Chapter 12. Lift-Out Rolls and Lehr Rolls for Production of High-Quality Class

  1. John B. Wachtman Jr
  1. D. Bucko1,
  2. J. M. Vignot2,
  3. P. Guillo2,
  4. D. Gautier2,
  5. Y. Takahashi3 and
  6. S. Inoue3

Published Online: 26 MAR 2008

DOI: 10.1002/9780470314814.ch12

A Collection of Papers Presented at the 56th Conference on Glass Problems: Ceramic Engineering and Science Proceedings, Volume 17, Issue 2

A Collection of Papers Presented at the 56th Conference on Glass Problems: Ceramic Engineering and Science Proceedings, Volume 17, Issue 2

How to Cite

Bucko, D., Vignot, J. M., Guillo, P., Gautier, D., Takahashi, Y. and Inoue, S. (1996) Lift-Out Rolls and Lehr Rolls for Production of High-Quality Class, in A Collection of Papers Presented at the 56th Conference on Glass Problems: Ceramic Engineering and Science Proceedings, Volume 17, Issue 2 (ed J. B. Wachtman), John Wiley & Sons, Inc., Hoboken, NJ, USA. doi: 10.1002/9780470314814.ch12

Author Information

  1. 1

    Vesuvius, Beaver Falls, Pennsylvania

  2. 2

    Vesuvius, Feignies, France

  3. 3

    Asahi Glass, Tokyo, Japan

Publication History

  1. Published Online: 26 MAR 2008
  2. Published Print: 1 JAN 1996

ISBN Information

Print ISBN: 9780470375419

Online ISBN: 9780470314814

SEARCH

Keywords:

  • fused silica ceramic rolls;
  • glass defects;
  • thermal expansion;
  • asahi float lines;
  • ceramic sleeve

Summary

An improvement in the quality of various types of glasses produced by the float process is obtained by the use of fused silica ceramic rolls. Substantial reductions in glass bottom surface defects have been achieved by replacing traditional steel rolls in both the lift-out position and lehr by using a fused silica sleeved roll to improve glass contact conditions in the hottest part of the lehr. Pure fused silica is an ideal material for this application because it is not reactive with sulfur and sulfilde, and it is chemically inert with tin compounds. For both applications, the roll design has been optimized by using a sleeved roll composed of a metallic core, a ceramic sleeve, and end cap fixtures to ensure low mechanical stresses and consistency of straightness over time. The quality of the glass surface is ensured by the ceramic sleeve having virtually no expansion and the nonexistence of ceramic surface deformation. The control of surface defects and the microstructure of the ceramic sleeve are keys to reduce crack propagation in the sleeve and ensure a life span of the ceramic sleeve that is compatible with the application. Ceramic lift-out and lehr rolls have been tested in various production conditions; the main benefits obtained are the reduction of the bottom surface imprinting noted with thick glass and the reduction of glass defects due to tin oxide buildup for high-quality thin glass. Furthermore, low thermal conductivity of the ceramic sleeve reduces the overcooling of glass bottom surface, which eliminates stress cracks.