US2372037A - Thermionic device and means and method of fabrication - Google Patents

Thermionic device and means and method of fabrication Download PDF

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Publication number
US2372037A
US2372037A US462342A US46234242A US2372037A US 2372037 A US2372037 A US 2372037A US 462342 A US462342 A US 462342A US 46234242 A US46234242 A US 46234242A US 2372037 A US2372037 A US 2372037A
Authority
US
United States
Prior art keywords
cathode
shell
stem
heater
sealed
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
US462342A
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English (en)
Inventor
Jr Ward W Watrous
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.)
Westinghouse Electric Corp
Original Assignee
Westinghouse Electric 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
Priority to BE474305D priority Critical patent/BE474305A/xx
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Priority to US462342A priority patent/US2372037A/en
Priority to GB15629/43A priority patent/GB571709A/en
Application granted granted Critical
Publication of US2372037A publication Critical patent/US2372037A/en
Priority to FR988431D priority patent/FR988431A/fr
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
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H01J17/02—Details
    • H01J17/04—Electrodes; Screens
    • H01J17/06—Cathodes
    • H01J17/063—Indirectly heated cathodes, e.g. by the discharge itself
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H01J17/02—Details
    • H01J17/04—Electrodes; Screens
    • H01J17/06—Cathodes

Definitions

  • the major difficulty in the use at higher cathode potentials is the fact that as soon as anyportion of the cathode, which has attained an emitting temperature, assumes a potential in excess of approximately twelve volts t'instantaneous) in respect to any other: portion of the cathode, the gas or vapor content: of the tube mentioned the fact that the. insulation 01 that.
  • An object. of the invention accordingly is to avoid the drawbacks of a heavily coated heater filament.
  • Another object of the invention is to provide a cathode which will avoid arcing with a cathode potential in ex'cessof present-day usual voltage ior' heater purposes of indirectly heated cathodes.
  • a iurther obiectof the invention'isto provide a cathode of the character indicated which is of practical manufacture and assembly.
  • a still further object offlthe invention is to provide a cathode of the characterindicated utilizing -a heater within the same which is. prevented from arcing, to the cathode in use with high potentials.
  • Another object of the. invention is'to enable a, cathodev heater to" be situated in vacuum in a gas or vapor filled tube;
  • an object of the invention is toVprovide an improved method oi fabrication of a tubeiulfillingathe above objects-in whole or in
  • an object of the invention is to provide apparatus. for. evacuating the cathode-heaterregion: and seal the same against. ingress: of th gas or vapor of the. discharge tube.
  • Figure l a vertical sectional view of a thermionlc device wherein my improved cathode is shown. in longitudinal section; v
  • Figure 2 is a cross-sectional view on the line II'--II of Fig. 1;; a
  • Figure 3 is: a vertical elevational view of" a cathode and associated parts viewed as indicated by" arrows III--III'of Fig. I, and showing a modified configuration of cathode;
  • Figure 4 is a. cross-sectional view on the.- line net-Iv of Fig. 1; v
  • Figure 5 is a sectional elevation. of apparatus for evacuation of. the cathode-heater region, and showing" a cathode andv associated partssituated therein. for evacuation; and,
  • Figure-61s a. modified construction or cathode lnaivinov tribulation connection showntherewith tor'purposes of evacuation.
  • the reference numeral l designates a glass or other envelope having a base ll thereon and a stem l2 therein as customary in the art.
  • the stem is illustrated as having a collar clamp 13 thereon from which extend upwardly supporting rods M in turn mounting a grid I5 of foraminous material in the region above the stem and within the envelope.
  • An anode I6 is depicted at the upper part of the envelope within a cylindrical extension ll of the grid.
  • a cathode in accordance with the present invention is situated coaxially within the grid and has support from the stem.
  • "Said cathode is preferably a hollow metallic shell providing a cylindrical wall l8 the upper end of which is closed by an end wall I9 shown as integrally,
  • of generally cylindrical shape and longer than the shell.
  • the end wall IQ, of the shell has an appropriate pocket 22 pressed therefrom to receive and position the end of said insulator 2
  • a transverse disc-shaped metallic plate 23 which has a central orifice somewhat larger than the diameter of the aforementioned insulator 21 but of less diameter than the said shell.
  • said plate is impressed with an annular trough 24, of ample capacity for receiving the said end of the shell and a continuous filling of solder 25 bywhich a vacuum-tight seal is obtained between the shell and plate.
  • Use of plate 23 promotes inductive heating formelting the solder during fabrication and constitutes a shield be-. tween the stem and lead-in wires and the main part of the interior of the-envelope where ionizationtakes place .in use of .the device.
  • a sleeve .26 Projecting from below and into the orifice of said plate and sealed to said plate by welding or otherwise, is a sleeve .26 constituting amountingmeans for the cathode.
  • the lower part of said mount-. ing. meansor sleeve 26 shoulders outward and.
  • said sleeve is .an integral piece of material of cylindrical shape having a coefficient of expansion which is sub-. stantially thatof the glass of the press. .Material sold inthe trade under the trade-name of Kovar may well be used for the purpose.
  • an intervening collar of insulative material 28 which according positions the insulatorcoaxially with respect to the sleeve, plate and shell.
  • a heater filament 29 such as a coiled spiral shown, is wound around the insulator 2
  • Theinsulator is shown as having a central bore therethrough thereby enabling an upper end connection for the heater filament to be extended downwardly therethrough and to protrude into the region confined by the enlargement of the sleeve. and its seal withthe stem.
  • Theotherend of the filament coil has a connection which extends downwardly into this same region by passing between the insulator and said collar 28.
  • the filament may be coated with a thin layer of insulation if desired as a precaution against short circuiting between parts thereof which nections are secured to appropriate lead-in wires 38, 30 which are sealed through the stem in usual manner.
  • the regions within the shell N3 of the cathode and between the sleeve and the stem are intercommunicating due to the looseness of the collar and insulator and of the filament wire connection within each, or otherwise as found desirable as by communicating holes or grooves, so that evacuation of the one region obtains evacuation of both. It will be observed that said regions are wholly confined so that a vacuum may be maintained therein. Such a vacuum is provided, and in consequence thereof it is now to be observed that the heater filament is operating in a vacuum irrespective of what pressure. of gas or vapor may exist on the ex-v terior of the cathode within the envelope.
