EP2669431A1

EP2669431A1 - Multiroll calender

Info

Publication number: EP2669431A1
Application number: EP12169973.0A
Authority: EP
Inventors: Ari Lehtonen; Kauko Kamppila; Hannu Pullinen; Aaron Mannio
Original assignee: Metso Paper Oy
Current assignee: Valmet Technologies Oy
Priority date: 2012-05-30
Filing date: 2012-05-30
Publication date: 2013-12-04
Also published as: CN203360931U

Abstract

The invention relates to a multiroll calender for calendering a fiber web, particularly a paper or board web (W), which multiroll calender comprises at least two sets of calender rolls (10, 20) and a frame (40), the set comprising at least two calender rolls, in between of which calender rolls a calendering nip is formed, and at least one fly roll, in which at least one calender roll is attached by a pivotable lever (45) by a joint (50) to the calender frame (40). At least one fly roll (15, 25) of the multiroll calender is an inner fly roll (14, 24) and that at least one inner fly roll (15, 25) is attached at the center of the joint (50) of the lever (45), advantageously fixedly, such that the distance travelled by the web (W) between the nips of the calender does not cause web tension changes when the set of rolls is moved.

Description

In general present invention relates to calenders for fiber web in a fiber web machine. More especially the present invention relates to a multiroll calender according to preamble part of claim 1.
Calendering is generally carried out in order to improve the properties, like smoothness and gloss, of a web-like material such as a paper or board web. In calendering the web is passed into a nip, i.e. calendering nip, formed between rolls that are pressed against each other, in which nip the web becomes deformed as by the action of temperature, moisture and nip pressure. In the calender the nips are formed between a smooth-surfaced press roll such as metal roll and a roll coated with resilient material such as a polymer roll. The resilient-surfaced roll adjusts itself to the forms of the web surface and presses the opposite side of the web evenly against the smooth-surfaced press roll. Multinip, or multiroll calendering is calendering in a calendering unit, in which the nips are formed between a smooth-surfaced press roll such as metal roll and a roll coated with resilient material such as a polymer roll and the linear load increases in multinip calenders from the upper nip to the lower nip due to gravitation, unless roll relies systems are used. From prior art multiroll calenders are known, in which the set of rolls of which is formed of one or two stacks of rolls, each stack of rolls comprising at least two calender rolls. Multinip or multiroll calender are known for example by brand names OptiLoad and TwinLine and Janus. In FI patent 96334 is disclosed a method for calendering a paper or an equivalent web material in a calender in which method the web to be calendered is passed through nips formed by a deflection-compensated upper roll and a deflection-compensated lower roll, and by two or more intermediate rolls arranged between the upper and lower roll. The rolls are arranged as a substantially vertical stack of rolls. Supercalenders are multiroll calenders composed of alternating hard and soft rolls, which soft rolls are filled rolls that have a steel shaft around which specialty paper sheets with a hole in the middle are slid. The most common number of rolls is 9 - 12 but here can be up to 16 rolls.
In multiroll calenders the fly rolls are typically fastened of their bearing housings to the same fastening parts (levers) with nip rolls movable with the stack of rolls. This arrangement aims at ensuring that, when closing and opening the stack of rolls, distance travelled by the web between closed nips, while the nip rolls still are moving, in inner fly roll positions changes as little as possible. The arrangement provides for preventing breaks caused by too high web tension or too loose web in the closing and opening situations of the stack of rolls. One prior art arrangement of this type is disclosed in EP-patent publication 679204 , for example in figure 5. In turn in DE-patent publication 19820088 the inner fly rolls are attached to the calender frame.
An object of the invention is to create a multiroll calender in which distance travelled by the web between closed nips does not change and thus cause changes in tension of the web while the set of calender nip rolls is moved upwards or downwards.
Another object of the invention is further to provide means for controlling the rigidity of a joint in a multiroll calender and by this control the vibrations in a multiroll calender.
To achieve the objects mentioned above and later the multiroll calender according to the invention is mainly characterized by the features of the characterizing part of claim 1.
Further advantageous features of the invention will be disclosed in the dependent claims.
According to the invention is to the inner fly rolls of the set of rolls of the multiroll calender are attached at the center of the joint of the lever, advantageously fixedly such that the distance travelled by the web between the closed nips of the calender does not cause web tension changes when the set of rolls moves up or down.
The inventive arrangement of attaching the inner fly roll at the center of the joint of the lever supporting a calender nip roll in the multiroll calender also provides for that in case of offsetting the calender nip roll, in which offsetting the nip position of the calender roll transfers in respect of the overall nip line of calendering nips, an advantageous effect on web tension is achieved because the position of the fly roll does not change and thus also the distance travelled by the web remains constant.
