US2422945A - Apparatus for manufacturing electron discharge devices - Google Patents

Description

June 24, 1947.

MECHANISM w. s. BRIAN ,945

APPARATUS FOR MANUFACTURING ELECTRON DISCHARGE DEVICES F'g led Nov. 23, 1944 3 Sheets-Sheet INVENTOR.

June 24, 1947.

APPARATUS FOR MANUFACTURING ELECTRON DISCHARGE DEVICES 3 Sheets-Sheet 2 Filed Nov. 23, 1944 INVENTO R. ZZ/LZZMU); 5157mm w. s. BRIAN 2,422,945

June 24, 1947. M BRMN] 2,422,945

APPARATUS FOR MANUFACTURING ELECTRON DISCHARGE DEVICES Filed Nov. 23, 1944 5 Sheets-Sheet s r0 2 I COOLING J v HIGH FREQUENCY sour ca CmwvEcLr/o/v r0 Ex Imus r Pun P.

therefor.

Patented June 24 1947 a a "2,42z,945] a APPARATUS FOR MANUFACTURINGELEC- a TRONDISCHARGE pnyrcns William s. Brian, owensboi-al xygimigntntyfl .mesne assignments, to General Electrle Joinpanyia c'orporation of New Xork e u M e Application November 23, 1944',Serla'l No. 564,768. (cine- 9) Claims Thisinvention relates to a method of and apparatus for manufacturing electron discharge 1 devices such as vacuum tubes and more particularly to such amethod and apparatus by means of which the exhaustgbaking-out anddegasing of a vacuum tubeare conducted within an exhaustible container in thetnature of a belljarv and the used an exhausting and sealing tubulation is i avoided. While the inventionis of general application in the manufacture of electronfdischarge devices, it is particularly suitable {or use in themanufacture of devices of the type disclosed and claimed; in my copending application Serial No. 557,126; filed October 4, 19 44, and. entitled Electron dischargedevice and electrode assembly In the manufacture of, conventional tubes, it is customary tomount the various tube electrodes on a: supporting sealing stem or press through which the .lead in conductors pass, This assembly* is then enclosed within'and sealedto an envelope other tube elements is enacted substantiallyicompletely automatically, thereby involving a minimum number of manual operations, a

;Itis. another object of the invention to provide a new and improvedmethod of and apparatus for, manufacturing electron discharge devices in which the exhaust, baking-out and degasing are conducted withinan exhaustible container and Y ,withoutthe use of an exhausting and sealing tubulation.

Inaccordance with thednven tion, the method v of manufacturing an electron discharge device including a unitary electrode assembly comprises a supporting, an electrode assembly from a sealing stem having an annuluar sealing surface, sub jecting the electrode assembly and stemsimultaneously to exhausting andheating media to a ,degas thesame, and sealing at least one enclosing provided withan exhausting and sealing tubula ,tion and usually having a configuration cooperat ing with mica spacing washersto locate the. electrode structure accurately and rigidly within the envelope. The exhausting tubulation is generally connected to an exhausting manifold andjwhile so connectedthe deviceis passed through a bakshell to the stem whilethe assemblyis" subjected L to theexhausting andheatingmedia. Further in accordance with the invention, appatratus ior manufacturing electron discharge devicesof the type including a unitary electrode ing-out oven for degasing, whereupon the tubula tion is sealed, oil and severed from the exhaust conducted continuously by means of automatic machinery.

.The process described has a number of limitations which it is desirable toavoid; Forexample, the exhaust is eifected through a restricted tubulation which considerably limits the rated exhaust, resulting either in an extended exhaust period or a lower degree of vacuum thanisdesired. Furthermore, the exhaust tubulation, which is tipped oflor sealedafter the exhaust operation, constitutes a weak point in the physical structure of the tube and must be protected from breakage in someway, either bya mounting base or some form of guard.

