US3249781A

US3249781A - Single-ended jacketed arc lamp mounting

Info

Publication number: US3249781A
Application number: US191207A
Authority: US
Inventors: Leon J Smialek; Clarence G Cook
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1962-04-30
Filing date: 1962-04-30
Publication date: 1966-05-03
Anticipated expiration: 1983-05-03

Description

May 3, 1966 L. J. SMIALEK ETAL SINGLE-ENDED JACKETED ARC LAMP MOUNTING Filed April 30, 1962 ITWVTWTOTSI Leon d. Smiatek Ctaven 6 .Cook by J Their" A t tow-neg United States. Patent 3,249,781 SINGLE-ENDED JAQKETED ARC LAMP MOUNTING Leon J. Smialek, Chagrin Falls, and Clarence G. Cook, East Cleveland, Ohio, assignors to General Electric Company, a corporation of New York Filed Apr. 30, 1962, Ser. No. 191,207 7 Claims. (Cl. 31325) The invention relates to an elongated single-ended jacketed arc lamp having a base at one end only for engagement in a socket. The invention is more particularly concerned with the mount within the jacketed assembly for supporting the arc tube within the jacket and for making electrical connections to its electrodes.

The light source proper of the present lamp is a high pressure mercury vapor arc lamp in the form of anelongated quartz tube having a length many times greater than its diameter with electrode inleads sealed into opposite ends. These lamps are efiicient sources of ultraviolet radiation and are used extensively in photochemical applications. They may also be used for general illumination when suitable glass shields are provided for cutting out the ultraviolet radiation which is harmful to the eyes.

In order to. prevent oxidation of the inleads of the quartz arc tube, it is mounted within an outer glass jacket which is then evacuated or filled with a neutral gas. With tubes of great length, and by such is meant an arc tube having a length 20 or more times greater than its diameter, a double-ended jacket has generally been used. This is a jacket provided with terminals at both ends and wherein the arc' tube is supported at both ends. For certain applications however, such as in photochemical treatment of fluids where the lamp is suspended and hangs down in a fluid bath, a single-ended jacket is necessary.

The problems involved in mounting an arc tube of great length in a single-ended jacket and in making electrical connections from the jacket base to the arc tube terminals are considerable, and the object of the invention is to provide a convenient and practical means for so doing.

More specific objects and corresponding features desired in the mounting arrangement according to the invention are ruggedness with sufiicient flexibility to absorb shock or vibration, ease of assembly and adjustability for normal variations in arc tube and jacket length.

In accordance with our invention, the arc tube is supported within the jacket between a pair of apertured end plates which engage and are caused to press against the shoulders of the arc tube about the seals of the inleads by means of a pair of side rods running the full length of the arc tube or chamber and maintained 'under spring tension. One of these rods is used as the current carrying conductor to the arc tube inlead at the far end of the jacket and the two together result in a balanced structure which remains aligned under tension. During operation of the lamp, the heat therefrom causes the rods to expand and lengthen but the springs which keep them under tension take up the increase in length so that the arc tube remains firmly and securely mounted at all times.

Other objects of the invention and further features and advantages thereof will be apparent from the description hereinafter following and from the accompanying draw ing illustrating a preferred embodiment. The features of the invention believed to be novel will be more particularly pointed out in the appended claims.

' In the drawing:

FIG. 1 is a full side view of a high pressure singleended mercury vapor arc lamp of great length embodying the invention.

"ice

FIG. 2 is a side view, partly sectioned but foreshortened and to a larger scale, of the same lamp.

FIG. 3 is an exploded pictorial view showing fragments of the same lamp. at the levels of the arc tube shoulders and at an intermediate point.

Referring to the drawing and more particularly to FIGS. 1 and 2, the illustrated lamp 1 comprises an inner arc tube 2 coaxially mounted within an outer envelope or jacket 3. The arc tube is a cylindrical quartz tube filled with an inert gas-such as argon at a low pressure, for instance 25 millimeters of mercury, and a quantity of mercury sufficient when vaporized to develop a vapor pressure in the range of 1 to 10 atmospheres, for instance 2 to 4 atmospheres, the mercury being indicated by the droplet 4. At each end of the lamp there is provided a thermionic electrode5 mounted on a support rod 6 and to which current connections are made through an inlead which extends through a generally cylindrical axially projecting quartz seal body 7. Each inlead comprises a thin metal foil portion 8, commonly made of molybdenum, with a short rod-like portion 9 emerging from the end of the seal body. The central portion of the inlead is Very thin, for instance less than 1 mil in thickness, so that it yields under tension to the quartz during cooling and does not rupture nor crack the quartz, thereby preserving a hermetic seal. The illustrated seal is generally known as a vacuum seal because vacuum is used to collapse the originally hollow quartz seal body 7 onto the inlead 8 passing therethrough while the quartz is heated to softening temperature. Other seal constructions may of course be used.

