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Publication numberUS2615137 A
Publication typeGrant
Publication dateOct 21, 1952
Filing dateJan 5, 1946
Priority dateJan 5, 1946
Publication numberUS 2615137 A, US 2615137A, US-A-2615137, US2615137 A, US2615137A
InventorsStephen M Duke
Original AssigneeStephen M Duke
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
High-power vacuum tube
US 2615137 A
Abstract  available in
Images(3)
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Claims  available in
Description  (OCR text may contain errors)

Oct. 21, 1952 v s. M. DUKE 2,615,137

HIGH-POWER VACUUM TUBE Filed Jan. 5, 1946 5 Sheets-Sheet l INVENTOR fi/e a/ze/v M 00/6? BY WXM ATTORNEY.

Oct. 21, S, M, DUKE HIGH-POWER VACUUM TUBE 3 Sheets-Sheet 2 Filed Jan. 5, 1946 F1E EI INVENTOR. fi/e a/zen M fiz/le W i M ATTORNEY,

Oct. 21, 1952 s. M. DUKE 2,615,137

HIGH-POWER VACUUM TUBE Filed Jan. 5, 1946 3 Sheets-Sheet 3 INVENTOR. 5/6 0560 M 90/46 Fl IE3 El BY 14 W ATTORNEY.

Patented Oct. 21, 1952 HIGH-POWER VACUUM TUBE Stephen M. Duke,

Harwell Didcot, Berkshire, England Application January 5,1946, Serial "No. 639,276

13 Claims.

The present invention relates to electrical dischargeapparatus in general and more particularly to high power vacuum tubes of the water-cooled typ'e.

Itisan object of the present invention to provide an improved "high power vacuum tube built and assembled in such fashion that it can be taken apart and repaired inthe field without the aid of factory toolsand facilities.

Another object of this invention is to provide the high power vacuum tube of improved construction giving a high degree of accessibility of the operative elements and improved electrical characteristics. j 1

Still another object of this invention is to pro vide a high powervacuum tube of the watereooledtype with characteristics which lend its application as a high power, high voltage regulator tube of theflosser type.

Another object of this invention is to provide a high power vacuum tube of improved cathode construction.

Still another object of this invention is toprovide a high power vacuum tube of improved grid electrode construction. Otherand further objects of this: invention will be, apparent to those skilled in the art to which it relates from the following specification, claims and drawings.

In the drawings, briefly, Figure lis a longitudinal sectional .view of-one embodiment of the hi h power vacuum tube of thisinvention;

,Fig. 2 is an end view ofthe high power vacuum tube looking at the tube from the anode end; ,1Figa3 is amend view of the higl-ipowervacuum tube looking at the tube from the cathode. terminalend; i g

Fig. 4 is a sectional view .takenalong the line 4 -4 of Fig. 1" 7 Fig. .5 is a sectional view 'takenlalcng the line 5- 5 of Fig; 1,; i V

Fig. 6 is a. sectional view taken along the line 6-5 QffFi'g'Q 17; i

Fig. '7 is a sectional view taken along the. line 'L-T OfIFig. 1; I Fig. 8.15 a sectional 8-8 ofFi'gljand i i v Fig. 9' aisectional view taken along the line '9 '9of1?ig;1.v I g Referring to. the drawingsl'i'n, detail, reference numeral. 10 designates a brass, jfack'etof tubular cross section, concentric; with and displaced from the high power vacuum? tube anode Jljl s o as to provide a water jacket :space .12 therebetwen. this jacket being connected to'the water maniikv taken alon he m 2. fo1dsl3 and M which are connected to the water circulating plumbing, not shown, associated with the threaded pipe 15 and the flanged pipe [6. One end of the anode II is hard-soldered to the outer periphery of the annulus [1, this annulus having a large-size aperture substantially in the center thereof which is hard-soldered to the evacuation manifold l8. This evacuation manifold I8 is hard-soldered to a ring I9; the outer periphery of which slidably engages a soft rubber gasket 20 clamped between the rings 2| and 22 by nut and bolt elements 23, the ring 2| being soft-soldered to the end ofthebrass jacket I0 to define together with thering l9, one end of the water manifold M, the gasket 20 functioning to form a water-tight seal between the rings [9 andZl. l

