US3225246A - Indirectly heated cathode - Google Patents

Indirectly heated cathode Download PDF

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Publication number
US3225246A
US3225246A US268387A US26838763A US3225246A US 3225246 A US3225246 A US 3225246A US 268387 A US268387 A US 268387A US 26838763 A US26838763 A US 26838763A US 3225246 A US3225246 A US 3225246A
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US
United States
Prior art keywords
cathode
collar
heater
wire
rod
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
Application number
US268387A
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English (en)
Inventor
Hollingsworth James William
Horton Murray Robert
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
RCA Corp
Original Assignee
RCA Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by RCA Corp filed Critical RCA Corp
Priority to US268387A priority Critical patent/US3225246A/en
Priority to GB11274/64D priority patent/GB1027404A/en
Priority claimed from BE645648A external-priority patent/BE645648A/fr
Priority to BE645648A priority patent/BE645648A/fr
Priority to SE3769/64A priority patent/SE303806B/xx
Priority to DER37546A priority patent/DE1257981B/de
Priority to NL6403305A priority patent/NL6403305A/xx
Priority to FR968911A priority patent/FR1386875A/fr
Publication of US3225246A publication Critical patent/US3225246A/en
Application granted granted Critical
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H01J1/22—Heaters

Definitions

  • Indirectly heated cathodes usually include a metal sleeve having electron-emitting oxides on the outer surface thereof.
  • a heater in the form of a wire is disposed insulatingly within the sleeve in heat transfer relation thereto.
  • the wire is connected to a suitable current source for heating the Wire by current losses therein.
  • the heated wire transfers heat produced therein to the sleeve for heating the oxides on the sleeve to emitting temperature.
  • Some types of tubes are involved in applications in which the heater Wire is subjected to a relatively high voltage.
  • Such high voltage heater wire has relatively small cross sectional dimensions.
  • a six volt tungsten heater wire may have a diameter of from eight to ten mils
  • a twenty-six volt tungsten heater wire on the other hand has a diameter of from two to lve mils for satisfactory operation.
  • Another object is to provide a high voltage heater structure for an indirectly-heated cathode wherein a relatively thin heater wire is ruggedly supported and electrically insulated from adjacent metallic elements.
  • a further object is to provide a heater structure contributing to facility in assembling the heater in a cathode sleeve and xing the structure in desired position within the sleeve.
  • a heater structure may comprise a ceramic tube having a closely wound coil of insulated tungsten wire thereon.
  • the ceramic tube is fixed at its ends to two spaced metallic collars or flanges, to which collars the opposite ends of the heater wire are connected, as being embedded in metalized coatings on the end surfaces of the tube.
  • One of the collars which may be called the upper collar, is snugly telescoped over a conducting rod and fixed thereto.
  • the other or lower collar has a central opening sufficiently large to provide clearance between the collar and rod.
  • the lower collar has a larger outer diameter than the upper collar outer diameter to provide a snug engagement for welding between the outer periphery of the lower collar and the inner surface of a cathode sleeve.
  • a ceramic disc having a central opening Prior to insertion of the heater struc- ICC ture within the cathode sleeve, a ceramic disc having a central opening is telescoped over and into engagement with an end portion of the conducting rod extending through the upper collar.
  • the ceramic disc has a diameter substantially equal to that of the lower collar for snugly engaging the inner wall of the cathode sleeve.
  • This provides a highly rugged cathode-heater sub-assembly for an electron tube, permitting the use of relatively thin heater wire for high voltage heater energization.
  • FIG. 1 shows a longitudinal cross-section of a cathodeheater structure for an electron tube
  • FIG. 2 is a fragmentary view taken along the line 2-2 of FIG. l.
  • the cathode-heater structure shown in FIG. 1 comprises a tubular cathode 10 including an active portion 12 having thereon a coating 14 of electron emitting material which may be in the form of carbonates of barium, strontium and calcium.
