Production of multi-layer paper or cardboard web, uses separate stock inlets and double-fourdrinier zones for each layer to be couched into multi-layer web using only three fourdriniers for two layers

摘要

To produce a multi-layer paper or cardboard web, the first layer (A) is developed with an initial stock inlet (10) and a double-fourdrinier zone (13) where the web is formed between two fourdriniers (11,12). At the end of the zone (13), the second fourdrinier (12) is detached (18) from the web, which is carried onwards by the other fourdrinier (11). The second layer (B) is developed by a second stock inlet (20) and a further double-fourdrinier zone (23), to be carried between the second fourdrinier (12) and a third fourdrinier (21), and the second fourdrinier (12) is separated (28) for the web to be carried onwards by the third fourdrinier (21). The two web layers (A,B) are brought together at a transfer zone where they are couched together into a multi-layer web to be carried to further processing stations. In front of each double-fourdrinier zone (13,23), each fourdrinier (11,12,21) is fed in clear of a previously-formed web. The two web layers (A,B) are couched together where the second layer (B) is stripped from the third fourdrinier (21) by a couch roller (6) and transferred to the first layer (A). The couch roller (6) has a smooth and closed mantle, in direct contact with the second web layer (B) to transfer it to the first layer (A). Or the couch roller has an open mantle, pref. covered with a woven mesh such as a watermark roller. A belt such as of linen, a porous blanket or a fourdrinier can pass round the couch roller, in direct contact with the second web layer (B). The belt can be smooth with little or no water absorption. The belt can be a pick-up blanket, which carries the multi-layer web onward for further processing. The couch roller can be open with a mantle fitted with grooves or drillings, or it can be a suction roller. The first fourdrinier (11) passes round part of the couch roller (6) circumference, at the transfer zone, and a pressure is applied at the transfer zone wholly by the longitudinal tension of the first fourdrinier (11) on the couch roller (6) or a press roller against the couch roller within the loop of the first fourdrinier, so that the press and couch rollers together form an extended press gap in the direction of web travel. The couch roller can be a shoe press roller. A water-absorbent continuous blanket can be passed through the transfer zone with the press roller. A fourth fourdrinier can be used to give a third web layer to be couched with the second layer (B) to be combined together with the first layer (A). The third layer is formed in a double-fourdrinier zone, using a fourth and fifth fourdrinier. At least one of the layers is developed from a multi-layer stock inlet, so that each layer is itself in a multi-layer structure of different or similar solid contents of fibers and/or filling materials. An Independent claim is included for a papermaking or cardboard production machine with separate stock inlets (10,20) and double-fourdrinier zones (13,23) to give web layers (A,B) to be couched together. Preferred Features: The couch roller (6) is outside the loops of the continuous fourdriniers (11,12,21). The second stock inlet (20) is within an intermediate zone defined by the three fourdriniers (11,12,21) and the couch roller (6). The transfer zone for the multi-layer web is a conventional shoe press, with an extended press gap in the direction of web travel.