The outer envelope or jacket 3 consists of a hard glass such as a borosilicate glass and is generally tubular with a rounded or hemispherical closure 11 at its lower or far end. The upper or near end of the jacket is necked down at 12 and is closed by a cup-shaped closure member 13 which is termed a bipost flare. The bipost flare is made as a separate assembly and comprises a shallow cup-like member 14 of hard borosilicate glass provided with a central exhaust tube 15 (shown tipped off) and a pair of outwardly projecting teat-like extensions 16. A pair of hollow copper pins or posts 17 are sealed peripherally into the extensions 16, whence the name bipost flare. The posts 17 are closed at the outer end and are enlarged at the inner end with a feathered edge 18 which is sealed to the flare by embedding it in the lip of the projecting teat 16. Due to the thinness of the metal at the edges of the post body where it is sealed to the glass, a hermetic joint is achieved which can withstand substantial temperature variations. The inter-envelope space between the arc tube and outer jacket is either evacuated or, preferably, is filled with a nonoxidizing gas such as nitrogen at a pressure, for instance, of 200 millimeters of mercury.

Mechanical support for and electrical connections to the arc tube from the posts 17 are provided by a pair of support rods 20, channel-shaped in cross section. The rods are suitably fastened within the hollow posts and extend inwardly into the jacket. The arc tube is located between a pair of

end plates

21, 22, each plate having a central aperture therethrough which bears against the shoulder 23 of the arc tube about the seal body 7. The plates are drawn together by means of long tie rods which extend the length. of the arc tube, the tie rods being fastened into the ends of the support rods 20 in suitable fashion, as by welding or by crimping the latter. One tie rod 24 (on the left side) is continuous and provides a circuit connection from one of the posts 17 to the electrode at the far end of the arc tube by means of a flexible jumper or strap 25. The other tie rod is in two parts: 26a, 26b which are mechanically joined together by a Patented May 3, 1966 V 3 ceramic insulator 27 but electrically insulated thereby one from the other. Part 26a which is fastened to one of the support rods 20 provides circuit continuity from the other post 17 to the electrode at the near end of the arc tube by means of a flexible strap or jumper 2%.

It is desirable to insulate the end plates electrically and thermally from the tie rods in order to avoid electrical stress and excessive cooling about the shoulders of the arc tube. To this end, end plate 21 is clampedbetween the mating parts 2%, 2% of ceramic insulators which are locked in place by nuts 30 engaging the threaded ends of the tie rods. These insulators are of the kind commonly known as feed-through insulators, and part 2% is provided with a neck which extends through an oversize hole in plate 21, thereby serving to insulate the plate from the rod in the usual fashion. The remote end plate 22 is engaged by similar feed-through insulator parts 3112 which make a sliding fit on the tie rods. The other insulator parts 31a are retained at the outer ends of the tie rods by means of locking nuts 32, and coil springs 33 located between the insulator parts cause end plate 22 to press resiliently against the end of the arc tube.

End plate 22 is provided with a loop or harp 34 consisting of a resilient U-shaped metal band which presses resiliently against the rounded end of the jacket and serves to relieve some of the strain on the posts 17 resulting from axial .shocks to the lamp in use or in handling. A springy transverse metal blade 35 is welded across the end of the harp and serves to maintain it centered in the end of the jacket. Both

end plates

21, 22 are furthermore provided with springy lateral metal blades 36 which are curved not quite to the radius of the jacket in order that their ends press resiliently against the jacket to maintain the plates axially centered. The

tie rods

24, 26b are provided with alignment rings 37 which are Welded to the tie rods at spaced points along their length. The rings have curved springy metal blades 38 welded to them on opposite sides and the ends of these blades bear against the jacket to maintain the assembly properly centered within the jacket. Although the alignment rings 37 provide electrical interconnection of the tie rods 24 and 2612, this does not create any problem because the short tie rod section 26a is insulated from the remainder.

The mounting arrangement which has been described achieves strength so that it does not distort under the weight of the arc tube and at the same time has sufiicient resiliency that the shocks encountered in shipping and handling or during operation will not damage the assembly. By reason of the coiled springs 33, the tie rods are maintained in tension and this is highly desirable to prevent distortion and twisting of the rods and mount assembly as the rods heat up during operation of the lamp. The are tube is maintained in compression wherein glass or quartz is strong. In tests performed without the springs 33 and wherein the

end plates

21, 22 were both rigidly attached to the tie rods, the tie rods expanded to the point where the arc tube was quite loose between the end plates and as a result of distortion and twisting of the side rods, they touched either the jacket or the arc tube wall in one or more places. With the coiled springs, the expansion of the rods is taken up by the springs and the rods remain perfectly straight and the entire assembly maintains its alignment.

