| 摘要 |
PURPOSE:To prevent the intrusion of the atmosphere into a heating atmosphere with a short device and simple structure by providing a means for vertically separating a furnace core tube in a heating furnace for passing a glass body vertically through the inside of the furnace core tube piercing the furnace body having a hollow zone heater. CONSTITUTION:A carbon heater 4 and the furnace core tube 3 are provided inside the furnace body 5 in the heating furnace. A quartz partition 23 pierced with a gas passage hole 24 is provided at the protruding part of the tube 3 above the furnace body 5. A high-purity quartz porous glass preform 1 is firstly fixed through a support 2 to a rotatable and liftable chuck, the upper lid 37 of the tube 3 is opened, and the preform 1 is lowered into the upper part 34 of the tube 3. In this case, the partition 23 is closed, and a purging gaseous N2 is introduced into the tube 3 from an inlet 7 for the atmospheric gas in the furnace core tube. Accordingly, the atmosphere is not introduced even when the upper lid 37 is opened. When the treated preform is discharged from the furnace, the preform is raised above the partition 23, the atmospheric gas is exhausted from an exhaust port 21 while introducing gaseous N2 from the inlet 7, the inside of the tube 3 is filled completely with the N2 atmosphere, the partition 23 is closed, and the upper lid 37 is opened. |
