US3419743A - Electron tube having a tensioned cathode - Google Patents

Electron tube having a tensioned cathode Download PDF

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Publication number
US3419743A
US3419743A US513957A US51395765A US3419743A US 3419743 A US3419743 A US 3419743A US 513957 A US513957 A US 513957A US 51395765 A US51395765 A US 51395765A US 3419743 A US3419743 A US 3419743A
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United States
Prior art keywords
cathode
blocks
filaments
tube
filament
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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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US513957A
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English (en)
Inventor
Donald B Kaiser
Roth Robert
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RCA Corp
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RCA Corp
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Filing date
Publication date
Application filed by RCA Corp filed Critical RCA Corp
Priority to US513957A priority Critical patent/US3419743A/en
Priority to GB54197/66A priority patent/GB1141517A/en
Priority to DER44807A priority patent/DE1299079B/de
Priority to NL6617565A priority patent/NL6617565A/xx
Priority to FR87557A priority patent/FR1505101A/fr
Application granted granted Critical
Publication of US3419743A publication Critical patent/US3419743A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H01J1/15—Cathodes heated directly by an electric current
    • H01J1/18—Supports; Vibration-damping arrangements

Definitions

  • the filament is sutficiently long so that end portions thereof extend beyond the slots.
  • Clamping rings are provided for closing the open ends of the slots.
  • the end portions of the filament extending beyond the slots are melted to spherical shape having a larger cross sectional area than the space defined by the slots and the clamping rings, for confining the filament in the slots.
  • Spring means urge the metal blocks apart thereby tensioning the filament and causing the spherical ends to bear against the clamping rings.
  • This invention relates to electron tubes and particularly to an electron tube having a filamentary type cathode that expands and contracts axially in response to temperature changes.
  • the cathode comprises a plurality of rectilinear filaments engaged at opposite end portions and having intermediate portions extending through opensided slots or grooves in a metal block.
  • Each slot serves to form into a beam the electron emission from a cathode filament therein with reduced interference from the electron emission from adjacent cathode filaments for increased efiiciency.
  • the spacing between a cathode filament and the walls of a slot in which it is positioned is relatively small, so that a slight buckling of the filament in response to axial expansion thereof at elevated temperatures, may cause the filament to contact an adjacent slot wall. Such contact is objectionable because it will drain heat from the filament that is necessary for its emission and adversely affect the electrical characteristics of the tube.
  • the suspension means involves direct spring engagement with a filament
  • the proximity of the spring to the cathode may result in an appreciable heat transfer to the spring from the cathode at its operating temperature.
  • the resultant heating of the spring may anneal the material thereof and reduce its flexibility to such degree that it cannot keep the filament in satisfactory tension.
  • a spring engagement with each of a plurality of cathode filaments employed in a tube may render it difficult to insulate electrically the cathode from other tube elements in order to pass to each filament the requisite electric current for attaining its operating temperature.
  • a further object of the invention is to provide a cathode suspension system wherein a tensioning means is disposed in a location appreciably spaced from the cathode for isolating the tensioning means from cathode heat.
  • Another object is to facilitate electrical energization 3,419,743 Patented Dec. 31, 1968 of a cathode for heating the cathode to its operating temperature.
  • an electron tube having two generally cylindrical metal blocks axially spaced.
  • the outer sides of the two blocks are provided with a plurality of circumferentially spaced grooves or open-sided slots extending parallel to the axis of the blocks.
  • Elongated cathode strips or filaments are received in the slots and extend in spaced relation with respect to the walls of the slots and parallel to the axis of the blocks. End portions of the cathode filaments are anchored in retaining means provided on the sides of the blocks adjacent to their remote ends. Means are provided for urging the two blocks apart against the tension of the filamentary cathodes.
  • the active regions of the filaments may be limited to intermediate portions thereof appreciably spaced from the filament ends.
  • FIG. 1 is a sectional elevation of an electron tube having an improved structure in accordance with the teachings of this disclosure
  • FIG. 2 is an enlarged sectional fragment illustrating the structure for retaining the cathode filaments in axial tension
  • FIG. 3 is a view in elevation of apparatus that may be used in axially compressing the two metal blocks of the tube and fixing the cathode filaments thereto for preserving a desired axial compression of the blocks in the completed tube.
  • the electron tube shown in FIG. 1, by way of example, includes an anode 10, a cathode in the form of a plurality of directly heated filaments 12 and a two-part structure 14, 16 defined by peripheral portions of two metal blocks 18, 20.
