PURPOSE: To obtain an observing device for the inside of a furnace, which is inexpensive and highly reliable without necessitating any special facility, by a method wherein problems of enlarging and complicating of the whole of the device are eliminated. ;CONSTITUTION: The substatially sealed type main body 1 of the title device is provided with a mirror 4, inclinably supported through a gas spring 6 contractable by the pressure difference between the outside and inside of the furnace, as well as an observing means 7, picking up an image in the furnace which is reflected by the mirror 4, which are accommodated in the main body, and an obsreving window 10, directed to the mirror 4. Further, the title device is provided with a gas supplying means 8, supplying pressure gas to the main body 1 of the device.;COPYRIGHT: (C)1993,JPO&Japio
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