CA1316975C - Pulsed metal halide salt source - Google Patents
Pulsed metal halide salt sourceInfo
- Publication number
- CA1316975C CA1316975C CA000586186A CA586186A CA1316975C CA 1316975 C CA1316975 C CA 1316975C CA 000586186 A CA000586186 A CA 000586186A CA 586186 A CA586186 A CA 586186A CA 1316975 C CA1316975 C CA 1316975C
- Authority
- CA
- Canada
- Prior art keywords
- metal halide
- light source
- region
- light
- halide salt
- 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.)
- Expired - Fee Related
Links
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
- H01J61/827—Metal halide arc lamps
Abstract
ABSTRACT OF THE DISCLOSURE
The present invention is directed to a new type of colored light source especially well suited for use as a signal and/or navigational aid. The source is also adaptable to many other applications requiring momentary flashes of a particular color of light.
The mercury-free, pulsed metal halide light source of the present invention comprises in combination:
(a) a light transmissive glass vacuum outer jacket;
(b) a light transmissive glass arc tube disposed within said outer jacket;
(c) emissive material comprising at least one metal halide salt and an inert gas; and (d) an anode and a cathode, disposed within said arc tube, forming a gap therebetween;
said cathode being completely covered by said metal halide salt.
The present invention is directed to a new type of colored light source especially well suited for use as a signal and/or navigational aid. The source is also adaptable to many other applications requiring momentary flashes of a particular color of light.
The mercury-free, pulsed metal halide light source of the present invention comprises in combination:
(a) a light transmissive glass vacuum outer jacket;
(b) a light transmissive glass arc tube disposed within said outer jacket;
(c) emissive material comprising at least one metal halide salt and an inert gas; and (d) an anode and a cathode, disposed within said arc tube, forming a gap therebetween;
said cathode being completely covered by said metal halide salt.
Description
13~97~
~.
: , 2~0 : ~ ~ Conventlonal~ metal halide~ discharge light sources : typically~ comprise ~ a: fused silica ~ube: with two electrodes, a; rare gas for starti~g, a charge of mercury, and a fill comprising one or more metal halide :salts, generally the iodides.
In ~ ~;he;ir~ operation, a starting voltage of about ; 300V~ is applied~ :across ~the elec~rode gap causing the conten~s~ of ~the~ arc tube~to vaporize, resulting in a high tempe~rature,::hlgh~pressure,:wall stabilized arc in 30~ ~;a gas~,~consisting:principally of mercury vapor, ionized:
:metal atoms and iodine:molecules. ~ ;
Th e output sp e ct rum ( i ~./ the col or of the discharge) of metal ~halide discharge lamp~ consists , ,: : ~ : , ~ ; ~
~316~7~
predominantly of the spectrum of the added metal halides. Color output for such lamps is tailored by varying the types of metal halides added to the arc tube. See for e~ample, Waymouth, "Electric Discharge Lamps," Chapter 8, MIT Press, (1971).
The present invention represents a radical departure from the pree~isting technology, namely the discovery of a metal halide arc lamp that does not employ mercury, the source cell of which can be formed from con~entional glass, and which operates at near ambient temperature by means of a short duration, high pulse current.
The present invention is directed to a metal halide arc lamp which generates a flashing colored, preferably monochromatic, light. The applications for such a source include signal and warning lights as well as applications in the visual aids field.
~As described in greater detail herein below, ;~ the lamp of an embodiment of the present invention can be easily fabricated from conventional borosilicate or alkali resistant glass (e.g., Pyrex R3 and requires no au~iliary heating, even though the emissive material, i.e., the metal halide fill, is contained as a stable salt.