  • the structure parts 14, 16 comprise opensided slots formed in the periphery of blocks .18, 20, each slot receiving a cathode filament 12.
  • the anode 10 and the two blocks 18:, 20, may be made of copper, preferably the OFHC type.
  • Each of the cathode filaments 12 comprises a base which may be made of any suitable metal such as an alloy known as Hastelloy having a melting point of about 1475 C. This alloy comprises by weight 2.5% cobalt, 4 to 6% iron, chromium, 26% molybdenum, 1% silicon, 1% magnesium, 0.05% carbon and the remainder nickel.
  • the base may be suitably coated for desired electron emission by sintering thereto particles made of a suitable metal such as nickel or tungsten for example.
  • the matrix formed by sintered metal particles is suitably impregnated with an electron emitting material such as barium.
  • the sintered coating may extend axially along the active portion of a filament which is the portion received in slots 14, 16 of the blocks 18, 20 as viewed in FIG. 1.
  • Two clamping rings 44 surrounding the array of filaments at each end thereof serve to keep the cathode filaments in this position.
  • the block 20 is provided with an axially-extending recess 22 open at its top end as viewed in FIG. 1 and having a closed bottom 24.
  • the block 18 also has an axially extending recess 26, of substantially the same diameter as recess 22 and with an open end adjacent to the open end of recess 22.
  • the other end of recess 26 is provided with an inwardly extending annular shoulder 28 having a function to be described.
  • an alignment and spacing member 30 made of insulating material such as aluminum oxide, for example.
  • spring means which for example may be in the form of Belleville springs 32, 34, each of which is made of a suitable spring material capable of retaining its spring nature at a temperature at least as high as 400 C.
  • springs 32, 34 has a generally concavo-convex shape. Springs of this type are well known in the art.
  • a metal plate 36 which also may be made of suitable spring material, may be interposed between the spring means 32, 34 and the adjacent end of member 30. Plate 36 may be omitted if the adjacent end of the member 30 has a sufiiciently large bearing surface.
  • each filament is engaged at its ends by mutually similar structures comprising metal support rings 38, each having an array of open-sided slots 16.
  • the periphery of the rings 38 are stepped to provide shoulders 42 (FIG. 2) thereon.
  • the metal rings 38 may be fixed to the blocks 18, 20 as by brazing.
  • the meta1 clamping ring 44 made of copper for example, is seated on the shoulder 42 and serves to close the sides of portions of slots 14, 16 above the shoulder 42 as viewed in FIGS. 1 and 2, and to restrain displacements of the filaments from the slots 14, 16.
  • Each cathode filament 12 has enlarged end portions 46, 48, which may be of spherical shape and which have a volume of appreciably larger transverse dimensions than the space between the bottom of a slot 14, 16 in ring 38 and the clamping ring 44. In this way, the filaments 12 serve to keep the blocks 18, 20 in compression against the force of spring means 32, 34.
  • the length of the cathode filaments 12 is preferably of a magnitude to provide a spacing 50 between the blocks 18, 20 of about 15 mils when the tube is cold.
  • the cathode filaments 12 are heated to a temperature of about 800 C. This results in a lengthwise expansion of the filaments of about 15 mils and an increase in the spacing 50 to about 25 mils. This is well within the compression limits of the spring means 32, 34.
  • the characteristics of the tube are determined when the tube becomes heated during operation. It is to be noted in this connection that the coefiicient "of expansion of the Hastelloy alloy of which the cathode filaments 12 are made is appreciably smaller than that of the copper blocks 18, 20. As a consequence, the 15 mils elongation of the filaments 12 when heated results in an increase of only about mils in the spacing 50.
  • the anode 10 is associated with a structure that provides suitable compensation for expansions and contractions of the cathode filaments 12 and relative axial movements of blocks 18, 20 in operation.
  • This structure as shown in FIG. 1, comprises an appreciable portion of the tube envelope and includes two metal rings 51, 52 fixed as by brazing to opposite ends of the anode 10 and to adjacent ends of two insulating rings 54, 56, made of aluminum oxide for example.
  • Two metal rings 58 and 60 are brazed to the other ends of the insulating rings 54, 56.
  • a welding ring 62, brazed to block 18 may be fixed as by welding to ring 60.
  • Between ring 58 and a metal ring 64 is an expansion compensation structure 66 suitably fixed as by welding to rings 58 and 64.
  • the compensation structure 66 forms part of the tube envelope, it is hermetically closed as by an annular weld 68.
  • the compensation structure 66 permits the envelope structure associated with the anode 10 to follow the relative movements of the blocks 18, 20 caused by expansion and contraction of the cathode filaments 12 during operation of the tube.
  • one block 18 is provided with an axial channel 70 in communication with a transverse channel 72 extending to the interior of the envelope of the tube.
  • An opening 74 defined by shoulder 28 affords communication between recesses 22, 26 in the blocks 20, 18 and channel 70 so that these recesses may be suitably evacuated.
  • An exhaust tube 76 is brazed to the walls defining channel 70 and after evacuation of the tube envelope, the exhaust tube 76 is closed as by a pinch 78.
