FI120293B - Method and apparatus for controlling the running of an edge band - Google Patents

Description

Method and apparatus for controlling the passage of an edge band

The invention relates to a method of transferring a fibrous web from a forming part of a papermaking machine to a press section, wherein the fibrous web is separated from the fibrous web when it is on a forming wire and the fibrous web is transferred at pick-up to the pressed tin fabric.

The invention also relates to a device for controlling the passage of an edge band after the point of intersection of the edge band 10 before the pick-up point where the fibrous web is transferred from the forming wire to the press section fabric while the edge band remains on the forming wire.

By papermaking machine is used herein to refer to paperboard, tissue, or pulp drying machines. Correspondingly, the fibrous web may be paper, board, soft 15 peri or pulp.

At the end of the forming section at the pick-up point, the fibrous web is transferred from the forming section wire to the fabric of the press section. Before the pick-up point, the edges of the web are cut and only the clean cut web is transferred to the press section. For this purpose, near the pick-up point, edge strip cutting devices, or edge whipers, are provided, through which water jets are applied to the web on the wire. They are used to cut narrow strips, i.e. edge strips, at both edges of the web, thereby providing a flat width and an intact and smooth web at both edges for guiding the press section. The web between the edge strips is separated from the wire by 25 pick-up rolls.

Managing the edge band after the edge cut requires high precision at the pick-up point. US 6214168 B1 discloses a solution in which the edge strips are separated from the web at the pick-up point by utilizing suction boxes 30 operating in the area of the edge strips through which the edge strips are subjected to vacuum. This vacuum ensures that the edge strips follow the wire as the web moves into the fabric of the press member. The problem with this solution is that, especially at high travel speeds, very high precision is required when adjusting the pick-up roll suction zone width, web width, vacuum suction box position and suction box location to properly move the web edge from the forming member to the press section.

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Some forming part solutions further include a suction roller between the edge whip and pick-up area, which removes water through the wire from the web. There is thus a risk that the web and the edge band will become entangled again, making it difficult to transfer the web cleanly to the press member.

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The object of the invention is to improve the handling of the edge strip after the intersection and thereby facilitate the transfer of the web from the forming part to the press part.

The method according to the invention is characterized in that the edge strip is subsequently subjected to an oblique blow through the forming wire, which causes the edge strip to either fold twice or to move sideways away from the cut fibrous web so that the edge strip and distance web are spaced.

Correspondingly, the device according to the invention is characterized in what is stated in the characterizing part of claim 4.

In one embodiment of the invention, the blowing is applied to the curb so as to cause the curb to move laterally away from the fibrous web. This is accomplished, for example, by blowing the blade over the entire width of the bead, so that the bead is detached from the wire and moves away from the web, i.e. closer to the outer edge of the wire, in the direction determined by the blow.

In another embodiment of the invention, the blowing is applied to the bead 30 so as to cause the bead to fold twice. This is achieved, for example, by directing the blowing only or mainly to the web-side edge of the web, whereby the outer edge of the web remains attached to the wire.

When the distance between the edge band and the fibrous web is sufficiently large as the web enters the pick-up position 5, the fibrous web is more easily detached from the forming wire and transferred to the fabric of the press member. In this case, the pick-up roll suction area can be selected as wide or even larger than the fibrous web without the risk of the edge strip following the web and causing interference with the press member. In addition, the web edge no longer tends to elongate during transfer, since the edge band is already separated from it even before the pick-up point.

The invention will now be described with reference to the figures in the accompanying drawings, which, however, are not intended to be limited thereto.

Fig. 1 is a side view of a two-wire forming machine having an edge section two after the wire zone before the pick-up point.

Fig. 2 is a side elevation view of a two-wire reformer having a suction roll between the edge cut and the pick-up point.

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Figure 3 is a cross-sectional view of the web at the intersection of the edge strip.

Figure 4 is a cross-sectional view of the first embodiment of the invention in which the edge band is blown sideways.

Fig. 5 is a cross-sectional view of another embodiment of the invention in which the edge band is inflated by a twofold step.

Figure 6 shows a top view of an embodiment in which the edge band is moved to the side.

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Figure 7 shows a top view of an embodiment where the edge band is folded twice.

Figure 1 shows a two-wire reformer in which a pulp suspension is fed between a first-wire 1 and a second wire 2 to form a forming spit 3. Thereafter, the wires 1,2 are curved over the suction sector 5 of forming roll 4 through the second wire 2 outwards. After the forming roll 4, within the first wire loop 1, there is a dewatering box 6 provided with a vacuum and 10 dewatering strips controlling the passage of the wire 1. Within the second wire loop 2 is a plurality of loading strips 7 which are arranged so that they fall between the dewatering strips on the lid of the drainage box 6. The preloading strip 8 is disposed within the second wire loop 2 prior to the dewatering box 6 and the actual loading strips 7. The common, substantially vertical run 15 of the wires 1, 2 ends with a suction roll 9 with wires 1, 2 curved over the suction sector 10. After the suction roll 9, the web W moves forward supported by the second wire 2 to the pick-up point P, where the web W is moved by the pick-up roll 11 to the fabric 12 of the press section.