According to the present invention there is provided a pulsed metal halide arc discharge light source comprising a light-transmissive envelope hermetically enclosing an interior; an anode and a cathode passing through said envelope and protruding into said interior, the internal terminations of said anode and cathode being spaced apart; an inert gas and an emissive ~aterial within said interior, said emissive material covering said cathode such that there is a minimum gap between said internal ~i~termination o~ said anode and the surface of said `~~emissive material, said emissive material including at least one recrystallized metal halide salt, the ~;
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7 ~
temperature of said emissive material being less than one hundred degrees Centigrade during an application of a short duration electrical pulse across said anode and cathode; and an arc discharge positioned between said anode and cathode during said application of said electrical pulse, said arc discharge including first, second, and third regions emitting colored light, said first region being plume-like and adjacent said metal halide salt, the color of the light emitted from said first region being substantially determined by said metal halide salt, said second region being a central core positioned between said first region and said anode, the color of the emitted light of said second region being substantially determined by said inert gas, said third region surrounding said second region, the color of said third region being determined by said inert gas and said metal halide salt.
BRIEF DESCRIPTIOD OF THE DRAWI~GS
Figure 1 illustrates a preferred configuration for the arc tube light source prepared according to one embodiment of the present invention.
Figure 2 represents the color output of an arc tube light source when lithium bromide is pulsed in accordance with one embodiment of the present invention.
Figure 3 illustrates one means for adjusting the color output of an arc source prepared in accordance with the teachings of one embodiment of the present invention, namely, the use of a coated reflector shield~
DETAI~ED DESCRIPTION OF THE PREFERRED EMBODIME~TS
A schematical drawing of the preferred arc tube light source of the present invention is shown in Figure 1.
As illustrated, the source o radiant energy in the lamp of one embodiment of the present invention comprises a light ~j ,5 ,~
.
4 ~ ~ 7 ~
transmissive radiating chamber 10, which is preferably cylindrical, being defined in preferred embodiments by a tubular section of thin walled Pyrex R glass.
Opposing electrodes 12, preferably formed of tungsten, are sealed into either end of the chamber 14, : preferably using a vacuum sealing technique.
The emissive fill 16, comprises one or more metal halide salts, preferably alkali metal iodides or bromides, and this fill may be added to the radiating . chamber 10 after one of the electrodes 12 has been sealed into the end of the chamber 14.
In preferred embodiments, this fill is added as described, e., before the addition of a second electrode 12, thus providing a source ~ith no auxiliary tubing on the side. An inert gas, preferably argon, is then added to the source, and the second electrode 12 is sealed in place 140 Such a construction is referred . 20 to as "tipless" which is generally not possible in traditional metal halide lamps.
An outer glass jacket (not illustrated) may be added to provide for convenient handling of the lamp.
While not wishing to be bound by ~heory, or to unduly limit the scope of the present invention, it has been discovered that a pulsed metal halide source : prepared~ according to the present invention must have ~: 30~ its cathode (negative (-) electrode~ completely covered with the metal halide salt.
. ~
The metal halide salt is typically added as a granular or powdered fill which is t~ereafter melted ::
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;
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and recrystallized around and over the cathode.
In practice, a natural gas torch is used to lightly heat up the cathode end of the cell during ~abrication, causi~g melting of the metal halide salt around the cathode. Upon cooling, a solid mass of recrystallized (or fused) metal halide salt surrounds the cathode.
It has been discovered that the cathode should be covered by at least about 0.5 mm of solidified metal halide salt. Lesser amounts will still work (providing the cathode is covered), but this represents a best estimate for the minimum amount of coverage required for consistently good per~ormance. The gap remaining between the anode and the top of the salt layer should range from about 3 to 10 mm for conventional arc tubes (about 10-15 mm x 3 mmj.
' ~
Unlike other metal halide sources, it has surprisingly ~een discovered that changes in the spatial orientation of the present source does not adversely impact the light output. In conv~ntional metal halide lamps, a change from vertical operation to horizontal operation dramatically reduces the light output. On the other hand, with the lamps of the presént invention, either spatial orientation, vertical or h~ri~ontal, may be employed, each with satisfactory light output.
~; 30~ In pre~erred~ operations, a 1-2 kV potential with a time duration of a few microseconds (e.g., 1-100, preferably 1-50, most preferably 1-10) is initially applied across the electrodes, which readily produces a low level of ionization of the argon and subsequent .