  • Cooling means for the blocks 18, 20 may be in the form of radiators 80, 82.
  • the anode 10 may be cooled by a radiator 84.
  • FIG. 3 In assembling the tube shown in FIG. 1, a technique may be employed as shown in FIG. 3.
  • the two blocks 18, 20 are assembled with the insulating alignment and spacing member 30 disposed in the recesses 22, 26 of the axially aligned blocks and with the spring means 32, 34 and plate 36 disposed between recess bottom 24 and the adjacent end of alignment member 30.
  • the slot 40 in the support elements 38 is in alignment or register with a slot 14 or 16 in such block. This alignment is effected when fixing the support elements 38 to the blocks 18, 20.
  • the aligned slots 40, 14 in one block be in alignment with the aligned slots 40, 16 in the other block as shown in FIG. 1. This is accomplished by axially rotating the blocks 18, 20 relative to each other until the slots 40, 16 in one block are aligned or in register with the slots 40, 16 in the other block.
  • the cathode filaments 12 are then extended through the aligned slots in support rings 38 and in the two blocks until the filaments abut against a ring-shaped stop 90.
  • the two blocks are then urged toward each other against the force of spring means 32, 34 until the spacing 50 is reduced to 15 mils.
  • the vertical posit-ion of stop is adjustable by means of a sleeve 92 and a lock screw 94.
  • the stop 90 is spaced about 125 mils below the slots in the adjacent cathode support member 38.
  • the filaments 12 have such length, for example 1.500 inches, that when the lower ends thereof, as viewed in FIG. 3 abut against stop 90 their upper ends extend above the slots in the upper cathode support ring 38, a distance of about 125 mils.
  • the assembly is then enclosed in a bell jar 96 which may be made of glass, and an inert gas such as argon is introduced into the bell jar through a tubulation 98 to a flow of about 60 cubic feet per hour.
  • the compression elements 86, 88 on which the assembled parts are supported is rotatable either by manual or automatic means, not shown, in a path that brings successive end portions of the filament 12 in the upper end of the assembly as viewed in FIG. 3, in close spaced relation with respect to an electric torch 100.
  • the spacing between the torch 100 and an adjacent filament 12 was about 30 mils.
  • An electric current source of about 30 amperes was used and the blocks 18, 20 were axially rotated at a velocity of one revolution per 20 seconds.
  • the blocks were rotated at a velocity of one revolution per five seconds, the spacing between the torch 100 and an adjacent cathode was 5 mils, and an electric current source of 75 amperes was used.
  • each cathode filament end portion As each cathode filament end portion is brought into proximity to the torch 100, the entire end portion of the filament becomes molten and assumes the shape of a sphere. The melting proceeds to a region close to that in which the filament emerges from the upper end of slot 40 as viewed in F-IG. 2. Melting of the cathode filament 12 below this region is prevented by the cooling effect imparted to the filament by the support ring 38 and the clamping ring 44. When a sphere so formed cools down to room temperature, it is in actual bearing contact with respect to the two rings 38, 44, as viewed in FIG. 2.
  • the assembly comprising the blocks 18, 20 and their associated parts including the filaments 12, is inverted and repositioned between compression members 86, 88, and axially compressed.
  • the stop 80 is then raised to engage and urge the previously formed spheres- 46 in the filaments, against the adjacent ends of the support ring 38 and clamping ring 44, as viewed in FIG. 3.
  • the assembly is then rotated under the conditions previously described to form spheres 48 (FIG. 1) at the upper ends of the filaments 12 as shown in FIG. 3.
  • the spring means 32, 34 serve to keep the cathode filaments 12 in tension at all temperatures to which the filaments may be subjected.
  • the welding ring 62 is fixed as by brazing to the upper portion of the block 18 as viewed in FIG. 1, and the welding ring 63 is similarly fixed tothe lower portion of the block 20.
  • the three parts of the envelope assembly comprising anode and envelope parts 60, 54, 50, 52, 56, 58, 66 and 64, are suitably joined as by brazing to form a tubular structure that can be telescoped downwardly upon the cathode assembly as shown in FIG. 1, until the flanges on welding ring 62 and metal envelope part 60 are in register.
  • the envelope parts referred to are so dimensioned that when such register occurs, the lower end of metal envelope part 64 will be flush with a flange on welding ring 63.
  • the two adjacent flanges on welding ring 62 and on envelope part 64 are then joined as 'by welding, and the lower end of envelope part 64 as viewed in FIG. 1 may be fixed to ring 63 as by welding.
  • the radiators '80, 82 may then be aflixed to blocks 18, 20 respectively, as by being brazed thereto.
  • the anode radiator 84 may be attached as by brazing, to the anode either before or after completion of the tube assembly.
  • the interior of the tube envelope is then evacuated through exhaust tubulation 76 which is appropriately closed as by the pinch-off 78, after evacuation has been completed.
  • An electron tube having:
  • An electron tube comprising:
  • said envelope being evacuated and including one portion fixedly sealed to one of said axially movable end portions and another portion fixedly sealed to the other of said axially movable end portions, and
  • An electron tube having:
  • An electron tube having:

