US2985946A - Indirectly heated cathode - Google Patents

Indirectly heated cathode Download PDF

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Publication number
US2985946A
US2985946A US583848A US58384856A US2985946A US 2985946 A US2985946 A US 2985946A US 583848 A US583848 A US 583848A US 58384856 A US58384856 A US 58384856A US 2985946 A US2985946 A US 2985946A
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US
United States
Prior art keywords
cathode
concentric
concentric body
mandrel
diameter
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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US583848A
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English (en)
Inventor
Weijer Henricus Johannes De
Heynen Constantius Jo Henricus
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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Publication of US2985946A publication Critical patent/US2985946A/en
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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
    • 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
    • Y10T29/00—Metal working
    • Y10T29/43—Electric condenser making
    • Y10T29/435—Solid dielectric type

Definitions

  • This invention relates to indirectly heated cathodes in the form of concentric cylinders electrically insulated from each other and to an improved method for making such cathodes.
  • Cathodes constructed according to the invention are particularly useful in reducing hum interference and microphonics due to heater vibrations in very sensitive tubes.
  • the cathode consists of a hollow tubular heater shield surrounded by a cathode sleeve from which the heater shield is insulated by a thin layer of dense insulating material.
  • the concentric body thus formed is compacted into an inseparable structure in order to reduce the wall thickness so as to improve heat transfer, to produce a more uniform structure, and to reduce the overall diameter of the cathode to dimensions which are appropriate in the small vacuum tubes of today.
  • the novel method by which the cathode is formed consists, broadly, in taking a pair of hollow metal tubes, one of which has a larger diameter than the other, coating either the outer surface of the smaller tube or the inner surface of the larger tube with a layer of dense insulating material, telescoping the tubes together, and drawing the resulting concentric body to reduce its wall thickness and overall diameter.
  • Fig. 2 shows one step in the method of producing cathode of Fig. l.
  • the cathode in Fig. 1 consists of an outer cathode sleeve 1 and a concentric inner sleeve 2 insulated from each other by a layer of dense insulating material 3.
  • a heater 4 is disposed within the heater shield 2 in the customary manner.
  • the enlarged portion of the cathode indicated by reference character 5 is a rib which is commonly found in cathodes and is provided for the purpose of locating a cathode in the usual mounting structures in a vacuum tube (not shown).
  • a cathode lead 6 is connected to one end of the cathode sleeve 1 and a lead 7 is connected to the heater shield 2 in order that the heater shield may be separately grounded or connected to such voltage source as may be available after a tube utilizing the cathode has been constructed.
  • a metal cylinder is selected of some suitably ductile metal, such as nickel for example, having a diameter and wall thickness larger than the desired dimensions of the heater shield 2.
  • the cylinder selected may have a diameter of 4.3 mm. and a wall thickness of 150 microns, although these dimensions are not to be considered as limiting the invention.
  • a second ductile metal cylinder having a larger diameter and greater wall thickness than the rst is selected to become the cathode sleeve l.
  • the diameter and wall thickness of the second cylinder may be 5.4 mm. and 200 microns respectively.
  • Either the outer cylindrical surface of the smaller cylinder or the inner cylindrical surface of the larger cylinder is then coated with a layer of dense or compact insulating material.
  • a layer of dense or compact insulating material is by means of a cataphoretic or settling down process using aluminum oxide or magnesium oxide as the insulating material.
  • the invention is not limited to a cataphoretic or settling down process or to aluminum or magnesium oxide but is satisfied by any process and material which will produce a uniformly dense layer on the cylindrical surface.
  • the particles of the insulating material should preferably be as small as possible since the final wall thickness of a completed cathode is limited partly by the size of the particles in the insulating layer.
  • a gas-tight connection is formed between the outer cylinder and inner cylinder at one end. This may conveniently be done by soldering the outer cylinder to the inner cylinder with silver solder to form a unitary concentric body. This concentric body is then placed in a chamber which is evacuated and the body is heated by induction heating to drive oil gas. Preferably this heating should begin at the closed end of the concentric body and proceed longitudinally to the other end in order that no gas will be trapped.
  • a ring of silver solder may be provided adjacent the other end to be heated by the induction heating apparatus in the iinal step of degassing so that this solder ring will melt and seal the other end of the concentric body to prevent the gas from reentering after the concentric body is removed from the chamber.
  • the concentric body is then slipped into a mandrel 8 as shown in Fig. 2 and the mandrel, together with the concentric body, is then drawn through a die 9 which serves to reduce the overall Wall thickness of the concentric body. It is desirable to deform one end of the concentric body indicated by reference character 10 to allow it to enter the opening in die 9 without jamming. For example, the end 10 of the concentric body may be hammered into place.
