FI79870C - Process of forming part of a paper machine - Google Patents

Description

7 9 870 1 Method in the forming part of a paper machine Förfarande vld formningsdel av en pappersmaskin 5

The invention relates to a method for guiding a web of wreckage in a forming section of a paper machine into a suction roll pit or the like from a return loop of a forming loop, in particular a two-ply wire loop, in which the web is removed from the surface of said roll by scraping or other similar means and led to a suction roll well below or other similar paper wrap handling or transfer device.

Recently, so-called wire forming fabrics have become more common. two-ply fabrics used especially on high-speed paper machines for certain reasons related to web formation. The bilayer fabrics 20 are intended to reduce wire marking and have a smooth outer surface and a relatively rough rigid base portion. Double-ply fabrics are generally made of plastic and also aim to have better wear resistance than bronze fabrics, to improve water economy, to improve fiber and filler retention, and to allow for higher wire tension.

25 The labyrinthine structure of such a wire tends to adhere relatively tightly to the web, especially due to efficient dewatering. However, despite this adhesion, there have been no difficulties in removing the web with the pick-up roll and transferring it from the wire of the forming part to the pick-up fabric. However, in connection with the use of said double-layer fabrics, it has proved that the removal of the wrecked web from the forming wire, e.g. .

2 79370 1 With the flat wire sections of »it is known to place high-pressure water spraying devices inside the wire loop downstream of the wire drawing roller, i.e. after the turning roll, by which the web going to the wreck is detached from the return wire of the forming wire and the thus removed web is dropped. For purposes of this prior art, reference is made, by way of example, to U.S. Patent Nos. 3,218,227 and 4,154,648. The high-pressure jet devices disclosed in these publications are further intended to clean the forming wire from wet paper web of adhering fibers and resin. These wire section high pressure jet devices use either low fiber circulating water or fresh water. Circulating water is better because of the balance of the water system, but in some cases the fibers present can cause difficulties.

As is apparent from the aforementioned U.S. patents, said cleaning devices are most commonly located in the area between the draw roll and the first return roll. In the meantime, a continuously operating normal shower is needed to ensure that no mass gets between the return roller and the wire while driving. During a break in which the web is run into the wire pit, two jets are required to detach the web from the wire. Especially with a sum of pak-20 paper grade, the web can be very solid after the suction roll of the wire, almost leathery tough. Therefore, the first of these showers is the irrigation shower and then the powerful drop shower for the actual removal. The operation of the wire cleaning jets must be automated so that they start spraying as soon as the removal movement of the pick-up roll 25 begins and close as soon as the wire stops. In addition, all guide rollers are usually equipped with wash showers.

Prior art down to drop spraying devices are divided into three segments of a paper machine in the cross direction: 30 1.-side edge of the tape shower 2. The self paper web (br) shower 3. The drive-side edge of the tape jet 35 of these devices 1 and 3 are continuously running and shower 2. engages the staple automatically controlled.

Il 3 79870 1 The disadvantage of conventional drop-jet devices is that they require a special high-pressure system with high-pressure pumps combined with automatic breakdown. In addition, these jet devices consume a relatively large amount of water, which in addition may cause instability and disadvantageous dilution in the pulp system.

In addition, it is already known to supply large amounts of water to the groove between the drawing roll and the wire with high-pressure jet devices. If this procedure is applied to double-layer fabrics, a great deal of water is required because the speed of the wire is generally high and the internal volume of the double-layer wire is, for example, substantially higher than that of bronze fabrics. Large volumes of water require a large amount of pumping energy and, in addition, as previously noted, cause consistency disturbances in the short circuit of the pulp system when the pulp is suddenly diluted. In addition, difficulties have been encountered in removing the web itself, despite the large amounts of water.

It is an object of the present invention to provide a new method and a paper machine forming section which reduces the need for high pressure drop jet devices. It is a further object of the invention to improve the water economy of the paper-20 mill and to reduce energy consumption, in particular by eliminating the energy used by high-pressure pumps in this respect.

