The invention relates to a fastening member for a curved roll to be placed in a paper machine or a finishing machine for paper. The invention also relates to the use of such a fastening member as a fastening member for a curved roll. Furthermore, the invention relates to an arrangement and a method for controlling the vibration of a curved roll placed in a paper machine or a finishing machine for paper.

Background of the invention

In rolls of paper machines, harmful resonant vibration usually occurs at certain roll rotation speeds when running at a critical running speed. The critical speed means that the frequency of rotation of the roll is the same as the first specific frequency of its transverse vibration. Thus, during one rotation of the roll, an excitation force occurs once, causing strong vibration in the roll at its specific frequency. At said critical speed, the magnification coefficient of the excitation is the highest.

Even at speeds lower than the critical speed, narrow resonance points occur, in which the amplitude of the vibration clearly increases. For example, at a semi-critical speed, the frequency of rotation of the roll is half of its specific frequency. Thus, a disturbance occurring twice during a rotation of the roll will act as an excitation. Typical excitations at the semi-critical running speed include, for example, faulty bearings or variations in the bending stiffness of the roll. Similarly, problems are also caused by, among other things, the so-called third critical speed. In the present application, the critical speed refers to both the critical speed and all the critical partial speeds. Bypassing the critical speeds, that is, the so-called resonant vibration speeds, usually causes various problems affecting production capacity in the papermaking process, for example breaking of the paper web. Although this problem is recognized, it is often impossible to completely avoid these problematic speeds, because different rolls have different vibration properties, and furthermore, the conditions that cause vibration vary. Normally, however, the aim is to minimize the problems caused by vibration. Thus, avoiding the critical speeds that are most harmful to the process usually means that the running speed of the process must be decreased significantly, even by several hundreds of metres per minute lower than the optimal running speed, which decreases the efficiency of the machine.

When the rotation speed of the roll increases, the specific frequency of the roll should be increased so that the critical speeds would not be achieved. To some extent, this can be influenced by configurations of prior art either by reducing the mass of the roll or by increasing its stiffness; in other words, for example, by increasing the diameter of the roll, so that the stiffness of the roll increases relatively more than its mass increases. However, this kind of a configuration is difficult, inter alia, because of the increasing roll costs. Moreover, such a configuration is not suitable as a remedy for problems of already existing rolls. The present invention relates particularly to curved rolls in paper machines and finishing machines for paper. No functional solution to the vibration problems of such curved rolls has been found in the prior art, but the only way to avoid the problems caused by vibration has been to avoid forbidden running ranges, that is, these so-called critical speeds. As a result of avoiding said forbidden running ranges, it is often necessary, merely because of the problems caused by curved rolls, to slow down the speed of the paper machine from the optimal running speed of the machine without said problems. Such a drop in the running speed of the paper machine resulting from the vibrations of the curved rolls may be, for example, 200 to 300 m/min. As a result of such a drop in the speed, the production capacity of the paper machine is substantially decreased.

In the industry, there is thus a need for a solution to the problem of vibration of curved rolls in such a way that the speeds of the paper machine could be increased to the critical speed ranges and above them without various problems caused by the vibration of the rolls in the process, such as breaking of the paper web. Brief summary of the invention

It is an aim of the present invention to solve the above-mentioned problem of vibration in such a way that the speeds of curved rolls in a paper machine or finishing machines for paper can be increased without problems caused by the vibration of said rolls in the process. To achieve this aim, a novel solution of a fastening member will be presented, particularly for curved rolls. Furthermore, an arrangement and a method for controlling the vibration of curved rolls will be presented.

In the presented solution, the curved roll is fastened at its both ends by fastening members in such a way that said fastening members may form two separate supporting points at both ends of the roll, wherein said supporting points support the roll and keep it stationary. Preferably, the second supporting points of the curved roll are placed inside the actual fastening structure. Thanks to the properties of the new fastening solution, vibrations of the roll at critical speeds can be transferred to different speed ranges in such a way they are no longer harmful to the process. Thanks to this, it is no longer necessary to drop the running speed because of problems with the curved rolls. The fastening members according to the solution can be included not only in new curved rolls but also in existing curved rolls in both paper machines and finishing machines for paper; as a result, the running speed of the paper machine can be increased with reasonable investments. The fastening member for a curved roll, as well as the arrangement and the method for controlling vibrations of a curved roll, as presented, are based on controlling and adjusting the specific frequencies of the roll itself in such a way that the critical speed ranges of the roll are advantageously raised higher when the running speed approaches said critical speed ranges. These critical speed ranges are preferably restored after said critical speed range has been safely passed by. The fastening member according to the invention will be presented in claim 1. The arrangement for controlling the vibration of a roll will be presented in claim 6. The method for controlling the vibration of a roll, in turn, will be presented in claim 9. Description of the drawings

