FI96524C - Former with MB unit for paper machine - Google Patents

Description

9652/5

Paper machine former equipped with MB unit Formare med MB-enhet för pappersmaskin

The invention relates to a paper machine former comprising a lower wire loop with wire guide and dewatering elements, the mold comprising an upper wire unit with a roll-guided upper wire, and the former having a single wire initial section or MB formation zone with a single double wire belt. are oppositely loaded lists.

Several different forming members are used in the web forming sections of a paper machine. The main purpose of these members is to provide compression pressure and pressure pulsation to the resulting fiber layer 15, which promotes dewatering of the forming web while improving its formation. Said forming members include various forming shoes, usually with a curved strip cover, over which the overlapping forming wires and the web between them are curved.

20 In the area of these forming shoes, water escapes through the wire on the side of the outer curve due to its tightening pressure, and this dewatering is further assisted by a centrifugal force field. Dewatering also takes place through a wire on the side of the inner curve, which is usually enhanced by the vacuum in the chamber of the forming shoe. The strip cover of the forming shoe 25 provides a pressure pulsation that both promotes dewatering and improves web formation.

In addition, the so-called MB units through which pass, usually in a straight run, two opposite wires. Inside the second wire loop of the known MB-yk-30 units there is a pressure loading unit, and inside the opposite second wire loop there is a dewatering unit provided with a control and dewatering strip. As is already known, this MB unit is generally placed on the flat wire section, so that the MB unit is preceded by a considerably long single wire section 35 with a substantial amount of dewatering before the web passes in a straight run in the flat wire plane through the MB unit. For structural details of known MB units, reference is made as examples to • the applicant's FI applications 884109 and 885607.

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A variety of hybrid and twin wire toners with the MB unit or units described above are already known. For these, reference is made to the following FI patent applications 884109, 885608, 904489, 905447, 920228, 920863, 924289, 930927, 931950, 931951, 931952, 5 932264, 932265, 932793 934667 and 934999.

In addition, the invention is closely related to International Patent Application WO 93/12292, filed by J.M. Voith GmbH, a hybrid former shown in which, after the single-wire initial section, at the beginning of the two-wire zone there is a forming shoe inside the 10 lower wire loops, which causes pressure pulsation in the pulp web formed on the lower wire. Indeed, the pressure pulses of the static forming shoe cause a ripple on the upper surface of the track, which, when "solidified", appears as said vanity.

15 The previously known MB formation and load list zones have been quite long in the machine direction. In addition, the load lists in the MB zone are cumbersome to manufacture and have been required in large numbers, which has made the structure quite expensive and complicated. The disadvantage of suo-. There have also been stability problems with the lateral guidance of the wires in some MB zones.

The object of the present invention is to provide a new former concept which essentially retains the advantages of the previously known MB former, such as good formation and efficient double-sided dewatering.

The object of the present invention is to provide an MB former which avoids the above-mentioned drawbacks and in which a relatively short loaded MB strip zone can be used, so that a relatively small number of difficult-to-manufacture load strips can be handled.

It is also a non-essential additional object of the present invention to provide a former, in particular a hybrid former, suitable for the regeneration of 35 flat wire sections, whereby the lower wire loop with its body can be an old flat wire structure and the former flat wire section can be regenerated into an un-nm <9652/3 MB hybrid it with a new upper wire unit and the necessary dewatering equipment.

In order to achieve the above and later objects, the invention is mainly characterized in that the MB unit is followed by a curved two-wire zone guide strip and then a counter-curved strip inside the opposite wire loop, after which the paper web is separated from the top wire and the upper wire. To point 10.

Especially in guitar formers, a curved strip shoe arranged in the direction of travel of the wires before the MB unit can be located substantially immediately after the forming roll in the region of the forming crystal. The radius of curvature of this most suitable 15-min short strip shoe is most preferably arranged on the underside loop side, i.e. the radius of curvature of this first strip shoe is parallel to the curvature guiding the two-wire zone of the next strip shoe after the MB zone.

Although the most preferred embodiments of the invention are known in the art to be hybrid formers, the invention can also be applied to guitar formers, most preferably guitar formers having a forming roll within the upper wire loop. , which is inside the lower wire loop and in the suction zone of which the two-wire zone curves downwards.

