| 摘要 |
PROBLEM TO BE SOLVED: To provide an method and apparatus for producing a drawn preform, wherein deterioration of the interface between a glass preform and a glass jacket tube can be prevented by inhibiting the evaporation of volatile constituents from the surface of the glass preform and from the inner wall of the glass jacket tube. SOLUTION: The producing method for the drawn preform, wherein a glass preform 1 is inserted into a hollow part 21 of the glass jacket tube 2 and a glass preform is drawn, includes a process wherein an internal pressure of the glass jacket tube is decreased to a specific one and integration is partially performed, a process wherein the pressure in the glass jacket tube is increased to more than the above specific one after the integration, and a process wherein a glass preform is drawn from an integrated part. Accordingly the deterioration of the interface between the glass preform and the glass jacket tube can be prevented because, in the process wherein glass is softened and in the process for drawing, the internal pressure of the glass jacket tube is controlled to inhibit the volatile constituent's evaporation from the surface of the glass preform and from the inner wall of the glass jacket tube. |