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glow in the arc tube between the bare anode and the salt covering the cathode. About a 300-400 volt potential is sustained across the gap between the anode and the salt during the high current pulse.
Figure 2 typifies what is observed when a cell prepared in accordance with the teachings of the present invention, and containing a preferred salt, lithium bromide, is pulsed in accordance with the above described procedures.
As shown in Figure 2, the arc discharge is comprised essentially of three regions. The first plume-like region 22 occurs immediately above lithium bromide salt 24 which covers the cathode. Region 22 emits red light from the lithium vapor and from the lithium bromide salt 24. The second region 18 is a central core occurring between region 22 and the anode. Region 18 emits bluish-white light. The third region 20 surrounds region 18 and emits bluish-green light mi~ed with red.
If the arc is sustained, e~, allowed to drain high levels of current (e.g., 0.5 - 1.0 amp), ioniæed argon atoms are accelerated toward the bottom electrode .
since that electrode is preferably the cathode. Many collisions between the argon and metal halide salt occur :`
as the argon migrates toward the bottom electrode. Some of these collisions will produce dissociation of the metal rom the halide and eventual excitation of the metal. The resulting emission from the Qxcited metal provides the desired effect, i.e., colored light output.
As shown in Figure 2, such a metal rich region forms slightly above the salt level. However, even within the salt region the metal can ~ecome excited so that emission is observed everywhere around the bottom ~, , " ~ ~
- 7 _ ~3~ ~ 9 7 ~
electrode. For the preferred embodiment described herein the lithium generates its resonance radiation at 610 and 670 nanometers wavelength, which is sbserved as a red color by the human eye.
In addition to the preferred lithium bromide emissive source, other metal halide salt systems such as sodium iodide and thallium iodide have been tested, and they exhibit a similar effect.
The glow from the argon can be masked leaving visible only the emission from the salt region.
A mask 26 can be prepared from a reflector or a coated shield, which would be used to reflect energy bac~ into the cell's interior as depicted in Figure 3.
Since the pressure of the argon is only a fraction of an atmosphere and the preferred electrode gap is less than about 1 cm, the glow transfers into an arc within several microseconds.
The preferred source has several advantageous fabrication features including:
~25 The cell material can be Pyrex R or alkali resis~ant glass which i5 more easily worked than fused silica which requires hi~h heat for forming. Mor~over, the~geometry of the cell apparently does not affect the performance. Ellipsoidal, tubular, and spherical shaped ~cells have been utilized all with success.
The availability of alternate types of glass results from the fact that the source is operated at ,.
l ~1 " 1~
.
~' .:
~31697~
near ambient tempera~ures, i.e., less than about 100C, rather than the approx. 800C, which i~
typical of most metal halide high in1:ensity discharge sources.
The absence of a tip-off greatly improves the light distribution of the source in the present lamp. The source also has fairly uniform light output in the horizontal plane.
Since the majority of the discharge energy is confined to a columinar zone including the salt region, the radiating region is effectively cylindrical so that no preforming of the glass is necessary; merely a ~; 15 straight section of glass tubing is sufficient.
The energy conservation with this source should be improved over an externally heated system since bulk vaporization of the s21t will not be necessary. The celI i5 basically cold.
Electrode maintenance should be improved since a diffuse contact at the cathode is guaranteed because of the salt coverage. In effect the salt disperses the 2s plasma flow and~ provides many current paths to the electrode~. Normally a gas arc will ~terminate on the càthode as a high current density spot which increases ; the local temperature o~ the eIectrod and contributes to erosion of the electrode.
Embodiments of the present invention have been described in detail. However, it will be appreciated that those skilled in the art, upon consideration of the present disclosure, may make .,~, : ,, ' ' ~3169~
_ 9 _ modifications and improvements on ~hi~ invention and ~till be within the scope and ~pirit of this invention as ~et forth in the following claims.
:~ :
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:
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. : : :
~.
