US1850809A - Vacuum electric tube - Google Patents

Vacuum electric tube Download PDF

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Publication number
US1850809A
US1850809A US715653A US71565324A US1850809A US 1850809 A US1850809 A US 1850809A US 715653 A US715653 A US 715653A US 71565324 A US71565324 A US 71565324A US 1850809 A US1850809 A US 1850809A
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US
United States
Prior art keywords
metal
coating
filament
cathode
coated
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Expired - Lifetime
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US715653A
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English (en)
Inventor
Robinson Ernest Yeoman
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Individual
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Individual
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Classifications

    • 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

  • nnunsr ROBINSON, or wrrmueronynuemun I *vAoUuM' merald was I i i no Drawing. Application filed May 24,i1924,'Seria1No. 715553, and in 'GreatBritain irune'lz, 192s;-
  • Thisinvention relates to vacuum electric tubes and partic'ula-rly to electron emitting cathodes of, the oxide coated "type.
  • These cathodes of say platinum or Iplatinum-iridb "5 um are usuallyco'ated withoxides of calcium, barium? or strontium for 'exa1nple,'or a; mixture of such oxldes,
  • a com-' mon method is toapply acoating of a compound of the metal, usually the nitrate, with an organic binder, by paintingor dipping the cathode; which binder is subsequently re moved byheat-ing in an oxidizing atmosphere and the compound decomposed to the.,ox1de.
  • an I electronemittingycathode of the typeabove referred to is produced in the follovvin'gynuanner.
  • c cathode isfirstcoated'with the metal, or a mixture of the ymetals, otthe compounds which form the electron-emitting coatings, and; the *metal surface is then converted to the compound desiredby suitable means.
  • a cathodevconsisting of a sheet For instance, a cathodevconsisting of a sheet,
  • wire or-filament ofrsuitable material may be
  • the cathode-base or support-for the coating may consist IEOIQX'. ample of tungsten,- molybdenum, platinum, platinum-iridium alloy, orcarbon'.
  • the coat: ing metal may be applied to the supportby electro-deposition, .byprecipitatioh :or. de-
  • Th" invention will be' particularly de scribed byway of example, in its applica tion' to coating a cathode of platinum or molybdeniun with the oxides of alkaline earth metals.
  • 'Ashereinbefo'restated, preferably 0 the alkalineearth metal is 'depositedfonthe filament by electrolysis of an acetone solutionof the iodide
  • To prepare the electroly tic solution in one method a quantity of one of the alkalineearth metal iodid'esis "placed in' a distilling flask and. heated in a current of hydrogen to atemperature 'between 18O C, i and 200 (lg'for a period of at least two hours,- in order to secure complete dehydration.
  • tungsten or molybdenumis employed for the cathode then it is cleaned in the case of Wire by heating in hydrogen; or in'the caseof sheet or tube by dipping it into molten'sodiumor V potassium nitrate, which is finally caretully removed from the cathode by washing; The cathode is then'lowered into the electrolytic depositing bath; It is obvious that a :number i of cathodes'may be coated at the same time,
  • the filament isf advanta'geously 9 I M50309 a coated with a mixture of alkaline earth metals rather than with a single alkaline earth metal. This may be effected by two electrolytic deposition processes employing solutions of strontium iodide and barium iodide. The filament is placed alternately in each electrolytic bath thus coating it with alternate layers of.
  • strontium and barium may be coated with two layers only.
  • the metals deposited alloy with each other when the filament is subsequently heated.
  • a mixture of barium and strontium may be deposited from a single electrolytic bath containing a solution of mixed barium and strontium iodides.
  • the filament with the desired alkaline earth metal is removed from the bath and the metal coat isconverted to oxide.
  • This may be efi'ectedin various ways. For example it is sufficient to leave the filament in dry air, butit is preferable to heat it to a temperature between 600 C. and 700 C. in air for half-an-hour to two hours.
  • the coated metals are alloyed with each other,converted to oxides and the oxide coating firmly bonded to the filament.
  • the oxide coat produced by any of the above described processes may then be converted if desired to a carbonate coat.
  • filamentwithacarbonate coating can be han- I refractory metal, such as molybdenum or dled with ease, and can be left in a moist atmosphere without injury, before its subsequent assembly in a valve, whereas an oxide coatedfilament often requires a further protective coating.
  • the coat may be oxidized while it is still in the depositing bath by permitting a little water tobe present.
  • the coatin is deposited as metal and is then oxidized y the water present in the solution, the cathode subsequently being heated.
  • the exact action of the water is not known, but it appears that a complex oxygen compound is formed probe ablycombined with acetone. Although this methodof roduction is not preferred it may sometimes e employed for coating special cathodes.
  • the alkaline earth metal may. .betialloyed thereto by beating out of the presence of oxidizing gases before the oxidizing process is effected.
  • a platinum filament coated with a mixture of barium and strontiummetal may be heated for a few moments in pure hydrogen, whereby subsequently a more homogeneous and amore firmly bonded coat is obtained. It will berealized, however, that this alloying process cannot be carried out when metals such as molybdenum or tungsten form the supporting base. 1
  • the filament is flashed in air.
  • the filament is flashed for a moment or two to a temperature of say 1100C.to 1200 C. after which period it is baked in the usual manner.
  • the barium and strontium metal should not be alloyed to the base, since often the subsequently produced oxides are found to have eaten in to the base, thus making it brittle. If the base is in the form of. a thin filament, the uniformity of its resistance is thus stroyed.
  • the supporting base consists of a strong tungstenthen after being coated it is preferably not heated in air, since oxidation of the molybdenum or tungsten takes place and the coating falls off.
  • the coated tungsten or molybdenum is heated for about ten minutes at'a dull red heat in hydrogen of commercial purity.
  • sufiicient oxygen or oxygen containing material such as water present in the hydrogen and in the metal support to effect partial or complete oxidation of the alkaline earth metal de posits.
  • the coating may then be converted to carbonate ifdesired in the manner described above.
  • cathodes of tungsten and molybdenum may be coated with an adherent coating of alkalineearth oxides or a mixture of these; and it is particularly applicable to cases in which thecathode is not filamentary such for example, as when it consists of a sheet or tube of tungsten or molybdenum.
  • the invention may be applied generally to the. coating of cathodes with compounds or mixtures of compounds of any metalfor obtaining a desired electron emission, and is not limited to the processes described by way'of example.
  • the method of making electron-emit ting cathodes'for vacuum electric tubes by coating a suitable support with at least one metal, converting said coating into a comwhich has desired electron-emitting properties, and then convertingsaidcoating j to a carbonateby h'eating in an atmosphere 1 of carbon dioxide, whereby the cathode can readily be handled before assembly.
  • the method of making an electron-emit- I ting cathode of the oxide-coated type which consists in: depositing on a metal cathode a coatingof at least one alkaline earth metal and substantially said coating.
  • y I y 4 The method of making an electron-emitting cathode of the oxide-coated type, which consists .in electrolytically depositing on a suitable support a coating of at least one alkaline earth metal from .a solution thereof i in acetone containing a trace of water.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
US715653A 1923-06-12 1924-05-24 Vacuum electric tube Expired - Lifetime US1850809A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB15309/23A GB221851A (en) 1923-06-12 1923-06-12 Improvements in or relating to vacuum electric tubes

