US2006568A - Method of sealing metal wires to glass - Google Patents

Description

y D. s. GUSTIN ET AL METHOD OF SEALiNG METAL WIRES TO GLASS Filed July 1, 1952 2 Sheets-Sheet l INVENTORS 11.5. GUST/N w. .D. FL 0 lav/ 779 ATTORNEY v July 2, 1935. D. s. GUSTIN ET AL METHOD OF SEALING METAL WIRES TO GLASS Filed July 1, 1952 2 Sheets-Sheet INVENTORS Z7. .5. GUS TIN W 3 FL z I W mom; I

Patented July 2, 71935 UNITED STATES PATENT OFFICE ME-rnon or SEALING METAL wines 'ro cuss Daniel S. Gustin. and Walter D. Flock, Bloomfield, N. J., assignors totwestinghouse Lamp Company, a corporation of Pennsylvania Application July 1,1532, Serial No. 620,368

4 Claims. (01. 49-78) J 5 vided and sealed in a wall of a glass -bulb or such character that they may be hermetically in sealed through the glass wall of an envelope. The-leading-in wires are, therefore, made of a material which will wet with the glass and al- I though metallic conductors of various metals have been employed, the most commonly used is a conductor composed of what is termed Dumet wire. Dumet wireis formed with a nickel iron core and an outside surrounding copper sheath,

Thewire is of such character that'it has substan ti'ally the sanie co'efliciency ofexpansion as the glass in whichit is used and the copper has the property of wetting and hermetically sealing with the glass. Although Dumet wire has been used over a long period and has given satisfactory results in themanufacture of large volumes of lamps and other devices, it has always been found that a certain amount of shrinkage, due to leaks occurring, attended the use of dumet as well as the use of other -leading-in conductors employed under similar conditions. This shrinkage is due to various causes and principally by reason of the oxide which accumulates on the surface of the wire when it is exposed to the atmosphere and when heated during the usual manufacturing operations. It isimpossible from a practical manufacturing standpoint to entirely clean the wire orprevent the formation of oxide thereon during the sealing-in operation and for this reason a certain percentage of lamps manufactured develop '40 what is known as leakers, which permit the entrance of air into the bulb with detrimental results, insofar as thequality and life of the lamp are concerned.

It is an object of the present invention, therefore, to provide a step in the manufacture of vacuum devices wherein portions of the leadingin' wires to be sealed in the glass are conditioned to more effectively wet with the glass.

Another object of the invention is to provide a method of sealing a metallic conductor in a glass wall in the presence of a reducing atmosphere.

Another object of the invention isto provide glass .body while plastic by enveloping av portion of the conductor to be sealed in a reducing at- 'mosphere and in pressing the glass body around such portion.

Another object of'theinvention is to provide a method of cleaning the surface of a metallic 5 conductor by surrounding the same with an ignited gas and in compressing the glass body while plastic around the said enveloped portion of said conductor. Other objects and advantages of the inven- 10 tion will be more clearly understood by reference to the accompanying drawings in which:

Fig. l is a; side elevational View of a portion ofthe machine partly in section for performing what is termed a butt-sea1ing operation in con- 15 nectiori with a miniature type of lamp; v 2 is a cross sectional view of a lamp after the butt-sealing operation has been performed showing the sealed-in lead wires and the extending exhaust tube; 1 20 Fig. 3 shows the lamp after the exhaust tub has been tipped off the top and constriction being shown in dotted lines;

Fig. 4 a view taken on line IV--IV in Fig. 1 and shows, on a larger scale. the ring of flame resulting from the passage of the reducing at- -mosphere between the exhaust tube and the bulb neck;

Fig. 5- shows anotherform of stem which may be manufactured in accordance with the present method, the stem being shown in cross section;

Fig. 6 is a view looking upwardly toward the 1 lower end of the stem shown in Fig. 5 and Fig. 7 is more or less a diagrammatic illustration of a machine for holding the parts of the stem, shownv in Fig. 5 m position to have the leading-in wires sealed therein.

The present invention may be used in'connection with the sealing-in of wires either through the wall-of a bulb as shown in Figs. 1 to 4 or it may be employed in connection with'the manufacture of astem as shown in Figs. 5 to 7. It may also be used in connection with various other types of lamps and in the manufacture of other types of stems. The lamp shown in Figs. 1 to 5 is what is termed a miniature lamp andis manufactured by a, so-called butt-sealing operation.

