CN1043178A - The forming method of paper or board web and device - Google Patents

Abstract

Method and apparatus for forming fibrous paper or board in a paper machine, with an initially horizontal lower wire circuit and an associated upper wire circuit. The fibrous layer passes through a directly extending support system after initial dewatering in the single wire dewatering zone, which prevents dewatering by gravity through the lower wire. When producing high grammage paper, the paper web is sent to the twin-wire dewatering zone. This area includes the support system and the opposite water absorption and chopping board device in the web, through which the web is dehydrated. When producing thin paper, the water absorbing and cutting board device is separated from the paper, and only the lower wire is in contact with the paper. This is followed by a twin-wire dewatering section, completed by a short upward segment of the forming rolls. The twin wire forming zone is then curved downwards guided by large radius forming plates.

Description

The invention relates to a method for forming a fibrous paper or board web. This method is used in the wire section of paper machines or similar equipment. The network department is composed of the lower network circuit and the upper network circuit. The off-grid loop works jointly with the off-net loop. In this method, the fiber suspension from the headbox of the paper machine is fed to the initial part of the upper run of the lower wire circuit, which constitutes the first single wire dewatering zone. The partially dewatered fibrous layer is then sent to a second dewatering zone. In this area, make the upper circuit cover the above-mentioned partially dehydrated fiber layer, so that the fiber layer continues to be dehydrated in the second dehydration zone, and then the upper circuit is separated from the formed fiber layer, and the fiber layer continues with the stroke of the lower wire circuit. move.

The invention also relates to a web forming apparatus for carrying out the method of the invention. It comprises a netting circuit with a substantially horizontal upward stroke, a netting device which works jointly with the netting circuit and is provided with a netting circuit, and a net head box. The headbox is used to send the jet of fiber suspension to the beginning of the single wire on the upper stroke of the lower wire circuit. Thereafter, a twin-wire forming area is also formed between the joint trip of the netting and the netting. In the double-wire forming area, there are various components placed in the lower wire circuit and the upper wire circuit for dehydration.

In the oldest method of forming paper or board webs, the paper web is formed on a horizontal so-called fourdrinier former wire section, the fiber suspension is only in one direction over the entire length of the wire section - i.e. downwards Dehydrate. The quality of the top and bottom of the paper produced in this way is different from each other, the top of the paper is smoother than the bottom, and the bottom of the paper has more or less clear traces produced by the forming wire, the so-called web trace. In terms of fibrous structure, the upper and lower sides of the paper are also different from each other, the upper side of the paper contains much more short fine fibers and fillers than the lower side, this is due to the fact that most of the lower fibers are washed away during unidirectional dehydration Caused. For printing paper, it is important to have the same quality as possible on both sides. The difference between the two sides of the paper is called "unequal-sidedness".

In the prior art, it is known that some paper machines can be used to reduce the non-uniformity of the paper. These machines can be divided into two main groups, namely dedicated twin-wire formers and so-called hybrid formers. In special formers, the web is formed all the way between the two wires. In a hybrid former, the web is first formed on a wire, and the partially formed web is then passed between the two wires to finally solidify the mutual position of the fibers.

One of the advantages of the hybrid former is that it can be made by relatively simple modification of the wire part of the existing fourdrinier wire former. Internet loop. In addition to improving the quality of the paper produced, the dewatering effect in the wire section can be enhanced, thereby increasing the production speed of the paper machine. In the applicant's Finnish patent application No. 820742 a hybrid former is described which is mainly used for the production of newsprint and printing papers of similar quality at a production speed of about 900 m/min or higher.

In general, the hybrid formers of the prior art are not suitable for the production of thick paper and board, because the beginning of the twin-wire section following the first single-wire dewatering zone, the wire and the wire placed between the two wires have been partially turned into a web The course of the fibrous layer is immediately directed relatively steeply and is bent over a long distance over turning rollers or over a stationary surface called a forming pad. The curved formation produces an internal shearing effect in the web which becomes more severe as the thickness of the paper increases. A relatively high dewatering pressure is thus exerted on the fibers between the two webs, which is proportional to the stretching of the outer web and inversely proportional to the radius of curvature of the relevant guide surface.

Due to space problems and other structural factors, in existing hybrid formers, as introduced in Finnish Patent No. 75375 (equivalent to U.S. Patent No. 4,614,566), the radius of curvature of the member changing the direction of the web is so small that if the For such formers to produce relatively thick paper and board, the relatively instantaneous compressive effect on the web being formed at this stage is too great. Excessive compression thus damages the fibrous layer, reducing the quality of the finished product, especially its strength and thus also the quality of the print. In the worst case, excessive compression can lead to so-called "cracking" of the web, causing interruptions in production.

