FURNACE FOR DRAWING OPTICAL FIBER

摘要

PURPOSE: To obtain an optical fiber hardly causing the fluctuation in fiber diameter by providing a constitution for installing a shutter ring at the top of a furnace for drawing the optical fiber, providing an elastically deformable sealing ring thereon and holding the sealing ring with a sealing ring holder. CONSTITUTION: This furnace for drawing an optical fiber is constituted by placing a shutter ring 20 of a heat insulating structure for passing a supporting rod 15 therethrough in a noncontact state at the top of the furnace for drawing the optical fiber, arranging an elastically deformable sealing ring 27 so as to bring the inner peripheral surface thereof into sliding contact with the outer peripheral surface of the supporting rod 15 above the shutter ring 20, placing a sealing ring holder 30 on the shutter ring 20 so as to hold the outer peripheral side of the sealing ring 27 and pressing the sealing ring holder 30 together with the shutter ring 20 to the top side of the furnace for drawing by a ring fixing means. Thereby, an atmospheric gas in the furnace core tube is prevented from leaking out and the temperature decrease at the top of the furnace can be reduced to suppress the convection of the gas in the furnace.