FI104576B - Arrangements to reduce the overpressure in the pick-up space of the web between a mold and a press section in a paper or cardboard machine - Google Patents

Description

104576 Arrangement for Relieving Overpressure at a Pick-up Point Between the Former and Pressing Part of a Paper or Cardboard Machine 5 Pick-up Stack of a Cardboard Mask 10 The invention relates to the preamble of claim 1. a defined arrangement for reducing overpressure at the web pick-up point between the former and the press portion of the paper or board machine.

In prior art solutions in which the formed web is transferred from the former inner wire to the press-pick pick-up fabric, there is a strong blow in the pick-up nip between the pick-up roller and the inner wire that dirts the pick-up area and edges while damaging the paper runnability. This blowing is mainly due to the air carried by the pick-up tissue and the wire-tissue pick-up nip 20.

The main features of the arrangement according to the invention are set forth in the characterizing part of claim 1.

,,, 25 The invention is based on the fact that the exterior of the two-wire part of the former. the wire guide roll and the pick-up fabric guide roll of the press section are arranged in close proximity. An adequate «· · I ♦ · | is provided for the pick-up tissue <* wrap angle around pick-up tissue guide roller to remove air carried by pick-up fabric due to centrifugal force pick-up IM * · · * 30 fabrics in pick-up fabric guide roller for pick-up fabric the air carried by it will not pass to the pick-up point. By arranging • · additionally, the passage of the pick-up tissue and the outer fabric is suitably accomplished: ί: a situation in which the outer fabric pumps air from the pick-up site, whereby pick-up. up pressure is reduced and carried by the inner wire to the pick-up • ·. 35 air volume decreases. In this case, the pick-up point and the edge whistles remain in place, which results in fewer breaks and improved machine efficiency.

·! J The reduction in overpressure at the pick-up also has a beneficial effect on the transfer of the web from the wire section to the press section. The web can be better tracked on the pick-up fabric.

In prior art constructions, the amount of air I passing to the pick-up nipple 5 is obtained by assuming a machine width of 10 m, a machine speed of 2000 m / min, and a 100 mm air layer passing through the inner fabric and pick-up fabric as follows: I = 0 , 1 mx 10 mx 33 m / sx 2 = 66 m3 / s.

10

There is thus a considerable amount of air, which causes the pick-up area to become dirty and contaminated.

In the following, the invention will be described with reference to the accompanying drawings, which are not intended to be limited solely by the scope of the invention.

Fig. 1 is a diagrammatic view of a solution of a former-press part applying an arrangement according to the invention.

20

Figure 2 is an enlarged view of the coupling between the former and the press member shown in Figure 1.

Figure 3 shows a modification of the solution of Figure 2.

25th · ·; Figure 4 shows another modification of the solution of Figure 2.

Fig. 5 shows a third modification of the solution of Fig. 2.

Fig. 6 shows an embodiment of the invention with a pick-up

i · I

'The tissue is thrown.

i ♦ · I 1 · «1 ·

Figure 7 shows an alternative embodiment of the invention. - •

I «I M

• I

1 shows a left-handed two-wire former comprising an outer wire 10 guided by a guide roller 12 and an inner wire 20 guided by a guide roller 22 from which the formed web W is removed by the pickup fabric 30 of the press member. The mold comprises a forming bar G to which a pulp suspension jet J is fed from the lip opening of the headbox. The forming gap G is defined between the forming roll 11 provided with the vacuum zone 11a 5 inside the outer wire loop 10 and the chest roll 21 inside the inner wire loop 20. Between the outer wire 10 and the inner wire 20, after the forming bar G, an upwardly running double-wire zone A is formed. The double-wire zone A terminates at the suction zone 23a of the pivoting suction roll 23 inside the inner wire loop 20.

10 At the suction side 23a of the suction zone 23a of the pivoting suction roll 23, the outer wire 10 diverges from the inner wire 20 and runs back to the forming roll 11 guided by the outer wire 10 following the reverse wire 10 and the other wire 10 12

15 reversing the vacuum zone 23a after 23 trailing the web W follows the inner wire 20, from which the web W is detached from the inner wire 20 and the pick-up roll 31 between the pick-up point N0. Removal of web W from inner fabric 20 is effected by a vacuum zone 31a of pick-up roll 31 which also engages web W 20 in pick-up fabric 30. The pick-up point N0 is located on a downwardly sloping run B between inner fabric 20 said inner wire 20; near the guide roll 22 '. A guide roll 22 '* of said inner wire 20; *; thereafter, the inner wire 20, guided by the guide rolls 22, runs back to the chest roll 25. The rotation direction of the outer wire 10 is indicated by the reference marks · · ·: S10 and the rotation direction of the inner wire 20 is denoted by reference numeral S · n.

