Paper web transfer strips are formed at the edges of the web with a stronger pulp than used for the body of the web to thread the web through the stations after a stoppage and then be separated for return to the pulper

摘要

To form a transfer strip at a fiber web, of paper or cardboard or tissue, the fiber suspension (25) forming the pulp has a higher strength potential at the zone (24.1) of the web (12) to form the cut transfer strip (23), than in at least one other zone of the web (12). The pulp (25) with an increased strength potential is formed by increasing the volume of the fiber suspension (25.1), the addition of strengthening chemicals such as for an increased wet strength, an adhesive and/or bonding agent, the introduction of natural and/or synthetic threads on the required orientations, grinding the fiber material of the suspension (25), adding stronger fiber materials, using added fibers which easily shed water during papermaking to achieve their strength more rapidly and/or reducing the ratio of filling materials in the fiber suspension (25) in the zones (24.1) where they are cut away to form the transfer strip. The increased volume of fiber suspension (25.1) is by raising the delivery speed of the pulp into the fourdrinier section (14). The strengthening chemicals are added directly at the stock inlet (11), in the stock inlet zone, at the fourdrinier section (14) and/or at the drying station. Reinforcement threads and other materials are added at the zone of the stock inlet (11) and/or at the fourdrinier section (14), oriented on the direction (S) of fourdrinier travel. The surplus strips (23) are trimmed from the web (12) as edge strips by a cutting blade, beater, water jet or laser cutter or a combination of at least two methods. The strips (23) are carried with the web (12) at least as far as the drying station zone or the end of it., and the discarded strip material is returned to the pulper. Or the edge strips are carried with the web through a web polishing calender, with =4 calender rollers and preferably =8 rollers, and the discarded edge strips are returned to the pulper. The edge strips (23) can remain with the web as far as the roll winder, to be wound as well, after the calender. During transfer movements, the edge strips pass through a coating machine. The transfer strips (23) are spread out to a required width, preferably the width of the web (12), after satisfying at least one quality and/or production characteristic e.g. the surface roughness, the lateral shrinkage profile or the fiber orientation, and the travel speed. The duration of the application is controlled, such as the time span of pulp suspension production with an increased strength so that, on starting up after a stoppage or after a web break, the strip strengthening activity is maintained until the web reaches the winder and winding has started. An independent claim is included for a papermaking machine with at least one channel for the stronger pulp suspension at the distribution tube in the stock inlet (11), or at the flow channel, between the flow channel and the turbulence generator, or in the flow channel in front of the pulp outflow gap. Preferred Features: The stock inlet (11) has a dividing wall along the direction (S) of fourdrinier travel, to give a separate flow of stronger suspension (25). The stock inlet (11) delivers a layer of fiber suspension (25.1) on to the moving fourdrinier, together with a narrower stock inlet (11.1) to deliver a stronger pulp (25) along the edge strip zone. The narrower stock inlet (11.1) is either after the stock inlet (11) for the web (12) or flanks the stock inlet (11). An applicator can be after the stock inlet (11), in the direction (S) of fourdrinier travel, as a spray jet or an unwinder, to deliver the stronger suspension (25) to the web (12) at the edge zones of the fourdrinier (14) where the side strips (23) are to be developed, and the applicator can be after the point where the two fourdriniers are separated from each other. The flow of the stronger suspension is controlled by volume and/or time at the stock inlet (11) and/or the narrower stock inlet (11.1) and/or the applicator. The width (B) of the edge strip (23) is 50-1000 mm and especially 100-800 mm and preferably 250-750 mm.