Regarding the state of the art of the present invention, please further refer to U.S. Patent No. 4,769,111 of Messrs.A.Ahlstrom Company and the applicant's Finnish patent application and the Finnish patent application of Messrs.Valmet-Ahlstrom Inc. submitted together with the application.

The main purpose of the present invention is to provide a multi-functional former, which can be used to obtain a wide range of production speeds and products of a wide range of grammes. Therefore, the same former can be used to manufacture paper and paperboards with a grammage range of up to 30. g/ ^m2 to 500 g/ ^m2 , the production speed range can reach 100 m/min to 1200 m/min.

One of the starting points of the present invention is the applicant's "Sym-Former R" (TM) Sym type stacked double-wire former Finnish patent No. 75375), which has been found in use, and it has a lower grammage and high speed. The next works best. It is therefore an object of the present invention to further improve the applicant's "Sym-Former R" former so that it can be used in an extended range, including thick paper and cardboard, and at low speeds.

When trying to achieve higher grammage paper production with this "Sym-Former" former, it has been noted that the quality of the paper it produces, especially the formation evenness and smoothness of the paper, is affected. The object of the present invention is also to avoid this disadvantage and to be able to produce paper and board of good quality with good uniformity and symmetry of the formation of the paper at a wide range of production speeds and grammages.

It is another object of the present invention to provide a former, certain embodiments of which are particularly suitable for retrofitting the wire section of existing Fourdrinier formers.

A further object of the present invention is to provide a method and former in which microturbulences which improve the formation and smoothness of the paper can be introduced to the web at appropriate stages of dewatering.

It is an object of the present invention to provide a versatile former which avoids excessive dewatering pressure due to web stretching, at least in the initial part of web forming, and until the paper has had time to achieve the proper level (Couching) Later, this pressure is applied only in the final stages of paper formation.

A subsidiary object of the present invention is to provide such a versatile method and web former in which the twin wire dewatering zone is not below the level of the lower wire plane. This has advantages both in terms of paper forming and in the case of retrofitting the frame knots of existing Fourdrinier former wire sections can be utilized.

Another incidental object of the present invention is to provide such a method and multi-performance former, which can, if necessary, employ a second headbox by which pulp of a second quality or pulp of the same quality can be sent to on the fiber layer being formed.

For achieving the above-mentioned purpose and the purpose that occurs later, the main feature of the inventive method is:

After initial dewatering by means of the single wire dewatering zone of the lower wire, the mat being formed passes through a lower wire support system which constitutes a direct extension of said single wire dewatering zone. In the region of this support system, dewatering caused by the action of gravity through the lowering of the wire is largely prevented.

Choose the paper web forming method according to the grammage of the paper to be produced. When producing paper with a larger grammage, make the paper web pass through the single-wire dehydration zone and then reach the beginning of the double-wire dewatering zone. This initial part is determined by the support system and the suction and foil device placed inside the lower wire circuit. The water absorption and chopping board device is placed in the inner loop of the grid, and is opposite to the supporting system. Dehydration takes place mainly in this initial section by means of a net. In a second alternative web-forming mode, when producing thinner webs, said suction and chopping device is not in contact with the lower wire facing it;

After the above-mentioned web forming stage, there is a twin-wire dewatering section, which is guided by a forming roll or the like placed in the wire circuit and is bent upwards in a short sector. Thus, the twin wire forming zone guided by the forming plate or corresponding part is guided to bend downwards. The shaped plate has a larger radius of curvature. After passing through the twin-wire forming zone, the paper web moves with one of the wires, preferably with the lower wire.

On the other hand, the main characteristic of the device according to the invention is that its second dewatering zone with twin wires is flat and constitutes a direct linear extension of the single wire start at its relatively long start. The double-wire area is guided upward by a short segment of the forming roller placed in the feeding circuit and has a hollow lining. Afterwards, a forming plate is installed in the lower wire circuit. The guide surface of the forming plate guides the double wire zone to bend downwards. The guide surface of the profiled plate is preferably ribbed and has a large radius of curvature. At the beginning of the inner end of the network loop, there is a water absorption and chopping board device. When the forming unit is tuned to produce thinner papers (typically in the grammage range of 30 to 120 g/ ^m2 ), actuators can be used to switch the suction and chopping units from those used for thicker papers. The lower working position is raised to the upper position.

