CA1116684A - High-pressure metal vapour discharge lamp with auxiliary starting electrode - Google Patents
High-pressure metal vapour discharge lamp with auxiliary starting electrodeInfo
- Publication number
- CA1116684A CA1116684A CA000317566A CA317566A CA1116684A CA 1116684 A CA1116684 A CA 1116684A CA 000317566 A CA000317566 A CA 000317566A CA 317566 A CA317566 A CA 317566A CA 1116684 A CA1116684 A CA 1116684A
- Authority
- CA
- Canada
- Prior art keywords
- strip
- discharge tube
- shaped coating
- discharge lamp
- pressure metal
- 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
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J61/00—Gas-discharge or vapour-discharge lamps
- H01J61/02—Details
- H01J61/54—Igniting arrangements, e.g. promoting ionisation for starting
- H01J61/541—Igniting arrangements, e.g. promoting ionisation for starting using a bimetal switch
- H01J61/544—Igniting arrangements, e.g. promoting ionisation for starting using a bimetal switch and an auxiliary electrode outside the vessel
Landscapes
- Discharge Lamps And Accessories Thereof (AREA)
- Vessels And Coating Films For Discharge Lamps (AREA)
Abstract
ABSTRACT:
The invention relates to an electrical high-pressure metal vapour discharge lamp provided with a discharge tube containing sodium and mercury as well as xenon. In the operating condition of the lamp the xenon pressure in the discharge tube is approximately 1600 torr.
In accordance with the invention the dis-charge tube is provided with a narrow external strip-shaped coating extending along substantially the entire length of the discharge tube. This strip-shaped coat-ing consists of 80% Molybdenum, 10% A1203 and 10% CaO
by volume. The strip-shaped coating acts as the starting electrode of the discharge tube.
The invention relates to an electrical high-pressure metal vapour discharge lamp provided with a discharge tube containing sodium and mercury as well as xenon. In the operating condition of the lamp the xenon pressure in the discharge tube is approximately 1600 torr.
In accordance with the invention the dis-charge tube is provided with a narrow external strip-shaped coating extending along substantially the entire length of the discharge tube. This strip-shaped coat-ing consists of 80% Molybdenum, 10% A1203 and 10% CaO
by volume. The strip-shaped coating acts as the starting electrode of the discharge tube.
Description
8~
The invention relates to an electrical high-pressure metal vapour discharge lamp comprising an elongate discharge tube provided near each of its two ends with a respective internal main electrode, the wall of the discharge tube consisting substantially wholly of aluminium oxide, a strip-shaped coating being present over at least a portion of the outer surface of the wall of the discharge tube, this coating containing a first electrically conductive elementary material as well as a second material counteracting evaporation of the first material, and in which at least part of the `
first material is in direct contact with the aluminium oxide, the strip-shaped coating being fastened over sub-stantially its whole length to the discharge tube and forming in use, part of a starting auxiliary device for starting a discharge between the main electrodes.
A prior art electrical high-pressure metal vapour discharge lamp of the type defined above is, for example, disclosed in British Patent 1,421,406 - Egyesult 20 Izzolampa - April 4, 1973. A drawback of that known high-pressure metal vapour discharge lamp is that, for promoting the starting of a discharge between the main electrodes, the strip-shaped wall coating is connected to an internal auxiliary electrode of the discharge tube.
This requires an additional electric feed-through through the wall of the discharge tube.
~3 ~
166~
22,9 78 2 ~HN.~9~1 It is an object of the invention to provide a lamp of the type defined in the preamlle in which the strip-shaped wall coating, provided on the outer side of the discharge tube wa1l, is the auxiliary electrode oP the discharge tube, but that this auxiliary electrode does not substantially intercept visible light generated in the discharge tube.
An electrical high-pressure metal vapour discha~ge lamp according to the invention comprising al7 elongate discharge tube provided near each of its two ends with a respective internal main electrode, the wall of the discharge tube consisting substa.ntially wholly of aluminium oxide, a strip-shaped coating oeing present .~ over at least a portion of the outer surface of the dis-charge tube wa]l, this coating containing a first elec-trically conductive elementary material as well as a second material counteracting evaporation of the first material of that coating and in which at least part of the fi.rst material is in direct contact with the alun1iniulr.
oxide, th.e strip-shaped coating being fastened over substantially its whole length to the discharge tube arld forming in use, part of a starting auxiliary device for starting a discharge between the main electrodes, i5 characterized in t.hat the strip-shaped coating extends .5 along substantially the whole path between the rnain electrodes, and in. that this strip-shaped coating has a width smaller tha~ 0.5 mm over at least 9O~ of its length.
An advantage of this lamp is that the strip-shaped coating is here an external auxiliary electrode. The narrow width, over the greater portion of the ].ength, of thi.s auxiliary electrode implies that the auxiliary electrode intercepts the l,.gh~ generated in rhe di.scharge tube to a verv sma:Ll extent on7y.
