FI113481B - Paper-making press section - Google Patents

Abstract

In the press section, of a papermaking machine, two independent and continuous elastic pressure belts are at the two pressure gap points. At the first point, one side of the web is in contact with the first belt and the other side of the web is in contact with the other belt at the second point.

Description

113481

Paper Machine Press Part - Pressparti i en pappersmaskin

The invention relates to a press section of a paper machine having the features set forth in the preamble of claim 5.

Such a press section is known from EP-0 107 606 B1. According to Figure 1 of this publication, two pairs of press-rollers are provided which each form a nip. Throughout each of the 10 nipples a web of endless and web-receiving felt passes, hereinafter briefly referred to as a "dewatering blanket". In addition, there is an endless resilient clamping element, in the form of a web, which successively passes through both nipples and some guide rolls. In the first nip of the en-15, the web to be dried is in contact with the resilient web and is then led to the other nip. This arrangement is intended to ensure that both dewatering felts are released from the web to be dried immediately behind each nip. Thus, behind each nip there is a complete transfer of the web 20 without the aid of dewatering felts. Thus, re-wetting of the web by dewatering blankets is avoided. Thus, the aim is ·, ·. increasing the drainage capacity of the press section, i.e. stripping; Greater dryness as it exits the press section.

• · *; ; A disadvantage of this known press section, however, is that the same side of the web · · touches the flexible web at both sides. Thus, one side of the web contacts the dewatering; felt in both nipples. As a result, different properties of the finished web (e.g., paper web), e.g., an abnormal smoothness or absorbency, are present.

Purifying the Future Paper Machines ;;;; the following requirements shall apply to tinplate:; ': 35 1. The number of nipples must be as small as possible, ie.

Chapter 2 should as far as possible not be exceeded.

113481 2 2. The web shall pass through each nip between the dewatering felt and the flexible compression element.

3. Care should be taken to avoid granite or similar stone or artificial stone rolls. In many cases, suction rollers should also be avoided.

4. The web must be in continuous contact with the conveying means, e.g., felt web 10 or resilient clamping element (i.e., closed web guiding without free web portion) when passing through the press member.

5. The finished product must have the same characteristics on both sides as far as possible.

15 6. The dewatering capacity of the press section must be increased as much as possible; i.e., the greatest possible dryness of the web must be achieved when leaving the press section, despite the high operating speed (in the order of 2000 m / min or 20).

··. ·. At the same time, it is required to modernize a known press section (e.g., U.S. Patent No. 42,856,766).

; ; In such a known press section, the web passes through the known '; ·; 25 over a smooth and hard press roll (for example, a stone roll).

This hard press roll has two additional press rolls: - two nipples, each with a dewatering felt. The web passes through two nips in a row.

This again has the disadvantage that, in each nip 30, the same side of the web comes into contact with the smooth surface (in this case, the smooth surface of the hard press roll) and that. the other side of the web is thus in contact with the dewatering felt in each of the nipples. As a result, again, it is '···' that the finished web has different properties on different sides.

* ·

Thus, it is an object of the invention to improve the known press section by retaining its smooth and hard press roll so that the finished product 113481 3 has as many characteristics as possible on both sides. In addition, closed web transport without free web portion is required, as well as maximum dewatering capacity of the press section.

This object is achieved by the feature of claim 1. Accordingly, the previous nip between the hard press roll and the additional press roll with the dewatering felt is retained. However, in the direction of travel behind this nip, the web 10 moves from a hard press roll to a flexible press member, for example a press edge. This then passes the web through a second nip formed by a second pair of rollers through a press web and a second dewatering felt.

According to the invention, one side of the web is first contacted with a smooth surface, i.e. the surface of a hard press roll, and then the other side of the web is contacted by that contact with a resilient press element, for example a press web. In this case, the dewatering preferably takes place first in one direction and then in the other direction. It is conceivable that an auxiliary nipple, ··. · With a double felt (according to the model of U.S. Patent 4,285,766) is coupled before said first nip.

