EP0803604B1 - Wet press - Google Patents

Description

The invention relates to a press for dewatering fibrous webs with two pressing elements, the pressing surfaces of which form a press nip are pressed against each other, the fibrous web together with at least one between the fibrous web and a respective one Pressing element running drainage belt through the press nip is guided and each drainage belt in the at the press nip outlet subsequent area is separated from the fibrous web.

A press of the type mentioned is known from DE-A-37 08 191.

In one known from DE-OS 41 12 355 Press the fiber web to be dewatered between two drainage belts passed through the press nip, the fibrous web at least in one on the press nip following section with at least one drainage belt stays in touch. This has the advantage that the Fibrous web in this section of the drainage belt in question is performed, especially at high speeds to avoid web breaks or web flutter can be beneficial, however, it can rewetting the fibrous web starting from the dewatering belt come.

The object of the invention is a press of the aforementioned Way of creating that for high web speeds is suitable and in which a rewetting of the fibrous web prevented at the press nip outlet or at least strongly is reduced.

This object is achieved in that a first both pressing elements a grooved or blind drilled surface and that second pressing elements has a smooth and closed surface, so that the drainage of the fibrous web (1) in the press nip predominantly the first press element is that the fibrous web at the press nip outlet is separated from the first pressing element and together with a Drainage belt in a subsequent to the press nip outlet Section over a predeterminable angular range on the second pressing element is that the thickness elasticity and / or absorbency of the a drainage belt is chosen so that with relaxation this drainage belt when leaving the press nip outlet forms a short suction zone adjoining the press nip outlet, and that the fibrous web immediately following this suction zone from which a drainage belt is separated.

By immediately removing the drainage belts from The fibrous web at the press nip outlet is rewet the fibrous web significantly reduced. Besides, can the guide roller for the fibrous web and / or a support belt in the form of a felt or sieve that leads to a subsequent one Unit belongs, arranged as close as possible to the press nip through which the free move, that is, that of none Belt-supported section of the fibrous web up to the guide roller is reduced so that because of the most extensive Guiding the fibrous web the risk of web breaks and Web flutter reduced even at high speeds or the tension in the fibrous web is kept lower can be.

Otherwise, guide rollers for the drainage belts Press in the area after the press nip drop, causing not only is space gained, but also a suction effect with regard to the liquid to be removed from the fibrous web in the direction of the drainage belts running away quickly can be achieved. This can reduce the degree of drainage be increased, so that one can, for example, in papermaking with just such a dewatering press inside the paper machine can get by.

According to a further embodiment it is provided that at least one side of the fibrous web between the dewatering belt and the fibrous web preferably has a separating screen low liquid storage capacity due to the Press nip is guided and the fibrous web after leaving of the press nip over a predeterminable distance on the Separating sieve is guided. This increases the risk of web breaks and web flutter even at high speeds reduced.

The separating screen can, since it is in the press nip against the fibrous web is pressed, be designed with little marking. There are but also applications in which an embossing of a fibrous web side targeted through the separating sieve, for example for papers for packaging or sleeves. The separating screen can then have corresponding markings.

According to a preferred embodiment it is provided that predetermined one of the pressing elements to form a press nip Longitudinal extension with the other pressing element a wide, in particular has a concave shape, pressing surface and a roller jacket made of a flexible material possesses that moves around a carrier and over at least one support element is supported on this, and the other Press element a complementary to the wide press surface Has pressing surface and preferably from a rotating cylindrical roller is formed.

In the case of a pressing element with a wide pressing surface, one can be special rapid routing of the drainage belt, which this pressing element rotates, due to the fibrous web through the adjoining the non-convex pressing surface convex curvature of the roll shell can be achieved, taking it is advantageous if the drainage belt on this pressing element at least in a section following the press nip is guided on the pressing element.

If the fibrous web between two drainage belts is passed through the press nip, is convenient Elasticity in thickness and / or the absorbency of the drainage belt on the side of the fibrous web on which the fibrous web from the dewatering belt or the separating screen should be taken, greater than the thickness elasticity and / or the absorbency of the drainage belt the opposite side of the fibrous web. Through this Measures is achieved that the drainage belt, to which the fibrous web should stick, in a short Section relaxed after the press nip, creating a Suction zone is formed, in which the together with the Drainage belt-running fibrous web or also the Separating sieve is still withdrawn water. After that, this drainage belt should due to the threat of rewetting from the fibrous web or also the separating screen, what can take place at least partially along the pressing element.

When using a separating screen, this is preferred provided below the fibrous web so that Separating screen a good guidance of the fibrous web to the next one Unity can be guaranteed.

