Title:
HIGH PRESSURE MERCURY VAPOR DISCHARGE LAMP
United States Patent 3740605
Abstract:
The addition of suitable proportions of mercury iodide and other selected metals to a mercury vapor lamp containing sodium iodide limits the change in operating voltage with time and provides longer life.
US Patent References:
High pressure electric discharge device containing mercury, halogen, scandium and alkalimetal
Koury et al. - October 1968 - 3407327
HIGH PRESSURE VAPOR DISCHARGE LAMP WITH CESIUM IODIDE
Gungle et al. - May 1970 - 3514659
METAL HALIDE DISCHARGE LAMPS WITH RARE-EARTH METAL OXIDE USED AS ELECTRODE EMISSION MATERIAL
Zollweg et al. - September 1970 - 3530327
HIGH-INTENSITY VAPOR ARC-LAMP
Hanneman et al. - January 1971 - 3558963
High pressure discharge device having a fill including iodine mercury and at least one rare earth metal
Butler et al. - August 1967 - 3334261
High pressure electric discharge device containing mercury, halogen, scandium and alkalimetal
Koury et al. - October 1968 - 3407327
HIGH PRESSURE VAPOR DISCHARGE LAMP WITH CESIUM IODIDE
Gungle et al. - May 1970 - 3514659
METAL HALIDE DISCHARGE LAMPS WITH RARE-EARTH METAL OXIDE USED AS ELECTRODE EMISSION MATERIAL
Zollweg et al. - September 1970 - 3530327
HIGH-INTENSITY VAPOR ARC-LAMP
Hanneman et al. - January 1971 - 3558963
High pressure discharge device having a fill including iodine mercury and at least one rare earth metal
Butler et al. - August 1967 - 3334261
Inventors:
Divoix, Jacques Climeut (Mesnil-le-Roi, FR)
Taxil, Andre Marc V. (Rueil-Malmaison, FR)
Taxil, Andre Marc V. (Rueil-Malmaison, FR)
Application Number:
05/174535
Publication Date:
06/19/1973
Filing Date:
08/24/1971
View Patent Images:
Export Citation:
Assignee:
Claude (Paris, FR)
Primary Class:
International Classes:
H01J61/18; H01J61/22; H01J61/12; H01J61/20
Field of Search:
313/229
Primary Examiner:
Lake, Roy
Assistant Examiner:
Hostetter, Darwin R.
Claims:
What is claimed is
1. A high-pressure mercury-vapor lamp filling comprising a mixture of materials including mercury, sodium iodide, argon, mercury iodide, cesium iodide, yttrium and a further material selected from the group consisting of thallium iodide, indium iodide, scandium, thorium and magnesium.
2. The lamp of claim 1 including an additional further material selected from the group consisting of thallium iodide, indium iodide, scandium, thorium and magnesium.
1. A high-pressure mercury-vapor lamp filling comprising a mixture of materials including mercury, sodium iodide, argon, mercury iodide, cesium iodide, yttrium and a further material selected from the group consisting of thallium iodide, indium iodide, scandium, thorium and magnesium.
2. The lamp of claim 1 including an additional further material selected from the group consisting of thallium iodide, indium iodide, scandium, thorium and magnesium.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements in high-pressure mercury-vapor electric discharge lamps and, more particularly, to lamps of this type which contain, in addition to mercury, alkali metal halogenides.
2. Description of the Prior Art
In these lamps, luminous radiation is generally produced either by very concentrated intense emission rays, as in the case of metals such as thallium, sodium and indium, or by very numerous rays spread over the entire spectrum as in the case of rare-earth elements or transition metals such as scandium, hafnium, thorium. The lamp is generally formed of an outer glass envelope and an inner high pressure discharge tube of vitreous material such as quartz.
The metals are usually introduced into the lamp in the form of halogenides and, more particularly, in the form of iodides which are highly volatile halogenides. One of the most used iodides is sodium iodide which, due to its low vapor pressure at the lamp operation temperature, is gaseous within the discharge region of the inner tube and liquid about the tube walls. Due to a diffusion phenomenon through the tube walls, the sodium iodide is decomposed and the sodium leaves the inner area resulting in an enrichment of iodine inside the tube, which restrains the electric discharge phenomenon causing an increased voltage across electrode terminals and, after a few hundreds of operation hours, renders lighting difficult.
One of the solutions adopted to slow the sodium diffusion is in locating the inner tube within an area of an outer envelope filled with a neutral gas such as nitrogen, at adequate pressure. Thus lamps are obtained in which the electrode terminal voltage increases less rapidly with time.
