| 摘要 |
PURPOSE:To obtain the title material whose core portion diameter of an available length is uniform in the longitudinal direction by forming a glass tube so that the diameter of one end portion is made smaller and that of the other end portion larger and by feeding feed gas into the tube to deposit a glass component on the tube inside. CONSTITUTION:The portion of glass tube 1 except one end portion 1a and other end portion 1b is considered as available length L, and the inside and outside diameters of the portion of length L are made uniform. Both end portions 1a, 1b of tube 1 are supported with bearings 2a, 2b of a glass lathe, and a clogging stopper is attached to portion 1b. Inert gas is blown from portion 1a to hold the internal press. of tube 1 at a predetermined value, and the portion of l2 is uniformly heat- softened with heater 3 and inflated to form tube 1 so that l1<l2 is attained within the range of length L and the boundary between l1 and l2 is tapered. Feed gas is then fed into tube 1 from portion 1a to portion 1b, and heater 3 is reciprocated over length L to deposit glass component 4 on the tube 1 inside. |
