DE19920438A1 - 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 - Google Patents

Abstract

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.

Description

The invention relates to a method of making a multi-layer (i.e., multi-layer composite) fibrous web; preferably paper or cardboard web. The invention also relates to an apparatus for performing the above method.

The starting point of the invention is the publication DE 44 02 273 A1 (= EP 0665 330; PA 10041). The following is known from this document for the purpose of producing a multi-layered fibrous web: A first layer is formed in a first twin-wire forming zone between two endless wire mesh belts (in short: between two "screens"). Likewise, a second layer is formed in a second twin-wire forming zone between two screens, after which the two layers are mixed together in a transfer zone and fed to further treatment stations. Referring to FIGS. 1 and 2, the total of 4 DE'273 endless screens are required for said purpose. According to FIG. 3 of DE'273, attempts have already been made to get by with only three screens, one of the screens running through both twin-wire forming zones. However, this arrangement has the disadvantage that the first layer formed in the first twin-wire forming zone also has to pass through the second twin-wire forming zone. As a result, the formation of the second layer cannot take place in the desired manner, namely by uniform drainage on both sides (ie evenly through both sieves). Rather, the drainage takes place only on one side directly through one of the two sieves and on the other side with only very little intensity through the previously formed first layer and through the other sieve.

The invention is therefore based on the object of a method and an apparatus for Manufacture to provide a multi-ply fibrous web, wherein each at least one of the two outer layers is formed in a twin-wire forming zone, immediately between two sieves each without the presence of a previously formed other layer. This is supposed to be with only three seven may be possible, so that the investment and operating costs compared to previously be reduced.

This object is achieved by the method defined in claim 1 or by that in claim 20 defined device solved. The invention is based on a simple he seeming sequence of different process steps. It is essential that the second Sieve - after forming the first layer in the first twin-wire forming zone - initially from separated from the first layer and then fed to the second twin-wire forming zone, where after the second layer formed there is fed to a transfer zone by means of the third screen in which the two layers are muddled together. For the invention is also characteristic that in the transfer zone be outside the loops of the three screens sensitive rubber roller is provided, which removes the second layer from the third screen and passes to the first layer. This rubber roller can be used as a bare roller (i.e. with a closed roller) nem roll shell) or it is provided with a porous cover or it a porous or substantially smooth belt runs over this roller. According to a continuation The transfer zone can be designed as a shoe press (with a wide nip) be, wherein preferably the rubber roller is a shoe press roller. For this design a transfer zone is sought according to claim 23 general protection, d. H. independently of the inventive idea defined according to claim 1 or 20.  

It is also characteristic of the invention that - seen in side view - the three screens and the said rubber roller form an intermediate space which is only open laterally, in which the second headbox (which is required to form the second layer) is arranged.

Exemplary embodiments and further refinements of the invention are the subject of dependent claims. It goes without saying that protection is also sought for those from the dependent features of the device. These will described below with reference to the drawings.

Each of FIGS. 1 to 8 shows - in a schematic side view - a device for producing a multi-layer fibrous web, referred to briefly as a "multiple layer genformer", preferably in front of paper or cardboard web. The Fig. 9 shows in tabular form a plurality of Kombinationsmög possibilities.

Common to all designs is a first twin-wire forming zone 13 . Two sieves 11 , 12 run through these, namely a lower first sieve 11 and an upper second sieve 12 . The twin-wire zone 13 begins at the circumference of a forming roller 14 , which is located in the loop of the first wire belt 11 . Here, a Fasersus pension is introduced directly between the two screens 11 and 12 by means of a first headbox 10 . So it is a so-called gap former. Deviating from this, a so-called hybrid former could also be provided, in which the lower sieve forms an (at least short) single-sieve pre-dewatering section.

Behind the forming roller 14 , the two screens 11 and 12 run over the strips of a drainage box 15 (located in the loop of the second screen 12 ). The latter cooperates with a so-called formation box 16 located in the loop of the first screen 11 . Its essential elements are strips, which are preferably pressed pneumatically (or with the aid of springs) to the first screen 11 . The drainage elements 15 , 16 are known; see e.g. B. DE 40 02 304 (PA 06622) or DE 40 05 420 (PA 04713). The overhead drainage box 15 is preferably bulged downwards. Then the two screens 11 and 12 run together with the first layer A formed between them via further drainage elements, for. B. suction box 17 and vacuum cleaner 18th The latter ensures that the first layer now continues with the first wire 11 , while the second wire 12 is fed to a second twin wire forming zone 23 with the aid of guide rollers 19 .

