The invention relates to a foundation arrangement for a paper or board machine or equivalent according to the preamble of claim 1.

Fibrous web machines, in particular paper and board machines, include different parts and devices, for example, finishing devices, such as calenders, which are needed for glazing and smoothing the surface of a paper web. There are many types of paper or board machine parts and devices, for example, calenders, depending on the surface quality desired for the web and on the intended future use of the web. From the viewpoint of the performance of a paper or board machine part/device, for example, a calender, it is important that support on the building and, in particular, on the ground underneath it is as stable as possible both dynamically and statically. In this connection, by dynamic stability is meant the fact that disturbing dynamic excitation is not transmitted through the ground and the damping characteristics of the ground are stable, and by static stability is meant the fact that the ground carries the loads imposed on it while keeping its shape. In prior art applications, one big problem has been to make the foundation sufficiently stable because of unfavourable or unknown ground conditions. Unstable support causes problems, among other things, in that disturbing vibration arises in the running situation and a permanent change in the position of support may occur.

One problem with prior art paper or board machines has also been that when different parts/devices are supported on the same foundation, the vibrations of the different parts/devices may have caused interactions of vibrations, which may have resulted in a periodic or chaotic vibration behaviour of the entire machine.

With respect to the state of the art, reference may be made to European patent EP 0 972 879 disclosing a calender assembly for webs of a paper or similar material, which calender comprises a frame which is supported at its bottom part and which includes at least five rolls mounted on the frame, which rolls form nips between themselves and have axes that lie in the same plane extending substantially parallel to the frame, which common plane is at an angle to the horizontal direction, which, in addition to a lower support surface, has an upper support surface, by means which it can be supported on a lower mounting surface attached to the building and on an upper mounting surface attached to the building. However, by means of this prior art arrangement it is not possible to the above- mentioned problems in calendering arising from unfavourable or unknown ground conditions because the attachment of the calender is fixed both dynamically and statically.

As known in the state of the art, vibration at a frequency of, of example, 20 Hz occurs in the bases of parts/devices of paper or board machines, such vibration in high structures, such as, for example, multiroll calenders, causing premature fatigue of structures and, at worst, process disturbances and breakage of structures. As known in the state of the art, attempts have been made to solve this problem by mounting passive dampers in the upper part of a part/device having a high structure in a paper or board machine, which are tuned to a given desired frequency, typically from 7 to 9 Hz. Using this arrangement, attempts have been made to control the machine-direction vertical vibration of the above-mentioned frequency in the part/device of the paper or board machine itself, but it has not made possible it to control vibrations in an overall manner.

It has required high costs to make the ground and foundations favourable. With increasing machine speeds, the demands imposed on the foundation in the conventional mode of attaching a machine to the foundation further increase the building costs.

An object of the invention is to provide a foundation arrangement for a fibrous web machine, such as a paper or board machine, by means of which arrangement the drawbacks of the arrangements known from the state of the art are eliminated or at least minimized. An object of the invention is to provide a foundation arrangement for a paper or board machine or equivalent, in which arrangement the problems associated with unfavourable or unknown ground conditions in sufficiently stable support both dynamically and statically can be eliminated or at least minimized.

An object of the invention is also to provide a foundation arrangement that takes into account vibrations in an overall manner.

An object of the invention is to provide a foundation arrangement that enables control of the vibrations of the part/device itself cost-effectively and in a structurally simple manner.

With a view to achieving the objects described above and those coming out later, the foundation arrangement for a paper or board machine or equivalent according to the invention is mainly characterized by what is stated in the characterizing part of claim 1.

The foundation arrangement for a paper or board machine or equivalent in accordance with the invention is accomplished such that the foundation is made on a massive solid base, for example, a concrete slab. The massive base is preferably reinforced concrete, which can be of a damping material in its material composition, and its weight is, for example, twice the weight of a part or device, for example, a calender in a paper or board machine or equivalent depending on the static bearing capacity of the ground. The massive base is such as to form rest mass for the foundation of the part or device of the paper or board machine, which rest mass in itself contains no excitations. The base is in turn supported on the foundations of the building by means of a moving coupling. The moving coupling

allows horizontal and vertical movement, static alignment taking place using elements controllable in a vertical direction by means of hydraulic actuators. The moving coupling enables the part/device of the paper or board machine to be kept in a desired position although changes, such as uneven sinking, would occur in the foundations. Control of the dynamic damping used in the invention is based on identification of the vibration of a part/device of a paper or board machine, such as a calender, and on minimization of such vibration using a change in the friction characteristics of a viscous damper. The dynamic properties of the spring and damping elements used in connection with the invention have been controlled and are controllable to be damping the vibration of the calender.