According to an advantageous aspect of the invention at least one of the joints of the calender levers or calender load cylinder is provided with adjustable rigidity. The rigidity adjustment is based on guiding a suitable gas pressure to a bellows arranged in between the joint shaft and the lug of the calender or the lever in order to provide adjustability. The bellows is limited by the sealing strip and outside the bellows is guided liquid pressure which compresses the gas space smaller. The gas space can thus be adjusted by liquid volume by decreasing the gas space; more rigidity is achieved in the joint. According to another advantageous aspect the gas space is replaced by a porous, water-/oil-proof rubber plate the pores of which can be compressed by oil pressure. According to a further advantageous aspect a gas-binding elastic medium, e.g. a net (woven wire), in the gas bellow area is provided for keeping the gas in the bellows area.
By the rigidity adjustment according to this advantageous feature of the invention calender vibration can be prevented by changing e.g. the rigidity of roll support when vibration starts to occur. Preferably the pivot is adjusted to be relatively rigid.
In the following the invention is discussed in more detail by reference to figures of accompanying drawings.
In figure 1 one example of a multiroll calender according to the invention is schematically shown.
In figure 2 one example of schematically the attachment of an inner fly roll is schematically show.
In figures 3 - 8 is schematically shown an example of an advantageous aspect of the invention relating to the adjustable rigidity of a joint.
In the following description same reference signs designate for respective components etc. unless otherwise mentioned and it should be understood that the examples are susceptible of modification in order to adapt to different usages and conditions.
Figure 1 schematically shows an example of multiroll calender calendering two-sided fiber web grades which comprises two sets of calender rolls 10, 20, in which a fiber web W is calendered in the calendering nips between the calender rolls of the sets of calender rolls. Reference numerals 11 - 17 refer to those parts and components of first, upper set 10 of calender rolls and reference numerals 21 - 27 to those of second, lower set 20 of calender rolls. Calender frame 40 supports the sets 10, 20 of calender rolls by levers 45. The levers are pivotably attached to the calender frame 40 by joint. Loading cylinders of the calender rolls are indicated by reference 42. By reference sign 50 are indicated pivot points and thus joints of levers 45 supporting the calender rolls in the calender. By reference numerals 13, 23 a calender roll that is a resilient-surfaced calender roll is indicated and by reference numeral 12, 22 a calender roll that is a smooth-surfaced calender roll is indicated. Resilient-surfaced calender rolls 13, 23 are soft-surfaced, for example polymer-surfaced deflection, rolls and smooth-surfaced rolls 12, 22 are metal rolls, or thermo rolls either heatable and/or coolable thermo rolls. Guide rolls guiding the web are indicated by reference numeral 16, 26, fly rolls by reference numeral 15, 17, 25, 27. The two sets 10, 20 of calender rolls are located on top of each other. The upper roll 11 is a deflection compensated roll and lower roll 24 is also a deflection compensated roll. In calendering the web W is passed into a nip, i.e. calendering nip, formed between rolls 14, 12; 12, 13; 12, 11; 21, 22; 22, 23; 22, 24 that are pressed against each other, in which nip the web becomes deformed as by the action of temperature, moisture and nip pressure. In the calender the calendering nips are formed between a smooth-surfaced press roll 12, 22 such as metal roll and a roll coated with resilient material such as a polymer roll 13, 23. According to the invention the inner fly rolls 15, 25 of the sets 10, 20 of calender rolls of the multiroll calender are attached at the center of the joint 50 of the lever 45, advantageously fixedly such that the distance travelled by the web W between the closed nips of the calender does not cause web tension changes when the set of rolls moves up or down.
In figure 2 is schematically shown the attachment according to the invention in which inner fly roll 15, 25 is attached at its each end to the pivot hole 46 of the corresponding lever 45 of the calender roll, by this the center line CL of the roll 15, 25 corresponds to the center line of the pivot hole 46 for the joint of the lever 45.
In figures 3 - 8 is shown an example of the adjustable rigidity arrangement of a joint of a calender calender load cylinder 42 (fig. 1) in connection with a ball joint of a calender load cylinder. The lug 102 of the cylinder includes the adjustment elements 101 for rigidity. Elements for rigidity adjustment 101 are located in a fastening lug 102 of a ball joint 115 of the load cylinder 42, on both sides of the ball joint. In figure 4 is enlarged an adjustment element 101. Rigidity adjustment is based on a structure where there is a gap 110 between the pivot shaft 107 and the lug 102. To the gap 110 are located two sealing strip loops 103 which limit areas on the loaded and opposite side of the shaft. Inside the by sealing strips 103 limited gap 110 area are also located flat bellows 104 of the size of about the area. In the figure, between the seal areas 103 above and below the shaft 107 (the sides of the shaft) are located limiters 105 (fig. 6) to prevent the seals 103 from moving in the periphery direction when different pressures prevail in the areas.
The rigidity adjustment is based on guiding a suitable gas pressure to a bellows 104 arranged in between the joint shaft 107 and the lug 102 of the calender in order to provide adjustability. The bellows 104 is limited by the sealing strip 103 and outside the bellows 104 is guided liquid pressure which compresses the gas space smaller. The gas space can thus be adjusted by liquid volume by decreasing the gas space; more rigidity is achieved in the joint. It is possible to locate a sensor to measure the size of the gap X in order to focus the pivot load to the adjusting elements.
In the above the invention has been described by way of example with reference to the figures of the accompanying drawing. However many modifications and variations are possible within the inventive idea.