: , 2~0 : ~ ~ Conventlonal~ metal halide~ discharge light sources : typically~ comprise ~ a: fused silica ~ube: with two electrodes, a; rare gas for starti~g, a charge of mercury, and a fill comprising one or more metal halide :salts, generally the iodides.
In ~ ~;he;ir~ operation, a starting voltage of about ; 300V~ is applied~ :across ~the elec~rode gap causing the conten~s~ of ~the~ arc tube~to vaporize, resulting in a high tempe~rature,::hlgh~pressure,:wall stabilized arc in 30~ ~;a gas~,~consisting:principally of mercury vapor, ionized:
:metal atoms and iodine:molecules. ~ ;
Th e output sp e ct rum ( i ~./ the col or of the discharge) of metal ~halide discharge lamp~ consists , ,: : ~ : , ~ ; ~
~316~7~
predominantly of the spectrum of the added metal halides. Color output for such lamps is tailored by varying the types of metal halides added to the arc tube. See for e~ample, Waymouth, "Electric Discharge Lamps," Chapter 8, MIT Press, (1971).
The present invention represents a radical departure from the pree~isting technology, namely the discovery of a metal halide arc lamp that does not employ mercury, the source cell of which can be formed from con~entional glass, and which operates at near ambient temperature by means of a short duration, high pulse current.
The present invention is directed to a metal halide arc lamp which generates a flashing colored, preferably monochromatic, light. The applications for such a source include signal and warning lights as well as applications in the visual aids field.
~As described in greater detail herein below, ;~ the lamp of an embodiment of the present invention can be easily fabricated from conventional borosilicate or alkali resistant glass (e.g., Pyrex R3 and requires no au~iliary heating, even though the emissive material, i.e., the metal halide fill, is contained as a stable salt.
According to the present invention there is provided a pulsed metal halide arc discharge light source comprising a light-transmissive envelope hermetically enclosing an interior; an anode and a cathode passing through said envelope and protruding into said interior, the internal terminations of said anode and cathode being spaced apart; an inert gas and an emissive ~aterial within said interior, said emissive material covering said cathode such that there is a minimum gap between said internal ~i~termination o~ said anode and the surface of said `~~emissive material, said emissive material including at least one recrystallized metal halide salt, the ~;
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7 ~
temperature of said emissive material being less than one hundred degrees Centigrade during an application of a short duration electrical pulse across said anode and cathode; and an arc discharge positioned between said anode and cathode during said application of said electrical pulse, said arc discharge including first, second, and third regions emitting colored light, said first region being plume-like and adjacent said metal halide salt, the color of the light emitted from said first region being substantially determined by said metal halide salt, said second region being a central core positioned between said first region and said anode, the color of the emitted light of said second region being substantially determined by said inert gas, said third region surrounding said second region, the color of said third region being determined by said inert gas and said metal halide salt.
BRIEF DESCRIPTIOD OF THE DRAWI~GS
Figure 1 illustrates a preferred configuration for the arc tube light source prepared according to one embodiment of the present invention.
Figure 2 represents the color output of an arc tube light source when lithium bromide is pulsed in accordance with one embodiment of the present invention.
Figure 3 illustrates one means for adjusting the color output of an arc source prepared in accordance with the teachings of one embodiment of the present invention, namely, the use of a coated reflector shield~
DETAI~ED DESCRIPTION OF THE PREFERRED EMBODIME~TS
A schematical drawing of the preferred arc tube light source of the present invention is shown in Figure 1.
As illustrated, the source o radiant energy in the lamp of one embodiment of the present invention comprises a light ~j ,5 ,~
.
4 ~ ~ 7 ~
transmissive radiating chamber 10, which is preferably cylindrical, being defined in preferred embodiments by a tubular section of thin walled Pyrex R glass.
Opposing electrodes 12, preferably formed of tungsten, are sealed into either end of the chamber 14, : preferably using a vacuum sealing technique.
The emissive fill 16, comprises one or more metal halide salts, preferably alkali metal iodides or bromides, and this fill may be added to the radiating . chamber 10 after one of the electrodes 12 has been sealed into the end of the chamber 14.
