| 摘要 |
PURPOSE:To excellently close the opening of a crucible and to surely prevent the flowing down of molten glass by combining a plug for closing the nozzle opening and a cooler to cool the periphery of the plug, and allowing the plug and cooler to play specified roles. CONSTITUTION:The molten core glass 6 and clad glass 7 placed in the crucible 1 are agitated, and clarified. Before this case, the plug 12 to close the openings 4 and 5 is previously inserted, supported, and fixed by a fixer, etc. A cooling gas is injected from a cooling gas injection port 16. The glass in the crucible 1 is heated and melted, or the clad glass 7 is poured from the upper part. Consequently, the clad glass 7 tends to flow out to the outside from the gap between the nozzle 4 of the outer crucible 3 and the plug 12. At this time, the glass is immediately cooled and solidified by the cooling gas, and the outflow is prevented. As a result, the nozzle opening can be completely closed, even it the plug 12 is not closely attached to the nozzle 4. |