The first screen belt 11 runs together with the first layer A from the separating suction device 18 to a transfer zone described below with a rubber roller 6 , then via further dewatering elements, e.g. B. suction boxes 9 and wire suction roll 8 to a Bahnabnahmein direction 5 , after which the first wire 11 runs over several guide rollers 7 back to the forming roller 14 . The rubber roller 6 is formed in Fig. 1 as a "closed" roller, that is, its roller jacket is smooth and comes into direct contact with the second layer.

While the first twin-wire forming zone 13 extends essentially in the horizontal direction, the second twin-wire forming zone 23 extends approximately vertically from bottom to top, similar to the known construction according to EP 0489094, Fig. 2 (PA 04668). In turn, a forming roller 24 , a drainage box 25 with forming box 26 , suction box 27 and vacuum cleaner 28 are provided . At the beginning of the second twin-wire forming zone 23 , a pulp suspension is again added between the second wire 12 and a third wire 21 by means of a headbox 20 , so that a second layer B is formed between the two wires 12 and 21 . The separating suction device 28 ensures that the second layer continues to run with the third screen 21 , guided by a plurality of guide rollers 29 . The second screen 12, which is separated from the second layer, runs back to the beginning of the first twin-screen forming zone 13 with the aid of a plurality of guide rollers 22 . The boxes 25 and 26 can usually be operated without negative pressure. In contrast, in the first (horizontal) twin-wire forming zone 13, the box 15, which drains upwards, is usually subjected to negative pressure.

The third screen 21 brings the second layer B into contact with the rubber roller 6 already mentioned. This separates the second layer B from the third sieve and transfers it to the first layer B (with the first sieve 11 ) arriving. In contrast to FIG. 1, the rubber roller 6 is wrapped a little by the first sieve 11 , so that under the longitudinal tension of the first sieve 11 ensures an intimate connection of the two layers. The two-layer web formed in this way, consisting of a “lower outer layer” A and an “upper outer layer” B, is now guided to a web take-off device 5 by means of the first screen 11 via further drainage elements 9 , 8 . From here, the web is in a known manner, for. B. by means of a felt to the subsequent treatment station (z. B. press section).

Are shown schematically in FIG. 1 means 4 for cleaning the screens comprising spray pipes and water-collecting container.

The construction according to FIG. 2 differs from that according to FIG. 1 by three features . On the one hand, the second twin-wire forming zone 23 A does not extend vertically but, like the first twin-wire forming zone 13 , essentially in the horizontal direction. This arrangement has the advantage of a lower overall height. On the other hand, one of the two headboxes or (as shown) both headboxes 10 A and 20 A are designed as multi-layer (e.g. two-layer) headboxes. This is in contrast to the headboxes 10 and 20 , which are designed according to FIG. 1 as a single-layer headbox. According to FIG. 2, each layer A or B is composed of several layers A1 + A2 or B1 + B2 when forming in the forming zone 13 or 23 A. The finished fibrous web thus consists, for example, of a total of four layers. It goes without saying that multilayer headboxes can also be used in the arrangement according to FIG. 1. Another difference from FIG. 1 is that the rubber roller 6 'is designed as an "open" roller (for example covered with a sieve stocking).

The design according to FIG. 3 differs from that according to FIG. 1 in that a fourth screen 31 and a fifth screen 32 form a third twin-wire forming zone 33 , which in turn is associated with a headbox 30 . The two screens 31 and 32 in turn run together over a forming roller 34 , an overhead drainage box 35 with a forming box 36 arranged underneath, and a suction box 37 and a separating suction device 38 . The third layer C thus formed is first combined with the second layer B brought up by the third sieve 21 by means of the lower, fourth sieve 31 , which wraps around a guide roller 39 and the rubber roller 6 A. Then the second layer B and the third layer C are co-molded with the first layer A. If all headboxes are single-layer headboxes, the result is a three-layer web consisting of lower outer layer A, middle layer B and upper outer layer C. In the example shown in FIG. 3, all headboxes are 10 A as two-layer headboxes , 20 A, 30 trained. The result is a three-layer fibrous web composed of a total of six layers A1 + A2 + B1 + B2 + C1 + C2. Numerous variants are conceivable if only one or only two of the three headboxes are designed as multi-layer headboxes; see the table in FIG. 9, which shows many possible combinations that may result from FIGS. 1 to 3.

