| 摘要 |
PURPOSE:To obtain a drawn rod having uniform outer diameter along the longitudinal direction, by controlling the take-up speed and delivery speed of a glass rod according to the measured value of outer diameter at the front end of a neck-down part of a drawn glass rod. CONSTITUTION:A supporting rod 21 and a drawing rod 22 welded to both ends of a glass rod 20 are fixed to an upper chuck 9 and a lower chuck 10, respectively. An inert gas is supplied to a furnace core tube 2 and a chamber 16 through inlet ports 17, 18 and, at the same time, heaters 3, 4 are electrified to heat an aeration port 6 or thereabout at about 1,800 deg.C. The chuck 9 is transferred downward at a specific speed with an upper driving part 11 under rotation, the rod 20 is heated and softened at the aeration port 6 and the chuck 10 is rotated and transferred downward at a speed higher than that of the chuck 9 with a lower driving part 12. At the same time, laser beam emitted from a laser beam generator 7 is applied via a lens 24 to the neck-down part 25 of the rod 20, passed through a lens 26 and introduced into a detector 8 to measure the outer diameter. The driving parts 11, 12 are controlled with a speed controlling device 13 according to the data of the measured diameter. |
