| 摘要 |
PURPOSE:To provide high-quality, optical-transmitting glass member having little light-transmission loss by a method wherein glass composition is clarified by melting and bubbling it in inert gas atmosphere and drawing it from small hole at the bottom of crucible while keeping a specified temperature. CONSTITUTION:Atmosphere 54 within furnace enclosed by furnace body 40, 42 and lid 48 is filled with inert gas admitted from 55 and is maintained positive pressure against outside atmosphere. Glass composition is contained in multiple-layer crucible and heated by oxygen gas which is heated in process of melting and clarification and by furnace temperature at the bottom of the furnace. The oxygen gas is jetted into internal and external crucible through many holes 58 installed to nozzle 57 so as to effect bubbling of glass material. Heater 60 for nozzle area is heated to raise temperature in the areas of nozzles 26 and 38 so that molten glass is decreased in viscosity in these areas. Then, oxygen inlet pipe 56 and oxygen jet nozzle 57 are removed downwardly so that optical transmitting member is drawn downward. |