In the following, the invention will be described in more detail with reference to the appended drawings, in which Fig. 1 shows an arrangement according to one embodiment for controlling the vibration of a roll,

Fig. 2 shows a separate fastening member in an arrangement according to Fig. 1 , seen in a slanted side view, and

Fig. 3 shows the detailed structure of a fastening member according to Fig. 2.

Detailed description of the invention

In the present application, for the sake of clarity, fastening members of prior art for fastening a roll in its place will be called first fastening members 38 or first supporting points 38, and separate fastening members of a new type for adjusting the critical vibration ranges of the roll will be called second fastening members 39 or second supporting points 39.

It should be noted that in the present application, the terms first fastening members 38 and second fastening members 39 do not refer solely to fastening members 38, 39 of separate structures, but both of said fastening members 38, 39 can be integrated in a single fastening member unit. Thus, the term first fastening members 38 will refer to the first supporting points for fastening a curved roll, and the term second fastening members 39 will refer to the second supporting points used for vibration control in a system, in which one fastening member unit constitutes both supporting points 1 and 2. In other words, although separate fastening members 38, 39 will be discussed for clarity in the present patent application, it should be noted that the fastening members 38, 39 may be not only single fastening members but also partial units of a single fastening member.

A paper machine refers, in the present application, to a machine using raw materials to form a web of cellulose-based fibres and/or other fibres, which web may contain substantial amounts of, for example, various fillers, coatings, chemicals, and water. The final product obtained from the paper machine according to the invention is usually paper, paperboard, wood-plastic composite, or a similar product. Finishing machines for paper refer, in the present application, to all the machines which can be used for finishing a product made by a paper machine. Such machines include, for example, a supercalender, a coating unit, and a slitter-winder. Figure 1 shows an example embodiment of an arrangement to solve vibration problems of a curved roll. The figure shows a curved roll 37, first fastening members 38 for a curved roll, and second fastening members 39 for a curved roll. The curved roll 37 shown in the figure is a curved roll which is placed in a papermaking process and which may be installed, for example, in the press section or the drying section of a paper machine, or, for example, in a supercalender or a winder-slitter in a finishing machine for paper. Preferably, said curved roll 37 is placed in the press section of a paper machine, to be used as a spreader roll. The shaft of the curved roll 37, bent to be curved, is preferably stationary so that the shaft itself does not rotate, but the outer periphery of the roll rotates around said shaft. The main functions of the curved roll 37 are usually to adjust the tension and to spread the web running on the roll wider so that the web remains straight. The primary functions of the curved rolls 37 remain the same, irrespective of whether the subject of the tension adjustment and/or spreading is felt and/or paper.

The first fastening members 38 may be any fastening members suitable for the purpose and intended for fastening a curved roll. The first fastening members 38 fasten the curved roll 37 to the paper machine preferably substantially at the ends 37a of said roll, forming the first supporting points for said curved roll. Each of the single curved rolls 37 is kept substantially locked in its place by means of these first fastening members. These first fastening members 38 are not suitable for controlling problems of vibration of the curved roll. The second fastening members 39 refer, in the present application, to the members which form the second supporting points and are placed substantially at the ends 37a of the curved roll 37. As shown in Fig. 1 , the second fastening members 39 are preferably placed within the area between the first fastening members 38 of the curved roll 37, but still substantially in the area of the ends of the roll 37 in such a way that one second fastening member 39 is placed at each end 37a of the curved roll 37. The second fastening members 39 may also be placed the other way around with respect to the first fastening members 38, that is, in such a way that the first fastening members 38 of the roll 37 are placed within the area between the second fastening members 39. Furthermore, it is possible, although not equally advantageous, that the order of the fastening members is different at different ends 37a of the curved roll 37. The second fastening members 39, that is, the second fastening points of the curved roll 37, are used for stiffening the curved roll at its supporting points, when necessary, in such a way that the vibrations of the roll are substantially suppressed. The precise location of the second fastening members 39 with respect to the first fastening members 38 is usually dependent, among other things, on the structure, location and size of the curved roll 37. The central line 39a of the fastening members 39 is advantageously spaced by 20 cm from the centre line 38a of the fastening members 38, preferably by 20 to 50 cm and more preferably by 25 to 45 cm from the centre line 38a.