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  • Solid Thermionic Cathode (AREA)
  • Electron Sources, Ion Sources (AREA)
  • Lasers (AREA)
US513957A 1965-12-15 1965-12-15 Electron tube having a tensioned cathode Expired - Lifetime US3419743A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
US513957A US3419743A (en) 1965-12-15 1965-12-15 Electron tube having a tensioned cathode
GB54197/66A GB1141517A (en) 1965-12-15 1966-12-02 Electron tube
DER44807A DE1299079B (de) 1965-12-15 1966-12-14 Direkt geheizte Kathode fuer eine Elektronenroehre und Verfahren zu ihrer Herstellung
NL6617565A NL6617565A (cs) 1965-12-15 1966-12-14
FR87557A FR1505101A (fr) 1965-12-15 1966-12-15 Tube électronique perfectionné

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US513957A US3419743A (en) 1965-12-15 1965-12-15 Electron tube having a tensioned cathode

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US3419743A true US3419743A (en) 1968-12-31

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US513957A Expired - Lifetime US3419743A (en) 1965-12-15 1965-12-15 Electron tube having a tensioned cathode

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US (1) US3419743A (cs)
DE (1) DE1299079B (cs)
FR (1) FR1505101A (cs)
GB (1) GB1141517A (cs)
NL (1) NL6617565A (cs)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5666018A (en) * 1993-07-27 1997-09-09 Thomson Tubes Electroniques Cathode with fast heat switch-on and switch-off mechanism and grid-type electron tube including such a cathode

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2385435A (en) * 1944-10-23 1945-09-25 Westinghouse Electric Corp Electron discharge device
US2542639A (en) * 1948-11-23 1951-02-20 Gen Electric Electrode structure for electric discharge devices
US2570121A (en) * 1949-05-26 1951-10-02 Rca Corp Nondeforming laminated electrode support and electron discharge device
US2726349A (en) * 1952-01-02 1955-12-06 Itt Filament support

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE895476C (de) * 1943-09-24 1953-11-02 Siemens Ag Gluehkathode
DE839235C (de) * 1950-08-20 1952-05-19 Siemens Ag Elektronenroehre, insbesondere Senderoehre
US2719244A (en) * 1952-01-25 1955-09-27 Westinghouse Electric Corp Electrical discharge tube
DE1061449B (de) * 1958-07-16 1959-07-16 Iapatelholdia Patentverwertung Elektronenroehre
NL113253C (cs) * 1960-10-14
FR1442819A (fr) * 1964-07-31 1966-06-17 Philips Nv Bloc cathodique à chauffage direct pour tube à décharge électrique

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2385435A (en) * 1944-10-23 1945-09-25 Westinghouse Electric Corp Electron discharge device
US2542639A (en) * 1948-11-23 1951-02-20 Gen Electric Electrode structure for electric discharge devices
US2570121A (en) * 1949-05-26 1951-10-02 Rca Corp Nondeforming laminated electrode support and electron discharge device
US2726349A (en) * 1952-01-02 1955-12-06 Itt Filament support

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5666018A (en) * 1993-07-27 1997-09-09 Thomson Tubes Electroniques Cathode with fast heat switch-on and switch-off mechanism and grid-type electron tube including such a cathode

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Publication number Publication date
GB1141517A (en) 1969-01-29
NL6617565A (cs) 1967-06-16
DE1299079B (de) 1969-07-10
FR1505101A (fr) 1967-12-08

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