The water jacket l3 cast of brass or similar material, is hard-soldered to the tubular casing 1-0 and is provided with flanges 24 and 25 the flange 24 functioning as a support for the high power vacuum tube and the flange 25 functioning to engage the peripheral portions of theannulus- 2'8 and being held in close engagement therewith by means of the bolts 27, a gasket 28 of soft rubber being disposed in water-sealing relation between the members 2-5 and 26. One end of the anode l I is seated in an annular groove in the lower face of the annulus 26 and is hardsoldere'd thereto. Threaded into the aperture of the annulus 2 6 is an electrostatic tubular metal Shield 2-9 extending well into the porcelain tubular insulator 30, the ends of which are flared outwardly gradually. Each end of the porcelain tubular insulator 3i) is adapted to be engaged by annular members 31 and 32. The annular member 3| is made up of a split ring (Ho and annulus 3th, the annulus 3'lb being provided with an in wardly extending flange 3lc for seating in a corresponding groove formed in the split ring 310, the purpose of this construction being to permit the split ring 3;! a to be expanded and slipped over the end of the insulator 30 and thereafter to be fitted into the annulus 3 lb, the'annulus Bib having' an aperture big enough to clear the end .of the insulator 30. Likewise the amiular member 32 is formed of asplit ring 32a and an annulus 32b having an inwardly extending flange .320 for the same purpose. One end of the insulator 31) is held in sealedrelationship with 'resp'ectlto the annulus .26 by me'ansof suitable gaskets ,33 compressed therebetween by the clampingaction ofthe annular member 3 I attached to the, annulus 25 by 'thebolts-3'4; Likewise the other end ofthe insulator 30' is sealed to thecopper top plate 36' by 3 'means of gaskets 3! compressed therebetween by the annular member 32 fastened to the end plate 36 by bolts 35. The plate 36 is therefore insulated from the annular member 26 and the anode l I by the porcelain insulator 30.

The stainless steel tubular grid support 38 is attached to the ring member 39 which is attached to the end plate 36 by machine screws 40. The other end of this grid support tube is attached to the steel grid frame 4| which supports the molybdenum grid shield 42 and the molybdenum grid rods 43, of which there are nine. One end of each of the grid rods 43 is positioned in appropriate apertures formed in the grid support 4| so as to leave surfaces of .lar displacement being to provide clearance bethe grid rods between these apertures exposed to the gripping action of the steel tightening grid rods 43 are inserted into the apertures provided therefor. The other ends of the grid rods 43 are inserted into suitable apertures formed in the tongues 45 of the grid rod spacer 46 and both these tongues 45 and the end portions of the grid rods 43 are deformed so that pin-receiving spaces are provided therebetween into which the short tapered pins 41 are fitted for the purpose of locking the grid rods 43 and the tongues 45 together in assembled relation. Around the grid rods 43 is wound the spiral grid 48 consisting of a plurality of spaced turns of molybdenum wire of 0.02 inch diameter, these turns being held in proper spaced relation by spacing wires 49 consisting of turns of molybdenum wire of 0.01 inch diameter spiraled around each of the grid rods 43 so as to bind the grid wire 48 in place on these grid rods.

The cathode of this high power vacuum tube consists of a plurality of electron emitting wirelike elements 50 disposed in spaced relation substantially in a circle inside of the grid electrode structure as shown in Fig. 8. Tie wires-5i of substantially triangular configuration, formed of molybdenum wire of 0.01 inch diameter, are employed to tie the cathode wires into three groups at intermediate portions thereof. These tie wires 5| are spaced from each other longitudinally of the cathode wires by a distance of approximately inch, so that for cathode wires of approximately 9 inches in length these tie wires are positioned approximately 3%; inches from the ends of the cathode wires, which ends are anchored in tongues 52 of the plate-like member 53 which is positioned well inside of the grid rod spacer 46, as shown in Fig. 9. The tongues 52 are deformed as are also the ends of the cathode wires 50 so that pin receiving apertures are formed therebetween for the taperedpins 54 which hold thetongues 52 and the cathode wires 58 in assembled relation. The member 53 is also of electrically conducting material, being formed specifically of molybdenum. The other ends of the cathode wires 58 are anchored in filament strips 55 which are also deformed together with these ends of the cathode wires 50 to provide pin receiving apertures for receiving the tapered pins 56 which hold the cathode wires and the strips 55 in assembled relation- It will be observed that certain of the molybdenum filament strips 55 are of different lengths from the others so that these strips may be fastened by machine screws ET-to different ones of the copper filament contactplates 58. Three of these filament contact plates are provided and each plate has three projections 59,