In the range of high operating speed and low grammage (usually below 120g/m ² ), the forming device according to the present invention can be used as a hybrid forming device of a Sym type forming device, and the water suction and the cutting board device of the feeding device are lifted to above position. Therefore, its operating speed is usually in the range of 800 to 1200m/min.

Under the situation of using the same paper machine, when needing to produce thicker paper or cardboard, such as 100-500g/m ² Even higher grammage scope, and when adopting lower running speed, according to the present invention The operation of the forming device can be adjusted, and the water suction and chopping board device of the net device can be rotated to the self-adjusting surface of a set of support beams located inside the net device. After passing through the initial part of the single net, the direction of dehydration can be reversed, and the water absorption and chopping board device can be used to carry out the dehydration through the net. And utilize a group of supporting beams that are positioned at the bottom of the lower wire and arranged opposite to the water suction and chopping board device, basically can prevent the dehydration by the lower wire. Then, after most of the water has been removed, the final dewatering is carried out using the suitably curved twin wire section of the "Sym former". This curved twin wire section is arranged so that the thicker partially couched paper is not subjected to excessively sharp or prolonged changes in direction or shear forces resulting from such changes.

In the present invention, after passing through the single net initial dehydration zone, its dehydration needs to be controlled so that its dehydration is mainly carried out through the feeding circuit. As such, it may utilize a dehydration device placed in the feeding circuit, for example as described in the applicant's Swedish patent application no. 8703468. The device comprises a suction or wiper blade combined with a corresponding water collection chamber. It is convenient for the water collection chamber to be connected to the suction source. In addition, this dehydration device includes at least one water collection chamber, which is composed of several chopping boards and communicates with the suction source. In addition, in the net circuit, facing the dehydration device in the net circuit, a series of net support beams are installed. The function of these support beams is to reduce or substantially prevent dewatering by the lower wire. On the one hand, a dewatering pressure intensified in an upward direction and appropriate pulsations of this pressure are applied in this region to the partially formed paper under the web. On the other hand, the forming of the paper being formed is also improved by utilizing the pressure and pulsation. Each beam of these net supporting beams is all such as utilizing the compressed air hose to load the lower net circuit. Therefore, the compression applied to the paper is self-regulating.

If necessary, one or several second headboxes may be used in the present invention. With these headboxes, the same quality or different qualities of pulp can be sent to the paper being formed before the twin wire forming area, so that the whole process of paper forming can be controlled and can be used to produce different stacks if necessary. Layer structures, e.g. for the production of cardboard.

Microturbulence is generated by means of a set of mesh support beams, ie mesh panels used according to the invention. These wire support beams are placed within the lower wire circuit and act as a direct linear extension of the single wire dewatering zone. Microturbulence improves web formation and smoothness. Furthermore, a self-adjusting gap zone is created at the beginning of the twin wire section. This self-adjusting gap area also brings advantages in terms of dewatering sensitivity and paper formation, so that the pressure caused by the stretching of the wire does not apply to the paper web, and the gap area between the wires can be determined according to the situation of the discharged water. Very free to adjust and shape.

Hereinafter, the present invention will be described in detail with reference to some embodiments of the invention shown in the accompanying drawings. The invention is in no way restricted to the details of these examples.

Figure 1 shows a first embodiment of the invention adapted to the operation of a "Sym-type former", with which paper or board of lower grammage can be produced at high speed.

Figure 2 shows the same former shown in Figure 1, adjusted to work in such a way that even high grammage paper or board can be produced at low speeds.

Figure 3 shows a second embodiment of the invention, adjusted to work in the production of higher grammage products.

Fig. 4 shows the working mode of the third embodiment of the present invention, wherein two chopping boards and or suction boxes are used in its surfing device.

Figure 5 shows a fourth embodiment of the invention, which employs a second headbox with which thicker boards can be produced.

Figure 6 is a vertical sectional view of a set of chopping boards and suction boxes and a wire support and blocking device placed in the lower wire circuit and facing the chopping boards and suction boxes according to the present invention.

The paper former shown in FIGS. 1-5 comprises a headbox 19 and a lower wire circuit 20 . The stroke of the lower wire circuit is basically guided by the breast roll 21, the guide roll 22, the forming plate 26, the couch roll 28 and the drive roll 29. In addition, inside the lower wire circuit 20, in the first dewatering zone 20a, there is a group of dewatering members 23. In the second dewatering zone there is a wire support device 30 and a suction box 27 . These suction boxes are placed on the run of the lower wire 20 between the forming plate 26 and the roll 25 ( FIG. 3 ) and the couch roll 28 .

The paper former shown in Figures 1 to 5 also includes an upper wire circuit 10 guided by guide rolls 11, 11a and 11b, which covers the lower wire circuit in the twin wire dewatering section. In addition, there is a dehydration device 40 inside the circuit 10, which is illustrated more specifically in FIG. 6 . As a first component, the device 40 includes a dewatering blade of the vacuum blade type, preferably associated with the suction chamber. The dehydration device 40 also includes two or three sumps, the bottom of which is formed by a chopping board (foil), which rests on the Internet 10 .

Next, differences between the various formers shown in Figs. 1 to 5 will be described.

Figures 1 and 2 illustrate two different modes of operation of the same former. In the mode of operation of the "Sym former" of Figure 1, thinner papers are produced at high speeds, typically around 30 to 120 g/ ^m2 . Figure 2 illustrates one mode of operation of the same former, usually producing thicker papers at lower speeds, about 120 to 500 g/ ^m² .

As shown in Figures 1 and 2, in the twin-wire forming zone, behind the forming roll 16 with a hollow lining 16', there is a forming plate 26 with a rib 26' having a larger Radius of curvature R, usually R = 5 to 9m. There are some vacuum suction boxes 27 behind the forming plate 26 . In FIG. 1 , the twin-wire zone starts at line A1 of the sector of roll 16 and ends at line B. In FIG. In Figure 2, the twin wire zone starts from line Ao towards guide roll 11a and ends at line B.

In FIG. 3 the forming plate 26 shown in FIGS. 1 and 2 is replaced by a shorter forming plate 26A followed by forming rolls 25 . The forming roll preferably has a smooth and hard lining. The radius of the forming roll 25 is substantially smaller than the radius of curvature RA of the ribs 26A' of the forming plate 26A. The radius of curvature is usually in the range of RA = 0.8 to 1.5 m, and the structure is otherwise similar to that shown in Figures 1 and 2 above.

The structure shown in Fig. 4 is similar to that shown in Figs. The device 40A is similar in structure and operation to the dewatering device 40 described above except that the contour of the chopping board system defining its underside has a curved shape corresponding to the ribs 26' of the forming plate 26. The forming plate 26 is followed by a vacuum suction box 27a placed on the inner side of the lower wire circuit 20 . There is a second forming roll 16a behind the above-mentioned vacuum suction box 27a, which is placed inside the upper circuit 10, and preferably has a smooth and hard lining.

The structure shown in Figure 5 is similar to that shown in Figures 1 and 2, the difference being that a second headbox 60 is used in Figure 5 . Via its knife cone 61, the second pulp jet J1 is directed onto the fiber layer formed on the wire section 20a of the single-wire Fourdrinier former before being sent to the twin-wire forming zone. The pulp quality of the main jet J and the second jet J1 can be the same or different from each other. For example, in the latter case, cardboard for the production of laminated structures.

For the production of thick paper (120 g/m ² to 500 g/m ² ), the operation of the web former shown in Figures 2 to 5 is as follows. The head box 19 sends the pulp jet J to the horizontal starting part 20a of the lower wire circuit 20, that is, to the first dehydration zone, in which the dehydration work is only carried out slowly downward through the lower wire 20, Dewatering is also suitably enhanced by means of suitable dewatering means 23, such as foil boxes. The fiber layer formed on the surface of the lower wire loop 20 continues its journey to the second dehydration zone, which is formed when the upper loop 10 is guided to the vicinity of the lower wire loop 20 at a small angle d (Figure 6). . The most suitable angle d is 2 to 5°, and can be adjusted by adjusting the vertical position of the calibrating roller 11a of the upper circuit 10 through the device 18 (FIG. 1).

In Figures 2 to 5, the second double-wire dehydration zone is divided into several sections. The dewatering device 40 placed inside the upper circuit 10 and the wire support device 30 placed inside the lower wire circuit 20 and working in conjunction with the dewatering device 40 form the first section of the second dehydration zone. Both the first dewatering zone 20 a and the longer first section of the second dewatering zone are at the same level before reaching the forming roll 16 . The forming rolls 16 rotate so that the travel of the wires 10 and 20 forms a slight upward angle. This angle is equal to the size of sector shape a. On this segment a, the combined run of the wires 10 and 20 is in contact with the forming roll 16 . This sector a forms the second section of the twin-wire dewatering zone. The pressure (P=T/R) between the wires 10 and 20 removes more water from the formed web W. These waters are thrown into the sump 13 by centrifugal force.

The upper wire 10 is detached from the web W placed on the surface of the lower wire 20 by means of the guide roll 11b, said web continuing to move to the roll 14. The suction box 27 ensures that the web W does not follow the wire 10 and the wire 10 returns to the roll 11a. Adjacent to the couch roll 28, a tail roll 14 provided with a suction zone 14a is placed together with a separating felt 15 by means of which the web W is transported from the wire section to the press section (not shown).

The former shown in FIG. 1 is adjusted to the mode of operation for the production of thinner papers with a typical grammage of about 30 to 120 g/m. In this case, the dewatering device 30 acts as a direct linear extension of the initial part 20a of the single wire and takes place through the lower wire 20 using the microturbulence generated by the groove 35 between the dewatering device and its support beam (Fig. 6). The dehydration work, and play a shaping role in the paper.

The starting part 20a of the substantially horizontal single-wire dewatering zone belongs to the lower wire device shown in FIG. move. For example, the lower wire section is the wire section of an existing fourdrinier wire former with frame structure 100 . It already exists, and the specific Internet access device 70 of the present invention is combined on it to form a new device.

For example, there are dewatering devices from the existing Fourdrinier former wire section, such as chopping boards and/or suction boxes, at the single wire start section 20 and a suction box 27 at the end of the twin wire section.

The Internet access device 70 includes a frame having horizontal and vertical beams 71, 72 to which various parts are fixed. The stroke of the wire circuit 10 is guided from the starting point A1 of the twin wire section by means of the opening roll 16 with the hollow facing 16' and the subsequent forming plate 26. The forming plate 26 has a rib 26' having a radius R of curvature. The twin-wire dewatering zone ends in the area of the last suction box 27 .

According to FIG. 1 , the Internet access device 70 includes a frame 75 . This frame 75 is pivoted in a vertical plane and is mounted to the horizontal beam 71 by adjusting screws 17a and 17b or the like. The first guide roller 11 a of the web 10 is mounted on the frame 75 . In Fig. 1, the display frame 75 and the dewatering device 40' installed on its support and the first guide roller 11a are all in the position of turning upwards. When the paper quality to be produced is changed, it can return to Fig. 2 from this position. In the position shown, in the latter position, the means 30 and 40 work together opposite each other.

In the initial part 20a of the single-wire dewatering zone, utilize the dewatering member 23 between the discharge port of the head box 19 and devices 30 such as forming plates and chopping boards to carry out dewatering, and in the single-wire initial part 20a, by The lower net 20 is dehydrated to a certain extent, and the remaining part of a sufficient proportion is dehydrated upward. After passing the line A1, the combined course of the webs 10 and 20 is bent upwards at the angle of the short sector a, this angle a=10° to 35°, preferably a=15° to 25°.

Microturbulence is created by slots 35 (Fig. 6) in one set of beams in wire support 30 so that web W formation can be completed and improved before the twin wire zone begins.

After sector a, there is a very short straight line of the wires 10 and 20, in the area of the forming plate 26, dewatering through the upper wires 10 in the direction of the compression between the wires 10 and 20 and the use of centrifugal force. After the trailing edge of the forming plate 26 there is a straight joint run of the wires 10 and 20 .

In the mode of operation of Fig. 1, the former of the present invention produces thinner paper in the manner of the hybrid twin-wire former as described above. For its specific structure and operation, please refer to the applicant's above-mentioned Finnish Patent No. 75375.

Figure 6 shows the dewatering device 40 belonging to the wire section of Figures 1 to 5 and its most important structural details, as well as the lower wire support system working in conjunction with the dewatering device 40 described above.

The dehydration unit 40 is a combination, usually including 2 to 4 (3 in the figure) suction and water collection chambers 46,47,48. The chambers are separated from each other by partitions 47b and 48b. Each chamber 46, 47 and 48 is provided with an air port (not shown) connected to a suction source and a drain 49. A water collecting pipe 46a belonging to the first water suction chamber 46 is formed between the frame beam 46b of the dehydration device 40 and the guide plate 46c. At the lower end of the tube 46a there is a transverse chopping blade 51 and a wedge 52 which can be adjusted by means of an adjustment shaft 53 . The scraper and wedge form a locally adjustable gap E. The gap E spans the width of the former through which water extruded from the fibrous layer between the wires 10 and 20 flows into the first chamber 46 .

