US2737607A - Incandescible cathode - Google Patents

Incandescible cathode Download PDF

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Publication number
US2737607A
US2737607A US297306A US29730652A US2737607A US 2737607 A US2737607 A US 2737607A US 297306 A US297306 A US 297306A US 29730652 A US29730652 A US 29730652A US 2737607 A US2737607 A US 2737607A
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alkaline earth
cavity
cathode
emissive surface
electron
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US297306A
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Lemmens Hendrikus Johannes
Jansen Marinus Jacobus
Haayman Pieter Willem
Linden Petrus Cornelis Van Der
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Hartford National Bank and Trust Co
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Hartford National Bank and Trust Co
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    • 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
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H01J1/28—Dispenser-type cathodes, e.g. L-cathode

Definitions

  • This invention relates to an incandescible cathode and more particularly to a cathode containing a supply of an alkaline earth compound capable of reduction by a refractory metal to free alkaline earth metal.
  • Cathodes of the aforesaid type have been described in U. S. Patent 2,543,728 to H. I. Lemmens et al.
  • a reservoir of alkalineearth compounds is located within a cavity of a body of refractory material which body has a porous wall portion and is tightly'closed so that the pores of the porous wall portion form the largest connecting passageways connecting the reservoir of alkaline earth compounds with the outside of the cathode.
  • the alkaline earth compounds disclosed in the said patent are the carbonates of the alkaline earth metals, for example barium and strontium which decompose at elevated temperatures to form the oxides of the alkaline earth metals with release of carbon dioxide. The latter must then be pumped off continuously to maintain a high vacuum in the tube.
  • the cathode comprises a structure forming an internal cavity, the portion of the structure surrounding the cavity consisting of a refractory metal such as tungsten, molybdenum, tantalurn, zirconium or hafnium.
  • a refractory metal such as tungsten, molybdenum, tantalurn, zirconium or hafnium.
  • an alkaline earth boride for example, BaBs or SrBs, and mixtures of those compounds is disposed.
  • the cavity is sealed by means of a wall of porous refractory metal, the pores of this wall forming the largest passageways connecting the cavity to the exterior of the cathode.
  • the porous wall of the cavity preferably consists of a body of tungsten formed by pressing powdered tungsten and sintering the same at temperatures exceeding 1600n C. in order to obtain tungsten body of required porosity.
  • the borides do not require a high formation temperature such as carbonates the tungsten may be sintered as low as 1400 C. However, therein very line powder should be used.
  • the borides of the alkaline earth metals should be preferably in a crystalline state.
  • the cathode shown in the drawing comprises a porous tungsten plate 1 formed as described in U. S. Patent 2,543,728 in order to have the correct porosity.
  • the plate is 0.5 mm. thick and 3 mms. in diameter.
  • the tungsten plate 1 together with a cup-shaped molybdenum member 2 with a sharp upper edge 3 to which the tungsten plate is secured forms an internal cavity in which a supply 4 of about 1 to 5 mgs. of barium boride is disposed. Plate 1 is welded to the edge 3 to tightly seal the cavity.
  • the cathode is heated by means of a heater 5 disposed within a tubular extension 6 of the cup-shaped molybdenum member.
  • a dispenser cathode comprising a structure forming an internal cavity and having an electron emissive surface, a porous sintered body of refractory metal forming part of the wall of said structure, said structure being tightly closed with the pores of said wall portion constituting the largest passageways connecting the cavity to said electron emissive surface, and a supply within said cavity of an alkaline earth material capable of furnishing free alkaline earth metal to said electron-emissive surface at a rate sufficient to maintain a monomolecular layer of alkaline earth metal thereon, said material consisting essentially of an alkaline earth boride.
  • a dispenser cathode comprising a structure forming an internal cavity and having an electron emissive surface, a porous sintered body of tungsten forming part of the wall of said structure, said structure being tightly closed with the pores of said wall portion constituting the largest passageways connecting said cavity to said electronemissive surface, and a supply within said cavity of an alkaline earth material capable of furnishing free alkaline earth metal to said surface at a rate sutlicient to maintain a monomolecular layer of alkaline earth metal thereon, said material consisting essentially of an alkaline earth boride.