It has-also beenproposed heretofore toexhaust V and bake out vacuum tubes within an exhausted container, such as a bell jar, but the typesfoi devices to which such a process has heretofore been applied have beensuchthat the process has proved impracticable. a a a It is a general objectof theinvention, theremamfbldy e process just described is r assemblmta sealing stern I and at least one enclosing shell comprises an exhaustiblej container in- -cludinga removable cover portion, means within the container, for supporting the electrode as-- sembly and stem, andrneans within the container for supporting the shellin spaced relationto the sealing stem. ,The apparatus also includes means forj subjecting the assembly. stem and shell to an exhaustingand heating media. and means external to the container ,tor initiating relative movementbetween the, two supporting means to .bringthe shell into sealingengagement with the stern while subject tonic exhausting and heating a media.

For a better understanding, of the invention, together. ,with other andfurther objects thereof, reference is had to the following descriptiontalren ,in connection with the accompanying drawings while its scope will be pointed out in the appended claims.

.m the drawings/Figs. 1a,.1b and 1c represent a cathode in successive stages ofassembly; Fig.

2a is an elevational view illustrating schematically apparatus for manutacturinggrid electrodes, F18. 2b is a plan, view'showlng the material from a, which the grid electrodes are manufactured as it 1 an elevatioriaiand plan ,view oi the ;completed i grid electrode; Fig.'3a illustrates schematically fore, to provide p. new and lmprovedmethodof and apparatus for manufacturing electron" discharge deviceswhich avoid one or moreflof the above-named disadvantages and limitationsoi i the systems of the prior art.

It is another object 01' the invention to provide a new and improvedmethod of and apparatus for manutacturing electron discharge devices in which the assembly of the electrodes and appears ,aftereach operation, and Fig. 2c shows the successive, steps of assembling the unitary electrode assembly and E18. 3b is an elevational view of aamachine for dispensing theelements in succession in accordance with the steps illustrated -in Fig. 30; Fig. 4 is a perspective view of. a unitary electrode assembly mounted in its supporting sealing stem; while Fig. 5als an elevational view, partly in section, of an apparatus for practicing the method or the invention incxhaustlng, bakstep advance.

ing-out and degasing the electron discharge device,Fig. b isa cross-sectional detail showing the positional relation of the components of'the electron discharge device in the apparatus of Fig. 5a during treatment, and Fig. 5c is a perspective view of one of the supportsshown in Fig. 5a..

Referring now to Figs. 1a, lb'andlci there is illustrated the method 5 assembling the cathode element of an e1 ctro discharge device .-to be manufactured in cog glance with the invention. In these figures, a p ir. of opposed annular cuplike elements Illa and Hlb'are assembled with a triangular frame or yoke ll therebetween which is bonded to both of the elements Illa and" Nb,

tube, the resulting cathode is preferably in accordance with the design illustrated in my abovementioned copending application.

In Figs.'2aand 2b there is illustrated the method, in accordancewith the invention, of manufacturing grid electrodes for embodiment in the electron discharge device constructed in accordance with the method of the invention. The method represented in Figs. 2a and 2b comprises intermittently feeding a continuous metallic sheet or ribbon 15 to a plurality of-successive operating stations A, B, C and D. The metal ribbon I5 may be supplied from a' suitable feed roll or spool I6 and is passed over, one or more guide rolls l1, past the stations A-D, inelusive, and to an indexing mechanism I! which imparts to the ribbon IS an intermittent step-by- At station A there is provided a punch or die for punching in the ribbon l5 spaced apertures [5a, preferably-of circular configuration. Between the'stations' A and B there is fed a superimposed continuous ribbon I! of metallic grid, this ribbon being fed'intermittently and synchronously with the ribbon l5. The term grid is used in its generic sense to include a group of parallel wires, a mesh or screen or a perforated sheet. The ribbon l9 maybe supplied from a feed roller or spool 20 and passed over one or more guide rollers or spools 2| and through the indexing mechanism l8. Station B comprises ;a punch or die for deforming the grid I9 within 'eachaperture into a dish-like configuration l9a having a plane bottom parallel to the plane of the ribbons l5 and 19. Station C includes provisions for line welding or otherwise bonding the grid ribbon l9 ,to the apertured ribbon I5 about the periphery of each aperture; that is, station C may comprise a suitable electric 'resistance welder. At station D there is provided a die or punch for punching from the superimposed ribbons l5 and IS a series of composite disks, each of a diameter larger than the apertures in the ribbon l5, the resulting apertures in the superimposed ribbons being represented at l5b. A detail of resulting composite disk is shown in Fig. 2c, in both plan and cross section, from which it is seen that the dish-like grid portions l9a are surrounded by an annular frame or flange l9b to which the peripheral portion of the grid or mesh Illa is welded, thus providing an accurately formed, rigid grid electrode.

