| 摘要 |
PURPOSE:To stabilize the control of exhaust pressure and to carry out stably the manufacture of a base material for an optical fibre for a long time by providing branches to an exhaust pipe of a VAD reaction vessel for manufacturing said material, introducing open air from the branch, and adjusting the quantity of the air to be introduced. CONSTITUTION:A base material 4 for an optical fibre is lowered in a VAD reaction vessel 1 and raised gradually under revolution. On the other hand, a gaseous starting material for soot, oxygen and hydrogen are supplied from a multiple pipe burner 2, and the soot made by hydrolysis in a oxygen-hydrogen flame 3 is deposited on said material 4. In this case, the gaseous starting material, the soot and water vapor which are not used for the formation of said material 4 are evacuated from an exhaust pipe 6, however, the pressure in said pipe 6 is measured by a pressure gauge 10 provided at a branch 9 out of the two branches 8, 9 provided at said pipe 6. In case of negative pressure, the flow rate of the air in a mass-flow controller 12 at the branch 8 is controlled by a control apparatus 13, and the exhaust pressure in the reaction vessel 1 is controlled always to be constant by adjustment of introduced quantity of the air in the exhaust pipe 6 to carry out stably the manufacture of said material 4 without any trouble in the reaction vessel 1. |
