Optical fiber drawing apparatus and sealing mechanism for the same

An inner seal ring is composed by connecting a plurality of inner seal ring pieces A, an outer seal ring is composed by connecting a plurality of outer seal ring pieces A provided at an outer periphery of the inner seal ring , and a coil spring is arranged at an outer periphery of the outer seal ring . The inner seal ring and the outer seal ring are piled for two or more stages, respectively. A connecting part of the inner seal ring pieces A and a connecting part of the outer seal ring pieces are arranged not to overlap each other. An inner diameter of the inner seal ring is variable in accordance with an outer diameter in vertical direction of a drawing-preform by using a coil spring