EP0173347A1 - Arc tube having two apposed hemispherical regions and an intermediate conical region; and high-intensity arc discharge lamp employing same - Google Patents

Arc tube having two apposed hemispherical regions and an intermediate conical region; and high-intensity arc discharge lamp employing same Download PDF

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Publication number
EP0173347A1
EP0173347A1 EP19850110969 EP85110969A EP0173347A1 EP 0173347 A1 EP0173347 A1 EP 0173347A1 EP 19850110969 EP19850110969 EP 19850110969 EP 85110969 A EP85110969 A EP 85110969A EP 0173347 A1 EP0173347 A1 EP 0173347A1
Authority
EP
European Patent Office
Prior art keywords
arc
arc tube
region
lamp
interior
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP19850110969
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German (de)
English (en)
French (fr)
Inventor
Harold L. Rothwell
George J. English
Timothy Fohl
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Osram Sylvania Inc
Original Assignee
GTE Products Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by GTE Products Corp filed Critical GTE Products Corp
Publication of EP0173347A1 publication Critical patent/EP0173347A1/en
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/82—Lamps with high-pressure unconstricted discharge having a cold pressure > 400 Torr
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/30—Vessels; Containers

Definitions

  • the present invention relates to the field of high-intensity arc discharge lamps and more particularly to such lamps employing an arc tube having two opposed hemispherical regions with an intermediate conical region.
  • High-intensity arc discharge lamps are those in which the light-producing arc is stabilized by wall temperature, and the arc tube has a wall loading in excess of three watts per square centimeter. These lamps include groups of lamps known as mercury, metal halide, and high-pressure sodium.
  • operating temperatures generally range between 500° and 1000° C and operating pressures may range between one and ten atmospheres.
  • the fill gas within the arc tube may comprise, for example, mercury, an inert gas, and one more metal-halide additives.
  • the chemical reactions extant within an operating arc tube are quite complex.
  • the arc discharge may be affected by convection currents within the arc tube.
  • the chemistry within the arc tube is affected by the shape of the arc tube.
  • various arc-tube shapes are employed; certain benefits and detriments are associated with each shape.
  • Fohl teaches that an arc tube having a non-uniform diameter, i.e., having an expanded section at or near the center of the arc tube, increases efficacy in vertically operated lamps.
  • the expanded central section reduces the shear between the upward and downward convective flow within the arc tube during operation of the lamp.
  • Some types of compact source arc discharge lamps have arc tubes with non-uniform diameters, such as short arc lamps and heavily loaded capillary lamps.
  • Short arc lamps generally contain a spherical arc tube and have an arc discharge that is electrode stabilized; in these lamps, the arc length is small compared to the arc-tube diameter, the shape of the arc discharge is independent of the shape of the arc tube, and the arc discharge is not affected by convection currents within the arc tube.
  • Capillary arc discharge lamps have been made with a slight bulge at the hottest portion of the arc tube in order to prevent melting of the glass wall.
  • the arc discharge extends to the walls of the arc tube and is confined thereby.
  • the arc discharge is not significantly affected by convection currents within the arc tube.
  • Capillary lamps are generally so heavily loaded (lamp wattage per square centimeter of internal surface area of the arc tube) that they must be artificially cooled in order to prevent the arc tube from melting.
  • a persistent problem is that of species segregation in vertically operated metal halide lamps.
  • the amount of metal halide additive in vapor phase may vary substantially along the arc discharge.
  • Nonuniform species concentration results in non-uniform spectral emission along the arc discharge which adversely affects the color temperature and efficacy of these lamps.
  • Lamps designers have sought to minimize species segregation in vertically operated lamps with only modest degrees of success. Furthermore, there is an ongoing quest to improve lamp operating characteristics, such as luminous efficacy, color temperature, lamp life, and flicker. It would be an advancement in the art if an optimum design could be provided for vertically operated high-intensity arc discharge lamps which substantially eliminates species segregation and provides improved operating characteristics.
