Electric lamp and discharge devices – With gas or vapor – Having electrode exterior to envelope
Reexamination Certificate
2000-12-08
2004-03-30
Glick, Edward J. (Department: 2882)
Electric lamp and discharge devices
With gas or vapor
Having electrode exterior to envelope
C313S234000, C313S567000, C313S594000
Reexamination Certificate
active
06713961
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a high-intensity discharge lamp, which is provided with a light-transmissive ceramic discharge enclosure, a high-intensity discharge lamp lighting system employing the high-intensity discharge lamp, and a lighting appliance using the lamp.
BACKGROUND OF THE INVENTION
Recently, the inventors of the present invention have devised a compact metal halide lamp whose lamp power is about 10 to 30 W for a light source suited for optical fibers or a substitutive light source for a halogen lamp and a compact high-intensity discharge lamp, i.e., a screw-base-mount type high-intensity discharge lamp in which the metal halide lamp, a compact lighting circuit for lighting the metal halide lamp and a screw base are integrally assembled together. The screw-base-mount type high-intensity discharge lamp has a lamp efficiency which is about three to four times higher than that of the halogen lamp, and which is remarkably smaller in size than that of the screw-base-mount type fluorescent lamp, so as to be treated as a point-source of light.
However, since the lamp belongs to a high-intensity discharge lamp, it requires a stabilizer comprising therein an igniter for generating a relatively high voltage pulse at a starting operation, i.e., a lighting circuit. Alternatively it requires a stand-alone igniter and a lighting circuit not including such an igniter. Accordingly, even if a compact high-intensity discharge lamp would be devised for all troubles, an overall system comprised of a light source, a stabilizer or a lighting circuit and a lighting unit results to have a large size. On the other hand, a compact fluorescent lamp and a screw-base-mount type fluorescent lamp in which such a fluorescent lamp is integrated with its lighting circuit have been used as a light source alternative to an incandescent lamp. Since such a screw-base-mount type fluorescent lamp also belongs to a discharge lamp, it requires a lighting circuit. However the lighting circuit of the screw-base-mount type fluorescent lamp is overwhelmingly small in comparison with that of the high-intensity discharge lamp.
As a result of the studies to solve the above problem, the inventor had achieved success of employing a lighting circuit principally constituted by a compact high-frequency inverter which is used for the screw-base-mount type fluorescent lamp as the lighting circuit of the compact high-intensity discharge lamp. Since the lighting circuit mentioned above is generally simple in its circuit arrangement, and works at a high frequency, it is compact, light in weight and less expensive. Accordingly, it is realize a high-intensity discharge lamp lighting system which is compact, light weight, and less expensive.
However, if it is possible to lower the starting voltage for the high-intensity discharge lamp it will realize a lighting circuit which is much more compact, light weight and less expensive.
Generally, the starting voltage for the discharge lamp follows a function of the distance between electrodes and the pressure of the discharge agent, that is, the Paschen's law in a case that the conditions of the electrode and the discharge agent are fixed.
Accordingly, to lower the starting voltage it is common that the pressure of the discharge agent is lowered down, and the distance between the electrodes is shortened. According to the above measures, the starting voltage is certainly lowered. However, it causes several drawbacks such as increases of spattering or evaporation of tungsten constituting the electrodes which causes a blackening of the light-transmissive ceramic discharge enclosure, and thus results of lowering the luminous flux retention and/or the lighting efficiency.
There is another measure to provide a supplemental conductor nearby the electrodes for lowering the starting voltage. As such a conventional technique, it is known that both ends of a supplemental conductor is wound about two or three turns on each of the small-diameter cylinders at a portion nearby the boundary of the cylinder and the enclosure respectively. And then the mid-portion of the conductor is elongated along the enclosure. Here, the supplemental conductor is isolated from the electrodes and thus electrically disconnected therefrom.
As another conventional technique, it is known that respective one ends of a pair of supplemental conductors are wound about two or three turns on the mid-portions of a pair of elongated sealing portions of a light-transmissive silica discharge enclosure. The mid-portions of the supplemental conductors are elongated along the enclosure in leaving appropriate distance from the enclosure. While respective other ends of the supplemental conductors are coupled to the outer lead wires of the opposite side sealed portions.
However, in the conventional techniques employing such a supplemental conductor it is found that the supplemental conductor does not always work effectively.
SUMMARY OF THE INVENTION
The present invention has an object to provide a high-intensity discharge lamp which operates at a low starting voltage, a high-intensity discharge lamp lighting device employing the high-intensity discharge lamp, and a lighting appliance.
A high-intensity discharge lamp according to the first aspect of the invention comprises a lighting-source bulb provided with a light-transmissive ceramic discharge enclosure containing an enclosure defining a discharge space and a pair of small-diameter cylinders communicating with the enclosure at both ends thereof and having an inside diameter smaller than the enclosure, a pair of slender electrodes extending through the small-diameter cylinders of the light-transmissive ceramic discharge enclosure in leaving narrow gaps between the inside surfaces of the small-diameter cylinders and the electrodes and a discharge agent filled in the light-transmissive ceramic discharge enclosure; a metallic coil which is wound on at least one of the small-diameter cylinders through which one of the electrodes extends, and which is coupled to the other end of the electrode to have the same potential with the electrode, a jacket-bulb which hermetically accommodates therein the lighting-source bulb and the metallic coil and a pair of outer lead terminals which are coupled to the pair of electrodes and hermetically led outside the jacket-bulb.
In the following descriptions, there will be made definitions and their technical meanings for presenting following specific terms, unless otherwise specified.
Herein-below the high-intensity discharge lamp will be described for each of its components.
Lighting-Source Bulb
The lighting-source bulb is provided with at least a light-transmissive ceramic discharge enclosure, a pair of electrodes and discharge agent.
Discharge Lamp Light-Transmissive Ceramic Enclosure
The term “light-transmissive” means a transmissivity allowing light generated by a discharge to be led outside. Accordingly the term may include not only a transparency but also a light-diffusiveness. When the light-transmissive ceramic discharge enclosure is provided with a small-diameter cylinder, it is essential only that the enclosure has a transmissivity to radiation to be utilized. While the small-diameter cylinder or the portion that may not utilize the radiation by the discharge can be light-tight.
Accordingly, the term “light-transmissive ceramic discharge enclosure” means a discharge enclosure comprised of at least an enclosure which is made of monocrystalline metal oxide, e.g., sapphire, polycrystalline metal oxide, e.g., semi-transparent hermetic aluminum oxide (alumina-ceramics), yttrium-aluminum garnet (YAG), yttrium oxide (YOX) and polycrystalline nonoxidic material, e.g., material having a light-transmissivity and a heat-resistancy like aluminum mitride (AIN).
Further, in making the light-transmissive ceramic discharge enclosure, one or a pair of small-diameter cylinders may be integrated with the enclosure by coupling the cylinder(s) to opposite two ends of the enclosure at the first step. However, for instance, it is als
Ashida Seiji
Honda Hisashi
Kawatburu Shigehisa
Miyagawa Kazuhiro
Sakaguchi Sadao
Glick Edward J.
Pillsbury & Winthrop LLP
Toshiba Lighting & Technology Corporation
Yun Jurie
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