Overflow downdraw glass forming method and apparatus

An apparatus for forming sheet glass, comprising

• a trough including sides attached to a structure including downwardly sloping sides converging along a downward direction to a root of the structure, the structure including a wedge-shaped cross-section taken perpendicular to a length of the trough;
• at least one inflow measurement device to measure a mass flow of air into a muffle door chamber;
• and
• at least one outflow measurement device to measure a mass flow of air out of the muffle door chamber;
• the outflow measurement device to regulate cooling air flowing out of the muffle door chamber equal to a measured value that flows into the muffle door chamber such that no air leaks through cracks and openings between the muffle door chamber and glass flowing off the root.

An apparatus for forming sheet glass, comprising:

• a trough including sides attached to a structure including downwardly sloping sides converging along a downward direction to a root of the structure, the structure including a wedge-shaped cross-section taken perpendicular to a length of the trough;
• at least one inlet end compression block located at an inlet end of the structure, the at least one inlet end compression block including at least two compression blocks that are angled inward relative to one another in a direction of the length of the trough;
• and
• at least one far end compression block located at an opposite end of the structure as the at least one inlet end compression block.

An apparatus for forming sheet glass, comprising:

• a muffle including an interior area and a muffle door, the muffle door including a muffle door chamber at least partially defined by a front wall of the muffle door, the front wall positioned between the muffle door chamber and a muffle door zone, and an exit port to remove air form the muffle door chamber without entering the interior area of the muffle;
• a trough positioned within the interior area of the muffle, the trough including sides attached to a structure including downwardly sloping sides converging along a downward direction to a root of the structure, the structure including a wedge-shaped cross-section taken perpendicular to a length of the trough, and the muffle door zone is aligned with the root in the downward direction to allow a glass sheet being drawn off the root to exit the interior area of the muffle;
• a plurality of cooling tubes that are each positioned to direct cooling air into the muffle door chamber and against the front wall of the muffle door;
• and
• at least one outflow measurement device to measure a mass flow of air out of the muffle door chamber through the exit port.