Figur 1

eine schematische Seitenansicht einer Ausführungsform einer erfindungsgemäßen Presse,

Figur 2

die in Figur 1 gezeigte Presse mit einer vorgeschalteten weiteren Preßvorrichtung,

Figur 3

eine Seitenansicht einer weiteren erfindungsgemäßen Presse;

Figur 4

die in Figur 3 gezeigte Presse mit einer vorgeschalteten weiteren Preßvorrichtung,

Figur 5

die in Figur 4 gezeigte Presse mit unterschiedlichen Entwässerungsbändern in beiden Pressen,

Figur 6

eine schematische Seitenansicht des Preßspalts der in den Figuren 3 bis 5 dargestellten Presse,

Figur 7

eine erfindungsgemäße Presse mit nur einem Entwässerungsband, der eine weitere Preßvorrichtung vorgeschaltet ist, und

Figur 8

den Preßspalt der in Figur 7 dargestellten Presse in schematischer Teilansicht.

With regard to advantageous embodiments of the invention, reference is made to the subclaims and the following description of exemplary embodiments of a press according to the invention with reference to the accompanying drawing. The drawing shows:

Figure 1

2 shows a schematic side view of an embodiment of a press according to the invention,

Figure 2

the press shown in Figure 1 with an upstream further pressing device,

Figure 3

a side view of another press according to the invention;

Figure 4

the press shown in Figure 3 with an upstream further pressing device,

Figure 5

4 with different drainage belts in both presses,

Figure 6

3 shows a schematic side view of the press nip of the press shown in FIGS. 3 to 5,

Figure 7

a press according to the invention with only one dewatering belt, which is preceded by a further pressing device, and

Figure 8

the press nip of the press shown in Figure 7 in a schematic partial view.

In all figures, the press consists of two on top of each other arranged pressing elements 2 and 3, the pressing surfaces against each other can be pressed, through the press nip 4 next to the fibrous web 1 at least one between the fibrous web 1 and one of the pressing elements 2 and 3 arranged drainage belt 5 or 6 runs. The bottom one Pressing element 3 from a rotating cylindrical roller be conventional or controlled by deflection can, formed. The upper pressing element 2 can be a concave Form press surface, which is a flexible material existing roller jacket 10 around a (not shown) Carrier moves and on at least one support member 11 supports this carrier.

However, there are other devices for forming Press nips 4 imaginable. For example, both pressing elements 2, 3 a wide press area and each a flexible Own coat.

The fibrous web 1 is removed in these exemplary embodiments via a suction roll 17 from an upstream Sieve section and it is delivered to the drying cylinder 18th a subsequent dryer section.

Furthermore, the exemplary embodiments have in common that the Drainage belts 5 and 6 after leaving the press nip 4 away from the fibrous web 1 as quickly as possible and in a section 12 on the corresponding pressing element 2 or 3 run along.

The drainage belts 5, 6 are otherwise as in the figures 1 to 5 can be seen, guided over felt guide rollers 13 and can in front of the press nip 4 to guide the fibrous web 1st be used. Simply by using two drainage belts 5 and 6 can drainage capacity the extended nip press can be increased significantly. About that In addition, the convex curvature of the upper press element allows 2 the immediate at the outlet of the concave press surface Moving the drainage belt 5 from the fibrous web 1 after the press nip 4 at least in a section 12 along the pressing element 2, which is a rewetting of the fibrous web 1 prevented from this drainage belt 5.

In order not to bend the fibrous web 1 too much and around an air inlet to the top of the fibrous web until tight at the press nip 4 against the direction of travel, which reduces the risk of negative pressure developing there, the fibrous web 1 runs in the case of those in FIGS and 2 shown presses after the press nip 4 approximately tangential to the lower press element 3 in one, albeit very short, Suction zone 14 on the underside of the fibrous web together with the lower drainage belt 6 along the cylindrical Press element 3. In the suction zone 14 there is a Relaxation of the elastic compared to the upper drainage band 5 lower drainage belt 6 and thus to one Aspiration of liquid from the fibrous web 1 in the lower drainage belt 6. Following the suction zone 14 the separation takes place due to the impending rewetting also the lower drainage belt 6 from the fibrous web 1, the drainage belt 6, as in FIGS. 2, 3 and 4, in a region extending beyond the suction zone 14 Section 12 runs along the pressing element 3.

