US3084274A

US3084274A - Electron tube

Info

Publication number: US3084274A
Application number: US859462A
Authority: US
Inventors: Roger A Krey
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1959-12-14
Filing date: 1959-12-14
Publication date: 1963-04-02
Anticipated expiration: 1980-04-02

Description

R. A. KREY ELECTRON TUBE April 2, 1963 Filed D c. 14, 1959 INVENTOR. R m :3 ER A. KREY BY Wlflw J a a o o o o o o o 0 0 0 0 0 u/ H/ u I ATTMWEX Patented Apr. 2, 1953 3,59%,274 ELECTRQN TUBE Roger A. Krey, Summit, NJ, assignor to Radio Corporation of America, a corporation of Delaware Filed Dec. 14, 1959, Ser. No. 359,462 6 Claims. (Ci. 3i3247) This invention relates to improvements in electron discharge tubes of the type which utilize envelopes having metal and ceramic walls and incorporated socket indexing features, and which may also incorporate interelectrode shielding in rnultigrid tubes.

In one form of prior art device of the multigrid variety, the cathode, control and screen grids are supported on a ceramic header member or wafer, the periphery of which is metalized and sealed vacuum tight to one end of a cylindrical ceramic portion of the envelope which surrounds the cathode and grids. in this type of tube the anode is supported from the other end of the cylndrical ceramic portion of the envelope, the anode and its supporting member being sealed with a vacuum tight fit to close the end of the envelope opposite the header member.

Each of the electrodes, except the anode, is mounted on a support flange, the flanges being progressively larger in diameter from the cathode support flange to the screen grid support flange. These flanges are in turn supported by lead-in and support wires sealed in the ceramic header. The screen grid flange extends closely adjacent the Wall of the ceramic portion of the envelope, the inner wall of which is metaiized upwardly from the header to the lower end of the anode. The anode is coaxial with the other electrodes and is supported within the cylindrical ceramic portion of the envelope. The base has attached to it a ring having indexing lugs thereon to properly orient a tube with its socket.

Several dih'iculties are encountered in making an electron discharge device of this kind. Since the electrodes supported on the header member are enclosed within the cylindrical ceramic portion of the envelope, one end or" which is sealed to the header prior to the sealing of the anode and its support to the other end of the envelope, it is not possible to inspect the electrode mount assembly on the header prior to the last steps of bake out and sealing in the anode. Metslizing the interior of the ceramic cylindrical por ion is not only ditlicult to control but is expensive. The prior construction also presents certain difficulties of bake out of and exhausting of the tube since gases must escape between the anode and its upport, or between the closure member which is secured to the anode and the closure member support, the bake out and exhaust being the last step before sealing the envelope. in prior art constructions the indexing lugs mounted on a ring were attached to the header member after sealing to provide means for indexing the tube into a socket.

it is an object or" this invention to provide a novel ceramic and metal envelope structure for a tube of the type described in which one metal part of the envelope serves to provide shielding between electrodes and provide indexing means to facilitate socks-ting of the tube, thus eliminating the need for later attaching the indexing lugs.

It is also an object or this invention to provide such envelope structure which, although closed at one end thereof by an anode and its support, nevertheless lends itself to a fabrication process in which the envelope structure with the anode sealed thereto can be placed over an otherwise completed electrode and header assembly, and the completed tube assembly then subjected to an evacuation step, and then sealed to form a completed tube.

A still further object of my invention is to provide an electron discharge device of the type described having a novel ceramic and metal envelope which permits inspection of the electrode mount assembly prior to inserting the header and assembly into the envelope to be sealed therein.

A further object of my invention is to provide a ceramic and metal envelope for an electron discharge device or the kind described and which eliminates the necessity of metalizing the ceramic portion of the envelope to provide shielding means cooperating with the screen grid.

An elect on discharge tube utilizing my invention includes an insulating header wafer preferably ceramic having a plurality of support and lead-in conductors sealed therethrough. A plurality of cylindrical, coaxial electrodes including a cathode and a plurality of grids are mounted on the conductors by means of radially ex tending flanges.