, In performing this operation a bulb is held with the neck projecting upwardly and a mount is positioned with the lead wires extending laterally from the neck and resting on the edge thereof. An'exhaust tube is then positioned so that its longitudinal axis is in alignment with the longi-' a method of sealing a metallic conductor in a tu dinal axis of the bulb and is. mbved so that the is in close abutting relation thereto with the lead wires interposed. Flames are then directed against the neck of the bulb and the lower end of the exhaust tube to heat them until they become plastic after which they are moved relative to' each other until they abut and consolidate, sealing the leading-in wires through the wall thus formed.

- This operation is well known in the manufacture of incandescent lamps and is. clearly shown and described in Patent Number 1,742,153 issued December 13, 1929. In the present invention, mechanism for accomplishing the above operations may be the same as that shown in the above mentioned patent and suilicient structure is illustrated to give a clear understanding of the invention and the application of the present method as a step in the manufacture of devices of the character to which the invention relates. As shown in Fig. 1, a bulb It may be supported in a holder in the form of a vacuum cup Ii which has a vacuum passage l2 connected to a vacuum line [3. The vacuum cup support H is mounted on a rotatable head l4 including a plate l5 secured to the upper end 01a spindle IS. The spindle isrrotatable in a hearing I! on an arm 18 of a rotatable conveyor. The spindle I6 is provided with a gear wheel IS in mesh with a continuously driven gear wheel 2|. The lower end of the spindle i6 is provided with a roller or cam follower 22 which traversesthe surface 23 of a .cam 24 mounted on a cable 25. The cam surface 23 is formed to slightly raise and lower the spindle l 6 for a purpose to be presently described. The plate l5 is provided with a post 26 the upper end of which is equipped with a pair of gripping jaws 21 to hold an exhaust tube 28 in alignment with the bulb end in the cup II.

The structural arrangement of the mechanical elements is such that when the bulb is positioned in the cup the exhaust tube is held by the jaws 21, the longitudinal axis. of the exhaust tube coincides with the longitudinal axis of the bulb so that the lower edge of theexhaust tube and the edge of the bulb neck will register when movedto abutting relation. When the bulb" l is in pwition and before the exhaust tube is applied, a mount 29 is positioned in the bulb'.- This mount consists of a filament/3| and lead wires 32 and 33 held by a glass bead 34. The lead wires of the mount are bent outwardly as shown so that the filament is heldin position in the bulb by resting the lead wires on the edge of the bulb neck. The lead wires are not; however, bent at right angles so that they contact with the flat edge of the bulb wall, and are. thus almost entirely exposed to the action of areducing atmosphere as provided in accordance with the present invention.

For the purpose of improving the manufacturing process, the present invention provides means in the form of a nozzle 35 for directing a stream of a reducing gas 36 into the exhaust-tube 28. It has been found, although various reducing gases may be employed such as a mixture of hydrogen and nitrogen or the like, that good results are obtained by employing a gas of relatively low cost such as the ordinary illumina ing gas. In practicing the present method, the gas passes down the exhaust tube which is held withv its lower end in-rel'atively close spaced relation to the neck of the bulb leaving an annular opening 31 through which the gas is forced and from which it issues in the form of a reducing zone which becomes ignited by fires 88 and I! which are directed against the bulb neck and the end of the tube to render them plastic for consolidation.

When the glass parts are in a proper state of plasticity, the cam 24 operates to slightly raise the bulb l0, pressing the plastic portions'of glass together and thus consolidating the bulb and exhaust tube and consequently sealing the lead wires at the united portions. This operation is performed in the presence of the reducing atmosphere or while the portions of the lead wires to be sealed are enveloped in the ignit'ed reducing fluid. I By performing the reducing operation substantially simultaneously with the fusing operation, the portions of the lead wires to be sealed are entirely free of any foreign material and by reason of the enveloping reducing atmosphere no oxides can form leaving the copper surface in its best condition for wetting and thus hermetically sealing with the glass. It will be understood that the present method wherein the portions of the wires to be sealed are enveloped in the ignited gas that the surrounding gas actually prevents the formation of-the oxides which would ordinarily form.

In the operation of sealing lead wires in a press or in the wall of a bulb the portions of the wires to be sealed are unavoidably heated by the flres which are employed to heat and soften the glass. Thus in the absence of the present method an oxide is formed on the surface of the heated por tions of the wire with the result that since the oxide is interposed between the surface of the wire and the glass the necessary intimate contact to make an air-tight seal is unattainable. When the present method is employed the reducing gas, which, by means of the glass heating fires is ignited, envelops the portions of the wires to be sealed in a gas flame which prevents the formation of oxide and leaves the surface clean and effective .to make a hermetic .seal and thus removes loss due to leakage.

