US2761086A - Electric discharge lamp - Google Patents

Electric discharge lamp Download PDF

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Publication number
US2761086A
US2761086A US307082A US30708252A US2761086A US 2761086 A US2761086 A US 2761086A US 307082 A US307082 A US 307082A US 30708252 A US30708252 A US 30708252A US 2761086 A US2761086 A US 2761086A
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United States
Prior art keywords
lamp
diameter
starting gas
envelope
length
Prior art date
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Expired - Lifetime
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US307082A
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English (en)
Inventor
Edward B Noel
Jr John I Falconer
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General Electric Co
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General Electric Co
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Publication date
Priority to BE522413D priority Critical patent/BE522413A/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US307082A priority patent/US2761086A/en
Priority to DEG12524A priority patent/DE939393C/de
Application granted granted Critical
Publication of US2761086A publication Critical patent/US2761086A/en
Anticipated expiration legal-status Critical
Expired - Lifetime 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
    • H01J61/02—Details
    • H01J61/12—Selection of substances for gas fillings; Specified operating pressure or temperature
    • H01J61/18—Selection of substances for gas fillings; Specified operating pressure or temperature having a metallic vapour as the principal constituent
    • H01J61/20—Selection of substances for gas fillings; Specified operating pressure or temperature having a metallic vapour as the principal constituent mercury vapour
    • 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
    • H01J61/822—High-pressure mercury lamps

Definitions

  • This invention relates to electric discharge lamps containing an ionizable medium including a metal vapor ⁇ and an inert starting gas. lt is more particularly concerned with high pressure ⁇ discharge lamps in the form of elongated and relatively slender tubes which, by reason of conventional mode of manufacture, may be somewhat irregular in diameter along their length.
  • the electric discharge is effected through mercury vapor at a relatively high pressure, for instance at 1A; to 5 ⁇ atmospheres.
  • a highmercury pressure of course entails a high operating temperature so that it is necessary to utilize for the envelope of the lamp a quartz capable of withstanding the high temperatures involved.
  • lamps were made having an envelope of commercial straight drawn quartz tubing and containing the usual filling of mercury with argon as a starting gas, it was found that the 3650 A. output of such lamps was extremely non-uniform along the length of the lamp. could be corrected by utilizing precision bore or sized quartz tubing.
  • quartz tubing is ⁇ prohibitively expensive, costing for instance twice as much as the commercial drawn tubing whereof the cost is already a substantial part of the total cost of the lamp.
  • the object of the present invention is to provide a new and improved lamp of the type discussed above and having substantial uniformity of radiant output perunit length thereof, without using precision bore or sized tubing for the envelope.
  • Another object of the invention is to provide a new and improved elongated source of 3650 A. radiation having substantial uniformity of radiant output along its length and having an efficiency superior to that heretofore realizable.
  • the non-uniformity of radiation is associated with variations in the partial pressures of the mercury vapor and of the starting gas along the length of the lamp.
  • the partial pressure of each component is a substantial ⁇ fraction of thetotal pressure. ⁇
  • the total pressure in the lamp at any ⁇ one time is constant throughout the lamp; however ⁇ in the regions of smaller diameter where the 3650 A. radiation decreases, the partial pressure of the starting gas is a greater percentage of the total pressure, and the partial pressure of the mercury is proportionately less.
  • the partial pressure of mercury may vary by as much as l to 2.5 as between regions of smaller and larger diameter. It was also observed that the spectral distribution of the radiation in the regions of high 3650 A.
  • Fig. l is a side view of a form invention.
  • Fig. 2 is a sectional view of one end of the lamp showing the electrode and seal structure.
  • Fig. 3 is a graph illustrating typical variations in diameter of commercial straight drawn quartz tubing such as that of the lamp of Fig. l, along the length thereof.
  • Fig. 4 is a graph illustrating light output along the of lamp embodying our length of a lamp for various pressures of argon gas filling.
  • ⁇ comprises an elongated slender tubular envelope 1 having thermionic electrodes 2, 2' sealed into. opposite ends thereof, and containing a small quantity of mercury represented by the droplet 3, together with a illing of an inert gas, which, in accordance with the invention, will include a substantial proportion ot' xenon.
  • Fig. l the lamp is shown with a central portion of the envelope removed in order to facilitate the illustration: in an actual construction, the lamp may have an internal diameter of mm. and a length of 125 cm.
  • the electrodes 2, 2" may be of any suitable type, preferably either activated with electron emissive material such as alkaline earth oxides or having other electron emissive materials such as thorium associated therewith.
  • the electrode comprises a tungsten rod 4 projecting into the end of the envelope which is somewhat reduced in diameter, and having wound about it a tungsten slip-over coil 5.
  • a narrow strip or sliver of thorium metal (not visible in the drawing) is enclosed within the coil or helix 5, being laid alongside the tungsten rod 4.
  • the other end of the tungsten rod 4 is welded to a tungsten foil 6 which makes a hermetic seal to the quartz, the quartz being collapsed about it at the end of the lamp.
  • the invention is of particular value in the case of a tube or envelope 1 made of a vitreous material varying appreciably in diameter.
  • the tube may be made of commercial straight drawn quartz of approximately 10 millimeters inside diameter which, in accordance with ordinary commercial manufacture, may vary in diameter up to about 20%.
  • curve 11A illustrates the variation in diameter of a typical tube about 48 inches (125 cm.) long along the length thereof.
  • the range of variation for this lamp is approximately 10%' and this is fairly typical of commercial drawn quartz tubing. It will be observed that the variations appear as short irregular jumps which are superimposed uponrelatively long sweeps producing a peak at 5 inches and another at 35 inches approximately.
  • the long sweeping variations are the ones which apparently cause the non-uniformity of output; the short term irregular variations do not appear to have any noticeable effect upon the uniformity of the discharge.
  • the 3650 A. radiation will exhibit a pattern corresponding in general to the long sweeping variations in diameter. As a rule, it appears that variations in diameter will tend to cause non-uniformity of output when the cycle of variations or distance between successive peaks or valleys exceeds 15 times the inside diameter of the tubing.
  • the variations may be as large as of the internal diameter of the tubing, the effect on the non-uniformity varying of course with its magnitude. in precision bore or sized tubing, the variations do not exceed 1 to 2%, and non-uniformity of 3650 A. output then ceases to be a problem.
  • the curves of Fig. 4 illustrate the relative 3650 A. radiation for various pressures of argon as the starting gas.
  • Curves 21, 22, 23 and 24 show the relative output for-25, 121/2, 6 and 0 millimeters of argon respectively. It will be observed that reducing thev pressure of the argon has two etfects: firstly the over-all output of the lamp increases, and secondly the non-uniformity becomes less pronounced, and substantially disappears in the case of 0 millimeter of argon, that is, when no starting gas is included in the lamp. It will be appreciated of course that as the argon pressure is reduced, the warm-up time increases.
  • the lamp was started by heating it with a torch so as to raise the mercury vapory pressure sufiiciently to allow the establishment of a discharge.
  • a torch so as to raise the mercury vapory pressure sufiiciently to allow the establishment of a discharge.
  • such an expedient is, impractical so that a reduction of the filling pressure of theA starting .gas does not afford an acceptable solution to the problem of reducing non-uniformity of output.
  • curves 31, 32 and 33- illustrate the relative 3,650 A. radiation for this type ofv argon lled lamp under wattage inputs of 2200, 1400 and 1000 watts respectively.
  • the non-uniformity de.- creases fairly rapidly as the wattage input is decreased, the total radiant output decreases at a rate which is greater than the decrease in wattage.
  • no real solution is afforded because the eiliciency of the lamp drops more than can be tolerated.
  • lamps of the general conguration of that illustrated in Fig. l comprising a quartz arc tube of approximately 10 mm. inside diameter and defining an arc gap approximately 125 crn. (48 inches) long.
  • the nominal wattage, voltage, and current of this lamp are 1400 watts, 1675 volts and 1.0 ampere respectively. It will be appreciated that the actual wattage is somewhat less than the product of volts by amperes by reason of the nonsinusoidal waveform of the current.
  • the quantity of mercury is such as to be all vaporized when these operating conditions are attained, in accordance with the teachings of U. S. Patent 2,247,176, Pirani et al.
  • the quantity of mercury is approximately milligrams.
  • the starting gas iilling of these lamps previous to the invention was argon gas at approximately 25 millimeters pressure at room temperature.
  • the condensation of the mercury may readily be determined by means of a photometer which measures the intensity of the radiation from the region in question; as soon as mercury begins to condense, ⁇ the intensity of radiation starts to drop.
  • the measure of the condensation temperature of the mercury gives of course a measure of the mercury pressure
  • the argon pressure has increased approximately l fold and becomes approximately 250 mm., the mercury vapor of course exerting the remaining 850 mm. of pressure.
  • the argon filling exerts approximately one-quarter of the total pressure and the mercury exerts three-quarters thereof.
  • the nonuniformity of 3650 A. output is very pronounced whenever the tubing has variations in diameter of the order in question here.
  • the phenomenon will occur under the stated condition when the starting gas exerts, during operation of the lamp, a partial pressure between and 75% of the total pressure exerted by the starting gas and the mercury vapor. Further experiments have indicated that non-uniformity effect may be just as pronounced with a mm.
  • diameter lamp as with 10 mm. diameter lamp when both have the same percentage diameter variation. In ⁇ general, it appears that non-uniformity becomes a serious factor under the stated conditions with discharge lamps having an arc voltage drop and loading in excess of 4 volts and 5 watts respectively per centimeter length of the envelope.
  • the undesirable nonuniformity characteristic may be substantially reduced or even eliminated under the stated conditions by using a starting gas such as xenon having a lower thermal conductivity than argon.
  • a starting gas such as xenon having a lower thermal conductivity than argon.
  • Our experiments have conrmed that at least for the inert gases neon, argon, krypton and xenon (named herein in decreasing order of thermal conductivity) the non-uniformity is most pronounced with neon and least or substantially non-existent with xenon.
  • Helium appears to provide an exception since being the lightest in atomic Weight and hence having the highest thermal conductivity, it would be expected that the non-uniformity would be most pronounced; in fact, the opposite is true and heliumgives a very uniform output although the efficiency of production of 3650 A.
  • a high pressure gaseous electric discharge lamp forming a line source of radiation comprising an elongated tubular envelope having a length at: least l5 times its diameter and having diameter variations greater than 2% occurring along the length of said lamp with a cycle extending over at least l5 diameters and the inten nal diameter of said envelope -being in the range of approximately 10 to 25 millimeters, a pair of electrodes I sealed into opposite ends of the envelope, and an ionizable atmosphere therein comprising a starting gas and mercury vapor, the quantity of said starting gas being proportioned such that its partial pressure at the operating temperature of the lamp is a substantial fraction of the total pressure exerted ⁇ by the said starting gas and the mercury vapor, the said starting gas comprising predominantly an inert gas having a thermal conductivity less than that of argon whereby the radiant output is substantially uniform per unit length of lamp irrespectively of the said variations in envelope diameter.
  • a lamp as in claim 1 wherein the lamp is operable with a wattage input not less than 5 Watts per centimeter length thereof to develop a total pressure in the range of 1A to 3 atmospheres, the quantity of said starting gas is proportioned such that the partial pressure exerted thereby under normal operating conditions of said lamp is a substantial fraction of the total pressure of said starting gas and mercury vapor, and the said starting gas consists predominantly of xenon at a pressure in the range of a few centimeters whereby to realize a total radiant output exceeding that realizable without any starting gas in the envelope.
  • a lamp as in claim 1 wherein the lamp is operable with a Wattage input not less than 5 watts per centimeter length thereof and a voltage drop not less than 4 volts per centimeter length to develop a total pressure in the lamp of 1A to 3 atmospheres, the quantity of mercury being proportioned to be totally vaporized under the operating conditions vand the quantity of said starting gas being proportioned such that the partial pressure exerted thereby under normal operating conditions of said lamp is a substantial fraction of the total pressure of said starting gas and mercury vapor, and the starting gas consists predominantly of Xenon at a pressure in the range of a few centimeters whereby to realize a total radiant output in excess of that realizable without any starting gas in the envelope.