The strip-shaped coating ~nay have a width exceeding O.5 mm for a short 3ength, for exanple wllere there is a connect ng termiIlal f`or e3.ectrically connecting thc strip shaped coating to thc circuit of the lamp 22 . 9 . 7~ - 3 PHN. 8981 The strip-shaped coating of an e]ectrical high-pressure metal vapour discharge lamp accordillg to the invention consists, for example~ of a solid metal conductor, the second mat0rial being in the form of a protective coating protecting the so]id conductor.
In an embodiment of an elecbrical high-pressure metal vapour discharge lamp according to the invention the first material of the strip-shaped coating consists for 16 to 90% by volume of an element ~rom the group molybdenum, tungsten, tantalum, niobium and carbon, and the second material of the strip-shaped coating consists of one or more oxides which, at a temperature of 1500 Kelvin, have vapour pressures below 10 torr.
An advantage of this embodiment is that more of the first material can be included in the strip-shaped coating than would be possible in the case of a soiid strip on the discharge tube. In addition, it is a good electrically-conducting material. The following should be noted by way of explanation. With the narrow width of not more than 0.5 mm of the strip-shaped coating, a sufficiently low ohmic resistance thereof per running centimetre of length can - in the case of a solid metal -only be realised with a fairly thick layer of that metal.
However, a very thick layer results in a poor adhesion f that metal to the discharge tube wall which mainly consists of aluminium oxide. This is caused by differences in the coefficients of expansion. By also including in the strip-shaped coating oxides which have a low vapour pressure at 1500 Kelvin, a sufficiently low ohmic re-3o sistance of the strip-shaped coati.rlg - which also remains low hecausc the evaporation during life of the lamp is relatively low - can be combined with a p~oper adhesion to the discharge tube wall.
In an improvement of a lamp according to 3S the above-mentioned embodiment, the first matariai of the strip-shaped coating is molybdenum or carbon, this first material being ur~iformly distributed in the second material of the strip-shaped coating. An advantage oi` this 68~
22.9.78 4 PHN.89~1 i.mprovement is that a .1.ow degree of evaporation c~n be oomb ned with a high electrical conductivity of the strip-shaped coa.tiIlg.
In a further improvement OI' that lamp the strip-shaped coating consists, by volume~ of approximately ~0% Molybdenum ~ 1 Oc/o Al203 ~ 10% CaO.
With such a strip-.shaped coating it is possible to obtain, next to the above-mentioned advantages of a low evaporation and a high electrical conductivity, a very good adhesion to the di.scharge tube wall.
In a further embodiment of a h.igh-pressure metal vapour discharge lamp accordingto the invention, the first materiai of the strip-shaped coating is molyb-~ denum and the second material is tullgsten~ the tungsten being applied as a top coating o~rer the molybdenum.
An advantage of this embodiment is that the strip-shaped coating can be applied in a si.mple manner to the dis-charge tube. This is done by, for example, vacuum deposition or by means of a sputteri.ng techrique, for example b~r magnetron sputtering.
The di.scharge lampis, for exaMple, a high--pressure sodium vapour discharge lamp the discharge tube of which also contains a starting gas,-for e~ample xenon, at a filling pressure of 1ess than 20 torr;
In an embodiment of an electrical high-pressure metal vapour discharge lamv according to thc invention~ whi.ch is implemented as a high-pressure sodium vapour discharge lamp, the discharge tube contains sodium ~e na~
~ and xenon, the filling pressure Or the sodium cxceeding 3G 50 torr, the c.ircumference of a transverse cross-section through the disch3.rge tube being between 10 and 40 mm.
An advantage of thi.s embodi.ment is that it may furnish a lamp which combines a high lumillous effi.cacy with a relatively low starting voltage and wherein the inter-3S ceptioll of ].ight by +he strip--shaped coating is ve.ry small only.
A l~igh-pressure dlscharge lamp according to the in~rerlti.on may comprise a discharge tube, 6~4 22.9.78 5 PHN.898l the strip-shaped coating of which is noi electricall.y connected to the lamp circuit. In that case the strip-shaped coating has a floating potential in use, preferably, however, in a high-pressure metal vapour discharge lamp according to the invention, the strip-shaped coating is clectrically connected to one of the main electrodes of the discharge tube. A.n advantage of this is that during the starting procedure of the lamp the difference in potential between the strip-shaped coating - which then operates as an auxiliary electrode - and the main electrode of the discharge tube not connected thereto can be substantially equal to the nmains voltage. As a rule this promotes the creation of ions and electrons in the .~............ discharge tube which facilitates the creation of a dis-charge between the main electrodes of the discharge tube.
.ll this implies that the mini.mum voltage between the maln electrodes for starting a discharge between these electrodss i5 then relatively low.