In accordance with my invention the envelope is provided with an annular ceramic portion having fiat surfaces lying in parallel planes transverse to its longitudinal axis. Sealed to one end of the annular ceramic portion is a tubular metal portion of the envelope which terminates at its free end with a pair of locating lugs oi arcuate shape one being of greater width than the other. The tubular metal portion forming the base portion of the envelope is provided between the lug end and the end sealed to the ceramic portion with inwardly directed positioning elements for positioning and supporting a header member carrying the electrodes and their supports during bakeout and sealing operations. The envelope has sealed to it at the other end of the ceramic annular portion an inverted cup-shaped member which in turn supports a tubular anode extending within the ceramic annular portion, the free end of the anode registering with the junction of the annular ceramic portion and metallic tubular portion. This envelope with the anode support and anode is fabricated first, prior to receiving the header and mount assembly and the bakeout and sealing of the completed tube assembly. The various electrodes including the cathode, control grid, and screen grid are supported by flanges upon conductors sealed through the header member. The flange of the screen grid extends closely adjacent the metallic tubular portion of the envelope. With this construction, it is possible to perform the bakeout and sealing operations by first inserting into the inverted envelope the ceramic wafer, header member and the electrodes supported thereon to be received and supported on the positioning elements. A sealing ring is then dropped into position within the tubular member in contact with the header. The envelope and the tube are then baked out and evacuated in an evacuation chamber. The temperature is then raised to melt the sealing ring to seal the header at its periphery to the tubular metallic portion of the envelope. This construction avoids the difficulties pointed out above and facilitates assembly of the tube.

In the drawings:

FIG. 1 is a longitudinal section view of an electron tube according to my invention; and

HG. 2 is a section view taken along line 22 of FIG. 1.

Referring to the drawings an electron tube 10 utilizing my invention includes a ceramic disk header wafer 12 having a plurality of bores 14 thereth-rough. A plurality of electrode support and lead-in conductors 16 are sealed in vacuum-tight relation in the bores 14.

As shown in FIG. 2, the bores 14 are arrayed in four

concentric circles

18, 20, 22, and 24 shown in dotted line. Three bores are disposed in equidistant rela tion on each of the circles. The bores in adjacent circles areangularly displaced 60 to provide maximum spacing therebetween.

The electrode mount assembly comprises in coaxial array, a cylindrical outer or screen grid 27, an inner or control grid 28, and a cathode electrode 30. An anode electrode 31 is disposed concentrically about the other electrodes. The outer grid 27 is mounted on a radially extending flange 32 which is in turn mounted on three of the conductors 16 which extend into bores on the circle 24. The inner lg-rid electrode 28 is similarly mounted on a radially extending flange 34 which is in turn mounted on three of the conductors 16 which extend into bores on the circle 22. The cathode 30 is mounted on a radially extending flange 38 which is supported on three of the conductors 16 extending into the three bores on the circle 20. A coil heater 4-4 is dis-posed in the cathode 30 and connects to a pair of the conductors 16 which are sealed through two bores on the circle 18.

An envelope made according to my invention includes the annular ceramic portion 46 having end surfaces lying in spaced parallel planes normal to the longitudinal axis of the envelope. The base portion of the envelope includes a conducting tubular member 48 of metal having an upper axial end '50 sealed to one of the end surfaces of the annular ceramic member 46 and extending away therefrom. The tubular member 43 is provided with means for supporting the ceramic header member 12 during assembly and terminates in a pair of oppositely disposed arcuate indexing lugs '52 and 54 of different :arcuate widths. The other end of the envelope includes an inverted cup-shaped member 56 of conducting material having a lip 58 at its open end sealed to the annular ceramic member '46. The cup-shaped member 56 in turn provides the support for the anode 31 which has a portion thereof received within and secured to the inner wall of the cup-shaped member '56 which in turn provides the anode terminal. Thus, the assembly of the anode 3,1 and the cup member 56 constitutes an anode and envelope enclosure structure or assembly. The three-part envelope and anode are assembled as a unit prior to receiving the mount assembly therein.