The three-layer fibrous web is guided by means of the first screen 11 via further drainage elements 9 , 8 to the web take-off device 5 . The fourth wire 31 runs from the rubber roller 6 A via guide rollers 41 back to the forming roller 34 . The fifth screen 32 likewise runs from the separating suction device 38 via a plurality of guide rollers 40 back to the forming roller 34 . The rubber roller 6 A can (as in Fig. 1) have a smooth roller shell. Instead, according to FIG. 3, it can have a casing provided with grooves or bores, which can temporarily store water; or the rubber roller 6 A is designed as shown as a suction roller (with suction zone 46 ). - Deviating from FIG. 3, only the lower sieve could be provided to form the third layer, the upper sieve 32 thus being omitted.

The design according to FIG. 4 differs from that according to FIG. 1 only in that the second layer transported by means of the third screen 21 in the direction of the rubber roller 6 does not come into direct contact with the roller shell of the rubber roller but with one around the rubber roller 6 A. band 42 . This band unites the two layers and immediately separates from the second layer. The band 42 can be formed as a felt or as a sieve (similar to the sieve 31 of FIG. 3) or as a relatively dense, smooth band. Referring to FIG. 5, the belt, the function takes the same time the pick-up felt 42 A in the sheet-removal device 5. FIG. 6 shows a variant of FIG. 5, in which the belt 42 A not only gushes the two layers together when it runs over the rubber roller 6 B, but immediately afterwards the multilayer fibrous web formed in this way leads from the rubber roller 6 B to the subsequent treatment station .

The design shown in FIG. 6 can be further developed as shown in FIG. 7 as follows: The rubber roller 6 C is now designed as a shoe press roller (known, for example, from DE 37 08 189; PA 04165), which is associated with a the loop of the lower, first screen 11 located counter-pressure roller 43 cooperates and thereby forms a "wide nip". The roller 43 is preferably formed as a perforated suction roller. In addition, a felt belt 44 wrapping around the counterpressure roller 43 can be provided. The required vacuum can be applied by means of an external suction box 45 . The shoe or wide-nip press designed in this way (similar to DE 197 02 574; PA 10473) not only serves to aggregate the two layers but also to further drain them. Referring to FIG. 7, the thus-treated multi-layer fiber web is fed directly downstream of the nip by means of the belt 42 A subsequent treatment station. Deviating from this, in the construction according to FIG. 8 - similarly to FIG. 4 - a band 42 is provided which is separated from the formed fibrous web after the two layers have been brought together in a wide nip. An additional take-off felt belonging to the web take-off device 5 is therefore provided.

Claims (23)

1. A method for producing a multi-layer (ie composed of several layers) fibrous web, preferably paper or cardboard web, with the following procedural steps:

• a) a first layer (A) is formed by means of a first headbox ( 10 ) and by means of a first twin-wire forming zone ( 13 ) between a first wire ( 11 ) and a second wire ( 12 ):
• b) the second screen ( 12 ) is then separated from the first layer and the first layer is continued by means of the first screen ( 11 );
• c) a second layer (B) is formed by means of a second headbox ( 20 ) and by means of a second twin-wire forming zone ( 23 ) between the second wire ( 12 ) and a third wire ( 21 );
• d) then the second screen ( 12 ) is separated from the second layer and the second layer is continued by means of the third screen ( 21 );
• e) the two layers (A and B) are mixed together in a transfer zone, after which the multi-layer fibrous web (AB) thus formed is fed to further treatment stations.

