EP0123397A1 - Unsaturated vapor pressure type high pressure sodium lamp - Google Patents
Unsaturated vapor pressure type high pressure sodium lamp Download PDFInfo
- Publication number
- EP0123397A1 EP0123397A1 EP84301612A EP84301612A EP0123397A1 EP 0123397 A1 EP0123397 A1 EP 0123397A1 EP 84301612 A EP84301612 A EP 84301612A EP 84301612 A EP84301612 A EP 84301612A EP 0123397 A1 EP0123397 A1 EP 0123397A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- high pressure
- getter
- arc tube
- sodium
- sodium lamp
- 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.)
- Granted
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Classifications
-
- 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
- H01J61/825—High-pressure sodium lamps
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/24—Means for obtaining or maintaining the desired pressure within the vessel
- H01J61/26—Means for absorbing or adsorbing gas, e.g. by gettering; Means for preventing blackening of the envelope
Definitions
- This invention relates to high pressure sodium lamps of the unsaturated vapor pressure type and more particularly to an unsaturated vapor pressure type high pressure sodium lamp having an arc tube containing a fill gas and a getter in contact with the fill gas.
- High pressure sodium lamps and particularly so-called “saturated” high pressure sodium lamps, are known in the art.
- an elongated arc tube is positioned within an evacuated glass envelope and filled with large amounts of sodium and mercury.
- sodium loss has long been a problem causing undesired increased voltage drop across the lamp and an accompanying reduction in the useful period of "life" of the discharge lamp.
- the large amount or “saturated” sodium content of the arc tube is an attempt to compensate for the uncontrolled loss of sodium during the operational use of the discharge lamp.
- An object of the invention is to provide an enhanced high pressure sodium lamp. Another object of the invention is to provide an unsaturated high pressure sodium lamp. Still another object of the invention is to improve stability of an unsaturated type high pressure sodium lamp. A further object of the invention is to reduce the loss of sodium in an unsaturated vapor high pressure sodium lamp.
- an unsaturated vapor pressure type high pressure sodium lamp having an elongated arc tube located within an evacuated glass envelope and containing a fill including mercury and sodium and a getter forming a metal oxide having a free energy of formation per mole of oxygen more negative than thee free energy of formation per mole of oxygen of sodium oxide.
- Fig. 1 illustrates an unsaturated vapor pressure high pressure sodium lamp of the invention.
- a glass envelope 3 is formed for insertion in a normal screw-type metal base 5.
- a stem portion 7 of glass is hermetically sealed to the glass envelope 3 and extends therein.
- the stem portion 7 has a plurality of electrical conductors 9 sealed therein and extending therethrough.
- An electrically conductive support member 11 is affixed to one of the electrical conductors 9 and to a metal cross-member 13 attached to an electrode 15 at one end of an elongated arc tube 17.
- Another electrode 19 is located at the opposite end of the arc tube 17 and attached to one of the electrical conductors 9 passing through the stem portion 7.
- Heat insulating sleeves 21 and 23 are wrapped about the opposite ends of the arc tube 17 in the vicinity of the electrodes 19 and 15 respectively.
- the glass envelope is evacuated and at least one getter, preferably barium, 25 is positioned adjacent the stem portion 7.
- a lamp fill including sodium and mercury is disposed - - within the arc tube 17 in an amount only sufficient to provide an unsaturated vapor type high pressure sodium lamp.
- a getter forming a metal oxide having a free energy of formation per mole of oxygen more negative than sodium oxide and more positive than aluminum oxide is located within the arc tube 17. The getter is in direct contact with the fill gas and preferably adjacent one of the electrodes 15 and 19 within the arc tube 17.
- the getter is of a material which does not react with mercury or sodium but does react with oxygen at a rate greater than the rate of reaction of sodium with oxygen. Also, the getter has a melting temperature greater than the operational end temperature of the arc tube 17. Moreover, a preferred getter is a zirconium-aluminum alloy getter manufactured by SAES Getters S.P.A., Milan, Italy, and known by the trade name St 101 getter having an alloy containing about 84% zirconium and 16% aluminum.
- each of the lamps included an arc tube 17 of a polycrystalline aluminum oxide material having an inner volume of about 4.3 cubic centimeters.
