| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a light source unit realizing extension of its service life by simply and surely preventing a reflector of a light-transmitting plate from cracking and enabling the light-transmitting plate to be surely positioned relative to a luminous tube fixed to the reflector. SOLUTION: In this light source unit U, a light-transmitting plate 20 is fixed to a reflector R being fitted into a groove part 22, thereby covering an opening part of the reflector R, and thus a structure suitable for explosion-proof is obtained. At the time of fixing, a side wall surface 22b of the groove part 22 is spaced apart from the side surface 20c of the light-transmitting plate 20. Even in the cases where the reflector R differs from the light-transmitting plate 20 in the amount of thermal expansion, the space can provide an appropriate escape for stresses. When the light-transmitting plate 20 is fitted into the groove part 22, a bottom wall surface 22a of the groove part 22 is brought into direct contact with a back surface 20d of the light-transmitting plate 20, thereby surely defining positional relation between a luminous tube and the light-transmitting plate 20 in the tube axis direction of the luminous tube. This is effective especially in the cases where the light-transmitting plate 20 is a lens.</p> |
