US2983078A - Method of sealing a vitreous conduit - Google Patents

Description

y 1961 G. R. MISTLER ETAL 2,983,078

METHOD OF SEALING A VITREOUS CONDUIT Filed July 12, 1957 2 Sheets-Sheet 1 INVENTORS 650265 E. M/JIZE'Z, LOU/.5 A. N/(OA/IEO y 1961 G. R. MISTLER ETAL 2,983,078

METHOD OF SEALING A VITREOUS CONDUIT Filed July 12, 1957 2 Sheets-Sheet 2 I VIII/Ill INVENTOR5 650265 1?. M/STLEE 400/; L. N/L'OLHEO E BY 02%,

United States Patent Ofifice 2,983,078 Patented May 9, 1961 2,983,078 METHOD OF SEALING A VITREOUS CONDUIT George R. Mistler, West Orange, and Louis L. Nicolaro, Roseland, N.J., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Filed July 12, 1957, Ser. No. 671,603 Claims. (CI. 4978) This invention relates to seals for vitreous conduits and to methods for effecting same and, more particularly, to a seal or tip-01f for a vitreous tubulation, particularly for lamps, and to a method for eiiecting this seal.

In the fabrication of an incandescent-type lamp such as a projection lamp, for example, the filament and attendant connecting and supporting members are first placed into the envelope and it is completely heremetical- 1y sealed except for what is known as a tubulation, which comprises a vitreous hollow conduit opening into the lamp envelope. The lamp envelope is then evacuated through this tubulation and a gas fill, if used, is inserted to the desired pressure. The tubulation is then hermetically sealed in order to complete the fabrication of the envelope. In lamp types where the gases within the envelope are at less than atmospheric pressure, the tubulation is normally sealed or tipped-01f by heating an annular portion of the glass comprising the tubulation to its softening temperature and pulling apart the tubulation at this heated portion. The heated glass at this pulledapart tubulation portion forms an hermetic seal. If the fill pressure within the envelope is greater than atmospheric, the tubulation must be sealed or tipped off by other means since heating a portion of the vitreous tubulation to the softening temperature would cause this heated portion to blow out under the greater internal pressures within the envelope. Sealing of such a pressure-type lamp is normally accomplished by means of a chamber about the tubulation, which chamber contains a greater-than-atmospheric pressure or by means such as heated jaws, for example, which heated jaws press against the tubulation from either side to effect the tip-01f or seal.

In all of the foregoing systems for tipping-off a vitreous tubulation, the tipped portion or seal of the tubulation will be fairly thick because of the manner in which the tip is made. Such thick sections of tubulation will contain considerable residual strains since the glass comprising the tubulation must be heated quite high to reach the proper softening temperature, and when cooling these relatively thick tubulation tip-01f portions, many residual strains are set up. In addition, the attainment of a tip which is flush with the envelope is very difiicult to achieve as this requires heating the envelope portions adjacent the tip-off with resultant strains and deformation in the envelope itself. Where the envelope fill pressures are greater than atmospheric so as to require what is termed pressure-tipping in order to form the hermetic seal, the equipment utilized is quite bulky and complicated and the tip-off is quite thick.

In order to avoid and overcome the foregoing and other difliculties of and objections to the prior art, it is the general object of this invention to provide an hermetic seal or tip-off for a vitreous conduit or tubulation for an hermetically-sealed envelope, wherein the seal has a minimum of residual strains.

It is a further object to provide a tubulation tip-off which may be made substantially flush with the envelope.

It is another object to provide a method for tipping ott a tubulation with a minimum of applied heat to produce a seal having a thin cross section, in order to minimize residual strains.

It is still another object to provide a method for tipping oif a tubulation which may be fabricated of any type of glass and which method will operate whether the connecting envelope is filled with high-pressure gas or is a vacuum type.

It is a still further object to provide a method for tipping off a tubulation wherein the applied heat may be minimized and limited only to the tubulation itself without exposing surrounding lead wires, etc., to the heat utilized in elfecting the tip-off.

It is yet another object to provide a method for tipping off a tubulation of any reasonable size with regular or irregular shape.

