Sealing a fiber drawing furnace

Abstract

A drawing furnace or the like for manufacturing optical fiber preferably of a vertical fiber preform, which drawing furnace includes at least a preferably tubular heating element surrounding the fiber preform for heating the fiber preform, an outside insulating layer of the heating element, a frame part of the drawing furnace in order to place the heating element and insulating layer in the drawing furnace, and a cover part in order to close the area between the heating element and the frame part to insulate the insulating layer from the gas flow surrounding the fiber preform. A gas tube is fitted between the cover part of the drawing furnace and the heating element in order to feed gas to the gas space surrounding the fiber preform, and the cover part is still fitted mobile in relation to the frame when the length of the heating element changes in such a manner, that a force, which is substantially constant and seals the gas tube to the end of the heating element, is directed at the gas tube in all modes of operation of the drawing furnace.

Dependencies are inferred from the claim text.