FI84636B - Hybrid former in a paper machine - Google Patents

Description

84636

The invention relates to a hybridformer for a paper machine, comprising a first wire fan cooperating with the headbox of the paper machine, the initial part of which forms a single-wire first dewatering zone, in the area of which the downwardly through the wire, the former comprising a second wire loop arranged on the first wire loop so that the wires together form a two-wire second dewatering zone immediately following the first dewatering zone and the former forming a two-wire second dewatering zone at the beginning of the first wire zone and the first wire loop at least a partially curved surface dewatering member having a center of curvature on the side of the first wire loop and guiding a common passage of the first and second wire loops at the beginning of the second two-wire dewatering zone, and in the region of the two-wire second dewatering zone, inside the second wire loop there is at least one device for preventing and preferably adjusting overflow through the second wire loop working width.

It is known that in the flat wire section of a conventional Fourdrinier paper machine, dewatering of the pulp suspension and the web gradually formed takes place exclusively downwards, partly by gravity, partly by either suction from stationary dewatering means, e.g. foils, or rotating register rollers. mainly on the wire side. It is therefore made on the Fourdrinier machine, the paper web is always anisotropic in respect of its two sides characteristics so that the upper surface of the web is smoother than the lower face, with the addition of so-called visible. viiramarkkeeraus. For the reason set out above, the top surface layer of the web also contains more fines and fillers than the bottom surface layer facing the wire.

In order to avoid these disadvantages, a so-called twin wire formers in which a substantial portion of the web is formed between the two wires 2 84636 so that the dewatering is effected either simultaneously or alternately in two directions, thereby at least partially eliminating the bias of the resulting web. Paper made on such machines is therefore considered to have better printing properties, especially paper made on single-wire Fourdrinier machines.

Two-wire formers can be of two main types, one of which is the so-called a guitar former and another so-called hybrid former. It should be noted that in mechanical engineering, a hybrid means a combination of two different types of machines or devices serving the same purpose, so that the advantageous properties of each are exploited. Em. the differences between the main types are explained in more detail below.

The kit former is completely double-wire, meaning that the fiber suspension is fed directly from the headbox into a converging wedge space between the two wire loops, where dewatering of the suspension can begin immediately in two directions, unless there is an obstacle for one reason or another. An obstacle to bidirectional dewatering may be a substantially closed surface within the second wire loop and in the region of the wedge space, which guides the passage of the wire.

The wire loops are substantially the same length in most guitar formers, which, however, is not necessary. Due to the operating principle of the other formers, they can have any directional angle of the dewatering zone, either vertically or horizontally, or in between. The fiber suspension can be fed to the kit either from the bottom up or vice versa. The dewatering zone, i.e. the web forming zone, in turn can be either substantially straight or curved. Once the fibrous web to be formed has sufficient strength in the dewatering zone, the runs 30 of the wire loops diverge and the web moves forward in support of the second wire, after which it can be detached from the wire by conventional means and transferred to the press section of the paper machine.

The hybrid former is a combination in function and structure of a Fourdri-35 Nier wire section and an actual double wire former. The hybrid former is characterized in that the dilute fiber suspension is first fed from the headbox to a single, substantially horizontal and straight primary wire, e.g. supported by register rolls or the like. This works the so-called. as a sub-wire where the dewatering takes place only in one direction, i.e. downwards. In the hybrid former, it is only after this dewatering section that the secondary wire loop is passed above the connection with the primary wire to form a two-wire dewatering zone, the beginning of which forms a more or less wedge-shaped area between the wires in the same way as in the groove former.

It follows from the principle of operation of the hybrid former that its single-wire initial portion 10 is substantially horizontal or slightly inclined either upwards or downwards.

The main difference in the operation of a hybrid former and a conventional other former is that in hybrid formers a certain portion of the suspension fibers during pre-dewatering before said two-wire zone forms a thinner but relatively coherent fibrous layer on the lower wire surface as shown schematically in Figure 1. comparing fibers that move freely with respect to each other. However, the consistency of this suspension 20 as it enters the double-wire zone of the hybrid former is generally significantly greater than the original headbox consistency provided by the dewatering. Immediately before the start of dewatering, the consistency of the conventional kit-type double-wire former is exactly the same as in the headbox, and therefore the web-forming process in the kit 25 is quite different in nature and result than in the hybrid former.

The two-wire dewatering zone of both the kit former and the hybrid former may be provided with either rotating or stationary dewatering members or combinations thereof. The advantage of rotating dewatering members is that they consume substantially less wire than fixed ones. The advantage of the latter is again that they can be used to advantageously influence the so-called formation, i.e. the uniformity of the fiber distribution of the paper, which cannot be sufficiently achieved by rotating dewatering means. This has been found in studies and test runs.

4,84636

As stationary dewatering elements, various types of so-called forming shoes, which usually have a box-like body and a cover part resting on it, which in conventional hybrid formers faces the lower wire. The cover part can be a continuous and solid plate, in which case the dewatering of the fibrous layer adjacent to it can take place only in one direction. Most commonly, however, the cover part is assembled from a plurality of strips transverse to the direction of travel of the wire, between which gaps of the desired size are left. The total surface of the slots is, for example, about 20-60% of the total area of the cover. From the 10 adjacent fibrous layers of crevice between the wires, water can escape in two directions. The slits are usually at an angle of 90 ° to the direction of travel of the wire. Even a smaller angle is possible. The openness of the surface of the slit lid can be adjusted by using filler strips placed in the slits. This can even happen during the operation of the paper machine if the structure of the slots and filling strips is appropriate. In this connection, reference is made to the applicant's FI patent application 771364.

The frame box of the forming shoe may be closed and as such connected to either a vacuum or overpressure generating device. With such a shoe member, it is possible to influence the direction of dewatering.

In addition to the dewatering effect, said cover strips cause a pulsation in the nascent web which flanks them between the two wires. This is one of the prerequisites for good formulation, which has been found in practice. The fibers of the web 25 partially formed by the pulsation move more or less relative to each other so that, for example, the fiber agglomerates in the web, i.e. the flocs, disintegrate.

In such forming shoe members, the guide or sliding surface facing the wire is most preferably curved. The radius of curvature may be constant or it may decrease in the direction of travel of the wire. The curved forming shoe also acts as a control element for the joint running of the wires, which contributes to the stability of the wires. With hybrid formers, a considerable part, up to 40-50%, of the dewatering takes place in the second or two-wire dewatering zone, especially in the area of its forming shoe.

35 Thus, the forming shoe arrangement has significant potential effects on both the dewatering capacity and the formation of the web to be formed.

5,84636

Although, for example, U.S. Pat. Nos. 2,881,669, 3,072,042 and 3,262,841 have already proposed certain types of wire parts to be considered as hybrid formers, they do not meet the current requirements or have not otherwise proved feasible. In particular, said wire sections 5 are not suitable for replicas of old Fourdrinier wire sections, which are now very important applications for hybrid formers. In these cases, after the rest of the flat wire section, in cooperation with it, one upper wire unit is usually placed, in the area of which the dewatering can also be turned upwards. This aims both to increase the dewatering capacity and to improve the retention. It should be noted that the new wire sections can be designed to be of the hybrid type from the outset.

Increasing the dewatering capacity makes it possible to e.g. the following 15 improvements or changes in the papermaking process: - it is possible to increase the working speed and production of the paper machine provided that other equipment on the machine allows it; 20 - without reducing the speed of the paper machine, the wire section can be used to produce thicker types of paper and board than before; - it is possible to reduce the consistency of the fiber suspension fed to the wire section, which in most cases leads to an improvement in the formation of the web formed; 25

In some cases, the upstream wire units described above have modernized old slow newsprint machines into paperboard machines without increasing the speed of the machine.

For the closest prior art to the present invention, reference is made to Applicant's U.S. Patents Nos. 3,846,233 and 4,164,566, which incorporate the applicant's Sym-Concept (TM) principle, although the scope of these patents is partially different. An essential feature in the operation of both structures 35 is the change in the direction of travel of the lower wire and the upper wire, respectively, immediately at the beginning of the double wire section, i.e. the second dewatering zone, which is achieved by means of either a curved shoe member or a roll.

6 84636

Although the main factor influencing dewatering is the compression between the wires with their curved portion, the centrifugal force acting at the same time is also relevant. In principle, the compression between the wires causes water to flow out equally through each of the 5 wires if their density (mesh) is the same. During pre-dewatering, some degree of nonwoven has formed on the surface of the sub-wire, the thickness of which depends on several variables such as machine speed, pulp consistency as it discharges from the headbox to the wire, number and type of the shoe is not, for example, connected to a suction device. This naturally results in increased dewatering in the direction of the centrifugal force, i.e. through the covering upper wire.

15 This phenomenon has become more pronounced in recent years as the speeds of Sym-Former (TM) -type paper machines have grown significantly higher than they were 15 years ago. It has been found that enhanced dewatering impairs the ability of the fibrous layer to retain fines important to the finished web in its structure. In several known constructions according to e.g. U.S. Patent 4,532,008 and PCT / EP82 / 00036, attention has been paid to the fact that the fiber content of the water leaving through the upper wire, i.e. 0 water (white water), is considerably high compared to other parts of the wire section, e.g. water consistency. The present invention therefore relates to a dewatering arrangement applicable to the double wire portion of various types of hybrid formers.

Dewatering through the upper wire has been known to be reduced by selecting the fabric of the upper wire to be considerably denser than the fabric of the lower wire. However, this can result in relatively rapid clogging of the wire mesh, leading to premature wire replacement and production downtime. When using a dense top wire, it must also be taken into account that when after the second, i.e. two-wire dewatering zone, the top wire turns upwards and the formed fibrous web pi-35 should continue to travel only supported or supported by the . This naturally interferes with the operation of the wire section of the paper machine.

In order to avoid the above-mentioned disadvantages, the dewatering through the upper wire 5 should therefore be pursued by the invention with separate mechanical devices which not only prevent excessive dewatering but also regulate it optimally for the respective web-forming process. One suitable method for controlling dewatering in the area of a curved shoe is either an apparatus formed by deflector strips or a uniform cover structure, which will be described in more detail below.

The use of deflectors on the wire section of a paper machine, either under a single wire flat wire or on both sides of a double wire section, is already known, however, for the purpose of enhancing and directing or directing dewatering. In this connection, reference is made, for example, to U.S. Pat. No. 3,573,161, 2,881,676, 3,578,561, 3,915,791, 4,125,428, 3,597,315, in which deflectors are arranged in an oblique position relative to the direction of travel of the wire or wires so that they promote the removal of water from the web. Deflectors are also intended in some cases to cause those pulsations in the web adjoining the wire which, as mentioned above, generally have a favorable effect on the formation of the web to be formed.

It is a general object of the present invention to obviate the above drawbacks and to provide a dewatering member and arrangement for use with a two-wire portion of a hybrid former that allows the paper machine wire section to be adjusted to operate optimally at different speeds and grades of paper machine and dewatering capacity. taking into account retention. In many cases, the prior art has paid too much attention to formation at the expense of retention.

It is a particular object of the invention to provide such a dewatering arrangement for use in hybrid formers to control the dewatering event so that it can affect the filler and fines distribution of the web in general and the retention of the web in particular.

It is a further object of the invention to contribute to providing the best possible formation for the paper to be produced.

In order to achieve the above and later objects, the invention is mainly characterized in that the dewatering device is placed at a substantially curved surface dewatering member at a certain distance from the inner surface of the second wire loop.

The arrangement of deflectors according to the present invention differs from the known ones in that the invention aims to prevent or slow down the dewatering of the web by means of deflectors. To this end, the deflector strips inside the upper wire loop are arranged in the direction of the wires so that each strip forms a convex the pressure forces the water accumulating in the area of this gill to exit through the wire in the opposite direction to the deflector. 20 This position of the deflectors relative to the wire and thus their operation has the opposite effect to those already known.

It is further possible that said deflectors inside the upper wire loop are replaced by a uniform cover which, in its simplest form, is a relatively thick but flexible plastic or rubber mat and which covers all or only the desired portion of the forming shoe and thus slows down dewatering through the upper wire.

Such a cover may in many cases make it unnecessary to connect the forming shoe 30 to a suction system that consumes energy and requires certain suction duct arrangements. It is also possible that this cover is rigid, e.g. a steel plate, the curvature of which substantially corresponds to the curvature of the curved shoe inside the lower wire loop or of the roll used instead. The surface 35 facing the wire of the cover or cover plate can be provided with strips or projections corresponding to the deflectors. In particular, if the cover plate is a steel plate, either pressed or welded in a sig-sag cross-section, such plate ko can be provided with grooves or troughs in which it is possible to place strips suitable for the operation of the cover plate, e.g. deflectors, which are described in more detail below.

9 84636 5 The curvature of the rigid and fixed cover plate structure naturally corresponds suitably to the profile and / or curvature of the dewatering element inside the lower wire loop. The term "appropriate" must be understood broadly in this context. This means that the distance of the cover plate from said curved dewatering member and thus also from the upper wire tightly adjacent to the drainage member inside the lower wire 10 may be smaller at the rest of the cover plate than at its beginning. This can be achieved mainly by the center of the radius of curvature of the cover plate deviating from the corresponding center of curvature of the dewatering member inside the lower wire. It is, of course, possible that both the radius of curvature and the center of curvature of the cover plate-15 structure according to the invention differ from the respective values of the dewatering element in question. In most cases, it is most advantageous for the distance of the cover plate from the upper wire to be greatest in the zone in question at its initial part, where the drainage is also strongest. In practice, this is achieved by providing the rigid cover plate structure with adjustable support members, by means of which the distance of the cover from the wire can be adjusted either throughout or for one of the lunar ends of the cover plate. By using a relatively heavy and flexible rubber or plastic mat, automatic adjustment of the distance of the cover member from the upper wire can be achieved.

25 It is clear from the preamble to the description of this application that, in order to obtain the best results with regard to the pulsation applied to the web, the deflector element or the like must be located on both sides of the upper and lower wire paths adjacent to the partially or completely curved shoe.

This can be either connected to the lymphatic system or function without it, as mentioned below. The smooth cover member is often unable, despite the effect of hydraulic pulses coming exclusively from the downstream direction, to produce a total pulsation which would sufficiently affect the rather watery or at least wet web between the upper and lower wires. Therefore, it is most advantageous to provide the cover plate structure according to the invention with the most suitable discontinuity points, thanks to which an effect is obtained in the 1 semi-formed groove between the upper wire and the lower wire which, when controlled, results in a good final format.

10 84636 Such discontinuities may be grooves in the cover plate and grooves transverse to the direction of travel of the wires extending over the entire width of the machine, i.e. the gutters either as such or in part and most preferably so that some of them are provided with suitable filling strips, preferably extending over the cover plate. outside the concave line of curvature, i.e. the contour. Such projections 10, in particular if they correspond in size, direction and number to the deflector strips arranged inside the upper wire according to the basic solution of the invention, function completely like the deflectors in question.

It is preferred that these gutters have openings in all or only some of them at the bottom, which may be separate, e.g. round or elongated holes, preferably spaced evenly along the length of the bottom of the gutter. These openings can also be continuous slots extending over the entire width of the machine. These openings allow drainage through the cover plate 20 unless they are closed. The closing of the openings takes place, for example, by placing the above-mentioned filling strips in the grooves, which is a preferred solution according to the basic idea of the invention. Since in some circumstances it is necessary to allow dewatering to take place in a controlled manner through the cover plate, this is made possible by removing the filled 25 from one or more grooves, whereby said openings are released.

It is essential in the groove or trough arrangement of the cover plate described above that the filling strips used in them, the number and shape of which are chosen to be suitable, have the function of conventional deflectors as a factor influencing the format. At the same time, however, the dewatering can be influenced so that the retention of the fines in the fibrous layer between the wires remains as high as possible.

When using this rigid and trough cover plate for the purpose of the basic idea of kek-35, it is in some cases advantageous to design this cover plate so that it simultaneously acts as a water collecting trough for the water passing through the slots or openings in the trough bottoms.

The advantages of the invention are summarized below.

5

Thanks to the dewatering member and arrangement according to the invention, a better retention and formation is obtained in the web to be produced than by using a conventional forming shoe arrangement arranged only inside the lower wire. Control of the amount and proportions of dewatering through the upper 10 wires is achieved by using a dewatering member that at least partially covers the curved forming shoe inside the upper wire loop.

If the "anti-deflector strips" according to the invention are used, the desired result can be obtained in particular by adjusting their number and direction. This makes it possible that in the hybrid former in which the invention is applied, the dewatering in the first, i.e. monolayer, dewatering zone can be adjusted even more carefully so that the fines retention is kept as high as possible with a sufficient dewatering fraction remaining in the two-wire, second dewatering night. the final formation of the web is obtained.

In the following, the invention and its advantageous variation 25 will be described with reference to the embodiments shown in the figures of the accompanying drawing, to which, however, the invention is not limited.

Figure 1 schematically shows a background of a step 30 in a filtration event of a fiber suspension through a horizontal wire fabric.

Figure 2 is a schematic side view of a hybrid wire section and an embodiment of the invention.

Fig. 2A is a partial view of a dewatering control arrangement according to the invention based on the use of a cover mat or belt placed in the area of the forming shoe and applied in the outer part according to Fig. 2.

Figure 2B shows a variation of the arrangement shown in Figure 2A.

Figure 3 is a schematic side view of the application of the invention to a hybrid wire section »conventionally formed from a four-drinier wire section by mounting a new top wire unit on which the invention has been applied.

Fig. 3A shows a schematic side view of the fitting of the cover member according to the invention to the hybrid former according to Fig. 3.

Figure 4A shows a variation of the cover member applied to the hybrid former of Figure 3.

Fig. 4B shows the cover member of Fig. 4A provided with filler strips.

20

Fig. 5A shows a variation of the cover member of Figs. 4A and 4B provided with filler strips.

Fig. 5B shows a possible variation of the cover member of Fig. 5A without filler strips.

Figure 1 schematically shows a step of dewatering and web formation on a fourdrinler wire section at a distance, e.g. 3-8 meters, from the mouth of a paper machine stern box. This distance naturally depends on the type of paper to be produced, the speed of the machine, the consistency of the fiber suspension and many other factors. In the step shown in Figure 1, part of the fiber suspension discharged from the headbox onto the wire has already dehydrated and provided a somewhat coherent fibrous layer 35, i.e. a partially formed web PFW, on the surface of the forming fabric FF. On top of this fibrous layer "dilutes" a dilute fiber suspension DFS, the consistency of which is considerably lower than the consistency prevailing in the headbox. According to the figure, the surface of the dilute 13 84636 fiber suspension still has in many cases a nearly fiber-free water surface FWS.

The web-forming step according to Figure 1 is shown mainly as a schematic diagram, which applies in particular to dewatering processes on the wire sections of rather slow-running machines. In high-speed machines, the dilute suspension layer DFS on the nonwoven PFW formed against the wire is under strong turbulence and / or its fibers are mainly oriented in the direction of travel of the wire FF. The almost non-fibrous surface layer FWS shown in Fig. 10 1 cannot be detected in such a case either.

Figure 2 schematically shows a hybrid former having a basic geometry in accordance with Applicant's U.S. Patent 3,846,233 (corresponding to FI Pat. 50648).

Figure 2 shows a deflector arrangement according to the invention. For the sake of clarity, the frame structure is omitted from Figure 2 and only the former process parts, mainly the wires and their associated dewatering members, and the wire guide rollers are shown. The former mainly comprises a head wire 1, a lower wire loop 2 and an upper wire loop 3.

The headbox 1 feeds the fiber suspension J as a lip jet to the horizontal initial portion A of the lower wire loop 2, which is supported by a chest roll 20, a chest table 4 and a plurality of foils 5,6 or the like. After the horizontal initial portion A, the passage of the wire 2 is directed downwards under the guidance of a partially curved shoe member 8,9 and then continues linearly from the level suction box 25 sideways to the suction roll 11, causing a change of direction in the warp loop 2 so that its return to the guide rollers 21.

The upper wire loop 3 is arranged in co-operation with the lower wire loop 2 so that their common running starts at a substantially curved shoe member 8,9 under the guidance of the roll 30 and continues to the suction roll 11, where the upper wire 3 differs from the lower wire 2 by the position of the roll 32. via conventional guide rollers 31 to the roll 30. The position of the roll 32 is at least height-adjustable so that the wire 3 is made to cover the roll 11 by a sector of the desired size. The position of the roller 30 is also adjustable.

“84636 1 In addition to the above-mentioned parts, Fig. 2 shows water collection troughs 12,13,14. Also shown is a pick-up suction roll 33 which detaches the resulting web W from the wire 2 and transfers it to the felt 34 for further delivery to the press section of the paper machine (not shown).

5

The Former! works as follows: The dewatering of the pulp suspension from the headbox 1 begins in the region of the chest 4 and continues with the initial portion A of the lower wire 2 supported by the foils 5, which is dehydrated relatively gently partly by gravity and at this point a thin fibrous layer begins to form on the surface The number of foils 5,6 or the like can be quite small and their dewatering capacity is affected e.g. by choosing a suitable foil angle so that at the last foil 6, just before the curved shoe 8,9, the suspension fibers have reached a suitable degree of felt 15 at least for the fibrous layer Wq . The corresponding step in the web formation is shown schematically in Fig. 1 described above. Accordingly, the fibers of the initially homogeneous pulp suspension fed to the wire 2 are partially rearranged during the dewatering. As a result of this dewatering process, a thin but relatively uniform pulp layer, i.e. a nonwoven mat, can be found on the surface of the lower wire 2, mainly in the region of the last foil 6, but may still have a relatively dilute pulp suspension where the individual fibers can still move relatively freely. .

25

In the latter step, the nonwoven mat and the suspension on its surface are carried by the lower wire 2 to the area of action of the curved shoe member 8,9 and at the same time the upper roller 3 is guided by the roll 30 at a relatively small angle α to cover the lower wool 2 and its nonwoven mat 30. The position of the roll 30 is mainly vertically adjustable so that the angle α is made to the desired size. As the wires 2 and 3 send each other, the fiber and suspension layer on the surface of the lower wire 2 is gradually subjected to increasing compression. As a result, the dewatering of the formed web becomes more efficient and begins to take place considerably, partly through the upper wire 3, since the non-woven mat covering the lower wool 2 causes a rather high resistance to the downward dewatering.

15 84636 1 The water which tends to escape through the upper wire 3 contains to a considerable extent a so-called fiber suspension. O-fiber and fillers because no similar non-fibrous filter mat or layer has been formed against the upper wire 3 at this stage, which is already present on the surface of the lower wire 2 at this stage. Therefore, the dewatering through the upper wire 3 according to the invention is slowed down by at least the initial portion 8.9 of the forming shoe member. In this case, it is also possible to form a fine-filtering layer against the upper wire 3, which improves the retention of the resulting web W. For this purpose, a plurality of deflector strips 7 are placed on and near the inside of the upper wire loop 3 on a suitable support device 7a, which are at an acute angle to the wire 3, so that the tip of the angle points in the direction of travel of the wire. The suspension water leaving the forming web W through the upper wire 3 in the area of the shoe member 8,9 and the deflector system 7a drifts into the gap between each deflector strip 7 and the upper wire 3. The resulting dam pressure considerably slows down the water penetration in the region of the shoe member 8,9, which is precisely the purpose of the principle and arrangement according to the invention. However, it is not necessary that the deflectors or the like extend over the entire area of influence of the shoe member 8.9.

20

The deflectors 7 are arranged on a special support rail 7a or the like so that their angle with respect to the wire and the distance from the wire can be adjusted. This possibility of adjusting the distance of the deflector from the wire is shown schematically in Figure 2, in which it is shown that there are four deflectors arranged so that the distance of the first and third from the wire is greater than that of the second and fourth. In this context, it should first be noted that the number of deflectors required depends on the working speed of the wire section, the type of paper to be produced, its fiber composition and other factors. The intended result can be achieved, for example, with only two deflectors, if their distance from the wire and also the angle with respect to the wire are chosen appropriately. These choices, of course, require experiments using the fiber suspension in question. These are most preferably carried out initially on a suitable narrow test paper machine, in which the necessary structural modifications of the wire section 35 can be advantageously carried out.

16 84636 Ί In Fig. 2, the shoe member inside the wire loop 2 is shown to have two parts 8,9. These can be connected (arrows S) to e.g. a suction system (not shown) if necessary, which arrangement contributes to the achievement of the objects of the present invention. However, the application of a suction system-5 entails additional equipment and energy costs. In order to avoid these, the operation of said shoe member 8,9 is most simply based on a system according to the invention, which has the same dewatering effect as when using a vacuum effect.

10

The deflectors 7 in the region of the forming shoe 8,9, at any angle to the wires adjacent to the shoe, always cause some degree of pulsation in the fibrous layer between the wires 2,3 and in the web W formed therefrom. Pulsation in turn 15 rearranges the mutual position of the fibers , which results in the fibers settling as evenly as possible and homogeneously between the wires 2,3 covering them. The slower the water leaves the fiber layer at this pulse stage, the more evenly the fibers settle relative to each other. Compression between the wires 2,3 causes -20 to ensure that the uniform distribution of fibers once achieved does not lead to their re-flocculation.

Fig. 2A shows a structure in which the deflectors 7 shown in Fig. 2 have been replaced by a uniform cover 73 made of plastic or rubber sheet. This cover plate 73 is attached to a support structure 70 extending over the entire width of the machine, on which a water collecting trough 71 also rests. triangular in shape, one tip of which is directed to the groove formed by the guide roll 30 and the wire 3 of the upper wire 3, where the upward drainage through the wire 3 begins near the last foil 6. The support structure 70 directs a part of the water separating from the fiber suspension to the trough 71, from which the water is further led to the outlet channel 72 on the rear side of the wire section. The position (arrows) of the trough 71 and its support structure 70 is adjustable. Some of the escaping suspension water drifts into the gap between the cover plate 73 35 and the wire 3 in the region of the forming shoe 8.9. The flexible plate 73, which can extend over the entire area of the shoe 8.9, reduces the amount of water that tends to exit 1 through the upper wire 3. The length of the cover plate 73 in the case of Figure 2A is fixed and can be experimentally selected to suit the purpose.

17 84636

Fig. 2B shows a preferred structure 5 according to the invention, which functionally corresponds to that shown in Fig. 2A and in which the components belonging to it are therefore marked with the same reference numerals as in Fig. 2A. The essential difference between the structures shown in these Figures 2A and 2B is that, as shown in Figure 2B, the cover plate 73 can be wrapped around the shaft 74. A shaft 74 provided with a suitable drive device 10 (not shown) is mounted on a support structure 70.

Thanks to this arrangement, the length of the cover plate 73 in the direction of travel of the wires 2,3 can be infinitely adjusted according to what the dewatering process in the area of the forming shoe 8.9 requires in order to achieve the effects of the invention. The position (arrows) of the support structure 70 and the trough 71 15 is adjustable, whereby the distance between the support structure 70 and the upper wire 3 can also be adjusted to the desired size.

Figure 3 essentially shows a hybrid former in accordance with one embodiment disclosed in Applicant's U.S. Patent 4,164,566. This application is intended for the renewal of conventional fourdrinier wire sections, and also in this connection the deflector arrangement according to the invention has the same effect and meaning as in the hybridformer according to Fig. 2 above.

Figure 3 shows mainly the two-wool part of the hybrid former in question and its upper wool unit in which the invention is applied.

This hybrid former is redesigned from a conventional fourdrinier wire section, of which the lower roller 40, the drive roller 41, the drive roller 42 and the wire guide rollers 43, and 30 a pleated beam 44 supporting a plurality of other devices in the intermediate section are shown, as shown in Fig. 3. . a forming shoe 45 with support structures 46 and an immediately following forming roll 47 resting on a bearing bracket 48. Three beams 49,50 and 51 are further mounted on the beam 44, of which 35, indicated by reference numeral 50, actually operates the so-called as a release box for reliable relocation of the web W formed on the surface of the wire 40 after the two-phase portion over the drive roll 41 to the downward run B between the rollers 41 and 42 18 84636 1 to a point B where the web 52 removes the web W from the wire 40 and moves web W forward to the press section of the paper machine (not shown). The upper wire unit belonging to the hybrid formers is formed by an upper wire loop 54 and guided by wire guide rollers 55. The upper wire unit comprises a forming roll 56 having a water-receiving cylinder shell, the function of which is further described in Applicant's U.S. Patent 4,614,566.

For the sake of clarity, Fig. 3 does not show the JO water collection troughs known per se, which can be arranged, for example, as shown in Fig. 2. One water tray arrangement is shown in Figure 3A below.

Essential to the operation of the hybrid former shown in Fig. 3 is that the partially formed fibrous layer Wq during the downward drainage of the wire 40 before the forming roll 56 enters the contact point between the forming roll 56 and the wire 40, i.e. the nip, where the dewatering also begins through the upper wire 54. As has happened with the structure of Figure 2 and the diagram of Figure 20, a preliminary fibrous layer has formed on the surface of the wire 40 which slows down the water penetration downwards and contributes to directing the dewatering event in the direction of the open surface roll 56. Thereafter, the partially formed fibrous layer or web W is advanced between the wires 40 and 54 over the forming shoe 45 and the roll 47. The shoe 45 is most preferably 25 stripped and may be connected to a vacuum system. However, the use of a vacuum is not always advantageous.

According to the object of the invention, which is to slow down the dewatering through the upper wire 54, a number of deflectors 57 (not shown) are placed inside said intermediate loop 54 and in the area of the forming shoe 45 so as to form an acute angle with the upper wire 54. the direction of travel. The function of these deflectors 57 has already been described above.

35

Fig. 3A shows a possibility for implementing a deflector arrangement according to the invention, e.g. in a wire section according to Fig. 3.

1946636 1 There are three deflectors 57 in Figure 3A and their support structure 58 is adapted to simultaneously form a first collecting trough 59 with discharge channels 60 for the suspension water which, under compression between the wires 40,54, begins to exit the emerging fiber web immediately near the forming roll 56. The operation of the tray 59 is substantially similar to that shown in Figures 2A and 2B above, and reference is made in this regard to the explanations of these figures. Since the bottom of the trough 59 as such acts as a means for regulating the amount of water leaving through the upper wire 54, it is not always necessary to use all three deflectors 57 at the same time, but two or even one is sufficient. Whether this is the first, second or last depends on the other operating parameters of the wire section.

Fig. 4A shows in cross-section a water collecting trough which at the same time acts as a cover plate structure according to the invention. This device can be fitted, for example, in the region of the curved forming shoe 45 of the hybrid former shown in Fig. 3. The trough 80 is made of a steel plate 81, e.g. by welding or pressing, so that the contour of its lower surface, i.e. the bottom of the trough, is sig-sag-shaped. The outermost outline and surface 20 substantially follows the curvature of the guide cover of the forming shoe 45. Important in this contour are troughs 82 which are trapezoidal in cross-section and which extend over the entire width of the wire section perpendicular to the direction of travel of the wires 40,54. The bottom of the troughs 82 has longitudinal slits 83 or similar openings. Water exiting the fibrous mat in the region of the forming shoe 45 by compression between the wires 40,54 is ejected against the bottom of the trough 80 and drifts through the troughs 82 of the plate 81 and the slots 83 therein into the trough 80. The trough 80 is connected to the side The bottom 80 itself is relatively effective 30 in slowing down the drainage of water through the top wire 54. The discontinuities formed by the troughs 82 in the cover plate cause pulsation in the fiber layer Wq between the wires 40,54 and thus improve the formation of the forming surface structure. The distance of the tray 80 from the top 54 is adjustable (indicated by an arrow). In particular, adjusting the position of the 35a edge 80a is important.

Fig. 4B shows a structure which can be used if it is desired to further reduce the drainage through the upper wire and / or if the effect of the pulsation proves to be too strong and to impair retention. In this case, it is possible to provide some of the troughs with trapezoidal filling strips 85 corresponding to the cross-section of the troughs 5. These can be used to make the bottom of the trough 80 substantially completely smooth, either along its entire length or in a suitable part thereof.

Figure 4B shows another possibility for filling the gutters.

The shape of the filler strips 86 used in this case differs from the trapezoid so that one of their tip edges 86c extends to some extent beyond the outermost outline of the cover plate of Fig. 4A. The strips 86 then act as actual deflectors according to the invention. The material of the filling strips 85.86 can be, for example, metal, plastic or ceramic.

15

Figures 5A and 5B show a modification of the water collection trough of Figures 4A and 4B. A common feature specifically between the embodiments shown in Figures 4B and 5A is the 86.95 function of the trough filling strips at the bottom of the trough 90. Although the base 20 of the trough 80.90 as a whole in these solutions reduces dewatering through the top wire, the strips in addition to 86.95 in both embodiments act as "anti-deflectors" acting in the direction of dewatering, especially in accordance with the basic idea of the invention. A special effect when using this trough 90 is achieved by the modification according to Fig. 5B, in which said filling strips are not used at all. As can be seen from the figure, the outer contour of the bottom of the trough has a few conventional deflectors 94 contributing to dewatering, but the bottom of the trough 90 for the most part still functions in accordance with the basic idea of the invention! in particular, if the troughs are filled with similar trapezoidal 30-shaped filling strips 85, which are shown as an alternative for use in Fig. 4B.

In the drawing, Figures 3-5 show only some examples of the application of the principle of the invention. Numerous other implementation-35 possibilities are, of course, possible.

21 84636 ^ The following claims, within the scope of the inventive idea defined by which the various details of the invention may vary and differ from those set out above.

5 10 15 20 25 30 35

Claims (15)

A paper machine hybrid former comprising a first wire coil (2; 40) cooperating with the paper machine's inlet tray (1), the favoring portion (A) of the wire coil forming a first single-wire dewatering zone within the range of the pulp suspension flowing from the inlet tube (1) is dewatered by means of dewatering means (4,5) within the first wire loop (2; 40) down through the wire (2; 40), the former comprising a second wire loop (3; 54) arranged above the moving the wire loop (2; 40) in such a way that the wires (2,3; 40,54) together form a second double wire dewatering zone immediately following the first dewatering zone and the former comprising a dewatering means (8,9; 45) with At least partially curved surface disposed within the first wire loop (2; 40) and at the beginning portion of the second double wire dewatering zone, the curvature center of the dewatering means Ar on the first wire loop (2 ; 40) side and rest dewatering means controls the common course of the first and second wire coils at the beginning portion of the second double wire dewatering zone, whereby at least one device is located at the area of the second double wire dewatering zone (3; 54) which prevents dewatering through the second wire (3; 54) by the pressure of a vaporizer and which most conveniently also regulates, and which extends over the entire working width of the former, can be noted that the device which prevents dewatering has been placed substantially at the dewatering member (8.9; 45) with curved surface at distance from the inner surface of the second wire loop (3; 54). 2. A hybrid former according to claim 1, characterized in that the device which reduces the dewatering comprises at least one deflector means (7; 57; 86; 95) at the area of the dewatering means in close contact with the upper wire loop, which deflector means forms a pointed wind. with the upper wire (3) on the edge so that the tip of the angle points towards the running direction of the upper wire (3). 3. A hybrid former according to claim 2, characterized in that the directional angle of the deflector means (7; 57; 86; 95), the distance from the upper wire (7) and / or the position in relation to said dewatering means are adjustably arranged. 4. Hybrid formers according to claim 2 or 3, characterized in that there are several deflector strips (7; 57; 86; 95) one after the other most preferably so that they can be individually controlled. A hybrid former according to claim 1, characterized in that the regulating device which reduces the dewatering consists of a uniform mat (73) or belt made of flexible guni, plastic or similar material, which from the relative direction of the wires direction of the front. the edge is attached to a support device (70) extending over the entire width of the wires (2,3) in such a way that the mat (73) or the corresponding to the other parts freely rests on the inner surface of the upper winding loop (3). (Figures 2A and 2B). A hybrid former according to claim 5, characterized in that the support device (70) for the flexible mat (73) or the like is provided with a winding shaft (74) around which the mat 20 (73) or the like can be wound by means of a special mechanism for controlling the active length of the mat (73) or the like (Figure 2B). A hybrid molding according to claim 5 or 6, characterized in that the distance of the support device (70) for the mat (73) and at the same time the distance from the beginning end of the mat (73) or the corresponding front of the inner surface of the upper wire loop (3). is arranged to be adjustable. A hybrid former according to claim 5, 6 or 7, characterized in that the position of the support device (70) can be controlled in the direction of travel of the wires. 9. A hybrid former according to claim 1, characterized in that the device which reduces the dewatering is a cover plate structure (80-89; 90-99) with a gutter-shaped surface, the cross-section of which is made in a zigzag form 27 84636 and is of rigid material, advantageously style, whose grooves (82.96) are open downward against the Upper wire loop (54). A hybrid former according to claim 9, characterized in that the bottom of the grooves (82; 96) in the cover plate construction has openings (83; 97) which allow the water to flow through the cover plate. 11. Hybrid molds according to any of claims 9-10, characterized in that fill strips (86; 96) are placed in the grooves (82; 96) whose shape corresponds to the deflectors, which molds form an acute angle with the upper the wire (54) in such a way that the tip of the angle points towards the running direction of the upper wire (54). 12. A hybrid former according to any one of claims 9-10, characterized in that at least part of the cover-bag's zig-zag profile itself consists of deflectors which reduce the dewatering which forms an acute angle with the upper wire in such a manner. that the tip of the angle points towards the direction of entry of the wire. A hybrid former according to claim 10, 11 or 12, characterized in that at least part of the channels (82,96) are provided with filling strips which most preferably have a straight surface to prevent water from flowing through the channels. A hybrid former according to any one of claims 9-13, characterized in that the cover plate structure forms a collection sanctity for water which is removed by the action of a dewatering means with curved surface inside the first wire loop (54). A hybrid former according to any of claims 9-14, characterized in that the distance of the cover structure from the upper wire (54) can be regulated uniformly or for either end.