FI119851B - Method for attenuating periodic vibration of a fiber web machine - Google Patents

Description

TECHNICAL FIELD 5. Method of attenuating periodic vibration of a fiber web machine

The invention relates to a method for damping the periodic vibration of a fiber web machine, the fiber web machine comprising a plurality of nip rolls adjacent to each other in the compression direction, wherein two adjacent nip rolls each form a roll nip comprising the step of determining the vibration of at least one of the first soft-surface nip rolls in at least one roll nip.

BACKGROUND ART

In soft nip contacts of fiber web machines such as multi-roll calenders, soft calenders, coating machines, and press rolls, periodic load variations have been observed with the occurrence of barring. When Barring is present in the nip process, transverse lines of varying gloss visible to the fiber web visible to the fiber web can be observed. In this case, the web may no longer be suitable for further use and may need to be removed as a waste. Said disturbed load variation typically occurs at 200 to 800 Hz. These frequencies have not previously been able to be actively influenced by gear or intermediate shaft drives.

25

There are known gaps and elasticities in the gears and intermediate shafts of roller transmission systems that make it difficult to make rapid changes from drive to roller force. In addition, parts of the transmission systems, such as the number of teeth 30 of the bearing elements or gears, can generate excitations that contribute to the generation of problematic interference frequencies in the nip process between the rolls of a fiber web machine.

2

DE 196 01 293 A1 discloses a method and apparatus for treating a web of material. The publication seeks to avoid the appearance of transverse shiny lines or barring. As a solution, the distance between the nip and the preceding take-off roll 5 is changed from time to time.

DE 101 33 888 C1 discloses a method for using a calender and a calender. The publication seeks to improve the service life of flexible surface rolls. Hereby, the vibration of at least one roll is determined continuously and displaced by 10 of these rolls in a transverse direction relative to the compression direction of the calender, in a manner dependent on the specified vibration.

DE 101 33 890 Cl discloses a method for using a calender. The publication seeks to improve the service life of a flexible surface roll. In this case, when the barring-15 pattern is present on the surface of the soft-surface roll, the wavelength of the barring pattern is determined and this soft-surface roll is displaced in a transverse direction relative to the compression direction of the calender in a manner dependent on the determined wavelength.

For example, calenders have three types of nip rolls: heated thermo rolls, deflection compensated rolls, and polymer-coated rolls. Normally, you need to replace thermo rolls and other hard surface rolls, for example, about once a year. Instead, soft roller coatings wear out faster and need to be replaced more frequently, typically, for example, two to six times a year. When the barring effect occurs, the coatings of such soft-surface rollers 25 may be damaged much faster than the above, for example, in days or weeks.

SUMMARY OF THE INVENTION

The main features of the method according to the invention are set forth in the characterizing part of claim 1.

3

According to the method of the invention, when calendering a fiber web on at least one roll nip of a fiber web machine, at least the first soft-surface nip roll of the nip rolls of this nip is rotated directly by an AC motor coupled to this soft-surface 5 nip roll. The rotational frequency and rotational phase of this AC motor are determined and an additional current is applied to the basic current frequency of this AC motor at a frequency of oscillation that is dependent on said first oscillation of a soft-surface nip roll.

10

According to another preferred embodiment of the invention, when calendering the fiber web in at least one roll nip of the fiber web machine, the second hard surface nip roll of this nip is rotated directly by the AC motor is dependent on the vibration determined by said first soft-surface nip roll.

According to a preferred third embodiment of the invention, when calendering a fiber web on at least one roll nip of a fiber web machine, the second soft-surface nip roll of this nip is rotated directly by an AC motor connected to this soft surface nip roll; which is dependent on said oscillation of at least the first soft-surface nip roll.

The solution according to the invention is suitable for reducing and eliminating the periodic oscillation or barring effect in the soft nip contacts of fiber web machines such as multi-roll calenders and soft calender rolls.

4

The mechanical damping of the power transmission of the calender rolls can be provided by 5 motors directly coupled or mounted to the roll between the drive nip. It is possible to transmit the desired torque change at high frequency to the nip process.

BRIEF DESCRIPTION OF THE FIGURES

10

The invention will now be explained in more detail by way of exemplary embodiments with reference to the accompanying schematic drawings.