Claims

Multiroll calender for calendering a fiber web, particularly a paper or board web (W), which multiroll calender comprises at least one set of calender rolls (10, 20) and a frame (40), and the set comprising at least two calender rolls, in between of which a calendering nip is formed, and at least one fly roll, in which at least one calender roll is attached by a pivotable lever (45) by a joint (50) to the calender frame (40), characterized in, that at least one fly roll (15, 25) of the multiroll calender is an inner fly roll (14, 24) and that at least one inner fly roll (15, 25) is attached at the center of the joint (50) of the lever (45), advantageously fixedly, such that the distance travelled by the web (W) between the nips of the calender does not cause web tension changes when the set of rolls is moved.
Multiroll calender according to claim 1, characterized in that in the multiroll calender at least one of the joints (50) of the calender levers or calender load cylinder is provided with elements (101) for adjusting rigidity.
Multiroll calender according to claim 2, characterized in that the rigidity adjustment elements (101) comprise at least one bellows (104) arranged in between shaft (107) of the joint shaft and a lug (102) of the calender or a lever.
Multiroll calender according to claim 2, characterized in that the rigidity adjustment elements (101) comprise at least one sealing strip (103).
Multiroll calender according to claim 1, characterized in that in the multiroll calender comprises at least two sets of at least four calender rolls (10, 20).
Multiroll calender according to claim 1, characterized in that sets of calender rolls (10, 20) are vertical or inclined or horizontal.