Ushio Denki Kabushiki Kaisha

Takuya Tukamoto

Yoshikazu Suzuki

Yoshihiro Horikawa

Tomoyoshi Arimoto

A short-arc ultra-high pressure mercury lamp in which the change in the shape of the electrodes can be suppressed and a stable arc discharge can always be produced is achieved in an arrangement in which, in the silica glass arc tube, there is a pair of opposed electrodes with a distance between them of at most 2 mm and the tube is filled with at least 0.15 mg/mmof mercury, a rare gas, and a halogen in the range from 1&#xd7;10&#x3bc;mole/mmto 1&#xd7;10&#x3bc;mole/mm, by at least one of the electrodes having a melt part formed toward the electrode tip by winding the electrode rod with a coil and by melting the part of the coil oriented towards the electrode tip at least in the area of its surface. A part of the coil located away from the electrode tip is unmelted and the base point side area of the coil facing away from the electrode tip is rounded and does not have sharp edges.

Short arc ultra-high pressure mercury lamp with rounded end faces of coil tips and process of producing such a lamp

An emission device for an ultra-high pressure mercury lamp which maintains an electrode tip shape by which a stable discharge can always be carried out is achieved for a short arc ultra-high pressure mercury lamp with silica glass arc tube containing a pair of opposed electrodes spaced apart a distance of at most 2 mm and in which the arc tube is filled with at least 0.15 mg/mmof mercury, a rare gas and a halogen in the range from 1&#xd7;10&#x3bc;mole/mmto 1&#xd7;10&#x3bc;mole/mm; by providing an operating device which produces a current feed by which the surface of the tip of at least one of the electrodes is shifted into a molten state during lamp operation.

Emission device for an ultra-high pressure mercury lamp

An ultra-high pressure mercury lamp is provided in which the disadvantage caused by projections formed on the electrode tips during operation can be eliminated. This is achieved by an arrangement in which a silica glass arc tube, filled with at least 0.15 mg/mmof mercury, rare gas and halogen in the range from 10&#x3bc;mole/mmto 10&#x3bc;mole/mm, includes a pair of opposed electrodes spaced a distance of at most 2 mm. Additionally, at least one of the electrodes includes a part with a greater diameter which is formed on the electrode shaft using a melting process, a projection which is formed by the tip of the electrode shaft, and a part with a decreasing diameter which extends from the part with the greater diameter in the direction toward the projection.

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Himeji, Japan

Takuya Tukamoto