The pick-up fabric 30 of the press member passes after the pick-up roll 31 to a first press nip c formed by the press roll 33 and the counter roll 43. · · · *. *. * Nlf, after which the pick-up fabric 30, guided by the guide rollers 32, moves into the return cycle. When web W is adhered to pick-up fabric 30 in pick-up roll 31 in suction zone 31a, web W is moved, supported by pick-up fabric 30, to first press nip N1 (through which web W passes · · 35 upper pick-up fabric 30 and below press fabric) The directions of rotation of the pick-up fabric 30 are denoted by the reference numeral S30 and the direction of rotation of the press fabric 40 is denoted by the reference numeral S40, respectively.

Figure 1 also shows a dashed line 5 of the prior art solution wherein pick-up fabric 30 'passes directly from lead-roll 32' of pick-up fabric 30 'to pick-up roll 31 of said pick-up fabric 30'. the air conveyed by the up fabric 30 'and the bottom fabric 20 is directly transported to the pick-up nip N0, creating overpressure in the pick-up nip N0 and contaminating the periphery and edge whips of the pick-up nip N0.

Fig. 2 is an enlarged view of the coupling between the former and the press member of Fig. 1, which illustrates the solution of the invention more clearly. The solution of the invention is based on preventing airflow I3 carried by the pick-up tissue 15 30 from entering the pick-up point N0 and removing the air in front of the pick-up point N0. This can be achieved by satisfying the following three conditions:

According to the first condition, the shortest distance (d) between the outer surface (30a) of the pick-up fabric (30) and the rotating suction rolls (23) in the rotational direction (S10) of the outer wire (10) is less than 300 mm.

According to another condition, the rotating suction rolls 23 in the direction of rotation S10 of the outer wire 10. . The tangent plane Tx between the first outer peripheral half 12 'of the next outer wire 10 first guide roll 12' and the first peripheral half of the pick-up fabric 30 'preceding the pick-up roll 31 and the angle of inclination α between the horizontal plane VT is in the range α = 0 ° to 80 °, more preferably in the range α = 0 ° to 60 °.

30 • · • · ·

The third condition is that the pick-up rolls 31 pick-up fabrics 30

Mt ·. · 1 in pin S30 the extension C3 of the run C3 of the first lead roll 32 'of the preceding pick-up fabric 30 and the lead roll 32' 'of the prior pick-up fabric 30' cuts the pivoting suction roll 23 in the direction of rotation of the outer wire 10 first guide roll 12 '• · 1 • ·

to the center of the axis M12, the vertical axis PT drawn on the axis

1 · • · 5 at 104576 at P1 (located above or in line with the intersection P0 of the outer periphery of the first guide roll 12 'of the first wire roll 12' of the outer wire 10.

It is further advantageous in the invention that the wrapping angle β of the pick-up fabric 30 on the first guide roll 32 'of the pick-up fabric 30 preceding the pick-up roll 31 is greater than 45 ° and preferably greater than 90 °.

The free distance d between the outer surface 30a of the pick-up fabric 30 and the outer conductor 12 'of the first guide roll 12' of the outer wire 10 following the pivot suction roll 23 provides an appropriately wide channel for pumping air I2 from the inner wire 20 from the triangular space 50 delimited by the pick-up fabric 30. In this way, the overpressure generated in said space 50 is reduced, so that the inner fabric 20 does not convey to the pick-up nipple N0 to any appreciable extent.