Figure 1 schematically illustrates a fiber web machine, which in Example 15 of the figure is a multi-roll calender in which the web is calendered at all nips between the calender rolls with a web feed from top to bottom.

Figure 2 shows a pair of rolls of a fiber web machine and a first embodiment of a roll drive directly coupled to the axis of the first soft-surface nip roll of a pair of rolls 20.

Figure 3 shows a pair of rollers of Figure 2 viewed from the direction of the ends of the nip rolls.

Figure 4 shows a pair of rolls of a fiber web machine and another exemplary embodiment of a roll drive directly coupled to the axis of the first soft-surface nip roll of the pair of rolls. The shaft of the second soft-surface nip roll is also directly connected to a roll drive.

Figure 5 shows a pair of rollers of Figure 4 viewed from the direction of the ends of the nip rolls.

30 5

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In papermaking, the paper web is completed by calendering as a finishing operation, in which the web is passed through one or more 5 consecutive calender rolls, for example in a multi roll calender or a soft calender. Calendering affects the thickness of the web and the surface quality by means of a line load acting on the nip between the calender rolls. In addition, the calendering result is influenced by temperature and humidity of the web. Line load, temperature and web humidity achieve the desired 10 calendering results by adjusting the above quantities.

Calendering can be done both on-line and off-line. In multi-roll calendars, the calender roll nipples are formed as a stack between the stacked calender rolls. It is also known to place 15 roll stacks in an inclined position. The web to be calendered passes through the nipples in a meandering manner so that it is brought e.g. from the beginning of the roll stack and leaves the roll stack at the end thereof.

Figure 1 schematically illustrates a fiber web machine 10 having ten nip rolls 20-11-20 and nine nipples N1-N9. The fiber web machine 10 of Figure 1 is one example of a multi-roll calender, but the method of the invention can also be applied to a soft calender.

In Figure 1, the roll of the fiber web machine 10 includes a top roll 11 and a lower roll 20 25 and eight intermediate rolls 12-19 arranged between the upper and lower rolls, the upper, lower and intermediate rolls forming the nip rolls 11-20 of the track. In the multi-roll calender, the fiber web to be calendered is denoted W. The intermediate rolls 12-19 are mounted on the body of the multi-roll calender, for example, by means of support and load arms that pivot about the joint, not shown. The multi-roll calender 10 shown in the figure has a vertical track, but the track, or part of the track, may equally well have 6 non-vertical tracks.

In the schematic side view of the fibrous web machine 10 shown in Figure 1, the fiber web W is calendered in all nipples 5 between the calender rolls with the web extension from top to bottom. The fibrous web W is guided through an output roller 21 to the top nipple N1 and further through the other nipples N2-N8 and finally out of the bottom nip N9. Between nipples N1-N9, web W is taken off the roll surface by means of take-out rolls 22, 23, 24, 25, 26, 27, 28 and 29. For reasons of clarity 10, the support roller support devices either in the roller bearing housings or in the calender body are not shown. After the track, the fibrous web W can be further guided as needed, for example by roll 30.

Figures 2 to 5 show adjacent rolls of a fibrous web machine 10, a first roll and a second roll forming a nip N1 between them. In Figures 2 and 3, the first roll 1 is a soft surface roll and the second roll 2 is a hard surface roll. In Figures 4 and 5, the first roll 1 and the second roll 1a are both soft surface rolls. The roll nip N1 shown in Figs. 2-5 may be located at one of the nip N1-N9 shown in Fig. 1, and there may be more than one, for example two or three, nipples shown in the roll nip N1. In the nip, N1 can be, when closed, with the fibrous web compressed in the nip and rolls 1,2; Calibrate the fiber web as the 1.1a rotates. 2-5, each pair of rolls forms a part of a fibrous web machine for calendering a fibrous web such as paper. Figures 2-5 do not show, for the sake of clarity, the fibrous web and the take-up rolls required for the pair of rolls or other rolls required for guiding the web.

When the transmission of the calender rolls is arranged according to the invention, the mechanical damping of the transmission of the rolls 1,2, la can be provided directly by the AC motors 6, 6a coupled or mounted to the roll 1,2, la significantly lower than the conventional shaft and gearbox gears 6, 6a . Thus, it is possible to transmit to the nip process at high frequency the desired change in torque of at least one roll.