  • the cathode may be made of a material such as nickel.
  • the carbonates referred to are converted to oxides.
  • the cathode 10 also includes a ange 16 which may serve as a cathode lead-in in the completed tube.
  • a thinned-down portion 18 of the cathode serves as an effective heat dam to reduce heat losses from the active portion 12 to the flange 16.
  • the upper end of cathode 10 as viewed in FIG. l is partly closed by an annular inturned end portion 20 dening an opening 22.
  • a heater assembly 24 Within the cathode 10 is disposed a heater assembly 24.
  • This assembly comprises a cylinder 26 made of a ceramic such as Forsterite having thereon a closely Wound coil 23 of tungsten wire 30 coated with insulating material 32 such as aluminum oxide, to insulate adjacent turns of the coil from each other.
  • a metal collar 34 which may be made of nickel.
  • the collar 34 as well as the coil 28 have an appreciably smaller diameter than the inner diameter of the active portion 12 of the cathode, so as to be space insulated therefrom.
  • such upper end surface is suitably metalized as by the use of conventional molybdenum salts, and the resultant molybdenum coating is plated with copper to permit brazing of such surface to an annular portion of the collar 34.
  • the collar 34 is provided with a central opening for snugly embracing a metal rod or pin 36, made of nickel, for example.
  • an uncoated portion 54 of the wire (FIG. 2) is clamped between the upper collar 34 and 'the upper surface of the cylinder 26, As shown in FIG. 1, when the upper collar 34 is brazed to the metalized coating 56, at a temperature of about 1140 C., the uncoated portion 54 of the heater wire is embedded in the softened copper of the metalized coating and in good electrical Contact with the metal collar 34. Since the upper collar 34 conductively engages the rod 36 and the rod in turn is conductively xed to ange 48, the latter ange may serve effectively as a lead-in for the upper end of the heater coil 28.
  • the lower end portion (not shown) of the coil 28 is also free of insulation and is clamped between the metalized lower end surface of the cylinder 26, and an annular portion of a lower nickel collar 38 engaged by the metalized lower end surface of the cylinder.
  • the bare lower end portion of the Wire of coil 2S is embedded in the metal joint to the lower collar 38. Since this collar is fixed to the inner surface of the cathode as the aforementioned, the flange 16 of the cathode may serve conveniently as a lead-in for the lower end of the heater wire of coil 28.
  • the engagement of the lower end of the heater wire with the collar 38 may be similar to the embedded engagement described before herein in connection with the upper end of the heater wire.
  • the collar 38 defines a central opening 40 having a diameter for providing an appreciable space clearance with respect to rod 36.
  • the outer diameter of lower collar 38 is larger than that of the upper collar 34, for snug engagement with the inner wall of the lower end portion of the active portion 12 of the cathode.
  • the collar 38 is fixed to the inner wall of the active portion 12 as by an annular weld 42.
  • an insulating disc 44 made of a ceramic such as aluminum oxide, is provided with a central opening for receiving the upper end portion of rod 36 in a sliding engagement.
  • the outer diameter of the disc 44 is larger than the outer diameter of the upper collar 34, and snugly engages the inner wall of cathode 10.
  • the heater assembly Prior to fixing the lower collar 38 to the inner surface of the cathode, the heater assembly is urged upwardly in the cathode until the upper surface of the disc 44 abuts against the inner surface of the inturned portion 20 of the cathode.
  • the opening 22 in the upper end of the cathode is sufficiently large to permit the upper end of the rod 36 to extend therethrough without danger of electrical shorts therebetween.
  • the rod 36 is fixed to the upper collar 34 by means of a metal ring or eyelet 46 which may be fixed as by welding to both the collar 34 and the rod 36.
  • the washer 52 provides a joint of graded expansion characteristics between the insulating ring 50 and the flange 16.
  • opposite faces of the ring 50 to the fiange 48 and washer 52 are suitably metalized in a manner which may involve the use of conventional molybdenum salts as aforementioned.