  • Another object of the invention is to provide a high-intensity discharge lamp with extended life compared to counterparts in the existing art.
  • a further object of the invention is to provide an arc tube for a high-intensity discharge lamp which produces light that has virtually no flicker perceptible to the human eye when the lamp is operated with alternating electrical current of fifty hertz.
  • an arc tube for a high-intensity arc discharge lamp as well as a high-intensity arc discharge lamp for vertical operation employing same, such arc tube comprising an elongated body with first and second opposed ends.
  • the body of the arc tube hermetically encloses an interior.
  • the body comprises a first region adjoining the first end, a second region adjoining the second end, and a third region intermediate the first and second regions.
  • the first region is substantially hemispherical in shape with radius R 1 .
  • the second region is substantially hemispherical in shape with radius R 2'
  • the third region is substantially a frustum of a right circular cone.
  • R 2 is greater than or equal to two millimeters, and the ratio R l /2 2 is greater than one.
  • the arc tube has two electrodes, one being mounted in the first end and protruding into the interior of the arc tube, the other electrode being mounted in the second end and protruding into the interior of the arc tube.
  • a fill including mercury and at least one metal halide additive is contained within the interior of the arc tube.
  • the fill is capable of generating and sustaining an electrical arc therethrough. Means are provided for supplying electrical energy to the electrodes.
  • FIG. 1 shows arc tube 10 having an elongated body 12 and central axis A-A.
  • Body 12 comprises region 18 adjoining end 14, region 20 adjoining end 16, and region 22 being intermediate regions 18 and 20.
  • Region 18 is substantially hemispherical in shape with radius R 1 .
  • Line B-B shows the approximate boundary between regions 18 and 22.
  • Region 20 is substantially hemispherical in shape with radius R2.
  • Line C-C shows the approximate boundary between regions 20 and 22.
  • Region 22 is substantially a frustum of a right circular cone wherein the radii of the two parallel planes of the frustum are approximately R1and R 2 so that region 22 will join regions 18 and 20, respectively, to form a smooth and continuous surface.
  • arc tube 10 is designed to be operated vertically with end 16 being the lower end, i.e., end 16 is closer to the earth when arc tube 10 is operationally positioned, and end 14 being the upper end.
  • Arc tube 10 encloses a hermetically sealed interior 28.
  • Interior 28 contains a fill (not shown in the drawing) which is capable of generating and sustaining an electrical arc therethrough.
  • Electrodes 24 and 26 are mounted into ends 14 and 16, respectively, of arc tube 10; these electrodes protrude into interior 28.
  • Ends 14 and 16 are formed by a novel method of press sealing.
  • this method see the copending application by Rothwell et al., having attorney's docket No. 83-1-105, filed concurrently herewith and assigned to the assignee hereof, the entire contents of which are incorporated herein by reference.
  • electrical current is provided from the lead-in wires to electrodes 24 and 26 by means of conventional foil strips, e.g., molybdenum, imbedded in the press seals.
  • the distance, L, between the centers of regions 18 and 20 is 20.5 mm.
  • the insertion depth d 1 of electrode 24 is 4 mm; and the insertion depth d 2 of electrode 26 is 4 mm.
  • distance G between the interior extremities of electrodes 24 and 26 is 25.5 mm.
  • Body 12 has wall thickness W of 1.5 mm. The values of the parameters provided herein are approximate and not critical to the invention.
  • the fill is a mixture of mercury, an inert gas (to aid lamp starting), and metal halide additives, e.g., sodium iodide (NaI) and scandium iodide (S C I 3 ).
  • a conventional heat-reflecting coating 32 e.g., Zirconium Oxide (ZrO 2 ), covers portions of bottom region 20 and end 16 in order to reflect infrared radiation back into the lower portion of arc tube 10.
  • FIG. 2 shows a high-intensity arc discharge lamp 40 intended for vertical operation with lamp base 42 up.
  • Arc tube 10 is operationally mounted within light-transmissive outer envelope 44 with end 16 down.
  • environment 46 surrounds arc tube 10 and is hermetically sealed within outer envelope 44.
  • FIG. 3 shows a plot of luminous output of lamp 40 in lumens per watt as a function of wall loading of arc tube 10 in watts per square centimeter. As may be seen from the plot, the wall loading varied from approximately 12 to 16.7 watts per square centimeter. This range corresponds to wattage applied to lamp 40 ranging from 150 to 212 watts.
