| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a glass preform where a high temperature exhaust gas can be exhausted without damaging an exhausting line. SOLUTION: The exhausting amount of the high temperature gas is suppressed by initial exhausting from a small-diameter tube 20a (for example, inside diameter of about 10-20 mm) which is one of the two lines when the high temperature exhaust gas is exhausted. After the temperature of the exhaust gas is lowered to some degree, exhausting from a large-diameter tube 20b (for example, inside diameter of about 100-150 mm) starts and then the high temperature exhaust gas can be exhausted without damaging exhausting pipes 28a and 28b, valves 24 and 27, a packing at a connection part and the like. COPYRIGHT: (C)2007,JPO&INPIT
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