Paper/cardboard web drying station has the web carried between two blankets in a serpentine path with separation of the outer blanket at the deflection point between drying sections for positive web guidance at high speeds

摘要

To dry a web (12), of paper or cardboard, it is passed through a series of successive drying sections with a deflection path between each section. In the drying sections, the web (12) is carried between at least two blankets (14,16). At the deflection paths between the drying sections, the outer blanket is detached from the web (12) and then returned in place against it. The outer blanket (14,16) is deflected in its path by an outer deflection roller (18), with a smaller dia. than the inner deflection roller (22) for the inner blanket (14,16) and the web (12). The outer blanket (14,16) is detached from the web (12) as the web arrives at the inner deflection roller (22), and is returned to the web as it leaves the inner roller. The direction of the outer blanket movement path is unchanged, or only slightly altered, at the arrival and departure points of the web (12) at the inner deflection roller (22). The inner blanket (14,16) and the web (12) form an angle around the inner deflection roller (22) at the arrival and/or departure zone of = 5 deg and pref. = 2 deg . In its path through the drying stage, the web (12) is deflected in alternating directions, in a serpentine path with deflections of -90 deg and pref. -120 deg and especially -150 deg . Two blankets (14,16) carry the web (12) between them through the drying stage, with the same deflections as the web. In all the drying sections, the web (12) follows a path which deviates slightly from a straight line, with a support or guide roller for the web (12) between the blankets (14,16). At least one of the blankets (14,16) has neutral fibers on the side towards the web (12). The inner deflection rollers (22) each are a suction roller. Each inner deflection roller (22) has a suction unit (52) at it. At the deflection path around the inner deflection roller (22), suction is applied to the web (12) through the inner blanket (14,16) using a suction unit (52) and pref. a suction box and/or air is blown through the outer blanket (16,14) at the web (12) by air jets (54) and/or air jets (56) between the web (12) and the outer blanket (16,14). The web (12) is treated with hot air and/or hot steam delivered through the blankets (14,16). An Independent claim is included for a web drying assembly, at a papermaking or cardboard prodn. machine, where the web (12) is carried between two blankets (14,16). Preferred Features: The assembly is a convection drying station for the web (12), with at least one hood (34) in at least one drying section to deliver hot air and/or hot steam to the web (12).