US2583525A - Method for sealing and terminating tubular devices - Google Patents

Description

J. YODER Jan. 22, 1952 METHOD FOR SEALING AND TERMINATING TUBULAR DEVICES 2 SHEETS--SHEET 1 Original Filed April 17, 1943 Invervtov: Joe Yodev, 04/ 105 His A=t+orneg.

J. YODER 2,583,525 METHOD FOR SEALING AND TERMINATING TUBULAR DEVICES Jan. 22, 1952 2 SHEETS-SHEET 2 Original Filed April 17, 1945 Fig 6.

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Patented Jan. 22, 1952 METHOD FOR SEALING AND TERMINATIN TUBULAR DEVICES Joe Yodcr, Erieside, Ohio, assignor to General Electric Company, a corporation of New York Original application April 17, 1943, Serial No. 483,470. Divided and this application August 15 1946, Serial No; 690,661

2 Claims.

' This invention relates to methods for basing. envelope constructions for electrical devices, in

cluding electric lamps and discharge devices.

external end cavity, or may even consist essen- This application is a division of my copending patent application Serial No. 483,470 filed April 17, 1943, which issued as Patent 2,535,773, December 26, 1950 and which is assigned to the assigneeof this application.

My invention relates to new and improved methods of sealing and terminating tubular devices such as tubular vitreous envelopes for elec-' tric discharge lamps.

The invention is especially advantageous for electric lamps whose envelopes have tubular necks or endportions, including lamps of tube form such as ordinary fluorescent lamps of the usual positive column discharge typealthough it is also adaptable to othertypes of lamps and.

electric translation devices. In suitable forms of embodiment, the invention affords advantages in maximum utilization of the tubular envelope wall for useful light output; simplicity and economy of envelope fabrication; ease and cheapness in the basing operation; simplicity and ruggedness of the base, and ease and cheapness in its manufacturej and economyof' material in the construction of the base. Indeed, the invention even permits of dispensing entirely with a base as a separate structure, by incorporating the usual base contact terminals into the envelope construction.

In forms of embodiment of the invention here illustrated and described, a tubular discharge envelope is constructed with a re-entrant-walled end, embodying an end-piece or wall set back behind the extremity of the tubular wall. some forms, this set back end portion is shown as a stem flare and inlead seal of the general, type now commonly used in fluorescent lamps;

while in otherforms, it is shown as an inlead seal disc which is in itself rather like those of certain vacuum-tubes. The set-back end portion is con+ nected to the extremity of the main tubular wall by a reentrant annular or frustro-conical inner wall, which coacts with the end piece to form an external end cavity. The preferred method of fabrication of the reentrant end wall that is hereinafter described is to fusethe tubular wall to the edge of the end-piece and to shift the end 7 piece further inward into the tube, while the material is soft, thus drawing, stretching, and retroverting the joint and the tubular wall outside-in into the tube to form this reentrant inner wall. A contact-terminal-carrying insulative base may be cemented over and into the tially of an insulative thermoplastic filler adhercut to the internal cavity wall and to contact terminal parts or biposts embedded and am chored directly in the plastic, substantially without direct attachment to the envelope, though connected to the inlead wires. Alternatively, the contact-terminals may be sealed into or through the reentrant end wall of they envelope, and

= thus anchored or attached directly and more firmly to the latter. When the contact-terminals are thus anchored strongly enough in a sufficiently rugged end wall, the insulative filler in the-end cavity may be omitted, doing away entirely with any distinct base structure.

Various other features and advantages of the invention will become apparent from the dc scription of species and forms of embodiment. and from the drawings.

In the drawings, Figs. 1, 2, 3 and 4 are frag mentary longitudinal sectional views illustrat ing stages in the fabrication of envelope ends according to the invention. I I

Figs. 5 and 6 are views similar to Figs. 1 and 4 illustrating another form of construction and its manufacture, and Figs. 7 and 8 are views similar to Figs. 5 and 6 illustrating a baselessljconstruction. I i As illustrated in Fig. 3,.the lamp L may be a discharge lamp of tubular form and of positive column low-pressure type, comprising a glass envelope tube I 0. with a reentrant-walledend l i. The reentrant end His shown as forming part of a cathode mount that includes a short hollow glass stem tube or flare l2 terminating in a fused seal l3 through which the current leads I4, 14 to the cathode 15 enter the envelope 16." The cathode i5 may consist of the usual coiled coil of tungsten wire coated with activating oxides, such as a mixture including barium and strontium oxides, and may be supplemented with the usual unactivated anode(s) it formed by transverse extensions of lead wire(s) it. When the device L is a fluorescent lamp, its tubular wall In is made luminescent under excitation by the radiation due to the electrical dischargetherein, as by means of an internal coating of phosphor l! on said wall. The envelope H] may contain a low pressure atmosphere of starting gas, such as argon at a pressure of 2 to mm. of mercury, and also a vaporizable and ionizable working substancahere indicated by a drop of mercury 18, which may exceed the amount that will vaporize during operation of the lamp L. The envelope end may also be provided with an exhaust tube 24 opening through the stem seal I3 but itself sealed-01f at its outer end 25.

