US2581945A - Apparatus for sealing-in electron tubes and the like - Google Patents

Description

R. F. DORAN 2,581,945

APPARATUS FOR SEALING-AIN ELECTRON TUBES AND THE LIKE l Jan. 8, 1952 Filed Nov. 27, 1943 INVENTOR ROBERT Fo/A/v AT ORNE Patented Jan. 8, 1952 APPARATUS. FOR- SEALING-IN ELECTRON I `TUBES AND THE LIKE.

Robert F. Doran, Emporium, Pa., assgno'r to Sylvania Electric Products Inc., a*corporationot'Massachusetts Emporium, Pa.,

Application November 2v, 1943, serial No. 511,915

serts the headers into the holder heads, the electrode mount pointing upwards, and slips the `glass bulb downward-'ly over the electrodev mount.

Usually Athe sternv Vis providedv with an exhaust" tabulation, which nts into an axial hole in the spindle head. If' desired, 'means may be prov vided' 'to supply an inert' gas through bores in the spindles into the exhaust' tubul'ation in or-v der 'to prevent oxidation of the mount elements when thel glass' of the envelope and the header is heated for sealing-in.

When the bulb or envelope is downwardly telescoped over the mount, it is usually held in position by special bulb supporting Varms attached to. and spinning with the spindle', or it may' rest with the rimof' its open end in' abutting relation against the periphery of the header; andtaken up before. sealing by grippers into chucks' which rotate and.' spin synchronouslyverti'cally abovethe header-holding spindles'.

@nel disadvantage of this: methodrv of sealing-in tubes, with the open rim of the envelope or bulb facing downward, is that the gravitational forcesv acting ony thefsoftened glass: at the' lower open end of' the envelope tend to pulll this softplastic glassdownward, with the resultthat the lower p'artfof` thev wall ofv the envelope becomes thinner, while the excess glass owing downward increases the thickness of the header.

Itis, therefore, an object of the invention. to provide means. for employing the gravitational forces, actingfon' the softening glassl rim of al glassenvelope during sealing-in, for the purpose of increasing the wall thickness of the glass envelopet in that region.'

Another object of the invention is, to provide ln'eansz'for` employing they gravitational forces, acting'on the softening glass rimof a glass' header during sealing-in, for obtaining a gradually decreasingI glass thickness from the header which is relatively thick, tothe bulbglass wall which is relatively? thinner.

1n some types of tubes, in particularin sina'sllfv secutivel positions.

tubes as used e.A g., in hearing aid ampliiiers; thev header isf too small to. provide enoughspace for attaching an exhaust tubulation of sufliciently large diameter for insuring the desired pumping speed' during exhaust of' the tube. The

exhaust tubulation in thesel tubes is, therefore, usually attachedto the closed rend of the enfv velope, opposite to the header end. 'If it is dei si'recl to introduce an inertgas through the tu--A bulation during sealing-in with the conventional position of the glass bulb above thel headerdur# ing sealing-in, special means must be provided for supplying the gas from'above'ainto they tu bulation and for' preventing thev glass bulb from tumbling e. g., through al pipe system provided the overhead chucks, or in 'any feasible manner. This complicates the: mechanical constructicin of the sealing-in machinel It is, thereforaa principal object of' theA invent-i tion to devise an apparatus' for' sealing-in vac-v uum discharge tubes in which only fone of 'the' two parts to' be sealed togetheris directly sup-f portedby external means. y f It is another object of the invention to pro-2 videI means for sealingin a vacuum tube 'as sembly, in which the header-mount assembly 'isi supported directly by the glass envelope into' which it is to be sealed. A According toa further object of the' invention, means are provided for supporting a tubula'ted glass envelope from below, with the open end -Jf the envelope pointing upward and" withv thel exhaust tubulati'on downward'. l

A still further feature of the invention refers to the application o f' a pair of working rollers ina fixed shaping position abovey an intermit-l tently 'rotating seal-in table.

Another object of the invention is toprovide means for forming a perfectly'smooth"butt-seal by the combined application of g'jas pressure intoI a glassenvelope from below, the weight ofthev header and mount, and of a According tol a: still further object of the in-f "vention, means are provided tov prevent exces` Fig. 1 is a top-plan view of a sector of the' intermittentlyy rotating table showing two con- Figz 2 1Saside Viewy of the tube being seared-in, just as it is entering the shaping position.

Fig. 3: isa side viewv of' a tube` in Lthesh'aping i position, at the end of thev shaping operation.

dexing drive with respect to a stationary rack l The indexing motion is so. con- (not shown) n trolled, that the holding heads'and spindles'come to a stopl in certain working positions, whereV they remain stationary for ay fixed interval. ITwo of these positions are indicated inthe flgureand i marked as positions (A) and (B). The spindles 3 with heads -2 include areceptacle 5 for the exhaust tubulation 6 and the lower part I of the bulb 8. By virtue of the low center of grav- I ity of rollers I9 and 20 and their contact with fthe cooler and solid part of bulb 8, extensive reduction in bulb diameter is avoided.