In order to ensure synchronism between the several operations performed at stations A, B, C and D, there is provided a common driving mechanism 22 which, by means of a shaft 23, actuates the forming mechanism at each of the stations, as represented schematically by the several crank and link mechanisms 23a, 23b, 23c and 23d, and which also actuates the indexing mechanism It to advance the superimposed ribbons l5 and IS an appropriate distance between each successive operation. It will be understood that the details of the mechanism for practicing the method described form no part of the'present invention but that such a mechanism may be of any conventional type. The method of forming electrodes described above is claimed in my divisional application, Serial No. 610,794, filed August 14, 1945.

Referring now to Figs. 3a and 3b, there is represented schematically apparatus by means of which there may be practiced the method of assembling the several electrodes of the electron discharge device being manufactured in their desired relationship within a retaining shell of insulation material to form a unitary electrode assembly. Referring particularly to Fig. 3b there is represented a cir ular stationary head 25 including a plurality of loading magazines 25a for carrying groups of individual electrode elements or parts and provided with suitable dispensers for dispensing suchelements singly. The stationary head 2513 supported on a base or table 28 but spaced therefrom. Between the head 25 and the table 26 is disposed a rotatable table or drum 21 carrying a plurality of loading heads 21a. The rotatable table 21 is provided with indexing mechanism, not shown, so that each of the loading heads 21a stops successively under each of the magazines 25a to receive the several electrode elements or parts in their proper sequence. The loading heads 21a, after each indexing movement, are raised by a suitable cam mechanism, not shown, under one of the magazines 25a to trip the dispensing mechanism associated therewith and receive a part. The magazine 25b represents schematically the unloading receptacle or magazine from which the complete electrode assembly is removed.

The several electrode elements and parts going to make up a unitary electrode assembly of the type disclosed and claimed in my above-mentioned copending application are represented in Fig. 3a opposite their respective positions in the stationary head 25 from which they are dispensed. In the specific assembly represented, the elements are, in their order of assembly, an anode 28; a ceramic retainer shell 29; a ceramic spacer rin 30; a grid electrode 3| of the type resultin from the method described above in connection with Figs. 2a, 2b and 2c, and in this case functioning as a supressor grid; a second ceramic spacer ring 30; a second grid 32 which may be of a different design and proportioning than the grid 3| and in this case functioning as a screen grid; a ceramic spacer ring 30; a third grid 33 which in this case is a control grid; a ceramic spacer ring 30; a cathode assembly 34, which may be of the type resulting from the method described in connection with Figs. 1a, 1b and 10; a second ceramic retainer shell 29; a ceramic spacer ring 30; a fourth grid 35, in this instance a control grid; 9. ceramic spacer ring 30; a fifth grid 36, in this instance a screen grid;a ceramic spacer ring 30; a sixth grid 31, in this case a suppressor grid; a ceramic ring 30; and a second anode 28, the complete electrode assembly being as represented by the unit 38 opposite the unloading position of the magazine head 25.

The unitary electrode assembly fabricated as just described is thereupon supported from a sealing stem having an annular sealing surface and preferably, as shown in Fig. 4, comprising an annular ring 39 surrounding the electrode assembly 38 and provided with opposed upper and lowertuting the sole support of the electrode assembly 38 within the annular sealing stem 39. Others of the lead-in conductors 39b may be connected to the other electrodes of the assembly in a coni ventional manner, certain of these connections being'illustrated. After the parts are positioned as illustrated, the annular ring 38 is subjected to ,heat and pressure in a forming diewhich fuses the glass ring 89 sufllciently to close the slots 39a and seal the ring 39 about the lead-in conductors 391), thus providing a unitary rigid structure composed of the electrode assembly 38 and its surrounding annular sealing stem 39.