  • the ;particular device shown is one wherein the envelope is evacuated to remove the air therefrom and thereafter'has a gas of desired character and quantity admitted into the envelope before sealing,
  • the completed device consequently comprises a tube containing a gaseous atmosphere and having therein an evacuated enclosure for a heater which is thus operating in vacuum while the surrounding part of the tubeis operating with gas present.
  • the heater voltage therefore will have no opportunity to cause gas breakdown even though that voltage "-1 is, considerably higher than ordinarily used in present-day practice.
  • the structure accordingly enables metoaccomplish the desired result of operating the filament heater at considerably more than seven volts, so that I am' enabled to connectthe filament direct to commercial lines and operate the device with 110, 220 or other voltages if so desired. 1
  • the outside of the collar is threaded at 36 to receive a threaded coupling ring 31.
  • the collar 35 and coupling ring 36 have inwardlydirected flanges 38, 39 respectively adaptedzto tightly clamp therebetween a rubber orotherwasherfifl superposed upon an annular lit at an inwardly directed insulative, nipple 4a io-rmed with a tapered inner end 43 constitutin atemporary seat for the lower end of, the stem i2.
  • Said nipple also has a.
  • a .structure of cathode capable of evacuation through tubulation' is illustrated in Figure 6. Furthermore in this modified construction, evacuation is not extended to include the region between the cathode and stem, but is confined to the region within the cathode only. Describing this modification more in detail, stem l2a is provided with an upper cylindrical neck 49 around which is mounted the lower end of a metallic cylindrical sleeve 50 having appropriate fit there-, on for the purpose. The upper part of said sleeve projects above the neck portion of the stem and overlaps the lower end of a cylindrical cathode 'shell l8a to which it is welded or otherwise secured.
  • the cathode shell in this instance is shown as tubular and of course electron emissive on its outer surface, and is closed at both ends by headers or end walls of which the upper one is identified as upper end wall Na and the lower one is identified as bottom end wall 5
  • a filament 29a is shown as wound spirally around the insulator, the upper end of the spiral being connected through a lateral slot 54 next the upper end of the insulator to make electrical connection downwardly through a central bore of the insulator and outwardly through another lateral slot 55 to a lead-in wire 56.
  • the lower end of the spiral part of the filament makes connection to another lead-in wire 51.
  • Said lead may be in the range, say from 50 to 5000 microns.
  • the cathode shell provides means for evacuation of the interior region of: the cathode shell. by virtue of, the passage madeby the presence-v of. slot Minthe insulatnr .ot the aforementioned opening ea in; the upper endwall, Tubulation 60 is, preferablymetal and after evacuation has been. accomplished, tubulation. is pinched and sealed together closeh; above the said upper wall and tubulation severed at; or above the pinched, sealed portion-
  • the interior region is accordingly readily evacuated and. maintained in the evacuated conditi0n.s0 that the assembly can be completed by addition'of the grid, as in Fig. 1, to the stem and the stem sealed within the envelope.
  • cathode shell l8 and la hasbeen defined as cylindrical, it is to be understood that other shapes and configurations of hollow cathode may be employed of which an additional example i given in Fig. 3.
  • the cathode shell l8b is shown as having a corrugated wall. which constitutes one illustration not only of a. different. configurationof cathode, but also of a cathodeof limited length having increased emissive surface. Except for this difference in. Fig. 3, this viewmay be considered an elevation of the cathodeand stem assembly otherwise shown in Fig. 1, its lower end being sealed in trough 24 of plate 23 as in that figure. I f
  • the pressure difference should be in the range, say from 25 to 760 mm.
  • the cathode is evacuated the pressure difference thereof from the body of the envelope
  • gases that are contemplated are xenon, krypton, neon, argon, helium, nitrogen,
  • the invention accordingly is exemplified in either construction, namely, a radical difference of pressure is. maintained between the interior of the cathode and the interior of the body of the envelope.
  • the tube will therefore operate in the part or the. voltage-pressure curve well above the low dip of the curve and in the parts of the curve tapering toward infinity.
  • a cathode comprising a hollow shell having an exterior emitting surface, a heater within said shell, means closing the upper end of said shell to external pressure, means closing the bottom end of the shell to external pressure, and means rigidly carried by the respective closing means at both the upper and bottom ends of said shell, centering said heater coaxially therein, said shell maintaining pressure withinthe same different than pressure outside said cathode.
  • a cathode comprising a hollow shell, an upper end wall for'said shelLsaid end wall having a centrally disposed pocket therein; an insulator longitudinally situated in said shell and projecting at its upper end into said pocket, and means at the lower endof said insulator positioning said insulator coaxially of the cathode and sealing the cathode to maintain a vacu therein.
  • a cathode and stem assembly comprising a glass stem having a sleeve sealed thereto, a plate transverse to and sealed to said sleeve, said plate having an annular trough therein, a closed cathode shell having one end thereof sealed in said trough, and a heater within said shell, said stem, sleeve and shell providing a confined region and said region being evacuated thereby preventing ionization and discharge between the heater and cathode.
  • a cathode comprising a hollow shell, an end wall at each end of said shell sealed thereto, each end wall having a pocket, an insulator longitudinally situated in said shell and carried at its ends in saidv pockets, and a tubulation sealed to one of said pockets, said pocket to which said tubulation is sealed having an opening from the interior of the shell into said tubulation for evac-' uationpurposes, said hollow shell being evacuated and said tubulation pinched and sealed closed for maintaining the vacuum in said shell, and a heater on said insulator within said shell and operating in the vacuum in said shell.
  • a method of fabrication of a hollow cathode for mounting said cathode on a stem and evacuating the cathode comprising positioning a cathode in a trough carried by the stem, providing solder in position to flow around said cathode in said trough, placing a dome over the cathode and stem temporarily sealing the dome and evacuating the same, and melting said solder and causing it to seal the cathode in said trough for maintaining the acuum within said cathode and the cathode assembled on the stem.