The foregoing objects of the invention, and other objects which will become apparent as the description proceeds, are achieved by providing an hermetic seal or tipolf for a vitreous conduit or tubulation wherein the tipoif portion of the tubulation comprises a thin layer of displaced tubulation material which has an average thickness somewhat less than the Wall thickness of the tubulation. This thin layer comprising the hermetic seal will normally be disposed generally transversely to the axis of the tubulation and, if desired, it may be placed proximate the envelope so as to be essentially flush therewith. To efiect this tip-off, a method is provided which comprises forcibly moving an elongated, hot sealing member or wire through the tubulation so that the hot sealing member will heat the tubulation portions contiguous therewith and allow the member to pass through the tubulation. The passage of the member through the vitreous tubulation pushes a substantial amount of vitreous material ahead of it and forms a continuous layer of displaced tubulation material across the tubulation cross section. At least a stratified portion of the continuous layer of displaced tubulation material is at a sufliciently low temperature to resist such substantial deformation as is required to rupture the continuity of this layer. As thesealing member is then forced completely through the tubulation, the continuous layer of displaced tubulation material will form the hermetic seal.

For a better understanding of the invention, reference should be had to the accompanying drawings which are. not drawn to exact scale and wherein:

Fig. l is an elevational view of an apparatus for tipping oif a vitreous tubulation;

Fig. 2 is a plan view of the apparatus shown in Fig. 1;

Fig. 3 is a cross-sectional view taken on the line IIIIII in Fig. l in the direction of the arrows;

Fig. 4 is an alternative embodiment of the hot sealing member used for effecting the tip-off;

Fig. 5 is a cross-sectional view taken on the line V--V in Fig. 3 in the direction of the arrows, showing the first step of making the tip-off;

Fig. 6 is a cross-sectional view showing a partiallycompleted tip-off for a tubulation which is under greaterthan-atmospheric pressure;

Fig. 7 is a view taken on the line VII-VII in Fig. 6 in the direction of the arrows;

Fig. 8 is a cross-sectional view corresponding to Fig. 6, but showing a tip-off wherein the tubulation is at atmospheric pressure;

Fig. 9 is a cross-sectional view corresponding to Fig. 6, but wherein the tubulation is at less than atmospheric pressure;

Fig. 10 is a cross-sectional view showing the justcompleted tip-off wherein the tubulation is at greater-thanatmospheric pressure;

Fig. 11 is a view taken on the line XI--XI in Fig. 10

' in the direction of the arrows;

Fig. 12 correspondsto Fig. 10, but wherein the tubulation is at atmospheric pressure;

Fig. 13 corresponds to Fig. 10, but wherein the tubulation is at less than atmospheric pressure; V 1 Fig. 14 illustrates an alternative embodiment for carrying out the method wherein the tubulation is separately preheated before tip-ofl;

Fig. 15 illustrates an alternative embodiment wherein the cross-sectional configuration of the hot sealing memberused for effecting the tip-off is circular;

' Fig. 16 shows another modification for the configuration of the tip-01f member and also shows the motion of the tip-E member in a direction which is oblique with respect to the plane of the cross section of the tubulation; Fig. 17 shows a tipped-off tubulation wherein the seal portion is oblique with respect to the cross section of the tubulation;

Figs. 18 and 19 illustrate the method of making a flush-type tip-off and the resulting tip-off;

Fig. 20 illustrates a tip-0E which has been made within a recess formed by the furthermost-projecting portions of the envelope in order to minimize any interference with lamp base caps or lead wires, for example.

.Although the principles of the invention are broadly applicable to hermetic sealing of any type of vitreous conduit, the invention has particular reference to sealing a vitreous tubulation for an otherwise-sealed envelope, such as a lamp envelope, and hence it has been so illustrated and will be so described.