It is a further object of the invention to reduce the use of fresh water. The more extra water 25 outside the normal circulating water system (which is usually fresh water) has to be used, the more it has to be burdened from the plant's water treatment plant so that the wastewater load caused by the plant does not exceed the given legal limits.

In order to achieve these and later objects, the method of the invention is mainly characterized in that a special release transfer roll is used as said roll, which is adapted to act as a first wire return roller guide roll after the forming wire drawing roll.

In test runs performed on a test paper machine, it has been found that the wreck transfer roller adapted according to the method of the invention operates safely and efficiently. This is based on the surface properties of the wreck transfer roll, i.e. __ - r- ____ 4 79870 1 that the web going to the wreck adheres to a sufficiently smooth surface of the roll under the influence of adhesion forces.

A preferred method of operation of the invention is partially based on the trailing side of the roll 5 resulting from the so-called wedge mode. to the register roll effect, which is known to be due to the pumping effect of the rotating roll so that a vacuum is created in said wedge space, which creates a pressure difference on the opposite side of this wedge space and the wire thereby, which tends to move the web away from the wire

When using the method according to the invention, no drop jet devices are necessarily required, at least not high-pressure, so that the high-pressure pump and the energy consumed by it are completely avoided. The amount of spray water used is also reduced by the beneficial effects described above.

In connection with the method according to the invention, water jet devices can also be used, but the purpose of these possible devices is only to bring the moisture content of the web to such a level that the roll separation according to the invention is successful. Such devices do not require a high-pressure water system and the amount of water they consume is in any case small.

The invention will now 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.

The figure shows a schematic side view of a paper machine forming part applying the method according to the invention and 30 devices.

The two-wire section according to the figure consists of a lower wire 2 and an upper wire 3.

The lower wire 2 runs supported by the rollers 11, 15, 16, 19 and 23 so that immediately after the headbox 1 a normal single-wire flat wire part 5, 35 is formed, in connection with which the dewatering means 4 known per se, e.g. foil it, act. The loop of the upper wire 3 is guided by rollers 8. In the flat wire section 5 the water is carefully removed so that the pulp web on this wire section 5 5 79370 1 has such a degree of felting that the fibers, at least the longer fibers, can no longer move relative to each other in peeling-5 strength.

The upper and lower wires 2 and 3 form a two-wire dewatering zone after the single-wire flat wire section 5. The downwardly curved portion 6 of the wires 2 and 3 is guided by a closed-ended dewatering box 7 or a corresponding dewatering roller.

In the curved section 6, the dewatering is affected by the centrifugal force due to the curvature of the track and the compression between the wires 2 and 3. The portion 6 discharges water from the web W in the opposite direction to the single wire 15 initial portion 5, which tends to even out the unilateral distribution of fines and additives caused by the parallel dewatering of the planar portion 5, as these materials are still able to migrate in an otherwise stable fibrous structure. The water removed from the web W above is collected in a box 9. The two-wire section continues in a planar manner up to the suction roll 20 11, and in this section the suction boxes 10 and the water collecting members 13 known per se also act.

With the suction zone Ilot of the suction roll 11, thanks to the effective vacuum, the web W follows the run of the lower wire 2. In normal running, the web W is transferred by a run of a lower wire 2 between the suction roll 25 and the wire drawing roll 15 to the pick-up felt 14 in the suction zone 12 <X of the pick-up roll 12 under the action of an effective vacuum. When starting the paper machine or in the event of a break or other disturbance in the web W, the web going to the wreck is guided to the well 24 under the suction roll, the so-called couch pit. At least in connection with the start-up of the machine 30, the pick-up roller 12 is moved to a position where the pick-up point is open and the pick-up blanket 14 is separated from the downstream wire 2 by special support devices (not shown). the passing web W follows the wire 2 over the draw roll 15 downstream thereof.