Landscapes

  • Closing Of Containers (AREA)
  • Manufacture Of Electron Tubes, Discharge Lamp Vessels, Lead-In Wires, And The Like (AREA)
US462342A 1942-10-17 1942-10-17 Thermionic device and means and method of fabrication Expired - Lifetime US2372037A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
BE474305D BE474305A (enrdf_load_stackoverflow) 1942-10-17
US462342A US2372037A (en) 1942-10-17 1942-10-17 Thermionic device and means and method of fabrication
GB15629/43A GB571709A (en) 1942-10-17 1943-09-23 Improvements in or relating to thermionic devices
FR988431D FR988431A (fr) 1942-10-17 1947-07-12 Dispositif thermoionique et procédé de fabrication

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US462342A US2372037A (en) 1942-10-17 1942-10-17 Thermionic device and means and method of fabrication

Publications (1)

Publication Number Publication Date
US2372037A true US2372037A (en) 1945-03-20

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Family Applications (1)

Application Number Title Priority Date Filing Date
US462342A Expired - Lifetime US2372037A (en) 1942-10-17 1942-10-17 Thermionic device and means and method of fabrication

Country Status (4)

Country Link
US (1) US2372037A (enrdf_load_stackoverflow)
BE (1) BE474305A (enrdf_load_stackoverflow)
FR (1) FR988431A (enrdf_load_stackoverflow)
GB (1) GB571709A (enrdf_load_stackoverflow)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2463372A (en) * 1945-10-03 1949-03-01 Jr Peter W Forsbergh Cathode structure for magnetrons
US2498775A (en) * 1948-01-16 1950-02-28 Westinghouse Electric Corp Cathode construction
US2507812A (en) * 1945-08-17 1950-05-16 Cossor Ltd A C Thermionic cathode
US2677787A (en) * 1950-05-08 1954-05-04 Charles V Litton Electron discharge device cathode assembly
US2740916A (en) * 1954-09-01 1956-04-03 Garner J Hooper Vacuum tube with replacement filaments

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2507812A (en) * 1945-08-17 1950-05-16 Cossor Ltd A C Thermionic cathode
US2463372A (en) * 1945-10-03 1949-03-01 Jr Peter W Forsbergh Cathode structure for magnetrons
US2498775A (en) * 1948-01-16 1950-02-28 Westinghouse Electric Corp Cathode construction
US2677787A (en) * 1950-05-08 1954-05-04 Charles V Litton Electron discharge device cathode assembly
US2740916A (en) * 1954-09-01 1956-04-03 Garner J Hooper Vacuum tube with replacement filaments

Also Published As

Publication number Publication date
GB571709A (en) 1945-09-05
BE474305A (enrdf_load_stackoverflow)
FR988431A (fr) 1951-08-27

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