Description

ta, i-
United States Patent O INCANDESCIBLE CATHODE Hendrikus `lohannes Lemmens, Marinus Jacobus Jansen, Pieter Willem Haayman, and Petrus Cornelis van der Linden, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 5, 1952, Serial No. 297,306 Claims priority, application Netherlands July 17, 1951 4 Claims. (Cl. 313-346) This invention relates to an incandescible cathode and more particularly to a cathode containing a supply of an alkaline earth compound capable of reduction by a refractory metal to free alkaline earth metal.
Cathodes of the aforesaid type have been described in U. S. Patent 2,543,728 to H. I. Lemmens et al. In the cathodes described in the patent, a reservoir of alkalineearth compounds is located within a cavity of a body of refractory material which body has a porous wall portion and is tightly'closed so that the pores of the porous wall portion form the largest connecting passageways connecting the reservoir of alkaline earth compounds with the outside of the cathode. The alkaline earth compounds disclosed in the said patent are the carbonates of the alkaline earth metals, for example barium and strontium which decompose at elevated temperatures to form the oxides of the alkaline earth metals with release of carbon dioxide. The latter must then be pumped off continuously to maintain a high vacuum in the tube.
` It is an object of the present invention to eliminate the need for continuous evacuation of the discharge tube during activation of the cathode in an electric discharge tube.
This and further objects of this invention will appear as the specification progresses.
In accordance with this invention, the cathode comprises a structure forming an internal cavity, the portion of the structure surrounding the cavity consisting of a refractory metal such as tungsten, molybdenum, tantalurn, zirconium or hafnium. Within the cavity a supply of an alkaline earth boride, for example, BaBs or SrBs, and mixtures of those compounds is disposed. The cavity is sealed by means of a wall of porous refractory metal, the pores of this wall forming the largest passageways connecting the cavity to the exterior of the cathode.
The porous wall of the cavity preferably consists of a body of tungsten formed by pressing powdered tungsten and sintering the same at temperatures exceeding 1600n C. in order to obtain tungsten body of required porosity. As the borides do not require a high formation temperature such as carbonates the tungsten may be sintered as low as 1400 C. However, therein very line powder should be used.
The borides of the alkaline earth metals should be preferably in a crystalline state.
Since there is no carbon dioxide formed during the life of the cathode, no exhaust of gas is required. The amount of gas released by a cathode of this type does not exceed the amount of gas liberated by other parts of the tube and consequently, the cathode only requires a few minutes for the formation of a monomolecular layer of alkaline earth metal on the exterior surface.
The invention will be described in connection with the accompanying drawing in which the sole figure shows one embodiment of a cathode according to the invention.
The cathode shown in the drawing comprises a porous tungsten plate 1 formed as described in U. S. Patent 2,543,728 in order to have the correct porosity. The plate is 0.5 mm. thick and 3 mms. in diameter. The tungsten plate 1 together with a cup-shaped molybdenum member 2 with a sharp upper edge 3 to which the tungsten plate is secured forms an internal cavity in which a supply 4 of about 1 to 5 mgs. of barium boride is disposed. Plate 1 is welded to the edge 3 to tightly seal the cavity. The cathode is heated by means of a heater 5 disposed within a tubular extension 6 of the cup-shaped molybdenum member.
While the invention has been disclosed in connection with a specific embodiment thereof other modifications will be readily apparent to those skilled in this art with out departing from the spirit and scope of this invention as delined in the appended claims.
What we claim is:
1. A dispenser cathode comprising a structure forming an internal cavity and having an electron emissive surface, a porous sintered body of refractory metal forming part of the wall of said structure, said structure being tightly closed with the pores of said wall portion constituting the largest passageways connecting the cavity to said electron emissive surface, and a supply within said cavity of an alkaline earth material capable of furnishing free alkaline earth metal to said electron-emissive surface at a rate sufficient to maintain a monomolecular layer of alkaline earth metal thereon, said material consisting essentially of an alkaline earth boride.
2. A dispenser cathode comprising a structure forming an internal cavity and having an electron emissive surface, a porous sintered body of tungsten forming part of the wall of said structure, said structure being tightly closed with the pores of said wall portion constituting the largest passageways connecting said cavity to said electronemissive surface, and a supply within said cavity of an alkaline earth material capable of furnishing free alkaline earth metal to said surface at a rate sutlicient to maintain a monomolecular layer of alkaline earth metal thereon, said material consisting essentially of an alkaline earth boride.
3. A dispenser cathode as claimed in claim 2 in which the alkaline earth material c-onsists essentially of barium boride.
4. A dispenser cathode as claimed in claim 1 in which the alkaline earth material is a mixture of barium boride and strontium boride.
References Cited inthe file of this patent UNITED STATES PATENTS 1,720,654 Wein July 9, 1929 1,936,334 Miesse Nov. 21, 1933 2,121,589 Espe June 21, 1938 2,543,728 Lemmens et al Feb. 27, 1951 2,647,216 Brown July 28, 1953