In accordance with one advantageous application of the invention, different parts/devices, each or the desired ones, of a fibrous web machine, for example, a paper or board machine, are provided on a separate foundation of their own in accordance with the invention, thereby enabling the possible interactions of the vibrations of the different parts/devices to be eliminated.

In connection with the invention, an underneath mounting damper is advantageously used which comprises typically four, at least three underneath mounting damper cylinders placed at corners of a massive base, i.e. a foundation slab. The slab is locked mechanically by means of the cylinders of the underneath mounting damper when machine alignments have been made. Underneath or on top of the cylinder of the underneath mounting damper there is a spring element whose spring constant is adjusted such that operation in the running situation is in an overcritical range. The spring element can be of metal or it can be an elastomer- and gas-containing spring element, so that the spring constant can be changed by means of the pressure of the gas. In addition, the underneath mounting damper arrangement includes a variable viscoelastic, energy-dissipating damper, which is controlled to minimize the running speed and the measured dynamic motion.

In connection with the invention, sinking is corrected advantageously by means of a hydraulic cylinder such that the part/device of a paper or board machine, such as a calender, achieves its original mounting position. When the position has been achieved, the cylinder is locked mechanically. Conventional levelling measurements are used for position setting. Static position can be monitored, for example, by laser sensor arrangements.

In connection with the invention, control of overall vibration is improved in an advantageous manner, in particular, control of the vibration arising from the machine's (calender's) own operation, by providing the base with semi-active mass dampers, whereby the self-excited horizontal and vertical vibrations of the part/device of the paper or board machine can also be brought under control and the vibrations can be brought under control in an overall manner.

In connection with the invention, a semi-active mass damper provided with a variable stiffness K is mounted on a base, the variable stiffness of the mass damper being typically produced by a pneumatic spring element. The operation of the mass damper is based on the fact known per se that a mass placed on support of a spring and a damping arrangement vibrates at its resonant frequency in a phase opposite to the excitation occurring at the same frequency in its base. The resonant frequency of the spring-damper- mass system is determined, as simplified, as follows:

f ^L _r r _P e _S s = V K/ m Hz

where K is stiffness (spring constant) (kg/s ² ) m is a vibrating mass (kg)

Damping shall be reasonably small in order that the resonance motion of the semi- active damper may arise but sufficient so that the damper device is not broken.

The vibration hampering the base is converted into dissipation heat in the damping element.

In a horizontal mounting arrangement, the above equation can be written:

where g is the acceleration of gravity (m/s ² ) s is the compression caused by mass m in the spring (m)

In that case, tuning of the resonant frequency takes place by adjusting the compression s.

In vertical damping, the first equation and a low-friction suspension arrangement eliminating the gravity are applied; it is also possible to mount a pre-stressed passive string in parallel with an adjusting spring. The foundation design in accordance with the invention provides a large number of advantages since because of the moving coupling of the foundation it is easier to control vibrations and, in addition, it is possible to manage with lower ground construction costs when problematic soils are encountered. Thus, the invention allows, among other things, quicker and simpler founding of a building to be achieved. Moreover, a part/device of a paper or board machine can be moved to a new mounting location more easily, so that a benefit is achieved in particular when the ground at the new mounting location differs from that of the earlier location.

In the following, the invention will be described in greater detail with reference to the figures in the appended drawing, but the invention is not by any means meant to be narrowly limited to the details of the figures.

Figure 1 schematically shows one application of the foundation arrangement in accordance with the invention in connection with a calender of a system.

Figures 2A - 2C schematically show spring and damping element arrangements used in connection with the foundation arrangement in accordance with the invention.

Figure 3 schematically shows one application for an underneath mounting damper for use in connection with the invention.

Figure 4 schematically shows one application for a moving coupling for use in connection with the invention.

Figure 5 schematically shows one application for a control arrangement for use in connection with the invention.

Figure 6 schematically shows a frequency displacement of a system between the ground and a part/device of a paper or board machine supported by the foundation.

Figure 7 schematically shows a control circuit arrangement associated with dissipation of sudden ground- induced impacts by means of a suppression element.

Figures 8A and 8B schematically show one application for a semi-active mass damper for use in connection with the invention for damping horizontal and vertical vibration.

As shown in Fig. 1, a calender 10 comprises six calendering rolls 11 in the application illustrated in the figure. Calendering nips N are located between the calendering rolls 11. The calendering rolls 11 are attached to a frame 15. A vertical frame beam 16 of the frame 15 of the calender 10 is supported with an inclined beam 12 onto a base 20, which is arranged to be a massive base in accordance with the invention, and which has a moving coupling arranged

underneath it, said moving coupling comprising damping and height-adjustment elements 21 comprising a spring element 22 and a damping element 23. The damping and height-adjustment elements 21 are in turn fixed to a floor 30 of a building.

