Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
1999-07-16
2002-03-12
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C445S043000, C445S066000
Reexamination Certificate
active
06354901
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a discharge lamp, where luminescent substances are sealed in an arc tube that is mainly made of, for example, a translucent ceramic, as well as to a method of sealing such a discharge lamp and an apparatus for sealing such a discharge lamp.
BACKGROUND ART
In these discharge lamps, an electrode member having a pair of electrodes is fixed in an air-tight manner to an opening of an arc tube, which is mainly made of a translucent ceramic, and luminescent substances, such as mercury, inert gases, and metal halides, are sealed in the air-tight manner in the arc tube. In such discharge lamps, a known method applied to seal the opening of the arc tube in the air-tight manner fuses a sealing glass like a glass frit and seals a gap between the electrode member and the opening of the arc tube with the fused sealing glass.
One known technique uses infrared radiation as a heat source for fusing the sealing glass. When a residual part of the arc tube other than the sealing glass is irradiated with infrared emission, the luminescent substances fly out of the arc tube. The technique can not accordingly attain the desired properties of the discharge lamp.
The object of the present invention is thus to provide a discharge lamp that reduces a fly loss of luminescent substances in an arc tube in the process of sealing an opening of the arc tube by using infrared radiation, as well as a method of sealing such a discharge lamp, and an apparatus for sealing such a discharge lamp.
DISCLOSURE OF THE INVENTION
A first application of the present invention is directed to an apparatus for sealing a discharge lamp, which fuses a sealing glass to seal an opening of an arc tube, through which a luminescent substance has been charged into the arc tube. The apparatus includes: a support jig that supports the arc tube, which is provided with the sealing glass placed around a circumference of the opening; and an infrared irradiation unit that emits infrared radiation to fuse the sealing glass, wherein the support jig is mainly made of a material that has a greater thermal conductivity than that of the arc tube.
The apparatus for sealing a discharge lamp in accordance with the first application of the present invention seals the opening of the arc tube, through which the luminescent substances are charged into the arc tube, by fusing the sealing glass with heat of infrared radiation emitted from the infrared irradiation unit. One end of the arc tube is supported by the support jig. The support jig is mainly made of a material having a greater thermal conductivity than that of the material of the arc tube, for example, a metal material like Al or Cu. This enables heat to be readily conducted from the arc tube to the support jig and thereby prevents a temperature rise in the arc tube. This arrangement effectively prevents the luminescent substances from being vaporized and released from the arc tube.
A cooling unit that lowers the temperature of the support jig is favorably provided to enhance the heat conduction from the arc tube to the support jig.
In accordance with one preferable embodiment of the first application, the apparatus for sealing a discharge lamp further includes an infrared shield that restricts the infrared radiation emitted from the infrared irradiation unit to a periphery of the sealing glass. This structure enables only the sealing glass to be fused for sealing the opening, while shielding the other part of the arc tube from the infrared radiation. This accordingly prevents a temperature rise in the arc tube.
In accordance with one preferable arrangement, the support jig is attached to the infrared shield via a heat-insulator. This arrangement simplifies the attachment structure of the infrared shield. The heat-insulator reduces the quantity of heat conducted from the infrared shield to the support jig. This arrangement accordingly decreases the quantity of heat conducted from the support jig to the arc tube and prevents a temperature rise in the arc tube.
A second application of the present invention is directed to a method of sealing a discharge lamp. The method fuses a sealing glass to seal an opening of an arc tube, through which a luminescent substance has been charged into the arc tube. The method includes the steps of: supporting one end of the arc tube with a support jig; placing the sealing glass around a circumference of the opening; and irradiating the sealing glass with infrared emission to fuse the sealing glass and thereby seal the opening, and cooling the support jig.
The method of sealing a discharge lamp given as the second application cools the support jig down in the course of fusing the sealing glass placed on the arc tube, while the arc tube is supported by the support jig. This arrangement enhances the heat conduction from the arc tube to the support jig and thereby prevents a temperature rise in the arc tube.
A third application of the present invention is directed to an apparatus for sealing a discharge lamp, which fuses a sealing glass to seal an opening of an arc tube, through which a luminescent substance has been charged into the arc tube. The apparatus includes: a support jig that supports one end of the arc tube; a feeding conduit that is arranged to cover the arc tube in an air-tight condition; an infrared irradiation unit; and a heating unit that condenses infrared radiation emitted from the infrared irradiation unit on a predetermined light condensing area, in order to fuse the sealing glass placed around a circumference of the opening of the arc tube. The heating unit has an opening, through which one end of the feeding conduit is protruded outward.
In the third application of the present invention, the opening of the heating unit enables the user to monitor the state in the heating unit. When a part of the feeding conduit is stained, the other end of the feeding conduit that is not projected from the opening is cut off. This shifts the position of the stained part of the feeding conduit relative to the light condensing area of the infrared radiation and thereby favorably avoids frequent replacement with a new feeding conduit.
It is preferable that the heating unit has a transparent window, through which the user can observe the state of fusing the sealing glass and sealing the opening of the arc tube. This arrangement enables the user to securely check the state of sealing the opening with the fused sealing glass.
In accordance with one preferable embodiment of the third application, the heating unit has: a flow length detection unit that measures a flow length of the fused sealing glass flown into the arc tube; and a heating control unit that stops the emission of the infrared irradiation unit when the flow length of the fused sealing glass measured by the flow length detection unit becomes not less than a predetermined value. This arrangement ensures the accurate detection of the flow length of the sealing glass and attains automation without requiring the process of monitoring the sealing state.
A fourth application of the present invention is directed to a discharge lamp, which includes: an arc tube with an opening; an electrode member that is inserted into the arc tube through the opening and has an electrode element; and a halide sealed in the arc tube, wherein electricity is suppled to the electrode member to make the halide radiate. The electrode member has a film layer on a circumference thereof. The film layer includes: a thin film layer that is formed on a specific part, which is in contact with the halide in the arc tube, and includes a halide-resistant material having high corrosion resistance to the halide; and a buffer layer that is interposed between the thin film layer and the circumference of the electrode member and formed to have a medium thermal expansion coefficient, which is between a thermal expansion coefficient of the thin film layer and a thermal expansion coefficient of the electrode member.
In the discharge lamp given as the fourth application, the film layer including the thin film
Bundo Tetsuaki
Hayashi Koichi
Ishibashi Hirotaka
Kita Koji
Nagai Hiroaki
Beyer Weaver & Thomas LLP
Ramsey Kenneth J.
Toto Ltd.
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