The present invention alters the flow path at the inlet of the sheet glass forming
apparatus to improve quality. The bottom of the downcomer pipe is preferably shaped
to alter the character of the vortex flow in the quiescent flow zone between the
pipes. In another embodiment, a bead guide provides hydraulic stresses that are
in opposition to the surface tension stress and thus reduces the influence of surface
tension on the formation of thick beads on the edges of the sheet. The present
invention also measures the temperature of the glass by immersing thermocouples
in the glass, at locations where any defects caused by the immersion are in the
glass that forms the unusable edges of the sheet. In another embodiment, the support
structure for the trough is altered to substantially reduce the aging of the trough
due to thermal creep.
