| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a fluorescent lamp including three or more conventional annular luminous tubes having different annular diameters and arranged substantially conically in a substantially same plane, in which the total luminous flux and luminous efficiency of the lamp are improved when the lamp is attached to a hermetically sealed fixture, by lowering the coldest point without changing the maximum outer diameter. <P>SOLUTION: In the cross-sectional shape of a tube at a part of the bridge joint of an annular luminous tube on the side opposite from a discharge path, the length (a) perpendicular to the concentric surface of a ring is made longer than a length b parallel with the surface of the concentric circle of the ring. Since the coldest point can be located at the lowermost part of the tube end near the bridge joint, the temperature can be lowered below that at the outermost part of the tube end near the bridge joint. In such an atmosphere that the ambient temperature increases when the lamp is attached to a hermetically sealed fixture, the lamp can be brought close to a temperature where the total luminous flux is maximized, and can be lighted in such a state that the luminous efficiency is high in the fixture. <P>COPYRIGHT: (C)2013,JPO&INPIT |
