Method of continuously producing flat glass by rolling

A rolling method of continuously producing flat glass, said method consisting of the steps of:

• a) supplying a fluid glass sheet from a glass melt tank;
• b) rolling the fluid glass sheet issuing from the glass melt tank between an upper shaping roller and a lower shaping roller to shape and to calibrate the glass sheet in a roller gap between the upper shaping roller and the lower shaping roller, wherein said upper shaping roller is arranged above said lower shaping roller, said glass sheet passes under the upper shaping roller and over the lower shaping roller, and wherein said upper shaping roller and said lower shaping roller are each hollow, provided with an interior, and made of a porous open-pored material having a pore structure;
• c) generating a gas cushion between said fluid glass sheet and said upper shaping roller from an evaporating liquid by supplying said evaporating liquid to said interior of said upper shaping roller at a fluid pressure controlled, so that a phase boundary between vapor from the evaporating liquid and the evaporating liquid is maintained within the porous open-pored material of the upper shaping roller;
• d) controlling a gas pressure of said gas cushion between said fluid glass sheet and said upper shaping roller in order to completely avoid contact between said fluid glass sheet and said upper shaping roller so as to form a glass surface on an upper side of the glass sheet having a quality corresponding to that of a fire-polished surface;
• e) generating another gas cushion between said fluid glass sheet and said lower shaping roller from said evaporating liquid by supplying said evaporating liquid to said interior of said lower shaping roller at another fluid pressure controlled so that a phase boundary between vapor from the evaporating liquid and the evaporating liquid is maintained within the porous open-pored material of the lower shaping roller;
• f) controlling a gas pressure of said another gas cushion between said fluid glass sheet and said lower shaping roller, so that a linear contact area is formed between said fluid glass sheet and a roller surface of said lower shaping roller, said linear contact area extending parallel to an axis of said lower shaping roller;
• g) controlling a width of said linear contact area between said fluid glass sheet and said lower shaping roller according to a speed and viscosity of the glass sheet, so that the glass sheet is transported without slipping and the glass sheet is sufficiently cooled so as to be dimension stable;
• and
• h) after the glass sheet is rolled between the upper shaping roller and the lower shaping roller conveying in the glass sheet into a cooling oven by means of conveying rollers located downstream of the upper shaping roller and the lower shaping roller, in order to obtain the flat glass.