The tubular member 48 is provided with an integral tapered shoulder 60 having a plurality of inwardly directed indentations as projections 62 on which the header wafer is seated during exhaust and bake out. The indentations are localized portions of the tapered shoulder 60 which have been formed by flattening the tapered shoulder into a horizontal plane as indicated on the right side of the member 48 in FIG. 1. The projections 62 provide a uniform support for maintaining the ceramic header 12 in a horizontal position during the bake out, exhaust,

and sealing operations of the tube. This last-described construction provides adequate spacing between the periphery of the header 12 and the inner face of the walls of the tubular metal member 48 so that the tube can be easily exhausted during 'bake out in a vacuum furnace. In the completed tube a hard solder seal is made between the periphery of the header wafer 12 and the tubular section 50 and the flange 32 shield the anode 31 from the cathode 30 and control grid 28. The indexing

lugs

52 and 54 are formed as circumferential sections of the tubular member48 and are thus integral therewith. The

indexing lugs 52 and 54 are disposed substantially opposite each other --and are of difierent circumferential extent such that'the tube can be received in an accommodating socket in only one angular orientation relative thereto.

The end of the envelope opposite the header is closed by an inverted cup-shapedmember 56 sealed to the upper end surface of the annular ceramic envelope portion 46. The anode 31 is provided with an extension 64 received within the cup-shaped member 56. This extension is fixed by press fit within the closure member 56. The anode 31 extends axially toward the header Wafer 12, the lower end of the anode registering with the upper end 50 of the tubular metal member 48. Thus, in the embodiment shown, the adjacent ends of the anode 31 and the tubular metal member 48 terminate in approximately the same transverse plane. The member 56, in addition to being a closure member and anode support, serves as the anode terminal.

In the fabrication of the electron tube 10, a metallic coating, such as molybdenum, is applied to the ceramic disk header 12 on its outer periphery and on the Walls of the bores .14. Such a coating may be applied by any suitable known metalizing process.

In operation of an electron tube of the type illustrated, strong electric fields are created between the anode and other of the tube electrodes. If such electric fields are not adequately shielded from the control grid, i.e., the inner grid 28, operation of the tube is adversely eflected.

Shielding between the anode 31 and the control grid 28 is provided according to my invention by co-operation of the outer grid support flange 32 and the upper section 50 of the base portion of the envelope, that is, tubular metal member 48. Since the outer grid support flange 32. extends radially outward with its periphery in close proximity with the tubular metal member 48, and since the upper portion 50 of the tubular metal member 48 is madeto extend upwardly beyond the periphery of the flange 32, the control grid and cathode structures including their flanges 34 and 38 and their supporting conductors 16 are substantially completely shielded from the anode. This avoids the necessity of coating the inner wall of a ceramic annular portion of the envelope.

"in addition to providing this shielding, the tubular metal member 48 serves the additional function of providing the indexing lugs 52 and 54. This eliminates the need for an additional indexing means to be attached after assembly of the entire tube.

It will thus be appreciated that by virtue of my novel envelope structure, a single integral metal member 48 serves not only as a part of the vacuum enclosure but also as a shield member, an indexing socketing member, and a support for the anode 31 of the tube. In addition to these multiple functions provided by the tubular metal member 48, an envelope structure results which is adapted to simple tube fabrication processing in which a preassembled electrode and stem structure can be easily integrated therewith.

What is claimed is:

1. An electron tube comprising an insulator header wafer, a plurality of conductors sealed through said header, an electrode spaced from said header and supported by said conductors, and an envelope enclosing said electrode and including a tubular metal member, a tubular insulator, and a cup-shaped anode and envelope enclosure structure sealed together end-to-end in an axial disposition in the order named, said anode and envelope enclosure structure including a tubular portion axially extending concentrically within said tubular insulator to adjacent said tubular metal member, said tubular metal member surrounding said header and sealed thereto with said header axially spaced from said tubulm insulator.

2. An electron tube comprising coaxial cathode, control grid, screen grid, and anode electrodes, a disk header, a plurality of conductors sealed through said header, said cathode, control grid, and screen grid electrodes being supported by said conductors, and an envelope, said envelope including a tubular metal member sealed around said disk header and extending therefrom to adjacent said anode and having a pair of integral mutually spaced arcuate lugs formed as circumferential sections of said tubular metal member at the and opposite said anode, an annular insulator sealed to said tubular metal member adjacent said anode, and a cap member sealed to said annular insulator and closing the end of said envelope, said anode being mounted within and supported by said cap member.

