US1695819A - Activation of filaments - Google Patents

Activation of filaments Download PDF

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Publication number
US1695819A
US1695819A US180252A US18025227A US1695819A US 1695819 A US1695819 A US 1695819A US 180252 A US180252 A US 180252A US 18025227 A US18025227 A US 18025227A US 1695819 A US1695819 A US 1695819A
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United States
Prior art keywords
filaments
filament
carbon
carbonization
temperature
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
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US180252A
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English (en)
Inventor
O'neill George Dean
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.)
Westinghouse Lamp Co
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Westinghouse Lamp 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 NL27012D priority Critical patent/NL27012C/xx
Application filed by Westinghouse Lamp Co filed Critical Westinghouse Lamp Co
Priority to US180252A priority patent/US1695819A/en
Application granted granted Critical
Publication of US1695819A publication Critical patent/US1695819A/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
    • 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
    • H01J9/045—Activation of assembled cathode

Definitions

  • This invention relates to'a method and apparatus for activating thoriated tungsten filaments'for electron emission purposes and more particularly to the carbonization thereof for the purpose of converting the thorium oxide content thereof to thorium metal.
  • One of the objects of the present invention is to avoid the above mentioned difiiculties and which will have a lon commercial life.
  • a further object is to provide a suitable apparatus for carrying out the above objects.
  • the unactivated filaments are -sealed into an envelope in the usual manner and after the tubes have been exhausted, they are filled with a purified gas, such as hydrogen, which contains a vapor of a hydrocarbon.
  • a purified gas such as hydrogen
  • filaments are then flashed and allowed to cool in rapid succession so that the filament attains a temperature of about 2400 K. for a, fraction of a second only at each flashing.
  • a temperature of about 2400 K. for a, fraction of a second only at each flashing is then flashed and allowed to cool in rapid succession.
  • the filament Due to the short period of each flash, there is very little loss of heat, due to radiation to the support wires and the filament is therefore heated substantially to the same temperature throughout its entire length. Oo n 25' sequently, the carbonization proceeds substantially uniform throughout the length of the filament. While the filament is being heated from approximately 200 or 300 K. to around 2200 K. carbon is being deposited thereon at a substantially uniform rate over the entire surface, since between these temperatures, carbon does not react with the tungsten and there is no carbideformation taking place... During the intervalv at which the filament is increasing from about 2200 to 24009 K. and again decreasing to 2200 K. the tungsten reacts with the carbon to form tungsten carbide.
  • the apparatus shown comprises a mainfold 1 to which are attached a number of electron discharge devices" 2 having sealed therein, filaments 3 which .it isdesired to activate.
  • the discharge devices 2 are joined --to the manifold 1 by exhaust tubes 4.
  • a vacuum pump (not shown) isjoined tothe manifold 4 1 by a conduit. -5'through a two-way valve'6.
  • the valve 6 also communicates, through con- However, since the car duits 7 and 8 with a" receptacle 9 containing for instance, ice water. ⁇ Hydrogen, from a line 11, is bubbled through the benzene 9 and saturated with the benzene vapor at the temperature of the cooling medium 10.
  • a reservoir 12 is provided for storage of the carbon vapor containing hydrogen.
  • a reservoir pump (not shown) for exhausting the reservoir 12 prior to emitting the hydrogen thereto, is joined to the reservoir by a connection 13 controlled by a valve 14. If desired, the reservoir may be omitted and the gas led directly from .the mixing chamber 9 to the manifold 1. 4
  • the leading-in wires 15 and 16 for each of the filaments are connected through a resistance 17 and a make-and-break device 18 with a source of current 19
  • the makeand-break device 18 is operated intermittently by a cam 20 driven by any suitable motor 21.
  • the operation of the apparatus is as follows. After the apparatus is sealed to the exhaust manifold 1 the valve 6 is adjusted so as to close off the hydrogen-line 7 and open the exhaust pump connection- 5 so as to exhaust the tubes. At the same time, the res-- .ervoir 12 may be exhausted by the reservoir pump through the valve 14. After the envelopes 2 have been exhausted, hydrogen bubbled through the benzene 9 is admitted to the envelopes at approximately atmospheric pressure from the reservoir 12, and
  • the frequency of the flashing may be varied within wide limits but I have obtained excellent results flashing the filament about once each second.
  • the motor 21 operated to flash the filaments flashes will be required, as will also be the' case when the partial pressure of the hydrocarbon is increased.
  • employing benzene vapor mixed at a temper the hydrocarbon taken up by will be suificiently constant and such that.
  • the partial" pressure of when the hydrogen is employed at approximately atmospheric pressure it will contain a sufficient quantity of the hydrocarbon vapor to effect the carbonization of the filament.
  • Method of activating thoriated. tungsten filaments comprising iutermittentl 1ncandescing said filaments in a carbon earing atmosphere.
  • Method of activating thoriated tung. sten filaments comprising momentarily an intermittently heating said filaments to a carbonizing temperature in a carbon bearing atmosphere until the desired carbonization is effected.
  • Methodof activating thoriated tungsten filaments comprising repeatedly heating the filaments momentarily to a temperature of about 2400 K. in the vapor of a hydrocarbon.
  • Method the hydrogenof activating thoriated tungsten filaments comprising repeatedly heating the filaments for a fraction of asecond to a temperature of about 2400 K. in a gas containing a carbonaceous material.
  • Method of activating thoriated tungsten filaments comprising heating the filaments to incandescence in a gaseous atmospherecontaining a small pressure of a vapor of a carbonaceous material.
  • Method of activating thoriated tungsten filaments comprising alternately depositing carbon substantially uniformly thereon and heating to a sufiiciently high temperature to cause a reaction between said carbon and the filaments.
  • Method of activating thoriated tungsten filaments comprising alternately heating the filaments'in a carbon vapor at a tem-' perature sufficiently high to effect a deposition of carbon thereon, without carbonization of the filament, and at a temperature sufliciently high to :eifect such carbonization.
  • Method of activating thoriated tungsten filaments comprising heatingthe filaments to below about 2200' K. in a "carbon bearing atmosphere to deposit carbon thereon and increasing the temperature of the filament above about 2200 K. to eflect a com-- bination of the carbon with the filament material.
  • Method of activating thoriated tungsten filaments comprising heating the filaments to below about 2200 K. in a carbon bearing atmosphere to deposit carbon there-. on and increasing the temperature of the filament above about 2200 K. to eifect a combination of the carbon with,the filament material, said latter temperature being maintained only for a brief interval.
  • Apparatus for carbonizing filaments comprising an enclosure for the filaments, means for supplying a carbon bearing atmosphere thereto, and means for intermittently and momentarily supplying a source of current to the filaments to heat the same to incandescence.
  • Apparatus for carbonizing filaments 1 comprising an enclosure for the filaments,