tween the filament strips 55, to hold the cathode wires 50 in parallel spaced relation and to provide connection between the cathode rods 50 and a source of polyphase current supply. As was pointed out previously, the cathode rods 58 are connected into three groups by the tie Wires 5| so that every third one of the cathode wires 50 is in the same group, as shown in Fig. 8, and all of the cathode rods 50 of the same group are connected to the same one of the cathode plates 58 as is apparent from Figs. 5, 6 and 7. Accordingly, these copper plates 58 function to tie the cathode wires 58 togetherinto groups at the power feeding ends of the cathode wires. The plates 58 are insulated from each other by insulation bushings of Lavite disposed therebetween and supported in suitable apertures thereof. The Lavite insulation spacers 60 are machined and fitted to the apertures formed in the plates 58 so as to form a well-fitting unitary structure. Three-phase power is fed to the cathode structure through tubular members GI and busbar connector!!! clamped thereto. These tubular conductors 6| are hard-soldered to selected ones of the copper cathode plates 58 so that one of these tubular conduct0rs 6| is hard-soldered to each of the plates 58 as shown in Figs. 5, 6 and 7, but is insulated from the others of said copper plates 58 by the Lavite bushings 60. Thus the plates 58 are connected to different phases of the three-phase power supply through the tubular conductors 6|, all of which alsofunction as a well braced support for the entire cathode structure. Auxiliary tubular members 62 are provided in each of the tubular conductors 6| for the purpose of feeding cooling water into the cathode ends of the tubular conductors 6| and it will be observed that the auxiliary tubular members 62 are of somewhat smaller cross section than are the tubular conductors 6| so as to provide clearance between the outside diameter of the auxiliary tubular members 62 and the inside diameter of the tubular conductors 6|. The cathode ends of the tubular conductors 6| are sealed by small'plugs 63 of copper hard-soldered into the" ends of the tubular conductors 6|. Furthermore, a molybdenum contact shield 64 is attached'to the inher surface of the innermost copper ,plate58.

The tubular conductors 6| are supported in spaced relation in apertures of the insulator 65 by means of the stainless steel sleeves 66 which are soft-soldered thereto. The porcelain insulator 65 is soft-soldered in vacc'umtight relation to the end plate 36. Caps 6'! threaded to the end of the tubular conductors Bi and sealed thereto by red lead water-tight joints are provided with tubular connections 68 and 69 for feeding cooling water into the auxiliary tube62 and removing it from the clearance space between the tube 6! and the tube 62. v

operation, the high 'pcwervaeuum tube of this invention is supported vertically so that the cathode power connections are uppermost and the vacuumpump connection is at the bottom or the tube. For this purpose the flange 24 is provided and this flange is adapted'to engage a suitable support, not shown. Connections'to the amide of this high power vacuum tube "may'be mad to the flange 24 and inasmuch as the anode of this vacuum tube is adapted to be energized at voltages of the order of 20,000 volts it is obvious that the anode of this tube must be insulated from ground unless the positive terminal or the high voltage power supply is also "grounded. In cases where the ositive terminal of the power supply is grounded, then of course the cathode power-supply must be insulated from ground.

Connections to the gl' id or this high power vacuum tube are made to theJplate BG and for this purpose such connections may be anchored atany ollepf the bolts 35. This plate 36 is connected to the grid through the grid support 38 and is'insulated from the anode by the. insulator 30 and from the cathode by the insulator Cooling medium is fed to the anode jacket through the pipe and removed through the pipe l5 and in cases where the tube is to be employed with the'anode insulated fromsground,

suitable lengths of porcelain tubing must be in- ,Y

*serted into the plumbing of the cooling medium to provide a sufficient length of water column between the high voltage anode and the grounded water supply.

