Patent ID: 8661851

Claim:
A method for continuously creating a structure on a face of a ribbon of glass using an impression device, wherein: the impression device is positioned in a zone situated after a bath of tin on which the ribbon is formed, wherein between the bath of tin and the impression device, the ribbon is at a mean temperature T 1 that is insufficient for impressing onto the ribbon a pattern of the impression device according to the nature of the pattern to be engraved, a pressure between the impression device and the ribbon, and a duration of contact between the ribbon and the impression device, the face of the ribbon that is to be engraved is heated by a heating device upstream of the impression device so as to raise, at a start of impression, a partial thickness of the ribbon to a temperature T 2 >T 1 that is sufficient for impressing onto the ribbon the pattern from the impression device according to the nature of the pattern to be engraved, the pressure between the impression device and the ribbon, and the duration of contact between the ribbon and the impression device, and the structure is engraved onto the face of the ribbon by the pattern of the impression device, and, during the heating, a thermal flux, q ht ,is transmitted to the ribbon by the heating device over a length in the direction of travel, length heated , wherein the values of the thermal flux and the heated length are determined by the steps of: selecting an “impression number”, N imp , which ranges between 0.05 mm −1 and 2.00 mm −1 , the “impression number” N imp being defined by the formula: N imp = depth T ⁢ ⁢ 2 diffusivity thermal · speed length heated , where depth T2 denotes a thickness of glass to be raised to the temperature T 2 in order to impress the structure, speed denotes a speed of travel of the glass ribbon, and diffusivity thermal denotes the thermal diffusivity of the glass, calculating length heated based on the selected N imp value and known values of depth T2 , diffusivity thermal , and speed, calculating the thermal power to be injected per meter width of ribbon, Q imp , from the formula: Q imp =ER ·( Hg ( T 2)− Hg ( T 1))·speed·depth T2 ·density glass , where Hg(T 2 ) and Hg(T 1 ) are an enthalpy of the glass at a temperature T 2 and a temperature T 1 , respectively, and where ER is an energy ratio determined from the calculated length heated value by the formula: ER = 4.21 · 10 - 2 · [ ⁢ depth 12 2 · speed ( 6.67 · 10 20 · length heated + 2 · 10 21 · dist imp ) · diffusivity thermal ] - 0.3397 , and determining the thermal flux, q ht , from the calculated values of Q imp and length heated by the formula: q nt = Q imp length heated .