In preferred embodiments, this fill is added as described, e., before the addition of a second electrode 12, thus providing a source ~ith no auxiliary tubing on the side. An inert gas, preferably argon, is then added to the source, and the second electrode 12 is sealed in place 140 Such a construction is referred . 20 to as "tipless" which is generally not possible in traditional metal halide lamps.
An outer glass jacket (not illustrated) may be added to provide for convenient handling of the lamp.
While not wishing to be bound by ~heory, or to unduly limit the scope of the present invention, it has been discovered that a pulsed metal halide source : prepared~ according to the present invention must have ~: 30~ its cathode (negative (-) electrode~ completely covered with the metal halide salt.
. ~
The metal halide salt is typically added as a granular or powdered fill which is t~ereafter melted ::
,., .,,, ,, , . , . ~
;
~3~9~
and recrystallized around and over the cathode.
In practice, a natural gas torch is used to lightly heat up the cathode end of the cell during ~abrication, causi~g melting of the metal halide salt around the cathode. Upon cooling, a solid mass of recrystallized (or fused) metal halide salt surrounds the cathode.
It has been discovered that the cathode should be covered by at least about 0.5 mm of solidified metal halide salt. Lesser amounts will still work (providing the cathode is covered), but this represents a best estimate for the minimum amount of coverage required for consistently good per~ormance. The gap remaining between the anode and the top of the salt layer should range from about 3 to 10 mm for conventional arc tubes (about 10-15 mm x 3 mmj.
' ~
Unlike other metal halide sources, it has surprisingly ~een discovered that changes in the spatial orientation of the present source does not adversely impact the light output. In conv~ntional metal halide lamps, a change from vertical operation to horizontal operation dramatically reduces the light output. On the other hand, with the lamps of the presént invention, either spatial orientation, vertical or h~ri~ontal, may be employed, each with satisfactory light output.
~; 30~ In pre~erred~ operations, a 1-2 kV potential with a time duration of a few microseconds (e.g., 1-100, preferably 1-50, most preferably 1-10) is initially applied across the electrodes, which readily produces a low level of ionization of the argon and subsequent .
,' '~
~ 3 ~
glow in the arc tube between the bare anode and the salt covering the cathode. About a 300-400 volt potential is sustained across the gap between the anode and the salt during the high current pulse.
Figure 2 typifies what is observed when a cell prepared in accordance with the teachings of the present invention, and containing a preferred salt, lithium bromide, is pulsed in accordance with the above described procedures.
As shown in Figure 2, the arc discharge is comprised essentially of three regions. The first plume-like region 22 occurs immediately above lithium bromide salt 24 which covers the cathode. Region 22 emits red light from the lithium vapor and from the lithium bromide salt 24. The second region 18 is a central core occurring between region 22 and the anode. Region 18 emits bluish-white light. The third region 20 surrounds region 18 and emits bluish-green light mi~ed with red.
If the arc is sustained, e~, allowed to drain high levels of current (e.g., 0.5 - 1.0 amp), ioniæed argon atoms are accelerated toward the bottom electrode .
since that electrode is preferably the cathode. Many collisions between the argon and metal halide salt occur :`
as the argon migrates toward the bottom electrode. Some of these collisions will produce dissociation of the metal rom the halide and eventual excitation of the metal. The resulting emission from the Qxcited metal provides the desired effect, i.e., colored light output.
As shown in Figure 2, such a metal rich region forms slightly above the salt level. However, even within the salt region the metal can ~ecome excited so that emission is observed everywhere around the bottom ~, , " ~ ~
- 7 _ ~3~ ~ 9 7 ~
electrode. For the preferred embodiment described herein the lithium generates its resonance radiation at 610 and 670 nanometers wavelength, which is sbserved as a red color by the human eye.
In addition to the preferred lithium bromide emissive source, other metal halide salt systems such as sodium iodide and thallium iodide have been tested, and they exhibit a similar effect.
The glow from the argon can be masked leaving visible only the emission from the salt region.