In preferred embodiments of the invention, the permanent magnet synchronous motor 5 PMSM is preferably used as the AC motor, which can provide high torques and high power densities compared to conventional induction motors.

A method for attenuating the periodic vibration of a fiber web machine 10 comprising a plurality of nip rolls 11-20 adjacent to each other in the compression direction 10, wherein two adjacent nip rolls each form a roll nip N1-N9 consisting of a first nip roll 1 and a second nip; la, which is a hard surface roll 2 or a soft surface roll la, comprises the following steps: the soft-surface nip roll 1 is rotated directly by the AC motor 6, 20 coupled to this soft-surface nip roll 1, - determining the rotational frequency and rotation phase of this AC motor 6, 1 dependent on the specified vibration F.

25

To the base current frequency F0 of the first soft-surface nip roll 1 using AC nozzle 1 and also to the base current frequency F0 of the second hard-surface nip roll 2 4a (not shown) or to the second AC motor 4a 30 using a soft surface nip roll 1a. a basic current frequency Fo (Figs. 4 and 5) can be supplied by a superposition principle with an additional current at a desired oscillation frequency Fi (barring frequency) which is dependent on said 8 oscillations F of the first soft-surface nip roll 1. The object is to provide a barring disturbance lie opposed to a vibration frequency which is thus in the opposite phase to the barring disturbance thereby providing active vibration damping in the fiber web machine 5 10. The phase of the auxiliary input current vibration frequency is adjusted by adjusting the AC motor 6; 6a used by the nip roll 1; 1.2; The rotation frequency of 1.1a changes so that the barring sound or the barring vibration from the nip process begins to dampen or diminish.

It is a prerequisite for active damping of the invention that at least one of the first soft nip rolls 1 of the fiber web machine is rotated directly by an AC motor 6 connected to this nip roll which acts as a torsional vibration actuator in addition to normal operation. It may also be advantageous to use the second hard nip rolls 2 and the second soft-surface nip rolls 1a directly on such another nip roll 2; 1A, which operates in addition to the normal operation of the oscillating suction device a. Of course, one fiber web machine 10, such as a multi-roll calender and a soft calender, may have a plurality of soft-surface nip rolls 1, 1a, which may be rotated directly by an AC motor connected to each nip roll.

20

Preferably, an internal frequency and phase analysis of each AC motor 6, 6a is determined to analyze and control the appropriate frequency and phase to determine the rotational frequency and rotation phase of this AC motor 6, 6a, and preferably a microphone or vibration sensor external to each AC motor. determining the vibration F. of at least one of the first soft-surface nip rolls 1 in the at least one roll nip N1; the second nip roll 2 of the telanip N1; a external microphone or vibration sensor external to the direct-actuating AC motor may determine at least one of the second nip rolls 2 in said at least one roll nip N1; The external microphone 30 or vibration sensor may be mimicked inside or outside the fiber web machine.

9 In practice, connecting the AC motor 6, 6a directly to the nip roll means increasing the weight on the nip roll support structures. Thus, the mechanical properties of the supporting structures, such as the load-bearing capacity and the stiffness of the 5-arm arms in the arrangement of the embodiments of the invention, have been improved. Special consideration should be given to the moments of acceleration and deceleration of the nip roll which are significant in design because they are significantly higher than those of active damping of the nip roll.

10

Figure 2 shows a first exemplary embodiment of an AC motor 6 directly coupled to the axis 3 of a first, soft-surface nip roll 1 of a roll pair of fiber web machines 10, although an AC motor is not connected to the shaft 3a of the second hard surface nip roll 2. Only one end of the nip roll pair is shown. At one end, the pair of rollers 1, 2 may also be equipped with an AC motor (s) or without an AC motor. The nip rolls 1, 2 are bearing at both ends from their shafts 3, 3a to the bearing housings 4, 4a.

