US2198007A - Electric lamp - Google Patents

Description

April 23, 1940.

C. W. GOULD ELECTRIC LAMP J. i .i aa m w Filed pril 8. 195a Patented Apr.-

PATENT orrlcs mo'nnc mm.

Clarence -W. Gould, Waltbam, Mass assignor, by mesne assignments, to Birdseye Electric Corporation, Gloucester, Mass a corporation of Massachusetts Application April 8, 193 8, Serial No. 200,882.

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This invention relates to electric lamps and consists in a lamp having an exhaust tube communicating with the interior of its bulb and provided with a metallic sealing portion.

Gas-filled lamps as heretofore manufactured have generally been sealed with their gaseous content under less than atmospheric pressure and no difllculty has been experienced in employing the conventional exhaust tube or stem of glass or in sealing such a tube. in manufacturing lamps of that kind on a commercial scale. -It has been appreciated for some time, however, that the luminous eiilciency of electric lamps may be increased by sealing their gaseous content under more than atmospheric pressure, for example, under, 'a pressure of l atmospheres or from 900 to 1000 mm. of mercury. It is impractical to employ an exhausting and filling tube of glass under conditions of internal pressure because a glass tube tends to blow out when soft ened for seating. ,The attempt has been made to overcome his diiflculty by enclosing the usual glass exhausting tube within a pressure chamber while sealing it with a flame, in thisway equalizing the pressure inside and outside the tube while the glass is in softened condition. This expedient is not satisfactory however, in that it involves elaborate apparatus and seriously slows down the rate of manufacturing production.

The object of the present invention is to overcome the difllculties abovediscussed and to provide a simple and effective structure by which the bulbs of lamps gas filled at more than atmospheric pressure may be sealed securely and rapidly under commercial conditions of manufacture. To this end an important feature of the invention consists in an electric lamp bulb providedwith a tube having a metallic sealing portion therein. The exact construction employed is a matter of secondary importance. A thin metal tube may be sealed in the press of the mount or into the hollow flare, or a short metal tube may be united to a glass stem which is itself sealed either into the flare or the press. An advantage of sealing the tube into the press is that in this location it may be utilized as one of the lead connections to the filament or to an electrode in the bulb. In any case it is desirable to insulate the tube within the bulb to avoid danger of shortcircuiting between the lead connections and another feature of the invention consists in a lamp bulb provided with a tube having a metal sealing portion and being protected by suitable insulation from the lead wires of the lamp.

A-thin copper tube issuitable for purposes of (cl. lie-s5) this invention since it may be heated to a sealing temperature without vreducing its strength to a point where it will be distorted by internal pressure. Other metals may be used and due r'egard must be paid to the matter of selecting a I metal or so treating it as to i'nsure perfect union with the glass of the press or of the flare. In sealing a thin copper tube it is practicable ,to heat it, compressing its side walls and spot-welding or soldering them together in a gas-tight l0 joint and having thus sealed the tube, its end may be trimmed off preparatory to the basing operation.

. These and other features of the invention will be best understoodand appreciated from the following description of several preferred embodiments thereof selected for purposes of illustra- --tion and shown in the accompanying drawing in which,

Fig. 1 is a fragmentary view in cross section "of an incandescent electric lamp bulb in process of being sealed,

Fig. 2 is a fragmentary view in cross section showing the tube as sealed and insulated,

Figs. 3, 4 and 5 are views illustrating alternative forms of exhaust tube, and

Fig. 6 is a fragmentary view of a bulb in which the metal exhaust tube is utilized also as a leadin connection. 1 g

The bulb i0 shown in Fig. l is of a type conventionally employed in incandescent electric lamps and has a hollow mount or flare H sealed into its neck. The flare terminates in a press I! into which are sealed the lead and supporting wires it which carry the fllament II at the proper ll location within the bulb. As shown in Fig. l a metal tube I! of small diameter extends axially into the flare Ii being curved at its inner end and sealed in the inner end of the flare so that it opens into the interior of the bulb. The tube do I! may be of thin copper or of other metal or alloy suitable for sealing to glass. One -satisfactory method of forming a union between the metal tube It and the glass flare II is disclosed in U. S. Letters Patent No. 2,035,015, granted March 24, 1936 on an application of R. E. Schirmer to which reference may be had for de tails of procedure.