  • the concentric body may be passed through several dies each of which may give a reductionin diameter of from 1% to 5%. If the Wall thickness has still not been reduced suliciently, the concentric body may be removed from the first mandrel, placed on a second mandrel, and passed through a second series of successively smaller dies. Before being placed on the second mandrel, the concentric body may be annealed. The reason for placing the concentric body on a second and smaller mandrel is that the internal diameter of the concentric body is reduced in the drawing process, although it is highly desirable that the mandrel itself not be reduced in diameter during the drawing process.
  • the mandrel 8 and the die 9 should be of material which is much harder than the ductile material out of which the cathode sleeve l and the heater shield 2 are made, It may be necessary to roll the concentric body after a drawing operation in order to remove it from the mandrel 8, to which it has a tendency to adhere because of pressure exerted during the drawing.
  • metal cylinders 1 and 2 which are from 30 centimeters to l meter in length and which are drawn on a mandrel 8 which may have a length of from 3 to 5 meters.
  • a typical cathode formed as described and starting with cylinders having the'dimcnsions given above may be reduced to an overall order to the hardness of the two metals.
  • cathode sleeve 1 has a diameter of 30 microns and the insulating layer 3 and the heater shield -2 each have a wall thickness of 20 microns.
  • These dimensions are substantially the same as the dimensions of an ordinary cathode constructed from a single piece of metal tubing. However it is possible using the process of the invention to manufacture cathcdes having an outer diameter of about 60() microns and a total wall thickness of 50 microns.
  • the cathode sleeve 1 and the insulating layer 3 are [removed from a short length at one end as shown in Fig. l so that the lead wire 7 may be attached to the heater shield Z as indicated. Any air which enters the compressed insulating material after the concentric body has been cut into short lengths may be removed during the usual degassing process after a tube has been built using the cathode.
  • the wall thickness of the cathode sleeve 1 is greater than the wall thickness of the heater' shield 2. This is desirable in order to prevent rupture of the cathode sleeve 1 during the drawing process, although it is not absolutely essential to the satisfactory formation of a concentric cathode structure.
  • the addition of an electron emissive coating to the outer surface of cathode sleeve 1 and the formation of rib may be carried out after the concentric body has been cut into short lengths.
  • the invention is not limited to the production of concentric cathode structures having only two metal tubes; three or more tubes may be drawn together in the same way. Nor it is it necessary that nickel be used for the cathode sleeve 1 and the heater shield 2; different materials may be used for these elements provided that the initial wall thickness before drawing be selected in inverse Still further modifications may occur to those skilled in the art, and the invention is to be limited only by the following claims.
  • the method of making an indirectly heated cathode structure comprising an outer metallic cathode sleeve having an inner cylindrical surface, and an inner heater shield having an outer cylindrical surface located substantially concentrically within said cathode sleeve, said method comprising the stepsv of depositing a compact layer of insulating material on one of said cylindrical surfaces; telcscoping said heater shield within said cathode sleeve; forming a substantially gas tight connection between said heater shield and said cathode sleeve at one end thereof to form a unitary concentric body; degassing said unitary concentric body; inserting a mandrel within said concentric body; drawing said mandrel, together with said concentric body, through a die to form said concentric body into an inseparable concentric structure without substantially reducing the diameter of said mandrel, and thereafter removing the mandrel from said structure.
  • the method of making an indirectly heated cathode structure which comprises an outer metallic cathode sleeve having an inner cylindrical surface, and an inner heater shield having an outer cylindrical surface located substantially concentrically within said cathode sleeve, said method comprising the steps of cataphoretically depositing on at least one of said cylindrical surfaces a layer of compact insulating material; telescoping said heater shield within said cathode sleeve; forming a substantially gas tight connection between said heater shield and said cathode sleeve at one ⁇ end thereof to form a unitary concentric body; degassing said unitary concentric body; forming a second substantially gas tight connection between said heater shield and said cathode sleeve at thc other end thereof; inserting a mandrel within said concentric body; deforming one end of said concentric body to allow the deformed end of said concentric body and said mandrel to enter a die; drawing said mandrel, together with said concentric body, through

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
  • Solid Thermionic Cathode (AREA)
US583848A 1955-05-10 1956-05-09 Indirectly heated cathode Expired - Lifetime US2985946A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL2985946X 1955-05-10

Publications (1)

Publication Number Publication Date
US2985946A true US2985946A (en) 1961-05-30

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US583848A Expired - Lifetime US2985946A (en) 1955-05-10 1956-05-09 Indirectly heated cathode

Country Status (5)