With specific reference to the form of the invention illustrated in the drawings, in Figs. 1 and 2 is shown an apparatus 30 for tipping oflf the vitreous tubulation of an otherwise hermetically sealed lamp. The tubulation 32 of the lamp envelope 34 connects to a standard tubulation-receiving chuck 36, such chucks being well-known. The chuck 36 receiving the tubulation 32 connects to an exhaust or pressure line 38, which may be connected either to a pressure source or a vacuum source depending upon the type of gas-fill which is desired within the lamp envelope 34 (pressure or vacuum pumps not shown). The frame 40 of the apparatus carries a pivotally-mounted arm 42 which has'extending therefrom the electrical connections and supports 44 for the hot-wire-tipping 'or sealing member 46 carried between the extremities of supports 44. An extension of the arm 42 has affixed thereto a tension spring 48 and the other end of this spring 48 is connected to the frame 40 of the apparatus 30 in order to maintain a predetermined pressure between the sealing member 46 and the tubulation 32.. A tension-adjusting means 50 is provided for the spring 48. Electrical connection for the hot-wire-tipping or sealing member 46 is made from a power source (not shown), through power connections 52, through the sealing-member-support and electrical-connecting members 44 and to the sealing member 46.

In the operation of the apparatus 30, the exhaust tubulation 32 is first fixed in place and the lamp envelope 34 suitably supported. To permit the insertion of the tubulation 32 into the receiving chuck 36 the arm .2 is manually rotated in a counter-clockwise direction (rotation limits shown dotted). In effecting the tip, the member 46 is heated to a predetermined temperature and the tension of the spring 48 is utilized to maintain a predetermined pressure between the sealing member 46 and the tubulation 32. The combination of heated sealing member and spring pressure serves to effect the hermetic seal of the exhaust tubulation, as will be described in detail hereinafter.

I In'Fig. 3 is shown a cross-sectional view of the hotwire-tipping or sealing member 46 and this member will normally assume the general configuration of the exhaust tubulation 32 which is being tipped, because of the prestain the sealing member 46 in a substantially straight sures which are applied between the member 46 and 3 the tubulation 32 and the temperature to which the member 46 is heated. It is possible, however, to main configuration and such a sealing-member configuration is shown in Fig. 4.

In Fig. 5 is shown the first step in the tipping operation wherein the heated sealing member 46 is placed adjacent the tubulation so as to ,heat at least the portions of the tubulation or conduit which are contiguous with the sealing member 46. After preheating of the tubulation 32, the spring 48 is allowed to urge the sealing member 46in a clockwise direction. This causes the member 46 to effect a considerable stress on the heated tubulation 32 and the temperature of the tubulationis such that the stress applied thereto by the heated sealing member 46 causes a substantial deformation in the tubulation 32 and permits a passage of the heated sealing member 46 therethrough. The passage of the heated sealing member 46 through the tubulation 32 pushes a considerable amount of displaced tubulation material ahead of it and a substantial portion of this displaced material is pushed to and past the sides of the sealing member 46 where it forms a layer 54 of displaced tubulation material which is continuous with adiacent portions of the tubulation, as shown in Fig. 7. In making the tip as shown in Fig. 6, the pressures within the vitreous tubulation are greater than atmospheric and when the heated sealing member 46 first deforms the tubulation 32 so as to pass therethrough, a portion of the heated tubulation material adjacent the trailing edge of the heated sealing member 46 will be sufiiciently soft so that it will deform somewhat due to the pressure differentials between the interior and exterior surfaces of the tubulation. This will cause a slight accumulation of displaced tubulation material at the point of entry of the sealing member 46 into the tubulation 32.

In Fig. 8 is shown 'asealing member 46 passing through a tubulation 32 which is filled to atmospheric pressure and here the configuration of the partially-tipped tubulation is somewhat different as there are nopressure diiferentials tending to distort or rupture the continuity of the partially fabricated seal. It should be pointed out, how ever, that even with a .greater-than-atmospheric pressure within the tubulation, the continuous layer 54 of tubulation material which has been deposited by the passage of the tipping or sealing member 46, has at least a stratified portion which is at a sufiiciently low temperature so that it will resist such substantial deformation under the forces of any pressure differentials, for example, as required to resist rupture of the continuity of the formed continuous layer 54. Thus while the glass is sufficiently heated so that it will deform under the relatively large pressures applied by the sealing member, it is not sufiiciently soft that it will deform so as to rupture under the stresses of any other forces acting'o n the tubulation portions which are proximate the passage of the sealing memb er therethrough. V

In Fig. 9, is shown a partially-completed tip wherein the tubulation is at less than atmospheric pressureand here the pressure difie'rentials tend to deform the tubulation portions inwardly, a contrasted with the partiallycornpleted tip illustrated in Fig. 6.