The burning gas, which flows from the inside of A in Figs. to '7. As shown in Fig. '7, two pairs of jaws 4| and 42 are provided to ,hold an exhaust tube 45. A flare tube 44 may be held by a pair of jaws 45. The several pairs of jaws are so arranged that the exhausttube 43 may be held in concentric relation and extend within'the flare tube 44. A lead wire support block 46 may be provided having suitable apertures torec'eivelead wires 41 and 48 in position within the flare tube and with ends extending below the neck 49 there- .of. A'pair of press forming jaws 5| and 52 are provided pivoted at 53 and. 54 and operated by means of a lever 55from a sourceof power not shown. These jaws serve to compress the flare tube and exhaust tube after portions thereof have been rendered plastic by means of suitable fires 56 and 51. Mechanism for performing this operation as well as the operation of blowing air down through the exhaust by means of a nozzle 58, indicated in dottedfijllnes in Fig. 'l, :is'*

well known in the lamp art. 'fiie purpose of the nozzle 58 is to force air into the exhaust tube after the same has been consolidated with the flare tube in a plastic mass and while the mass is still plasthe portions of the lead wires to be sealed in the glass. The flare tube 44 is held above the support 46 to provide an annular opening 63 for the passage of the reducing fluid which issues in the form of a surrounding ring 64. This issuing fluid is ignited thus completely excluding the entrance of any air to portions of lead wires to be sealed and obviously the filling of fluid within the flare tube will prevent the entrance of air from the opposite side of the exhaust tube. While the lead wires are thus enveloped in a reducing atmosphere, the jaws and 52 are actuated and the plastic glass is compressed about the lead wires in the presence of the reducing atmosphere thus sealing the wires and making it possible to obtain a seal under ideal conditions.

It has been found that when practicingthe present method, a great saving is accomplished in that leaks are avoided andthe defective seals which were prevalent heretofore are eliminated. Various materials have been used for lead-in wires and one of the greatest difficulties has been to provide a metallic conductor which would be dependable in wetting with the glass but although good wetting materials have been obtained and the results have been satisfactory up to a certain point; the difliculty always remained of having a certain percentage of defects by reason of the impracticability of -obtaining wire with the surface free from oxide or other foreign substances which operate to destroy the effective wetting property of the material used. By reason of the present invention the portions of the leading-in conductors to be sealed in the glass are so treated that their wetting properties are' improved and consequently, when employing the present method, the cost of manufacture is-reduced by reason of low shrinkage. I

Although a preferred embodiment of the invention is shown and described herein, it is to be understood that modifications maybe made therein without departing from the spirit and scope of the appended claims.

What is claimed is: 1. The method of butt-sealing which comprises This supporting a bulb, disposing lead wires with portions extending from the bulb neck, positioning an exhaust tube with one end adjacent to portions of said wires, directing a flow of a reducing gas down said exhaust tube and around said portions of said wires, heating to render plastic the bulb neck and the end of said tube and in moving' the bulb and exhaust tube to compress the plastic portions about the wires.

- 2. The method of making an incandescent electric lamp of the butt-seal type which comprises positioning a lamp bulb with the neck portion extending upwardly, disposing a lamp mount within said bulb with the lead wires, projecting at an angle to the neck wall and resting on the edge of said neck, positioning an exhaust tube with its longitudinal axis coincident with the longitudinal axis of said bulb and with its lower end in spaced relation to said bulb neck to provide an annular outlet, directing a reducing fluid into the upper end of said tube for discharge from said outlet, heating adjacent portions of said tube and bulb neck, and in compressing the heated portions about said wires.

3. The method of butt-sealing which comprises supporting a bulb, disposing lead wires with portions extending from the bulb neck, positioning an exhaust tube with one end adjacent to portions of said wires, directing a flow of a reducing gas down said exhaust tube and around said portions of said wires, heating to render plastic the bulb neck and the end of said tube and in changing the relative positions of the bulb and exhaust tube to compress the plastic portions about the wires.

4. The method of hermetically sealing an electrical conductor oxidizable in air in a fused wall in a tubular glass part which comprises surrounding a conductor with one end of said tubular part, directing a flow of reducing gas said conductor;

DANIEL S. GUSTIN. WALTER D. FLOOK.

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