GB899115A - Process and apparatus for making sheet glass - Google Patents

Abstract

899,115. Glass - melting furnace walls. GLACES DE BOURROIS. Jan. 26, 1961, No. 3092/61. Class 51 (2). [Also in Group XXIII]. For the drawing of sheet glass, a vitreous melt produced in a tank furnace to give a depth of melt in the range 120 to 150 centimetres, has a high temperature zone at a refining portion and a stream of liquid glass is withdrawn from the melt through an outlet in the furnace at a distance less than 15 metres from the high temperature zone and from which continuous sheet of glass is drawn, a descending flow of glass diverted from the surface stream being cooled to accelerate the velocity of the descending flow and consequently the velocity of the surface stream. A tank furnace 5 for molten glass 10 comprises floor 16, arched roof 13 and terminal wall 12, furnace gases being admitted through ports 17. The floor 16 between the hot point 11 of the furnace and the wall 12 has a heat-insulating coating 15 to reduce heat losses in the return current 27 of liquid glass deflected from the supply current 22 flowing towards the feeding channel 24 and drawing chamber 25, the return current being deflected downwardly at 26 along the terminal wall 12 and upwardly at 28 towards the hot point 11. To accelerate the flow of glass currents, the descending current 26 is cooled by cooling the wall 12 by cold air blown through pipes 19 against the outer surface 18, the thickness of the wall being only about 15 cm. The wall 12 is situated less than 15 m. from the hot point 11 and has its upper edge 20 about 30 cm. below the surface 46 of the bath 10 when the bath is about 150 cm. deep. The depth of the stream 23 supplying the feeding channel 24 and drawing chamber 25 may be varied by means of a register 21 formed by a plurality of individual vertically adjustable blocks 29, each block 29 being screwed to clamping plates securing a suspension rod 30. Each rod 30 passes through a friction bushing 43 in the web 31 of a channel iron 32 supported on posts 33 to straddle the channel 24 and abut the top wall 41 of the furnace 5. The roof 35 of the channel 24 is provided with a slot which acts as a guide for the blocks 29. Each block 29 may be raised or lowered manually or by automatic devices to regulate the depth of the stream 23 throughout its width and thereby compensate for variations in thickness of the drawn glass sheet. The blocks 29 may be made of corundum, mullite or zirconia for temperatures in excess of 1200‹ C. or vitreous silica for temperatures between 1000‹ C. and 1200‹ C.