In Figs. 10 and 11 are illustrated the completed tip or seal for a tubulation 32 which is at greater-than-atmos- .pheric pressure. As illustrated, the average thickness of the hermetic seal formed by the layer 54 is somewhat less than the tubulation wall thickness and this is particularly desirable since residual stresse s are minimized in thin sections of glass. In additiornthe re-entrant angle 56'where the displaced continuous layer 54 of tubulation material meets the tubulation wall, is quite large and this also tends to minimize stresses. I

In Fig. 12 is shown a tipped-off tubulation SZW-hich is connected to an envelope filled with gas at atmospheric pressure and in Fig. 13 is shown a tipped-o5 tubulation 32which is connected to an-envelope filled with less than atmospheric pressure]. As shoWn, as the gas. pressures shown in Fig. 15. The sealing within the tubulation decrease, the continuous layer 54 of displaced tubulation material depresses inwardly.

In all of the tubulation tip-off procedures shown hereinbefore, the sealing member 46 has been shown with a generally-circular configuration, but with a flattened leading edge. This permits the sealing member to carry ahead of it a slightly greater amount of softened tubulation material as the sealing member traverses the tubulation. There is a tendency for the continuous layer 54 of displaced tubulation material to be somewhat thinner at portions which are adjacent the portion of the tubulation where the sealing member first enters and this is apparently due to the softened glass being pulled along by the sealing member 46 as it passes. As the sealing member approaches the point of complete intersection of the tubulation, the residual glass which has been pushed ahead of the sealing member is deposited and forms a somewhat heavier deposit of glass at this point. However, the average thickness of the continuous layer 54 is always somewhat less than the wall thickness of the tubulation.

As an alternative embodiment for tipping-01f by means of the heated sealing member, the portion of the tubulation 32 which is to be tipped may be preheated to a temperature somewhat below the softening temperature of the tubulation by a gas-air flame 55 or by an electrical heating means, or other suitable heating means, as illustrated in Fig. 14. In automatic lamp-making equipment, for example, it is often desirable to preheat the tubulation before the tip-01f is made, since the conventionaltype equipment is readily adapted to perform this operation. With a separately preheated tubulation it is possible to make the tip-off more rapidly and specific examples will be given hereinafter.

While the sealing member 46 has been illustrated as having a generally-rounded configuration with a flattened leading edge, it is also possible to perform the tip-off with a sealing member 46a which has a generally-circular cross-sectional configuration and such an embodiment is member may also have a quadrilateral configuration, for example, and such a member 46b is shown in Fig. 16. In the embodiment as illustrated in Fig. 16, the longest cross-sectional dimension is preferably aligned with the axis of the tubulation and this tends to push a considerable amount of displaced material ahead of the sealing member 4611.

It is also possible to pass the sealing member through the heated tubulation in a direction Which is generally oblique to the plane of the cross-section of the tubulation and such a direction of passage is indicated in Fig. 16, with the resulting tipped-oil? tubulation shown in Fig. 17. This has the advantage that the ratio of the amount of displaced tubulation material to the intersected area of the axial aperture within the tubulation is greater so that more displaced tubulation material is available to effect the tip-oif. In addition, the re-entr-y angle 56:: between the displaced tubulation material and the wall of the tubulation is quite large, thereby largely eliminating a possible weakness in the physical structure of the tubulation seal.