SUMMARY OF THE INVENTION
It is therefore, an object of the present invention to provide an improved high-pressure mercury-vapor electric discharge lamp containing an alkali-metal halogenide, by including additional materials to maintain the operating voltage substantially constant with time.
In such lamps the alkali-metal halogenides, in particular, may be sodium halogenide and the added materials may include additions of mercury halogenide, and a halogenide of easily ionizable metal and a further metal which may be in decreasing order of preference: yttrium, thorium, magnesium, hafnium, aluminum and rare-earth metals.
The metal halogenides introduced into high-pressure mercury-vapor lamps are generally iodides and the metal halogenide which is added in the present invention is cesium iodide, cesium having a low ionization energy.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following Table 1 shows three examples A, B and C of fillings for high-pressure mercury-vapor lamps having a power of 400 watts obtained with an inner tube having a diameter of 18 mm and a spacing between electrodes of 50 mm. In each example, the left-side column shows the possible pressure and weight limits in torrs (millimeters of mercury) and in milligrams, respectively, of the filling materials and the right-side column the values used in an embodiment. The left hand column lists the various materials in the compositions. ##SPC1##
The example A relates to addition of yttrium and cesium iodide with mercury iodide in a high-pressure mercury-vapor lamp already containing iodides of sodium (having a characteristic yellow color), of thallium (having a green color) and of indium (having a blue color).
The example B relates to addition of yttrium and cesium iodide with mercury iodide in a high-pressure mercury-vapor lamp already containing sodium iodide and scandium, which have a very close color spectrum.
In the example C, compared with the example B, yttrium is replaced by thorium and magnesium.
Yttrium may also be replaced by hafnium, aluminum and rare earth metals within limits from 0.1 mg to 5 mg.
Although the addition of only one metal is sufficient it is clear that addition of several metals of the above mentioned list may also be convenient.
TABLE 2
D E Materials Range Ex. Range Ex. Argon 10 to 40 torrs 20 10 to 40 torrs 20 Sodium iodide 25 to 100 mg 50 40 to 80 mg 60 Thallium iodide 2 to 5 mg 3 Indium iodide 0.1 to 5 mg 0.3 Cesium iodide 0.5 to 10 mg 5 0.5 to 10 mg 5 Mercury iodide 5 to 10 mg 6 5 to 20 mg 10 Mercury 180 180 Yttrium 0.1 to 2 mg 1 0.1 to 2 mg 1 Scandium 0.5 to 5 mg 2
Table 2 shows two examples of fillings for high-pressure mercury-vapor lamps designed to provide a power of 1,000 watts, the burner diameter being 22 mm and the spacing between electrodes of 100 mm.
TABLE 3
F G Materials Range Ex. Range Ex. Argon 10 to 40 torrs 20 10 to 40 torrs 20 Sodium iodide 50 to 200 mg 140 50 to 200 mg 160 Thallium iodide 3 to 10 mg 5 Indium iodide 1 to 10 mg 5 Cesium iodide 1 to 10 mg 5 Mercury iodide 5 to 20 mg 10 10 to 40 mg 20 Mercury 320 320 Yttrium 0.2 to 5 mg 2 0.5 to 5 mg 2 Scandium 1 to 5 mg 3
Table 3 shows two examples of fillings for high-pressure mercury-vapor lamps designed for providing a power of 2,000 watts, the burner diameter being 30 mm and the spacing between electrodes of 145 mm.
It has been observed that the high-pressure mercury-vapor lamps manufactured according to the present invention have an operating voltage which is increased by less than two volts per thousand operation hours, which constitutes a substantial improvement with respect to prior art lamps of which the operation voltage was increasing by eight to fifteen volts per thousand operation hours.
While the present invention has been described in relation to specific embodiments, it is clear that the composition is not limited to the examples and that other variations and modifications may be made within the scope of the invention as set forth in the appended claims.
1. Field of the Invention
The present invention relates to improvements in high-pressure mercury-vapor electric discharge lamps and, more particularly, to lamps of this type which contain, in addition to mercury, alkali metal halogenides.
2. Description of the Prior Art
In these lamps, luminous radiation is generally produced either by very concentrated intense emission rays, as in the case of metals such as thallium, sodium and indium, or by very numerous rays spread over the entire spectrum as in the case of rare-earth elements or transition metals such as scandium, hafnium, thorium. The lamp is generally formed of an outer glass envelope and an inner high pressure discharge tube of vitreous material such as quartz.