3. An electron tube comprising an insulating header water, a plurality of parallel conductors sealed vacuumtight through said header Wafer, an electrode supported by said conductors on one side of said header, an envelope sealed to said header and together with said header enclosing said electrode, said envelope including a onepiece tubular metal member surrounding said header and sealed thereto and extending therefrom on said one side of said header to adjacent said electrode and having a pair of mutually spaced circumferential indexing sections of different circumferential extent extending perpendicular from said header on the other side thereof, a tubular insulator sealed at one end thereof to the end of said onepiece tubular metal member in tandem relation therewith,

and an anode and envelope enclosure structure sealed tothe other end of said tubular insulator and surrounding at least a portion of said electrode and forming an end enclosure of said envelope.

4. An electron tube comprising an insulator header wafer; a plurality of conductors sealed through said header; coaxial cylindrical cathode, inner grid, outer grid, and anode electrodes disposed axially perpendicular to and spaced from said header; said anode electrode surrounding at least portions of other of said electrodes; said other of said electrodes being supported by said conductors; an annular flange member secured to the end of said outer grid electrode adjacent said header and extending radially outward therefrom; and an envelope structure including a tubular metal member, an annular insulator member and a cup-shaped envelope enclosure member disposed axially perpendicular to said header; said tubular member surrounding said header and sealed thereto and extending axially on one side of said header to beyond said radial flange and having a pair of spaced lugs of arcuate cross section extending axially on the other side of said header, said lugs comprising circumferential integral sections of said tubular member, said annular insulator being sealed to said tubular member beyond said radial flange from said header and to said envelope enclosure member, said anode electrode being supported by and at least partially within said envelope enclosure member.

5. An electron discharge device having an envelope comprising an annular ceramic portion having end surfaces lying in spaced parallel planes, a tubular conducting member having an end sealed to one of said end surfaces, the other end of said conducting member having oppositely disposed indexing lugs integral therewith and extending therefrom, an anode and closure member assembly sealed to the other of said end surfaces on said ceramic portion, and a ceramic closure member received Within said tubular conducting member and sealed at its periphery thereto, and electrodes mounted on said ceramic closure member, said anode extending Within the envelope and surrounding the other electrodes supported on said ceramic closure member.

6. An electron discharge device having an envelope comprising an annular ceramic portion having end surfaces lying in spaced parallel planes, a tubular conducting member having an end sealed to one of said end surfaces, the other end of said conducting member having spaced oppositely disposed indexing lugs integral therewith and extending therefrom, an anode and closure member assembly sealed to the other of said end surfaces on said ceramic portion, and a ceramic closure member received within said tubular conducting member and sealed at its periphery thereto, said anode and closure member including an anode portion extending Within the envelope, said device also comprising at least one electrode supported on said ceramic closure member and extending within said anode.

References Cited in the file of this patent UNITED STATES PATENTS 2,880,349 Polese Mar. 31, 1959 2,885,588 Wilde May 5, 1959 2,918,598 Rose et a1 Dec. 22, 1959 2,937,305 De Backer May 17, 1960 2,995,673 Schade Aug. 8, 1961

Claims

1. AN ELECTRON TUBE COMPRISING AN INSULATOR HEADER WAFER, A PLURALITY OF CONDUCTORS SEALED THROUGH SAID HEADER, AN ELECTRODE SPACED FROM SAID HEADER AND SUPPORTED BY SAID CONDUCTORS, AND AN ENVELOPE ENCLOSING SAID ELECTRODE AND INCLUDING A TUBULAR METAL MEMBER, A TUBULAR INSULATOR, AND A CUP-SHAPED ANODE AND ENVELOPE ENCLOSURE STRUCTURE SEALED TOGETHER END-TO-END IN AN AXIAL DISPOSITION IN THE ORDER NAMED, SAID ANODE AND ENVELOPE ENCLOSURE STRUCTURE INCLUDING A TUBULAR PORTION AXIALLY EX-