As mentioned before, the fastening members 38 and 39 may be partial units of a single separate fastening member, wherein a single separate fastening member is capable of forming two separate supporting points for the curved roll 37. This kind of a configuration is formed, for example, when a single fastening member forms two substantially separate supporting points for the curved roll 37. This kind of a configuration may also be, for example, the connecting of the fastening members 38 and 39 to each other by means of mounting plates or similar fastening solutions. Thus, the distance between the centre lines of the fastening members naturally refers to the distances between the central lines of the supporting points 38, 39. The control of the vibrations of the curved roll 37 by means of the presented fastening members is advantageously based on the fact that the locking of the second fastening members 39 is kept preferably released in those running situations in which the critical running speed of the curved roll 37 is not close. When approaching the critical running speed of the curved roll 37, both of the second fastening members 39 are locked around the preferably curved roll 37 substantially simultaneously, wherein said roll is stiffened in such a way that the critical running speed of said roll is shifted substantially higher than the previous critical running speed range. If the locks are kept closed during the whole running operation, for example a temperature rise in connection with start-up of the machine may cause problems due to thermal expansion.

After the critical running speed of the curved roll 37 has been shifted to a substantially higher running speed range than before, the speed of the curved roll can be safely increased higher than before in such a way that the running speed of the curved roll 37 reaches and, if necessary, exceeds the previous critical running speed of said curved roll that existed without the locking of second fastening members 39 and was to be bypassed. If the running speed of the curved roll is to be kept in this so-called critical running speed range to be bypassed, the fastening members 39 are kept locked as long as the running speed is to be kept in said range. However, if the running speed of the curved roll is to be increased even above this speed range, the locking of the second fastening members 39 can be released at the stage when said previous critical running speed has been safely exceeded.

By operating in the above-mentioned manner, a safe interval is constantly kept to any vibrations of said curved roll caused by the critical running speeds which would otherwise disturb the process. This vibration control can naturally be performed for each single critical running speed range of the curved roll 37 in such a way that all said critical running speed ranges can be bypassed safely. Furthermore, this adjustment of the critical running speed range can be performed separately for each single curved roll in the paper machine or finishing machine for paper in such a way that in spite of possible various vibration speeds of the curved rolls, the vibrations of all the curved rolls in the machine can be kept under control at all running speeds. If the running speed of the curved roll 37 is to be increased above one or more critical speeds, the locks of the second fastening members 39 are preferably locked each time when approaching the next critical running speed range and, in a corresponding manner, the locks of said fastening members 39 are preferably released when the running speed of the roll exceeds each "natural" critical running speed range without the second locking members. Thus, each so-called natural critical speed range can always be safely exceeded in such a way that each time it is also possible to determine, if the running speed is to kept at the speed achieved in this way or if the speed is to be increased further. Thus, in both of these alternatives, the vibrations of the curved roll 37 are still under control and do not disturb the process.

Said operation, that is, the locking of the second fastening members 39 of the curved roll 37 when approaching the critical speed of said roll 37 and the releasing of the locking of the second fastening members 39 after the bypassing of the critical speed, is performed preferably each time when approaching a critical running speed range, so that the curved rolls 37 can be safely run at any possible speeds of the paper machine or the finishing machine for paper. When operating in this way, the critical speeds of the curved rolls 37 which were previously particularly problematic, can be exceeded in a reliable and safe way.

The curved roll 37 is locked by the second fastening members 39 preferably symmetrically on both sides. If said roll 37 is locked asymmetrically, for example in such a way that it is locked with a second fastening member 39 on only one side of said curved roll 37, the asymmetricity of the fastening may impair the production efficiency, for example, by a more frequent need to replace the felts.

