| 摘要 |
PROBLEM TO BE SOLVED: To provide a double-tube incandescent bulb that can make base diameter small, that has a small top opening of a concave reflection mirror to expand the effective area of the reflecting face, and that does not reduce illumination on the illuminated surface. SOLUTION: This double-tube incandescent bulb is attached with insulating base 20 at a seal 12 of the incandescent bulb 10, which is covered with an outer tube 30 fixed to the base 20 at the end. Outer face of fixed portion of the outer tube 30 and base 20 is covered with a ring metal frame 40 in the fastened state. A recess 23 is formed at the outer face of the base 20, and inner projection 41 formed on the frame member 40 is fit at this recess 23.
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