2. The method according to claim 1, characterized in that before each twin-wire forming zone ( 13 , 23 ) each of the screens ( 11 , 12 , 21 ) is fed free of a previously formed layer of this twin-wire forming zone. 3. The method according to claim 1 or 2, characterized in that the layers (A and B) are gassed together by removing the second layer (B) by means of a rubber roller ( 6 ) from the third screen ( 21 ) and on the first layer (A) passes. 4. The method according to claim 3, characterized in that a smooth roller is used as the rubber roller ( 6 ), the closed roller shell of which comes into direct contact with the second layer (B) and passes it to the first layer ( Fig. 1). 5. The method according to claim 3, characterized in that an "open" roller ( 6 ') is used as the rubber roller, the roller shell of which is preferably coated with a screen fabric, for. B. Egoutteurwalze ( Fig. 2). 6. The method according to claim 3, characterized in that one leads over the rubber roller ( 6 A) flax tape ( 31 , 42 , 42 A) which comes into direct contact with the second layer (B) and passes it to the first layer . 7. The method according to claim 6, characterized in that a porous tape, for. B. felt ( 42 A) or sieve ( 31 ). 8. The method according to claim 7, characterized in that one as a rubber roller open roller used, the jacket z. B. has grooves or holes or z. B. is designed as a suction roll.   9. The method according to claim 6, characterized in that the tape is a non-absorbent or only slightly absorbent, essentially smooth tape ( 42 ) ( Fig. 4). 10. The method according to claim 6, characterized in that one uses a decrease felt ( 42 A), which feeds the multilayer fibrous web of the subsequent treatment station. 11. The method according to claim 3, characterized in that one guides the first screen ( 11 ) in the transfer zone over a part of the circumference of the rubber roller ( 6 ). 12. The method according to claim 11, characterized in that a contact pressure is exerted in the transfer zone exclusively by means of the longitudinal tension of the first screen ( 11 ) on the rubber roller ( 6 ). 13. The method according to claim 11, characterized in that in the transfer zone a contact pressure is exerted by means of a press roller ( 43 ) located in the loop of the first screen on the rubber roller ( 6 C) ( Fig. 7, 8). 14. The method according to claim 13, characterized in that the press roll ( 43 ) and the rubber roll ( 6 C) together form an extended press nip in the web running direction. 15) Method according to claim 14, characterized in that a shoe press roll is used as the rubber roll ( 6 C). 16. The method according to any one of claims 13 to 15, characterized in that a water-absorbing endless belt (z. B. felt 44 ) with the press roller ( 43 ) through the transfer zone. 17. The method according to claim 6, characterized in that a fourth sieve ( 31 ) is used as the belt, on which a third layer (C) has been formed and that the first layer is gassed with the second layer (B) and that then the layers merged with the first layer (A) were collapsed ( Fig. 3). 18. The method according to claim 17, characterized in that one forms the third layer (C) if in a twin-wire forming clay ( 33 ), namely between the fourth wire ( 31 ) and a fifth wire ( 32 ). 19. The method according to any one of claims 1 to 18, characterized in that at least one of the layers is formed by means of a multi-layer headbox ( 10 A, 20 A, 30 ), so that the layer in question (z. B. A) at least two Has layers (A1, A2) of different or similar solids (fiber and / or fillers). 20. Device for producing a multi-layer (ie composed of several layers together) fibrous web, preferably paper or cardboard web, with the following characteristics:

• a) to form a first layer (A), a first headbox ( 10 ) and a first twin-wire forming zone ( 13 ) with a first wire ( 11 ) and with a second wire ( 12 ) are provided;
• b) at the end of the first twin-wire forming zone there is a first separating device ( 18 ) which separates the second wire ( 12 ) from the first layer (A) which continues with the first wire ( 11 );
• c) in order to form a second layer (B), a second headbox ( 20 ) and a second twin-wire forming zone ( 23 ) are provided, through which said second wire ( 12 ) and a third wire ( 21 ) pass;
• d) at the end of the second twin-wire forming zone ( 23 ) there is a second separating device ( 28 ) which separates the second wire ( 12 ) from the second layer (B) which continues to run with the third wire ( 21 );
• e) in a transfer zone there is a rubber roller ( 6 ) which removes the second layer (B) from the third screen ( 21 ) and gasses it with the first layer (A) (brought up by means of the first screen ( 11 )).

21. The apparatus according to claim 20, characterized in that the rubber roller ( 6 ) outside the loops of the three screens ( 11 , 12 , 21 ) is arranged. 22. The apparatus according to claim 20 or 21, characterized in that the second headbox ( 20 ) is arranged within an intermediate space which is limited by the three screens ( 11 , 12 , 21 ) and by the rubber roller ( 6 ). 23. Device for producing a multilayer, for. B. two-layer fibrous web, with several (e.g. two) forming zones for forming one of the layers and with at least one a transfer zone in which at least two layers are mixed together characterized in that the transfer zone by a shoe press known per se is formed with a press nip extended in the direction of web travel.