Publications (1)

Publication Number Publication Date
US1850809A true US1850809A (en) 1932-03-22

Family

ID=10056785

Family Applications (1)

Application Number Title Priority Date Filing Date
US715653A Expired - Lifetime US1850809A (en) 1923-06-12 1924-05-24 Vacuum electric tube

Country Status (5)

Country Link
US (1) US1850809A (en(2012))
DE (1) DE483948C (en(2012))
FR (1) FR582662A (en(2012))
GB (1) GB221851A (en(2012))
NL (1) NL15308C (en(2012))

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2693431A (en) * 1948-01-27 1954-11-02 Eitcl Mccullough Inc Method of making electron emitters
US2798828A (en) * 1952-03-26 1957-07-09 Ets Claude Paz & Silva Process for manufacturing electrodes for gaseous electric discharge apparatus
US3265924A (en) * 1962-06-29 1966-08-09 York Res Corp Thermionic tube having novel heater and cathode

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE968912C (de) * 1931-09-15 1958-04-10 Siegmund Loewe Dr Verfahren zur Herstellung von Hochemissionskathoden fuer Entladungsgefaesse
NL48805C (en(2012)) * 1936-09-01
DE741396C (de) * 1937-07-17 1943-11-10 Sueddeutsche Telefon App Kabel Verfahren zur Herstellung von isolierten gewendelten Heizdraehten fuer indirekt geheizte Kathoden

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2693431A (en) * 1948-01-27 1954-11-02 Eitcl Mccullough Inc Method of making electron emitters
US2798828A (en) * 1952-03-26 1957-07-09 Ets Claude Paz & Silva Process for manufacturing electrodes for gaseous electric discharge apparatus
US3265924A (en) * 1962-06-29 1966-08-09 York Res Corp Thermionic tube having novel heater and cathode

Also Published As

Publication number Publication date
NL15308C (en(2012)) 1900-01-01
DE483948C (de) 1929-10-09
FR582662A (fr) 1924-12-24
GB221851A (en) 1924-09-12

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