The envelope end portion L is provided with a suitable base structure (not shown) of a type which leaves the luminescent envelope wall It exposed and, unobscured right to the very, ex

tremity :of the: erivelopetube and which is. provided with suitable contact terminals which may project outwardly from the base substantially beyond the extremity of themain tube (as shown in Fig. 8) and to which the current lead wires I4, I4 are electrically connected as by soldering or welding. q r

It will be appreciated'that as the base leaves the luminescent envelope wall III exposed and unobscured right to the very extremity of the envelope tube, this wall can be fully utilized for useful light output; and when the envelope is rendered luminescent by a phosphor coating or layer at its inside, this layer may usefully extend to the very end of the wall I0, andeven inward back on the wall of the reentrant cavity II. It will be understood that for the usual fluorescent lamp the. other end of the lampiis provided with a similar electrode and base structure.

' In fabricating an envelope end for a fluorescent ID by means of gas flames from circumjacent' burners 32. Usually, envelope tubes for fluores cent lamps are made with their ends reduced in diameter by an inward offset of the edge, and the tube end I 0 is so shown with'a reduced diameter neck end portion 33in Fig. 1'. Also, the envelope tube I0 :is commonly and preferably coated internally with phosphor powder I! before the mount M'i's sealed into it; but to prevent phosphor on the tube edge'or'neck end portion' 33 from interfering with the sealing in, this portion 33 is left uncoated, or the coating on it is removed in advance of the sealing in operaf tion. The tube I0 may be held'in a vertically shiftable clamp '34, and the mount M may be held or supported in proper sealing-in relation to'the-tube 'III, at a predeterm'inedsealing line thereof, by a vertically shiftable hollow metal conformation 33 that is shown in Fig. '2 is modified. In part, at least, this may be effected by 'a measure that also assists in uniting the hot edges of the parts II, 33: namely, by direct positive pressure on these softened and more or less coalescent edges, by means of a metal molding head 38 on a sleeve 39 shown in Fig. 1 as telescoped around the'support 35. This head 38 is moved up against the soft parts to finally seal them together (if this is required) and to round and trueup the corner formed by their union. The effect of this is to more or less obliterate the shoulder or lip 31, shown in Fig. 2, besides regularizing the tube end conformation and shifting. the whole mount M further inward in the axialdirectio'n into the tube I3.

The inward displacement of the stem tube or flare II, I2 by action of the head -38 on the seal at 33 may be supplemented or substitutedby an axial inward shift otherwise effected. If resorted to as a measure additional to thepressure of the head 38 on the seal at 33, this may support 35 which receives the exhaust'tube 24 r and has a more or less conical head 35 that'fits up into the stem tube I2. The support 35 may be slotted and grooved asshown to accommodate the lead wires I4, I4. Inaccordance with usual sealing-in practice, the burners 32 may revolve relative to the'parts .III, M, 34, 35, or vice versa. The 'flames'from the burners 32 play on the edge portions 33 and II, respectively of the tube It! thing further, the sealing-in operation would result 'after'cooling' in" a tube end conformation such as illustrated in Fig. 2, where the edge II of the flare I2 joins the reduced tube edge or neck, end portion 33 almost at a sharp angle,

and the reduction in diameter at 33 is retained almost unmodified. In former practice, this was the case; and the reduction at 33 afforded room be done either during suchpressure or afterward. In either case, the'flare I2 (and the whole mount M) is shifted. inward into the tube end portion III, while the material is heated and soft, by force exerted more directly on the mount or' flare, thus drawing and retroverting the edge or marginal portion of the envelope wall at 33 reentrantly outside-in and stretchingior pulling it straight (more or less'perfectly) into an inturned frusto-conical annulus-33b at thebase of the flare'IZ-almost corresponding in conicity to the flare itselfall as shown in Fig. 3, where the slight angle or difference of conicity of the reentrant wall at 3| corresponds to the fused seal between the original flare I2 and the inturned tube-edge portion 33b.' This is preferably done While the portions of tube I0 and flare I2 are stillr soft from the heat used in sealin them together as above described in connection with Fig. 1, rather than by reheating them. In this operation, the original offset at 33 in Fig. 1 is fairedaway and virtually or nearly abolished. If the material of the tube edge portion and of the flare is suitably soft over sufliciently wide zones, and the shown in Figs. 1 and 2 will generally be turned outside-in and thus incorporated into the reentrant end wall. The axial inward shift 1 of the mount M andflare I2 may be produced by pushing upward on them by means of the support 35 while'the envelope I0 is held fixed by means of the clamp 34, or by pushing downward on the envelope II! by means of the clamp, or by acombination of such movements-or in any other suitable way.

It will be seen that the turning outside-in of the tube wall at 33 (and above) as has been described not only improves'the conformation of the tube end and gets rid of the unsightly reduction in diameter at 33 without necessity fora skirted base to hide it, but also'results in hav ing the luminescent cylindrical tube Wall II) extend right to the very end of the tube,with the resultant advantage already mentioned in connection with Fig. 3. Even if the envelope tube end I lacked the end reduction 33 or any corresponding feature, the retroversion outside-in of part of the cylindrical tube wall would produce a similar advantage in respect of the zone of fusion produced in sealing the flare I2 to the tube-end edge.