The cutting of the edges of the web W is accomplished by running at the lower wire of the second wire 2 between the suction roll 9 and the pick-up point P. Above the web W, an edge whip 13 is provided at each edge of the web, from which a water jet 13a is applied against the web 2 of the wire 2, which separates a narrow strip or edge strip from the web W. Below the wire 2, there is a vacuum 14 at the corresponding position, which receives the spillage penetrating through the wire 2 25. The solution according to the invention further comprises one or more blow nozzles 15 arranged to blow air through the wire 2, as will be described later. The purpose of the blow nozzles 15 is to widen the gap between the edge band and the web before transferring the web to the puris section.

At the pick-up point P, only the cut web W is transferred to the fabric 12 of the press member while the ribbon S remains on the wire 2, from which it is subsequently guided to the pulper (not shown). This is accomplished, for example, by tracking the inside of the second wire loop 2 at the pick-up roll 11 by the edge strip suction boxes 18 that hold the edge web S in the wire 2 as the web W moves to the press section 12 under vacuum in the pick-up roll 11. The suction width of the suction boxes 18 of the edge band 5 extends substantially only to the width of the edge band S.

Fig. 2 shows an alternative structure of the remainder of the two-wire reformer. 1. At the end of the forming section, inside the second wire loop 2 is a suction roll 16 which is positioned 10 after the edge whips 13 before the pick-up point P, where the web W is transferred from the wire 2 to the fabric 12 of the press section. the function is to increase the solids content of the web W before transferring it to the press section. The suction roll 16 disposed after the edge whips 13 can normally cause the edge band to re-adhere to the edge of the web, thereby making it difficult to transfer the web to the press member. In the solution 15 according to the invention this can be avoided by moving the edge strip by one or more pu nozzles 15 apart from the cut web before the suction roll 16.

Figures 3-5 show a cross-sectional view of the web at the edge 13 and the blow nozzles 15 of the wire 2 and the web W on its surface.

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Figure 3 shows the initial situation at the edge whip 13 before the action of the blow nozzles 15 begins. From the nozzle opening of the edge whip 13, a water jet 13a is directed obliquely past the web W, which creates a narrow cut groove G on the surface of the web W separating the edge strip S and the web W. Below the wire 2, there are shown blowing nozzles 15 which are arranged only after the cutting point so that their effect does not extend to the cutting point.

FIG. the distance d increases,

Fig. 5 shows an alternative solution in which compressed air is blown obliquely towards the edge band S from the blower nozzle 15 below the wire 2 so that the edge band S is folded twice. Also in this case, the distance d between the web W and the edge strip S increases, which facilitates the transfer of the web W to the press section. With a clear gap between the web W and the edge strip S, the suction zone of the pick-up roll can be extended over the entire width of the web and, if necessary, slightly over it.

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Cutting the edge band by means of a water jet easily results in that the web W and the edge band S adhere more closely to the wire 2 in the area of the cutting groove G than elsewhere. The blowing through the wire 2 can be aligned while at the same time removing the edge of the web W from the wire 2.

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Figure 6 is a top plan view of the solution of Figure 4. The arrow 13a illustrates a water jet directed towards the outer edge of the web obliquely towards the outer edge of the web W, which provides a cutting groove G. Due to the blows 15a, the distance d between the edge strip S and the web W grows larger than the original width of the cutting groove G.

Figure 7 is a top plan view of the solution of Figure 5. Arrows 25 15a illustrate air blows which are inclined obliquely towards edge band S

heading and outer edge. This time, the blows 15a are arranged to fold the edge band S twice. The desired effect is achieved either by using only one blow 15a or by staggering the blows 15a so that the blowing power closest to the shear groove G is the highest and the blowing power decreases as the farther away from the shear groove G.

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Many variations of the invention are possible within the scope defined by the following claims.

Claims (5)

A method of transferring a fibrous web from a forming portion to a pressing portion of a paper machine, in the method of operation, an edge band (S) is separated from the fibrous web (W) while on a forming web (2) and the fibrous web ( W) is transferred to a tissue (12) in the press portion at a pick-up location (P) while the edge web (S) remains on the forming wire (2), characterized in that the edge band (S) after the separation of the edge band (S) is subjected to an oblique through the lining wire (2) directed blow (15a) which causes the edge band (S) to either fold twice or move laterally further away from the cut fiber web (W) in such a manner that the distance ( d) grows between the edge band (S) and the fiber web (W). 2. A method according to claim 1, characterized in that the blow (15a) is directed so that it simultaneously detaches the edge of the web (W) from the forming wire (2). 15 Method according to claim 1 or 2, characterized in that the area of the fiber web (W) at the pick-up site (P) is subjected to a first subpressure through the web (12) in the pressing section, which suppresses the fiber web (W). from the forming wire (2) on the tissue (12) in the press section, and the area of the edge band (S) is simultaneously exposed to a second negative pressure through the forming wire (2), which pressure adheres the edge band (S) to the forming wire (2). Apparatus for controlling the running of an edge band (S) after a location for cutting the edge band (S) before a pick-up location (P) where a fiber web (W) is transferred from a forming wire (2) to a tissue (12) in a pressing portion while the edge band (S) remains on the forming wire (2), characterized in that the device comprises blowing means (15) for blowing lute through the forming wire (2) obliquely against the edge band (S) so that the blowing (15a) the edge band (S) causes either to fold twice or move laterally further away from the fiber web (W) in such a way that the distance (d) between the edge band (S) and the fiber web (W) grows. 5. Apparatus according to claim 4, characterized in that the blowing means comprises one or more blowing nozzles (15).