Patent ID: 8347654

Claim:
A vacuum degassing apparatus for molten glass, comprising: a vacuum degassing vessel having an uprising pipe and a downfalling pipe attached thereto; an upstream side pit configured to supply molten glass to the uprising pipe; and a downstream side pit configured to receive molten glass from the downfalling pipe, wherein the vacuum degassing apparatus further comprises a separating mechanism and a returning pipe, the separating mechanism is configured to separate a part of molten glass moving from the downfalling pipe to the downstream side pit, the returning pipe is positioned to return molten glass separated by the separating mechanism to the upstream side pit, and the downstream side pit has a side portion having an opening forming an end of the returning pipe, wherein the vacuum degassing apparatus further comprises a conduit structure for molten glass, which is positioned on a downstream side of the downfalling pipe, the conduit structure comprises an outer pipe made of platinum or a platinum alloy, a part of which functions as the separating mechanism, the conduit structure has a double pipe structure comprising an inner pipe and the outer pipe, formed at least in a downstream end portion of the conduit structure, the inner pipe has an open end at each of an upstream end and a downstream end, the outer pipe has an upstream end that is an open end, and a downstream end that is a closed end, the inner pipe perforating through a part of the closed end, and the outer pipe has an opening in a downstream end portion at a position facing the opening provided in the side portion of the downstream side pit such that the separated molten glass separated by the separating mechanism flows through the opening of the outer pipe and the opening of the downstream side pit into the returning pipe.