FI72162B - FOERFARANDE FOER LEDANDE AV BANAN TILL TORKPARTIET I EN PAPPERSMASKIN - Google Patents

Description

Method for conducting a web of paper ^ ^ _,. . „7 2162 koneen drying unit Part of the ledger for the taps of the paperclip 5

The invention relates to a method for guiding a web from the center roll of a press section or the like to a drying section of a paper machine using drying cylinders and / or rolls, in which the web 10 is transferred against which the web is to be removed from the roll and passing a transfer fabric through a transfer nip between said transfer roll and said smooth surface press roll and transferring and gripping the web in said transfer roll suction zone to said transfer fabric and holding the web with said transfer fabric said transfer fabric and the web associated therewith are passed over one or more drying cylinders and the web is further passed through a so-called as a single fabric export to the subsequent drying cylinders of the drying section.

As is already known, the guiding of the web from the press part of the paper machine generally takes place in the so-called with an open draw, in which the web becomes stretched by about 2%, whereby the web weakens and tapers accordingly. The above-mentioned export of the web takes place, for example, from a smooth-surfaced design of the applicant's "Sym-Press" press section, taking advantage of the guide roll and the speed difference which produces said tension.

30 Some closed export arrangements are also known, but they have had their own shortcomings, so that they have not been widely used.

With regard to the state of the art related to the invention, reference is made to the applicant's FI publications 35,148 and 53,333, DE-OS 2,365,438 and U.S. Patent 2,350,019.

2 72162

As paper machine speeds increase and due to the single wire export of the drying section, the web export from the press section to the dryer section has formed a kind of bottleneck, so that there is a need to develop this web export site more securely so as to reduce the risk of breaks. Another goal is to reduce the which measure has a positive effect on the runnability of the web also in the case of the traction caused by the speed difference. the part of the machine after the paragraph as well as the final performance of the paper.

The object of the present invention is to avoid the above-mentioned drawbacks and to provide an export arrangement in which the traction can be substantially reduced, e.g. to the order of about 0.5%.

In order to achieve the objectives set out above and which will become apparent later, the invention is mainly characterized in that in the method the web is transferred from said transfer fabric to the so-called for a single export fabric by pressing the web against the surface of the drying cylinder with said transfer fabric and conducting said so-called a single take-up fabric over the latter drying cylinder in a particular sector such that the latter drying cylinder-20 blade, in connection with which the transfer from one fabric to another takes place, is located outside the loops of both said fabrics.

According to the starting point of the invention, a central roll of the press part, such as a smooth-faced design, is used against a transfer suction roll, which is pressed against the central roll with a suitable relatively low line pressure. In this transfer suction roll, a vacuum zone or zones are used in which a suitable vacuum is used at the transfer nip and a vacuum lower than said vacuum in the subsequent holding zone.

30

According to a preferred embodiment of the invention, the transfer fabric acts as an export fabric in the first smaller pre-group formed by the drying cylinders, e.g. with 2 to 6 cylinders.

The homogeneous fabric is preferably a homogeneous endless fabric loop that is felt-like and sufficiently permeable for cleaning. In the past, some of these closed export systems 3 72162 have failed due to difficulties in cleaning the transplant tissue.

When the loop of the transfer tissue is made relatively short, its replacement is relatively easy and quick, which is quite important in practice.

5

In any case, the invention advantageously achieves a short and fast transfer, whereby the objects of the invention are realized.

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

Fig. 1 is a schematic side view of a closed web delivery arrangement according to the invention using a transfer fabric operating on a pre-cylinder group of the drying section, the lower cylinders of which are suction cylinders.

Figure 2 shows a variation of the invention in which the transfer fabric comprises only two drying cylinders, the first of which is a suction cylinder.

Figure 3 shows an arrangement according to the invention, in which the transfer fabric adjoins only one cylinder of the drying section, which is the first cylinder in the top row.