In order to Vavoid sliding down or sagging of the Yheader `inside the softening wall of bulb 8, as a result of thedeformation of the header in recylindrical glass bulb 8, each spindle being pro-.UY

vided with a bore 9 through which a neutral gas e. g., nitrogen is supplied as indicated bythe vertical arrows in Figs. 2 and 3. In position (A) of Fig. 1, a pair of torches III and II is provided for bringing the upper portion I 2 lof bul-b 8 andv the Vperipheryof header- I3 to softening temperature. glassthan the bulb and is dome-shaped witha fiat but slightly inclined peripheral edge I4 on its lower face where it initially seats against the rim; I5 Vof the bulb. Header I3 has the usual lead-in wires I6. preseated therethrough,` and any well-known form of electrode. assembly II is Iattached to and supported by wires I5. The weight lof mountI 1l tends to Vexert downwardly directed forces on the r-im I8 of thesoftening header, .and pressesdownwardly and outwardly on the open upperrim' I5 vof the glassbulb with enough pressure to overcomethe yrespective surface tensions of the two glass parts,y thus effecting a mutual wetting and puddlingV to begin the sealing operation.A The gasis now -trappedbe-v tweenIS and I8 and its pressure through the tubulation is high enoughtoi expand thew sealingportion of the softened header and the portion I2 ofv the. bulb, radially outwardf,so.as to impartito it a bulging shape similar to that indicated in Figs. 2 and 5. When the viscosity of the glass has been sufiiciently lowered by the heat applied in position (A), the head Zand spindle 3 are indexed into position (B), where a pair of graphite rollers Iiiand are located. These rollers may be suspended by levers 2l, 22, from hinges 23 and 24, attached to stationary rod 29. ARollersIS and 20, may .be separated by theindexing motion of table I so asto provide a clearpath for the bulb 8 and header I3 ybe-` tween the rollersas shown in Fig. 2. As soonas the table I is atrest again after completion'of the indexing motion, the rollers I9 and 20 close (Fig. 3) and theirl weight works therhot glass fromthe outside, whereby a perfectly smooth transition between the cylindrical part of the bulb and the header is obtained. By properly1 locating the hinges 23 and 24, and by proper choice of the diameter of the rollers I9 and 2i), the straightness of the seal asl shown in- Fig. 3 Vbetween the cylindrical bulb and the header can easily beinsured, and the proper amount of radially vinwardand upward pressure exerted by the rollers on thesoft .glass seal and can easilyv be adjusted, e. g., by counterweights and 26, adjustably attached to horizontal rods` 21 and 28, which formvbell-cranks with arms. 2l and 22. I twill be observed that the hinges or. pivots- 23 and 24 are located considerably above the soft- The header I3 is of much thicker.

sponse to the sealingtorches applied in position (A), and in response to the weight of the tube mount I'I, the header is, in accordance with the invention, made slightly-dome-shaped or saucershaped, with the convex side pointing upward as shown in Figs. 2 and 3.- Itis clear therefore, that the periphery of the header willexert a downward pressure on the upper margin of the glass bulb as the header tends to iiatten out.' This results ina taperedthickening of the bulb rim at the sealing region and in a smoothly tapered final sealas shown inFig. 3. Y n Y This feature is very important. Y If a fiat discshaped header is used in this method of sealing;v in, the shape of the originally flat header deforms and 4collapses into a downwardly convex curvedv surface Ain vresponse to the weight of. the vlmount` when the header softens. y

Accordingly-anat header has a tendency-to slip down into the envelope, which frustratesthe formation of the desired uniformly tapered seal,

duer tor formationv of forcesl pulling the periphery.

of the header radially inward. Such forces not only decrease the downward-pressure ofthe peri-'- phery of the header on the softening YbulbV rim,

but represent a pulling away of the headerxpe-Y riphery from the seal with the 4rim of the en,- velope. l

'With the foregoing described method of seal-l ing-in, a minimum of heat is transmitted to the interior part of the mount andvit is not necessary to support mechanically lthe header from opposite ends. Y f g I It will be understood that if the gravitational,4 forces acting on the header are insucient to ef:r fect the proper working of the softened glass, it may be supplemented by pushing down on-the header. Thus if the header is of the typewhich carries -the exhaust tubulation, this-tubulation.

may at-the sealing-inposition be subjected to a downward pressure. Y

Various changes and modifications can be made-'z without departing-from the spirit and scope ofA the invention. y I y What is claimed is: Apparatus for sealing-in arelatively thick glass header to a thinner-walled glass bu-lbyrwhich apparatus is-,of the type comprising a turntable indexable to a seriesof successive positions atA which operations are to be performed, a plurality of rotatable heads carried by said turntable, each head having means to receive and support abulb with its mouth uppermost and with the headerV resting on the lip of-V the-mouth, means eilectiye in one position of said turntable for heating the,

contacting regions ofthe Vb ulb and header to softening temperature and for admitting gas un-v der pressure to the interior of the bulb -to 'causer the .softened regions to bulge outwardly, the feaand mount- 5 6 ture of novelty which includes meansI effective in UNITED STATES PATENTS another position of said tuintable to press the Number Name Date bulged region mechanically inwardly comprising 565 576 Smith et a1 Aug 11 1896 a pair of weighted rollers which are pivotally sup- 1 955058 Eden Ap1. 17 1934 ported on pivot points located above and beyond 5 2082848 Rose 31. June 8 1937 the boundary of the said bulb, each roller having a 2089044 Thonlas` Aug 3 19,37 length which is substantially greater than the 2131923 Thomas Oct 4 1938 length of the said softened regionswhereby the 2237186 Mauoy 1 Apr: 1 1941 inward movement of said rollers is limited by their 21268510 Kmberg et a1 Dec 30 1941 gieaxlileit respectively with the unsoftened wall l0 2,296,579 Seelen Sept 22: 1942 Y 2,334,001 Hapgood Nov. 9, 1943 ROBERT F DORAN' 2,334,123 Perkins Nov, 9, 1943 REFERENCES CITED The following references are of record in the 15 ille oi this patent:

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