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Title: Method for producing a glass flow of high homogeneity in a tank furnace and an arrangement for carrying out the method
Claims: The embodiments of the invention in which an exclusive property or privelege is claimed are defined as follows: 1. A method for producing a glass flow of high homogeneity in a tank furnace in which the surface layer of the glass melt is separated from the glass flow intended for processing, characterized in that within the working part of the tank, which contains the refined glass, at a removal point spaced upstream from the downstream end wall of the tank, a selected layer of glass underneath the surface layers and above the bottom layers is drawn off, at least in part, and supplied to the processing station, while said surface layers above said selected layer are allowed to pass on downstream beyond said removal point and are returned from a point in the tank downstream of said removal point to a point upstream from said removal point, said bottom layers below said selected layer also being returned to a point upstream from said removal point. 2. A method in accordance with claim 1, characterized in that said surface layers are diverted towards the sides of the tank at a point downstream of said removal point and are returned to the front of the tank where flow is initiated. 3. A method in accordance with claim 2, characterized in that the return of the surface layers of the molten glass is carried out by means of ducts running adjacent to the side walls of the working part of the melt tank. 4. A method in accordance with claim 3, characterized in that adjacent to said downstream end wall of the working part of the melt tank means are provided for effecting a temperature gradient, running from the center of the tank to the side walls thereof. 5. A method in accordance with claim 4, characterized in that the removal of the selected glass layer is carried out at such a distance from said downstream end wall of the working part of the melt furnace that at said removal point, the glass flows substantially in the direction of the longitudinal flow axis of the melting tank and mixing of the glass flows has not yet taken place. 6. A method in accordance with claim 5, characterized in that the selected layer glass flow removed is passed on in the direction of the longitudinal axis of the melt tank through a duct, passing through said downstream end wall of the melt tank, to the processing station. 7. A method in accordance with claim 5, characterized in that the selected layer glass flow removed is passed in a vertical direction through a duct passing through the bottom of the melt tank to the processing station. 8. A method in accordance with claim 2, characterized in that the return of the surface layers of the molten glass is carried out within the working part of the melt tank itself using natural return flow along the side walls of the working part. 9. A method in accordance with claim 8, characterized in that adjacent to said downstream end wall of the working part of the melt tank means are provided for effecting a temperature gradient, running from the center of the tank to the side walls thereof. 10. A method in accordance with claim 1, characterized in that adjacent to said downstream end wall of the working part of the melt tank means are provided for effecting a temperature gradient, running from the center of the tank to the side walls thereof. 11. A method in accordance with claim 1, characterized in that the removal of the selected glass layer is carried out at such a distance from said downstream end wall of the working part of the melt furnace that at said removal point, the glass flows substantially in the direction of the longitudinal flow axis of the melting tank and mixing of the glass flows has not yet taken place. 12. A method in accordance with claim 1, characterized in that said downstream selected layer glass flow removed is passed on in the direction of the longitudinal axis of the melt tank through a duct, passing through the end wall of the melt tank, to the processing station. 13. A method in accordance with claim 1, characterized in that selected layer glass flow removed is passed in a vertical direction through a duct passing through the bottom of the melt tank to the processing station. 14. A glass melt tank for effecting the selected separation of a layer of molten glass located intermediate the top and bottom surface layers of the melt tank, said melt tank comprising: an upstream end away from which glass is intended to flow and a downstream end towards which glass is intended to flow; an upper end wall at said downstream end, against which the upper layers of glass flow as they flow downstream in said tank; a pair of spaced side walls and a bottom; a removal duct leading out of the melt tank for conducting the flow of molten glass to a processing station, said removal duct leading out of the melt tank for conducting the flow of molten glass to a processing station, said removal duct including an opening into said tank whose cross-section in its vertical extent is substantially less than the vertical extent of the normal glass bath level for the tank and whose cross-section is arranged underneath the surface layers of the glass melt to be eliminated and above the bottom layers of the glass melt to be eliminated; and said removal duct opening into said tank being spaced at a horizontal distance upstream from said upper end wall of the glass melting tank such that the surface layer glass currents in the tank run substantially in the longitudinal flow direction of the melting tank as they pass over said opening of said duct. 15. A melt tank in accordance with claim 14 characterized in that a return duct is provided adjacent each of said side walls and to the outside of said tank, each of said side walls including a downstream opening at the downstream end of said tank adjacent said upper end wall and downstream from said removal duct opening which opens into said return duct and an upstream opening at the upstream end of said tank which opens from said return duct into said tank whereby the flow of glass is from the upstream end of said tank to the downstream end thereof, through the downstream opening in the sidewalls thereof, through the return ducts and back into the tank at the upstream openings from said return ducts into said tank. 16. The melting tank in accordance with claim 14 characterized in that said duct for conducting the flow of selected glass to the processing station is arranged horizontally underneath the surface layer of molten glass to be separated and includes an upper wall defining a bottom for the surface layers of glass which are to be diverted. 17. The melting tank in accordance with claim 14 characterized in that said removal duct for conducting the flow of selected glass to a processing station is defined in part by a block of a generally L-shaped cross-section, the vertical limb of said block projecting above the intended surface level for glass in the tank and said horizontal limb projecting towards the upstream end of said tank at a level just underneath the intended bottom level for the upper surface layers of glass to be separated. 18. The melt tank of claim 14 which includes heating means positioned on said upper end wall thereof at a point above the intended surface level for the glass in said tank and being located generally centrally of said upper end wall whereby the flow of surface layers of glass in the tank from the center of the upper end wall thereof towards the side walls thereof is encouraged. 19. The melting tank according to claim 14 characterized in that cooling means are positioned on each of said side walls of said tank generally adjacent said upper end wall of said tank whereby the flow of glass in the upper surface layers of glass in said tank from the center of said upper end wall towards said side walls of said tank is encouraged. 20. The melting tank according to claim 14 characterized in that said removal duct extends generally vertically from said removal duct opening out through said bottom of said tank. Other info: Inventors: Heitzer, Xaver (near Cologne, DT) Bourggraff, Robert (Cologne, DT) Application Number: 529845 Filing Date: 1974-12-05 Publication_date: 1976-02-10 Assignee: Erste Deutsche Floatglas GmbH. & Co. OHG (DT) Primary Class(es): 65/135.1 65/136.4, 65/337, 65/346, 65/347 Other Classes: US Patent Ref:
Other Refs: Primary Examiner: Kellogg, Arthur D. Assistant Examiner: Attorney: Price, Heneveld, Huizenga & Cooper |
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