- Each of the arc tubes 17 contained a relatively low amount of sodium, about 6 X 10 -5 gms, and one of the arc tubes 17 included about 10 mgs of the above-described zirconium-aluminum getter material.
- a high pressure sodium lamp employing an unsaturated vapor pressure
- a getter is positioned within the arc tube of the lamp.
- the arc tube has a relatively low amount of sodium introduced therein, and the getter forms a metal oxide with a more negative free energy of formation than that of sodium oxide.
- the sodium level of the arc tube is maintained and the period of operational use of the lamp is extended as compared with prior known structures.
Landscapes
- Discharge Lamp (AREA)
Abstract
Description
- Concurrently filed Applications entitled "Unsaturated Vapor High Pressure Sodium Lamp Arc Tube Fabricating Process", bearing Attorney's Docket No. 83-1-036 corresponding to U.S. Serial No. 473894, and "Unsaturated Vapor High Pressure Sodium Lamp Getter Mounting", bearing Attorney's Docket No. 83-1-021 corresponding to U.S. Serial No. 473897, relate to an arc tube fabricating process and getter mounting structure for high pressure sodium lamp. Also, concurrently filed applications entitled "Arc Tube Fabrication Process", bearing Attorney's Docket No. 24,833 corresponding to U.S. Serial No. 473896, and "Arc Tube Dosing Process For Unsaturated High Pressure Sodium Lamps", bearing Attorney's Docket No. 24,517 corresponding to U.S. Serial No. 473892, relate to arc tube fabrication and arc tube dosing of unsaturated vapor type high pressure sodium lamps.
- This invention relates to high pressure sodium lamps of the unsaturated vapor pressure type and more particularly to an unsaturated vapor pressure type high pressure sodium lamp having an arc tube containing a fill gas and a getter in contact with the fill gas.
- High pressure sodium lamps, and particularly so- called "saturated" high pressure sodium lamps, are known in the art. Therein, an elongated arc tube is positioned within an evacuated glass envelope and filled with large amounts of sodium and mercury. As is well known, sodium loss has long been a problem causing undesired increased voltage drop across the lamp and an accompanying reduction in the useful period of "life" of the discharge lamp. Thus, the large amount or "saturated" sodium content of the arc tube is an attempt to compensate for the uncontrolled loss of sodium during the operational use of the discharge lamp.
- It has long been recognized that one of the principal causes for this undesired sodium loss is the presence of oxygen impurities in the gas fill of the arc tube. More specifically, it is known that the sodium fill gas tends to combine with oxygen and the aluminum oxide arc tube to provide sodium aluminate whereby undesired sodium loss is encountered.
- One known attempt to reduce this undesired oxygen impurity level is set forth in U.S. Patent No. 4,075,530 of Furukubo et al. Therein, a niobium exhaust pipe is coupled to an arc tube and a decomposable material, NaN3, is located within the exhaust pipe. The exhaust pipe is heated to decompose the NaN3 while the arc tube is cooled to effect condensation. Thus, the material within this exhaust pipe is heated to effect decomposition, transferred to the arc tube wherein materials, such as sodium and mercury, are condensed and whereat undesired gases, such as nitrogen, are withdrawn.
- Unfortunately, locating the decomposable materials in a container external to the arc tube necessitates the application of heat thereto in order to effect the desired decomposition. Thereafter, the decomposed materials must be transferred to the arc tube. Also, the arc tube must be cooled in order to effect the condensation of desired residual materials while permitting the exhaust of other undesired materials. Obviously, such a process is cumbersome of apparatus and unrealistically expensive of labor and materials.
- An object of the invention is to provide an enhanced high pressure sodium lamp. Another object of the invention is to provide an unsaturated high pressure sodium lamp. Still another object of the invention is to improve stability of an unsaturated type high pressure sodium lamp. A further object of the invention is to reduce the loss of sodium in an unsaturated vapor high pressure sodium lamp.
- These and other objects, advantages and capabilities are achieved in one aspect of the invention by an unsaturated vapor pressure type high pressure sodium lamp having an elongated arc tube located within an evacuated glass envelope and containing a fill including mercury and sodium and a getter forming a metal oxide having a free energy of formation per mole of oxygen more negative than thee free energy of formation per mole of oxygen of sodium oxide.