The locking and releasing of the second fastening members 39 during the process of papermaking or finishing of paper can be done either automatically or manually. The arrangement for preventing vibrations can be connected to the rest of the automation system of the machine, for example, in connection with new roll deliveries in such a way that the vibration preventing arrangement will automatically take care of bypassing the critical running speed points of the curved roll 37. Thus, the machine operators do not need to pay extra attention to these critical speed ranges.

In some cases, for example to include the presented vibration prevention arrangement in an old, already operating curved roll 37 in a machine in which sufficient automation is not readily available, it may be most cost-efficient to perform the releasing and locking of the second fastening members 39 manually. Thus, the machine operators lock and release the second fastening members 39 for the time of bypassing known, so-called natural critical running speeds of the roll.

The locking position that stiffens the curved roll 37, that is, the position in which said roll is advantageously locked by the second fastening members 39, can be preferably selected by two different methods. The first advantageous method is, in a way, to let the curved roll 37 itself find its natural position inside the second fastening members 39. This means that the curved roll 37 is set to move via the second fastening members 39 to the first fastening members 38, which first fastening members 38 lock the roll in its position in a preliminary way. Then, after the curved roll has been locked by the first fastening members 38, the position of the roll in this first locking with respect to the second fastening members 39 is seen. The curved roll 37 is then stiffened in this so-called natural position by the second fastening members 39 each time when these so-called natural critical running speed ranges are being bypassed.

The second fastening members 39 can also be placed behind the first fastening members 38, that is, on the side of the end of the roll 37. In this case, the roll 37 is naturally placed to move via the first fastening members 38 to the second fastening members 39. Similar methods can also be applied if the first fastening members 38 and the second fastening members 39 together form a part of a larger fastening member unit. Another advantageous method to select the locking position of the curved roll 37 is to place the curved roll 37 to move first in the above- mentioned way via the second fastening members 39 to the first fastening members 38 and to lock the roll by means of these first fastening members 38. After this, the curved roll 37 can be fastened, for the time of bypassing said so-called natural critical running speed ranges, by means of both the second fastening members 39 to a predetermined position which is not necessarily its so-called natural position. This is done by tightening the curved roll 37, locked by the first fastening members 38, to a desired position by means of the second fastening members 39 in such a way that said roll can substantially not vibrate. Usually, if there is no reason to the contrary, it is preferable to perform the selection and locking of the position of the curved roll 37 first in said manner so that the curved roll 37 is stiffened in its natural position.

Like in the first advantageous method for selecting the locking position, also in this second advantageous method for selecting the locking position the second fastening members 39 can be placed alternatively behind the first fastening members 38, that is, on the side of the end of the roll 37. Thus, the roll 37 is naturally placed to move via the first fastening members 38 to the second fastening members 39. Both methods can also be used in cases in which the first fastening members 38 and the second fastening members 39 are not separate fastening members but a part of a larger fastening member unit.

When the vibration control is performed symmetrically by using the presented arrangement, the curved roll 37 can be run at a desired running speed without the forces needed for stiffening said roll 37 causing negative effects on the roll 37 itself or on the felt or paper running on the roll 37, which is often the case if the curved roll 37 is stiffened by supporting it in an unbalanced way. The second fastening members 39 do not substantially affect the operation of the paper machine or the finishing machine for paper, except for their use to control the vibrations of the curved roll. This is due, among other things, to the fact that the second fastening members 39 are kept locked preferably during approaching and passing so-called critical running speeds. Because the fastening members 39 are preferably released both when the roll (e.g. its position) is being adjusted and when the operation is not close to the critical running speed ranges, the effect of the fastening members 39 on the operation of the roll will remain small, except for the vibration control.

Figure 2 shows a configuration according to an advantageous embodiment of the fastening member 39 of the arrangement shown in Fig. 1. The figure shows, among other things, a locking ring 8, an outer frame half 9, an inner frame half 10, three lock cylinders 40, and feet 41 of the fastening member 39.

The second fastening member 39 suitable for controlling vibrations of the curved roll 37 comprises at least one frame element. As shown in Fig. 2, the second fastening member 39 preferably comprises two frame elements, i.e. an outer frame half 9 and an inner frame half 10.