Fig. 2A is a schematic view of the main features of the foundation arrangement in accordance with the invention, in which damping and height-adjustment elements

21 and spring elements 22 are placed underneath a massive base 20, said spring elements comprising gas cavities 24 allowing the spring constant to be changed by changing the pressure of the gas cavities.

Fig. 2B shows a structure in which damping is accomplished using a magnetorheological fluid 25. Reference numeral 26 designates controllable magnets, which damp according to the formula B α γ, Le. flux density is directly proportional to damping.

As shown in Fig. 2C, compression force F in damping is directly proportional to friction damping, according to the formula F α γ.

Fig. 3 is a schematic view of one underneath mounting damper application. In the underneath mounting damper 21 there are typically four, at least three, cylinders 23 placed at corners of a massive base 20, i.e. a foundation slab. The slab is locked mechanically by means of the cylinders 23 of the underneath mounting damper 21 when machine alignments have been made. Underneath or on top of the cylinder 23 of the underneath mounting damper 21 there is a spring element

22 whose spring constant is adjusted such that operation in the running situation is in an overcritical range. The spring element 22 can be of metal or it can be an elastomer- and gas-containing spring element, so that the spring constant can be changed using the pressure of the gas. In addition, the underneath mounting arrangement 21 can include a variable viscoelastic damper 31, which is controlled

to minimize the running speed and the measured dynamic motion. Another flowing substance can also be used instead of gas.

As shown in Fig. 4, in connection with the invention, sinking is corrected advantageously by means of a hydraulic cylinder 23 such that a part/device of a paper or board machine, such as a calender, achieves its original mounting position. When the position has been achieved, the cylinder is locked mechanically using locking devices 33. Conventional levelling measurements are used for position setting. The position can be monitored, for example, by laser sensor arrangements for minimizing vibration using a change in the friction properties of a viscous damper.

Figure 5 schematically shows one application for a control arrangement for use in connection with the invention.

Fig. 6 is a schematic graph showing displacement of vibrations between the ground and a part/device of a paper or board machine, in which the dominant critical frequency W _cr of a system is adjusted by means of springs to be clearly below the operating frequency Wrunnmg range and small damping is used when the running conditions of the calender are normal. If the system comes to the resonant region or below the critical frequency, greater damping is used according to the formula

nibase + nicalender

As shown in Fig. 7, sudden ground- induced impacts (earthquake) are dissipated by a damping element 21, i.e. damping Δp is increased by means of a control system 41 to produce suitable dissipation. In addition to this, spring constant Δk can be controlled by means of the control system 41, whereby the dominant resonant frequency of the system can be transferred to a more controllable region.

In the applications of the invention shown in Figs. 8A and 8B, a semi-active mass damper 50 provided with a variable stiffness K on a base, the variable stiffness of the mass damper being typically produced by a pneumatic spring element. The operation of the mass damper 50 is based on the fact known per se that a mass 20 placed on support of a spring 51 and a damping arrangement vibrates at its resonant frequency in a phase opposite to the excitation occurring at the same frequency in its base 30. The resonant frequency of the spring 51 -damper 52-mass 20 system is determined, as simplified, as follows:

^L res V K/ m Hz

where K is stiffness (spring constant) (kg/s ² ) m is vibrating mass (kg)

Damping shall be reasonably small in order that the resonance motion of the semi- active damper may arise, but sufficient so that the damper device is not broken. The vibration hampering the base is converted into dissipation heat in the damping element.

In a horizontal mounting arrangement, the above equation can be written:

f ^L _r r _P e«s = V g/ S Hz

where g is the acceleration of gravity (m/s 2\ ) s is the compression caused by mass m in the spring (m)

In that case, tuning of the resonant frequency of the mass damper takes place by adjusting the compression s.

As shown in Figs. 8A and 8B, in one application of the semi-active mass damper used in connection with the invention, an adjustable spring 50 is formed, at its simplest, of an elastomer 51, which has a fluid- filled (fluid = a flowing substance) chamber 52. The pressure of the chamber 52 is used for affecting the stiffness of the spring unit and, at the same time, its compression as well as, based on the equations given above, the desired resonant frequency. This spring structure 50 contains dissipating damping; dissipating damping can be increased by increasing the mass of the fluid, for example, mixing water with air. In the figure the vibrating mass, i.e. the massive base in accordance with the invention, is denoted with reference numeral 20 and it is connected by means of the spring 50 to a floor 30 or to an equivalent building foundation 30.

Above, the invention has been described with reference only to some of its preferred exemplifying embodiments, but the invention is by no means meant to be narrowly limited to the details of them.