Apparatus and method for tempering glass sheets
AssigneePPG Industries Ohio, Inc.
InventorsWilliam R. Krall, Jr., William R. Siskos, Thomas M. Sailock, Joseph Medzius, DeWitt W. Lampman
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Abstract
A method of tempering a glass sheet heated to a tempering temperature includes cooling the glass sheet at a first heat transfer coefficient at a first quench station and cooling the glass sheet at a second heat transfer coefficient at a second quench station downstream of the first quench station. The second heat transfer coefficient is greater than the first heat transfer coefficient. In a multistage process of the invention, a plurality of quench stations could be used with each downstream quench station having a larger heat transfer coefficient than the previous upstream quench station.
Claims8
A method of tempering a glass sheet heated to a tempering temperature, comprising:
- (a) cooling the glass sheet with a first gaseous cooling fluid at a first heat transfer rate for a first period of time using a first heat transfer coefficient in the range of 33 Btu/hr/ft2/° F. to 129 Btu/hr/ft2/° F.;
- (b) cooling the glass sheet with a second gaseous cooling fluid at a second heat transfer rate after step (a), with the second heat transfer rate being greater than the first heat transfer rate and using a second heat transfer coefficient in the range of 144 Btu/hr/ft2/° F. to 235 Btu/hr/ft2/° F.;
- and
- (c) cooling the glass sheet with a third gaseous cooling fluid at a third heat transfer rate after step (b), with the third heat transfer rate being greater than the second heat transfer rate and using a third heat transfer coefficient in the range of 272 to 388 Btu/hr/ft2/° F.,
- wherein the first gaseous cooling fluid, the second gaseous cooling fluid, and the third gaseous cooling fluid can be the same or different, and
- wherein cooling with the first gaseous cooling fluid, cooling with the second gaseous cooling fluid, and cooling with the third gaseous cooling fluid are each conducted such that the glass sheet in each case has a maximum surface tension of ≦5,000 psi.
Dependencies are inferred from the claim text.