The inclination angle α of the tangent plane TL 20 between the first surfaces of the first guide roll 32 'of the pick-up fabric 30 and the first guide roll 12' of the outer wire 10 ensures that the respective positions of the first guide roll 32 'of the pick-up fabric 30 The uppermost point of the outer periphery of the first guide roll 32 'of the pick-up fabric 30 must be located at least on the same horizontal plane as the outer periphery of the first guide roll 12' of the outer wire 10; 25 top points to allow the airflow carried by the pick-up tissue 30 • • · • · *. . the backing I2 is not deflected too far down on the outer circumference of the first guide roll 12 'of the outer wire 10 where it could prevent the outer wire 10 from pumping air from the space 50 in front of the pick-up nip N0. On the other hand, the earth guide roll 32 'must not be too high with respect to the first lead roll 12' of the outer wire 30 10 so that the pick-up fabric 30 will not collect air again on the first lead roll of the pick-up fabric 30. 32 'and • · · · between the first conductor roll 12' of the outer wire 10.

·

Pick-up fabric 30 pick-up rolls 31 first leading guide rolls • ·. 35 * C * of the pick-up fabric between the 32 'and the second second guide roll 32' 'and extends Cx of the run C of the run and the suction roll 23 of the outer wire 10 »· • * * 6 104576 to the center point M12 of the first guide roll 12' the position of the intersection point Pj ensures that the direction of said run C of the pick-up fabric 30 is such that the flow of air I2 5 carried by the pick-up fabric 30 is not too downwardly directed to the outer circumference of the first guide roll 12 ' air from space 50 in front of pick-up nipple N0.

With a sufficiently large wrap angle angle β, it is intended that the airflow carried by the pick-up 10 fabric 30 is detached from the surface of the pick-up fabric 30 by centrifugal force when the direction of travel of the pick-up fabric 30 is reversed to the first guide roll 32 'of the pick-up fabric 30. This ensures that the airflow I3 carried by the pick-up tissue 30 cannot pass into the pick-up nipple N0.

15

In the situation of Fig. 2, the extension Cx of the pickup fabric 30 between the first guide roll 32 'and the second guide roll 32' preceding the pick-up roll 30 coincides with the first guide roll 12 'of the outer wire 10 following the swivel suction 23 and for the run D of the outer wire 10 "between the guide roll 12" at a point P2 spaced from the point where the outer wire 10 is separated from the first guide wire 12 'of the outer wire 10 following the pivot suction roll 23. In this way, an advantageous situation is obtained in which the airflow IL carried by the pick-up fabric 30 is directed over the run D of said outer wire 10, from which it is carried away by the outer wire 10.

IM f • «• · · • · · ·. . Fig. 3 shows a situation corresponding to that of Fig. 2, except for the pick-up roll 31 in the direction of rotation S30 of the pick-up fabric 30 • · · · · ·

* run C of first pick-up roll 32 'of upstream pick-up fabric 30 and run 30 C of second pick-up roll 32' of upstream pick-up roll 30

• · • · · *. *. * Direction. In the situation of Figure 2, the direction of the run C of said pick-up fabric 30 is such that the extension C3 of said run cuts the outer wire 10 at a point P2 located in the first guide roll of the outer wire 10 following the rotation suction roll 23 of the outer wire 10. 12 '• «. Between the 35 and the second second guide roll 12 '', the outer wire 10 runs • «·

melt D. In the situation of Figure 3, run 30 C of said pick-up tissue

7 10 76 kyse 10 kyse 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 10 However, the invention works well in this situation as well. Here, the airflow I3 carried by the pick-up tissue 30 is directed above the outer wire 10 and the outer wire 10 pumps the air I2 in front of the pick-up point N0 and 5 further transports it out of the pick-up position N0.

Fig. 4 shows a situation in which the first guide roll 32 'of the pick up fabric 30 preceding the pick-up roll 31 in the direction of rotation S30 of the pick-up fabric 30 is lower relative to the situation of Fig. 2 relative to the first guide roll 12' of the outer wire 10. In the situation of Figure 4, the extension C3 of the run C between the first guide roll 32 'and the second lead roll 32' 'of the pick-up roll 30 before the pick-up roll 31 hits the center of the axis of the first lead roll 12' of the outer wire 10 a vertical plane PT at the point Pj which intersects the intersection P0 of said vertical plane PT and the upper half of the outer periphery of the first guide roll 12 'of the outer wire 10. The airflow Ix carried by the pick-up fabric 30 is directed onto the outer fabric where it mixes with the airflow I2 pumped from the front of the pick-up point N0 of the pick-up wire 10 and passes away from the pick-up position N0 as the air flow I3. If you pick-up tissue 30, said run C extension

Cj would hit said vertical plane PT below said point P0, the airflow I3 carried by the pick-up fabric 30 would be deflected too far down on the circumference of the first guide roll 12 'of the outer wire 10, whereby the outer wire 10'. Pumping 25 ran air I2 from space in front of pick-up nipple N0 50 flashing «· * ·; riintyisi.

