Preform entry device for an optical fibre draw furnace and draw furnace comprising said entry device

摘要

Furnace (1') includes an enclosure (4') having a preform insertion opening, and a device (3') for inserting the preform into furnace. Preform insertion device (3') comprises injector (6') for injecting gas around the preform and filling the enclosure, and a sealed coupling (17B) fixed above the injector and allowing passage of preform body (9'). Sealing lock (13) closes the top of the furnace. The sealing lock (13) is located above the injector (6') and provides sealing both in the presence and in the absence of the preform and maintains an overpressure of inert gas at the entry of furnace to avoid air inlet.