PURPOSE: To keep the inner pressure as well as to carry out cooling with only a protection gas by supplying the protection gas into a hermetic outer lamp body and disposing the opening part of inner lamp body close to the glass surface of irradiation window of inner lamp body opening part so that the protection gas is allowed to flow in through the thin clearance between the glass surface and the opening part.
CONSTITUTION: The hermetic outer lamp body 1 is provided with an irradiation window 2 with glass 3 fitted in its lower surface, and the protection gas supplied from an inlet 4 through a passage 5 by a blower 6 set in the outside of explosive atmosphere keeps the pressure of inside higher than that of the surrounding explosive atmosphere. A lamp 8 and a reflection body 9 are housed in the inner lamp body 7 which is disposed in the outer lamp body 1, and the opening part 11 of lower surface is disposed close to the inner surface of the glass 3 of the irradiation window of the outer lamp body 1 so that the protection gas in the outer lamp body 1 entered from the opening 11 while cooling the surface of glass, cools the lamp 8 and the reflection body 9, and then is directly discharged from an outlet 13 through a passage 14 into the outside of explosive atmosphere. As a result, keeping inner pressure and cooling are carried out only by the protection gas.
YUGE YOSHIHIRO
MURAKAMI KAZUHIRO