  • the data in FIG. 3 pertains to environment 46 being a vacuum. The plot shows that the luminous output increases only slightly with increasing wattage indicating that the arc tube geometry is nearly optimum.
  • FIG. 4 is a plot of luminous output in lumens per watt for lamp 40 operating with 175 watts power with respect to nitrogen pressure within outer envelope 44 measured in Torr. The plot shows that an optimum heat transfer is obtained with 200 Torr of nitrogen.
  • the dashed coordinate lines in FIG. 4 indicate the optimum point on the curve corresponding to approximately 113 lumens per watt with 200 Torr of nitrogen.
  • the curve in FIG. 4 comprises two parts, P1 and P2, as shown in the drawing.
  • Pl corresponds to outer pressures of nitrogen less than 200 Torr;
  • P2 corresponds to outer pressures of nitrogen exceeding 200 Torr.
  • the position of the arc discharge was unstable during operation of lamp 40 in the lower Pl-region.
  • the arc tended to bow to one side thereby reducing the effective plasma volume producing light.
  • the outer pressure of nitrogen up to approximately 200 Torr, the arc stably assumed a central position within the arc tube whereby maximum utilization of the arc tube volume was realized. In the P2 region, further increasing the outer pressure of nitrogen has little effect, if any, on luminous output.
  • the 175 watt power rating used in obtaining the data of FIG. 4 corresponds to a wall loading of approximately 13.8 watts per square centimeter for the arc tube of lamp 40.
  • the dashed coordinate lines indicate a luminous output of approximately 96 lumens per watt for lamp 40 operated at 175 watts with a vacuum within the outer envelope.
  • an increase in luminous output from 96 to 113 lumens per watt (18%), approximately has been realized by an optimal choice of pressure within the outer envelope.
  • FIG. 5 shows the temperature distribution over the arc tube wall during vertical operation of arc tube 10 with end 16 down.
  • the temperatures are shown at six locations, labelled Ll, L2,..., L6, in the drawing. Note that the temperature variation is only approximately 25 * over the body of arc tube 10. This result is attributable to the special geometry of arc tube 10.
  • metal halide additives A major function of the metal halide additives is to improve the output spectrum of the lamp over that of mercury lamps.
  • the metal halide additives particularly metal iodides, emit considerable energy in the red and other visible parts of the spectrum which results in vastly improved color rendition.
  • the degree of species segregation can be estimated by measurements of corollated color temperature.
  • the Sylvania M175 high-intensity arc discharge lamp was selected as a representative of the existing art. This lamp is intended for vertical operation; it was a straight tubular arc tube; the power-rating is 175 watts.
  • the M175 has a corollated color temperature of 4500° K and a color rendering index of 65.
  • Lamp 40 which is essentially the same lamp as the M175 except for the specially shaped arc tube as has been described herein, has a corollated color temperature of 3400° K and a color rending index of 60. Thus, lamp 40 exhibits a substantial improvement in color rendering ability (more than 1000° K decrease in corollated color temperature).
  • the two lamps have a slight difference in their color rendering indices; however a comparison of the two indices is not meaningful because the chromaticity or color temperatures of the two lamps differ by so great a degree.
  • FIG. 6 contains least-squares fitted graphs of these temperatures in Kelvin as a function of the distance in millimeters from the top electrode.
  • the arc plasma temperature is considerably higher near the top electrode.
  • the arc temperature increases approximately 7.5° K per millimeter from the bottom electrode toward the top electrode. Since the mercury in the fill burns hotter than do the metal halide additives, this indicates an absence or undersupply of metal halide additives in the upper arc portion.
  • lamp 40 has more uniform plasma temperatures throughout the entire arc with the upper arc being slightly cooler than the lower arc.
  • the arc temperature decreases approximately 2.2° K per millimeter from the bottom electrode toward the top electrode. The temperature variation over the entire arc length has been reduced, by approximately 70%, with lamp 40.
  • lamp 40 operates with an arc discharge having a substantially uniform plasma temperature over the entire arc discharge corroborates the conclusion that the metal halide additives are in plentiful supply at all points in the arc and that the problem of species segregation has been overcome by the special arc tube geometry employed by lamp 40.