The hybrid former of the present invention is particularly suitable for rebuilding very old flat wire sections when the flat wire sections are modernized to provide higher web speed and better paper quality. It should be emphasized, however, that the former according to the invention is also suitable for use in new structures.

35 9652 ·· 4

A relatively short loaded MB-strip zone can be used in the invention, whereby the number of difficult-to-manufacture load-bearing strips can be considerably reduced. In addition, the invention provides stable control of the wires in the two-wire zone also laterally when two forming strip zones are curved in opposite directions after the MB strip zone, above which a drainage box system is arranged.

In the following, the invention will be described in detail with reference to an embodiment of the invention shown in the figures of the accompanying drawing, to the details of which the invention is in no way narrowly limited.

Figure 1 shows a schematic side view of a lay-out of a hybrid-15 former according to the invention.

Figure 2 shows the two-wire zone of the hybrid former of Figure 1 on a larger scale.

Figure 3 shows a preferred embodiment of a gutter former of the invention.

Figure 4 shows an alternative implementation of the initial portion of the two-line zone of the kit former. 1 2 3 4 5 6 7 8 9 10 11 il III I IMI IIHH i

The hybrid former according to Fig. 1 comprises guide rollers 11, a chest roll 2 11a and a lower wire loop 3 10 controlled by a wire suction roll 15 and a draw roll 16. The headbox and the lower wire loop 10 with frames, rollers 4 11,11a, 15,16 and , in which the 6 old flat wire sections are modernized to provide a higher web speed and a better 7 paper quality. In these renewals, the flat wire section 8 is provided with an upper wire unit 40 according to the invention and a new dewatering equipment 12,13,14,22,23. The plane T-T marked in Fig. 1 is a web forming section of an old planar wire. The invention is also suitable for use in new structures 11.

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A pulp suspension plug J with a fiber density of the order of 0.7 to 1.5% is fed through the lip portion 12 of the headbox to the single-wire horizontal initial portion 10a of the lower wire 10. In the hybrid former according to Figures 1 and 2, at the initial section 10a of the forming zone, the track WD 5 is dewatered by means of dewatering means (not shown) known per se, so that the lower surface of the track W i against the wire 10 gets a certain degree of felting at the beginning of the two-wire zone 10/20. The dry matter content of the track W0 at the beginning of the two-wire zone 10/20 is k0 <1.2 ... 2.2%.

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The former comprises an upper wire unit 40, the upper wire 20 of which is guided by guide wires 21 and a chest roll 21a. After the single-wire zone 10a, the double-wire zone 10/20 begins at the pressure-loaded strip pair 35. The two wire zones 10/20 terminate in the region of a suction rod 15 with a curved cover 14a. The suction box 14 ensures that the web W follows the lower wire 10, from which it is separated at the pick-up point P between the rollers 15 and 16 and transferred by the pick-up fabric to the press section (not shown). 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Figure 3 shows a preferred embodiment of the guitar former 2 of the invention, the two-wire zone of which is substantially similar to the hybrid former of Figures 1 3 and 2. Unlike hybrid former applications 4

as shown in Figure 3, the headbox 12 feeds the pulp suspension jet J

5 directly to the forming roll G bounded between the breast roll 11A inside the lower wire loop 10 and the forming roll 21A, preferably the suction roll, inside the upper wire loop 20. With the overhead forming roll 8 21A, the two-wire zone begins and curves upward in sector a. The size of the sector 9a is preferably a ~ 0 ... 45®, preferably a »0 ... 30 °. After sector a 10, the two-wire zone continues upward in substantially the same way as in the hybrid former of Figures 1 and 2. According to Fig. 3, at the end of the double-wire zone, inside the lower wire loop 10, there is a second forming roll 17, in the area of which the double-wire zone 14a curves downwards. After the suction zone 17a, the web W is separated from the upper wire 20 to follow the lower wire 10 to the pick-up point P. There is a water collecting trough 18 on and after the suction zone 17 of the second forming roll 17.

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The implementation of the double wire zone is best seen in Figures 2 and 3, according to which there are two successive dewatering boxes 22 and 23 inside the upper wire loop 20, each with two successive dewatering chambers 22a, 22b and 23a, 23b. These chambers 22 and 23 have drainage channels 24 on either side of the pape-5 breaker. Chambers 22a, 22b and 23a, 23b are connected by common suction pumps (not shown) so that separately adjustable pressures P1. P2 can be provided in the different chambers. P3 and p4 for dewatering control. Fixed below the base 22c of the first chamber 22a are 10 stationary forming strips 28, of which the first strip 28a acts as a suction deflector strip of the chamber 22a, limiting the suction deflector channel 26a at its lower end. The front edge of the base 22d of the second chamber 22b has a single forming strip 28b. The space 22e below the bottom 22d of the second chamber 22b as well as the space 23e below the third chamber 23a, which spaces 22e 15 and 23e are at the strip cover 13a of the suction box 13, are without the forming list. The space 23f below the base 23d of the last suction chamber 23b has a strip 29, the first strip 29a of which serves as a deflector strip of the suction deflector channel 27a of the third chamber 23a.

As shown in Figure 2, the two-wire zone 10/20 begins with an MB unit 12 comprising fixed forming strips 28, 28a inside the upper wire loop 20 and strip pairs 35, 36a, 36b inside the lower wire loop 10 loaded with medium pressures ρ * 0, pkl and pk2 supplied to the hoses 37. The first load list pair 35 forms a preload zone 25 which does not have a stationary counter strip. The strips 28,28a, 28b and 36a, 36b of the MB zone alternate to form the beginning of a two-wire zone with adjustable load, which provides efficient bidirectional dewatering and a sufficiently efficient pressure pulsation to ensure good formation of the web W. The strip pairs 30 35, 36a, 36b are loaded against the stationary strips 28a, 28 with separately · 'adjustable pressure medium pressures supplied to the hoses 37.

Pko.Pki And Pk2 · According to Figures 2 and 3, the MB strip zone is substantially straight, which is most preferred, but a curved strip zone, preferably an upwardly curved zone 35 having a curvature opposite to the curvature of the strip cover 13a, may also be used within the scope of the invention. Through the suction deflector channel 26a, the water leaves il i IM i Hi! IITA 7 9c .: 2 deflector 28a in front of the negative pressure p1 and the water kinetic energy of the impact direction of the arrow F into the chamber 22a and from there further through the duct 24 onto the paper machine or to the side.

The box 39 below the 5 MB unit 12 can be connected to a vacuum source (not shown) if necessary. Between the slats 28, water exits through the space 22c of the bottom 22c of the chamber 22a to the second chamber 22b via the channel 26b, assisted by a vacuum p2. The MB list 28 / 35,36a, 36b is straight in its main direction. In Fig. 2, for the strip 28b, the dry matter content of the web W is of the order of ^ ... 3.5 ... 4%. The two-wire zone then curves (R 1 downwards under the guidance of the curved strip cover 13a of the forming shoe 13 arranged inside the lower wire loop 10. The forming shoe 13 is connected by a suction foot 13b to a vacuum. At the cover 13a there are no forming strips inside the upper wire loop, but exits through the duct 27a with the aid of a vacuum p3 to a second suction deflector chamber 23a having a suction deflector strip 29a at its lower end.After the strip cover 13a of the forming shoe 13, the strip 29a, 29 directs the two-wire zone to curve (R2) in into the chamber 23b assisted by a vacuum p *.

The two-wire zone terminates in the area of the curved (R3) cover 14a of the suction box 14 inside the lower wire loop 10. At the end of the two-wire zone, the dry matter content of the web W is of the order of k2 = 7 ... 10%.

25

According to Figure 2, the drainage boxes 22 and 23 are suspended by means of brackets 31 fixed to their roof wall on vertically displaceable supports 32 used by the control gears 30 so that the printed wires 10/20 against the strips 28a, 28, 28b, 29a, 29 and the alignment can even be adjusted and changed while driving to ensure proper operation of the two-zone zone. The dewatering boxes 22a, 22b and 23a, 23b shown in Fig. 3 are also suspended for adjustable position by devices similar to the devices 30,31,32 shown above, which are not shown in Fig. 3 for simplicity.

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An essential feature of the invention is that after the MB unit 12 there are two successive strips 13a and 29a, 29 with opposite curvature (Rx and R2), at which there is no loaded counter-strip. Thus, the length L 5 of the loaded MB zone is made relatively short, but long enough to ensure good formation and efficient, two-way dewatering. The length L of the MB zone is generally selected from the range L = 150 ... 1000 mm, preferably L »400 ... 600 mm. The radii of curvature RltR2 and R3 of the strip zones marked in Figure 2 are generally selected from the ranges R3 «2. .. m, R2 ~ 3.. .10 m 10 and R3 * 5 ... 10 m, preferably from the areas R1 «3 ... 5 m, R2« 5 ... 8 m and R3 »5 ... 8 m.

Figure 4 shows an alternative embodiment of the initial portion of the two-wire zone of the kit former according to the invention. This initial portion is otherwise similar to that shown in Figure 3 and described above, except that substantially immediately after the forming roll 21A, a first forming shoe 40 with a curved strip cover 40a is arranged inside the lower wire loop 10. The forming shoe box 40 can be connected to a vacuum shown by arrow p0. With a vacuum p0, dewatering can be promoted through the slit gaps 41 of the cover strips 40a. The first forming shoe 40 is preferably relatively short in the machine direction, substantially shorter than the second forming shoe 13. The radius of curvature R0 of the first forming shoe 40 is generally selected from the range R0 <3 ... 8 m. The radius of curvature R0 is parallel to the radius of curvature Rx of the second forming shoe 13. After the first forming shoe 40, a loaded MB-strip zone 28/36 substantially as described above follows substantially immediately. After the last loaded list 36, another fixed list 42 is arranged inside the sub-wire loop 10. 1 2 3 il: l »l IMI I U it ·

The following claims set forth within the scope of the inventive idea defined by the various details of the invention may vary and differ from those set forth above by way of example only.

Claims (14)

9652 '9 A paper machine former comprising a lower wire loop (10) having wire guide and dewatering elements, the former comprising an upper wire unit (40) having an upper wire (20) controlled by rollers (21, 21a; 21, 21A), and wherein the former has an MB unit (12) with oppositely loaded strips (28a, 28 / 36a, 36b) after the single-wire initial portion (10a) of the forming zone or the forming crystal (G) in the next double-wire zone (10/20), characterized in that the MB unit (12) is followed by a curved (Rx) two-wire zone guide strip (13a) and then by a strip (29a, 29) of opposite curvature (R2) inside the opposite wire loop (20), after which the paper web (W) is separated from the upper wire (W). 20) and guided by the downline (10) to the pick-up point (P). 15 Former according to claim 1, characterized in that the two-wire zone element is arranged before said MB unit (12) at the beginning of the two-wire zone with a strip shoe (40) with a strip cover (41) having a radius of curvature (R0) parallel to said MB zone (12). then the radius of curvature (Rj) of the strip cover (13a) of the next forming shoe (13) (Fig. 4). Former according to Claim 1 or 2, characterized in that the oppositely loaded strip (28a, 28 / 36a, 36b) 25 of the MB unit is relatively short in the machine direction, so that its length L is selected from the range L »150 ... 1000 mm , preferably in the range L «400 ... 600 mm. Former according to any one of claims 1 to 3, characterized in that inside the upper wire loop (20) there is a drainage box system (22, 23) at said strips 30, through which drainage channels (26a, 26b, 27a, 27b) in the region of said strip the water leaving the web (W) through the upper wire (20) is preferably guided by suction, to the side or sides of the paper machine. 1 Former according to one of Claims 1 to 4, characterized in that a forming shoe (13) with a downwardly curved (Ri) strip cover (13a) follows the loaded strip zone (36a, 36b / 9652 10 28a, 28) of the MB unit (12). which is preferably connected by a suction foot (13b) to a vacuum so that said strip cover (13a) is followed by a forming strip (29) with an opposite curvature (R2) inside the upper wire loop (20), followed by a strip (10) inside the lower wire loop (10) a suction box (14) with a strip cover (14a) having a curvature (R3) in the opposite direction to the previous one, in the region of which the web (W) is separated from the upper wire (20) to follow the lower wire (10). 10 Former according to one of Claims 1 to 5, characterized in that before the loaded strip zone (36a, 36b / 28a, 28, 28b) of the MB unit (12) there is at its beginning inside the double-wire zone (10) a pressure strip a preload strip or strip (35) loaded with pressure (pk0) 15, preferably a pair of strips, followed at a small distance by a first stationary deflector strip (28a) inside the upper wire loop (20). Former according to one of Claims 1 to 6, characterized in that the dewatering box system in the two-wire zone consists of two separately supported (30, 31, 32) boxes (22, 23), each having, preferably two, its own dewatering channel (26a, 26b); 27a, 27b) with dewatering chambers (22a, 22b and 23a, 23b) connected (25) to vacuum sources (P1.P2.P3.P4) and to: 25 dewatering channels (24). Former according to Claim 7, characterized in that the first chamber (22a) of the first dewatering box (22) is provided with a suction deflector channel (26a) arranged on its front wall, the lower end of which has a suction deflector strip (28a) serving as the first stationary support strip in the MB zone. that the second chamber (22b) of the first dewatering chamber (22) is provided with a dewatering channel (26b) having a last stationary support strip (28b) in the MB zone at its lower end, and a rear wall of the first chamber (23a) of the second dewatering box (23) in connection with a suction deflector channel (27a), the stationary support strip (29a) at the lower end of which is il; IS 1 III! n m »? 9652/11 placed after the curved (Rx) strip cover (13a) inside the lower wire loop (10) and that the last dewatering chamber (23b) of the second dewatering box (23) comprises a dewatering channel (27b) connected to its rear wall, which opens to the last 5 curved zone of the double wire zone (R2). ) to the strip spacing of the strip (29a, 29) to transfer the water leaving the web (W) through them to the last dewatering chamber (23d). Former according to Claim 8, characterized in that the two dewatering boxes (22, 23) are suspended on control brackets (31, 32) used by adjusting gears 10 (30) or the like, so that the two dewatering boxes (22, 239) can be aligned and printed separately on the wires (10). , 20). Former according to one of Claims 1 to 9, characterized in that there are one to three pairs (36a, 36b) of strips loaded with the pressures of the pressure medium (Ρια.Ρια) of the MB unit (12) and 3. .7 stationary support strips (28a, 28,28b) inside the upper wire loop (20). Former according to one of Claims 1 to 10, characterized in that the MB zone is substantially straight in that the radius of curvature R 1 of the downwardly curved first strip zone (13a) is selected from the range Rx s® 2 ... 8 m, preferably from the range Rx = 3. ..5 m that the radius of curvature R2 of the last curved strip zone (29a, 29b) is selected from the range: 25 R2 ~ 3 ... 10 m, preferably from the range R2 »5 ... 8 m. Hybrid former according to one of Claims 1 to 11, having a single-wire initial portion (10a) of the forming zone with dewatering elements inside the lower wire loop (10) and then wire guide and dewatering elements inside the lower wire loop (10), characterized in that the single-wire forming zone after the (10a) section, the next double-wire zone (10/20) starts with the MB unit (12). 1 Hybrid former according to one of Claims 1 to 11, characterized in that the various dewatering elements and process parameters 9652/12 meters are arranged and adjusted so that the dry matter content of the web (W0) after the single-wire zone (10a) and at the beginning of the double-wire zone is k0 »1.2 ... 2.2%, that the dry matter content of the web (W) after the MB zone is kx <3.5 ... 4% and that the dry matter content of the web (W) at the end of the two-zone 5 zone is k2 ~ 7 ... 10%. Kit according to one of Claims 1 to 11, characterized in that the two-wire zone begins after the chest roll (11A) inside the lower wire loop (10) in the curved sector a of the forming roll (21A) inside the upper wire loop (20), where the two-wire zone begins and curves in sector a = 0 ... 45®, preferably a = 0 ... 30® upwards and that at the end of the two-wire zone there is a second forming roll (17) inside the lower wire loop (10), in the region of which the two-wire zone curves downwards and after which the paper web 15 (W) is separated from the upstream (20) to follow the downstream (10) to the pick-up point (P). il · HU I 14-m - 9652 /: 13