Patent GB-350930-A (GB)
Title: Improvements in or relating to electric furnaces and methods for making glass and the like
IPC: C03B5/027
Filed: 1930-03-06
Abstract: 350,930. Glass manufacture. RAEDER, J. K. B., Holmenkollen, near Oslo. March 6, 1930, No. 7411. [Class 56.] Production of metal.-A furnace for melting and refining glass in which the molten material serves as an electric heating resistance comprises a melting and refining chamber 1 connected at the bottom by a passage 2 with a conditioning chamber 3 which may have a laterally extending forehearth 4, Fig. 3, associated with glass-feeding means. A gate 6 may regulate the flow of glass to the forehearth from the chamber 3. The forehearth 4 is formed with a discharge outlet 5. A cooling space 7, in which may be fitted water-cooling pipes 7a, may be provided between the chambers 1, 3 and passage 2. The terminals 10 of a pair of electrodes 11 extend through aligned openings 9 in the side walls of the chamber 1 from which the electrodes are spaced so that a layer of molten glass will lie between each electrode and the chamber side wall. The terminals 10 may be water-cooled. Holddown members 16 are provided if the electrodes are of carbon or graphite, and the electrodes 11 are continuously submerged and protected against oxidation by the molten glass. Batch, preferably pre-heated, is fed through openings 19 in the furnace roof to form heaps which are partially submerged as shown in Fig. 1. The glass, after melting, passes downwardly through a refining zone to the passage 2 and chamber 3 and may move horizontally to the forehearth 4. Electrodes 23 may be arranged at opposite ends of the chamber 3 and are held submerged by stops 24 so that electric current may be used to regulate the temperature of the glass in the chamber 3. Electric current may also be passed from an electrode 11 to an electrode 23 so that the passage 2 is heated. The electrodes 11, when of carbon or graphite, may be formed of individual strips 44 secured together by dowels 45 as shown for a modified construction of electrode 11a, shown in Fig. 5. A number of terminals 10 may be provided for each electrode. The construction shown in Figs. 6 and 7 is a furnace for the use of three-phase alternating current. A melting and refining chamber 50 is connected at its lower end by a throat 51 with the bottom of a conditioning chamber 52 which is provided with means 53 for drawing glass upward in sheet form. A bridge 54 extends transversely of the chamber 52 and comprises a bore 55 for circulating cooling fluid. Electrodes 56 are symmetrically disposed round the chamber 50 below the level of the melted glass. Each electrode 56 is preferably of triangular shape in horizontal section, and may have a downwardly and outwardly inclined contact surface 58, Fig. 7. Each electrode 58 has a terminal 59. The electrodes 58 are held down by blocks 60 and rest on support blocks 61. A feed opening 62 with a depending lip 63 is provided in the top member of the furnace. Preheating means for the batch may comprise a rotary frame 66 which carries wheels 67 rolling on an annular track 68 concentric with the feed opening 62. The frame 66 carries depending batch spreading and feeding blades 69 which spread the batch on a plate 65 and feed it to the opening 62. The batch is fed from a hopper 77 to a stationary plate 78, and the frame 66 carries a wiper 79 which sweeps batch so that it will fall through an open part 80 of the frame 66 on to the plate 65. The chamber 52 may have submerged electrodes 82. In a modified construction the top of the chamber 50 may have a number of feed openings and a number of symmetrically spaced throats 51 may connect with chamber 50 with tempering chambers 52. Specification 262,535, [Class 39 (iii), Heating by electricity], is referred to.