US2347048A - Vapor electric device and method of operation - Google Patents

Description

April 18, 1944. R N ET AL 2,347,048

VAPOR ELECTRIC DEVICE AND METHOD OF OPERATION Original Filed March 28, 1941 Inventors: i Newell T. Gordon,

32 Willis Rwhibneg,

Th eir- Attorney.

Patented Apr. 18, 1944 VAPOR ELECTRIC DEVICE .AND 'METHOD OF OPERATION Newell T. Gordon and Willis R. Whitney, Schenectady, N. .Y., assignorsr-to General Electric Company, a corporation .of New -York 1 Original application March 28,1941, Serial No.

385,642. Divided and this application November '10, 1942, Serial No. 465,114

9 Claims. (01. jive-#122) The present application is a division of our prior application Serial No. 385,642, now Patent No. 2,307,502, and 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 B01, 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 our invention to provide an 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 a superatmospheric pressure lamp to be operated from a supply circuit of high reactance, it eventually would 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 in unsatisfactory intermittent operation.

Another source of diiliculty encountered in the operation of high pressure lamps is the devitrification of such-parts of the envelope as are in contact with the discharge, the devitrification being especially marked in the neighborhood of, the electrodes. In the forms of high pressure lamps shown in the above-mentioned B01 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 arrangement being described in B01 and Lemmens United States Patent No; 2,094,695, patented October 5, 1937. Ordinarily, high pressure mercury lamps constructed to operate with a loading of more than 200 watts per centimeter of discharge column have been water-cooled. Itisinconvenient and in some cases it is inefiicientto water-cool vapor electric devices. ,Water, although an efiicient cooling medium, is subject to freezing. Also, water and other cooling fluids are subject to fo'uling, especially when recirculated in a closed'system. Furthermore, liquid cooling is apt to be too energetic at the region where unva poriaed 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 sufficiently effective, particularly in lamps in which the discharge tube is of small bore as indicated in Fig. l and pressures of mercury vapor of at least several atmospheres are normally present during operation.

As aconsequence of our invention, we have providedimproved gas-cooling means, conveniently using air as the cooling medium, by the use of which vapor electric'devi'ces may be operated at high pressures with materially higher wattage inputs than heretofore possible. Another advantageous result of our'inve'ntion is a reduction of devitrification of the lamp envelope which, as stated in the above-mentioned Patent 2,094,694, may consist of vitreous silica or heatresisting glass.

. As will be pointed out in greater particularity inthe 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. The claims in the present application are directed particularly to a modification of our invention whereby a high velocity jet of cooling air is directed against the envelopeintermediate' said electrodes. The nozzle orifice is positioned so closely adjacent the surface to be cooled that the area of impingement of the jet is substantially the same or-but little greater than the diameter of the jet.

Several embodiments of our invention are shown in the accompanying drawing in which Fig. 1 shows a vapor lamp and jet cooling means in side elevation; Fig. 2 shows such combination 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 alight-"reflecting layer; Fig. 4 is a cross section on 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. 2 provided at opposite ends respectively with electrodes 3, 4 which may consist of tungsten. The envelope 2' ordinarily consists -01 vitreous or fused quartz, although heat-reof 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, 15. Operating current is supplied by the conductors ll, l8 connected to the contact ter-' minals I9, 20. The supports l3, l4 aremounted on an insulating basell. Such a device may be operated at a pressure exceeding 40 atmospheres and up to 200 atmospheres and higher.

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

Effective cooling and continuous operation may be obtained by directing sharply localized jets of compressed air, or other suitable cooling'fluid, against the envelope'ofsuch device as shown in the drawing. These jets'of air, delivered by the nozzles 22, 23 and supplied by a pipe 24, should be directed substantially perpendiculanto the axis of the envelope. Although nozzlessuch as shown in Fig. 1 are ordinarily preferred, .the jets may be modified in some cases asshownat 22 and 23', Fig. 6. Satisfactory jetcooling has been afiorded by maintainedpressures of to.40 pounds. The jets of air may havea diameter of about].50 to 80 mils. Preferably the centers of therespective jets of air are located opposite'the ends of the respective electrodes. When theends of thenozzles are lengthened to form slits, as shownin Fig. 6, a modifying effect can be exerted upon the. vapor' pressure and electrical parently a layer of warmed air, which tends to normally adhere to the surface to be cooled, must be effectively and rapidly eroded away. The jets of pressure air have an effective bufiing action which we have found to be absent in the usual forms of air circulation. Surprisingly, such 10- calized jets adequately cool the envelope portion between theregions 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 housing26 provided with the usual reflector (not shown) and mounted on the supports21, 28.

The lamp shown in Fig. 1 can be operated with a lighting efficiency 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 in searchlights.

In our application Serial No. 385,642, filed March 28, 1941, claims havebeen made on the embodiment of our invention which is shown in Fig. 1. In this species of device compressed cooling air is jetted against the envelope at regions adjacent said electrodes. In the present application, we are directing claims to a modified embodiment in which the cooling air is jetted upon the region of the envelope in which the discharge occurs, that is, the region of the envelope whichis intermediate the electrodes.

The lamp shown in Figs. 3 and 4 is in most respects similar to the lamp shown in Figs. 1 and .2, but differs therefrom in two main aspects.

