JPS5587918A - Fused glass liquid level detecting method - Google Patents

Abstract

PURPOSE:To enable to detect the liquid level of fused glass and to continuously spin the optical fiber wherein the outer diameter ratio of the core glass to the coating glass is constant by measuring a change of the liquid level in the U-shaped pipe mounted on the outside of the heating furnace. CONSTITUTION:Fixed quantities of the glass materials 9, 10 are fused in the core and coating glass crucibles 2, 3 of the spinning crucible 1. Also the fused glass 11, 12 is communicated to the U-shaped pipe 5 with the communicating vessel 6, the liquid level in the U-shaped pipe is set to the same level as that of the fused glass in the crucible by the leak valve 7. When the spinning rate of the optical fiber 8 and the feeding rate of glass materials 9, 10 are unbalanced, air pressure in the communicating vessel 6 changes, the level difference DELTAh is develops on the liquid level in the U-shaped pipe. Since the difference DELTAh is proportional to a change of the liquid level of fused glass, change of the liquid level in the U-shaped pipe mounted on the outside of the furnace is detected and the feeding rate of the glass material is controlled to keep the liquid level constant at all times, and the optical fiber wherein the outer diameter ratio of the core glass to the coating glass is fixed can be spinned.