• M • * • · • · · I I »

Figure 5 illustrates a kind of extreme case in which the highest point 1 2 3 4 5 6 of the first guide roll 12 'of the outer wire 10 following the pivot suction roll 23 is on the same horizontal plane as the pick-up fabric preceding the pick-up roll 31. '· * ·' The highest point of the outer circumference of its first 30 guide rollers 32 '. The angle α of the tangent plane T3 and the horizontal plane VT between the first conductor roll 12 'of the outer wire 10 2 and the first conductive wire 4'; 4 of the pick-up fabric 30 'in this embodiment is 0 °. . Pick-up roll 31 The pick-up fabric 30 between the first guide roll 32 'of the preceding pick-up fabric 30 and the second guide roll 32' of the preceding pick-up roll 30 has a run C of 104576 also horizontally, whereby the elongation Cx of said pick-up fabric 30 runs into the inlet point M12 of the first guide roll 12 'of the outer wire 10 following the pivot suction roll 23, at a vertical plane PT at P1 to the intersection P0 of the upper half.

The airflow 1I carried by the pick-up fabric 30 is directed to the outer fabric 10 where it joins the airflow I2 pumped in front of the pick-up nip N0 of the outer fabric 10 and passes away from the pick-up position N0 as the airflow I3. If the first 10 guide rolls 32 'of the pick-up fabric 30 are lowered further relative to the first guide roll 12' of the outer fabric 10, the airflow I3 carried by the pick-up fabric 30 interferes with the pumping of the outer fabric 10 without I2

Fig. 6 shows a situation in which the pick-up fabric 30 is a so-called throw, i.e. a substantially water-impermeable transfer belt. Here, the pick-up nip N0 is formed at the end of the former double-wire zone A between the pivoting suction roll 23 within the inner wire loop 20 and the pick-up roll 31. The diameter of the pivoting suction roll 23 is relatively large relative to the diameter of the roll 31 of the pick-up roll 20 and the pick-up nip N0 also acts as a so-called pre-compression nipple, where water W is pressed through the inner wire 10 into the suction zone 23a. The pick-up roller 31 is preferably a flat-bottomed roller with a closed shell. The invention can also be well applied to such a structure by providing a pick-up fabric before the first guide roll 12 'of the outer wire 10 25 and before the pick-up roll 31'. conveniently located between its first 30 guide rollers 32 '. As the first press nipple of the • M «· cross member, NL is the shoe press nip here.

Fig. 7 shows a situation in which an intermediate roll 34 is disposed between the pick-up roll 31 and the first guide roll 32 'of the pick-up box 30'.

The operation of the invention is not affected by such an intermediate roll 34 per se, and the intermediate rolls 34 may, if desired, be provided with a plurality of pick-up rolls 31 and a first guide roll 32 of the pickup fabric 30 '. if it is deemed necessary. Placing the intermediate roll 34 or the intermediate rolls between the narrow • 35 may be problematic, but the invention will naturally work in such a situation. The first guide roll of pick-up fabric 30 · · 9 104576 32 'is also in this situation the guide roll of pick-up fabric 30 whose position relative to the first guide roll 12' of outer wire 10 must meet the requirements of the above invention.

The arrangements of the invention described above provide a situation in which the airflow Ix carried by the pick-up tissue 30 cannot reach the pick-up position N0. Said airflow Ix is guided at the outer surface of outer wire 10 by pick-up fabric 30 on outer surface of outer wire 10 by rotating suction roll 23 in outer thread 10 of outer wire 10 following first outer wire 10 'and subsequent outer wire 10'. D above. The outer fabric 10 further pumps air I2 from the space limited by the pick-up fabric 30 and the inner fabric 20 in front of the pick-up point N0. The overpressure 15 in front of said pick-up point N0 can thus be reduced and, under most favorable conditions, a negative pressure can be generated in front of the pick-up point N0.