The position of the locking ring 8 is preferably between said frame halves 9 and 10, as shown in the figure. The locking ring 8 is preferably designed in such a way that the lock cylinders 40 are capable of locking the locking ring 8 tightly in a desired position against the curved roll 37. With said locking operation, the structure of the curved roll 37 becomes stiffer than before. The locking ring 8 advantageously comprises one integral and adjustable circumference. The locking ring

8 may comprise not only said one integral circumference but also several separate parts. This kind of a configuration is, for example, a locking member 8 formed of at least two separate components, in which the separate components advantageously have a wedge-like shape. When the second fastening member 39 is used for controlling vibration of the curved roll 37, the end 37a of said roll 37 is guided preferably to pass via the inside of the inner circumference of the locking ring 8. One fastening member 39 advantageously comprises at least one or two lock cylinders 40; more advantageously, their number is at least three to secure a sufficiently firm fastening to stiffen the curved roll 37 and to suppress vibrations. Preferably, the number of said lock cylinders 40 is precisely three. The lock cylinders 40 are preferably placed at substantially regular intervals, as shown in Fig. 2. An advantageous example of a lock cylinder series unit formed by three lock cylinders 40 and its more detailed structure is shown in Fig. 3.

The curved roll 37 can be stiffened by means of the second fastening members 39 not only by using the lock cylinder series 40 but also by using other kinds of locking members, such as, for example, a locking based on a pressure monitoring device.

The second fastening member 39 is fastened to its position in the paper machine or finishing machine for paper by any fastening members of prior art. The mounting of the fastening member 39 to the structure of the machine is performed advantageously at the lower part of the fastening member 39, preferably at the feet 41 of the fastening member 39.

Figure 3 shows an example of the more detailed structure of the second fastening member 39 of Fig. 2. The most important parts shown in Fig. 3, as well as in Figs. 1 and 2, are listed in Table 1. If nothing else is mentioned, the reference numerals of said Table 1 are found in at least Fig. 3.

It is obvious that the elements mentioned in Table 1 are only some possible alternatives for the components of the second fastening member 39. For this reason, the single elements mentioned in the table may naturally be replaced by other elements suitable for the invention without changing the idea of the invention. As an example, it can be mentioned that it is obvious that an Allen screw for example, could also be replaced by another fastening member of prior art.

The example of Fig. 3 shows, among other things, the three lock cylinders 40 according to an advantageous embodiment, with some of their possible components. Connected in series, these three lock cylinders 40 constitute a lock cylinder series that fastens the locking ring 8 firmly to the curved roll 37 in such a way that said roll 37 is stiffened to a desired extent.

Advantageously, the detailed structure of the lock cylinder 40 contains, among other things, a cylinder 16, a piston 3 with its seal 35, a locking arm 4, 11 , as well as a guide bushing 5. In this example, a lock cylinder series of the single lock cylinders 40 is formed by connecting pipes 17 connected to the lock cylinders 40 by connectors 21.

Advantageously at least one, preferably exactly one of the lock cylinders 40 is provided with a cogging. The cogging can be implemented, for example, by providing the lock cylinder with a stepped locking arm 11 comprising a spring cotter 18. This cogging arrangement may be added in any one of the lock cylinders 40 of the fastening member 39, in one or more of said lock cylinders 40.

The purpose of the cogging is to fix the locking ring 8 in a rigid and sealing manner around the curved roll 37 so that said roll 37 becomes stiffer. Another aim of the cogging is to provide said fixing in such a delicate way that the process of fixing the curved roll 37 does not disturb the operation of said roll 37 and thereby the operation of the paper machine or the finishing machine for paper.

Advantageously, at the initial stage of the process of stiffening the curved roll 37, the locking ring 8 is guided by the cogged lock cylinder 40a and the other lock cylinders 40 following the cogged lock cylinder to be firmly fixed to the curved roll 37. When all the lock cylinders 40 of the lock cylinder series stiffen the curved roll 37 via the locking ring 8, the whole lock cylinder series is tightened firmly around the locking ring 8, tightening the curved roll 37 in its place so that the curved roll is stiffened to the desired position inside the locking ring 8. Thus, thanks to the stiffening of the curved roll 37, the critical running speed ranges of said roll are upshifted to higher running speeds than before.