The metals are usually introduced into the lamp in the form of halogenides and, more particularly, in the form of iodides which are highly volatile halogenides. One of the most used iodides is sodium iodide which, due to its low vapor pressure at the lamp operation temperature, is gaseous within the discharge region of the inner tube and liquid about the tube walls. Due to a diffusion phenomenon through the tube walls, the sodium iodide is decomposed and the sodium leaves the inner area resulting in an enrichment of iodine inside the tube, which restrains the electric discharge phenomenon causing an increased voltage across electrode terminals and, after a few hundreds of operation hours, renders lighting difficult.
One of the solutions adopted to slow the sodium diffusion is in locating the inner tube within an area of an outer envelope filled with a neutral gas such as nitrogen, at adequate pressure. Thus lamps are obtained in which the electrode terminal voltage increases less rapidly with time.
SUMMARY OF THE INVENTION
It is therefore, an object of the present invention to provide an improved high-pressure mercury-vapor electric discharge lamp containing an alkali-metal halogenide, by including additional materials to maintain the operating voltage substantially constant with time.
In such lamps the alkali-metal halogenides, in particular, may be sodium halogenide and the added materials may include additions of mercury halogenide, and a halogenide of easily ionizable metal and a further metal which may be in decreasing order of preference: yttrium, thorium, magnesium, hafnium, aluminum and rare-earth metals.
The metal halogenides introduced into high-pressure mercury-vapor lamps are generally iodides and the metal halogenide which is added in the present invention is cesium iodide, cesium having a low ionization energy.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following Table 1 shows three examples A, B and C of fillings for high-pressure mercury-vapor lamps having a power of 400 watts obtained with an inner tube having a diameter of 18 mm and a spacing between electrodes of 50 mm. In each example, the left-side column shows the possible pressure and weight limits in torrs (millimeters of mercury) and in milligrams, respectively, of the filling materials and the right-side column the values used in an embodiment. The left hand column lists the various materials in the compositions. ##SPC1##
The example A relates to addition of yttrium and cesium iodide with mercury iodide in a high-pressure mercury-vapor lamp already containing iodides of sodium (having a characteristic yellow color), of thallium (having a green color) and of indium (having a blue color).
The example B relates to addition of yttrium and cesium iodide with mercury iodide in a high-pressure mercury-vapor lamp already containing sodium iodide and scandium, which have a very close color spectrum.
In the example C, compared with the example B, yttrium is replaced by thorium and magnesium.
Yttrium may also be replaced by hafnium, aluminum and rare earth metals within limits from 0.1 mg to 5 mg.
Although the addition of only one metal is sufficient it is clear that addition of several metals of the above mentioned list may also be convenient.
TABLE 2
D E Materials Range Ex. Range Ex. Argon 10 to 40 torrs 20 10 to 40 torrs 20 Sodium iodide 25 to 100 mg 50 40 to 80 mg 60 Thallium iodide 2 to 5 mg 3 Indium iodide 0.1 to 5 mg 0.3 Cesium iodide 0.5 to 10 mg 5 0.5 to 10 mg 5 Mercury iodide 5 to 10 mg 6 5 to 20 mg 10 Mercury 180 180 Yttrium 0.1 to 2 mg 1 0.1 to 2 mg 1 Scandium 0.5 to 5 mg 2
Table 2 shows two examples of fillings for high-pressure mercury-vapor lamps designed to provide a power of 1,000 watts, the burner diameter being 22 mm and the spacing between electrodes of 100 mm.
TABLE 3
F G Materials Range Ex. Range Ex. Argon 10 to 40 torrs 20 10 to 40 torrs 20 Sodium iodide 50 to 200 mg 140 50 to 200 mg 160 Thallium iodide 3 to 10 mg 5 Indium iodide 1 to 10 mg 5 Cesium iodide 1 to 10 mg 5 Mercury iodide 5 to 20 mg 10 10 to 40 mg 20 Mercury 320 320 Yttrium 0.2 to 5 mg 2 0.5 to 5 mg 2 Scandium 1 to 5 mg 3
Table 3 shows two examples of fillings for high-pressure mercury-vapor lamps designed for providing a power of 2,000 watts, the burner diameter being 30 mm and the spacing between electrodes of 145 mm.
It has been observed that the high-pressure mercury-vapor lamps manufactured according to the present invention have an operating voltage which is increased by less than two volts per thousand operation hours, which constitutes a substantial improvement with respect to prior art lamps of which the operation voltage was increasing by eight to fifteen volts per thousand operation hours.
While the present invention has been described in relation to specific embodiments, it is clear that the composition is not limited to the examples and that other variations and modifications may be made within the scope of the invention as set forth in the appended claims.