US2307502A - Vapor electric device and method of operation - Google Patents

Description

Jan. 5, 1943.

N. r. GQRDON ETAL VAPOR ELECTRIC DEVICE AND METHOD OF OPERATION Filed March 28, 1941 Inventors: Newell TGor'don, Willis Rwhitneg,

Then" Attorney.

water-cool vapor though an emcient Pa tented Jan. 5,

FFICE varoa anaemic nsvrcs AND munch on Q OPERATION Newell '1'. Gordon nectady, N- Y.,

and Willis B. Whitney,'Scheassignors to-General Electric Company, a corporation of New York Application March 28, 1941, sem No. 385,642 1 Claims. (cine-122) The present invention relates to vapor electric devices, such as mercury lamps, and in particular to devices of this type which are operated at relatively high vapor pressures. Our invention is applicable with especial benefit to high pressure vapor lamps which are provided with an envelope of substantially capillary dimensions in which under operating conditions there is a pressure of at least several atmospheres. High pressure lamps are described in Bol, Elenbaas and Lemmens United States Patent No. 2,094,694, issued October 5, 1937, and in Germer United States Patent No. 2,202,199, issued May 28, 1940.

It is the object of improved apparatus and a method whereby vapor devices may be maintained at a desired operating temperature. In the operation of vapor electric devices of high wattage consumption, it is necessary to carry heat away more rapidly than the natural rate of heat dissipation. The progressive increase of vapor pressure otherwise would result in correspondingly increasing the voltage necessary to operate the lamp. Assuming the lamp to be operated from a supply circuit of high reactance, it eventuallywould be extinguished. In that event the device would not restart until it had cooled and the vapor pressure had fallen considerably lower than the pressure at which it ceased to operate. This would result inunsatisfactory intermittent operation.

Another source of difilculty encountered in the operation of high pressure lamps is the devitrification of such parts of the vitreous envelope as are in contact with the discharge, the devitriflcatlon being especially marked in the neighborhood of the electrodes. In the forms of high pressure lamps shown in the above-mentioned 301 et al. patent in which the pressure of mercury vapor reaches many atmospheres during normal operation, the heat dissipation requirements are especially exacting.

High pressure lamps may be cooled by the circulation of water over their surfaces, such ar'- rangement being described in B01 and Lemmens United States Patent No. 2,094,695, patented October 5, 1937. Ordinarily, high pressure merour invention to provide an cross section on cury lamps cons'ructed to operate with a, loading of more than 200 watts per centimeter of discharge columnhave been water-cooled. It is inconvenient and in electric devices. Water, al-

cooling medium, is subject to freezing. Also, water and other cooling fluids are subject to fouling, especially when recirculated in a closed system. Furthermore, liquid cooling some cases it is lnefllcient to.

,mally present during provided improved gas-cooling means,

is apt to be too energetic at the region where unvaporized material, such as mercury, is present. Ordinary air cooling, that is, cooling by air circulation, such as may be produced by a fan, is not suiliciently effective, particularly in lamps in which the discharge tubeis of small bore as indicated in Fig. 1 and pressures of mercury vapor of at least several atmospheres are noroperation. 2 of our invention, we have conveniently using air as the cooling medium, by the use of which vapor electric devices may be operated at high pressures with materially higher wattage inputs than heretofore possible. Another advantageous result of our invention is asreduction of devitriiication of the envelope in which a high pressure discharge occurs and which is cooled in accordance with our, invention.

As will'be pointed out in greater particularity in the appended claims, the main novel feature of our invention comprises a method of and apparatus for applying to a vapor electric device high velocity jets of cooling fluid, preferably air, the cooling jet having a dimension which is materially smaller than the surface which is being cooled. Another feature of our invention consists in applying such cooling jet or As a consequence is apt to be most severe, that is, ordinarily adjacent the electrodes. sists in applying the cent the surface to shown in the accompanying drawing in which Fig. 1 shows a vapor lamp and jet cooling means in side elevation; Fig. mounted in a light projector; Fig. 3 is a partly sectionalized side view on an enlarged scale of a modification in which part of a tubular lamp is coated with a light-reflecting layer; Fig. 4 is a lines 4-4 of the modification of Fig. 3; and Figs. 5 and 6 are perspective views of nozzles for furnishing cooling jets.