- The invention is illustrated by way of example in the accompanying drawings, in which:
- Fig. 1 is an elevational perspective view of a high pressure sodium lamp of the unsaturated vapor type of the invention; and
- Fig. 2 is a chart comparing relative sodium content with operational time for unsaturated high pressure sodium lamps with and without a getter therein.
- For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended Claims in connection with the accompanying drawings.
- Referring to the drawings, Fig. 1 illustrates an unsaturated vapor pressure high pressure sodium lamp of the invention. Herein, a glass envelope 3 is formed for insertion in a normal screw-
type metal base 5. A stem portion 7 of glass is hermetically sealed to the glass envelope 3 and extends therein. The stem portion 7 has a plurality of electrical conductors 9 sealed therein and extending therethrough. An electrically conductive support member 11 is affixed to one of the electrical conductors 9 and to ametal cross-member 13 attached to anelectrode 15 at one end of anelongated arc tube 17. Anotherelectrode 19 is located at the opposite end of thearc tube 17 and attached to one of the electrical conductors 9 passing through the stem portion 7. Heat insulatingsleeves arc tube 17 in the vicinity of theelectrodes - Further, a lamp fill including sodium and mercury is disposed - - within the
arc tube 17 in an amount only sufficient to provide an unsaturated vapor type high pressure sodium lamp. Importantly, a getter forming a metal oxide having a free energy of formation per mole of oxygen more negative than sodium oxide and more positive than aluminum oxide is located within thearc tube 17. The getter is in direct contact with the fill gas and preferably adjacent one of theelectrodes arc tube 17. - The getter is of a material which does not react with mercury or sodium but does react with oxygen at a rate greater than the rate of reaction of sodium with oxygen. Also, the getter has a melting temperature greater than the operational end temperature of the
arc tube 17. Moreover, a preferred getter is a zirconium-aluminum alloy getter manufactured by SAES Getters S.P.A., Milan, Italy, and known by the trade name St 101 getter having an alloy containing about 84% zirconium and 16% aluminum. - As a specific example, a number of substantially identical 400-watt unsaturated vapor high pressure sodium lamps were fabricated. Each of the lamps included an
arc tube 17 of a polycrystalline aluminum oxide material having an inner volume of about 4.3 cubic centimeters. Each of thearc tubes 17 contained a relatively low amount of sodium, about 6 X 10-5 gms, and one of thearc tubes 17 included about 10 mgs of the above-described zirconium-aluminum getter material. - All of the lamps were processed in a substantially similar manner and lamps with and without the above-mentioned getter located within the
arc tube 17 were energized under substantially normal operating conditions. As can readily be seen from the comparison chart of FIG. 2, the lamp having no getter (Curve "A") within thearc tube 17 lost essentially all of the sodium therein through arc tube wall reaction within a period of less than five (5) hours. On the other hand, the lamp having anarc tube 17 containing a getter (Curve "B"), as previously described, indicates a good supply of sodium after an operating period greater than about 700 hours. - Thus, a high pressure sodium lamp employing an unsaturated vapor pressure has been provided wherein a getter is positioned within the arc tube of the lamp. The arc tube has a relatively low amount of sodium introduced therein, and the getter forms a metal oxide with a more negative free energy of formation than that of sodium oxide. As a result, the sodium level of the arc tube is maintained and the period of operational use of the lamp is extended as compared with prior known structures.
- While there has been shown and described what is at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined by the appended claims.