  • arc tube 10 provides the improved operating characteristics of lamp 40.
  • point M is the midpoint between the internal extremities of electrodes 24 and 26. Since arc tube 10 is designed for substantially vertical operation, arrow U points upward (away from the earth) and arrow D points downward (toward the earth) when arc tube 10 is operationally positioned.
  • FIG. 1 shows that arc tube 10 has greater surface area and interior volume in the upper portion of the arc tube.
  • This design feature provides greater surface cooling of the upper portion of the arc tube. Within arc tube 10, heat will rise into the upper portion because of gravity and interior convection currents. The greater cooling ability of the upper surface area is necessary to obtain a substantially isothermal temperature distribution over the walls of arc tube 10.
  • FIG. 7 illustrates contours of convection currents within an operating arc tube 10 positioned with end 16 down. These contours are shown as dashed lines in the drawing.
  • the arc discharge is positioned on central axis A-A.
  • the direction of the convection current is upward surrounding the arc discharge and downward adjacent to the walls of arc tube 10.
  • Maintenance of continuous convective flow within arc tube 10 is essential for replenishing the arc discharge with the metal halide additives so that species segregation does not occur.
  • Hemispherical top region 18 and hemispherical bottom region 20 are critical regions because each region changes the direction of convective flow. Such redirection should occur with a minimum of turbulence and without causing a vortex within arc tube 10.
  • the hemispherical shapes of regions 18 and 20 have experimentally been determined to be optimum.
  • Region 20 encloses the lowest portion of interior 28 which is potentially the coolest portion of the interior.
  • a heat-reflecting coating such as zirconium oxide, is frequently employed on the exterior of region 20 to assist in maintaining the metal halides in vapor state.
  • a continuous convective flow along the walls of region 20 is important for the purposes of supplying heat to the region (via hot gases from the upper region) and by sweeping the metal halide additives out of region 20 upward to arc discharge.
  • R 2 should be greater than or equal to two millimeters so that the metal halides additives will not collect in condensate form in the apex portion of region 20.
  • Conical region 22 provides an optimum intermediate region between hemispherical top 18 and hemispherical bottom 20.
  • the increasing radius of a conical cross-section as the cross-section is advanced toward top 18 provides greater surface area and interior volume in the upper portion of arc tube 10 which is essential to the isothermal property of the arc tube.
  • Region 22 also provides essentially straight convective contours between the opposed hemispherical ends of differing radii.
  • the ratio P. 1 /R 2 is an important design parameter in the overall heat balance equation for the arc tube. Since the relative surface areas of the upper and lower portions of the arc tube are directly related to the respective radii, the cooling ability of each portion is likewise related. An optimum choice of R 1 /R 2 is dependent on many factors, such as the length of the arc discharge and the electrode insertion depths; the chemical properties of the fill and metal halide additives as well as the internal operating pressure; the electrical voltage across the electrodes; etc. An optimum range for this ratio for high intensity arc discharge lamps generally of 1000 watts or less has been computed theoretically and experimentally verified to be approximately between 1.5 and 3, preferably within 1.5 and 2.5.
  • Lamp 40 provides light which has virtually no flicker when the lamp is operated with alternating electrical current of approximately fifty hertz.
  • flicker is defined as half-frequency light-intensity differences which are perceptible to the human eye.
  • Flicker is a serious problem in vertically operated metal halide lamps of the existing art operated at approximately fifty hertz. Because of the deficiency of additives in the upper arc, mercury radiation is prevalent and flicker occurs. Since lamp 40 has the feature that axial mixing of the additives is uniform along the vertical arc, flicker is virtually eliminated at fifty hertz. Radiation emitted from metals in the additives, e.g., sodium and scandium, when mixed with the mercury radiation, is sufficiently intense to overcome the eye's sensation of flicker.
  • metals in the additives e.g., sodium and scandium

