Patent GB-694891-A (GB)
Title: Improvements in the manufacture of glass
Inventor: SEYMOUR JOHN LAWRENCE
IPC: C03B5/225
Filed: 1951-02-12
Abstract: 694,891. Glass refining. SOC. ANON. DES. MANUFACTURES DES GLACES ET PRODUITS CHIMIQUES DE ST. - GOBAIN CHAUNY, ET CIREY. Feb. 12, 1951 [Feb. 10, 1950], No. 3417/51. Class 56. [Also in Group XI] In the manufacture of glass a stream of molten glass is caused to flow from a melting zone through a refining zone being restricted in cross sectional area in relation to its length as it flows through the refining zone, and an electric current such as to heat the glass to its refining temperature before it reaches the end of the refining zone is. caused to pass through the restricted stream transversely of its direction of flow. As shown in Fig. 1 a tank 10 receives molten glass from an outside source or by melting solid raw materials 12, e.g. by burners 13, and a carbon tube 14 extends downwards from the bottom of the tank at a point remote from the batch feeding point. This tube, which may be of graphite, is cylindrical and is connected at its lower end to a feeder 15. A rod electrode 16, preferably of graphite, passes through the sole of the feeder and extends axially and adjustably into the tube. An A.C. generator 17 supplies current through leads 18, 19 to the tube and electrode which constitute outer and inner electrode walls between which the glass flows in an annular stream of uniform cross section. The intensity of the heating is regulated by controlling the size of the current, the duration of heating, and the degree of insertion of the electrode 16. Bubbles produced during refining escape to and then from tank 10. In the construction shown in Fig. 2 the batch is melted in tank 30 and passes through a refining tube 39 of graphite insulated at 40 to a storage tank 42 where it is drawn as a sheet 44 or fed at 45. A refractory sleeve 37 extends adjustably through the roof of tank 30 at an angle of 45 degrees and a conductor 35 extends through the sleeve and is connected to a rod electrode 36 fixed to the end of the sleeve. Refractory non-conducting guides 38 may support the electrode axially of tube 39, and the lower end of the electrode may pass through the bottom of tank 42. A battery of three tubes 39 is described. The inner and outer electrodes may be in the form of concentric tubes, with the glass passing through the space between them, in order to reduce the difference between the areas of the electrodes. Alternatively a tube may be used having non- conductive walls 60, and conductive walls 61 connected to opposite sides of an A.C. source 62, as in Fig. 5. In Fig. 6 the melting tank 71 communicates with the reservoir 72 by a cylindrical carbon tube 75, preferably of graphite, which has longitudinal slots 76 and is connected by a lead 77 to an A.C. source 78. An electrode 79 extending axially through the tube is supported by a refractory bracket 80 at one end and by a hollow refractory support 81 at the other, a lead 82 passing from the source 78 to the electrode through support 81. Gas liberated during refining escapes through slots 76 which may have a nozzle-like construction. The tube 75 may be enclosed in a chamber 84 which may be heated or contain inert gas to prevent oxidation of the tube which may have an external refractory coating.