A mask 26 can be prepared from a reflector or a coated shield, which would be used to reflect energy bac~ into the cell's interior as depicted in Figure 3.
Since the pressure of the argon is only a fraction of an atmosphere and the preferred electrode gap is less than about 1 cm, the glow transfers into an arc within several microseconds.
The preferred source has several advantageous fabrication features including:
~25 The cell material can be Pyrex R or alkali resis~ant glass which i5 more easily worked than fused silica which requires hi~h heat for forming. Mor~over, the~geometry of the cell apparently does not affect the performance. Ellipsoidal, tubular, and spherical shaped ~cells have been utilized all with success.
The availability of alternate types of glass results from the fact that the source is operated at ,.
l ~1 " 1~
.
~' .:
~31697~
near ambient tempera~ures, i.e., less than about 100C, rather than the approx. 800C, which i~
typical of most metal halide high in1:ensity discharge sources.
The absence of a tip-off greatly improves the light distribution of the source in the present lamp. The source also has fairly uniform light output in the horizontal plane.
Since the majority of the discharge energy is confined to a columinar zone including the salt region, the radiating region is effectively cylindrical so that no preforming of the glass is necessary; merely a ~; 15 straight section of glass tubing is sufficient.
The energy conservation with this source should be improved over an externally heated system since bulk vaporization of the s21t will not be necessary. The celI i5 basically cold.
Electrode maintenance should be improved since a diffuse contact at the cathode is guaranteed because of the salt coverage. In effect the salt disperses the 2s plasma flow and~ provides many current paths to the electrode~. Normally a gas arc will ~terminate on the càthode as a high current density spot which increases ; the local temperature o~ the eIectrod and contributes to erosion of the electrode.
Embodiments of the present invention have been described in detail. However, it will be appreciated that those skilled in the art, upon consideration of the present disclosure, may make .,~, : ,, ' ' ~3169~
_ 9 _ modifications and improvements on ~hi~ invention and ~till be within the scope and ~pirit of this invention as ~et forth in the following claims.
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Claims (28)
1. A pulsed metal halide arc discharge light source comprising:
(a) a light-transmissive envelope hermetically enclosing an interior;
(b) an anode and a cathode passing through said envelope and protruding into said interior, the internal terminations of said anode and cathode being spaced apart;
(c) an inert gas and an emissive material within said interior, said emissive material covering said cathode such that there is a minimum gap between said internal termination of said anode and the surface of said emissive material, said emissive material including at least one recrystallized metal halide salt, the temperature of said emissive material being less than one hundred degrees Centigrade during an application of a short duration electrical pulse across said anode and cathode; and (d) an arc discharge positioned between said anode and cathode during said application of said electrical pulse, said arc discharge including first, second, and third regions emitting colored light, said first region being plume-like and adjacent said metal halide salt, the color of the light emitted from said first region being substantially determined by said metal halide salt, said second region being a central core positioned between said first region and said anode, the color of the emitted light of said second region being substantially determined by said inert gas, said third region surrounding said second region, the color of said third region being determined by said inert gas and said metal halide salt.
(a) a light-transmissive envelope hermetically enclosing an interior;
(b) an anode and a cathode passing through said envelope and protruding into said interior, the internal terminations of said anode and cathode being spaced apart;
(c) an inert gas and an emissive material within said interior, said emissive material covering said cathode such that there is a minimum gap between said internal termination of said anode and the surface of said emissive material, said emissive material including at least one recrystallized metal halide salt, the temperature of said emissive material being less than one hundred degrees Centigrade during an application of a short duration electrical pulse across said anode and cathode; and (d) an arc discharge positioned between said anode and cathode during said application of said electrical pulse, said arc discharge including first, second, and third regions emitting colored light, said first region being plume-like and adjacent said metal halide salt, the color of the light emitted from said first region being substantially determined by said metal halide salt, said second region being a central core positioned between said first region and said anode, the color of the emitted light of said second region being substantially determined by said inert gas, said third region surrounding said second region, the color of said third region being determined by said inert gas and said metal halide salt.