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  • Discharge Lamps And Accessories Thereof (AREA)
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EP19850110969 1984-08-30 1985-08-30 Arc tube having two apposed hemispherical regions and an intermediate conical region; and high-intensity arc discharge lamp employing same Withdrawn EP0173347A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US64565984A 1984-08-30 1984-08-30
US645659 2000-08-24

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EP0173347A1 true EP0173347A1 (en) 1986-03-05

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EP (1) EP0173347A1 (ja)
JP (1) JPS61107652A (ja)
CA (1) CA1243721A (ja)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0220633A1 (en) * 1985-10-25 1987-05-06 General Electric Company Asymmetric arc chamber for a discharge lamp
EP0271927A2 (en) * 1986-12-18 1988-06-22 Gte Products Corporation A method to reduce color temperature variation in metal halide arc tubes
US4823050A (en) * 1986-09-18 1989-04-18 Gte Products Corporation Metal-halide arc tube and lamp having improved uniformity of azimuthal luminous intensity
GB2213317A (en) * 1980-04-07 1989-08-09 Gen Electric Envelope for high-intensity-discharge electrodeless arc lamp
EP0483507A2 (en) * 1990-09-26 1992-05-06 Gte Products Corporation Low wattage metal halide capsule shape
WO2003060946A3 (en) * 2002-01-16 2004-03-18 Koninkl Philips Electronics Nv Gas discharge lamp
EP1564785A1 (en) * 2004-02-17 2005-08-17 General Electric Company Discharge lamp and method of forming same
US8106589B2 (en) * 2006-03-14 2012-01-31 Koito Manufacturing Co, Ltd. Direct-current high voltage discharge bulb for vehicle lamp

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4311319B2 (ja) * 2004-09-22 2009-08-12 ウシオ電機株式会社 ショートアーク型放電ランプ
JP5747529B2 (ja) * 2011-01-31 2015-07-15 岩崎電気株式会社 セラミックメタルハライドランプ

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1589342A1 (de) * 1967-10-27 1970-12-10 Siemens Ag Anordnung zum schnellen Wiederzuenden einer Quecksilberdampf-Hochdruckgasentladungslampe
US3883766A (en) * 1973-07-19 1975-05-13 Gte Sylvania Inc Method of operating high-intensity arc discharge lamp
EP0034056A1 (en) * 1980-02-06 1981-08-19 Ngk Insulators, Ltd. Method of producing a ceramic arc tube of a metal vapour discharge lamp and ceramic arc tube thereby produced

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1589342A1 (de) * 1967-10-27 1970-12-10 Siemens Ag Anordnung zum schnellen Wiederzuenden einer Quecksilberdampf-Hochdruckgasentladungslampe
US3883766A (en) * 1973-07-19 1975-05-13 Gte Sylvania Inc Method of operating high-intensity arc discharge lamp
EP0034056A1 (en) * 1980-02-06 1981-08-19 Ngk Insulators, Ltd. Method of producing a ceramic arc tube of a metal vapour discharge lamp and ceramic arc tube thereby produced

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, unexamined applications, E section, vol. 7, no. 288, December 22, 1983 THE PATENT OFFICE JAPANESE GOVERNMENT page 97 E 239 * JP - A - 58-165 239 * *

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2213317A (en) * 1980-04-07 1989-08-09 Gen Electric Envelope for high-intensity-discharge electrodeless arc lamp
EP0220633A1 (en) * 1985-10-25 1987-05-06 General Electric Company Asymmetric arc chamber for a discharge lamp
US4823050A (en) * 1986-09-18 1989-04-18 Gte Products Corporation Metal-halide arc tube and lamp having improved uniformity of azimuthal luminous intensity
EP0271927A2 (en) * 1986-12-18 1988-06-22 Gte Products Corporation A method to reduce color temperature variation in metal halide arc tubes
EP0271927A3 (en) * 1986-12-18 1990-06-27 Gte Products Corporation A method to reduce color temperature variation in metal halide arc tubes
EP0483507A2 (en) * 1990-09-26 1992-05-06 Gte Products Corporation Low wattage metal halide capsule shape
EP0483507A3 (en) * 1990-09-26 1992-11-19 Gte Products Corporation Low wattage metal halide capsule shape
WO2003060946A3 (en) * 2002-01-16 2004-03-18 Koninkl Philips Electronics Nv Gas discharge lamp
EP1564785A1 (en) * 2004-02-17 2005-08-17 General Electric Company Discharge lamp and method of forming same
US8106589B2 (en) * 2006-03-14 2012-01-31 Koito Manufacturing Co, Ltd. Direct-current high voltage discharge bulb for vehicle lamp

Also Published As

Publication number Publication date
JPS61107652A (ja) 1986-05-26
CA1243721A (en) 1988-10-25

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