Patent ID: 8881552
Filing Date: 2014-11-11
Classification: C03B

Abstract:
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, the value of which varies over the length of the region, the method comprising: determining values of the pre-drawn diameter of the glass preform over the length of the region; feeding the glass preform longitudinally into the input end of the furnace at a variable feed speed such that a plurality of points longitudinally spaced along the region pass a reference position of the furnace as the glass preform is fed into the furnace, the feed speed being controlled so as to vary over the length of the region, the variance of the feed speed at each point of the region being based on the value of the pre-drawn diameter of the glass preform at a diameter acquisition position corresponding to the particular point, the diameter acquisition position being longitudinally separated from the particular point of the region by a predetermined drawing reference distance that remains fixed over the length of the region, wherein feeding the glass preform into the furnace causes a diameter decreasing region to be formed in the glass preform, the diameter decreasing region having a position PM at which a deformation rate of the glass preform is at a maximum value, the position PM being dependent on the feed speed, and the feed speed being varied to maintain the predetermined drawing reference distance at a constant value as the glass preform is fed into the furnace, the predetermined drawing reference distance L being defined by the following equation: where: drawing the glass preform from the output end of the furnace at a variable drawing speed V2 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: where: