| 摘要 |
<p>1531743 Refining molten glass PILKINGTON BROS Ltd 21 Jan 1976 [31 Jan 1975] 4361/75 Heading C1M Molten glass 25 is refined in refining zone 13, the upper regions of the melt being heated (e.g. from ports 26) and the lower regions of the melt (constituting a return flow) being cooled through a heat-conducting support material 19, and the length of zone 13, the depth of the glass in zone 13 and the temperature difference between the inlet and outlet of zone 13 being controlled so that the ratio of forward flow to return flow is 2-6:1. Preferably support material 19 is molten tin, the cooling being by air circulation through channels 21. Preferably the refining zone 13 is shallower than melting zone 12 but deeper than conditioning zone 14 (in which there is preferably no return flow). The temperature at the upper melt surface (e.g. 1460‹ C.) may be up to 200‹ C. more than that at the bottom of zone 13. The atmosphere above zones 12, 13, 14 may be divided by platinum barriers (not shown).</p> |
