Patent ID: 6993937
Filing Date: 2006-02-07
Classification: C03B

Abstract:
1. An inlet arrangement for inserting a preform into a furnace for drawing a fiber, which furnace is of the type including an enclosure at the top of which there is an opening to allow insertion of the preform which moves vertically downwards in translation during fiber drawing; said inlet arrangement composing both an injector situated at the level of the preform inlet opening to inject inert gas onto the perimeter of the preform to fill the enclosure of the furnace, and an airlock comprising at least one seal fixed by means of a seal support above the injector and designed to allow the preform to pass therethrough with the cylindrical main body of the preform being surrounded to prevent gas circulating between the surrounding environment and the inside of the furnace at the level where the at least one seal is situated; said airlock further comprising a closure member that is selectively operated between a closed position and an open position for closing and sealing the top of the furnace above the injector, and for maintaining a positive internal gas pressure at the furnace inlet to prevent the surrounding entering at that level, and wherein said airlock is disposed above said injector so as to be located upstream of said injector.