Electric lamp and discharge devices: systems – Combined load device or load device temperature modifying... – Discharge device load
Reexamination Certificate
2001-12-12
2003-12-09
Wong, Don (Department: 2879)
Electric lamp and discharge devices: systems
Combined load device or load device temperature modifying...
Discharge device load
C315S082000, C315S057000, C315S363000, C313S625000, C313S624000, C313S623000, C313S626000
Reexamination Certificate
active
06661176
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-376947, filed on Dec. 12, 2000, the entire contents of which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a high pressure discharge lamp which is provided with a light-transmissive ceramic discharge vessel, a high pressure discharge lamp lighting circuit, and a luminaire therefor.
BACKGROUND OF THE INVENTION
A compact metal halide type high pressure discharge using a light-transmissive ceramics with a rated lamp power of about 20 W is described in co-pending Japanese Patent Application No. 2000-6994, which has been devised by the inventors of the present invention and filed Jan. 14, 2000 (hereinafter referred to as 6994 Prior Application).
The 6994 Prior Application refers to a high pressure discharge lamp having a light-transmissive ceramic discharge vessel which is provided with an enclosure defining a main discharge space and a pair of thin cylindrical portions integrated with both ends of the enclosure. A feed-conductor and an electrode which is mounted on the end of the feed-conductor are inserted in the slender thin cylindrical portions of the light-transmissive ceramic discharge vessel, and the thin cylindrical portion and the feed-conductor are sealed by using a ceramic sealing compound, which is the so-called a frit glass. A discharge agent comprised of a luminous metal halide, mercury, and rare gas is filled in the light-transmissive ceramic discharge vessel.
On the other hand, as such sealing configurations other than that as mentioned above, a high pressure discharge lamp wherein a sealing body which is made of cermet and a metal pipe acting as a current conductor are mounted on the end of a ceramic discharge tube (light-transmissive ceramic discharge vessel) has been disclosed in the Japanese Laid-Open Patent Application Hei 8-250068 (hereinafter referred to as Prior Art I). Moreover, a high pressure discharge lamp wherein a metal rod is inserted in such a metal pipe has been disclosed in the Japanese Laid-Open Patent Application Hei 10-334852 (hereinafter referred to as Prior Art II). Then, the metal pipe itself is fused to seal the ceramic discharge tube.
The Prior Art II discloses that when the high pressure discharge lamp disclosed in the Prior Art I is applied to the metal halide lamp, a metal rod is inserted in the metal pipe in order to reduce conductance inside of the metal pipe, so as to prevent some problems such as a reduction in luminous efficiency by the metal halogen flocculating in the metal pipe which becomes the lowest temperature portion during the operation of the lamp.
Further, a technique to fuse both of a metal lead to which an electrode rod is connected and the metal pipe by heat is shown in FIGS. 9 and 10 of the EP 982278A1 (hereinafter referred to as Prior Art Ill). Furthermore, it is disclosed that it has a coupling configuration which a first member made of ceramics or cermet and a second member made of a metal are connected together by interposing a main phase that contacts with the first member and an intermediate glass member that contact with the second member. Here, the intermediate glass member, that contact with the second member, is interposing between the second member and the main phase that has a porous skeleton configuration made from a sintered metal powders with an opening to which a glass phase is sunk.
Furthermore, a metal halide lamp wherein two ends of a light-transmissive ceramic arc tube are closed by ceramic plugs, through the ceramic plugs molybdenium exhaust pipes are fused, and electrode core rods are welded to inner ends of the ceramic plugs, is described in the Japanese Laid-Open Patent Application Hei 10-284004 (hereinafter referred to as Prior Art IV).
Furthermore, a technique to fuse by heat both of a metal lead to which an electrode rod is connected and the metal pipe is disclosed in FIGS. 9 and 10 of the EP 982278A1 (hereinafter referred to as Prior Art III).
In the high pressure discharge lamp discussed in the 6994 Prior Application, since the thin cylindrical portion becomes relatively longer in comparison to the enclosure, dead spaces tend to become broader in case of miniaturization.
On the contrary, the high pressure discharge lamps disclosed in the Prior Arts I, II and III are suitable for miniaturization in a point that it does not need a longer thin cylindrical portion. However, these Prior Arts do not mention to a relation between the luminous efficiency as a metal halide lamp, the lowest temperature portion to determine the luminous color and a sealing configuration.
That is the Prior Arts I-III are not able to rise the temperature of the lowest temperature portion by using w fusing configuration.
Under the circumstances, as a result of a meticulous research for such sealing configurations using a metal pipe, the inventors of the present invention have accomplished the present invention.
As a result of the research, it was proved that the Prior Arts I and II ware much the same. That is, in the high pressure discharge lamp disclosed in the Prior Art II, since the electrode is shorter than the metal pipe, there is left a gap, which becomes a capacity permitting aggregation of metal halide inside of the metal pipe. Then, if the electrode is extended in the metal pipe, the same effect as the case or the Prior Art II that the metal rode is inserted in the metal pipe is achieved.
Further, it is not mentioned about the causes or conditions for forming the lowest temperature portion in the metal pipe in the Prior Art II. According to the studies of the inventors, it was found that even in the high pressure discharge lamp disclosed in the Prior Art II, the lowest temperature portion might to be formed in the enclosure depending on the size of the light-transmissive ceramic discharge vessel and the metal pipe. Thus, it is proved that the techniques disclosed in the Prior Arts do not always achieve enough luminous efficiency, but also not suppress the difference of the luminous color at the time of changing the lighting direction.
Furthermore, the Prior Art IV is different from the present invention by that the Prior Art IV has a configuration of sealing the arc tube made of light-transmissive ceramics by a ceramic plug. The Prior Art IV is also different from the present invention in the inventive subject by that the Prior Art IV is subjected for preventing cracks of molybdenium exhaust pipe passing through the ceramic plug. On the other hand, the present invention is subjected for achieving a high luminous efficiency by raising a lowest temperature portion as described later. The Prior Art IV also has a problem that the exhaust pipe cannot be thickened because that the electrode is welded to a part of the inner wall of the exhaust pipe and thus placed eccentric from the axis of the arc tube.
SUMMARY OF THE INVENTION
The present invention has an object to improve the light-transmissive ceramic discharge vessel and the sealing configuration for providing a high pressure discharge lamp, high pressure discharge lamp lighting device, and a luminaire, which have an excellent luminous efficiency and/or a desired luminous color, and also, albeit compact, suppress the difference of the luminous color due to lighting directivity.
Further, the present invention has another object to provide a high pressure discharge lamp, a high pressure discharge lamp lighting device, and a luminaire which have longer life-expectancy.
A high pressure discharge lamp according to the first aspect of the invention is comprised of a light-transmissive ceramic discharge vessel with an envelope having a maximum outer diameter D
1
and open ends, a metal pipe disposed in each or the open ends, respectively each metal pipe having a first end, i.e., a top end fused, located in one of the open ends of the light-transmissive ceramic discharge vessel and a second end, i.e., a base end protruding from the light-transmissive ceramic discharge
Ashida Seiji
Honda Hisashi
Ishida Masazumi
Kashiwagi Takahito
Oku Shigemi
Pillsbury & Winthrop LLP
Toshiba Lighting & Technology Corporation
Vo Tuyet T.
Wong Don
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