Patent GB-1000884-A (GB)
Title: Producing sheet glass
IPC: C03B15/02
Filed: 1963-09-12
Abstract: <PICT:1000884/C1/1> <PICT:1000884/C1/2> <PICT:1000884/C1/3> A method of continuously producing sheet glass comprises flowing a stream of molten glass successively through melting, refining and cooling chambers into a working receptacle, continuously drawing a sheet upwardly from the molten glass in the working receptable through a drawing chamber, deflecting the sheet about a bending member and conveying it horizontally through an annealing lehr, and is characterized by sealing off the atmosphere above the molten glass in the refining chamber from that in the cooling chamber and in also sealing off the atmosphere above the molten glass in the cooling chamber from that in the drawing chamber.  The refining chamber 25 is connected by a cooling chamber 28 to a relatively shallow draw pot 29 above which is a drawing chamber 30 where is continuously drawn a sheet 32 which passes over a backing roll 37 and passes into a horizontal flattening chamber 38 and Lehr 40.  The draw pot works with a Colburn Machine and is supported upon stools 33 in a heated pot chamber 34.  To seal off the atmospheres in the refining and cooling chambers, the two chambers are separated by an arch 42 which has two walls 43, 44 extending between the furnace side walls and depending to just above the glass level, there being a C-bar 46 in the space between the walls 43, 44 a horizontal leg 47 of which is disposed below the glass surface.  A cover 48 is placed over the C-bar.  The cooling chamber decreases in depth to that of the draw pot 29 and is separated from the drawing chamber by a wall 50.  On the cooling chamber side of the wall is a skimmer bar 51 extending across the exit to seal off the atmospheres between the chambers. The skimmer bar 51 has a tube 52 of rectangular cross-section and a depending flange 53 which is below the glass surface, the flange and tube being made of a heat-conductive material (e.g. platinum or an alloy of iron, chromium aluminium) and the tube 52 being heated by a burner to prevent build up of devitrefied glass.  The draw pot, which is enclosed by side walls 55, and machine enclosure 56 has located across the entrance to the draw chamber 30 a hollow heated muffle tip-tile 59 of rectangular cross-section <PICT:1000884/C1/4> made of stainless steel.  The tile is suspended close to the glass surface by adjustable rods 65 and seats on the tank side walls by recess portions 69, 72 in its base and side walls. An alternative form of the tile may have a corrugated base and a flange which dips into the glass, Fig. 13 (not shown).  Further edge heaters 81 are provided at the exit of the cooling chamber.  To seal off the atmosphere in the pot chamber completely from that in the draw pot a rear liptile 94 is seated over the junction between the drawing chamber 30 and the flattening chamber 38.  The tip-tile comprises a refractory block 95 which is supported upon a ledge 97 and held by a key 98 in a carrying frame 96.  The lower edge of the frame has a sealing member 101 which is submerged in the glass.  The tile 94 is accurately positioned by means of brackets 103, 104 and tubes 106 see Figs. 9 and 10 (not shown).  The flattening chamber 38 and lehr 40 have the customary suspended barriers 125 and barricades 127 upon the floor, beneath the sheet. In order to prevent any air turbulence within the tunnel there are provided cut-offs 128 which form vents in the tunnel, and also close off the pot chamber exhaust ducts 111 which run through the lehr floor.  There is formed beneath the ribbon a chamber 134 by having a pair of screens 133, vertically adjustable, which cooperate with a bulk head 129.  To maintain the temperature of the chamber, burners 140 are included.  The screens each have a pair of parallel conduits 142, Fig. 20 (not shown) for the circulation of a heat-absorbing medium. Above the sheet and acting in conjunction with the screens 133 is an adjustable curtain 156 having cooling ducts 159, and also an adjustable heat shield 157 having cooling ducts 171. The bending roller 37 is cooled by a cooler 112 which allows the passage of an inert gas, such as sulphur dioxide, this helping to lubricate the roller and prevent the glass sheet from sticking thereto.  More than one refining chamber 25 may lead off from the melting chamber, thus allowing more than one sheet to be drawn simultaneously (see Fig. 1).