First, the envelope 2 is provided over approximately half of its circumferential surface with a coating 39 of light-reflecting material, such as platinum or gold, which extends longitudinally over the discharge space between the electrodes. Second, the jets of cooling fluid 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. As appears in the drawing, the jetted cooling air is distributed substantially symmetrically with respect to the midlength of the envelope so that corresponding points toward the. opposite ends receive substantially equal cooling.

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 high velocity jets which, however, exert but little cooling effect on the masses of mercury or whatever vaporizable material may be employed in the device.

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

1. A method of operating a high pressure electric discharge device comprising a tubular heatresistant vitreous envelope containing electrodes adjacent its ends, and also containing starting gas and mercury, which method consists in operating the device with an energy input sufficient to maintaina discharge-constricting superatmospheric pressure of mercury therein, whereby devitrification of the envelope is entailed, jetting compressed cooling air externally against said envelope intermediate said electrodes with a conby the energy input aforesaid.

2. A method of operating a high pressure electric discharge device comprising atubular heatresistant vitreous envelope containing electrodes adjacent its ends, and also containing starting gas and mercury, which method consists in operating the device with an energy input sufficiently high to maintain a discharge-constricting superatmospheric pressure of mercury therein, and to produce substantial devitrification of the envelope, jetting compressed cooling air externally against said envelope intermediate said electrodes with a constricted air stream width, transversely of the envelope, substantially less than the envelope width presented to the impinging air, distributing the cooling air substantially symmetrically lengthwise of the envelope with respect to its mid-length, and maintaining the velocity of air jet delivery sufilciently high to substantially reduce envelope temperature and devitrification while allowing discharge-constricting internal pressure to be maintained by the energy input aforesaid.

3. A method of operating an electric discharge device comprising a tubular vitreous envelope containing electrodes adjacent the ends thereof and also containing starting gas and mercury, which method consists in operating said device with an energy input sufliciently high to cause said envelope to be heated to a temperature at which volatilized mercury therein will have a pressure of at lea-st several atmospheres, projecting a stream of compressed cooling air externally and transversely against the portion of said envelope which is intermediate said electrodes, the width of said stream being substantially less than the envelope diameter, and maintaining the pressure of such cooling air at about to 40 pounds, thereby avoiding the devitrification of such envelope While maintaining a predetermined high operating pressure therein.

4. A high pressure vapor electric discharge device comprising a tubular heat-resistant vitreous envelope containing electrodes adjacent its ends, and also starting gas and mercury for providing discharge-constricting superatmospheric pressure in the envelope during normal operation, in combination with nozzle means for jetting compressed cooling air externally against said envelope intermediate said electrodes with a constricted air stream Width, transversely of the envelope, substantially less than the envelope width presented to the impinging air, whereby envelope temperature and devitrification are substantially reduced while maintenance of dis-charge-constricting internal pressure is allowed.

5. The invention as set forth in the next preceding claim further characterized in that the distance of the nozzle means from the envelope is so short that the Width of air jet impingement on the envelope is substantially the air jet width.

6. A high pressure vapor electric discharge device comprising a tubular vitreous envelope containing electrodes adjacent its ends and also starting gas and mercury for providing superatmospheric pressure in the envelope during normal operation, said envelope having a coating of lightreflecting material covering approximately half the circumferential surface thereof and extending longitudinally over the discharge space in said envelope, and means for projecting a fiat jet of compressed cooling air externally against said envelope intermediate said electrodes, said jet having a width transversely of said envelope less than the envelope diameter, whereby envelope temperature is reduced without preventing the development of desired normal high pressure.

'7. A vapor electric device comprising an elongated tubular envelope, electrodes therein positioned near the ends thereof, a current-carrying medium therein including mercury, and means :for supplying air under pressure to cool said envelope at a region between said electrodes, said means including one or more nozzles for delivering constricted air jets, each nozzle having a slitshaped opening the transverse dimension of which is less than the diameter of said envelope, the distance between said opening and the envelope being so short that the width of air jet impingement is substantially the air jet Width.

8. An electric discharge device comprising a tubular vitreous silica envelope, electrodes having stems sealed into opposite ends of said envelope, argon gas and mercury in said envelope, said device being constructed and proportioned to operate normally at superatmospheric pressure, and nozzle means constructed to project a jet of cool ing fluid or linear extension externally against said envelope, the transverse dimension of said jet being less than the diameter of said envelope, said nozzle means being so positioned closely adjacent said envelope as to deliver cooling fluid tangentially with respect to said envelope.

9. A high pressure vapor electric discharge device comprising a tubular, heat-resistant, vitreous envelope containing electrodes adjacent its ends, and also starting gas and mercury for providing discharge-constricting superatmospheric pressure in the envelope during normal operation, in com bination with nozzle means for jetting compressed cooling air externally against said envelope intermediate said electrodes, said means being arranged to distribute this air substantially symmetrically lengthwise of the envelope with respect to its mid-length and in a constricted air stream width, transversely of the envelope, substantially less than the envelope width presented to the impinging air, whereby envelope temperature and devitrification are substantially reduced While maintenance of discharge-constricting internal pressure is allowed.

NEWELL 'I'. GORDON. WILLIS R. WHITNEY.

Images