The apparatus for completing the manufacture of electron discharge devices of the type described, including a unitary electrode assembly, a surrounding sealing stem, and at least one enclosing shell, .-preferably two opposed enclosing shells, is represented in Fig. a. This apparatus comprises an exhaustible container 48, preferably of non-conductive material such as the glass commercially available as Corning type 705. The container 48 is sealed to a metal mounting ring 4|, preferably of a cobalt, nickel and iron alloy commercially available under the trade name Kovar," having atemperature-coeiiicientof-expansion substantially matching that of the glass container 48. The ring 4| is provided with an internal supporting disk 42 having a plurality of enlarged apertures 42a opening into the bottom of the ring 4| which is .adapted for connection to a suitable exhaust pump or manifold through valves,- not shown. The container 48 is provided with an outwardly extending peripheral flange 48a in which is seated a removable cover portion 48b, preferably also of glass, which is adapted to sit in the annular flange 4811 on a seal or cushion 43 of rubber or equivalent sealing material. It is foundthat normally the atmospheric pressure acting on the cover por tion b is suiiicient to maintain an air-tight seal at the flange 40a.

There are provided means for supper-ting within the exhaustible container 48 the electrode assembly and steam structure, as well as means for supporting two enclosing shells for the electrode assembly in spaced relation to the stem and on opposite sides thereof. The desired space relationship of the components is represented in Fig. 5b in which the electrode assembly 39 and annular sealing stem 39 are shown with upper and lower substantially hemispherical enclosing shells 44 and 45 spaced from the opposing sealing surfaces of the sealing stem 39. Specifically,

the supporting means for the electrode assembly 38, the stem 39 and shells 44 and 45 comprises a central supporting post 46 mounted from the disk 42 and extending vertically with- 5 in the chamber 40. A stationary ceramic ring or jig 41 is supported from an auxiliary ceramic platform 48, rigidly secured to the post 45, by means of posts or struts 49 provided with threaded portions 49a cooperating with nuts 58 for accurately positioning vertically the jig 41 which, in turn, positions and supports the electrode assembly 38 and sealing stem 39. There is also provided a ceramic supporting ring or jig 5| for the upper shell 44, theiig 5| being supported by posts or struts 53 from a ceramic platform 53 in turn supported on a sleeve 54 slidably mounted on the post 48. The jig 5| merely rests on its supports so that it can be lifted off when the tube lscompleted. There is also provided a third ceramic jig or ring 55 for supporting the lower sealing shell 45, the jig 55 being supported from a sleeve 58 sliding on post 45 and on which, in turn, the sleeve of jig 5| slides.

The apparatus of Fig. also includes means for biasing the jigs 5| and to bring the shells 44 and 45 into sealing engagement with the stem 39. The biasing means of the upper jig 5| comprises merely the weight of the jig and its associated elements which tend to drop, bringing the lower rim of the shell 44 into sealing engagement with the upper face of the stem 38. The biasing means for the jig 55 comprises a coil spring 51- actingon a flange 58a of sleeve 58, biasing the jig 55 to move the lower enclosing shell 45 upwardly until its upper rim engages the lower sealing surface of the stem 39.