It will be understood that the function of the metal tube II is first to exhaust the bulb Ill so and then flll it with argon or other inert gases or gas mixtures under greater than atmospheric pressure. Having thus fllled the bulb, the tube It is sealed under pressure. The metal walls ofthetubeareadaptedtobeheatedtoafusingll or soldering temperature without belnfweakened sufllciently to be distorted by any, pressure desired within the bulb. One satisfactory procedureiorsealingthetube liissuggestedinl'lgl where cooperating laws It and II are shown as mounted for clamping movement adjacent to the end of the neck of the bulb and as connected in electric circuit through which a current may be supplied for spot-welding the collapsed walls of the tube, and so forming an effective gastight seal therein. The inner walls of the tube I! may be tinned if desired and the seal eflected by soldering if preferred. At the completion of the sealing step the end of thetube may be severed by cooperating cutters It and the sealed bulb is then ready for the basing operation.

In Fig. 2 the end of the tube I 5 is shown as sealed in the manner suggested in Fig. 1. The sealed tube is provided with an insulating sleeve IQ of woven asbestos or the like by which it is eifectively insulated from the lead wires 13 which pass downwardly from the flare II.

In Fig. 6 I have shown an alternative construction in which a small metal tube 22 is sealed in the press i2 instead of in the walls of the flare II as in Fig. 1. p In this construction it is practicable to utilize the metallic tube 22 as one of the lead connections to the filament or to an electrode or other terminal within the bulb. Accordingly one lead wire 2| is shown as passing through the press I! and the flare ll, while the other lead wire 23 is connected to the inner end of the metal tube 22 and then continued again beyond the outer sealedend oi the tube. The metal tube 22 is shown as provided with an insulating sleeve 20 to prevent any danger of short-circuiting between it and the lead wire 2!.

In Figs. 1, 2 and 6 I have shown the bulb as equipped with an integral metal tube, but it is within the scope of the invention to employ an exhausting or filling tube having a metal sealing portion and being formed in part of other material, such as glass. In Figs. 3-5 are illustrated composite tubes oi this character which may be substituted in place of the integral tubes shown in Figs. 1, 2 or 6. In Fig. 3 the tube has its upper end 25 formed of glass and so curved that it may be sealed into the inner end of the flare. The glass end 2| is telescopically united with a metal tube or sleeve 28 and extends out from the flare of the bulb in position to be sealed by welding or soldering as already explained. In Fig. 2 the tube comprises an upper glass end portion 21 and a metal tube 28. The lower end of the glass portion is flared and united by a butt weld to the metal section 2|. In Fig. 5 the curved glass end is united to the metal tube II which may be copper in this instance and may have the thickness of its walls tapered or reduced so as to reduce the area of contact to a minimum. This is advisable where there is any difl'erence between the coeiflcient of expansion of the metal employed and 'the glass. In most instances it v is advisable to employ a metal such as Kovar or other alloys of chromium, iron and copper or nickel and iron which have the same coeflicient. of expansion as the glass used in the flare.

Having thus disclosed my invention and-shown preferred embodiments thereoi for purposes of illustration but not in any limiting sense, I claim as new and desire to secure by Letters Patent:

. 1. An electric lamp having a hollow flare terminating in a press, a glass tube sealed into the press, extending out through the open end of the flare and being provided with an outer metallic extension section in which is included a seal, and means for insulating the metallic section of the tube.

2. An electric lamp having a bulb with a hollow flare terminating in a press, lead wires within the flare, and a glass fllling and exhausting tube located partially within the flare and communi catingwith the interior of the bulb, said tube having at its outer end a metal section containing a seal and being insulated from said lead wires.

3. An electric lamp having a bulb provided with a hollow lntemal flare, a glass tube sealed in the flare and communicating with the interiorof the bulb, and a metallic section secured to the outer end of said glass tube and serving as a longitudinal extension thereof and in which is included a seal spaced beyond the end of the a glass tube.

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