35

As previously described, the web W adheres particularly strongly to the maze structure of the two-layer wire 2 6 79870 1, as a result of which the web W going to the wreck follows the roll 15 downstream of the wire 2. According to the invention, a special wreck transfer roller 16 is arranged downstream of the wire 2 above the suction roll well 24. This roll 16 is provided with a wreck-5 removal scraper 17. The surface 16 'of the release transfer roll 16 is a smooth rubber or metal surface or the like. 16 surface of the roll 16 'is selected so that the broke passing the web V of the adhesion forces and / or the wire 2 and the roller 16 of the downstream wedge space between the 22 resulting from the regis-teritelavaikutuksen allows the roll 16 and the wire 2. The doctor blade 17 blade October 18, the web W is scraped from the roll 16, and it ends up as a wreck W "in a well 24, the surface of which is marked with the reference number 25.

According to the figure, before the wire drawing roll, water jet devices 20 are arranged over the entire width of the wire 2 or at least the web W, the nozzles of which are directed to the inner surface of the wire 2 by water jets S for pre-separating the wrecked web W from the wire 2. The jets S cleansing. The jets S can be used, for example, in combination with the pre-removal (wetting) of the web and as cleaning jets for the drawing roll from the fibers and resin adhering to it.

Through the nozzles 21, water is applied to the gap between the wire 2 and the drawing roll 15 only to such an extent that the wreck web W remains sufficiently intact on the roll 15 and thus the web W transferred downstream of the wire 2 is removed from the wire 2 only by a special wreck transfer roll 16 according to the invention.

25

In some cases and with some pulp grades, the web is removed reliably even without the above-mentioned water jets S. However, in many cases it is most advantageous to use said water jets because they allow the scrap web removal conditions 30 to be adjusted according to wire type, pulp quality or other factors. In addition, as noted above, water jets are used to clean the wire of fibers and other contaminants adhering to it. It should be emphasized, however, that in the context of the invention, the amounts of water sprayed by the device 20,21 in any case are quite substantially lower than the amounts of water used in the previously known drop-jet devices.

Il 7 79370 1 Different showers can also be provided for pre-removing the web W and washing the traction roller 15, which are controlled separately. Edge strips generally also have their own nozzles, but both or both drop-down jets may not be required in the practice of the invention.

5

The figure shows an angle β, which is the sector in which the lower wire 2 bypasses the traction roll 15. According to a preferred embodiment of the invention, said angle β can be increased relative to normal so as to provide a sufficiently large frictional force to drive the wire 2 on the traction roll 15.

The magnitude of the angle / μ is preferably in the range of 100 ° to 150 °, most preferably 120 ° to 135 °. Thanks to the wreck transfer roll 16 located outside the wire loop 2 according to the invention, the above-mentioned angle / 3 can be increased and in addition said roll 16 functions as described above together with its scraper 17,18 as a device which smoothly and reliably transfers the wreck W to a wire pit 24 or the like.

The aforementioned plastic wires take up much more drag than e.g. bronze wires, so the increased coverage angle / ¾ and the improved friction between the draw roll 15 and the wire 2 due to the absence of aquaplaning result in a substantial combined advantage. In addition, it is noted that it is more advantageous to draw more plastic wires (e.g. more than 60% of the load) on the traction roller 15 than on the suction roller.

In order to carry out the method according to the invention, it is necessary that the roll 16 be provided with a scraper 17 or a similar transfer device, e.g. a second roll, which in turn is provided with a scraper, because otherwise it is obvious that the wreck does not fall into the pit 24 but wraps around the roll Ib. is most often the result of damage to the wire 12 and other equipment.

30

In addition, it should be noted that the surface of the roll 16 must be selected in addition to the transfer properties of the wreck so that it can be reliably scraped. The scraper 17,18 must also be carefully designed and constructed in such a way that it securely moves the wreck W "into the pit 24 and does not pass 35 e.g. a thin strip of web which, when wrapped around the roll 16, causes local stretching of the wire 2 and thus damages the wire 2.

8 79870 1 The angle CX indicated in the figure is the angle at which the wire 2 between the rollers 15 and 19 deflects the transfer roll 16. The angle o (is relatively small, preferably about 5 °, in order to obtain the lightest possible contact between the roll 16 and the web 2 on the wire. Said light contact has proved to be important for the removal of the web W 'from the wire 2 to the wreck.