The temperature to which the sealing member 46 may be heated and the pressures applied to this sealing member in effecting the tip-elf may vary over a wide range depending upon conditions of operation such as the type of glass, the size of the tubulation, the internal pressures within the tubulation and whether or not a preheating technique is used, for example. The most difiicult tip off to perform is one wherein the exhaust tubulation is at a pressure greater than atmospheric. Extensive experiments have been conducted tipping off a lead-glass-type of soft-glass tubulation having an outside diameter of about 0.114" with an average wall thickness of about 0.027". The tipping operation was performed with 0.064", 0.040" and 0.036" diameter Nichrome V Wire and additional tests were carried out using 0.034"

Nichrome v strip cut to a width of 0.104". Nichrome V wire is a trademark of Driver-Harris Co. and consists of nickel and 20% chromium. In these tests, the tubulation was filled to an internal pressure of fifteen pounds above atmospheric and the temperature of the sealing member varied from 850 C. to 1000 C. Under these conditions of operation, the sealing member 46 was placed next to the tubulation in order to preheat the tubulation portions contiguous with the sealing member. After a preheat time of thirty seconds, for example, the temperature of the sealing member was lowered slightly to from 850 C. to 950 C. and the heated member forced through the tubulation using pressures which varied from sixteen to sixty ounces. The actual tipping times under these conditions of operation varied from nine to fifteen seconds and the actual stress between the tipping member and the heated tubulation varied from 173 lbs. per sq. inch to 260 lbs. per sq. inch depending on the pressure which was applied to the sealing member and the sealing member diameter. Under these conditions of tipping, the minimum thickness of the formed continuous layer of tubulation material varied between 0.0004 and 0.0026 inch. As a specific example, with a 0.040 diameter sealing member and a tubulation internal pressure of fifteen p.s.i., a member preheat temperature of 975 C. may be used to preheat the tubulation portions contiguous with the wire. After this, the sealing member temperature may be dropped to 900 C. and the sealing member forced through the tubulation to effect the seal in about ten seconds. Under these conditions of operation, the pressure applied to the sealing member may be twenty-four ounces with a resultant stress between the sealing member and the tubulation of 260 lbs. per sq. inch. This will produce a tubulation hermetic seal having a minimum thickness of about 0.0006". It should be understood that the foregoing conditions of operation are only given as a specific example and may be varied considerably.

It is also possible to tip a hard-glass tubulation and extensive experiments were conducted on a borosilicate glass tubing sold under the Corning Glass Works trademark Nonex. This tubing had an outside diameter of about 0.162", an average wall thickness of about 0.040 and was maintained at a pressure of fifteen pounds above atmospheric, When tipping this hard glass, a somewhat higher temperature is required for the sealing member 46 and temperatures varying from 975 C. to 1350 C. were utilized. A pressure of about sixty ounces was applied to the member 46 which produced a stress between the sealing member and the tubulation of from to 605 pounds per sq. inch. The actual tipping operation, after a thirty second preheat, took from about 3.5 seconds to about six seconds.

Utilizing a preheat time of six seconds with a gas-air burner, hard-glass tips were made with a sealing-member temperature of from 975 C. to 1100 C. in as little as 2.4 seconds and the maximum tipping time required was 5.2 seconds. The actual stress applied between the sealing member 46 and the tubulation 32 during these tipping experiments utilizing the gas-air preheat varied from 195 lbs. per sq. inch to 605 lbs per sq. inch. It should be understood that any soft or hard glass may be substituted in place of the foregoing specific examples.

In the foregoing specific examples, the tubulation has been preheated before the actual tipping operation, either entirely by the heated sealing member, or by a gas-air burner or other heating means. It is also possible to effect a tubulation seal with no actual preheating of the tubulation by merely effecting a passage of the heated sealing member through the tubulation. This requires a slightly longer period to effect the actual seal since the tubulation must be heated by the heated sealing member as it passes therethrough. Such a technique is more practical with so-called hard or borosilicate glass since thermal shocks are minimized, although soft glass tubulations may be tipped by such a method.

aasaore As will be seen from the foregoing, the actual conditions of operation may vary within vary wide limits and satisfactory tips will still'result. As a general rule, as the sealing member diameter is decreased, the temperature that can be used to obtain satisfactory tips can be increased. With soft glass, the best temperatures for the sealing member were found to be from 850 C. to 950 C. With hard glass, the best temperatures for the sealing member were found to be rom 975 C. to 1275 C. Of course, the foregoing ranges may be extended considerably and good seals will still be obtained.

