GB937697A - Improvements in or relating to methods and apparatus for down-drawing a sheet of glass - Google Patents

Abstract

937,697. Drawing sheet glass. GLAVERBEL. Jan. 8, 1962 [Jan. 21, 1961], No. 733/62. Class 56. In the downward drawing of a sheet of glass from a bulb of viscous glass hung on the bottom of a horizontal member of material to which the glass sticks and extending over the whole length of a slot through which molten glass flows continuously, the member is in the form of at least one rotating roller, rotated at such speed that some of the viscous glass forming the bulb is moved upwardly therewith to engage fresh glass issuing from the slot. Molten glass 2 in a furnace 3 is fed downwardly through a slot 4 covered with electrically heated foils 5 of platinum or like material, the width of the slot being adjustable by horizontal movement of the refractory block 27. As shown in Fig. 3 and in Figs. 1 and 6 (not shown), the glass impinges on a single refractory roller 6 rotated at an adjustable speed in the direction of arrow Y to take up part of the glass adhering thereto from the bulb 7 from which a sheet 8 is drawn by rollers 28 the edges being maintained by knurled wheels 32 and the sheet cooled by coolers 31 in the usual way. The roller 6 is adjustable horizontally so as to lie under the centre of slot 4. The thickness of the sheet 8 is varied by varying the speed of rotation and by making the roller vertically adjustable to vary the distance from the slot 4. The roller 6 is also continuously reciprocated parallel to its axis in order to assist in evening out the thickness of the glass layer on the roller and therefore of the sheet 8. In Fig. 3, the thickness of the glass layer is further limited by carbon members 35, 36 secured to the furnace and block 27, an atmosphere of nitrogen being maintained through duet 37 to prevent oxidation. The glass does not stick to the carbon. In Fig. 4, not shown, a pair of rollers 6<SP>1</SP>, 6<SP>11</SP>, as in Fig. 7, arranged so that the distance between them is less than the width of the slot 4, rotate in opposite directions Y<SP>1</SP>, Y<SP>11</SP> to draw up glass from bulb 7 between them. In Fig. 5, not shown, the pair of rollers 6<SP>1</SP>, 6<SP>11</SP> have limiting carbon members 35, 36. As shown in Fig. 7, in addition to the members 35, 36, a pair of carbon rollers 38<SP>1</SP>, 38<SP>11</SP> are provided to even out the sheet 8, the rollers rotating as at R<SP>1</SP>, R<SP>11</SP> against the flow of the glass. In Fig. 6, not shown, a single roller 6, carbon members 35, 36 and rollers 38<SP>1</SP>, 38<SP>11</SP> are used.