In Figs. 1-7, the first guide roll 32 'of the pick-up fabric 30 and the first guide roll 12' of the outer fabric 10 are drawn substantially the same size, but the invention is not limited to such an embodiment; the diameters of the rolls 12 'and 32' may also be different.

Furthermore, the invention is in no way limited to the former as shown in Fig. 1 or to the .25 press member as shown in Fig. 1 or Fig. 6.

«· · · 1 1 · · · · · · ·

The pick-up fabric 30 may be a press felt, a transfer belt substantially impermeable to water, i.e. a so-called toss or the like.

The following claims, which, within the scope of the inventive concept, define the details of the invention, may vary.

• I I

· .1 1 above by way of example only.

«· · · V · <· ·

Claims (7)

10 104576 An arrangement for relieving overpressure at a pick-up point (N0) of a web (W) between the former and a press section of a paper or board machine, comprising a outer wire loop (10) and an inner wire loop (20) forming dewatering zone (A) at the end of the two-wire zone (A), the outer wire (10) is separated from the web (W) and guided to the first guide roll (12 ') of the outer wire (10) and the formed web (W) is followed by the inner wire (20) a press portion for pick-up fabric (30) in a pick-up nip (N0) between the pick-up roll (31) and the roll (23) within the inner wire (20) or the inner wire loop (20), characterized in that the arrangement: 30) the shortest distance (d) between the outer surface (30a) and the outer periphery (10) of the first guide roll (12 ') of the outer wire (10), the upper peripheral half of the first guide roll (12') of the outer wire (10) up ku the pitch (α) between the upper peripheral half of the first guide roll (32 ') of the first guide roll (32') and the horizontal plane (VT) of the dock (30) is less than 80 °, and the first guide roll (32 ') of the pick-up fabric (30); the extension (C ^) of the run (C) between the second guide roll (32 ') of the preceding pick-up fabric (30) cuts the center wire (M12) drawn on the outer wire (10) of the lead roll (12'). ! 25 at the point (Px) on the vertical axis (PT) at I · · ·, ·. : see vertical (PT) and outer wire (10) first guide roll • · · • ·. · (12 ') above or at the point of intersection of the upper peripheral half (P0), whereby the flow of air (Ij) carried by the pick-up tissue (30) does not pass to the pick-up position (N0) but is released by centrifugal force from the surface of the pick-up fabric (30) during the pivoting of the pick-up fabric (30) at the first guide roll (30 ') of the pick-up fabric (30) and the pick-up fabric (30). up pressure (N0) that normally builds up can be reduced as the outer wire (10) pumps air (I2) out of the inner wire (20) and pick-up • m. 35 of the tissue (30) confined space (50) in front of the pick-up point (N0). · · · • • • • • t · • · ♦ * * • · 11 104576 An arrangement according to claim 1, characterized in that said pitch angle (a) is less than 60 °. Arrangement according to Claim 1 or 2, characterized in that the wrapping angle (β) of the pick-up fabric (30) on the first guide roll (32 ') of the pick-up fabric (30) is greater than 45 °. Arrangement according to claim 1 or 2, characterized in that the wrapping angle (β) of the pick-up fabric (30) on the first guide roll (32 ') of the pick-up fabric (30) is greater than 90 °. Arrangement according to one of claims 1 to 4, characterized in that the pick-up fabric (30) between the first guide roll (32 ') of the pick-up fabric (30) and the second guide roll (32' ') of the pick-up fabric (30). the extension (0Χ) of the run (C) intersects the outer wire (10), the first lead roll (12 ') of the outer wire (10) and the second lead roll (12' ') of the subsequent wire (10) at the point (D) P2) spaced from the intersection (P0) of the vertical plane (PT) drawn on the center of the axis (M12,) of the first guide roll (12 ') of the outer wire (10) and the upper outer half of the outer wire (10). Arrangement according to one of Claims 1 to 5, characterized in that the first guide roll (32 ') of the pick-up fabric (30) is a guide roll (S30) preceding the pick-up roll (31) in the direction of rotation (S30) of the pick-up fabric (30). 32 '). f I »· • • · · • f · • · Arrangement according to one of Claims 1 to 5, characterized in that: • · t • fl m ···, between the pick-up roll (31) and the first guide roll ff · (32 ′) of the pick-up fabric (30) one or more intermediate rollers (34). 30 • • • il • • • • • • Ml 12 104576