WO2003038186A1

WO2003038186A1 - Multi-nip calender

Info

Publication number: WO2003038186A1
Application number: PCT/FI2002/000840
Authority: WO
Inventors: Erkki Kirveskari
Original assignee: Metso Paper, Inc.
Priority date: 2001-10-30
Filing date: 2002-10-29
Publication date: 2003-05-08
Also published as: FIU20010404U0; FI5218U1

Abstract

The invention relates to a calender comprising at least one hard-surfaced roll (151) and at least two backing rolls (161) stacked up one on top of the other. Each hard-surfaced roll has a take-out roll (156) for detaching the web from the surface of the roll. At least one backing roll (161) is without a take-out roll.

Description

Multi-nip calender

Background

The invention relates to a calender that is used in papermaking, a multi-nip calender in particular, comprising at least one hard-surfaced roll, such as a heated thermo roll, and at least two backing rolls, such as polymer-coated rolls, piled up one on top of the other.

In the stacks of calender rolls there are take-out rolls, through which the web coming from a nip is led into the following nip. The take-out roll is used to keep the web off the roll surface in places other than the nip. In this way, for instance, drying and formation of steam pouches between the web and the roll are prevented.

One calender of this type is described in the publication FI-C-96334, for example.

In the calender described, problems might occur with web feeding particularly when running at high velocities. The take-out rolls exert a large deflecting angle on the web, wherein the web-feeding belt tends to come off the ideal track line.

Description of the invention

A calender according to claim 1 has now been invented. The other claims disclose some preferred embodiments thereof. The calender according to the invention has at least one backing roll, against which there is no take-out roll. Preferably, all backing rolls are without take-out rolls.

In the calender according to the invention, the web is easier to feed than in conventional calenders. Furthermore, the structure as such is also simpler.

The hard-surfaced roll is preferably a chilled roll or a steel roll, e.g., a thermo roll. The backing roll is preferably a soft-surfaced roll, such as a polymer-coated roll.

In the following, some embodiments of the invention are described in detail. The appended drawings are part of the specification. Fig. 1 shows the calender as viewed from the side.

Fig. 1 shows a schematic side view of a supercalender that applies the invention. The supercalender is generally marked with a reference number 10. It comprises a calender body 11 having a stack of rolls 12 formed from several rolls mounted on a vertical plane. The stack of rolls 12 comprises an upper roll 13, a lower roll 14 and several idle rolls 15-22 arranged one on top of the other between the upper and the lower rolls, the rolls being arranged so that they are in nip contact with one another. A paper web W is lead through a spreader roll 135 and the take-out roll 136 to the upper nip N_\ and further through the other nips N₂-N₈ of the calender and, finally, out through the lower nip N₉. The upper roll 13 of the calender is a variable crown roll. It is provided with upper cylinders 134 at both ends of the calender, which are attached to the calender body 11, the piston of the upper cylinder affecting the bearing cup 131 of the upper roll. The shaft of the upper variable crown roll 13 is mounted in the said bearing cup 131 and the roll is provided with inner loaders, in a conventional manner, which can be used to adjust the bend of the roll jacket as desired. Vertical guide bars 132 are formed in the calender body 11, into which guide bars the bearing cups 131 are movably fitted and along which the bearing cups 131 can be moved by means of the upper cylinders 134. It is actually not necessary to use the upper cylinders 134 for loading the stack of rolls 12 but, in that case, the upper cylinders are used to close and open the upper nip Nj. However, it is also possible to use the upper cylinders 134 for loading the stack of rolls 12 either alone or together with the inner loaders of the upper variable crown roll 13. The actual loading of the nips N N₉ of the stack of rolls 12 can also be carried out by means of the inner loaders of the upper variable crown roll 13 or the lower variable crown roll 14 only. The upper roll 13 is provided with an elastic polymer coating.

Correspondingly, the lower roll 14 of the calender is a variable crown roll, the roll jacket of which is rotatably mounted on the shaft of the roll and which roll 14 is provided with inner loaders, which can be used to adjust the bend of the roll jacket as desired. The axis of the lower roll 14 is mounted in bearing cups 141, which are movable on the vertical plane by means of the lower cylinders 143. Consequently, by using the lover cylinders 143, the stack of rolls 12 can be opened in a conventional way. Because of the lower variable crown roll 14 the linear pressure profiles can be kept regular at the nips N N₉ of the stack of rolls 12. The lower roll 14 is also provided with an elastic polymer coating 142. Several idle rolls 15-22, which are in nip contact with one another, are arranged between the upper roll 13 and the lower roll 14 of the calender. The idle rolls 15, 17, 20 and 22 are chilled rolls that can be heated. The idle rolls 16, 18, 19 and 21 are polymer-coated rolls.

In the following, the two uppermost idle rolls 15, 16 are described in detail. In the disclosed embodiment, the uppermost idle roll 15 is thus a hard-surfaced roll, which is rotatably pivoted in the bearing cups 151 at its ends. The bearing cups 151 are mounted on arms 152, which are articulated to swivel on the calender body 11 by means of the axial articulations 153 of the roll 15. The arms 152 are provided with relief devices 154, which in the disclosed embodiment are pressure medium-driven piston-cylinder devices, which are attached to the said arms at the one end thereof, and to lugs 155 mounted in the calender body 11 at the opposite end thereof. The said piston-cylinder devices 154 can be, for example, hydraulic or pneumatic cylinders or the like.

The second uppermost idle roll 16, on the other hand, is thus a roll with a soft surface, which in the disclosed example is provided with an elastic polymer coating 166. The said roll 16 is rotatably pivoted in the bearing cups 161 at its ends, which bearing cups are mounted on the arms 162, respectively. The arms 162 are articulated to swivel on the calender body 11 by means of the axial articulations 163 of the roll 16. The arms 162 are further provided with relief devices, e.g., pressure medium-driven piston-cylinder devices 164, which at their one end are attached to the said arms 162 and at their opposite ends to lugs 165, which are mounted in the calender body 11. The support of the other idle rolls is not indicated in detail by any reference marks in Fig. 1, but the support of these rolls 17-22 is similar, as can be observed in the figures.

The relief devices 154, 164 are used to bring a relieving force to the support structure of the rolls 15, 16, the force being used to fully compensate the loads caused by the rolls and the accessories attached to the rolls. Accordingly, the weights of the rolls and the accessories have no effect on increasing the nip load. In that case, the linear load at each nip N N₉ can be made essentially equally great, when so desired. This is because a standard load is brought to the calender by means of the variable crown roll that is used as the upper roll 13. After the nips N_b N₃, N₆ and N₈, the web W is detached from the surface of the chilled rolls 15, 17, 20 and 22 by the take-out rolls 156. Instead, after the nips N₂, N₄, N₅ and N₇, there is no take-out roll; therefore, the web runs along the surface of the corresponding polymer-coated rolls.

Claims

1. A calender comprising at least one hard-surfaced roll (151) and at least two backing rolls (161) stacked up one on top of the other, and wherein each hard- surfaced roll has a take-out roll (156) for detaching the web from the surface of the roll, characterized in that at least one backing roll (161) is without a take-out roll.

2. A calender according to claim 1, characterized in that all backing rolls (161) are without take-out rolls.

3. A calender according to claim 1 or 2, characterized in that the hard-surfaced roll (151) is a chilled roll or a steel roll.

4. A calender according to any of claims 1 to 3, characterized in that the hard- surfaced roll (151) is a thermo roll.

5. A calender according to any of claims 1 to 4, characterized in that the backing roll (161) is a soft-surfaced roll, such as a polymer-coated roll.