By guiding the drainage belts 5 and 6 along of the pressing element 2 or 3 gained space for this used a guide roll 7 following the press nip 4 if possible to be arranged close to the press nip 4. This shortens the free one Length of the fibrous web 1 between the press nip 4 and the Guide roller 7 and thus acts to flutter and tear off the Fiber web 1 opposed. Runs over the guide roller 7 a support belt 8 for guiding the fibrous web 1 to one Drying cylinder 18 of a subsequent drying unit. The support band 8 is usually designed as a sieve and can also arranged on the other side of the fibrous web 1 his.

As shown in Figure 2, the press 2, 3 can at least a further pressing device 17, 18 with a press nip 4 ' be upstream. In this case, the drainage belts go through 5, 6 together with the fibrous web in between 1 advantageously also the press nip 4 ' upstream pressing device, which makes the transport the fibrous web 1 between the upstream pressing device 17, 18 and the press 2, 3 simply designed.

At least one of the pressing elements 17, 18 is preferred the further pressing device a suction roll.

Figures 3 to 6 show long gap presses, in which between the drainage belt 6 of the lower pressing element 3 and the fibrous web 1 runs a separating screen 9, which here at least in a section before and after the press nip 4 is in contact with the fibrous web 1 and thereby the fibrous web 1 leads. This guidance of the fibrous web 1 can, for example, take place up to the subsequent unit.

It is also possible that two the fibrous web 1 including separating screens 9 through the press nip 4 become. Since the separating screen 9 together with the fibrous web 1 is passed through the press nip 4, it should depend on Requirements for the end product with little or strong marking and because of the risk of rewetting leaving the press nip 4 in any case a very small one Have liquid storage capacity.

The suction of the liquid takes place during the suction zone 14 the relaxation of the lower dewatering belt 6 by the separating sieve 9 through. Then, as shown in Figure 6 is, the drainage belt 6 of which together with the fibrous web 1 running separating screen 9 through its Guide along the pressing element 3 removed. To do the To improve the adhesion of the fibrous web 1 to the separating screen 9, can preferably the clamping force of the separating sieve 9 on Press nip outlet to be adjustable in the direction of web travel.

The suction zone 14 can in all versions with regard to their Expansion in the web running direction can be made variable, so that rewetting from the dewatering belt 6 is excluded becomes. This is possible by changing the course the fibrous web 1 after the press nip 4 via a change in position the corresponding guide roller and the adjustable Longitudinal tension in the separating sieve 9.

Since according to Figure 6 and other embodiments shown the fibrous web 1 in the suction zone 14 with the drainage belt 6 of the cylindrical pressing element 3 in contact remains, the drainage in the press nip 4 should predominantly to the other pressing element 2, which for example is achieved in that the concave pressing element 2 a grooved or blind drilled and the cylindrical press element 3 has a smooth surface.

Recommended for transferring or detaching the fibrous web 1 itself on the pressing element 2, 3 or the drainage belt 5, 6, to which the fibrous web should not adhere, the use of a scraper 15. If it is a pressing element 2, 3 with a wide pressing surface 4, the Scraper 15 in a region of the flexible roll shell 10 be arranged in which it does not have a slide bearing 16 is supported. This enables gentle scraping, because the scraper 15 at least slightly against the roller jacket 10 press in the air pressure prevailing in the roller jacket and can therefore be particularly effective.

To promote the separation of the fibrous web from the the scraper-provided pressing element or drainage belt is recommended, directly or indirectly from the scraper To blow air into the press nip outlet. This helps that Fibrous web as soon as it leaves the press nip 4 in to guide the right direction, and besides, that is going to Any negative pressure that arises from each press nip outlet is avoided.

As shown in Figures 4 and 5, the press 2, 3 upstream of a further pressing device 17, 18 be, which is traversed by the fibrous web 1. In in this case the separating screen 9 also passes through the press nip 4 ' this upstream pressing device 17, 18 to the fibrous web 1 in a simple manner from the pressing device 17, 18 to the press 2, 3 to transport. In advantageous The upper drainage belt 5, as in FIG Figure 4 shown, through the press nip 4 'of the upstream Press device guided. But it is also possible for different dewatering belts 5, 5 'to both presses use as shown in Figure 5.

Figures 7 and 8 show the press shown in Figure 5 with the proviso that only on the underside of the separating sieve 9 a drainage belt 6 is provided and the fibrous web 1 rests directly on the pressing element 2 on its upper side. In this case it is made directly with the fibrous web 1 coming into contact with the pressing element 2 a material repelling the fibrous web, in particular made of peeler rubber, for easy separation of the fibrous web 1 from the press roll 2 when leaving the press nip 4 to ensure.

