Electric lamp and discharge devices – With gas or vapor – Having electrode lead-in or electrode support sealed to...
Reexamination Certificate
2000-12-21
2002-07-30
Day, Michael H. (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Having electrode lead-in or electrode support sealed to...
C313S331000
Reexamination Certificate
active
06426592
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a high-voltage discharge lamp and, more particularly, to a high-voltage discharge lamp in which it is possible to prevent a quartz-glass bulb from bursting at the time of high-temperature thermal processing or at the time of operation.
BACKGROUND OF THE INVENTION
A high-voltage discharge lamp according to the prior art has a structure of the kind shown in
FIG. 6
, by way of example. Specifically, a high-voltage discharge lamp
1
includes a quartz-glass bulb
2
, which comprises an enlarged portion
21
that provides a light-emitting space and a seal portion
22
, and a pair of opposing electrodes (an anode
3
and cathode
4
) disposed within the glass bulb
2
. The anode
3
and cathode
4
are joined to the molybdenum foils
5
and
5
′, respectively, by means such as welding. Further, the molybdenum foils
5
,
5
′ are hermetically sealed within the bulb
2
at the seal portions
22
thereof. The enlarged portion
21
having the light-emitting space is filled with a discharge gas or the like.
Coils
6
,
6
′ comprising a material such as tungsten, tantalum or molybdenum are wound on the anode
3
and cathode
4
, respectively, on or near the joints between these electrodes and the molybdenum foils
5
,
5
′. By winding the coils
6
,
6
′ on the electrodes, stress applied to the glass bulb
2
owing to thermal expansion of the electrodes
3
,
4
can be mitigated even in a case where thermal processing is applied at high temperature or when the high-voltage lamp is operated. As a result, it is possible to prevent cracking at the portions where the electrodes
3
and
4
contact the glass bulb
2
.
SUMMARY OF THE DISCLOSURE
In the course of the investigations toward the present invention, it has turned out that there is much to be desired in the art.
When the coils are wound on the electrodes, however, protrusions are produced at the leading and trailing ends of the coils and the protrusions scratch the glass bulb. As a consequence, the glass bulb tends to crack. Further, when the coils are wound on the electrodes, a load (tensile force) acts upon the electrodes. If an electrode has a diameter of 0.6 to 0.8 mm, therefore, the electrode is deformed. It is technically very difficult to eliminate these protrusions and to prevent the deformation of the electrodes. Furthermore, a high-voltage discharge lamp of this kind cannot discharge stably and sufficiently stable brightness cannot be obtained.
Accordingly, an object of the present invention is to provide a high-voltage discharge lamp in which it is possible to eliminate the scratching of a quartz-glass bulb and the deformation of electrodes,and to mitigate thermal stress at the time of high-temperature thermal processing and high-voltage discharge operation, as a result of which the occurrence of cracking can be prevented and sufficiently stable brightness can be obtained.
As a result of extensive research, the inventor has devised a high-voltage discharge lamp in which the joint, as well as the vicinity thereof, between at least one electrode and molybdenum foil is covered by a cylindrical member the outer and/or inner surface of which has slits, or by a mesh-like member. The inventor has found that such a high-voltage discharge lamp will no longer have its quartz-glass bulb scratched, that the electrode will no longer be deformed because it is unnecessary for the joint or the vicinity thereof to have a hermetic seal, that it is possible to mitigate thermal stress at the time of high-temperature thermal processing or high-voltage discharge operation, thereby preventing the occurrence of cracking, and that sufficiently stable brightness is obtained. The present invention has been perfected on the basis of these findings.
Specifically, according to the present invention, the foregoing object is attained by providing a high-voltage discharge lamp having a bulb made of quartz glass, a pair of electrodes and molybdenum foils, wherein the pair of electrodes are arranged so as to oppose each other and are joined to respective ones of the molybdenum foils, and the bulb and molybdenum foils are hermetically sealed at seal portions of the bulb, characterized in that joints, as well as the vicinities thereof, between the pair of electrodes and the molybdenum foils are covered by cylindrical members having slits on an outer surface and/or an inner surface thereof.
According to another aspect of the present invention, the foregoing object is attained by providing a high-voltage discharge lamp having a bulb made of quartz glass, a pair of electrodes and molybdenum foils, wherein the pair of electrodes are arranged so as to oppose each other and are joined to respective ones of the molybdenum foils, and the bulb and molybdenum foils are hermetically sealed at seal portions of the bulb, characterized in that joints, as well as the vicinities thereof, between the pair of electrodes and the molybdenum foils are covered by mesh-like members.
REFERENCES:
patent: 4550269 (1985-10-01), Dixon
patent: 4749905 (1988-06-01), Mori et al.
patent: 5200669 (1993-04-01), Dixon et al.
patent: 5461277 (1995-10-01), Van Gennip et al.
Aoki Yasushi
Nishida Kazuhisa
Day Michael H.
McGinn & Gibb PLLC
NEC Corporation
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