  • the periphery of washer S0 is not metalized so that the faces are insulated from each other.
  • the heater structure In assembling the heater structure 24 in the cathode t 10, the heater structure may be held by the rod 36 in position so that the collar 34 thereof is uppermost. Thereafter, the insulating disc 44 may be threaded over the upper end of the rod 36 and in seated relation with respect to collar 34. The cathode may then be telescoped downwardly over the heater structure until the disc 44 abuts against the inner surface of the inturned portion of the cathode. When in this position, the lower collar 38 may be fixed to the inner surface of the cathode. It will be noted that the lower collar 38 is fixed to the active and relatively thick portion 12 of the cathode. This contributes to ruggedness of the assembly.
  • the washer 52 and insulating ring 50 are positioned on the transverse portion of flange 16, with the assembly preferably supported in such a way as to cause the flange 16 to extend upwardly.
  • the flange 48 is threaded over the adjacent end of the rod 36 and is seated on a metalized surface of ring 50.
  • suitable brazing material such as BT solder interposed between the rod 36 and flange 48, between the opposite surfaces of ring 50 and the flange 48 and washer 52, and between this washer and flange 16
  • the assembly is heated in a reducing atmosphere such as hydrogen in an oven at a temperature of about 1l40 C. for about ten minutes for brazing together the parts referred to.
  • the emitting carbonates held in a suitable binder, are applied to the active portion 12 of the cathode, as by spraying, to provide the coating 14.
  • the cathode-heater structure described provides a rugged support for the heater coil 28, and facilitates the operation of assembling the heater structure within the cathode.
  • the parts conveniently may be made to such close tolerance as to render self-jigging feasible.
  • the tungsten wire employed in the coil of the heater structure may have a thickness of from 2 to 4 mils, for service with a heater supply of 26 volts.
  • the insulating coating 32 on the tungsten wire may be made of a material such as aluminum oxide and having a thickness of about 2 mils. Assurance of continuous electrical contact between the ends of the wire of the coil and the collars 34, 38 is provided by the novel imbedment of the bare ends of the coil in the metalized coatings on the end surfaces of the cylinder 26.
  • a cathode-heater structure for an electron tube comprising:
  • a cathode-heater sub-assembly for an electron tube comprising:
  • a tubular cathode (b) a heater structure within said cathode, said heater structure comprising (l) an insulating cylinder having a coil of heater wire thereon,
  • an insulating disc having a central opening snugly receiving a portion of said rod adjacent to said second collar, said disc having an outer diameter for snugly engaging the inner wall of said cathode for electrically insulating said second collar from said cathode.
  • a cathode-heater sub-assembly for an electron tube comprising:
  • a heater structure within said cathode comprising (1) an insulating cylinder having a coil of heater wire thereon,
  • an insulating disc having a central opening snugly receiving a portion of said rod adjacent to said second collar, said disc having an outer diameter for snugly engaging the inner wall of said cathode for electrically insulating said second collar from said cathode,
  • An electron tube subassembly comprising an indirectly heated cathode having a heater structure cornprising:
  • An electron tube subassembly comprising an indirectly-heated cathode having a heater structure comprising:
  • An electron tube subassembly comprising an indirectly heated tubular cathode having a heater structure comprising:
  • An electron tube subassembly comprising an indidirectly heated cathode, said cathode having a heater structure comprising:
  • An electron tube subassembly comprising an indirectly heated cathode having a heater structure comprising:
  • a heater structure for an indirectly-heated tubular cathode comprising:
  • an insulating disc having an opening snugly receiving a portion fo said rod adjacent to said smaller collar, said disc having outer diameter substantially equal to that of said larger collars for a snug fit in said cathode.
  • a heater structure for an indirectly-heated tubular cathode comprising:

