US2123015A

US2123015A - Seal for discharge lamps

Info

Publication number: US2123015A
Application number: US72048A
Authority: US
Inventors: Marden John Wesley; Meister George
Original assignee: Westinghouse Electric Corp
Current assignee: Westinghouse Electric Corp
Priority date: 1936-04-01
Filing date: 1936-04-01
Publication date: 1938-07-05
Anticipated expiration: 1955-07-05

Description

July 5, 1938. J. w. MARDEN ET AL 2,123,015

SEAL FOR DISCHARGE LAMPS Filed April 1, 1936 INVENTOR J 14/. MJFDf/V 6'. NE/Ji' F.

ATTORNE Patented July '15, 1938 UNITED STATES PATENT OFFICE- SEAL FOR DISCHARGE LAMPS John Wesley Marden, East Orange, and George Meister, Newark, N. J., assignors, by mesne assignments, to Westinghouse Electric and Manufacturing Company, East Pittsburgh, Pa... a corporation of Pennsylvania Application April 1, 1936, Serial No. 72,048

5 Claims.

Our present invention relates to seals for electric apparatus and particularly electric discharge apparatus wherein a discharge occurs between two electrodes in a gaseous atmosphere under comparatively high pressure. In the prior art various types of seals have been employed wherein the leading-in conductors for supplying the electrical energy to the electrodes or filament within the envelope are sealed through the Vitreous envelope. Moreover the problem of providing a seal such that the coemcient of expansion of the metallic leading-in conductor approximates that of the vitreous envelope so as to pre-- vent cracking of the seal with attendant loss of the vacuum or gaseous medium has long been recognized.

The customary construction has been to provide the leading-in conductor with a section of a metal having an analogous co-emcient of expansion to that of the vitreous envelope with the remainder of the leading-in conductor being of a less expensive metal or of a refractory metal capable of withstanding high temperatures due to heating of the electrode or filament. However, with such construction that portion of the leading-in conductor having the desired, co-eificient of expansion has limited to a considerable extent the current carrying capacity of the leading-in conductor.

In instances where the electric discharge device comprises a vitreous envelope provided with oppositely disposed electrodes between which a discharge occurs the electrodes are either heated to a thermionic emission from an exterior source or the electrodes are thermionically' heated by the discharge occurring between theeIectrodes upon the application of electrical energy thereto.

In addition the envelope is usually provided with a gaseous medium comprising a metallic vapor, such for example as sodium, cadmium, mercury or the like at a substantial pressure ranging from a few millimeters of mercury to several atmospheres. Moreover as the pressure of the gaseous medium normally increases with increase of temperature the provision of a suitable seal for the leading-in conductors presents an even more momentous problem than is present with the usual incandescent lamp or electric device utilizing a vacuum.

We have previously shown and described in our copending application Serial No. 49,448, filed November 13, 1935, that the maximum efllciency of a high pressure mercury vapor lamp is dependent on the maximum wattage per centimeter of arc length. In order to obtain maximum efficiency comparatively high currents must be impressed upon the electrodes which necessitates leading-in conductors for the device not only capable of carrying the necessary currents, but in additional such character as to form a perfect,

seal so that the high temperatures of operation of the device will not destroy the seal formed at the juncture of the leading-in conductors for the electrodes with the vitreous envelope.

It is accordingly an object of our present invention to provide a novel seal for electric devices particularly of the high pressure type employing a gaseous medium wherein the leading in conductor forms an integral seal with the vitreous envelope of the device which will not be detrimentally aliected by the high temperatures of operation of the device nor by the high pressure of the gaseous medium contained within the envelope.

Another object of our present invention is the provision of a seal for a vitreous envelope or container wherein the leading in conductor is sealed to the envelope in such manner as to provide an integral seal capable of withstanding the high temperatures and pressures of operation of the device and of carrying the requisite electrical currents during operation.

Another object of our present invention is the provision of a seal for a vitreous envelope or container wherein the leading in conductor is provided with a portion formed of thin metal having a high melting point and due to its crosssectional area forms an integral seal with the envelope without the necessity of the seal forming portion being of the same coefficient of expansion as that of the envelope.

