| 摘要 |
1,003,461. Sight holes for furnaces. M. FOGUEL. Feb. 27, 1964 [Feb. 27, 1963], No. 8215/64. Heading F4B. A sight hole for a muffle furnace 11 is formed by a conical recess 12 in the furnace wall, the apex of the recess forming a pinhole 18 in the outer surface of the wall. A crystal 13 formed by fusion in the furnace 11 produces an inverted image on a screen 17 spaced from the pinhole. In another embodiment, Fig. 2, a crystal 26 is observed through a pinhole 25 at the apex of a conical recess 24 in a cylindrical plug 23 fitted in a hole in the furnace wall. A lens 28 throws an upright image on the screen 30. |