Some erllb~di.ments of lamps according to the invent:io~ wi.ll now be further explai.ned with refer-ence to a drawing i.n which:
Figure 1 shows an eievational view, partly in Gross-secti.on, of a high-pressure sodium va.pour discharge lamp according to the invention;
The invention relates to an electrical high-pressure metal vapour discharge lamp comprising an elongate discharge tube provided near each of its two ends with a respective internal main electrode, the wall of the discharge tube consisting substantially wholly of aluminium oxide, a strip-shaped coating being present over at least a portion of the outer surface of the wall of the discharge tube, this coating containing a first electrically conductive elementary material as well as a second material counteracting evaporation of the first material, and in which at least part of the `
first material is in direct contact with the aluminium oxide, the strip-shaped coating being fastened over sub-stantially its whole length to the discharge tube and forming in use, part of a starting auxiliary device for starting a discharge between the main electrodes.
A prior art electrical high-pressure metal vapour discharge lamp of the type defined above is, for example, disclosed in British Patent 1,421,406 - Egyesult 20 Izzolampa - April 4, 1973. A drawback of that known high-pressure metal vapour discharge lamp is that, for promoting the starting of a discharge between the main electrodes, the strip-shaped wall coating is connected to an internal auxiliary electrode of the discharge tube.
This requires an additional electric feed-through through the wall of the discharge tube.
~3 ~
166~
22,9 78 2 ~HN.~9~1 It is an object of the invention to provide a lamp of the type defined in the preamlle in which the strip-shaped wall coating, provided on the outer side of the discharge tube wa1l, is the auxiliary electrode oP the discharge tube, but that this auxiliary electrode does not substantially intercept visible light generated in the discharge tube.
An electrical high-pressure metal vapour discha~ge lamp according to the invention comprising al7 elongate discharge tube provided near each of its two ends with a respective internal main electrode, the wall of the discharge tube consisting substa.ntially wholly of aluminium oxide, a strip-shaped coating oeing present .~ over at least a portion of the outer surface of the dis-charge tube wa]l, this coating containing a first elec-trically conductive elementary material as well as a second material counteracting evaporation of the first material of that coating and in which at least part of the fi.rst material is in direct contact with the alun1iniulr.
oxide, th.e strip-shaped coating being fastened over substantially its whole length to the discharge tube arld forming in use, part of a starting auxiliary device for starting a discharge between the main electrodes, i5 characterized in t.hat the strip-shaped coating extends .5 along substantially the whole path between the rnain electrodes, and in. that this strip-shaped coating has a width smaller tha~ 0.5 mm over at least 9O~ of its length.
An advantage of this lamp is that the strip-shaped coating is here an external auxiliary electrode. The narrow width, over the greater portion of the ].ength, of thi.s auxiliary electrode implies that the auxiliary electrode intercepts the l,.gh~ generated in rhe di.scharge tube to a verv sma:Ll extent on7y.
The strip-shaped coating ~nay have a width exceeding O.5 mm for a short 3ength, for exanple wllere there is a connect ng termiIlal f`or e3.ectrically connecting thc strip shaped coating to thc circuit of the lamp 22 . 9 . 7~ - 3 PHN. 8981 The strip-shaped coating of an e]ectrical high-pressure metal vapour discharge lamp accordillg to the invention consists, for example~ of a solid metal conductor, the second mat0rial being in the form of a protective coating protecting the so]id conductor.
In an embodiment of an elecbrical high-pressure metal vapour discharge lamp according to the invention the first material of the strip-shaped coating consists for 16 to 90% by volume of an element ~rom the group molybdenum, tungsten, tantalum, niobium and carbon, and the second material of the strip-shaped coating consists of one or more oxides which, at a temperature of 1500 Kelvin, have vapour pressures below 10 torr.
An advantage of this embodiment is that more of the first material can be included in the strip-shaped coating than would be possible in the case of a soiid strip on the discharge tube. In addition, it is a good electrically-conducting material. The following should be noted by way of explanation. With the narrow width of not more than 0.5 mm of the strip-shaped coating, a sufficiently low ohmic resistance thereof per running centimetre of length can - in the case of a solid metal -only be realised with a fairly thick layer of that metal.
However, a very thick layer results in a poor adhesion f that metal to the discharge tube wall which mainly consists of aluminium oxide. This is caused by differences in the coefficients of expansion. By also including in the strip-shaped coating oxides which have a low vapour pressure at 1500 Kelvin, a sufficiently low ohmic re-3o sistance of the strip-shaped coati.rlg - which also remains low hecausc the evaporation during life of the lamp is relatively low - can be combined with a p~oper adhesion to the discharge tube wall.