In the exemplary embodiment of Figures 2 and 3, the load-bearing supporting and loading arms 5, 5a of the nip roller 1, 2 and of the AC motor 6 and auxiliary devices such as possible take-off rollers are mounted on the unshown body of the fibrous web machine 10, e.g. The bearing housings 4, 4a are secured to the outside of the support and load arms 5, 5a 25 from the direction of the nip roll shell, and an AC motor acting directly on the shaft 3 of the first nip roll 1 is mounted inside the support and load arms 5, 5a. Preferably, the body of the AC motor 6, comprising a stator portion of the AC motor, is secured to a support and loading arm 5 of the first nip roll 1 inside it. The rotor of the AC motor 6 is then attached, for example, by a wedge connection 30, to the shaft 3 of the first nip roll.

10

Fig. 3 is a view of a pair of rollers of Fig. 2 viewed from the direction of the ends of the nip rolls 1,2. Figure 3 illustrates that the compression plane of a pair of nip rolls may be horizontal. Of course, the pair of rollers shown in Fig. 3 may also be formed by two soft-surface nip rolls 1; la.

5

Figures 4 and 5 show a pair of rolls of a fiber web machine 10 and another exemplary embodiment of an AC motor 4 connected directly to the axis of the first soft-surface nip roll 1 of the pair of rolls. In the second pair of rollers, in this embodiment, the shaft 10 of the soft-surface nip roll 1a is also directly connected to the AC motor 4a.

In the embodiment of Figs. The bearing housings 4, 4a are fixed in the direction of the sheath of the nip rolls, inside the support and loading arms 5, 5a and directly on the first and second nip rolls 1; 2 for shafts 3; 3a acting AC motors 6; 6a is mounted inside the bearing housings 4, 4a. Preferably, AC motors 6; 6a, the bodies including the stator portion 20 of the AC motor being secured to respective nip roller bearing and loading arms 5; 5a inside. AC motors 6; The rotors 6a are then attached, for example, by means of wedges, to the shafts 3 of the respective nip rolls; 3a.

Fig. 5 is a view of a pair of rollers of Fig. 4 viewed from the direction 25 of the ends of the nip rolls 1, 1a. Figure 5 illustrates that the compression plane of a pair of nip rolls may be non-horizontal. Of course, the pair of rollers shown in Figure 5 may also be formed by a soft-surface nip roll 1 and a hard-surface nip roll 2.

As will be apparent to one skilled in the art, such stiffening is also possible 30 that the nip roll 1, 1a, 2 is mounted on its shafts 3, 3a to the bearing housings 4; 4a, such a bearing housing is attached to a fiber web machine on a pivotable load and support arm 5, 5a viewed from the inside of the nip roll casing, wherein the body of the AC motor 6, 6a including the stator is secured to the load and support arm 5, 5a , 3a via a rotor of an attached AC motor.

5

Further, it is possible that the nip roller 1, 1a, 2 is mounted on its shafts 3, 3a to the bearing housings 4; 4a, such a bearing housing being attached to a fiber web machine on an articulated load and support arm 5, 5a as viewed from the direction of the nip roll casing, wherein the body of the AC motor 6, 6a comprising a stator 10 is attached to the bearing housing 4; 4a to the outside thereof and the nip roll is rotated through the rotor of the AC motor fixed to its shaft 3, 3a.

Only some preferred embodiments of the invention have been described above and it will be apparent to those skilled in the art that they may be subject to numerous modifications within the scope of the appended claims.

Claims (14)

