Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
  • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
  • H01J1/02—Main electrodes
  • H01J1/13—Solid thermionic cathodes
  • H01J1/14—Solid thermionic cathodes characterised by the material
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
  • Y10T428/2913—Rod, strand, filament or fiber
  • Y10T428/2933—Coated or with bond, impregnation or core
  • Y10T428/294—Coated or with bond, impregnation or core including metal or compound thereof [excluding glass, ceramic and asbestos]
  • Y10T428/2958—Metal or metal compound in coating

Definitions

• This invention relates to electron-emittingcathodes of the oxide coated type, such as are used in thermionic discharge devices, and more particularly to an electrically conduc- 5 tive core or base for such cathodes.
• Nickel has very largely supersededthe use of platinum-iridium, due to the excessive expense of the platinum.
• Nickel has the d1S advantage, however, in that its specific resistance is such that the voltage-ampere characteristics required for the large size filaments cannot be readily obtained without reducing the thickness of the core to such an ex- 'tent that it is mechanically weak or, if proportioned for proper tensile strength, causing it to o crate at an excessively high tem-. 2 perature, elther of which result in short life.
• This high filament temperature results in bombardment of the cathode by back emission from the grid or plate, caused by the thermionically active coating on the cathode being thrown ofi at the high operating temperature thereof and depositing on the grid, and the heating of the grid, to an electron emitting temperature by heat radiated .from the overly heated.
• This back bombardment rapidly:
• the oxlde coating does not adhere as readily 'to the narrow ribbon as it does to the broader surface.
• the hot strength of nickel is low, moreover,
• One of the objects of the present invention 1s to overcome the above mentioned diiiiculties and to produce a metal core for an oxide coat-' ed cathode which will have the proper specific resistance to enable the required voltage-amperage characteristics to be readily obtained.
• a further object is to provide an electrical- I ly conductive core which will have a high tensile strength while hot.
• a stlll further object is to provide a thermionlcally active cathode which will have a large electron-emitting surface area for av ploy an alloy having a higher specific resistance than pure nckel, whereas, for the smaller slze'filaments, Iemploy an alloy having a lower specific resistance than nickel.
• silicon-nickel is preferred since its change in specific resistance for various percentages is very slight.
• An alloy containing about 3% of silicon I have found very satisfactory, but the percentage may run from 2 to 6% without materially a tering the electrical conductivity of the metal. This isadvantageous since it eliminates the necessit of maintaining exact proportions in the fabrication of the wire.
• Manganese nickel with a manganese content of 4% is also satisfactory for large filaments,
• Pure nickel ribbon of a weight corresponding'to a 6 or 8' mil Wire has a specific resist-. ance of about 5.35 ohms per sq. cm., whereas, the alloys which I prefer for filaments of this: weight have a specific resistance of about 6.
• This broad ribbon presents a more extensive sur-' face to which the oxide coating will adhere more tenaciously. It also increases the electron emitting area of the oathode and thereby enhances the electron emit-.
• the silicon or jmanganese-nickel alloy cores are not as susceptible to variations 1n their specific resistances by internal changes in the core as is nickel. 4
• the conductivity variesaccording' to the particular In the caseheat treatment and mechanical working to which it is subjected; It is the practice in the manufacture of electron discharge devices employing oxide sary to take into consideration the change in conductivity effected by this high temperature treatment. Since this treatment is not uniform in all tubes, the electrical conductivity of filament .cores of the same size is notuniform and this non-uniformity has caused considerable difliculty.
• An electron-emitting cathode comprising an alloy of nickel and silicon and a coating thereon of thermionically active ma- 10 terial.
• a metal core for an electron-emitting cathode of the oxide coated type composed of an alloy of nickel and about 3% of silicon.
• An electron-emitting cathode comprising a core composed of an alloy of a metal of the group containing nickel and up to 6% of silicon.

Landscapes

• Solid Thermionic Cathode (AREA)

Priority Applications (2)

Applications Claiming Priority (1)

Publications (1)

Family

ID=22860512

Family Applications (1)

Country Status (2)

Cited By (2)

• 0
  • NL NL27068D patent/NL27068C/xx active
• 1927
  • 1927-10-27 US US229276A patent/US1695845A/en not_active Expired - Lifetime

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