The transfer roll 16 according to the invention can be easily installed on existing paper machines. From the point of view of retrofitting and / or wire change of the roll 16 and the use of space, it is advantageous that the transfer roll 16 is mounted on 10 special movable support structures, e.g. support arms (not shown). By means of the power devices arranged on these support arms, e.g. pneumatic cylinders, the transfer roller 16 can be lowered out of its operating position and correspondingly moved to its operating position to press against the wire 2 with a suitably low surface pressure (at a small angle ex).

15

Once the operation of the web forming section has been such that the web W can be transferred to the pick-up fabric 14, the pick-up point is closed under the control of the automatic cut-off, whereby the pick-up roll 12 is absorbed with a suction pulse 12 CX. under the influence of the prevailing suction, the web W follows the pick-up felt 14 and the run-20 to the press part of the paper machine in a manner known per se. In this normal operation of the paper machine, water jet devices 20,21 are not used, and the roll 16 then acts only as a guide roll for the downstream of the lower wire 2 as the scraper 18 blade 18 cleans the surface 16 'of the roll 16 of contaminants adhering to the outer surface of the wire 2. In general, however, one continuously running nozzle system is required to wash the draw roll 25.

The roll 16 has also been found to have a clear fiber cleaning effect on the fiber 2 in the position according to the invention during the normal operation of the machine (i.e. not in the drop-down situation).

30

It is not necessary to arrange a separate use for the release transfer roll 16, especially if the coverage angle CX of the roll 16 is large enough, e.g. approx. 5 ° ... 10 °. In some cases, the roll 16 can be used as an auxiliary drive roll, making the use of other auxiliary drive rollers unnecessary, since the roll 16 35 thus increases the pulling capacity of the roll 15. The placement and use of the roll 16 according to the invention also increases the traction of the roll 15 due to the increase in the angle.

9 79870 1 The figure shows a plate or strip-like member 26 placed inside the wire loop 2 on the roll 16, under which the pumping effect of the wire 2 creates an overpressure, which enhances and ensures the release of the wrecked web W from the lower surface of the wire 2 and the transfer and adhesion 5 to the roll 16 .

Instead of the scraper 17,18, instead of the above-mentioned additional roll, water jet devices can also be used to remove the wreck web W 'from the surface 16' of the roll 16, which direct a sharp jet at the web release point 10. Instead of the pit 24, the wreck web can be fed to a special wreck conveyor located under the roll 16, which takes the wreck to a suitable further processing site.

In the following, the claims are set out, within the scope of the inventive idea defined by which the various details of the invention may differ from the foregoing.

20 25 30 35

Claims (5)

A method for guiding a paper web (W) wrecking in a paper machine forming section to a suction roll pit (24) or the like from a return loop of a forming wire 5 (2), in particular a two-ply wire loop, in which the wreck web (Wr) is detached from said forming wire 2) from the outer surface of a roll (16) on a sufficiently smooth surface (16 ') of which a wreck web (W ") is adhered and in which method the wreck web (W) is removed from said roll (16) 10 surface (16') by scraping or other similar means and fed to a suction roll pit (25) or other similar paper wreck handling or transfer device below, characterized in that said roll (16) uses a special release transfer roll (16) adapted to operate after the drawing roll (15) of the forming wire (2). 15 as the first return roller guide wire for the wire (2). 1 Claims A method according to claim 1, characterized in that said release transfer roll (16) causes a relatively low surface pressure in its side sector («*) to the forming wire (2), which is obtained by selecting the size of said side sector (a.) To be about 5 °. . Method according to Claim 1 or 2, characterized in that the detachment of the wrapped paper web (W) is intensified and / or secured by a plate-like or strip-like member (26) or other similar part arranged inside the loop of the wire (2) near the detachment transfer roll (16). providing a local overpressure area based on the pumping effect of the wire (2) that enhances and / or ensures the removal of the web (W). 30 A method according to claim 1, 2 or 3, characterized in that said release transfer roll (16) is mounted to guide the downstream of the forming wire (2) so that the cylindrical shell of the release transfer roll (16) is located at least partially on the draw roll 35 of said wire (2). (15) and a wire (2) below the next guide roll (19) and above the tangent plane common to said rollers (15,19). 11 79870