Taxil
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Claude Paz et Visseaux SA
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Claude Paz et Visseaux SA
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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
    • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
    • H01J9/042—Manufacture, activation of the emissive part

Definitions

  • the invention re ates to a method of treating an electrode, of which at least one portion contains thorium oxide in its surface, by heating in an atmosphere containing a hydrocarbon.
  • One object of the invention is to provide a method for carburizing thoriated electrodes, which method is simple to carry out and also effects the sintering of the emissive deposit when the manufacture of the electrode comprises such sintering.
  • Another object of the invention is to provide a method for carburizing thoriated electrodes intended to operate in an ionisable atmosphere.
  • a feature of the invention is to provide a method for carburizing thoriated electrodes, which method comprises the passage of an electric arc discharge between two electrodes, one of which is the electrode to be treated, the atmosphere for this discharge containing hydrocarbon at a partial pressure of the order of a millimetre of mercury.
  • FIG. 1 shows a device for carrying out the method of the invention.
  • FIG. 2 shows a discharge lamp provided with two electrodes according to the invention.
  • FIGS. 3, 4, 5 and 6, respectively, show four other-electrodes which have undergone the method of treatment according to the invention.
  • the electrode treated in the device of FIG. 1 is intended for a 400-watt lamp operating by discharge in an atmosphere under pressure containing mercury and halides; it conforms to French Pat. No. 1,464,066.
  • This electrode is composed essentially of:
  • a helix 6 comprising approximately seven contiguous or almost contiguous turns, consisting of a tungsten filament 0.5 mm. in diameter;
  • Patented May 5, 1970 ice A coating 8 on the helix and on the neighbouring zones of the rod 4, more particularly its end, this coating being composed of equal weights of thoria powder and of thorium powder and a little temporary binder.
  • the electrode is held by its stem in a resilient collet 10 and is enclosed with a bell 12 having a branch 14, in which bell there is sealed a tungsten rod 16.
  • the bell is, for example, made of borosilicate glass, called Pyrex.
  • the electrode -4, 6, 8 and the rod 16 are connected respectively to the poles of a direct-current or alternating-current source of appropriate voltage and in series with a resistance.
  • an arc discharge is produced.
  • the current source and the resistance in series therewith are such that the discharge has a current of 8 amperes.
  • a discharge of about 12 amperes would be passed; this electrode is intended, for example, for a Z-kilowatt lamp supplied by a 380-volt alternating-current source.
  • This discharge is passed for about twenty seconds while the e ectrode 4, 6, 8 is moved, so that the cathode spot is successively produced on all the points of the deposit 8.
  • the spot brings the point at which it is formed to about 2000 C., whereby the thoria and the thorium are converted into a ceramic and the binder is eliminated at this point; since the cathode spot is highly localised and this stage of the treatment is short, the mass of the electrode does not by far reach this temperature.
  • the electrode After this discharge, the electrode is allowed to cool for about one minute in argon without naphthalene. Thereafter, the arc discharge is renewed and accompanied by displacements of the electrode to be treated, but in argon without naphthalene, except in involuntary traces. At the end of about twenty seconds, the electric discharge is extinguished and, after argon without naphthalene has been passed through for one minute, whereby the electrode is cooled, the bell is removed and the electrode is withdrawn from its collet 10.
  • Two electrodes intended for a 2-kilowatt 380-volt lamp treated as described with reference to the drawings were fitted in a manner known for high-pressure mercury vapour lamps, in a silica tube of a diameter of 30 mm.; the distance between these electrodes, called main electrodes, was mm.
  • FIG. 2 illustrates a lamp of this type with two main electrodes 20, 22 but a single auxiliary electrode 24.
  • the discharge tube 26 is surrounded in known manner by an envelope 28, which is exhausted. There is shown at 30 the mercury and at 32 a spot formed by the halides before the lamp has been put into operation.
  • the method of the invention may be carried out in manners different from that described in the foregoing.
  • the naphthalene may 'be replaced by a more volatile hydrocarbon, the vapour pressure of which may, if desired be lowered by cooling. Conversely, the naphthalene may be replaced by a less volatile hydrocarbon, which is heated if the vapour pressure is found to be insuflicient. The discharge in an atmosphere containing this hydrocarbon may also be maintained for a longer time. It is also possible to employ a number of hydrocarbons simultaneously.
  • the treated electrode may be different both in the composition of the mixture containing the thorium oxide and in the metallic support for this mixture.
  • a helix 6 having noncontiguous turns for increasing the quantity of emissive products.
  • the mixture may comprise other proportions of thoria and thorium. It may contain other constituents, for example silica.
  • all or part of the portion whose surface contains thorium oxide may be surrounded, after the treatment, with a metallic member not comprising any emissive material, but formed with voids, slots or pores, for example. Electrons will pass through these voids, as also a little metallic thorium, which will activate the said member.
  • the said member is, for example, a second tungsten helix of the same pitch and the same filament diameter as the helix 6.
  • This member protects the emissive deposit from bombardment, reduces the temperature of the electrode during operation and in addition increases the thermal inertia of the electrode and its cooling time, so that no halides are deposited on the electrode during the extinction.
  • the said member consists of a helix 34 or 36 of tungsten filament, screwed onto the helix 6 and extending beyond it in the forward direction (FIG. 3) or t in the rearward direction (FIG. 4).
  • the said member could also extend beyond the helix 6 both in the forward direction and in the rearward direction or not extend beyond it at all.
  • FIGS. 5 and 6 are variants of "FIGS. 3 and 4, in which the helix 6 is replaced by two shorter helices 38, 40, de-
  • a method of treating a thoriated tungsten electrode, of which at least one portion contains thorium oxide in its surface comprising striking an electric arc between two spaced electrodes of which one is the electrode to be treated, and maintaining an atmosphere for the arc containing an inert gas and a small amount of hydrocarbon vapor to carburize said electrode.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Discharge Lamp (AREA)
US612506A 1966-04-18 1967-01-30 Method of treating an electrode,of which at least one portion contains thorium oxide in its surface Expired - Lifetime US3510190A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR57986A FR1489755A (fr) 1966-04-18 1966-04-18 Procédé pour le traitement carburant d'une électrode à l'oxyde de thorium