In more detail, the process of stiffening said curved roll preferably proceeds as follows:

1. The cogs of the cogged lock cylinder 40a are gradually tightened so that the locking ring 8 is moved by said cogged lock cylinder against the curved roll 37. This is performed by applying a relatively small force.

2. After the cogged lock cylinder 40a has moved the locking ring 8 against the curved roll 37, the resistance introduced by said roll will become so heavy that said cogged lock cylinder 40a will start to move the other, more lightly movable lock cylinders 40 which are not yet affected by the resistance introduced by said roll 37.

3. The cogged lock cylinder 40a will pull all these more lightly moving lock cylinders 40 steadily against the locking ring 8, which locking ring 8 is thereby fixed steadily around the curved roll 37, its end 37a. The moving of the more lightly moving lock cylinders 40 is continued until each lock cylinder 40 encounters an essentially equal resistance caused by the curved roll 37, the resistance being at least equal to the resistance according to point 1.

4. When the resistance encountered by each lock cylinder 40, 40a, caused by the curved roll 37, is at least equal to the resistance introduced by said roll 37 under point 1 , the cogged lock cylinder 40a will continue the simultaneous tightening of each lock cylinder 40, 40a around the locking ring 8. This goes on until the locking ring 8 has fastened the curved roll 37 by a desired force to be sufficiently stiff. 5. As a result, the locking ring 8 has been tightened around the end 37a of the curved roll 37 in such a way that the curved roll 37 has been substantially stiffened. The operations of guiding the second fastening members 39 placed at both ends 37a of the curved roll 37 are preferably integrated in such a way that said second fastening members 39 at both ends 37a of the roll are applied, both in the releasing operation and in the locking operation, substantially simultaneously. Thus, the curved roll 37 is stiffened and released by both fastening members 39 simultaneously, whereby problems possibly caused by asymmetricity are avoided in the process.

As mentioned earlier, the locking ring 8 is advantageously placed between the two frame parts of the fastening member 39, the inner frame half 10 and the outer frame half 9. The locking ring 8 preferably "floats" in its position between these frame halves. Thus, the locking ring is moved relatively lightly by the cogged lock cylinder 40a into the so-called natural locking position of the curved roll 37, in those cases in which said curved roll 37 is to be stiffened in this so-called natural position. If the roll is to be stiffened in another predetermined position, the locking ring 8 is moved in connection with the locking to the location required by this predetermined position. So that the locking position for the locking ring could be selected in a sufficiently flexible way, the clearance for the locking ring 8 is advantageously at least 1 mm, more advantageously at least 2 mm. A suitable clearance is often, for example, 1 to 5 mm; most often, a sufficient clearance is already 2 to 4 mm. Thanks to possibility of adjusting the location for the locking ring 8, the position and stiffness of the curved roll can be adjusted without a need to move the position of the fastening member 39 itself.

The presented fastening members 39 are used to influence the specific frequency of the curved roll 37 in such a way that the vibrations originating from the roll's own structure will be suppressed. The presented second fastening members are suitable for use for controlling vibrations of all curved rolls both in paper machines and in finishing machines for paper. In solving problems related to production efficiency, they are normally most efficient when used in connection with curved rolls in the press section of a paper machine.

The presented configuration is suitable for application in connection with various curved rolls, irrespective of the length, diameter or radius of curvature of said roll. Because the second fastening members release the second fastening of the curved roll preferably each time when the running speed of said curved roll is not in the range of the critical running speeds, any harmful effect possibly caused by the operation of these second fastening members on the roll will be minimized in such a way that the harmful vibration caused by said roll can be simultaneously prevented. Furthermore, problems caused by asymmetricity are avoided in the fastening of the curved roll, because the curved roll is preferably always fastened substantially symmetrically in such a way that both the second fastening members operate at the same time.

The presented configuration can be installed not only in new curved rolls in connection with their mounting but also in curved rolls already existing in paper machines or finishing machines for paper. Thus, the presented second fastening members are installed afterwards in curved rolls already existing in a paper machine. Thanks to this, it is possible to achieve a new class of running speeds with these old curved rolls. The presented fastening member suitable for adjusting vibration can be formed, not only by the methods mentioned in the examples, but also by using other suitable components. The invention is thus not limited solely to the examples presented in Figs. 1 to 4 and in the above description, but the invention is characterized in what will be presented in the following claims.