The apparatus of Fig. 5a. also includes latching means for normally restraining the supportingmeans of the several vacuum tube elements from stem engaging movement. Specifically, latching means comprises a pin 58 supported by pivoted link mechanism 59 for horizontalmovementto engage overlapping slots in the sleeves 54 and 55, to hold the jigs 5| and 55 in such relative positions that the shells 44 and 45 are spaced from the stem 39 as shown in Fig. 5b. The pin is mounted in a side arm 400 of container 40 and is biased into engagement with 59 the slots in sleeves 54 and 58 by means such as a biasing spring 58a. As described hereinafter, this relationship is maintained during the 'exha'usting and baking-out process. To this end, there are provided means forsubjecting the electrode assembly 38, the stem 39 and the shells 44 and 45to exhausting and heating media. These elements are subjected to an exhausting media or vacuum by evacuating the container 48 by means of a suitable exhaust pump, in the con- 80 ventional manner. The means for subjecting thes elements to a heating medium comprises a coil 80 surrounding the container 48 in the vicinity of the elements 38, 39, 44 and 45 and adapted to be connected to a high-frequency source 65 8| through a switch52 for producing within the container 40 a high-frequency electromagnetic field to heat the electrode assembly 38 and the shells 44 and 45 to baking-out temperature in ductively. The winding 8|) is preferably constructed of hollow tubing and coupled to a source of cooling fluid such as water, as indicated.

' The apparatus of Fig. 5a also includes means external to the container 48 for initiating rela tive movement between the supporting means for the electrode assembly 38 and stem 39 and the supporting means for one or both of the shells 44, 45 to bring the shells into sealing engagement with the stem while the container 49 is exhausted and the elements are being heated by the high-frequency field of the coil 80. Thia means comprises a solenoid 53 surrounding the side arm 49c and acting on the pin 58 as an armature and adapted to 'be connected to a suitable source, such as a battery 64, through a switch 65. Upon closure of the switch, 55, the solenoid 53 is energized to retract the pin 59 against the bias of the spring 58a and release the sleeves 54 and 56 to permit movement of the jigs and 55 to bring the shells 44 and 45 into sealing engagement with the stem 39.

It is believed that the method of manufacturing an electron discharge device including a unitary electrode assembly effected by the apparatus of Fig. 5a will be clear in view of the foregoing description. Briefly, the movable cover portion 40b of the container is removed and an electrode assembly 38, supported from a sealing stem 39 having a pair of opposed annular sealing surfaces, as by means of the lead-in conductors 39b extending through the substantially annular stem 39, is disposed in the exhaustible container 40, supported in the jig 41. The shells 44 and 45 are thereupon disposed within the container 40, supported in theirrespective positions in the jigs 5| and 55, respectively, and in spaced relation to the opposite sides of stem 39. The removable cover portion 49b of the exhaustible container 40 is then replaced. The container 49 is thereupon" exhausted and the electrode assembly 39 and shells 44, 45 are simultaneously heated by means of the high-frequency electromagnetic field developed by the coil 50 upon excitation from the high-frequency source 9|. The action of the high-frequency electromagnetic field is effective to raise the temperature of the shells 44 and 45and of the various metal'elements of the electrode assembly 99 to very high temperatures, this heat being transmitted to the non-conductive elements of the assembly. This heating is continued to the point where all of the occluded gases are driven off, the container 49 being continuously exhausted during this heating or baking period.

When this process is completed, the solenoid 53 is energized through switch 55 to release the jigs 5| and 55 which,.under the influence of their biases, move the shells 44 and 45 into. sealing engagement with opposite faces of the sealing stem 39, the heating and exhausting process being continued. The shells 44 and 45 become I heated to such a degree that they fuse the portions'of the glass stem 39 with which they come in contact.

of-resistance, the portions of the fused glass be- ;come appreciably conductive and absorb additional heat from the high-frequency electromagnetic field, thereby aiding in the sealing process. When this sealing process is complete, the excitation of the winding 50 is interrupted and the parts are allowed to cool sufllciently to cause freezing of the seals between the stem 39 and the shells 44 and 45. The connection from the exhaustible container 40 to the exhaust pump is then broken, atmospheric pressure is admitted, the cover portion 40b removed, and the jigs 5| and 55 restored to their normal spaced positions in which they are held by the latch pin 59. The completed electron discharge device may then be removed from jig 41 and the apparatus is ready for the processing of a second electron discharge device.

In practice, the apparatus of Fig. 5 will be duplicated in a 'bank of containers preferably moving around a closed path so that the manui'acture of the discharge device can be made continuous andsubstantially automatic.