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  • Discharge Lamps And Accessories Thereof (AREA)
  • Discharge Lamp (AREA)
US307082A 1952-08-29 1952-08-29 Electric discharge lamp Expired - Lifetime US2761086A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
BE522413D BE522413A (is") 1952-08-29
US307082A US2761086A (en) 1952-08-29 1952-08-29 Electric discharge lamp
DEG12524A DE939393C (de) 1952-08-29 1953-08-27 Hochdruck-Gasentladungsroehre

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US307082A US2761086A (en) 1952-08-29 1952-08-29 Electric discharge lamp

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US2761086A true US2761086A (en) 1956-08-28

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2924733A (en) * 1957-09-17 1960-02-09 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Wall-stabilized electric high-pressure gaseous discharge lamp
US2935637A (en) * 1957-03-05 1960-05-03 Thomas M Cortese Fluorescent lamp
US4625149A (en) * 1983-08-10 1986-11-25 Kabushiki Kaisha Toshiba Metal vapor discharge lamp including an inner burner having tapered ends

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1792347A (en) * 1925-02-09 1931-02-10 Philips Nv Producing light of different colors
US1826382A (en) * 1925-01-22 1931-10-06 Claude Neon Lights Inc Vacuum discharge tube
US2247176A (en) * 1931-05-13 1941-06-24 Gen Electric Gaseous electric discharge device
US2353668A (en) * 1942-10-05 1944-07-18 Gen Electric Electric discharge device
US2363531A (en) * 1941-11-27 1944-11-28 Gen Electric Electric discharge device and electrode therefor

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1826382A (en) * 1925-01-22 1931-10-06 Claude Neon Lights Inc Vacuum discharge tube
US1792347A (en) * 1925-02-09 1931-02-10 Philips Nv Producing light of different colors
US2247176A (en) * 1931-05-13 1941-06-24 Gen Electric Gaseous electric discharge device
US2363531A (en) * 1941-11-27 1944-11-28 Gen Electric Electric discharge device and electrode therefor
US2353668A (en) * 1942-10-05 1944-07-18 Gen Electric Electric discharge device

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2935637A (en) * 1957-03-05 1960-05-03 Thomas M Cortese Fluorescent lamp
US2924733A (en) * 1957-09-17 1960-02-09 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Wall-stabilized electric high-pressure gaseous discharge lamp
US4625149A (en) * 1983-08-10 1986-11-25 Kabushiki Kaisha Toshiba Metal vapor discharge lamp including an inner burner having tapered ends

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Publication number Publication date
BE522413A (is")
DE939393C (de) 1956-02-23

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