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Title: Novel flat glass-producing furnace
Claims: We claim: 1. In a continuous tank-type furnace producing flat glass of high temperature melting, highly volatile glass batch making ingredients comprising a melter, a canal and flat glass forming means, said melter comprising: a. a back end wall and front end walls, b. a top and bottom wall, two generally parallel side walls which define a channel in which the molten glass proceeds from the back wall to the front end walls, said front end walls having an opening therethrough to permit the passage of glass to flow into the canal which has a narrower cross-section than the melter, the improvement comprising tapered front end walls converging inwardly towards one another from the width of the melter to the width of the canal, such that the angle the front end walls make with the side walls is at least about 140.degree.. 2. The furnace of claim 1 in which the angle the front end walls make with the side walls is within the range of 150.degree. to 160.degree. inclusive. 3. The furnace of claim 1 which has heaters along substantially the entire length of the melter. 4. The furnace of claim 3 in which the heaters are overhead burners. 5. The furnace of claim 4 which has a length-to-width ratio in the melter within the range of 4 to 6:1. 6. The furnace of claim 5 which has a melter width to canal width ratio within the range of 2 to 4:1. 7. The furnace of claim 6 in which the ratio of a. the furnace distance from the back end wall to the point at which the front end walls begin to converge inwardly to b. the furnace distance from the point at which the end walls begin to converge inwardly to the beginning of the canal is within the range of 6 to 8:1. 8. A method of making glass comprising: introducing into a melting zone a glass batch containing an ingredient which is volatile at the elevated temperatures required for melting over a prolonged time so as to cause an adverse loss of said ingredient from the glass, said melting zone having an initial portion thereof defined by spaced substantially parallel boundaries extending toward a molten glass outlet, heating said glass batch until it is in a molten state, flowing said molten glass through said initial portion of said melting zone toward the end of the melting zone and said molten glass outlet along a substantially straight linear path of flow, and applying forces to said flowing molten glass at the terminal end of each said boundary of the initial portion of said melting zone and maintaining said forces so as to divert and constrict the flow of molten glass to said outlet, said forces being sufficient to divert the flow of the molten glass at each side edge thereof along lines of flow forming an angle of at least about 140.degree. with the line of flow of the molten glass along the edge thereof at the adjacent boundary of said melting zone, whereby to streamline the flow of portions of the molten glass along said side edges and thereby decrease the average residence time of said glass portion and decrease the loss of volatilizable components of the molten glass. 9. The method of claim 8 in which the advancing flow of glass is continuously heated by heaters as it advances through the melter. 10. The method of claim 9 in which the heating is from overhead burners. 11. The method of claim 8 wherein said application of forces is sufficient to reduce the width of the glass flow to one half to one fourth the width of flow through the initial portion of said melting zone. 12. The method of claim 8 wherein said step of introducing batch ingredients into a melting zone includes introducing ZnO as a component of the batch. 13. The method of claim 12 wherein molten glass is withdrawn through said outlet with the following composition:
COMPONENT PERCENT BY WEIGHT ON THE OXIDE BASIS
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SiO.sub.2 64-74
Al.sub.2 O.sub.3
15-23
Li.sub.2 O 3.3-4.8
ZnO 1-3.8
TiO.sub.2 1.2-3.0
ZrO.sub.2 0-2.
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Other info: Inventors: Cerutti, Richard L. (Seminole, PA, US) Demarest, Jr., Henry M. (Natrona Heights, PA, US) Application Number: 458911 Filing Date: 1974-04-08 Publication_date: 1976-02-03 Assignee: PPG Industries, Inc. (Pittsburgh, PA) Primary Class(es): 65/135.1 65/136.3, 65/337, 65/339, 65/346, 373/27 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Bashore, S. Leon Assistant Examiner: Miga, Frank W. Attorney: Millman; Dennis G., Uhl; William J. |
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