In an improvement of a lamp according to 3S the above-mentioned embodiment, the first matariai of the strip-shaped coating is molybdenum or carbon, this first material being ur~iformly distributed in the second material of the strip-shaped coating. An advantage oi` this 68~
22.9.78 4 PHN.89~1 i.mprovement is that a .1.ow degree of evaporation c~n be oomb ned with a high electrical conductivity of the strip-shaped coa.tiIlg.
In a further improvement OI' that lamp the strip-shaped coating consists, by volume~ of approximately ~0% Molybdenum ~ 1 Oc/o Al203 ~ 10% CaO.
With such a strip-.shaped coating it is possible to obtain, next to the above-mentioned advantages of a low evaporation and a high electrical conductivity, a very good adhesion to the di.scharge tube wall.
In a further embodiment of a h.igh-pressure metal vapour discharge lamp accordingto the invention, the first materiai of the strip-shaped coating is molyb-~ denum and the second material is tullgsten~ the tungsten being applied as a top coating o~rer the molybdenum.
An advantage of this embodiment is that the strip-shaped coating can be applied in a si.mple manner to the dis-charge tube. This is done by, for example, vacuum deposition or by means of a sputteri.ng techrique, for example b~r magnetron sputtering.
The di.scharge lampis, for exaMple, a high--pressure sodium vapour discharge lamp the discharge tube of which also contains a starting gas,-for e~ample xenon, at a filling pressure of 1ess than 20 torr;
In an embodiment of an electrical high-pressure metal vapour discharge lamv according to thc invention~ whi.ch is implemented as a high-pressure sodium vapour discharge lamp, the discharge tube contains sodium ~e na~
~ and xenon, the filling pressure Or the sodium cxceeding 3G 50 torr, the c.ircumference of a transverse cross-section through the disch3.rge tube being between 10 and 40 mm.
An advantage of thi.s embodi.ment is that it may furnish a lamp which combines a high lumillous effi.cacy with a relatively low starting voltage and wherein the inter-3S ceptioll of ].ight by +he strip--shaped coating is ve.ry small only.
A l~igh-pressure dlscharge lamp according to the in~rerlti.on may comprise a discharge tube, 6~4 22.9.78 5 PHN.898l the strip-shaped coating of which is noi electricall.y connected to the lamp circuit. In that case the strip-shaped coating has a floating potential in use, preferably, however, in a high-pressure metal vapour discharge lamp according to the invention, the strip-shaped coating is clectrically connected to one of the main electrodes of the discharge tube. A.n advantage of this is that during the starting procedure of the lamp the difference in potential between the strip-shaped coating - which then operates as an auxiliary electrode - and the main electrode of the discharge tube not connected thereto can be substantially equal to the nmains voltage. As a rule this promotes the creation of ions and electrons in the .~............ discharge tube which facilitates the creation of a dis-charge between the main electrodes of the discharge tube.
.ll this implies that the mini.mum voltage between the maln electrodes for starting a discharge between these electrodss i5 then relatively low.
Some erllb~di.ments of lamps according to the invent:io~ wi.ll now be further explai.ned with refer-ence to a drawing i.n which:
Figure 1 shows an eievational view, partly in Gross-secti.on, of a high-pressure sodium va.pour discharge lamp according to the invention;
2; ~igure 2 shows a cross-section not to scale - througll a variant of a discharge tube for the lamp of Figure 1.
In Figure 1 reference numeral 1 denotes a dischargc tube whose wall consi.sts mainly o~ densely sintered alumilllum oxide. This tube is located in an outcr bulb 2. ~.efsrence numeral 3 denotes a base of the lanlp. Tlle di.scharge tubc 1 comprises two internal n1ain electxodes 4 and 5, respectively, located near the ends of this discharge -tubs. V~a a feed-throu~h 6 the main electrode 4 is connected. to a metal conductor 7 cornected to a pole wire 8 which is cu.rved arouMd the discharge tube 1. Thi.s form of the pole wire 8 has the ad~ran.tage that annoyi.ng shadows are avoided.
. ~ .
6~4 Pole wire 8 is electrically connected to a contact of the base 3 of the lamp. An extended portion 9 of the pole wire 8 serves, together with a support 10, for supporting and centring the discharge tube 1 in the outer bulb 2.
Vla a tubular feed-through 11 the main electrode 5 is mechanically fastened to a metal conductor 12. The elec-trical connection is effected via a metal conductor 13.
The other end of the conductor 12 is connected to a fur-ther contact in the base 3 of the lamp.
In addition, the discharge tube is provided with a strip-shaped external auxiliary electrode 20 in the form of a local coating on the outer surface of the discharge tube 1. The auxiliary electrode 20 extends over substantially the whole distance between the main electrodes 4 and 5. The auxiliary electrode is approx-imately 0.2 mm wide, its composition by volume is: a mix-ture of 80% Molybdenum, 10% A12O3 and 10% CaO. The two mentioned oxides A12O3 and CaO have, at a temperature of 20 1500 Kelvin, a vapour pressure below 10 6 Torr. Near the main electrode 5 the discharge tube 1 comprises a conduct-ing nickel sleeve 21 which also extends over the auxiliary electrode 20 and is in electrical contact therewith. A
strip 22, also of nickel, connects the sleeve 21 to an electrode of a capacitor 23, disposed in the space between the discharge tube 1 and the outer bulb 2. The other elec-trode of capacitor 23 is constituted by a portion of the metal conductor 13 which provides the electrical connection between the main electrode 5 and the conductor 12.