While the method and apparatus of the invention have been described in connection with the manufacture of an electron discharge device comprising a unitary electrode assembly supported from a sealing stem and provided with a pair of opposed enclosing shells, it is apparent that it is also applicable to the manufacture of such a device in which the sealing stem is a circular disk and only a single enclosing shell is provided.

While there has been described what is at present considered to be the preferred embodiment of the invention, it will be apparent to those skilled in the art that various changes and modification may be made therein without departing from the spirit or scope of the invention.

What is claimed as new is: 1. Apparatus for manufacturing electron discharge devices of the type including a unitary Due to the fact that glass has an extremely high negative temperature-coemcientelectrode assembly, a sealing stem and at least one enclosing shell comprising, an exhaustible container, means within said container for supporting said electrode assembly and stem in fixed relation, means within said container for supporting said shell in spaced relation to said stem, means for subjecting said assembly, said stem and said shell to exhausting and heating media,

and means external to said container for initiating movement of said second-supporting means to bring said shell into sealing engagement with said stem while subject to said exhausting and heating media.

2. Apparatus for manufacturing electron discharge devices of the type including a unitary electrode assembly, a sealing stem and at least one enclosing shell comprising, an exhaustible container including a removable cover portion, means within said container for supporting said electrode assembly and stem in fixed relation to said container, means within said container for supporting said shell in spaced relation to said stem, means for subjecting said assembly, said stem and said shell to exhausting and heating media, and means external to said container for initiating movement of said second supporting means to bring said shell into sealing engagement with said stem while subject to said exhausting and heating media.

3. Apparatus for manufacturing electron discharge devices of the type including a unitary electrode assembly, a sealing stem and a pair of enclosing shells comprising, an exhaustible container, a first Jig within said container for positioning and supporting said electrode assembly and stem in fixed relation to said container, second and third Jigs within said container and on opposite sides of said first jig for positioning and supporting said shells in spaced relation to said stem, means for subjecting said assembly, said stem and said shell to exhausting and heating media, and means external to said container for initiating movement of said second and third supporting jigs to bring said shells into sealing engagement with said stem while subject to said exhausting and heating media.

4. Apparatus for manufacturing electron discharge devices of the type including a unitary electrode assembly, a sealing stem and at least oneenclosing shell comprising, an exhaustible container, means within said container ior supporting said electrode assembly and stem, means within said container for supportingsaid shell in spaced relation to said stem. means for subjecting said assembly, said stem and said shell to that ma heusmspwee'ri-om said m means 1 ior subjecting said assembly, said stem and'ssid shells to exhausting and heating medimand means exhausting heating media. means for biasing said two supporting means to bring said shell into sealing engagement with said stem, latching means for normally restraining said supporting means from stem-engaging movement, and means external to said container for releasing said litiich- 1118 means.

5. Apparatus for manufacturing electron discharge devices or the type including a unitary electrode assembly. an annular sealing stem surrounding said assembly and a pair of opposed enclosing shells comprising, an exhaustible container, a central supporting post in said container, a first Jig mounted on said post 101' psitioning and supporting saidelectrode assembly and stem, second and third 118s siidably mounted on said post for supporting said shells, means for biasing said second and third Jigs to bring said shells into sealing; engagement. withsaid stem, latching means for normally holding said second and third 118s in such relative positions externalto said container-tor releasing said .s-latchingmejans.

The following references are of record in the iile of this patent:

Number 3 2,180,988 2,ooe,a1s 2,223,031 2,229,436

Number UNITED rsm'rs Name Date Gustin Apr. 20, 1926 Quarr'ie July 21.1942

Patterson Mar. 8, 1928' Madden et al. July 10, 1923 Loppacher Juneil, 1939 Lemmers Nov. 21, 1939' Zimber July 2, 1935 Edwards Nov. 26, 1940 Belg: Jan. 21, 1944 FOREIGN PATENTS Country Date Great Britain Nov. 2:. 1m

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