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  • Electrodes For Cathode-Ray Tubes (AREA)
US268387A 1963-03-27 1963-03-27 Indirectly heated cathode Expired - Lifetime US3225246A (en)

Priority Applications (7)

Application Number Priority Date Filing Date Title
US268387A US3225246A (en) 1963-03-27 1963-03-27 Indirectly heated cathode
GB11274/64D GB1027404A (en) 1963-03-27 1964-03-17 Indirectly heated cathode
BE645648A BE645648A (de) 1963-03-27 1964-03-24
DER37546A DE1257981B (de) 1963-03-27 1964-03-25 Indirekt geheizte Kathode fuer eine Elektronenroehre
SE3769/64A SE303806B (de) 1963-03-27 1964-03-25
NL6403305A NL6403305A (de) 1963-03-27 1964-03-26
FR968911A FR1386875A (fr) 1963-03-27 1964-03-27 Ensembles de chauffage pour cathodes à chauffage indirect de tubes électroniques

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US268387A US3225246A (en) 1963-03-27 1963-03-27 Indirectly heated cathode
BE645648A BE645648A (de) 1963-03-27 1964-03-24

Publications (1)

Publication Number Publication Date
US3225246A true US3225246A (en) 1965-12-21

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Family Applications (1)

Application Number Title Priority Date Filing Date
US268387A Expired - Lifetime US3225246A (en) 1963-03-27 1963-03-27 Indirectly heated cathode

Country Status (6)

Country Link
US (1) US3225246A (de)
DE (1) DE1257981B (de)
FR (1) FR1386875A (de)
GB (1) GB1027404A (de)
NL (1) NL6403305A (de)
SE (1) SE303806B (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3450927A (en) * 1965-11-16 1969-06-17 Philips Corp Thermionic cathode with heat shield having a heating current by-pass
US3737711A (en) * 1968-11-21 1973-06-05 Varian Associates Electron tube having an improved filamentary cathode and support therefor and method of making same
US4169987A (en) * 1977-02-04 1979-10-02 Hitachi, Ltd. Magnetron tubes cathode support

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114513868B (zh) * 2022-02-18 2022-09-09 哈尔滨工业大学 一种电推进空心阴极的电加热器组件

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1790153A (en) * 1927-10-15 1931-01-27 Gen Electric Electrical discharge device and method of operation
US1941074A (en) * 1930-09-17 1933-12-26 Bell Telephone Labor Inc Electric discharge device
US2510639A (en) * 1948-03-02 1950-06-06 Gen Electric Cavity resonator system
US2842701A (en) * 1954-12-22 1958-07-08 Raytheon Mfg Co Cathode heater assemblies

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE745133C (de) * 1935-06-27 1944-02-26 Aeg Mittelbar geheizte Kathode fuer elektrische Entladungsgefaesse
DE763222C (de) * 1938-08-23 1954-10-04 Siemens & Halske A G Mittelbar geheizte Gluehkathode fuer Elektronenstrahlroehren
DE1138483B (de) * 1957-11-29 1962-10-25 Eitel Mccullough Inc Hochleistungselektronenroehre fuer hohe Frequenzen

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1790153A (en) * 1927-10-15 1931-01-27 Gen Electric Electrical discharge device and method of operation
US1941074A (en) * 1930-09-17 1933-12-26 Bell Telephone Labor Inc Electric discharge device
US2510639A (en) * 1948-03-02 1950-06-06 Gen Electric Cavity resonator system
US2842701A (en) * 1954-12-22 1958-07-08 Raytheon Mfg Co Cathode heater assemblies

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3450927A (en) * 1965-11-16 1969-06-17 Philips Corp Thermionic cathode with heat shield having a heating current by-pass
US3737711A (en) * 1968-11-21 1973-06-05 Varian Associates Electron tube having an improved filamentary cathode and support therefor and method of making same
US4169987A (en) * 1977-02-04 1979-10-02 Hitachi, Ltd. Magnetron tubes cathode support

Also Published As

Publication number Publication date
NL6403305A (de) 1964-09-28
FR1386875A (fr) 1965-01-22
GB1027404A (en) 1966-04-27
SE303806B (de) 1968-09-09
DE1257981B (de) 1968-01-04

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