Publications (1)

Publication Number Publication Date
US3510190A true US3510190A (en) 1970-05-05

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US (1) US3510190A (is")
BE (1) BE693505A (is")
CH (1) CH460186A (is")
FR (1) FR1489755A (is")
GB (1) GB1166927A (is")

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3846006A (en) * 1972-02-24 1974-11-05 Picker Corp Method of manufacturing of x-ray tube having thoriated tungsten filament
US5001397A (en) * 1985-07-17 1991-03-19 U.S. Philips Corporation High-pressure gas discharge lamp having electrodes with coil layers having interlocking turns

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1704981A (en) * 1927-08-26 1929-03-12 Lebrun Paul Francois Joseph Method of preparing luminescent tubes
US2324559A (en) * 1943-04-05 1943-07-20 Machlett Lab Inc Manufacture of vacuum apparatus
US2401040A (en) * 1942-10-05 1946-05-28 Eitel Mccullough Inc Method of making electronic tubes
US2591474A (en) * 1950-05-26 1952-04-01 Raytheon Mfg Co Cold cathode discharge device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1704981A (en) * 1927-08-26 1929-03-12 Lebrun Paul Francois Joseph Method of preparing luminescent tubes
US2401040A (en) * 1942-10-05 1946-05-28 Eitel Mccullough Inc Method of making electronic tubes
US2324559A (en) * 1943-04-05 1943-07-20 Machlett Lab Inc Manufacture of vacuum apparatus
US2591474A (en) * 1950-05-26 1952-04-01 Raytheon Mfg Co Cold cathode discharge device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3846006A (en) * 1972-02-24 1974-11-05 Picker Corp Method of manufacturing of x-ray tube having thoriated tungsten filament
US5001397A (en) * 1985-07-17 1991-03-19 U.S. Philips Corporation High-pressure gas discharge lamp having electrodes with coil layers having interlocking turns

Also Published As

Publication number Publication date
GB1166927A (en) 1969-10-15
BE693505A (is") 1967-08-01
FR1489755A (fr) 1967-07-28
CH460186A (fr) 1968-07-31
DE1589111B2 (de) 1975-10-30
DE1589111A1 (de) 1970-03-19

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