The discharge tube 1 contains both sodium and mercury as well as xenon. The xenon pressure at 300 Kelvin is approximately 200 torr. The space between the discharge tube 1 and the outer bulb 2 is evacuated.
The described lamp is, for example ignited by means of a starter (not shown) provided with a thyris-35 tor, for example as disclosed in Canadian Patent 896,070 -Moerkene - March 21, 1972 (PHN 3905).
In the operating condition of the lamp shown in Figure 1 the lamp is connected through an 22.9-7~ 7 PHN.8981 inductive stabilisation impedance of approximately 0.3 Henry to an a.c. mains supply of approximately 220 Volts, 50 Hertz. Further details of the described lamp are included in the following table. The temperature of the coldest spot in ~e discharge tube 1 is - in the operating condition of the lamp according to the invention-approximately 1000 Kelvin. A sodium vapour pressure in the discharge tube 1 of approximate]y 130 torr corresponds therewith. The average temperature within the discharge tube 1 in the operating condition of the lamp is approxi-mately 2400 Kelvin. The average temperature of the wall of the discharge tube is approximately 1500 Kelvin.
At this temperature of 1500 Kelvin the vapour pressure '- of the cxides of the strip-shaped auxiliary electrode is - as already mentioned above - small. So there is only a low degree ~f evaporation of said oxides.
Lamp according to the invention . _~ . _.
Power (in watts) 150 ~ _ Operating voltage (in volts) 100 _ _ .
Inside diameter of the discharge tube (in mm) 4.5 _ _ . .
Circumference of cross-section (in mm) of the discharge tube approx. 20 _ .
Main electrode spacing (in mm) 63 Weight of the amalgam (in mgram) 10 . _ .
l~eight ratio mercur~r/
~odium 2.7 _ _ __ ~
Xellon pressure cold ~
(in t;orr) 1 200 Xenon pressure during operation (in torr) ¦ 1600 Luminous e~ficacy (lumens/watt 11$
.__ ~ _ ~
8~
22.9.7~ 8 P~lN.~981 The voltage required between the main electrodes 4 and 5 for starting the discharge is in the present case approxiMately 2 k~olts.
Without the strip 20 the voltage requirecl between the main electrodes 4 and 5 - for igniting the discharge - would be much greater, namely: approximately 6 kVolts.
The strip-shaped coating 20 of Figure 1 is approximately 35 micron3 thick. Its ohmic resistance per running centimetre is approximately 0.1 kOllm.
The strip-shaped coating 20 is applied to the wall of the discharge tube by means of a pen.
For this purpose this pen is first dipped into a sus -~ pension of 80% molybdenum powder with 10% aluminium oxide and 10% calcium oxide in butyl acetate. After the coating has been applied a firing operation is performed at 1~00 l~elvin for 30 minutes in a reducing atmosphere.
This results in a proper adhesion to the wall of the discharge tu~e 1 over the full length of the strip-shaped coating 20.
In a case where the first material ofthe strip-shaped coating is carbon, that strip-shaped coating can, for exarnple, also be applied to the dis-charge twbe by means of a pen.
~5 Also other processes of reali~ing the strip~shaped coating on the wall of the discharge tube are conceivable.
Figure 2 shows a perpendicular CI'OSS-section 100 of a second c~ischarge tube~ enlarged three ti~les relative to that of the discharge tube 1 o~
Figure 1. Al50 tube 100 consists mainly of aluminium oxide. A ~trip-shaped molybdenum coating 101 is provided on tube 100. A tungsten top coating 102 is app:Lied ove-~coating 101. The full width of the strip is approxi-~5 Mately 0.2 ,nm. To indicate tl1e various ]ayers~ the stripis not dra-.~n to scale in ~igure 2.
A31 advantagc of` the described strip-shaped coatings in a la~np a-cording to the iI1ventio 6~
22.9,78 9 PHN.8981 -as opposed to starting wires - is that the strip-shaped coatings are always very close to the main electrode path without requiring an addltiorlal measure such as subjecting it to a tenqile load - as is the case with starting wires.