Figs. 5 and 6 illustrate the application of the invention to a mount Me in which the flare type end piece of Figs. 1-4 is replaced by a simple glass disc end piece IIc which the lead-wires I4, I4 penetrate through bead-like internal and external seal protuberances Ml, 40, and through which the axial exhaust tube 24 opens centrally between the seals 40, 40. Such a, mount may be fabricated by the glass-working methods commonly used in fabricating the multi-lead ends of vacuum tubes of various kinds, with the slight modification naturally indicated by the fact that only two leads I4, I4 are sealed through the disc Ho. The mount Me is shown in Fig. 5 as supported by a vertically movable hollow metal support 350 that receives the exhaust tube 24 and has an enlarged flat head 360 with flared apertures for the leadwires I I, I 4 and the seals 40, 40. Instead of having reduced ends as at 33 in Fig. 1, the envelope tube we may originally be of uniform bore; and instead of the method usually employed for sealing in fluorescent lamp mounts M as illustrated in Fig. 1, the mount Mc may be sealed in accordance with usual incandescent lamp practice: that is to say, the upright tube portion Ill is placed around the mount disc IIc with the latter some distance (e. g., some 1 to 1 inches) above the open lower tube end in sealing-in relation thereto at a predetermined sealing line thereof, and the tube IIlc is then heated at the region of the sealing line by flames from the circumjacent burners 32 until it draws and necks in into a fused seal with the disc edge by the weight of the subjacent tube end, which ultimately fuses through below the seal and drops off. Thereupon the support 350 may be raised higher to shift the disc He and the whole mount Mc further inward into the tube III, thus pulling, stretching, and turning or retroverting the fused seal (and even the soft wall of the tube I0) outside-in into the end of the tube III as shown at 33c in Fig. 6. The reentrant-ended tube may then be based in the manner previously described, or in any other suitable manner.

Figs. 7 and 8 illustrate a variant of the method and construction shown in Figs. 5 and 6 whose distinctive feature is that instead of having through leadwires I, I4 sealed through the disc end piece Nd and afterward connected to contact terminal pins of a distinct or separate base structure, the contact terminal pins 2Id, 2Id are themselves sealed directly through the disc I Id and 40d, 40d and carry short internal leadwires I4d, I4d between which the cathode coil I5 is connected. In other respects, this construction and its fabrication may correspond to what has already been described in connection with Figs. 5 and 6, including the pulling, stretching, and turning in of the fused seal at 33d and the wall of the tube I0. Thus the lamp base is essentially merged in the lamp envelope end construction, and special basing operations are dispensed with. The pins Md, Md are firmly fixed in the glass of the end construction, which is very strong and rigid. The cavity of the reentrant lamp end may if desired be filled in around the pins Md, Md and the exhaust tube seal 25d with an insulative filler of cement, sealing-wax, or other thermoplastic, like Bakelite, for instance, thus fortifying the anchorage of the pins, and protecting the seal 25d and the reentrant tube end IId from accidental damage.

It will readily be appreciated that the constructions illustrated in Figs. 6 and 8 not only allow of renderin the tube wall luminous with phosphor I! right up to the very end. Nd and even on the main central area of the latter, but also allow of placing the cathode I5 as close as possible to the very end of the tube wall, so that all the phosphor coating shall be effectively excited by the electric discharge in the tube.

In Figs. 2, 3, and 4 to 8, various parts and features are marked with the same reference characters as are applied to corresponding parts in the earlier figures, in order to dispense with repetitive description, a distinctive letter being added where such distinction appears needful.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The method of manufacturing a tubular fluorescent lamp having its envelope coated internally with fluorescent material to the very ends thereof, which method comprises positioning an end piece in sealing-in relation adjacent an end of an envelope coated internally with fluorescent material except for a limited uncoated end portion of its wall extending inwardly beyond the region of the envelope wall to be sealed to the end piece, thermally softening and sealing the said uncoated end portion of the envelope to the edge portion of the end piece, and, while the material is soft, turnin the entire uncoated end portion of the envelope, inwardly of the seal, reentrantly outside-in by shifting the end piece inward into the envelope.

2. A method of manufacturing a tubular fluorescent lamp having its envelope coated internally with fluorescent material to the very ends thereof, which method comprises positioning an end piece in sealing-in relation to one end of an envelope having reduced diameter neck end portions and coated internally with fluorescent material except for the said neck ends thereof which are uncoated, thermally softening and sealing the uncoated neck end portion of the envelope to the edge portion of the end piece, and, while the material is soft, turning the en tire uncoated neck end portion of the envelope wall reentrantly outside-in by shifting the end piece inwardly of the envelope.

JOE YODER.

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

UNITED STATES PATENTS Number Name Date 1,461,155 Madden et al. July 10, 1923 1,842,184 Madden Jan. 19, 1932 2,349,822 Gardner May 30, 1944 FOREIGN PATENTS Number Country Date 108,574 Austria Jan. 10, 1928

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