As an example of a high power photochemical lamp actually constructed in accordance with the illustration of the drawings and successfully tested, the following data apply:

Electrical.l0,000 watts, 1400 volts 8.15 amperes (87.5% power factor).

Burning position.Vertical only immersed in fluid at 75 C. maximum temperature.

Jacket dimensi0ns.-71 A" overall length x 3" diameter.

Arc tube dimensi0ns.-59 /2" interelectrode distance x inch oute d ameter- The preferred embodiment of the inventionwhich has been described herein is intended by way of example and not in order to limit the invention thereto. The scope of the invention is to be determined by the appended claims.

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

1. A single-ended jacketed arc lamp of great length comprising an inner arc tube, a tubular light-transmitting jacket surrounding said arc tube closed at the far end, and a mounting structure supporting said are tube within said jacket comprising terminals sealed through the near end of said arc tube, a pair of tie rods extending on opposite sides of said are tube and fastened to said terminals, 9. pair of transverse end plates supported by said tie rods near opposite ends thereof, each plate engaging an end of the arc tube, one of said end plates being slidably mounted on said tie rods, and spring means urging the slidably mounted end plate against the arc tube so as to maintain the tie rods in tension and the arc tube in compression in spite of expansion of the tie rods from heat during operation of the lamp.

2. A single-ended jacketed arc lamp of great length comprising an inner arc tube, a tubular light-transmitting jacket surrounding said arc tube closed at the far end, and a mounting structure supporting said are tube within said jacket comprising terminals sealed through the near end of said are tube, a pair of tie rods extending on opposite sides of said are tube and fastened to said terminals, a pair of transverse end plates supported by said tie rods near opposite ends thereof, each plate engaging an end of the arc tube, the near end plate being fast to said tie rods, the far end plate being slidably mounted on said tie rods, and coil springs fastened to said tie rods and urging the slidably mounted end plate against the arc tube so as to maintain the tie rods in tension and the arc tube in compression in spite of expansion of the tie rods from heat during operation of the lamp.

3. A single-ended jacketed arc lamp of great length comprising an inner arc tube having electrode inleads at opposite ends, a tubular light-transmitting jacket surrounding said are tu-be closed at the far end, and a mounting structure supporting said are tube within said jacket comprising terminals sealed through the near end of said are tube, a pair of tie rods extending on opposite sides of said arc tube substantially its full length and fastened to said terminals, a pair of end plates supported by said tie rods near opposite ends thereof, each plate engaging an end of the arc tube, one of said end plates being slidably mounted on said tie rods, spring means urging the slidably mounted end plate against the are tube so as to maintain the tie rods in tension and the arc tube in compression in spite of expansion of the tie rods from heat during operation of the lamp, a connection from the electrode inlead at the far end of the arc tube to one of said tie rods, an insulator interposed in the other of said tie rods, and a connection from the electrode inlead at the near end of said are tube to the portion of said other tie rod between the jacket terminal and said insulator.

4. A single-ended jacketed are lamp of great length comprising an inner arc tube having projecting seal bodies at opposite ends, a tubular light-transmitting jacket surrounding said arc tube closed at the far end, and a mounting structure supporting said are tube within said jacket comprising a pair of terminals sea-led through the near end of said jacket, a pair of tie rods extending on opposite sides of said are tube substantially its full length and fastened to said terminal-s, a pair of end plates supported by said tie rods near opposite ends there- 'of, each plate having a central aperture therethrough and the seal bodies of the arc tube being passed through said apertures with the rim of the aperture bearing against the shoulder of the arc tube, one of said end plates being fast to the tie rods, the other of said end plates being slidably mounted on said tie rods, and spring means urging the slidably mounted end plate against the arc tube so as to maintain the tie rods in tension and the arc tube in compression in spite of expansion of the tie rods from heat during operation of the lamp.

5. A single-ended jacketed arc lamp of great length comprising an inner arc tube having projecting seal bodies at opposite ends, a tubular light-transmitting jacket surrounding said are tube closed at the far end, and a mounting structure supporting said are tube within said jacket comprising a closure member at the near end of said jacket having terminals sealed therethrough, a pair of support rods extending axially inwards from said terminals, and a pair of tie rods extending on opposite sides of said are tube substantially its full length, said tie rods being fastened to said support rods at ne end, a pair of transverse end plates supported on said tie rods near opposite ends thereof, each plate having a central aperture therethrough and the seal bodies of the arc tube being passed through said apertures with the rim of the aperture bearing against the shoulder of the arc tube, the near end plate being fast to the tie rods, the far end plate being slidably mounted on said tie rods, coil springs fastened to the tie rods and urging the slidably mounted end plate against the arc tube so as to maintain the tie rods in tension and the arc tube in compression in spite of expansion of the tie rods from heat during operation of the lamp, and lateral spring blades attached to said end plates and bearing against the walls of said jacket to maintain said end plates centered within said jacket.