As noted hereinbefore, the average thickness for the hermetic seal of the tubulation is somewhat less than the wall thickness of the tubulation. in actual measurements, the minimum thickness of the seal has varied from about one seventy-fifth to about one-half of the tubulation wall thickness with the maximum thickness of the seal being only slightly less than the tubulation wall thickness. Such variations in'thickness of the hermetic seal are due to varying speeds of tipping, crss-sectional dimensions of the sealing member, varying tipping temperatures, types of glass and other variables in the process.

In Fi 18 is shown an electronic tube 58 which is completed except for the exhaust and a tip-oil operation. Where space limitations constitute a problem, it is often desirable to make this tip flush with the envelope al- 7 though under the usual tip-off practices, this is not practical without incurring the risk of damaging the envelope. With the instant method, however, a flush-type tip is entirely practical and such an operation is shown in Fig. 18, with the completed tip shown in Fig. 19. In such electronic tubes, the tubulation often forms a continuation of the envelope proper and as is usual, generally comprises a vitreous conduit having walls which define a centrally-disposed aperture along the axis of the conduit. When tip-oil is made at a point proximate the connection of the tubulation or conduit and the envelope, this will result in a thin layer of tubulation material which is disposed generally-transversely to the axis of the tubulation and continuous with the walls thereof, as shown in Fig. 19. Of course, the tip-off could be made at an angle oblique to the plane of the cross-section of the tubulation, if desired.

in Fig. is shown another embodiment wherein the tubulation for a fluorescent lamp 64? has been tipped oil so that the tip-ofi is within the recess formed by the furthermost-projecting portions of the lamp envelope. In this manner, any interference with the base cap which is later provided on the fluorescent lamp is eliminated and sealing-fire splash as is encountered in the general practices of the prior art is also eliminated.

One unusual feature about the instant method is that the tubulations which are to be hermetically sealed are not limited in size or shape. As an example, a glass tubing having an outside diameter of inch and an average wall thickness of /8 inch has been tippedoff by the hotsealing-member technique disclosed herein. Tipping off this size of tubulation is not practical with the practices of the prior art. Also, while specific examples have been given for tipping a tubulation having an internal pressure of fifteen pounds per sq. inch, the tipping operation is equally effective with considerably higher internal pressures, with atmospheric pressures within the tubulation or with vacuum conditions within the tubulation. There appear to be no practical limitations to the pressures within the tubulation which can be tipped with the techniques disclosed herein and three or four atmospheres, for example, can be readily tipped.

As a further alternative embodiment, the tubulationsealing apparatus shown hereinbefore may be dispensed with and the tipping operation carried out by hand by manually forcing a heated sealing member through the tubulation to be sealed. Alternatively, the tubulation to be sealed may be moved against the heated sealing memher so as to effect a relativemovement between the heated c) f" and der pressure or vacuum conditions with substantially any type of vitreous material and with any practical size or configuration for the tubulation.

While in accordance with the patent statutes, one besthnown embodiment of the invention has been illustrated.

and described in detail, it is to be particularly understood that the invention is not'limited thereto or thereby.

We claim:

l. The method of hermetically sealing 'a hollow vitreous conduit with an elongated sealing member, which method comprises, heating said sealing member to a predetermined temperaturc, bringing said sealing member and said conduit into contiguous relationship, heating by means of said scaling member that portion of said conduit contiguous with said sealing member to a predetermined temperature sufficiently high to enable said heated conduit portion to be deformed by the stress resulting from an externally applied force but sufliciently low to enable said heated conduit portion to resist substantial deformationunder any stress exerted by any gaseous forces acting thereon, applying between said heated sealing member and said heated conduit portion such force as required to effect therebetween a stress sufficient to produce a substantial deformation of said heated conduit portion, causing controlled sealing member passage across said conduit by controllirn the temperatures of said sealing member and said heated conduit portion and the stress applied therebetween to displace a portion of said conduit and form a continuous layer of displaced conduit material continuous with adjacent undisplaced conduit portions, and continuing to effect such controlled sealing member passage across said conduit until said conduit has been at least substantially intersected and the resulting formed continuous layer of displaced conduit material is continuous with undisplaced conduit portions adjacent the path of said sealing member thcreacross, whereby said conduit is hermetically sealed.

