| 摘要 |
PROBLEM TO BE SOLVED: To provide a thermal shielding cylinder suitable for obtaining a glass preform which can control temperature rising at a connection of a shaft having a porous glass preform and a quartz rod on the upper part of the porous glass preform, can shorten the distance between the connection and an effective part of the porous glass preform, and to provide a manufacturing device and a manufacturing method of a glass preform provided with it. SOLUTION: The thermal insulating cylinder is so constructed that in a device of heat treating the porous glass preform 1 hung in a reacting container and vitrifying transparently, the thermal shielding cylinder is provided near the connection so that quantity of radiation heat to be received by the connection part 3 of the shaft 2 fixed at the device with free revolution and the quartz rod 9 on the upper part of the porous glass preform is reduced. |