According to Figures 1, 2 and 3, the press word is the so-called A "Sym-Press" press section in which the web W is introduced by a pick-up fabric into 13 press sections. The first nip of the press section is formed between the hollow surface roll 10 and the suction roll 11 provided with the suction belt 30. The suction roll 11 forms a second press nip with a central roll 14 provided with a smooth surface 14 of the press. The central roll 14 is e.g. The central roll 14 forms a third nip with the on-surface press roll 15. The first nip N 2 is double felt, including a lower fabric 12 and said 35 pick-up fabric 13, which also acts as a press fabric in the second nip N 1. After the nip, the web W separates from the fabric 13 and follows the center roll 14 adhered to the smooth surface 14 '. The third nip is provided with its own press fabric. The guide rollers 17 guide the fabric 16.

According to the invention, a transfer suction roll 20 is arranged in connection with the central roll 14, which forms a transfer nip Ng with the central roll 14 of the press section.

5 According to the figures, the transfer nip Ng is placed below the horizontal plane set through the central axis of the central roll 14 by an angle α 1, α 2 or ° 3. The magnitude of the angles is preferably about 20 ° ... 50 °. The transfer via the nip Ng is derived from a special transfer fabric 19 selected for this purpose, which is a homogeneous endless felt-like fabric 10 which is sufficiently permeable for cleaning.

The transfer suction roll 20 has two successive vacuum zones 20a and 206. The vacuum zone 20a is at the transfer nip Ng and the prevailing vacuum is preferably of the order of about 30 kPa. Under the reduced pressure prevailing in the zone 20a, the web W is detached from the smooth surface 14 'of the central roll 14 and the web W is adhered to the surface of the transfer fabric 19. The suction zone 20a is considerably smaller than said vacuum, and this zone 203 is a kind of holding zone which ensures that the web W remains on the surface of the transfer fabric 19 as the fabric 19 20 changes direction in the sector of the transfer suction roll 20.

According to Figure 1, the transfer fabric 19 acts as an export fabric in a first pre-group of drying cylinders comprising cylinders 21, 22 and 23. The lower cylinders 21 and 22 are suction cylinders and are provided with a suction zone 21a, respectively. 23α, which zones extend to the sector where the transfer tissue 19 and the web W are adjacent to the cylinder. The upper cylinders 22 are normal smooth-surfaced, steam-heated drying cylinders. The vacuum under the suction zones 21a, 23a of said suction cylinders 21 and 23 ensures that the web W remains on the outer surface 30 of the transfer fabric 19. In the upper cylinders 22, the web W is in the compression between the cylinder surface and the fabric 19.

With the latter cylinder 22, the web W is transferred to the so-called to a fabric 24 providing a "single felt export" which, from one row of cylinders to another knee 35, carries the web W forward as is known per se.

According to Figure 1, the transfer rolls 19 are guided by guide rollers 18, of which 5 72162 rolls 18 'are provided with a blowing zone for cleaning and drying the transfer fabric 19. Rehabilitation devices 33 are arranged for the horizontal flow of the transfer tissue 19, in connection with which spray devices 34 are used to clean the transfer tissue 19.

5

According to Fig. 2, the transfer fabric 19 only bypasses the lower cylinder 21 provided with the vacuum zone 21a and the upper cylinder 22, which is a normal smooth-surfaced drying cylinder. With the cylinder 22, the web W is transferred to the fabric 24, which carries the web W forward, as is known per se.

According to Figure 3, the web W is transferred by a transfer fabric 19 to a drying cylinder 25, on the surface of which the fabric 19 presses the web W. An export fabric 35 is introduced into the cylinder 25, by means of which the web W is transferred. According to Fig. 3 15, the first lower cylinder 26 is provided with a hollow surface 26 'and in connection with this cylinder 26 there is a support fabric 31 guided by the guide rollers 30. The backing fabric 31 ensures that the web W remains on the fabric 35 in connection with the cylinders 26,28, etc.

20 of the fabric 35 and the cylinders 26 and 28 between the inlet side is arranged kitoihin suction 32 with which the wedge spaces between the fabric 35 and the air is sucked into said cylinders so as to reduce these spaces otherwise pathogen-inducible pressure which tends to detach the web W from the fabric 35.

25

According to the invention, the first group of drying cylinders is as low as possible and is positioned relative to the press section so as to provide the shortest and fastest possible continuously supported transfer of the web W.