After the chopping blade 51 of device 40 shown in Figure 6, there are some similar chopping blades 51 ' and 51 ", and their bottom surfaces are all on the same level. The chopping blade 51 ' gathers the fibers separated from the fiber structure under the first suction chamber 46. Water. These waters are guided into the water suction chamber 47 through the pipe 47a, which is formed between the partition plate 47b and the guide plate 47c. Likewise, the water gathered by the scraper 51 "of the next step is guided to the third water suction chamber through the pipe 48a. Chamber 48, while duct 48a is formed between rear wall 48d of the dehydrator and guide plate 48c.

The tube 46a shown in FIG. 6 and the associated chopping blade 51 and adjustment wedge 52 form a suction-assisted dewatering member. When using this former to produce thicker paper and cardboard at low speed, it is best to use vacuum suction to help the automatic doctor system work. The most appropriate vacuum is 6-8kpa (kilo Pascal). The amount of dehydration carried out upwards at this stage (partially also the magnitude of vacuum generation) can be changed by adjusting the height of the gap E between the wedge block 52 and the chopping blade 51 .

In FIG. 6 , the dehydration effect of the suction-assisted dewatering element and the associated first water-absorbing chamber 46 is localized and limited near the tip of the first chopping blade 51 . The dehydration area of the second water absorption chamber 47 is relatively wide, which is determined by the number of chopping board scrapers 51 ′, which are shown as seven in FIG. 6 , which is a specific example. The effect of the chopping blade 51 ′ is based on its joint operation with the wire support device 30 placed inside the lower wire circuit 20 . The main feature of the support device 30 and its operation is that, with it, the compression exerted by the lower wire 20 on the forming web can be continuously increased in the desired manner in the region of the dewatering device 40 . Utilizing this compression action, the dehydration of the paper web W is mainly carried out through the feeding circuit 10, water enters the suction pipe 47a, and enters the water absorption chamber 47 through the suction pipe 47a. The operation of the third water absorption chamber 48 is similar to that of the second water absorption chamber 47 .

The negative pressures that the second and third chambers 47 and 48 shown in Figure 6 present are preferably much higher than the first chamber, that is, chamber 47 is about 10 to 20kpa, chamber 48 is about 15 to 30kpa, and its specific values depend on The material of the paper being produced.

The water collecting device 40A shown in FIG. 4 includes two water suction chambers placed one behind the other. Two wedges placed under the two suction chambers are in contact with the net 10 . These two wedges delimit the drinking tube of the device 40A with their rear sides of the mouth in the direction of movement of the net 10 .

With reference to Figure 4, the main feature of the invention should be further clarified that in some embodiments of the invention, particularly those most suitable for retrofitting the wire section of a fourdrinier former, the forming zone need not extend to Below the T-T plane defined by the single net start portion 20a. According to FIG. 4, after the forming roll 16a, the double wire zone with the suction box 27 in the lower wire circuit 20 returns to the level T-T defined by the single wire start 20a. The single web initiation portion 20a is preferably horizontal.

With respect to the apparatus shown in Fig. 6, when the former of Fig. 2 to Fig. 5 is used to produce thick paper, the dehydration process is as follows. In the first dewatering zone 20a of the former, the partially formed fiber layer on the surface of the lower wire circuit 20 enters the space between the wires 10 and 20, whose clearance angle d is determined by the position of the guide roll 11a. The wire 10 is guided by guide rollers 11 a whose position can be adjusted by means of a device 18 . The surface of the web contacts the top 10 in front of the wedges 52 . In this position, the part of the wire support device 30 supporting the lower wire circuit 20 also starts, with the action of which the dewatering of the fibrous layer starts and mainly takes place upwards.

The beam member 31 of the device 30 shown in FIG. 6 is supported on a longitudinal support beam 33 by the middle portion of a rubber tube 32 filled with compressed air. The support beams 33 are in turn supported by transverse box beams 34 . The pressure action of the rubber tube 32 can be adjusted, so that the load acting on the lower net 20 and the fiber net member can increase sequentially in the direction of movement of the nets 10 and 20. In the rubber tube 32, a relatively paper pressure, such as 10 to 50 _cmH2O (centimeters of water column), is used to apply a very moderate compression to the web W in the forming stage. The dehydration pressure is self-regulating. The member surfaces of the device 30 are provided with transverse grooves 35 across the entire width of the mesh 20 . These troughs also have some dehydration effects by lower net 20. Microturbulence is generated by these grooves to improve the forming of the web W.

In FIG. 6, the dewatering process continues in the area between the contact line of the upper surface of the web W and the wedges 52. As shown in FIG. Among them, a water layer is formed on the inner surface of the net 10 . This water layer is collected in the wedge-shaped space between the net 10 and the wedge 52 and subsequently in the gap E between the wedge 52 and the chopping board. Through this gap, water is forced through the pipe 46a into the first chamber 46 of the dehydration device by means of its kinetic energy and/or the vacuum of the vacuum chamber. The wedge block 52 can be adjusted vertically by means of an adjustment device 53, so that the amount of water entering the conduit 46a can be adjusted, and the amount of air can also be adjusted at the same time. Naturally, the adjustment of the angle of inclination d between the wires 10 and 20, the adjustment of the gap of the entry tube 46a, and the adjustment of the pressure exerted by the support system all depend on the paper or board being produced.

In some cases, the suction-assisted system based on the adjustment wedge 52 shown in FIG. 6 can be replaced by another structure. In this structure, the adjustment wedge 52 is replaced by a roller whose rotational speed and its height position, ie its distance from the wire 10, are adjustable.

In the following the claims of the invention are given, by means of which the various details of the invention can be varied within the scope of the inventive idea specified by these claims and differ from the embodiments described above which are presented by way of example only. .

Claims (12)

1. A method for forming a paper or cardboard web (W) using fibrous materials as a raw material, which method is used on a wire section of a paper machine or similar equipment, and the wire section is composed of a lower wire circuit (20) and an upper wire circuit (10), The lower wire circuit is substantially horizontal at least at the beginning of its upstroke, the upper wire circuit works in conjunction with the lower wire circuit, and in this method the fiber suspension jet from the paper machine headbox (19) (J) to the initial part (20a) of the upstroke of the lower wire circuit (20), which constitutes the first single-wire dewatering zone, and then sends the partially dewatered fiber layer to the second dewatering zone , in this second dehydration zone, make the upper circuit (10) cover the fiber layer through partial dehydration, make the fiber layer continue dehydration in the second dehydration section, then make the upper circuit (10) and the formed fiber Paper web (W) breaks away, and fiber paper continues to move along with the stroke of net circuit (20) to carry out post-processing to paper web (W), and the method of the present invention is characterized in that: After the initial dewatering of the single wire dewatering zone (20a) by the lower wire (20), the formed fiber layer (W) is passed through the support system (30) of the lower wire (20), which constitutes the single wire zone The direct extension of (20a), in the section of this support system (30), can largely prevent dehydration caused by gravity through the lower wire (20), According to the grammage of the paper produced, the paper web forming method is selected. When producing paper with a higher grammage, after passing through the single-wire dehydration zone (20a), the paper web (W) is sent to the starting point of the double-wire dehydration zone. This initial part is made up of the above-mentioned supporting system (30) placed on the inner side of the lower net circuit (20) and the water absorption and chopping board device (40) opposite to the supporting system (30) placed on the inner side of the upper net circuit (10) Determined, the dehydration is carried out mainly through the Internet (10) in the initial part, and in the second alternative paper forming mode, when producing thinner paper, the water absorption and chopping board device (40) out of contact with the lower net (20) facing it, and, After the above-mentioned web forming stage, there follows a twin-wire dewatering section, which is guided by a forming roll (16) or a corresponding part placed in the upper circuit (10), and in a shorter sector Bending upward within the scope of section (a), and then the forming plate (26) or corresponding parts guide the double wire forming area to make it bend downward. The forming plate (26) has a larger radius of curvature (R). After the wire forming zone, the web (W) is guided to follow one of the wires, preferably with the lower wire (20). 2. The method according to claim 1, characterized in that the section after the initial dewatering zone (20a) of the single wire in the stroke of the lower wire is flat at its longer initial part and constitutes the lower part of the former The immediate linear extension of the initial wire travel (20a) where microturbulence is created in the web (W) by means of grooves (35) or corresponding structures provided by the wire support members (31). 3. The method according to claim 1 or 2, characterized in that: when the former is adjusted to produce paper with a lower grammage, usually 30 to 120 g/ ^m2 , it will be placed in the feeding circuit (10) The inner suction and dewatering box (40) group is lifted to an upper position (40') at least together with the frontmost guide roll (11a) of the wire (10), so that the twin-wire paper web forming area is placed on the wire loop (10) Starting from a short fan-shaped part (a) of the forming roller (16) with a hollow lining (16)', when producing thicker paper that is usually 120 to 500g/ ^m2 , the parts of the surfing device (75 ) is turned to the lower position, so that the net support device (30) located in the lower net circuit (20) and the water absorption and cutting board device (40) placed in the upper net circuit and turned down are used as the initial part of the double net dehydration zone Carry out dehydration, here mainly by surfing the net and by means of said water suction and chopping board device (40). 4. The method according to any one of claims 1 to 3, characterized in that the double wire area bends upwards a short segment (a) on the forming roll (16) located in the upper loop, the segment The angle is selected in the range of a=10° to 45°, the most suitable angle range is a=15° to 25°, and the double wire area is bent downwards on a curved stationary forming plate member (26), The radius of curvature (R) of the member (26) is much larger than the radius of the forming roller (16). 5. A method as claimed in any one of claims 1 to 4, characterized in that, after passing through the section (a) of the forming roll (16) which is located in the upper circuit and has a hollow lining (16'), The twin wire section is curved downward on a shorter forming plate (26A) with a larger radius of curvature (RA) followed by a steeper downwardly curved zone which is Guided by the second forming rolls (25) located in the lower wire circuit (20), the twin wire zone then passes through one or several vacuum suction boxes (27) or equivalent devices located in the lower wire circuit (20). 6. The method according to any one of claims 1 to 5, characterized in that, in the method, after passing through the upward bending zone occurring on the forming roll (16) of the twin wire forming zone, after passing through the web (10) Dewatering is carried out using a water collector (40A) mounted against the forming plate (26) 7. A method as claimed in any one of claims 1 to 6, characterized in that, when producing thicker paper, the first wire from the second headbox (60) is fed before the start of the twin wire forming zone. The second pulp (J1) is sent to the above-mentioned single wire dehydration zone (20a). 8. A web forming apparatus for carrying out the method as claimed in any one of claims 1 to 7, comprising a lower wire circuit (20), an upper feeding device (70) and a lower wire headbox, the lower wire circuit (20) having Basically horizontal upward stroke; the netting device (70) works jointly with the netting circuit (20), and is equipped with the netting circuit (10), and the net head box (19) is installed to spray the fiber suspension (J) It is sent to the single-wire initial part (20a) of the upper stroke of the lower wire circuit, and thereafter, there is a double wire forming area, which is formed between the joint stroke of the lower wire (20) and the upper wire (10). In the wire forming area, there are various components and component groups placed in the lower wire circuit (20) and the upper wire circuit (10) to dewater, and the present invention is characterized in that: in its basic and longer initial part, The second twin-wire dewatering zone is flat and constitutes a direct linear extension of the single-wire initial section (20a), while the twin-wire zone, guided by a short sector (a) of the forming rolls (16), is directed upwards Bending, the forming roller (16) is fixed in the upper circuit and has a hollow lining (16'), behind, the forming plate (26) is installed in the lower circuit (20), and the guiding surface of the forming pad (26) guides the double wire The guide area is guided and bent downwards. The guide surface preferably has a rib plate (26') and has a large radius of curvature (R). A water absorption and chopping board device ( 40), when the forming device is adjusted to produce thinner paper with a grammage of typically 30 to 120 g/ ^m2 , the actuators (17a, 17b) can be used to make Paper lower working position raised to upper position (40′). 9. Apparatus according to claim 8, characterized in that, on the straight initial section of the twin-wire dewatering zone, a forming plate (30) is installed, which includes self-adjusting support beams (31) for the lower wires, The forming plate (30) is placed in the lower wire circuit (20) and is equipped with parts that use them as a device to prevent dehydration, and a water absorption and chopping board device (40) is arranged in the upper circuit facing the forming plate (30) . 10. Device according to claim 8 or 9, characterized in that the forming plates placed in the lower wire circuit (20) consist of self-adjusting beams (31) made of pressurized hoses (32) Or the corresponding parts are supported and stretched over the area facing two or three water suction chambers and their chopping board devices (51, 51', 51 "), the chopping board device guides the dehydration device's online (10), and is opposite to the beam (31) place. 11. The device according to any one of claims 8 to 10, characterized in that the water absorption and chopping board device (40) placed in the feeding circuit (10) consists of at least two, preferably three The box group of each box and the subsequent water suction chambers (46, 47, 48) and the chopping board device (51, 51′51″) placed at the bottom of the box group, the device (40) is used to guide the double wire dehydration area and as a direct linear extension of the initial portion (20a) of the single net. 12. The device according to any one of claims 8 to 11, characterized in that, before the water suction and chopping board device (40), there is a suction-assisted device whose upwardly inclined pipe (46a) is connected to the first water suction Chamber (46) communicates, and the mouth of this pipe (46a) has a forming block (52) that is adjustable relative to the upper net (10).

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