Still further objects of our present invention will become readily apparentto those skilled in the art by reference to the accompanying drawing wherein,

Figure l is a fragmentary view in cross-section of an electric discharge device particularly of the high pressure metal vapor type provided with a seal constructed in accordance with our present invention.

Figure 2 is an enlarged cross-sectional view taken on the line 11-11 of Fig. 1.

Figure 3 is a perspective view on an enlarged scale of a seal for electric discharge devices 0011- employing seals in accordance with the teachings of our present invention.

Referring now to the drawing in detail we have shown in Fig. l a vitreous envelope I constructed of hard glass, silica, or the like, but in instances where the device is of the metallic vapor type which is subjectable to high temperatures of operation it is preferable to construct the container or envelope I of quartz due to its high melting point. The envelope I is provided with a tubular extension I formed thereon during the sealingin process and embedded in the tubular portion is a leading-in conductor forming an integral seal with the tubular extension portion of the vitreous container or envelope. The construction of this leading-in conductor may be better appreciated by particular reference to Fig. 3 wherein the leading-in conductor comprises a substantially cylindrical member 'I. This member may be formed of any suitable thin metal, such as tungsten, tantalum, but preferably molybdenum foil of about 1 mil thickness. This metal is formed into the configuration of a cylinder by rolling and joining the overlapping ends and securing the same in any suitable manner, such as by welding I.

The cylindrical metallic foil member I is provided with a longitudinal slot 9 for a purpose to be hereinafter more fully described and connected to this member 1 in any suitable manner, such as by welding, is an electrode III of suitable refractory metal, such as tungsten, which may be provided with an additional refractory metal layer of coiled tungsten I2 with this portion being subjected to the discharge between the oppositely disposed electrodes during operation of the device.

Also connected to the cylindrical metallic foil portion is a rod like portion or wire II which may be formed of substantially U-shaped configuration having its ends secured as by welding to the metallic foil portion with the remaining portion of the wire II joined in a similar manner to the base of the U-shaped portion and constituting that portion of the leading in conductor adapted to be disposed exteriorly of the container or envelope I asshown more clearly in Fig. 1. Prior to connection of the exteriorly disposed portion II of the leading in conductor a core of vitreous material ll of the same composition as that of the vitreous envelope I is inserted in the cylindrical metallic foil portion I of the leading in conductor thus conditioning the same for sealing in to the envelope of the discharge device. This latter step may be accomplished in any suitable manner, but we find it expedient to employ the method and apparatus shown more particularly in Fig. 4.

As the spacing between the electrodes of a discharge lamp of the metal vapor type is an essen tial factor in its efficiency of operation we first join the envelope I to a suitable vitreous chamber II and provide the opposite end of the envelope with a tubular member II having an elbow or the like II.

The lower leading-in conductor as viewed from Fig. 4, together with its electrode and seal forming portion, as shown more particularly in Fig. 3, is then inserted into the chamber II while its upperend is open and such leading-in conductor slid downwardly of the chamber II and envelope I until the extremity of the leading-in conductor rests against the shoulder portion II thus accurately positioning the leading in conductor and electrode within the lower portion of the envelope I preparatory to the sealing in operation.

Next the upper leading in conductor together with its respective electrode and seal forming portion is inserted into the chamber lIand moved I downwardly of the chamber II until the upper electrode is positioned the desired distance from the lower electrode.

the upper electrode and leading-in conductor in this desired position.

The vacuum pump (not shown) which is connected to the chamber II is then operated to evacuate the envelope I and the lower portion of the envelope I is suitably heated by flames II until the envelope attains a suitable fusing temperature and at the same timethe vitreous core II- of the leading in conductor is also heated to the fusion pointresulting in complete fusion of the core II with the envelope I both above and below the cylindrical metallic foil portion I and also fusion of the core I l and envelope I occurs through the longitudinal opening I provided in the cylindrical metallic foil section I until complete fusion of the core II and envelope I results. thus completely embedding the leading-in conductOr and particularly the cylindrical metallic foil portion I in the tubular portion I formed on the envelope I'during the fusion to form a complete integral seal with the envelope.

