Patent GB-368089-A (GB)
Title: Improvements in or relating to apparatus for feeding molten glass
IPC: C03B7/07
Filed: 1931-03-23
Abstract: 368,089. Glass manufacture. HARTFORD-EMPIRE CO., 333, Homestead Avenue, Hartford, Connecticut, U.S.A.- (Assignees of Henry, K. M. ; 354, San Benito Way, San Francisco, U.S.A.) March 23, 1931, No. 8903. Convention date, April 29, 1930. [Class 56.] Delivering molten metal. - A forehearth, through which molten glass flows from a furnace to a discharge orifice, is provided with a cooling section adjacent the furnace and a heating section in its forward portion, and means are provided for passing an electric current through the glass in order to raise it to a predetermined temperature before discharging it through the orifice. Baffles are provided to prevent stratification of the glass into zones of different temperature, and thermoelectric devices are provided for automatically maintaining the glass at a predetermined temperature. The cooling section B, Fig. 1, of the forehearth receives molten glass through a submerged port 6 formed in the wall A of the furnace, and temperature of the glass in this section may be raised, if necessary, by gas burners inserted in openings 8, 9 formed in the tile 7 that covers the forehearth. The burner may be removed from the opening 8 if the admission of cold air is required for cooling the glass more rapidly. The back part 5 of the floor of the section B slopes, as shown, and the front part consists of a block 11 having an inclined face to deflect the current of glass in an upward direction. Another block 12 projects downwards into the glass and, in addition to skimming the glass, it also separates the space above the glass in section B from that in section C. The blocks 11, 12 act as baffles to prevent stratification of the glass. The heating-section, C, of the forehearth is subdivided into three or more zones 30, 40, 50, and electrodes 14 are fitted in recesses in the side walls. Electricity is passed between opposite electrodes through the glass to raise its temperature. Each electrode consists of a graphite plate 15, Fig. 6, into which a graphite rod 16 is screwed, and a protective tube of steel or other heat-resisting metal is shrunk around the graphite rod. The plate 15 is covered with an electrode material to protect it from the glass, and the faces 15, 19 are set in a recess to protect the coating 19 from erosion by the flowing glass. Blister traps 20 are positioned above the electrodes to receive the gas bubbles which rise through the glass from the faces of the electrodes and to conduct the gas into the atmosphere. The discharge orifice 38 is surrounded by a ring or wall 43 on which a cylinder 34 rests, and a plunger 39 of the usual kind reciprocates within the cylinder. One or more openings 35, 36 are formed in the wall of the cylinder to allow the glass to flow to the orifice. The purpose of the cylinder is to guide the glass so that it flows in definite paths in which thermocouples 77 are placed. In order to keep the temperature of the glass approximately constant, the circuits connected to the electrodes 14 are controlled by the thermocouples 77 which are inserted in openings in the roof of the forehearth and dip into the glass. Variations of the temperature of the glass cause variations of the current generated by each thermocouple, and the resulting movement of the arm 76 of a galvanometer 67 either makes or breaks the circuit of a pair of opposite electrodes 14.