Apparatus for fabricating a glass rod and method of same

摘要

The present invention provides an apparatus and a method for fabricating a glass rod from a glass preform capable of suppressing a diameter fluctuation of the drawn glass rod even when there is a relatively large diameter reduction ratio between the glass preform and the glass rod, such as 60 to 95%. The feed speed V1 of the glass preform is set to a constant value, the diameter D of the glass preform is acquired for determining the drawing speed V2 from diameter data of the glass preform measured before being drawn at a diameter acquisition position defined with respect to a reference position of the furnace. The distance from the reference position to the diameter acquisition position is defined so as to vary depending on a diameter fluctuation of the glass preform before being drawn in a longitudinal direction thereof.

主权项

1. A method of fabricating a glass rod from an elongated glass preform using a furnace, the furnace extending between an input end and an opposing output end, the glass rod being fabricated so as to have a target diameter, the glass preform having a region thereof extending in a longitudinal direction between a drawing start position and a drawing end position, the distance between the drawing start position and the drawing end position defining a length of the region, the glass preform having a pre-drawn diameter that varies over the length of the region from a first initial diameter value at the drawing start position to a second initial diameter value at the drawing end position, the method comprising:
determining first and second drawing reference distance values respectively corresponding to the drawing start and drawing end positions, the first and second drawing reference distance values being dependent on the first and second initial diameter values, a predetermined feed speed value, and the target diameter, the first and second drawing reference distance values each being defined by the following equation:L=VMπ×(ND2)2, where:
L is the first or second drawing reference distance value,VM is the volume of the glass preform between a reference position of the furnace and a position PM of the furnace where a deformation rate of the glass preform is the greatest, andND is the first or second initial diameter value of the glass preform; feeding the glass preform longitudinally into the input end of the furnace at a feed speed such that a plurality of points longitudinally spaced along the region pass the reference position of the furnace as the glass preform is fed into the furnace, the feed speed being maintained at the predetermined feed speed value; drawing the glass preform from the output end of the furnace at a variable drawing speed as the glass preform is fed into the furnace, the variable drawing speed being controlled so that as each point of the region passes the reference position of the furnace, the following equation is satisfied:V⁢⁢2V⁢⁢1=(Dd)2, where:
V2 is the variable drawing speed at the particular point of the region,V1 is the feed speed,D is the pre-drawn diameter of the glass preform at a diameter acquisition position corresponding to the particular point of the region, the diameter acquisition position being longitudinally separated from the particular point of the region by a drawing reference distance, andd is the target diameter of the glass rod, wherein the drawing reference distance varies between the first and second drawing reference distance values over the length of the region, the variance of the drawing reference distance at each point of the region with respect to the first drawing reference distance value being based on the longitudinal location of the corresponding point within the region, wherein the drawing reference distance transitions linearly from the first drawing reference distance value at the drawing start position to the second drawing reference distance value at the drawing end position, and wherein the drawing reference distance at each point of the region is determined by interpolating between the first and second drawing reference distance values.