Patent ID: 6438997
Filing Date: 2002-08-27
Classification: C03B

Abstract:
A method of elongating a glass preform comprising the steps of holding both ends of the glass preform with first and second holding sections, respectively; moving the first and second holding sections in a longitudinal direction of the glass preform with the moving speed of the first holding section faster than that of the second holding section; heating and softening the glass preform by a heating section successively from the end portion on the first holding section side as the first and second holding sections move in the longitudinal direction of the glass preform; and elongating the glass preform by a tensile force applied to the glass preform;wherein an electric furnace is employed in said heating section, and said method further comprising the steps of: setting a reference value R1 with respect to an outside diameter at a specific position in a tapered region of the glass preform in the process of elongating; acquiring an actually measured value R2 which is an outside diameter at said specific position; and controlling the moving speeds of said first holding section and/or second holding section according to a value (R2/R1) obtained from said reference value R1 and actually measured value R2.