While there has been set with in the foregoing specification and drawing a referred emof said tubular anode, "a "substantially tubular member surrounding said tubularra'node "and slightly displaced therefrom,sai d tubular memher having means for sealing the ends thereof 'tosaid ring-shaped members to 'forma-wa'tertight jacket around said tubularanode, plumbing connections provided to said water-tight jacket for circulating cooling medium through said jacket around said anode, a grid'e'lec'trod'e positioned inside of-said anode and coaxially disposed with respect to said anode, said 'grid electrode comprising "a wire spiral supported upon a plurality of parallel spaced rod-like members, a metallic spacer member for engaging one set or ends of said rod-like members, a perforated annular member for receiving the other '"set of end'sof said rod=like members in the perforatio'n-s thereof, ajmetallic sleeve attached to said annular member, "a- "hollow electrical insulator "sealed to the uppermost "of "said 'ringtshaped members and surrounding said metallic sleeve,

a metallic end plate attached to the "other end or said hollow insulator and t the "other -end o f-said metallic sleeve, a plurality of tubular fluidcooled conductors, insulation means for supporting saidhollow fluid-cooled conductorsin "said'end plate andinside of saidmetallicsleev'e, "a cathode assembly including "a plurality of rods positioned longitudinally of said g'rid electrode, and means for connecting "said cathode asscmblyto said'fluid cooled conductors whereby 6 said cathode is susp'ended in position by said fluid cooled conductors.

2. A high "power fluid-cooled vacuum tube comp'rising a tubular anode, a watertight jacket around said tubular anode, plumbing connections provided to said water-tight jacket for circulating cooling medium through said jacket around said anode, a grid electrode positioned inside of said anode and coaxially disposed with respect tosaidanode, said grid electrode comprising a plurality of parallel spaced rod-like members, a Wire spiral about said plurality of members, and a wire Wound about each of said members engaging said wire spiral and securing it in position about said members, a metallic spacer membet for engaging one set of ends of rod-like members, a perforated annular member for receiving the other set or ends of said rod-like members in the perforations thereof, a metallic sleeve attached to said annular member, a hollow electrical insulator sealed to said tubular anode and surrounding said metallic sleeve, a metallic 'end plate attached to the other end of said -hol low insulator and to the other end of said metallic sleeve, a plurality of tubular fluid-cooled conductors, insulation means for supporting-said hollow fluid-cooled conductors in said end plate and inside of said metallic sleeve,-and acathode structure suspended from said fluid cooled "conductors and positioned longitudinally of and interior to said grid electrode.

of said anode and coaxially disposed with respect to said anode, said grid electrode comprisin'g a'w'ire spiral supported upon a plurality of parallel spaced rod-like -members, a metallic spacer member for engaging one set of ends of rod-like members, a, perforated annular member for receiving the other set of ends of said'rod like members in the perforations thereof, a hollow electrical insulator'sealed to one of said rin shaped plate members, a metallic end plate attached to the other end of said hollow insulator for supporting said grid electrode, a plurality of tubular fluid-cooled conductors, insulation means "for supporting said hollow fluid-cooled conductors in said end plate and inside of said hollow insulator, a plurality of cathode rods positioned longitudinally of said grid electrode, and means for; connecting said plurality of cathode rods to said fluid-cooled conductors.

4. A high power fluid-cooled vacuum tube comprising a tubular anode, a pair of ring-shaped plate members attached one to 'each end ofssa'id means for sealing the ends thereof to 'said ringshaped members to form a water-tight jacket around said tubular anode, plumbing connections provided to said water-tight jacket for circulating cooling medium through said jacket around said-anode, a grid electrode positioned inside of said anode and co'ax-ially disposed with respect to said anode, said grid electrode comprising a plurality of parallel spaced rod-like members, a wire spiral about said plurality of members, and a wire wound about each of said members in fixed relation thereto and engaging said Wire spiral whereby said spiral is secured about said members, a perforated annular member for receiving one set of ends of said rod-like members in the perforations thereof, a metallic sleeve attached to said annular member, a hollow electrical insulator sealed to the uppermost of said ring-shaped member and surrounding said metallic sleeve, a metallic end plate attached to the other end of said hollow insulator and to the other end of said metallic sleeve, a plurality of tubular fluid-cooled conductors, insulation means for supporting said tubular fluid-cooled conductors in said end plate and inside of said metallic sleeve, a cathode structure including a plurality of parallel rods positioned longitudinally of and internal to said grid electrode, and means for connecting said cathode structure to said fluidcooled conductors, whereby said cathode structure is supported in spaced relation with said grid electrode.

