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

• the invention relates to a high-emission cathode for vacuum tubes, for example rectifiers, amplifiers, oscillation generators.
• a high-emission cathode for vacuum tubes, for example rectifiers, amplifiers, oscillation generators.
• rectifiers, amplifiers, oscillation generators for example rectifiers, amplifiers, oscillation generators.
• oxide coating was also applied electrolytically.
• a much more satisfactory and already known method consists in applying a light metal to the filament by evaporation, whereby oxidation takes place subsequently (metal vapour process).
• the cathodes produced in accordance with the metal vapour process are excellent as regards efiiciency; from the standpoint of manufacture, however, the process is not'an entirely simple one.
• the invention relates to a high-emission tube having an oxide cathode, but consists of an additional development of the cathode production on such lines that the emissive oxide, for example light metal oxide, is first produced on the carrier filament, preferably according to the evaporation process, or according to an electrolytical process.
• the carrier filament coated with the metal oxide is then fitted as cathode in the discharge vessel, and is there raised to high emission by means of a special treatment.
• This special treatment consists of two measures, viz., in the first place in a heating of the filament in the absence of air, which causes initially a degasifying of the filament and, upon additional heating, a conversion of the carbonate and hydroxide, which are formed in addition to the oxide, into metal oxide; secondly in application, by atomization, of a light metal onto the pure metal oxide which is now present on the filament in the evacuated tube.
• the invention resides in the combination of various features, which only by reason of their particular cooperation are adapted to produce high-emission cathodes of equal effectiveness throughout, such as are capable of being produced according to the metal vapour process, but by a technically more simple method.
• the point concerned is the common use of the following factors:
• point (A) it may be remarked as follows:
• the appreciable increase in emission, which is obtained by cathodes produced according to the metal vapour process as compared with other methods must be maintained.
• the filament material is coated in relatively large quantities, for example in loosely wound wire coils, with a layer containing oxygen on the surface.
• the most desirable embodiment is constituted by a thin layer of brown tungsten dioxide on tungsten wire.
• the layer may be produced in continuous fashion at certain temperature in a furnace, which is filled with hydrogen having a certain percentage of water.
• the filament coated with tungsten dioxide is now introduced in a relatively large quantity, for example in the form of a loose roll, into a vacuum furnace, in which there is created a barium-vapour atmosphere.
• the metallic barium vapour reacts with the tungsten dioxide in the known manner, in such fashion, that on the surface of the tungsten wire there is now formed barium oxide, in which connection, however, there is also an excess of metallic barium present.
• the excess of metallic barium, according to the invention is again pumped away or bound otherwise in the furnace, for example is condensed by cooling, so that in the furnace there now remains the tungsten wire coated with pure barium oxide without an excess of metallic barium.
• a light metal is caused to evaporate in the manner known from the metal vapour process, viz., either the same metal from which the metal oxide is formed (in the described example: barium) or another metal, preferably a light metal with higher evaporation point than the metal base of the oxide employed.
• barium the same metal from which the metal oxide is formed
• another metal preferably a light metal with higher evaporation point than the metal base of the oxide employed.
• the metal coating applied by atomization has the surprising effect of initiating the emission process, so that in discharge vessels of this nature completion may be performed without the presence of any kind of gas.
• cathodes produced by the method according to the invention even result in an improved efliciency as compared with cathodes produced according to the pure metal vapour process, apparently owing to the fact, that control of the chemical reaction (conversion of the tungsten dioxide into barium oxide) can be performed more effectively in a special vacuum furnace than in the actual discharge vessel, in which it is difficult to select all of the conditions of reaction in such reliable fashion as in a special vacuum furnace.

Landscapes

• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Solid Thermionic Cathode (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=6396858

Family Applications (1)

Country Status (4)

Cited By (1)

• 0
  • NL NL40189D patent/NL40189C/xx active
  • FR FR742822D patent/FR742822A/fr not_active Expired
• 1932
  • 1932-09-12 GB GB25305/32A patent/GB395537A/en not_active Expired
  • 1932-09-14 US US633080A patent/US2049811A/en not_active Expired - Lifetime

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