Matsushita Electric Industrial Co., Ltd.

Kozo Shirai

Toshiyoshi Oga

Masaru Saitoh

A method for manufacturing a glass tube used for a fluorescent lamp having an arc tube constructed by joining a plurality of glass tubes is provided. According to this method, a straight glass tube held at both ends is rotated, and a predetermined cutting portion of the glass tube is softened by heating, and then the glass tube is moved in the heated state in the direction toward the predetermined cutting portion to form a glass accumulated portion at the area of the predetermined cutting portion. Next, the glass tube is drawn away in the direction receding from the predetermined cutting portion, and the predetermined cutting portion of the glass tube is cut into two glass tubes having self-closing end walls. In this way, the end walls of the self-closed glass tubes can be formed thicker and more uniform compared to those obtained by the conventional techniques, and the mechanical strength of the end walls also can be improved. As a result, the defective percentage of the lamps during the manufacturing process and on the market due to cracks, leakage, or damages in the end walls of the glass tubes can be reduced.

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Kyoto, Japan

Kozo Shirai