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
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US180252A 1927-04-01 1927-04-01 Activation of filaments Expired - Lifetime US1695819A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
NL27012D NL27012C (en)) 1927-04-01
US180252A US1695819A (en) 1927-04-01 1927-04-01 Activation of filaments

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Application Number Priority Date Filing Date Title
US180252A US1695819A (en) 1927-04-01 1927-04-01 Activation of filaments

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US1695819A true US1695819A (en) 1928-12-18

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2420014A (en) * 1944-04-18 1947-05-06 Eitel Mccullough Inc Cathode
US2456761A (en) * 1947-04-19 1948-12-21 Eitel Mccullough Inc Rugged cathode
US2658844A (en) * 1952-08-30 1953-11-10 Rca Corp Process of carburizing
US2693431A (en) * 1948-01-27 1954-11-02 Eitcl Mccullough Inc Method of making electron emitters
US2788289A (en) * 1951-06-29 1957-04-09 Climax Molybdenum Co Method of forming protective coatings for molybdenum and molybdenum-base alloys

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2420014A (en) * 1944-04-18 1947-05-06 Eitel Mccullough Inc Cathode
US2456761A (en) * 1947-04-19 1948-12-21 Eitel Mccullough Inc Rugged cathode
US2693431A (en) * 1948-01-27 1954-11-02 Eitcl Mccullough Inc Method of making electron emitters
US2788289A (en) * 1951-06-29 1957-04-09 Climax Molybdenum Co Method of forming protective coatings for molybdenum and molybdenum-base alloys
US2658844A (en) * 1952-08-30 1953-11-10 Rca Corp Process of carburizing

Also Published As

Publication number Publication date
NL27012C (en))

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