Claims (13)

1. Press for dewatering fibrous webs (1), having two press elements (2, 3) whose pressing surfaces can be pressed against each other, forming a press nip (4), the fibrous web (1) being through the press nip (4) together with at least one dewatering belt (5, 6) that runs between the fibrous web (1) and a respective press element (2, 3), and each dewatering belt (5, 6) being separated from the fibrous web (1) in the area following the outlet from the press nip, characterized in that a first (2) of the two press elements (2, 3) has a grooved or blind-drilled surface, and the second press element (3) has a smooth and closed surface, so that the dewatering of the fibrous web (1) in the press nip predominantly takes place towards the first press element (2), in that the fibrous web (1) is separated from the first press element (2) at the outlet from the press nip and, together with a dewatering belt (6), in a section (12) which follows the outlet from the press nip, is guided on the second press element (3) over a predefinable angular range, in that the compressive elasticity and/or absorbency of the one dewatering belt (6) is selected such that, when this dewatering belt (6) is relieved of stress as it leaves the outlet from the press nip, a short suction zone (14) which follows the outlet from the press nip is formed, and in that the fibrous web (1) is separated from the one dewatering belt (6) directly following this suction zone (14).
2. Press according to Claim 1, characterized in that a guide roll (7) for the fibrous web (1) and/or a supporting belt in the form of a felt or wire is arranged as close as possible to the press nip (4).
3. Press according to Claim 2, characterized in that a supporting belt (8) is provided, in which the fibrous web (1) is guided from the guide roll (7) to a following unit, in particular a drying unit.
4. Press according to one of the preceding claims, characterized in that, on at least one side of the fibrous web (1), between the dewatering belt (6) and the fibrous web (1), a separating wire (9) preferably having a low liquid storage capacity is guided through the press nip (4) and, after leaving the press nip (4), the fibrous web (1) is guided on the separating wire (9) over a predefinable distance.
5. Press according to Claim 4, characterized in that the fibrous web (1) is guided on the separating wire (9) to the following unit, and the separating wire (9) is preferably arranged underneath the fibrous web (1).
6. Press according to one of the preceding claims, characterized in that one of the press elements (2), in order to form a press nip with a predefined longitudinal extent with the other press element (3), has a broad pressing surface, in particular a concavely shaped pressing surface, and has a roll cover (10) which consists of a flexible material, moves around a carrier and is supported on the latter by at least one supporting element (11), and the other press element (3) has a pressing surface which is designed to be complementary to the broad pressing surface and is preferably formed by a rotating cylinder roll.
7. Press according to one of the preceding claims, characterized in that at least one side of the fibrous web (1) is assigned a doctor (15), in order to separate the fibrous web (1), after it leaves the press nip, from a press element (2, 3) or a dewatering belt (5, 6) on which it is resting.
8. Press according to Claim 7, characterized in that the doctor (15) rests on a press element (2) with a broad, in particular concave, pressing surface, the press element (2) having a flexible roll cover (10) which is supported on a carrier by at least one supporting element (11), and in that the doctor (15) comes into effect between the supporting element (11) and a sliding bearing (16) additionally supporting the roll cover (10) on a carrier.
9. Press according to Claim 7, characterized in that in order to assist the separation of the fibrous web (1), effected by the doctor (15), from a further element (2, 3, 5, 6), air is blown into the press nip (4) in the direction opposite to the web running direction, the doctor (15) itself being used as an air distributor and an air knife or as a carrier for an appropriate air knife.
10. Press according to one of Claims 4 to 7, characterized in that the tension of the separating wire (9) at the outlet from the press nip can be adjusted in the web running direction in order to improve the adhesion between the fibrous web (1) and the separating wire (9).
11. Press according to one of Claims 1 to 7, characterized in that the fibrous web (1) is guided through the press nip (4) between two dewatering belts (5, 6), and the compressive elasticity and/or the absorbency of the dewatering belt (5, 6), on that side of the fibrous web (1) on which the fibrous web (1) is intended to be carried along by the dewatering belt (5, 6) or the separating wire (9), is greater than the absorbency of the dewatering belt (5, 6) on the opposite side of the fibrous web (1).
12. Press according to one of Claims 1 to 11, characterized in that a cover which comes directly into contact with the fibrous web (1) and belongs to a press element (2, 3) consists of a material which repels the fibrous web (1), in particular of peeler rubber.
13. Press according to one of Claims 1 to 12, characterized in that the dewatering belt (5, 6) and/or the separating wire (9), before they pass through the press nip (4), are guided through at least one preceding, further press device (17, 19), preferably at least one of the press elements of the at least one further press device being a suction roll.

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