2. A light source as described in claim 1 wherein the light emitted from said light source is colored light.
3. A light source as described in claim 1 wherein the duration of said electrical pulse is approximately one hundred microseconds or less.
4. A light source as described in claim 3 wherein the duration of said electrical pulse is approximately fifty microseconds or less.
5. A light source as described in claim 4 wherein the duration of said electrical pulse is approximately ten microseconds or less.
6. A light source as described in claim 1 wherein the electrical potential across said anode and cathode during application of said electrical pulse is approximately two thousand volts or less.
7. A light source as described in claim 6 wherein said electrical potential is approximately one thousand volts or greater.
8. A light source as described in claim 1 wherein said minimum gap is approximately ten millimeters or less.
9. A light source as described in claim 8 wherein said minimum gap is approximately three millimeters or greater.
10. A light source as described in claim 1 wherein said envelope is alkali-resistant glass.
11. A light source as described in claim 10 wherein said envelope is borosilicate glass.
12. A light source as described in claim 1 wherein said recrystallized metal halide salt is selected from the group consisting of an alkali metal chloride, an alkali metal iodide, and an alkali metal bromide.
13. A light source as described in claim 12 wherein said recrystallized metal halide salt is lithium bromide.
14. A light source as described in claim 1 wherein said recrystallized metal halide salt is selected from the group consisting of the chlorides, iodides, and bromides of lithium, sodium, zinc, and thallium.
15. A light source as described in claim 2 wherein the light emitted from said light source is red.
16. A light source as described in claim 1 wherein said inert gas is argon.
17. A light source as described in claim 1 wherein said envelope includes a body and two opposed ends, said body having substantially a straight cylindrical shape.
18. A light source as describe in claim 1 wherein said envelope is tipless.
19. A pulsed metal halide arc discharge light source comprising:
(a) a light-transmissive envelope hermetically enclosing an interior;
(b) an anode and a cathode passing through said envelope and protruding into said interior, the internal terminations of said anode and cathode being spaced apart;
(c) an inert gas and an emissive material within said interior, said emissive material covering said cathode such that there is a minimum gap between said internal termination of said anode and the surface of said emissive material, said emissive material including at least one recrystallized metal halide salt, the temperature of said emissive material being less than one hundred degrees Centigrade during an application of a short duration electrical pulse across said anode and cathode;
(d) an arc discharge positioned between said anode and cathode during said application of said electrical pulse, said arc discharge including first, second, and third regions emitting colored light, said first region being plume-like and adjacent said metal halide salt, the color of the light emitted from said first region being substantially determined by said metal halide salt, said second region being a central core positioned between said first region and said anode, the color of the emitted light of said second region being substantially determined by said inert gas, said third region surrounding said second region, the color of said third region being determined by said inert gas and said metal halide salt;
(e) a light-transmissive outer jacket enclosing said envelope; and (f) means within said outer jacket for providing electrical energy from an external source to said anode and cathode.
(a) a light-transmissive envelope hermetically enclosing an interior;
(b) an anode and a cathode passing through said envelope and protruding into said interior, the internal terminations of said anode and cathode being spaced apart;
(c) an inert gas and an emissive material within said interior, said emissive material covering said cathode such that there is a minimum gap between said internal termination of said anode and the surface of said emissive material, said emissive material including at least one recrystallized metal halide salt, the temperature of said emissive material being less than one hundred degrees Centigrade during an application of a short duration electrical pulse across said anode and cathode;
(d) an arc discharge positioned between said anode and cathode during said application of said electrical pulse, said arc discharge including first, second, and third regions emitting colored light, said first region being plume-like and adjacent said metal halide salt, the color of the light emitted from said first region being substantially determined by said metal halide salt, said second region being a central core positioned between said first region and said anode, the color of the emitted light of said second region being substantially determined by said inert gas, said third region surrounding said second region, the color of said third region being determined by said inert gas and said metal halide salt;
(e) a light-transmissive outer jacket enclosing said envelope; and (f) means within said outer jacket for providing electrical energy from an external source to said anode and cathode.
