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Method and apparatus for the manufacture of large optical grade SiO.sub.2 glass preforms

  • US 5,312,471 A
  • Filed: 12/02/1991
  • Issued: 05/17/1994
  • Est. Priority Date: 12/02/1991
  • Status: Expired due to Fees
First Claim
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1. A process for producing an optical quality SiO2 glass ingot comprising:

  • rotating a cylindrical horizontal furnace about its central axis, said furnace having spaced electrodes extending along said central axis into the furnace interior;

    establishing a gas plasma arc between said electrodes to heat the furnace;

    feeding SiO2 into said furnace and melting said SiO2, within said furnace at a temperature of at least 2400°

    C. to form a hollow cylindrical melt by centrifugal force generated by said rotating, while controlling the rate of said feeding to provide a rate of decrease of the inner radius of said cylindrical melt no greater than the escape rate toward the inner cylindrical surface of said melt at said temperature for the smallest bubble compatible with the desired optical quality of the glass ingot product, said rate of said feeding being decreased in proportion to the rate of change of surface area of the inner surface of the hollow cylindrical melt.

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