The lamp shown in Figs. 1, 2 and 3 comprises a tubular envelope {provided at opposite ends respectively with electrodes 3, 4 which may consist of tungsten. The of vitreous or fused quartz,

ing glass also may be used. ductors I, S are sealed into the envelope by a sealing glass as described in said 301 et al. Patent No. 2,094,694 and as well understood. These conducenvelope 2 ordinarily consists although heat-resistv jets to the envelope at a region where devitriflcation of the envelope Still another feature con- 2 shows such combination The electrode contors are connected to external contact caps I, 8.

At the respective ends of the envelope 2 and surrounding the electrodes is a quantity of mercury as shown at 9, l0. Part of the mercury is contained in a pocket I! whereby the amount of mercury is adjusted during the manufacture of the lamp. The electrodes 3, 4 project about one millimeter beyond the mercury surface. The envelope also contains a charge of starting gas, such for example as argon or neon, at a pressure of about 50 millimeters of mercury. The lamp is supported by electrically conductive supports l3, M, on the ends of which it is held by spring clips l5, l6. Operating current is supplied by the conductors IT, IS connected to the contact terminals i9, 20. The supports l3, M are mounted on an insulating base 2 l Such a device may be operated-at a pressure exceeding 40 atmospheres and up to 200 atmospheres and higher.

Unless the envelope of such device is energetically cooled, it will continue to rise in tem perature upon being put into operation, the voltage required to operate the device rising at the same time. The rise in vapor pressure with increasing temperature would result in extinguishing the discharge after a short period of operation, or, if suificient voltage should be available, excessive rise of internal pressure would cause it to burst.

Efiective cooling and continuous operation may be obtained by directing sharply localized jets of compressed air, or other suitable cooling fluid, against the envelope of such device at the regions adjacent the respective electrodes. These jets of air, delivered by the nozzles 22, 23 and supplied by a pipe 24, should be directed substantially perpendicular to the axis of the envelope. Although nozzles such as shown in Fig. 1 are ordinarily preferred, the jets may be modified in some cases as shown at 22 and 23", Fig. 6. Satisfactory jet cooling has been afiorded by maintained pressures of to 40 pounds. The jets of air may have a diameter of about 50 to 80 mils. Preferably the centers of the respective jets of air are located opposite the ends of the respc tive electrodes. When the ends of the nozzles are lengthened to form slits, as shown in Fig. 6, a modifying efiect can be exerted upon the vapor pressure and electrical characteristics of the lamp. For example, if the slit is positioned to direct the jet against a portion of the envelope adjacent unvaporized mercury, then the vapor pressure can'be maintained at a lower value.

The nozzle openings should be spaced closely adjacent the surface to be cooled. A spacing of 1 to 2 millimeters ordinarily is satisfactory. Apparently a layer of warmed air, which tends to normally adhere to" the surface to be cooled, must be effectivelyand rapidly eroded away. The jets of pressure air have an effective bufling action which we have found to be absent in the usual forms of air circulation.

Surprisingly, such localized jets adequately cool the envelope portion between the regions on which the jets impinge. As shown in Fig. 2, the described lamp and the jet-cooling adjuncts may be mounted in a light projector having a housing 26 provided with the usual reflector (not shown) and mounted on the supports 21, 28.