A method for damping the periodic oscillation of a fiber web machine (10) comprising a plurality of nip rolls (11-20) adjacent to each other in the compression direction, wherein each of the two adjacent nip rolls forms a roll nip (N1 ... N9) formed by the first nip roll 1) which is a soft surface and a second nip roll (2; la) which is hard surface (2) or soft surface (la), the method comprising the steps of: 10. determining at least one roll nip (N1) of at least said first soft surface nip roll (1) oscillation (F), characterized in that the method further comprises the following steps: - at least one of the nip rolls 15 (1) of the nip rolls of this nip is rotated directly connected to this soft nip roll (1) With the AC motor (6), - determine this A The rotation frequency and the rotation phase of the C motor (6), wherein - an additional current is applied to the basic current frequency (Fo) of this AC motor (6) at a vibration frequency (Fi) of 20 said first oscillations (1). A method according to claim 1, characterized in that it further comprises the steps of forming a fibrous web on at least one roll nip (N1) of the fibrous web machine (10) by rotating a second hard nip roll (2) of said nip directly with an AC motor connected to said hard nip roll (2). (6a), - determining the frequency of rotation and the rotation step of this AC motor (6a), whereby - an additional current at the base current frequency (Fo) of this AC motor (6a) is provided at an oscillation frequency (Fi) from said at least first soft-surface nipple dependent on the specified vibration (F). A method according to claim 1, characterized in that it further comprises the steps of - rotating a second soft-nip roll (la) of this nip directly on the AC-coupled to this soft-surface nip roll (la) in at least one roll nip (N1) of the fibrous web machine (10). motor (6a), - determining the rotation frequency and rotation step of this AC motor (6a), whereby an additional current is applied to the base current frequency (Fo) of this AC motor (6a) at an oscillation frequency (Fj) from said at least first ) dependent on the specified vibration (F). Method according to one of claims 1 to 3, characterized in that an AC motor (6) directly driving the first nip roll (1) of said at least one roll nip (N1) is provided with an internal frequency and phase analysis to determine the 6) rotation frequency and rotation phase. 20 Method according to one of Claims 1 to 4, characterized in that the second nip roll (2; 1a) of said at least one roll nip (N1) is rotated directly by an AC motor (6a) connected to this nip roll (2) and provided with internal frequency and Phase analysis to determine the 2nd rotation frequency and rotation phase of this AC motor (6a). Method according to one of Claims 1 to 5, characterized in that an external microphone or vibration sensor 30 is provided on the outside of the AC motor (6) directly driving the first nip roll (1) to the fiber web machine to determine at least one roll nip (N1) vibration (F) of said first soft-surface nip roll (1). Method according to one of Claims 1 to 6, characterized in that an external microphone or vibration sensor is provided on the outside of the AC motor (6a) directly driving the second nip roller (6a) in the fiber web machine 5 to determine at least one roll nip (N1). at least vibration (F) of said second nip roll (2; 1a). Method according to one of Claims 1 to 7, characterized in that the nip roll (1, 1a, 2) is mounted on its shafts (3, 3a) to a bearing housing (4; 4a), such a bearing housing being fixed to a load and support arm 5.5a) externally viewed from the direction of the nipple roll casing, wherein the body of the AC motor (6, 6a) including the stator is mounted on the load and support arm (5, 5a) on the inside thereof and rotated by AC actuated to its 15 axes (3, 3a). motor through the rotor. Method according to one of Claims 1 to 7, characterized in that the nip roll (1, 1a, 2) is mounted on its shafts (3, 3a) to a bearing housing (4; 4a), such a bearing housing being mounted on a load and support arm 20 5, 5a) as viewed from the direction of the nipple roll shell, wherein the body of the AC motor (6, 6a) including the stator is mounted on the load and support arm (5, 5a) outside and rotated by the AC motor mounted on its shaft (3, 3a). rotor. Method according to one of Claims 1 to 7, characterized in that the nip roll (1, 1a, 2) is mounted on its shafts (3, 3a) to a bearing housing (4; 4a), such a bearing housing being fixed to a load and support arm (5) , 5a) as viewed from the direction of the nipple roll shell, wherein the body of the AC motor (6, 6a) including the stator is mounted in a bearing housing (4; 4a) on the inside thereof and rotated by an AC motor rotor mounted on its shaft (3, 3a). Method according to one of the preceding claims 1 to 7, characterized in that the nip roll (1, 1a, 2) is mounted on its axles (3, 3a) to a bearing housing (4; 4a), such a bearing housing being fixed to a load and support arm (5) 5.5a) externally viewed from the direction of the nip roll shell, wherein the body of the AC motor (6, 6a) including the stator is attached to the bearing housing (4; 4a) outside and rotated by the AC motor rotor mounted on its shaft (3, 3a). Method according to one of the preceding claims 1 to 11, characterized in that a permanent magnet synchronous motor (PMSM) is used as the AC motor (6, 6a). Method according to one of Claims 1 to 12, characterized in that the fiber web machine (10) is a multi-roll calender. Method according to one of the preceding claims 1 to 12, characterized in that the fiber web machine (10) is a soft calender.