One advantage of using the transfer suction roll 20 according to the invention and the transfer nip N formed by it is that the line pressure of the transfer nip N partially compensates for the nips and line pressures associated with the embodiment 14 and thus lightens the load on the embodiment 14. The line pressure of the transfer nip Ng is generally 5 ... 20 kN / m, preferably about 10 ... 15 kN / m. When the loop of the transfer tissue 19 according to the invention is relatively short, it is relatively easy to change.

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The transfer fabric 19 is the above-mentioned special fabric, in connection with which blowing-based felt restoration is preferably used, which is easy to arrange inside the hood of the drying section.

5 As stated earlier, traction is used in open exports, where the web is stretched by about 2%. In the application of the invention, the speed of the transfer fabric 19 can be adjusted to be only about 0.5% ... 1% higher than the circumferential speed of the press roll 14.

After the web W has been transferred according to the invention by the transfer fabric 19 to a drying cylinder or a similar roll, the web is continuously guided with the support of the so-called with one felt export still. Said single felt export is used at least at the beginning of the drying section, where the web is even weaker and thus more prone to breakage. As shown in Fig. 15 3, in addition to the single felt outlet, additional fabrics 31 or the like can also be used to support the passage of the web and / or to press it against the surface of the drying cylinder to enhance drying.

The following are claims within the scope of which the various details of the invention may vary within the scope of the inventive idea.

Il

Claims (8)

7 72162 1 Claims A method of guiding a web (W) from a central roll (14) of a press section or a similar drying section of a paper machine using drying cylinders (21,22,23,25,26,27,28) and / or similar rolls, wherein the web (W) ) is transferred as a closed export without open drawing from the press section to the drying section, in which method a transfer nip (N) is formed by pressing the transfer suction roll (20) with a suitable line pressure against the smooth surface roll (14) of the press S from which the web (W) is to be removed. , and a transfer fabric (19) is passed through a transfer nip (N) between said transfer suction roll (20) and said smooth surface press roll (14) and a web (W) is transferred and adhered to said transfer fabric (19) in the suction zone (20) of said transfer suction roll (20). and holding the web (W) on said transfer fabric (19) by means of a vacuum holding zone (20a) or the like of the transfer suction roll (20), and in which method said transfer fabric (19) and the associated web ina (W) is passed over one (25) or more drying cylinders (21,22,23,25) and the web (W) is further passed through a so-called as a single fabric outlet (24,35) for the subsequent drying cylinders of the drying section, characterized in that in the method 20 the web (W) is transferred from said transfer fabric (19) to the so-called to the single export fabric (24; 35) by pressing the web (W) against the surface of the drying cylinder (22; 25) with said transfer fabric (19) and guiding said so-called a single take-up fabric (24; 35) over the latter drying cylinder (22; 25) in a particular sector so that said drying cylinder (22; 25) in which the transfer from one fabric (19) to another (24; 35) takes place is located between both said fabrics (24; 35); 19; 24,35) outside the loops. Method according to Claims 1 to 3, characterized in that the transfer fabric (19) is guided by a so-called as a single fabric outlet over a precursor of the drying cylinders (21,22,23) such that the lower row cylinders (21,22) are located inside the transfer fabric (19) loop and the top row cylinders (22) are located outside the transfer fabric loop. A method according to claim 2, characterized in that said bottom row cylinders (21) maintain a web (W) on the outer surface of the transfer fabric (19) at the vacuum prevailing in the suction zone (21a, 23a) of said cylinders (21,22). . 8 72162 A. A method according to any one of claims 1 to 3, characterized in that the speed of the transfer fabric (19) is about 0.5% to 1% higher than said press roll (IA) with which the transfer suction roll (20) forms a transfer nip ( Ng), circumferential speed. 5 Method according to one of Claims 1 to A, characterized in that the transfer fabric (19) is rehabilitated mainly or substantially by felting devices based on blowing devices (18 '). 10 Method according to one of Claims 1 to 5, characterized in that the transfer fabric (19) is guided in a downward direction to the first drying cylinder (21) (Figs. 1 and 2). Method according to one of Claims 1 to 5, characterized in that the transfer fabric (19) is guided after the holding zone (20β) of the transfer suction roll (20) to a first drying cylinder (25) which is a top-row cylinder of the drying cylinder group (Fig. 3). II