2. The method of hermetically sealing a hollow vitreous conduit with an elongated sealing member, which method comprises, electrically heating said sealing memher to a predetermined temperature preheating at least that conduit portion which is to be sealed to a predetermined temperature somewhat below the softening temperature of the vitreous material comprising said con duit, moving said sealing member into contiguous relationship with said heated conduit portion, further heating by means of said sealing member that portion of said conduit contiguous with said sealing member to a predetermined tcmperature sufiiciently high to enable such heated conduit portion to be deformed by a stress resulting from an externally applied force but sufficiently low to enable such heated conduit portion to resist substantial deformation under stress of any gaseous forces acting thereon, applying to said heated sealing member such force as required to effect on said heated conduit portion a stress sufiicient to produce a substantial deformation of said heated conduit portion, causing controlled sealing member passage across said heated conduit portion by'controlling the temperatures of said sealing member and said heated conduit portion and the stress applied therebetween to displace a portion of said conduit and form a continuous layer of displaced conduit material continuous with adjacent undisplac-ed conduit portions, and continuing to effect such controlled sealing mcmberpassage across said conduit until saidcondu t has been completely intersected and the resulting formed continuous layer of displaced conduit material is continuous with undisplaced conduit portions adjacent the path of the passage of said sealing member thereacross, whereby said conduit is hermetically sealed.

3. The method as specified in claim 1, wherein controlled sealing member passage across said conduit is continued until said sealing member has completely intersected said conduit.

4. The method as specified in claim 1, wherein said sealing member is initially moved into contiguous relationship with said conduit, and the predetermined force applied between said heated sealing member and said heated conduit portion, to produce a substantial deformation in said conduit, is applied to said heated sealing member to move same against said conduit.

5. The method as specified in claim 1, wherein sealing member passage across said conduit is generally transverse to the axis of said conduit.

6. The method as specified in claim 1, wherein said conduit encloses a partial vacuum.

7. The method as specified in claim 1, wherein said conduit encloses gas under greater-than-atmospheric pressure.

8. The method as specified in claim 1, wherein said sealing member is metallic.

9. The method as specified in claim 8, wherein said sealing member is electrically heated.

10. The method of hermetically sealing with a wire metallic sealing member a soft glass tubular conduit containing an internal gas pressure of p.s.i. gauge and having an outside diameter of about 0.114 inch and an average wall thickness of about 0.027 inch, said wire sealing member having a diameter of from 0.036 inch to 0.064 inch, which method comprises, electrically heating said sealing member to a temperature of from 850 C. to 1,000 C., moving'said heated sealing member in a direction generally transverse to the axis of said conduit so that said heated sealing member contacts said conduit, maintaining said sealing member in contacting relationship with said conduit for 30 seconds, adjusting the temperature of said sealing member to from 850 C. to 950 C., applying a force of from 16 to ounces against said sealing member to exert a stress between said sealing member and said heated conduit of from 173 pounds per square inch to 260 pounds per square inch, and maintaining the foregoing stress between said sealing member and said conduit for a period of from 9 to 15 seconds while maintaining the temperature of said sealing member at from 850 C. to 950 C., whereby said conduit is hermetically sealed.

References Cited in the file of this patent UNITED STATES PATENTS 787,428 Blackburn Apr. 18, 1905 2,014,471 DeNeumann Sept. 17, 1935 2,273,441 Gustin Feb. 17, 1942 2,442,608 Lemmens June 1, 1948 2,464,765 Palmer Mar. 15, 1949 2,561,838 Bechard July 24, 1951 FOREIGN PATENTS 822,713 Germany Nov. 26, 1951

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