Claims (1)

1. A DISPENSER CATHODE COMPRISING A STRUCTURE FORMING AN INTERNAL CAVITY AND HAVING AN ELECTRON EMISSIVE SURFACE, A POROUS SINTERED BODY OF REFRACTOR METAL FORMING PART OF THE WALL OF SAID STRUCTURE, SAID STRUCTURE BEING TIGHTLY CLOSED WITH THE PORES OF SAID WALL PORTION CONSTITUTING THE LARGEST PASSAGEWAYS CONNECTING THE CAVITY TO SAID ELECTRON EMISSIVE SURFACE, AND A SUPPLY WITHIN SAID CAVITY OF AN ALKALINE EARTH MATERIAL CAPABLE OF FURNISHING FREE ALKALINE EARTH METAL TO SAID ELECTRON-EMISSIVE SURFACE AT A RATE SUFFICIENT TO MAINTAIN A MONOMOLECULAR LAYER OF ALKALINE EARTH METAL THEREON, SAID MATERIAL CONSISTING ESSENTIALLY OF AN ALKALINE EARTH BORIDE.
US297306A 1951-07-17 1952-07-05 Incandescible cathode Expired - Lifetime US2737607A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL309313X 1951-07-17

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US2737607A true US2737607A (en) 1956-03-06

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US (1) US2737607A (en)
BE (1) BE512852A (en)
CH (1) CH309313A (en)
FR (1) FR1071683A (en)
GB (1) GB699287A (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2869017A (en) * 1956-10-24 1959-01-13 Philips Corp Thermionic dispenser cathode
US2928013A (en) * 1954-12-23 1960-03-08 Siemens Ag Electrical discharge device
US3079515A (en) * 1960-08-22 1963-02-26 Gen Electric Energy conversion device and methods of making
US3258636A (en) * 1961-09-01 1966-06-28 Electron emitter with activator of sill cide, boride or carbide of solid solu- tion of barium and at least one other alkaline earth metal
US3513349A (en) * 1966-01-08 1970-05-19 Matsushita Electronics Corp Discharge tube

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1720654A (en) * 1925-05-13 1929-07-09 Radio Patents Corp Photo-electric cell
US1936334A (en) * 1929-01-31 1933-11-21 Gen Scientific Corp Electrode
US2121589A (en) * 1934-06-28 1938-06-21 Westinghouse Electric & Mfg Co Emissive incandescent cathode
US2543728A (en) * 1947-11-26 1951-02-27 Hartford Nat Bank & Trust Co Incandescible cathode
US2647216A (en) * 1950-04-01 1953-07-28 Rca Corp Dispenser cathode

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1720654A (en) * 1925-05-13 1929-07-09 Radio Patents Corp Photo-electric cell
US1936334A (en) * 1929-01-31 1933-11-21 Gen Scientific Corp Electrode
US2121589A (en) * 1934-06-28 1938-06-21 Westinghouse Electric & Mfg Co Emissive incandescent cathode
US2543728A (en) * 1947-11-26 1951-02-27 Hartford Nat Bank & Trust Co Incandescible cathode
US2647216A (en) * 1950-04-01 1953-07-28 Rca Corp Dispenser cathode

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2928013A (en) * 1954-12-23 1960-03-08 Siemens Ag Electrical discharge device
US2869017A (en) * 1956-10-24 1959-01-13 Philips Corp Thermionic dispenser cathode
US3079515A (en) * 1960-08-22 1963-02-26 Gen Electric Energy conversion device and methods of making
US3258636A (en) * 1961-09-01 1966-06-28 Electron emitter with activator of sill cide, boride or carbide of solid solu- tion of barium and at least one other alkaline earth metal
US3513349A (en) * 1966-01-08 1970-05-19 Matsushita Electronics Corp Discharge tube

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Publication number Publication date
BE512852A (en)
FR1071683A (en) 1954-09-03
CH309313A (en) 1955-08-31
GB699287A (en) 1953-11-04

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