After the desired degree of evacuation of the envelope I is obtained and the appropriate gaseous medium or vapor forming metal is introduced into the envelope I the flames I! are moved adjacent the upper seal forming portion where the same operation is performed to form the upper integral seal between the envelope I and the leading-in conductor particularly the cylindrical metallic foil portion 1. The envelope I and portions II of the leading-in conductor are then severed from the chamber II and tubular member II thus completing the device.

It thus becomes obvious to those skilled in the art that we have provided a leading-in conductor particularly adaptable to electric discharge devices subjectable to extremely high temperatures and pressures during operation wherein the leading-in conductor forms an integralseal with the vitreous envelope. Moreover, the seal forming portion being of comparatively thin metal or foil facilitates the radiation of heat which is generated by the resistivity thereof to the passage of the electric current thus obviating possibilities of cracking of the seal. While preferably the seal is formed of a metal having a coefllcient of expansion simulating that of the vitreous envelope it need not necessarily have such precise coemcient of expansion due to its being of comparatively thin cross section. In addition the area of cross-section of the cylindrical metallic foil portion of the leading-in conductor is such that the requisite electrical current can be readily supplied to the electrodes without danger of overheating.

Although we have shown and described one specific embodiment of our invention we do not desire to be limited thereto as various other modiflcations of the same may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

What is claimed:

1. The combination of a vitreous container, a conductor fused to a portion of said container comprising a cylinder of metal foil, a leadingin conductor secured to the wall of said cylinder and extending exteriorly of said container, and an electrode within said container having its The open end of the chamber II is then sealed as shown at II to thus hold ends connected to the periphery of said cylindrical conductor and extending a substantial distance on the surface thereof in the direction of the longitudinal axis of said cylinder to form a support for said electrode.

2. The combination of a discharge device provided with an envelope of vitreous material, leading-in conductors comprising substantially cylindrical members formed ofmetal foil having their interior and exterior surface fused to said envelope to form a seal, leading-in conductors secured to the wall of each of said cylindrical members and extending exteriorly of said envelope, and electrodes within said envelope between which a discharge occurs when supplied with electrical energy and subjectable to extremely high temperatures, each of said electrodes having its ends connected to the periphery of the respective cylindrical member and extending a substantial distance on the surface thereof in the direction of the longitudinal axis of said cylinder to form a support for each of said electrodes directly from said seals.

3. The combination of a discharge device provided with an elongated envelope of vitreous material, a leading-in conductor disposed at opposite ends of said elongated envelope comprising substantially a cylindrical member formed of metal foil having a core of the same vitreous material as said envelope to form a fused seal integral with the latter, a leading-in-conductor secured to the wall of said cylindrical member and extending exteriorly of said envelope, and an electrode disposed at each end of said envelope between which a discharge occurs and subjectable to extremely high temperatures, and each of said electrodes having their ends connected to the periphery of the respective cylindrical member and extending a substantial distance 0n the outer surface thereof in the direction of the longitudinal axis of said cylindrical member to form a support for each of said electrodes directly from said seal.

4. A current conducting seal for an electric stantial distance on the outer surface in the direction of the longitudinal axis of said cylindrical member, and a wire having a bifurcated end portion connected to the periphery of said cylindrical member and extending a substantial distance on the outer surface thereof and extending exteriorly of the envelope of said discharge device.

5. A current conducting seal for an electric discharge device having a vitreous envelope comprising a substantially cylindrical member of metal foil having a longitudinal slot therein and provided with a core of vitreous material of the same composition as the envelope of said discharge device and readily fusible with the latter to entirely surround the cylindrical member and form an integral vacuum tight seal, an electrode having its ends connected to the periphery of said cylindrical member and extending a substantial distance on the outer surface in the direction of the longitudinal axis of said cylindrical member, and a wire having a bifurcated end portion connected to the periphery of said cylindrical member and extending a substantial distance on the outer surface thereof, and the remaining portion of said Wire being coaxially disposed relative to the longitudinal axis of said cylindrical member and extending exteriorly of the envelope of said device.

JOHN WESLEY MARDEN. GEORGE MEIS'I'ER.