Country Link
US (1) US2985946A (en, 2012)
BE (1) BE547691A (en, 2012)
DE (1) DE1011529B (en, 2012)
FR (1) FR1153189A (en, 2012)
NL (1) NL100356C (en, 2012)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3252040A (en) * 1963-06-19 1966-05-17 Varian Associates Electron tube and cathode therefor
US3259783A (en) * 1964-02-14 1966-07-05 Thorn A E I Radio Valves & Tub Indirectly-heated cathode assemblies
US3279028A (en) * 1964-05-01 1966-10-18 Rca Corp Method of manufacturing thermionic energy converter tube
US3299492A (en) * 1963-08-14 1967-01-24 Simmonds Precision Products Electroformed inner tube for tank unit

Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1193667A (en) * 1916-08-08 Method of producing compound metal objects
US1341812A (en) * 1919-02-13 1920-06-01 Cie Belge Du Bi Metal Sa Process for the manufacture of wires and tubes of two metals
US1426734A (en) * 1919-04-30 1922-08-22 Western Electric Co Method of manufacturing audions
US1568369A (en) * 1923-10-20 1926-01-05 Everett Samuel James Production of metal tubing and of tubular metal articles or instruments
US1700454A (en) * 1924-07-08 1929-01-29 Western Electric Co Electron emitter and process of making the same
US1719988A (en) * 1923-01-26 1929-07-09 Westinghouse Lamp Co Electron device and the like adapted for alternating current
US1897229A (en) * 1927-12-06 1933-02-14 Telefunken Gmbh Indirectly heated cathode
US2091001A (en) * 1935-08-26 1937-08-24 Reconstruction Finance Corp Tube drawing means
US2366168A (en) * 1942-05-02 1945-01-02 Dow Chemical Co Bonding magnesium-alloy sheets
FR952361A (fr) * 1947-08-14 1949-11-16 Radio Electr Soc Fr Procédé pour préparation de cathodes pour tubes électroniques
US2499944A (en) * 1946-10-04 1950-03-07 Porter H Brace Gun tube liner material
US2581876A (en) * 1949-03-30 1952-01-08 Rca Corp Grid structure for electron discharge device
US2663069A (en) * 1951-07-20 1953-12-22 Philips Lab Inc Method of making incandescent cathodes
US2724070A (en) * 1953-02-09 1955-11-15 Westinghouse Electric Corp Cathode coating for electrical discharge devices and method for making the same

Patent Citations (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1193667A (en) * 1916-08-08 Method of producing compound metal objects
US1341812A (en) * 1919-02-13 1920-06-01 Cie Belge Du Bi Metal Sa Process for the manufacture of wires and tubes of two metals
US1426734A (en) * 1919-04-30 1922-08-22 Western Electric Co Method of manufacturing audions
US1719988A (en) * 1923-01-26 1929-07-09 Westinghouse Lamp Co Electron device and the like adapted for alternating current
US1568369A (en) * 1923-10-20 1926-01-05 Everett Samuel James Production of metal tubing and of tubular metal articles or instruments
US1700454A (en) * 1924-07-08 1929-01-29 Western Electric Co Electron emitter and process of making the same
US1897229A (en) * 1927-12-06 1933-02-14 Telefunken Gmbh Indirectly heated cathode
US2091001A (en) * 1935-08-26 1937-08-24 Reconstruction Finance Corp Tube drawing means
US2366168A (en) * 1942-05-02 1945-01-02 Dow Chemical Co Bonding magnesium-alloy sheets
US2499944A (en) * 1946-10-04 1950-03-07 Porter H Brace Gun tube liner material
FR952361A (fr) * 1947-08-14 1949-11-16 Radio Electr Soc Fr Procédé pour préparation de cathodes pour tubes électroniques
US2581876A (en) * 1949-03-30 1952-01-08 Rca Corp Grid structure for electron discharge device
US2663069A (en) * 1951-07-20 1953-12-22 Philips Lab Inc Method of making incandescent cathodes
US2724070A (en) * 1953-02-09 1955-11-15 Westinghouse Electric Corp Cathode coating for electrical discharge devices and method for making the same

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3252040A (en) * 1963-06-19 1966-05-17 Varian Associates Electron tube and cathode therefor
US3299492A (en) * 1963-08-14 1967-01-24 Simmonds Precision Products Electroformed inner tube for tank unit
US3259783A (en) * 1964-02-14 1966-07-05 Thorn A E I Radio Valves & Tub Indirectly-heated cathode assemblies
US3279028A (en) * 1964-05-01 1966-10-18 Rca Corp Method of manufacturing thermionic energy converter tube

Also Published As

Publication number Publication date
DE1011529B (de) 1957-07-04
NL100356C (en, 2012)
FR1153189A (fr) 1958-03-03
BE547691A (en, 2012)

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