In addition to the advantages set forth above, it is an additional advantage that the dry web is transported without the free portion of the web being en- * ·: '. · From the first nip to the other, since the web is moved immediately »% v ·' An additional advantage of this is that, when transporting the web from the first nip to the second nip, the re-wetting of the web is completely or nearly completely excluded.

*> I

However, when transferring the web from a hard press roll to a flexible press element, some problems must be eliminated. Namely, without special additional measures, it is not ensured that the web actually moves to the flexible press element. For example, it is possible that the web edges 113481 4 in particular tend to pass with the hard press roll. However, various ways have been found to manage these difficulties. The measures relating to these are set out in the subclaims.

5

An embodiment of the invention will now be described with reference to the drawing. This schematically shows a press section of a papermaking machine.

The illustrated press member comprises a first press I having a first pair of rollers 41, 47 and a second press II having a second pair of rollers 51, 52. A nip formed by the first pair of rollers 41, 47 passes a first web of felt 43 15 first nips. Therein, the paper web 9 is in direct contact with the press roll 47, which is a smooth and hard press roll, for example a stone roll.

Behind the first nip, the paper web 9 engages the hard paper roll roll 47 and thus passes therethrough to a delivery point where the paper web moves from the hard press roll. 47 for the flexible press rib 53. This takes the web 9 to work; Thus, when the underside of the paper web 9 in the first *: 25 press I contacts the smooth surface, i.e., any press roll 47, the upper side of the paper web contacts the second press surface 53 of the press web 53. against.

•

The second press II includes a so-called shoe press roll 30 around which the second dewatering felt 57 passes. Shoe Dress ·. the cross roll 51 comprises a stationary support piece 24, a tubular resilient press sheath 10, and a radially movable press shoe 26. The second press roll 52 of the second press II is formed as a bend control roll.

\ 35

Before the web delivery point (where web 9 moves from the hard press roll 47 to the press web 53), a device 50 may be provided to moisten the press web. In addition, a device for cooling the press web, for example in the form of a cooling roll 50 ', over which the press web 53 extends from the outside, may be provided. Further, a device 60 for heating the web may be provided prior to the web delivery point.

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Claims (8)

A press section for a paper machine for dewatering a web, preferably a paper web, the press section having the following features: a) through a first press nip (I) a first endless felt web (43) which receives water from the web (9) and through a second press nip (II) a similar second felt web (57); B) the arrangement is such that the web (9) is continuously in contact with at least one means of transport (e.g. with the second felt web); characterized in that: (c) the first roll pair press roll is a smooth and hardened roll. a rock roller which is in contact with the web (9); d) a flexible pressing element, e.g. a press web (53), receives the web (9) from contact with the hardened roll (47) and for the nip II of the second roll pair. 2. Press section according to claim 1, characterized in that the outer surface of the second flexible press element (53) which touches the web is smoother than the first flexible press element. · Corresponding side of the tester (47). * »·,; Press section according to either of the preceding claims 1 or 35, characterized in that a device (50) is arranged before the delivery point of the web to moisten the second flexible pressing element (53), e.g. water or meadow. 8 113481 Pressing portion according to claim 3, characterized in that the wetting means are arranged on each edge of only one flexible pressing element (53). Press section according to any of the preceding claims 1-4, characterized in that a device (50) is arranged before the delivery point of the web to cool down the flexible pressing element (53). Press section according to any one of the preceding claims 1-5, characterized in that a device (60) is arranged before the delivery point of the web to heat the web (9) and / or the hardened roller (47). Pressing section according to any of the preceding claims 1-6, characterized in that the flexible pressing element (53) rotates at a higher speed than the hardened roller (47). Press section according to claim 7, characterized in that,. The velocity difference is between 1-5%. 1. I 1 «1. t» * * · 'I · Iti I * *> I I · r t * · * · »* 1 · * • · * · * t» »» · »t»