5. A high power fluid-cooled vacuum tube comprising a tubular anode, a pair of ring-shaped plate members attached one to each end of said tubular anode, a substantially tubular member surrounding said tubular anode and slightly displaced therefrom, said tubular member having means for sealing the ends thereof to said ringshaped members to form a water-tight jacket around said tubular anode, plumbing connections provided to said water-tight jacket for circulating cooling medium through said jacket around said anode, a grid electrode positioned inside of said anode and coaxially disposed with respect to said anode, said grid electrode comprising a wire spiral supported upon a plurality of parallel spaced rod-like members, a substantially circular metallic spacer member having tongues around the periphery thereof with a pair of aligned apertures in each tongue for engaging the ends of said rod-like members, and tapered pins engaging said rods and tongues for securing said rods to said tongues, a perforated annular member for receiving the other set of ends of said rod-like members in the perforations thereof, a metallic sleeve attached to said annular member, a hollow electrical insulator sealed to one of said ring- ,shaped plate members and surrounding said metallic sleeve, a metallic end plate attached to the other end of said hollow insulator and to the other end of said metallic sleeve, a plurality of tubular fluid-cooled conductors, insulation means forsupporting said hollow fluid-cooled conductors in said end plate and inside of said metallic sleeve, a plurality of cathode rods positioned longitudinally of said grid electrode, and means for connecting said plurality of cathode rods to said fluid-cooled conductors, whereby said cathode is suspended by said conductor.

' 6. A high power vacuum tube as defined in claim 2 further characterized by said cathode structure comprising three substantially circular metallic plates, each of said plates having three peripheral projections thereon spaced approximately equally about the periphery thereof, said plates each having a pair of substantially equalsized holes cut therethrough and a third smaller hole, insulation spacing means positioned in said substantially equal-sized holes, said insulation spacing means having flanges thereon for spacing .said metallic plates, three tubular fluid-cooled electrical conductors, different ones of said tubular conductors being attached to different ones of said metallic plates in said smaller apertures, said insulation spacing means having apertures corresponding to said smaller apertures for receiving selected ones of said tubular conductors, strip-like members attached to said projections, and electron emissive filament members adapted to be heated to electron emission temperature attached to said strip-like members.

7. Grid electrode structure for a high power vacuum tube comprising a plurality of substantially parallel rod-like members, each of said rodlike members having a kink formed therein in one end thereof, said rod-like members being disposed in parallel spaced relation about a circle, a cuplike member having apertures formed in surfaces thereof for receiving the kinked portions at one of the ends of said rod-like members, a plurality of tapered pins, said tapered pins being adapted to engage the kinked portions of said rod-like members and surfaces of said cup-like member to retain said rod-like members and said cup-like member in assembled relation, an apertured annular member having a groove formed around the outside thereof, said groove exposing intermediate portions of the apertures of said apertured annular member and said apertures being of a size adapted to receive the other ends of said rodlike members, and a binding member adapted to be positioned in said groove to engage surfaces of said rod-like members and binding said rod-like members against surfaces of said apertures.

8. Grid electrode structure for a high power vacuum tube comprising a plurality of substantially parallel rod-like members, each of said rodlike members having a kink formed in one of the ends thereof, said rod-like members being disposed in parallel spaced relation about a circle, a cup-like member having apertures formed in surfaces thereof for receiving the kinked portions of said rod-like members, and a plurality of tapered pins, said tapered pins being adapted to engage the kinked portions of said rod-like members and surfaces of said cup-like member to retain said rod-like members and said cup-like member in assembled relation.

9. A high power fluid-cooled vacuum tube comprising a tubular anode, a grid electrode and a cathode, an annular member attached to one end of said tubular anode, a metallic sleeve having one end attached to one end of said grid electrode, a disc-like plate attached'to the other end of said metallic sleeve, a hollow electrical insulator for spacing said annular member from said disc-like plate, said hollow electrical insulator having flared ends, clamping means for engaging and clamping the flared ends of said insulator to said annular member and to said disc-like plate, said disc-like plate having a substantially centrally disposed hole formed therein, an insulator positioned in said hole, and a plurality of tubular conductors connected to said cathode and passing through said last-mentioned insulator, in fixed relation thereto, whereby said cathode is suspended Within said grid electrode. I