6. A single-ended jacketed arc lamp of great length comprising an elongated inner arc tube having axially projecting seal bodies at opposite ends with inleads passing there-through, said seal bodies extending beyond shoulders of the arc tube, a tubular vitreous jacket surrounding said are tube closed at its far end, and a mounting structure coaxially supporting said are tube within said jacket, said mounting structure comprising a vitreous closure of said jacket at the near end of said lamp, a pair of hollow post terminals sealed into said closure member and projecting axially therefrom, support rods fastened into said terminals and extending axially inwards therefrom, a pair of tie rods on either side of said are tube extending substantially its full length, said tie rods being fastened into said support rods at one end, a pair of end plates supported by said tie rod-s each having a central aperture there-through through which the seal body of the arc tube extends with the rim of the aperture bearing against the shoulder of the arc tube, the near end plate being fast to the tie rods but insulated therefrom-the far end plate being slidably mounted on the tie rods and likewise insulated therefrom, each tie rod having a coil spring compressed between retaining means therefor on the far end of the tie rod and the slidable end plate, said coil springs serving to keep the tie rods under tension and the arc tube compressed between said end plates, spring blades attached to said end plates and bearing against the Walls of the jacket to maintain the end plates centered, and alignment rings spaced longitudinally along the tie rods with flexible blades bearingagainst the inner walls of the jacket to maintain the assembly in alignment.

7. A single-ended jacketed arc lamp of great length comprising an elongated inner arc tube having axially projecting seal bodies at opposite ends with inleads passing therethrough, said seal bodies extending beyond shoulders of the are tube, a tubular vitreous jacket surrounding said are tube closed at its far end and a mounting structure coaxially supporting said are tube within said jacket, said mounting structure comprising a vitreous closure for said jacket at the near end of said lamp, a pair of hollow post terminals sealed into said closure member and projecting axially therefrom, support rods fastened into said terminals and extending axially inwards therefrom, a pair of tie rods on either side of said are tube extending substantially its full length, said tie rods being fastened into said support rods at one end, a pair of end plates supported by'said tie rods each having a central aperture therethrough through which the seal body of the arc tube extends with the rim of the aperture bearing againstthe shoulder of the arc tube, the near end plate being fast to the tie rods but insulated therefrom, the far end plate being slidably mounted on the tie rods and likewise insulated therefrom, each tie rod having a coil spring compressed between retaining means therefor on the far end of the tie rod and the slidable end plate, said coil springs serving to keep the tie rods under tension and the arc tube compressed between said end plates, a flexible connector between the far end of one tie rod and the inlead at the far end of the arc tube, the other tie rod being interrupted at a place close to said near end plate by an insulator mechanically interconnecting the two parts, a flexible lead inter-connecting the near part of said other tie rod and the inlead at the near end of the arc tube, spring blades attached to said end plates and bearing against the Walls of the jacket to maintain the end plates centered, and alignment rings spaced longitudinally along the tie rods with flexible blades bearing against the inner walls of the jacket to maintain the assembly in alignment.

References Cited by the Examiner UNITED STATES PATENTS 2,385,435 9/1945 Werner et a1. 313278 2,458,218 1/1949 Skehan 313278 X 2,671,183 3/1954 St. Louis et al. 313-25 X GEORGE N. WESTBY, Primary Examiner.

ARTHUR GAUSS, Examiner.

C. R. CAMP-BELL, Assistant Examiner.

Claims

1. A SINGLE-ENDED JACKETED ARC LAMP OF GREAT LENGTH COMPRISING AN INNER ARC TUBE, A TUBULAR LIGHT-TRANSMITTING JACKET SURROUNDING SAID ARC TUBE CLOSED AT THE FAR END, AND A MOUNTING STRUCTURE SUPPORTING SAID ARC TUBE WITHIN SAID JACKET COMPRISING TERMINALS SEALED THROUGH THE NEAR END OF SAID ARC TUBE, A PAIR OF TIE RODS EXTENDING ON OPPOSITE SIDES OF SAID ARC TUBE AND FASTENED TO SAID TERMINALS, A PAIR OF TRANSVERSE END PLATES SUPPORTED BY SAID TIE RODS NEAR OPPOSITE ENDS THEREOF, EACH PLATE ENGAGING AN END OF THE ARC TUBE, ONE OF SAID END PLATES BEING SLIDABLY MOUNTED ON SAID TIE RODS, AND SPRING MEANS URGING THE SLIDABLY MOUNTED END PLATE AGAINST THE ARC TUBE SO AS TO MAINTAIN THE TIE RODS IN TENSION AND THE ARC TUBE IN COMPRESSION IN SPITE OF EXPANSION OF THE TIE RODS FROM HEAT DURING OPERATION OF THE LAMP.