Abstract: A sealing arrangement for a drawing furnace including a vertical center hole with surrounding heating elements for receiving a glass preform including a tapered portion connected to an extension rod. A sealing with an opening is arranged on top of the furnace. The arrangement includes an outer annular bushing arranged on top of the furnace and an inner annular bushing with a first and an opposing second vertical end. The inner bushing is positionable to surround at least part of the tapered portion with the first end positioned to the region of the beginning of the tapered portion and the second end includes protrusions on the outer surface. As the inner bushing is inserted in the outer bushing it is arranged to be movable within the outer bushing and the protrusions form supports for holding the second end of the inner bushing above the center hole.

Abstract: A sealing arrangement for a drawing furnace including a vertical center hole with surrounding heating elements for receiving a glass preform including a tapered portion connected to an extension rod. A sealing with an opening is arranged on top of the furnace. The arrangement includes an outer annular bushing arranged on top of the furnace and an inner annular bushing with a first and an opposing second vertical end. The inner bushing is positionable to surround at least part of the tapered portion with the first end positioned to the region of the beginning of the tapered portion and the second end includes protrusions on the outer surface. As the inner bushing is inserted in the outer bushing it is arranged to be movable within the outer bushing and the protrusions form supports for holding the second end of the inner bushing above the center hole.

Abstract: The invention relates to an apparatus. In order to achieve efficient sealing, the apparatus includes a sealing with a plurality of sealing elements arranged generally in a ring configuration around a center opening. Each sealing element includes a sealing surface facing the center opening. At least one chamber is included for receiving sections of the sealing elements. An inlet to a fluid source provides the at least one chamber with fluid in order to generate an overpressure acting on the sections of the sealing elements received in the at least one chamber, and for pressing and moving the sealing surfaces of the sealing elements towards the center opening.

Abstract: The invention relates to an apparatus. In order to achieve efficient sealing, the apparatus includes a sealing with a plurality of sealing elements arranged generally in a ring configuration around a center opening. Each sealing element includes a sealing surface facing the center opening. At least one chamber is included for receiving sections of the sealing elements. An inlet to a fluid source provides the at least one chamber with fluid in order to generate an overpressure acting on the sections of the sealing elements received in the at least one chamber, and for pressing and moving the sealing surfaces of the sealing elements towards the center opening.

Abstract: The present invention relates to a system for manufacturing fibres comprising a melting furnace, a crucible within said furnace comprising at least one orifice (6) and at least one induction coil (4) for heating the melting furnace and the crucible. In a typical system according to the invention, the crucible comprises at least a first part (1) made of graphite and comprising said at least one orifice (6). The invention also relates to the use of the system as well as to a method for manufacturing fibres and to said fibres.

Abstract: The present invention relates to a system for manufacturing fibres comprising a melting furnace, a crucible within said furnace comprising at least one orifice (6) and at least one induction coil (4) for heating the melting furnace and the crucible. In a typical system according to the invention, the crucible comprises at least a first part (1) made of graphite and comprising said at least one orifice (6). The invention also relates to the use of the system as well as to a method for manufacturing fibres and to said fibres.

Abstract: A heating apparatus for preparing an optical fiber from a preferably vertical fiber preform in a draw furnace, in which draw furnace the fiber preform is heated with the heating apparatus in the heating zone of the draw furnace in such a way that a molten, downwards tapering zone is formed in the preform, from which a thin fiber is produced by means of gravity and/or drawing the fiber downwards, which heating apparatus comprises at least a preferably tubular heating element, placed around the fiber preform in the draw furnace, for heating the fiber preform, and a heating means placed around the heating element in the draw furnace, for heating the heating element, as well as an insulator element around the heating element. The heating element and the insulator element are surrounded at least partly by a radiation shielding to reflect thermal radiation from the heating element to the insulator element back to the heating element.