10. In a high power fluid-cooled vacuum tube, a cathode, a grid electrode and an anode, means for insulating said cathode, said grid electrode and said anode from each other, tubular means connected to said cathode for feeding current thereto, means for sealing the ends of said tubular means connected to said cathode in fluid-tight relation, auxiliary tubular means positioned inside of said tubular conductors for feeding cooling medium into said tubular conductors adjacent to said cathode, said tubular conductors and said auxiliary tubular members having spaces therebetween for passing the aforesaid cooling medium, electrical connectors engaging said tubular conductors in clamping relation, and plumbing connections fitted to said tubular conductors and said auxiliary tubular members for feeding the aforesaid cooling medium therethrough.

11. In a high power fluid-cooled vacuum tube, a cathode, a grid electrode and an anode, means for insulating said cathode, said grid electrode and said anode from each other, a water jacket around said anode, plumbing connections for connecting a supply of cooling medium to said water jacket, tubular means for feeding current to said cathode, means for sealing the ends of said tubular means connected to said cathode in fluid-tight relation, auxiliary tubular means positioned inside of said tubular conductors for feeding cooling medium into said tubular conductors adjacent to said cathode, said tubular conductors and said auxiliary tubular members having spaces therebetween for passing the aforesaid cooling medium, electrical connectors engaging said tubular conductors in clamping relation, and additional plumbing connections fitted to said tubular conductors and said auxiliary tubular members for feeding the aforesaid cooling medium therethrough.

12. A high power fluid-cooled vacuum tube comprising a tubular anode, a grid electrode and a cathode, an annular member attached to one end of said tubular anode, a metallic sleeve having an end attached to one end of said grid electrode, a disc-like plate attached to the other end of said metallic sleeve, a hollow electrical insulator surrounding at least a part of said metallic sleeve for spacing said annular member and said disc-like plate, said hollow electrical insulator having flared ends, clamping means for engaging and clamping the flared ends of said insulator to.

said annular member and to said disc-like plate, said disc-like plate having a substantially centrally disposed hole formed therein, an insulator positioned in said hole, a plurality of tubular conductors connected to said cathode and to said last-mentioned insulator, and passing through said last-mentioned insulator, and said metallic sleeve, whereby said cathode is suspended within said grid electrode.

13. A high power fluid-cooled vacuum tube comprising a tubular anode, a grid electrode, a cathode, an annular member attached to one end of said tubular anode, a metallic sleeve having one end attached to one end of said grid electrode, a disc-like plate attached to the other end of said metallic sleeve, a hollow electrical insulator for spacing said annular member from said disc-like plate, said hollow electrical insulator having flared ends, clamping means for engaging said insulator and clamping the flared ends thereof to said annular member and to said disc-like plate, an insulator positioned in a hole in said disc-like plate and conductors passing through said last insulator for feeding current to said cathode.

STEPHEN M. DUKE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,669,145 Prindle May 8, 1928 1,957,223 Murphy May 1, 1934 2,009,444 Gebhard July 30, 1935 2,012,038 Eitel et al Aug. 20, 1935 2,169,879 McArthur et al. Aug. 15, 1939 2,288,380 Wing, Jr June 30, 1942 2,298,950 Litton Oct. 13, 1942 2,323,364 Wing, Jr July 6, 1943 2,380,502 Clark et a1 July 31, 1945 2,492,313 Okress Dec. 27, 1949

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Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2909698 *Sep 19, 1955Oct 20, 1959Rca CorpElectron tube
US4197481 *May 16, 1978Apr 8, 1980International Standard Electric CorporationMagnetically focussed tube
US4563609 *Aug 18, 1983Jan 7, 1986Thomson-CsfDirectly-heated cathodes
US5236159 *Dec 30, 1991Aug 17, 1993Energy Sciences Inc.Filament clip support
EP2557902A2Aug 6, 2007Feb 13, 2013Plasma Surgical Investments LimitedCathode assembly and method for pulsed plasma generation
Classifications
U.S. Classification313/21, 313/35, 313/42, 313/333, 313/265, 313/32, 313/343, 313/237, 313/22, 313/273, 313/350
International ClassificationH01J19/34
Cooperative ClassificationH01J2893/0003, H01J19/34
European ClassificationH01J19/34