Claims (8)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US47389583A | 1983-03-10 | 1983-03-10 | |
US473895 | 1990-08-27 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0123397A1 true EP0123397A1 (en) | 1984-10-31 |
EP0123397B1 EP0123397B1 (en) | 1988-12-28 |
Family
ID=23881464
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP84301612A Expired EP0123397B1 (en) | 1983-03-10 | 1984-03-09 | Unsaturated vapor pressure type high pressure sodium lamp |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP0123397B1 (en) |
JP (1) | JPS59169050A (en) |
AU (1) | AU578603B2 (en) |
CA (1) | CA1222273A (en) |
DE (1) | DE3475855D1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4755721A (en) * | 1987-03-16 | 1988-07-05 | Iwasaki Electric Co., Ltd. | High pressure sodium vapor lamp having unsaturated vapor pressure type characteristics |
EP0328209A1 (en) * | 1988-02-10 | 1989-08-16 | Koninklijke Philips Electronics N.V. | Unsaturated high-pressure sodium lamp |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3805105A (en) * | 1971-06-30 | 1974-04-16 | Gte Sylvania Inc | High pressure electric discharge device with zirconium-aluminum getter |
DE2645930A1 (en) * | 1975-10-14 | 1977-05-26 | Gen Electric | ALKALI METAL LAMP WITH A TUBE MADE OF ALUMINUM OXIDE CERAMIC AND A METAL GETTER STRUCTURE |
GB1580991A (en) * | 1976-04-07 | 1980-12-10 | Egyesuelt Izzolampa | High pressure gas discharge light source with metal halide additive |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3203901A (en) * | 1962-02-15 | 1965-08-31 | Porta Paolo Della | Method of manufacturing zirconiumaluminum alloy getters |
US3384798A (en) * | 1966-04-26 | 1968-05-21 | Gen Electric | High pressure saturation vapor sodium lamp containing mercury |
GB1211176A (en) * | 1967-02-16 | 1970-11-04 | Gen Electric | High-pressure sodium vapor lamp |
US3453477A (en) * | 1967-02-16 | 1969-07-01 | Gen Electric | Alumina-ceramic sodium vapor lamp |
US3485343A (en) * | 1967-08-28 | 1969-12-23 | Gen Electric | Oxygen getter for high pressure sodium vapor lamp |
US3727089A (en) * | 1970-06-24 | 1973-04-10 | S Chow | Small sized stroboscopic tube for photographic use |
US4075530A (en) * | 1976-04-21 | 1978-02-21 | Japan Storage Battery Company Limited | High pressure sodium vapor lamp of unsaturated vapor pressure type |
CA1214196A (en) * | 1983-02-14 | 1986-11-18 | Jack M. Strok | Color rendition high pressure sodium arc tubes having an oxygen getter |
-
1984
- 1984-03-06 CA CA000448953A patent/CA1222273A/en not_active Expired
- 1984-03-09 AU AU25478/84A patent/AU578603B2/en not_active Ceased
- 1984-03-09 DE DE8484301612T patent/DE3475855D1/en not_active Expired
- 1984-03-09 EP EP84301612A patent/EP0123397B1/en not_active Expired
- 1984-03-09 JP JP4415684A patent/JPS59169050A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3805105A (en) * | 1971-06-30 | 1974-04-16 | Gte Sylvania Inc | High pressure electric discharge device with zirconium-aluminum getter |
DE2645930A1 (en) * | 1975-10-14 | 1977-05-26 | Gen Electric | ALKALI METAL LAMP WITH A TUBE MADE OF ALUMINUM OXIDE CERAMIC AND A METAL GETTER STRUCTURE |
GB1580991A (en) * | 1976-04-07 | 1980-12-10 | Egyesuelt Izzolampa | High pressure gas discharge light source with metal halide additive |
Non-Patent Citations (1)
Title |
---|
PATENT ABSTRACT OF JAPAN, unexamined applications, M section, vol. 3, no. 12, January 31, 1979 THE PATENT OFFICE JAPANESE GOVERNMENT page 16 M 47 & JP-A-53-135 187 (hitachi) * |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4755721A (en) * | 1987-03-16 | 1988-07-05 | Iwasaki Electric Co., Ltd. | High pressure sodium vapor lamp having unsaturated vapor pressure type characteristics |
EP0282657A1 (en) * | 1987-03-16 | 1988-09-21 | Iwasaki Electric Co., Ltd. | High pressure sodium vapor lamp having unsaturated vapor pressure type characteristics |
EP0328209A1 (en) * | 1988-02-10 | 1989-08-16 | Koninklijke Philips Electronics N.V. | Unsaturated high-pressure sodium lamp |
Also Published As
Publication number | Publication date |
---|---|
AU2547884A (en) | 1984-09-13 |
EP0123397B1 (en) | 1988-12-28 |
DE3475855D1 (en) | 1989-02-02 |
AU578603B2 (en) | 1988-11-03 |
JPS59169050A (en) | 1984-09-22 |
CA1222273A (en) | 1987-05-26 |
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