20. A light source as described in claim 19 wherein during application of said electrical pulse a first light emission emanates from said inert gas and a second light emission emanates from said emissive material and said light source further includes means within said outer jacket for substantially masking said first light emission from emanating through said outer jacket.
21. A light source as described in claim 20 wherein said mask means surrounds a portion of said envelope such that said first light emission is reflected by said mask means back toward said envelope.
22. A method of constructing a mercury-free, pulsed metal halide arc lamp comprising the steps of:
(a) forming a radiating chamber from glass;
(b) sealing an electrode into one end of said radiating chamber;
(c) adding emissive material in the form of a metal halide salt to said chamber, sufficient to cover said electrode and positioned above the electrode to facilitate an arc discharge;
(d) heating said metal halide salt to a sufficient temperature as to melt around said electrode, thereafter allowing the same to cool and solidify;
(e) sealing an additional electrode in the open end of said cylindrical chamber; and (f) adding sufficient inert gas to support mercury-free, pulsed ionization;
(g) wherein a plume-like region of the arc discharge occurs adjacent and above the metal halide salt, the region of the arc discharge emitting colored light, the color being determined almost exclusively by the metal halide salt.
(a) forming a radiating chamber from glass;
(b) sealing an electrode into one end of said radiating chamber;
(c) adding emissive material in the form of a metal halide salt to said chamber, sufficient to cover said electrode and positioned above the electrode to facilitate an arc discharge;
(d) heating said metal halide salt to a sufficient temperature as to melt around said electrode, thereafter allowing the same to cool and solidify;
(e) sealing an additional electrode in the open end of said cylindrical chamber; and (f) adding sufficient inert gas to support mercury-free, pulsed ionization;
(g) wherein a plume-like region of the arc discharge occurs adjacent and above the metal halide salt, the region of the arc discharge emitting colored light, the color being determined almost exclusively by the metal halide salt.
23. The method of claim 22, wherein the cylindrical radiating chamber is formed from thin walled borosilicate glass.
24. The method of claim 22, wherein the opposing electrodes are formed of tungsten.
25. The method of claim 24, wherein the electrodes are sealed into each end of the chamber using a vacuum sealing technique.
26. The method of claim 22, wherein the metal halide salt is recrystallized around one of the electrodes.
27. The method of claim 22, wherein the metal halide salt is fused around one of the electrodes.
28. The method of claim 22, wherein during the lamp operation, the covered electrode is the cathode.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US13540587A | 1987-12-18 | 1987-12-18 | |
| US135,405 | 1987-12-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1316975C true CA1316975C (en) | 1993-04-27 |
Family
ID=22467964
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000586186A Expired - Fee Related CA1316975C (en) | 1987-12-18 | 1988-12-16 | Pulsed metal halide salt source |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0320933A3 (en) |
| CA (1) | CA1316975C (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH03152852A (en) * | 1989-11-08 | 1991-06-28 | Matsushita Electric Works Ltd | Discharge lamp of high brightness and electrodeless discharge lamp device |
| DE102008013607B3 (en) * | 2008-03-11 | 2010-02-04 | Blv Licht- Und Vakuumtechnik Gmbh | Mercury-free metal halide high pressure discharge lamp |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA577060A (en) * | 1959-06-02 | W. L. Cumming Harry | Electric discharge lamps | |
| US3622217A (en) * | 1969-06-30 | 1971-11-23 | Xerox Corp | Light producing system |
| US3840767A (en) * | 1973-08-23 | 1974-10-08 | Gen Electric | Selective spectral output metal halide lamp |
| US4389201A (en) * | 1979-03-12 | 1983-06-21 | General Electric Company | Method of manufacturing a lamp |
-
1988
- 1988-12-15 EP EP88120992A patent/EP0320933A3/en not_active Withdrawn
- 1988-12-16 CA CA000586186A patent/CA1316975C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0320933A2 (en) | 1989-06-21 |
| EP0320933A3 (en) | 1990-05-23 |
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| Date | Code | Title | Description |
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| MKLA | Lapsed |