GB674990A - Glass furnace - Google Patents

Abstract

674,990. Glass manufacture. GLASS FIBERS, Inc. Sept. 17, 1949 [Oct. 30, 1948], No. 23985/49. Class 56. [Also in Groups XI and XII] In the manufacture of glass the glass making materials are introduced into one end of the tank 2 and melted and heated on the surface by heat from combustion above the surface, and the lower stratum of the melted glass is heated by means of electric currents flowing in the glass, the current being controlled to maintain a small temperature gradient with the temperature of the lower strata less than the temperature of the upper strata, and the molten glass is extracted from the other end of the tank. The electrodes 8 are mounted in the side walls of the tank below the mid-depth of the melted material, and the discharge opening extends from above the level of the electrodes to a level beneath the surface of the molten glass. The raw materials are introduced through the opening 3 in the tank enclosure 1 and heated by gas, or vaporised oil mixed with air, from burners 4, the exhaust passing through the opening 5 to the chimney 6. The lower stratum of the molten glass 7 is heated by currents passing through the evenly spaced electrodes 8 which are preferably of molybdenum and water cooled. The glass passes through the shallow gate 9 to the forehearth 10, and is discharged through the opening 11. The forehearth has a cover 12 and skimmer block 13. Electrical power is fed through leads 15 to the primary winding 16 of transformer 17, the secondary winding 18 of which is connected through leads 19, 21 and branch leads 20, 22 to the electrodes 8. The current is controlled by varying the voltage for which taps 23 are provided. If the decrease in resistance of the glass with an increase in temperature is sufficient to cause instability an impedence 24, which may be an inductive reactor with or without a saturable core, may be included in a lead to the furnace on the primary or secondary side of the transformer. Further control may be exercised by including reactors or resistors in the leads to the individual electrodes. The reactor 24 serves to limit the current flow if the resistance decreases.