HIGH-CONVECTION GAS JET NOZZLE SECTION FOR SHEET-LIKE MATERIAL GUIDED OVER ROLLS AND METHOD OF USING SAME

摘要

A high-convection gas jet nozzle section for a sheet-like material guided over rollers, in particular for thermal prestressing or tempering of thin flat glass sheets, comprises a lower nozzle field having nozzle ribs disposed centrally parallel between the rollers and provided with nozzle apertures and an upper nozzle field of which the nozzle ribs provided with nozzle apertures are arranged symmetrically to the vertical axis of each respective lower nozzle rib; the nozzle bottoms of the upper nozzle ribs have the cross-section of a letter "M" extended by a center strip; the width of the nozzle bottom of the upper nozzle ribs is greater than the horizontal distance between the rollers and smaller than the roller pitch; the center strip and the two upwardly tilted inner legs of the upper nozzle bottoms are provided with nozzle apertures; and the smallest distance of the upper nozzle ribs from the upper side of the material is greater than the smallest distance of the lower nozzle ribs from the lower side of the material; the downwardly directed outer legs of the upper nozzle bottoms constrict the downflow region for the gas emerging from the nozzle apertures of the upper nozzle ribs on either side of the upper nozzle ribs, giving as a whole a very symmetrical gas action on the material from above and below.