2~
In Figure 1 reference numeral 1 denotes a dischargc tube whose wall consi.sts mainly o~ densely sintered alumilllum oxide. This tube is located in an outcr bulb 2. ~.efsrence numeral 3 denotes a base of the lanlp. Tlle di.scharge tubc 1 comprises two internal n1ain electxodes 4 and 5, respectively, located near the ends of this discharge -tubs. V~a a feed-throu~h 6 the main electrode 4 is connected. to a metal conductor 7 cornected to a pole wire 8 which is cu.rved arouMd the discharge tube 1. Thi.s form of the pole wire 8 has the ad~ran.tage that annoyi.ng shadows are avoided.
. ~ .
6~4 Pole wire 8 is electrically connected to a contact of the base 3 of the lamp. An extended portion 9 of the pole wire 8 serves, together with a support 10, for supporting and centring the discharge tube 1 in the outer bulb 2.
Vla a tubular feed-through 11 the main electrode 5 is mechanically fastened to a metal conductor 12. The elec-trical connection is effected via a metal conductor 13.
The other end of the conductor 12 is connected to a fur-ther contact in the base 3 of the lamp.
In addition, the discharge tube is provided with a strip-shaped external auxiliary electrode 20 in the form of a local coating on the outer surface of the discharge tube 1. The auxiliary electrode 20 extends over substantially the whole distance between the main electrodes 4 and 5. The auxiliary electrode is approx-imately 0.2 mm wide, its composition by volume is: a mix-ture of 80% Molybdenum, 10% A12O3 and 10% CaO. The two mentioned oxides A12O3 and CaO have, at a temperature of 20 1500 Kelvin, a vapour pressure below 10 6 Torr. Near the main electrode 5 the discharge tube 1 comprises a conduct-ing nickel sleeve 21 which also extends over the auxiliary electrode 20 and is in electrical contact therewith. A
strip 22, also of nickel, connects the sleeve 21 to an electrode of a capacitor 23, disposed in the space between the discharge tube 1 and the outer bulb 2. The other elec-trode of capacitor 23 is constituted by a portion of the metal conductor 13 which provides the electrical connection between the main electrode 5 and the conductor 12.
The discharge tube 1 contains both sodium and mercury as well as xenon. The xenon pressure at 300 Kelvin is approximately 200 torr. The space between the discharge tube 1 and the outer bulb 2 is evacuated.
The described lamp is, for example ignited by means of a starter (not shown) provided with a thyris-35 tor, for example as disclosed in Canadian Patent 896,070 -Moerkene - March 21, 1972 (PHN 3905).
In the operating condition of the lamp shown in Figure 1 the lamp is connected through an 22.9-7~ 7 PHN.8981 inductive stabilisation impedance of approximately 0.3 Henry to an a.c. mains supply of approximately 220 Volts, 50 Hertz. Further details of the described lamp are included in the following table. The temperature of the coldest spot in ~e discharge tube 1 is - in the operating condition of the lamp according to the invention-approximately 1000 Kelvin. A sodium vapour pressure in the discharge tube 1 of approximate]y 130 torr corresponds therewith. The average temperature within the discharge tube 1 in the operating condition of the lamp is approxi-mately 2400 Kelvin. The average temperature of the wall of the discharge tube is approximately 1500 Kelvin.
At this temperature of 1500 Kelvin the vapour pressure '- of the cxides of the strip-shaped auxiliary electrode is - as already mentioned above - small. So there is only a low degree ~f evaporation of said oxides.
Lamp according to the invention . _~ . _.
Power (in watts) 150 ~ _ Operating voltage (in volts) 100 _ _ .
Inside diameter of the discharge tube (in mm) 4.5 _ _ . .
Circumference of cross-section (in mm) of the discharge tube approx. 20 _ .
Main electrode spacing (in mm) 63 Weight of the amalgam (in mgram) 10 . _ .
l~eight ratio mercur~r/
~odium 2.7 _ _ __ ~
Xellon pressure cold ~
(in t;orr) 1 200 Xenon pressure during operation (in torr) ¦ 1600 Luminous e~ficacy (lumens/watt 11$
.__ ~ _ ~
8~
22.9.7~ 8 P~lN.~981 The voltage required between the main electrodes 4 and 5 for starting the discharge is in the present case approxiMately 2 k~olts.
Without the strip 20 the voltage requirecl between the main electrodes 4 and 5 - for igniting the discharge - would be much greater, namely: approximately 6 kVolts.
The strip-shaped coating 20 of Figure 1 is approximately 35 micron3 thick. Its ohmic resistance per running centimetre is approximately 0.1 kOllm.
The strip-shaped coating 20 is applied to the wall of the discharge tube by means of a pen.
For this purpose this pen is first dipped into a sus -~ pension of 80% molybdenum powder with 10% aluminium oxide and 10% calcium oxide in butyl acetate. After the coating has been applied a firing operation is performed at 1~00 l~elvin for 30 minutes in a reducing atmosphere.
This results in a proper adhesion to the wall of the discharge tu~e 1 over the full length of the strip-shaped coating 20.