The lamp shown in Fig. 1 can be operated with a lighting efiiciency of 86 lumens per watt of consumed electric energy and with brilliancies over 50,000 candles per square centimeter. Because of this high brightness, it is well adapted for use insearchlights;

delivered by two nozzles 3!, 32 extend linearly substantially over the entire discharge distance between the electrodes. The cooling jets of air' or other suitable fluid preferably are delivered tangentially as shown in Fig. 4. In Fig. 5 is shown in perspective the nozzle 3! with its slit-shaped opening 34 carried by the supply tube '35. When employing a slit-shaped nozzle the width of the slit should be materially less than the diameter of device to be cooled. In the particular case illustrated, its width is about one-fifth the diameter of the lamp. In both modifications of our invention the portion of the envelope of quartz, or other refractory material, extending between the electrodes is cooled either locally or throughout its length by the impingement of one or more highvelocity jets which, however, exert but little cooling effect on the masses of mercury or whatever vaporizable material may be employed in the device. Our copending divisional application Serial No. 465,114, filed November 10, 1942, is directed to features of our invention which are embodied in the devices illustrated by Figs. 3, 4 and 5.

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

1. A vapor electric device comprising an envelope, electrodes therefor, a current-carrying medium including mercury in said envelope, the resulting mercury vapor being at superatmospheric pressure under normal operating conditions, cooling means including nozzlesterminating respectively opposite said electrodes closely adjacent said envelope and having an opening of 'such small dimension that a jet of air issuing therefrom impinges exclusively on said envelope, and means for supplying air thereto at a pressure sufiicie'ntly high to maintain the vapor pressure v in said envelope below a predetermined discharge-extinguishing limit.

2. A vapor. electric device comprising an envelope, electrodes therein spaced apart, a current-carrying medium in said device including a vaporizable material which in a condensed state surrounds said electrodes at least in part and cooling means constructed to supply jets of gas under pressure directed against the parts of the envelope which are immediately adjacent said electrodes and-having at least one dimension which is relatively small with relation to the surface being cooled.

3. A high pressure vapor electric lamp comprising a tubular quartz envelope, electrodes hav- Y ing conductors sealed into the wall of said envelope, a starting gas in said env'elope, bodies of mercury therein respectively surrounding said conductors and being sufficient in quantity to produce under operating conditions a vapor pressure of at, least several atmospheresand means for directing against said envelope at regions adjacent said respective mercury bodies constricted jets of cooling gas at'a pressure of at least about 10 pounds having asectional area less than the surface receiving the local impingement of said jets.

4. A high pressure vapor electric discharge device comprising an elongated tubular envelope,

: electrodes having stems respectively sealed into said envelope at the ends thereof, a filling for said envelope comprising a material which is vaporizable at the operating temperature of said envelope, and cooling means starting gas and a constructed to project localized jets of compressed air against said envelope at regions adjacent said electrodes and substantially perpendicular to-an axis passing through said electrodes.

5. A high pressure mercury vapor lamp comprising an elongated tubular envelope which is capable of withstanding an internal pressure of about 40 to 200 atmospheres, electrodes of tungand maintaining the pressure sten therein having conductors sealed into the porizable material, which method consists in carby the impingement of constricted jets of air rep rying away heat irom'said envelope by the impingement o! constricted jets of air thereon at regions adjacent said electrodes, the distance between said envelope and the base of said jetsand the area of impingement of said jets being substantially the same-as the cross section thereof, of. compressed air for said jets at about 10 to 40 pounds,

7. A method of operating an electric discharge device comprising an envelope of capillary di-- mansions containing electrodes positioned near the ends thereof, and being provided with a starting gas and a quantity of mercury, method consists in operating said device with an energy input of at least about 200 watts per centimeter of discharge column, cooling said device spectively directed externally against the electrode regions of said envelope, so regulating the length of said jets that the area of impingement thereof is substantially the same as the diameter thereof, and maintaining the velocity of air delivery of said jets sumciently high to prevent the voltage required to maintain a discharge between said electrodes from a predetermined value.

. T. GORDON. WILHS R. WHITNEY.

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