OVERFLOW DOWN-DRAW WITH IMPROVED GLASS MELT VELOCITY AND THICKNESS DISTRIBUTION

摘要

An apparatus for making a glass sheet using overflow fusion down-draw process comprising an inlet assembly having an elliptic cylindrical section coupled to a transition section which is, in turn, coupled to an open end of an open channel of an isopipe, and an overflow fusion down-draw process for making glass sheet. The glass melt flow has a high surface velocity profile conducive to the formation of a glass ribbon over the surface of the weirs and the wedge side surfaces with the desired mass distribution.

主权项

1. A method for making a glass sheet by an overflow process using a forming body comprising a trough-shaped part and a wedge-shaped part below the trough-shaped part, the trough-shaped part having a first trough side wall and a second trough side wall over a trough bottom surface defining an open channel having an open end, the open channel having a center plane, the first trough side wall having a first internal trough surface, a first trough top surface and a first external trough side surface, the second trough side wall having a second internal trough surface, a second trough top surface and a second external trough side surface, the wedge-shaped part having a first wedge side surface connecting with the first external trough side surface, and a second wedge side surface connecting with the second external trough side surface, the first and second wedge side surfaces sloping downwardly to join at a root line, the method comprising:
(i) delivering a stream of a molten glass via a closed channel into the open channel of the trough-shaped part through the open end of the open channel; (ii) allowing the molten glass to flow over at least part of the first trough top surface, down along the first external trough side surface to form a first glass ribbon over the first external trough side surface; and (iii) allowing the molten glass to flow over at least part of the second trough top surface, down along the second external trough side surface to form a second glass ribbon over the second external trough side surface; wherein in step (i), the closed channel and the open channel are arranged such that the velocity distribution of the stream of the molten glass in a vertical reference plane tangential to the center plane of the open channel at a point where overflow starts on the first trough top surface is such that the average velocity of the molten glass in the top one fourth of said stream of the molten glass in said vertical reference plane is higher than the average velocity in the bottom one fourth of said stream of the molten glass in said vertical reference plane immediately above the trough bottom surface.