In a case where the first material ofthe strip-shaped coating is carbon, that strip-shaped coating can, for exarnple, also be applied to the dis-charge twbe by means of a pen.
~5 Also other processes of reali~ing the strip~shaped coating on the wall of the discharge tube are conceivable.
Figure 2 shows a perpendicular CI'OSS-section 100 of a second c~ischarge tube~ enlarged three ti~les relative to that of the discharge tube 1 o~
Figure 1. Al50 tube 100 consists mainly of aluminium oxide. A ~trip-shaped molybdenum coating 101 is provided on tube 100. A tungsten top coating 102 is app:Lied ove-~coating 101. The full width of the strip is approxi-~5 Mately 0.2 ,nm. To indicate tl1e various ]ayers~ the stripis not dra-.~n to scale in ~igure 2.
A31 advantagc of` the described strip-shaped coatings in a la~np a-cording to the iI1ventio 6~
22.9,78 9 PHN.8981 -as opposed to starting wires - is that the strip-shaped coatings are always very close to the main electrode path without requiring an addltiorlal measure such as subjecting it to a tenqile load - as is the case with starting wires.
2~
Claims (7)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electrical high-pressure metal vapour discharge lamp comprising an elongate discharge tube provided near each of its two ends with a respective internal main electrode, the wall of the discharge tube consisting substantially wholly of aluminium oxide, a strip-shaped coating being present over at least a portion of the outer surface of the wall of the dis-charge tube, this coating containing a first elec-trically conductive elementary material as well as a second material counteracting evaporation of the first material and in which at least part of the first material is in direct contact with the aluminium oxide, the strip-shaped coating being fastened over substantially its whole length to the discharge tube and forming, in use, part of a starting auxiliary device for starting a discharge between the main electrodes, characterized in that the strip-shaped coating extends along substantially the whole path between the main electrodes, and in that this strip-shaped coating has a width smaller than 0.5 mm over at least 90% of its length.
2. An electrical high-pressure metal vapour discharge lamp as claimed in claim 1, characterized in that the first material of the strip-shaped coating consists for 16 to 90% by volume of an element from the group molybdenum, tungsten, tantalum, niobium and carbon, and the second material of that strip-shaped coating consists of one or more oxides which, at a tem-perature of 1500 Kelvin, have vapour pressures below 10-6 torr.
3. An electrical high-pressure metal vapour discharge lamp as claimed in Claim 2, characterized in that the first material is molybdenum or carbon, this first material being uniformly distributed in the second material of the strip-shaped coating.
4. An electrical high-pressure metal vapour discharge lamp as claimed in Claim 3, characterized in that the strip-shaped coating consists of substantially 80% Molybdenum + 10% Al2O3 + 10% CaO by volume.
5. An electrical high-pressure metal vapour discharge lamp as claimed in Claim 1, characterized in that the first material is molybdenum and the second material is tungsten, the tungsten being applied as a top coating over the molybdenum.
6. An electrical high-pressure metal vapour discharge lamp as claimed in any of Claims 1, 2 or 5, the lamp being a high-pressure sodium vapour discharge lamp, the discharge tube containing sodium and xenon, the filling pressure of the xenon exceeding 50 torr, characterized in that the circumference of a transverse cross-section through the discharge tube is between 10 mm and 40 mm.
7. An electrical high-pressure metal vapour discharge lamp as claimed in any of Claims 1, 2 or 5, characterized in that the strip-shaped coating is elec-trically connected to one of the main electrodes of the discharge tube.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL7713950 | 1977-12-16 | ||
| NL7713950A NL7713950A (en) | 1977-12-16 | 1977-12-16 | ELECTRIC HIGH PRESSURE METAL VAPOR DISCHARGE LAMP. |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1116684A true CA1116684A (en) | 1982-01-19 |
Family
ID=19829774
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000317566A Expired CA1116684A (en) | 1977-12-16 | 1978-12-07 | High-pressure metal vapour discharge lamp with auxiliary starting electrode |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0002848B1 (en) |
| JP (2) | JPS5488676A (en) |
| CA (1) | CA1116684A (en) |
| DE (1) | DE2860920D1 (en) |
| HU (1) | HU180274B (en) |
| NL (1) | NL7713950A (en) |
Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1167973A (en) * | 1980-10-02 | 1984-05-22 | Joseph M. Proud | Low energy starting aid for high intensity discharge lamps |
