CORE TUBE TOP COVER FOR GLASS POROUS BASE MATERIAL SINTERING FURNACE, AND GLASS POROUS BASE MATERIAL SINTERING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a core tube top cover for a sintering furnace to produce glass products by sintering a glass porous base material, which is structured to prevent atmosphere from windingly coming into the furnace and a work gas from leaking into atmosphere, also, to provide a manufacturing method for the glass porous base material free from impurities capable of sintering the base material without coming in of atmosphere windingly into the furnace and the leakage of the work gas while setting the pressure of exhaust gas to ca -500 pa by using the above top cover and which method enables to extend life of the core tube. SOLUTION: At the top cover, a small chamber equipped with an exhaust port, a small chamber with a sealing gas introduction port, and a small chamber without a port are installed in this order. In each chamber, an airtight ring is inserted loosely and movably into a seed rod. Only at the airtight ring in the chamber with the exhaust port, an exhaust gas passage is installed on a lower side of the ring toward the circumference direction. Clearance between the airtight ring and the seed rod is set at 0.15-0.25 mm. Airtightness is improved in the upper chamber, pressure difference is kept in the middle chamber by not installing a gas passage on a lower side of the airtight ring, and exhaust is easily made in the lower chamber with the gas passage toward the circumferential direction.