| 摘要 |
Methods and apparatus for controlling the stress in, and the shape of, the glass ribbon (15) formed in a downdraw glass manufacturing process (e.g., the fusion downdraw process) are provided. In certain embodiments, the control is achieved by cooling the bead portions (21a, 21b) of the ribbon (15) at a rate which provides a heat flux Q″b at the thickest part of the bead (23a, 23b) which is given by Q″b=Q″q+&Dgr;Q″, where (i) Q″q is the heat flux at a transverse position adjacent to the bead portion (21a, 21b) at which the ribbon's thickness equals 1.05*tcenter, where tcenter is the final thickness at the ribbon's center line (17), and (ii) &Dgr;Q″≧(tb/tq−1)Q″q+10 kilowatts/meter2, where tb is the thickness of the thickest part of the bead portion. The cooling can take place along the entire length of the ribbon (15) or at selected locations, e.g., in the portion (50) of the draw which includes the glass transition temperature region (31) or the portion (60) of the draw where individual glass sheets (13) are cut from the ribbon (15).
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