| ES2128387T3 (en) * | 1992-10-08 | 1999-05-16 | Koninkl Philips Electronics Nv | HIGH PRESSURE DISCHARGE LAMP. |
| DE19631188A1 (en) * | 1996-08-02 | 1998-02-05 | Heraeus Kulzer Gmbh | Discharge lamp arrangement |
| EP1279187B1 (en) * | 2000-04-26 | 2004-07-14 | Cornell Research Foundation, Inc. | Lamp utilizing fiber for enhanced starting field |
| US6456005B1 (en) * | 2000-10-31 | 2002-09-24 | General Electric Company | Materials and methods for application of conducting members on arc tubes |
| US6563265B1 (en) * | 2000-11-06 | 2003-05-13 | General Electric Company | Applying prealloyed powders as conducting members to arc tubes |
| US6897615B2 (en) | 2001-11-01 | 2005-05-24 | Axcelis Technologies, Inc. | Plasma process and apparatus |
| KR20060076773A (en) * | 2003-09-17 | 2006-07-04 | 코닌클리즈케 필립스 일렉트로닉스 엔.브이. | Gas discharge lamp |
| WO2009030265A1 (en) * | 2007-08-29 | 2009-03-12 | Osram Gesellschaft mit beschränkter Haftung | Lamp having directly applied starting aid device |
| EP2301063B1 (en) | 2008-07-10 | 2013-10-23 | Koninklijke Philips N.V. | High-pressure sodium vapor discharge lamp with hybrid antenna |
| US10325769B2 (en) | 2014-12-12 | 2019-06-18 | Koninklijke Philips N.V. | Gas-discharge lamp for a vehicle headlamp |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2542345A (en) * | 1948-08-16 | 1951-02-20 | Gen Electric | Electric discharge lamp |
| DE1764866A1 (en) * | 1968-08-21 | 1971-11-18 | Patra Patent Treuhand | Arrangement for restarting a high-pressure mercury vapor discharge lamp at operating temperature with additives |
| US4065370A (en) * | 1975-11-18 | 1977-12-27 | The United States Of America As Represented By The Secretary Of The Army | Method of ion plating a thin metallic strip for flashlamp starting |
| US4047064A (en) * | 1976-06-16 | 1977-09-06 | Gte Sylvania Incorporated | Flash tube having enclosed trigger wire |
-
1977
- 1977-12-16 NL NL7713950A patent/NL7713950A/en not_active Application Discontinuation
-
1978
- 1978-12-04 EP EP19780200339 patent/EP0002848B1/en not_active Expired
- 1978-12-04 DE DE7878200339T patent/DE2860920D1/en not_active Expired
- 1978-12-07 CA CA000317566A patent/CA1116684A/en not_active Expired
- 1978-12-13 JP JP15324878A patent/JPS5488676A/en active Pending
- 1978-12-13 HU HUPI000654 patent/HU180274B/en not_active IP Right Cessation
-
1983
- 1983-02-28 JP JP2888783U patent/JPS58165849U/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58165849U (en) | 1983-11-04 |
| HU180274B (en) | 1983-02-28 |
| DE2860920D1 (en) | 1981-11-05 |
| NL7713950A (en) | 1979-06-19 |
| EP0002848A1 (en) | 1979-07-11 |
| EP0002848B1 (en) | 1981-08-05 |
| JPS5488676A (en) | 1979-07-13 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5990599A (en) | High-pressure discharge lamp having UV radiation source for enhancing ignition | |
| US4105910A (en) | Fluorescent lamp with an integral fail-safe and auxiliary-amalgam component | |
| CA1116684A (en) | High-pressure metal vapour discharge lamp with auxiliary starting electrode | |
| US3872340A (en) | High temperature lamp starting aid | |
| GB2072967A (en) | High intensity discharge lamp containing electronic starting aid | |
| US6456005B1 (en) | Materials and methods for application of conducting members on arc tubes | |
| US3716743A (en) | High-pressure metal-vapor discharge tube | |
| CA1163310A (en) | Thermal interruption switch for a gaseous discharge lamp auxiliary means | |
| US4651048A (en) | High pressure discharge lamp with arc tube heat shield | |
| US4316122A (en) | High pressure sodium vapor discharge lamp | |
| US2094647A (en) | Gaseous electric discharge device | |
| US7378797B2 (en) | Fluorescent lamp with conductive coating | |
| US4445069A (en) | Low-pressure discharge lamp | |
| US5680000A (en) | Reflective metal heat shield for metal halide lamps | |
| US2103033A (en) | Electron emissive electrode | |
| JPS62283543A (en) | Metallic vapor discharge lamp | |
| US4433271A (en) | High pressure discharge lamp | |
| US3325662A (en) | Metal vapor lamp having a heat reflecting coating of calcium pyrophosphate | |
| GB2026766A (en) | High-pressure sodium vapour discharge lamps | |
| US5218269A (en) | Negative glow discharge lamp having wire anode | |
| US2748308A (en) | Low-pressure arc-discharge tube supplied with direct current | |
| US4521716A (en) | High-pressure metal vapor discharge lamp | |
| RU2079183C1 (en) | High-pressure discharge tube | |
| CA1130361A (en) | High pressure sodium vapor discharge lamp with outside starting aid conductor | |
| US4745333A (en) | Auxiliary electrodes in fluorescent lamps for preventing irregular light flickering |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |