FI95489B - System of drainage chambers in a double-wire former - Google Patents

Description

5 95489

Double wire formwork dewatering chamber system System av avvattningskammare i en dubbelviraformare

The invention relates to a dewatering chamber arrangement of a two-wire former, which two-wire former comprises a two-wire zone in which a wire loading unit is arranged inside the second wire loop. a dewatering chamber connection connected to a dewatering duct or duct through which the water leaving the web through the slit spaces of the strip acting against the inner surface of the upper wire loop is discharged from the web, and the dewatering chamber purchase is arranged at least

Several different forming members are used in the web forming sections of a paper machine. The main purpose of these members is to provide a pressure pulsation in the resulting fibrous layer, which promotes dewatering of the forming web and at the same time improves its formation. In addition, a number of different forming shoes, usually with a curved strip cover, are already known, over which the overlapping forming wires and the web between them are curved. In the area of these forming shoes, water escapes mainly through the wire on the outer curve side due to its tightening pressure, and this dewatering is further aided by a centrifugal force field. The molding cover of the forming shoe provides pressure pulsation that both promotes dewatering and improves web formation.

In addition, the so-called MB units through which two opposite wires • usually run in a straight line. Inside the second wire loop there is a pressure-loaded loading unit and inside the opposite second wire loop there is a dewatering unit with a guide and dewatering strip. Previously, the HB unit in question was generally placed on a flat wire section so that it was preceded by a remarkably long single wire section with a substantial amount of dewatering 95489 2 before the web passes a straight run in the plane of the flat wire through the MB unit. For structural details of MB units, reference is made, by way of example, to Applicant's FI applications 884109 and 885607. It should be emphasized that the present invention encompasses both hybrid formers with 5 single wire initial sections and other . The two-wire zone can be either curved or straight and its main direction can be horizontal, ascending or descending. In general, the angle of rise or fall of the two-wire zone is 10 <45 °, because at larger angles the disadvantages which the invention is intended to eliminate do not occur, at least not very clearly.

Several different hybrid and double wire formers with the MB unit or units described above are already known. For these 15, reference is made to the following FI patent applications 884109, 885608, 904489, 920228, 920863, 924289 and DE application 40 02 305.

The prior art MB units use a plurality of successive dewatering chambers 20 with their own dewatering channel inside the upper wire loop, each with an adjustable or adjustable vacuum level. This chamber purchase has to be dimensioned quite high due to the large amounts of water to be removed. The known successive chambers have substantially the same vertical cross-sectional area in the machine direction, although the amount of water to be removed through the first chamber is considerably greater than the amount of water to be removed through the next and latter chambers. In addition, a relatively high vacuum level has to be used in these chambers, which is partly due to the high water level in these chambers. The high vacuum level results in the disadvantage that the inner surface 30 of the upper wire rubs with relatively high force against the dewatering and guide strips in the felt of the bottom of the dewatering chambers, resulting in excessive wear of the wire and also of these strips.

The length of the known two-wire MB zones is generally of the order of 35 1.5 m and, using previously known dewatering chamber arrangements, makes it difficult to obtain a sufficient water volume for this length; i! i I: | 95489 Drainage chamber purchase with 3 combustion capacity without unfavorably high construction height. On the other hand, in Formeri renewals, for example, the space available to the upper wire unit is often quite limited.

5 Indeed, the difficulties described above have led, in particular in the case of rebuilders, to the need to provide dewatering channels in the first dewatering chamber of the chamber for both the operation and maintenance side of the paper machine. Treatment side drainage channel is very problematic, because it must be passed across the paper machine back to the width of the driving side of the wire pit 10 for connection. Treatment side drainage channels also have the disadvantage that they have a number of other functions, such as the wire-break, the MB-unit exchange lists and the MB-unit measures the washing path.

The object of the present invention is to further develop the previously known two-wire MB units and in particular their dewatering chamber purchase arrangements, so that the disadvantages discussed above can be substantially avoided.

It is a particular object of the invention to provide an MB-former dewatering chamber purchase arrangement in which a relatively small but adjustable or adjustable vacuum can be used so that the pressure between the dewatering and support strips opposite the inner surface of the upper wire sex.

It is a further object of the invention to provide a dewatering chamber purchase arrangement for a former MB unit in which a dewatering duct or ducts can only be arranged on the drive side of the machine.

It is a further object of the invention to provide a dewatering chamber arrangement of a former MB unit which is simple in construction and which takes up even less space in the height direction.

35 4 95489

In order to achieve the above and later objects, the invention is mainly characterized in that below said dewatering chamber there is a strip block in which the vacuum in different blocks and / or the amounts of water leaving the web 5 upstream through the different blocks are arranged to be adjustable or adjustable.

Although a relatively low vacuum can be used in the dewatering chamber assembly according to the invention, the pressure of the strip blocks of the two-wire-10 zone control strip can be individually controlled below the chamber assembly. In addition, in case the dewatering chamber and that the height of the drainage chamber is kept relatively low. 15 last-mentioned advantage is also the fact that the drainage channel or -kanavisto need to be placed only on the drive side of the machine, wherein the front side and the channels discussed above drawbacks resulting therefrom is avoided.

In the following, the invention will be described in detail with reference to some application examples of the invention schematically 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 an application of the invention to the gutter sea with an ascending MB two-wire zone.

Figure 2 shows on a larger scale the dewatering chamber arrangement according to the invention of the kit former of Figure 1.

Fig. 3 shows an example of an adjustment strip with which the throttling of the suction opening of the bottom of the dewatering chamber and the flow cross-section can be adjusted.

Figure 4 shows a cross-section IV-IV in Figure 3.

95489 5

Figure 5 shows a schematic machine direction vertical cross-section of an MB two-wire zone of a hybrid former equipped with a dewatering canopy arrangement according to the invention.

Figure 6 shows, in a manner similar to Figure 5, a preferred drainage chamber purchase arrangement according to the invention.

Figure 1 shows a kit forming a MB unit 100 with a dewatering chamber purchase 15A according to the invention. Former! comprises a covering wire 10 guided by guide rollers 10 12 and a chest roll 11 and a load-bearing wire 20 guided by guide rollers 12 and forming rollers 21 and 25. A pulp suspension jet J is fed from the headbox lip portion 33 to a wire roll 10,20 between the chest roll 11 and the forming roll 21 with suction zone 21a. the forming zone starts after the grid 15G with the suction zone 21a of the forming roll 21, followed by the MB unit 100, under the control of which 26-26 the two-wire zone curves with a relatively large radius of curvature R0 »5 ... 12 m (Fig. 2).

After the MB unit 100, there are planar boxes 24 inside the carrier wire loop 20. After the planar boxes 24, the two-wire zone continues with two successive suction zones 25a and 25b of the second forming roll 25. The latter suction zone 25b ensures that the web W differs from the covering wire 10 and follows the supporting wire 20. Inside the loop of the covering wire 10 there is a dewatering box 16 with a dewatering channel 16a above the suction zone 25a 1 · 25 of the forming roll 25.

The guide roller 12 'after the dewatering box 16 guides the wire 10 to its return run. The web W is detached from the wire 20 in the suction zone 31a of the pick-up roll 31, where it is transferred to the pick-up fabric 30 and further to the press section (not shown). In Fig. 1, the pitch angle of the two-wire-30 zone is denoted by a: 11a. When the dewatering chamber purchase 15A of the MB unit 100 according to the invention is used, it is generally α <45 °, whereby the problems which the invention is intended to eliminate are disturbing.

As shown in Figures 1 and 2, the MB unit 100 comprises a dewatering chamber section 15A, preceded by a suction deflector unit 13 having a dewatering chamber 15e with a dewatering channel 14e led to the wire well on the machine side. Connected to the pre-chamber 15e is a suction deflector channel 35a bounded between the vertical walls 35b and 35c. The lower end of the channel 35a is on the suction zone 21a of the forming roll 21 bounded by a curved wall 34. The channel 35a is removed through a substantial amount of water in the direction of the arrow F1 pre-chamber 15e, the current 10 through the negative pressure p0 and the wire exiting from the forming web with the water kinetic energy of the impact.

The upper part of the chamber assembly 15A according to Figures 1 and 2 is a uniform sub-10 pressure space without partitions. The chamber acquisition 15A is divided into three compartments 15a, 15b and 15c by partition walls 16a and 16b which do not extend to the upper wall 15c of the chamber acquisition 15A. Kammiostossa 15A is a transverse end walls 35c and 15d in both the machine direction of the end walls, which are related to the machine operating side of the end walls of the water discharge channels 14a, 14b and 14c. The compartments 15 15a, 15b, 15c are bounded below by walls 19a, 19b, 19c, below which there are strip blocks 37a, 37b, 37c which open into the slit spaces 36R of the stationary drainage guide strips 36,36a, 36b. In connection with the upper end of the walls 19a, 19b, 19c there are transverse flow slots 18a, 18b, 18c, the throttling and flow cross-sections of which are arranged to be adjustable by means of slides 20 17a, 17b, 17c by moving them in the direction of arrows B. Using said slides 17a, 17b, 17c, the vacuum prevailing in the strip blocks 37a, 37b, 37c can be adjusted and in this way affect the web formation and the amounts of water leaving the various compartments 15a, 15b, 15c through the upper wire 10 and their distribution.

, · '25

According to Figures 1 and 2! the first list of the control list 36 below the chamber assembly 15A is indicated by reference 36a and the last list by reference 36b. Opposite the strip 36 there is a loading unit 23 of the MB unit 100, the body part 28 of which is provided with support strips 26 supported by means of pressure hoses, which are connected to each other in pairs by intermediate parts 29. The drainage and guide strips 36 and the load strips 26 are arranged alternately to extend transversely over the entire width of the wires 10,20. The load strips 26 are loaded against the inner surface of the wire 10 with pressure medium pressures pk applied to the hoses 27. The bifurcation zone 35-35 travels, under the guidance of the strips 26 and 36, a gently undulating path in Fig. 2 with a large radius of curvature R0, in Fig. 5 with a large radius of curvature R3, and in Fig. 6 substantially straight in the horizontal direction. The first list of the load list 26 is denoted by reference 26a and the last list by reference numeral 26b. The load strips 26, 26a, 26b press the web W of the lower wire 10 and the support 5 of the guide strips 36a, 36, 36b against the upper wire 20, and this pressing contributes to the drainage through both wires 10,20.

Figures 3 and 4 show a more detailed embodiment of how the choke gap 18 of the strip blocks 37a, 37b, 37c can be arranged to be adjustable. In connection with the lower walls 19 of the compartments 15a, 15b, 15c of the chamber section 15A, rotatable control rods 17 with a series of flow openings 18k are arranged. At 17k, the adjusting rod 17 is full and has a circular cross-section. The circular adjusting rod 17 is pivotable via its end pins 19k by an actuator 19A. In Figure 4, the control rod 17, 15 is semi-opened position, and rotating the adjusting rod 17 in the direction D len those actuator 19A is obtained virtausaukostoa 18k and the flow F2 further choked and accordingly the direction of arrow A by the actuator 19A is obtained by rotating the throttling of the flow F2 to be reduced. The adjusting rods 17 can be assembled in successive parts so that the throttling of the flow opening 18k 20 can be arranged in the transverse direction of the web W to be profiled for the transverse profile adjustment of the vacuum of the strip blocks 37a, 37b, 37c.

Figure 5 shows an embodiment of the invention for a hybrid former comprising a single wire lower wire portion 20a having per se known dewatering means (not shown) so that the web W0 has time to reach a certain degree of felting before it enters the double wire zone starting at the guide roll 11 of the upper wire 10. After the guide roll 11, at the beginning of the two-wire zone, inside the loop of the lower wire 20, there is a first forming shoe 41 having a strip cover 41a having a radius of curvature Rx. This is followed by the MB unit 100, which begins within the upper wire loop 10 is imudeflektoriyksikkö 13, a fixed deflector list 36a opens after imudeflektorikanava 35a, through which the water exits the pre-chamber 14e of the arrow Fx direction.

35 95489 8

In Fig. 5, the MB unit 100 has, inside the loop of the upper wire 10, a dewatering chamber purchase 15B according to the invention, in which said pre-chamber 14e and a chamber 15a connected to the same vacuum pj as its unit are integrated. The pre-chamber 14e under a first list in block 37a, which opens to the front five edges the adjustable kuristusrakoon 18a, which is controlled by an arrow B direction of the movable slide 17a or as shown in Figures 3 and 4 control rod 17. Similarly, Title 15a in the first head, the second list block 37b is opened at its front edge a slide 17b or the like, with a throttle gap 18b adjustable by the adjusting rod 17. A similar structure is also provided in connection with the strip blocks 17c and 17d, which open into the throttling slots 18c, 18d, which are adjustable by means of slides 17c and 17d or corresponding adjusting rods 17. Below the strip blocks 37a and 37b there is a loading unit 23 which does not extend below the strip blocks 37c and 37d.

The MB unit 100 is followed by a second forming shoe 42 inside the loop of the lower wire 20 with a strip cover 42a having a radius of curvature R2. By means of suction acting through the strip cover 42a, the web W is separated from the upper wire 10 to follow the lower wire 20.

According to Fig. 5, the slides 17a, 17b, 17c, 17d adjust the vacuum prevailing in each of the house blocks 37a, 37b, 37c, 37d. If, for example, the vacuum section p <20 kPa produced by the suction pump 40 prevails in the chamber section 15a, then the pressure prevailing at the upper surface of the slides 17a, 17b, 17c, 17d is 15 kPa, assuming that the water surface height H0 = 500 mm. If, for example, a vacuum of 5 kPa is required in the strip block 37a, the pressure drop of the flow Fa at the throttling point 18a is adjustable to 10 kPa. With said vacuum of 5 kPa in the strip block 37a, it is possible, for example, to prevent the water collected in the compartment 15a from flowing back into the strip block 37a. Thus, by means of the slides 17a-17d, the pressures of the strip blocks 37a-37d can be arranged to be staggered for optimum web formation and dewatering 30. By staggering the pressures in the strip blocks 37a-37d, it is also possible to adjust the amounts of water entering the different compartments 15a, 15b and 15c and in this way divide the water leaving the web W according to the discharge capacity of the different drainage channels 14a, 14b, 14c. In addition, transverse pressure profiling can be used by arranging the throttling slots 35 18a in the transverse direction, e.g. for block adjustment, as described in connection with Figures 3 and 4.

«· Il lllt» lilll IKI # »'i 95489 9

By using one uniform chamber 15a of the dewatering chamber 15B according to Fig. 5, the advantage is obtained that the cross-sectional area of the dewatering channel 14B is multiplied, thus facilitating water treatment so that no other dewatering channel is needed on the treatment side of the machine. leads through channel 14B off completely on the machine side.

Fig. 6 shows an alternative embodiment of the invention with a pre-chamber 15e in the dewatering chamber 15C of the MB unit 100 as described above, with a vacuum p0 provided by a suction pump 40. The chamber 15C is only uniform at its top so that it has the same the vacuum level px provided by the suction pump 40. The first strip block 37a is connected to the suction duct 39a, the second strip block 37b is respectively connected to the suction duct 39b and the third strip block 37c is in turn connected to the suction duct 39c. The inlet channels 39a and 39b is the upper end of the water distribution gate 38a and 38b, which is movable in the direction of arrow C, which adjustment can be split dividing 39a and 39b through various incoming water chamber compartments 15a, 15b and 15c. This water division is represented by the arrows Fal / Fa2 and the arrows Fbl / Fb2. By means of the slides 38a, 38b 20, the water is distributed so that the flooding of the chamber purchase 15C does not occur and so that the height H0 of the water surface S is substantially constant in the entire area of the chamber purchase 15C. In this case, drainage channels 14a, 14b, 14c are only required on the drive side of the machine. A fixed trough 38k above the last channel 39c directs the water flow Fc from the strip block 37c to the chamber compartment 15C.

In the embodiment according to Figure 6, the vacuum levels of the strip blocks 47a, 47b and 47c can be controlled by the throttling and flow resistance and / or the channel height of the drainage channels 49a, 49b, 49c by suitably dimensioning and / or positioning.

Particularly preferred is an embodiment of the chamber purchase arrangement according to Fig. 6, in which the flow Fb of the second channel 39b is completely led to the latter compartment 15c, whereby the flow Fbl = 0. The flows Fal and 35 F1 are distributed as described above. Assuming that the drainage capacity of the drainage channels 14a, 14b, 14c is equal to each other, • t 95489 10 then the water is distributed by means of the water distribution slide 38a so that

Fal s Fa2 ~ Fb + Fc-

In the following, the claims are set out, within the scope of the inventive idea defined by them, the various details of the invention may vary and differ from those set forth above by way of example only. 1 i »t nni4 i t ι * ι, ·

Claims (10)

A system of dewatering chambers in a double-wire former, said double-wire former comprising a zone of double-wire, in which is disposed within one of the wire loops (20), a wire loading unit (23) having a system of load rails (26a, 26,26b ) which, most suitably, can be loaded with pressure (Pk) of pressure medium and opposite it a system of dewatering and guide strips (36a, 36b, 36c) inside the second wire loop (10) and in which former one is inside the upper wire loop 10 ( 10) provided dewatering chambers (15A; 15B; 15C; 15D) which are connected to a dewatering channel (14B; 14D) or channels (14a, 14b, 14c) through which one removes water from the web (W ) through the upper wire (10) via the heel cavities (36R) of the strips which act against the inner surface of the upper wire loop (10), and at least the upper part of the system of dewatering chambers (15A; 15B; 15C; 15D). is provided in the form of a uniform suction chamber space with which to feed purifying a negative pressure (p 1) of a negative pressure source (40), characterized in that the dewatering chamber (15A; 15B; 15C; 15D) mentioned below has mold sections (37a, 37b, 37c, 37ai, 37a2), whereby the negative pressure which raises in the various sections and / or the amounts of water that move away from the web (W) through the upper wire (10) via the different sections are arranged to be adjustable or adjustable. 2. A dewatering chamber system according to claim 1, characterized in that a pre-watering chamber (15e) with a deflector (36a) and a suction channel (35a) therefor is provided with said system of chambers and mentioning the pre-watering chamber. (15e) can be combined with its own negative pressure (p0). Drainage chamber system according to claim 1 or 2, characterized in that the lower part of the dewatering chambers (15A; 15C) is divided by walls (16a, 16b) or ducts (30a, 39b) into two or more, most preferably three compartments (15a, 15b, 15c), which compartments are joined by straddling heels (18) and / or dewatering channels 35 (39a, 39b, 39c) with the mold sections (37a, 37b, 37c) below them. •): · β, ϊ MU l, U4 * t: 95489 15 4. A system of dewatering chambers according to claim 3, characterized in that, in one edge of said compartments (15a, 15b, 15c), most preferably in the running direction of the wires (10,20) at the edge of the exit side, there are adjustable throttle heels ( 18), which can be controlled by a rotatable control bar or the corresponding control slides (17a, 17b, 17c) for controlling or adjusting the amounts of water coming to the different compartments (15a, 15b, 15c) of the vacuum levels and / or the dewatering chambers of said list section ( 37a, 37b, 37c) (Figures 1 and 2). 10 Drainage chamber system according to claim 3 or 4, characterized in that, in connection with the wall on the exit side of each compartment (15a, 15b, 15c) of the system (15C) of drainage chambers, there are drainage channels ( 39a, 39b, 39c), of which the first part (s) divides the system (15C) of dewatering chambers into said compartments (15a, 15b, 15c) and that at least in the upper end of said first dewatering channel (39a) connected In the list system (37a) below the first chamber compartment (15a), there is a water distribution slide (38a), with which the mutual distribution (Fal, / Fa2) of the water streams coming into the first and second chamber compartments (15a, 15b) ) can be set or regulated via said channel (39a). 6. A dewatering chamber system according to claim 5, characterized in that the system (15C) of the dewatering chamber comprises a suction space whose upper part is uniform and which is connected to the same vacuum source (px) and the chamber system (15C). is divided into three compartments (15a, 15b, 15c) with said dewatering channels (39a, 39b) and the water quantities coming through the first dewatering channel (39a) are distributed to the first and second chambers (15a, 15b) and via the second dewatering duct (39b) as well as the last dewatering duct (39c), which is connected to the rear wall of the chamber system (15C), is guided to the last compartment (15c) (Figure 6). Drainage chamber system according to any of claims 1-3, characterized in that the entire machine-directed length of the drainage chamber system (15B) is uniform without transverse intermediate walls and that there are two or more drainage chambers under the system (15B). several, most conveniently, three strip sections (37b, 37c, 37d), one end of which, most preferably the exit end, is connected with controllable throttle openings (18b, 18c, 18d) with the internal space of said dewatering chamber system (15B) and the uniform suction space in the upper part of said dewatering chamber system (15B) is associated with a single negative pressure (px) (Figure 5). 8. A system of dewatering chambers according to claim 7, characterized in that on the front side of the chamber system there is a pre-dewatering chamber (15e), which is connected to a separate sub-pressure (p0), that in connection with said forewashing chamber ( 15e), most preferably at the front edge, is a deflector (36a) and a suction deflector channel (35a) which opens above it, that in said pre-drainage chamber (15e) there is a separate dewatering channel (14e) at the operating side of the machine, below said pre-dewatering chamber (15e), there is the first of the mold sections (37a), which is joined by a controllable throttle opening (18a) with the front portion of the unitary chamber (15a), that thereafter under said unitary chamber (15a) there are two or more, most preferably three, strip sections (37b, 37c, 38d), each of which is joined with its own adjustable throttle opening (18b, 18c, 18d) with a uniform chamber (15a) and said unitary comb re (15a) is provided with a dewatering channel (14B) which is located on the operating side of the machine and most preferably extends over the entire machine-directed length. Drainage chamber system according to any one of claims 1-8, characterized in that at the lower end of the chamber system stationary dewatering and guide strips (36) have been attached from the double wire zone, from whose heel cavities (36R) the water removes go to said list section (37). 10. A system of dewatering chambers according to any one of claims 1-9, characterized in that in the area of said chamber, the zone of double wire curved by the loading strips (26) of the st. IK) III II I I t fe · 95489 17 the double wire load unit (23) with a relatively large radius of curvature (R0; R3).