FI115555B - A method of dampening the vibration of a beam and a vibration-damping beam - Google Patents

Description

115555

The present invention relates to a method according to the preamble of claim 1 for damping the vibration of a beam-like body.

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The invention also relates to a vibrating damped bar-shaped body.

The purpose of calendering is to increase the smoothness and gloss of paper or cardboard and to enhance other printing surface properties. When calendering paper and board, the web 10 is formed into a nip formed by two opposing rolls. The calender rolls can be hard or soft. The coating of soft-surface rolls is made of paper, other fibrous material or polymeric material. Hard surface thermo rolls are generally made of cast iron and can be heated or cooled by oil, steam or other means, for example by induction heating.

15 In long nip calendars, the other roll is replaced by a load shoe and a strap that surrounds it.

During the use of the calender, impurities which weaken the calendering effect, such as coating mixture, tape or strips of paper, adhere to the surfaces of the rolls of the rolls, in particular to the surfaces of rolls with a polymer coating '; due to the typical electrical charge of the polymer coating. Pieces of tape and paper adhering to the surface of the roll may cause traces not only of the web being calendered but also of: the coating of the roll. A nip load of 300-450 kN / m causes a radial deflection of the roll shell: typically 60-120 µm, so a 90 µm thick piece of paper on the roll surface: 25 may cause high local loads on the roll surface.

s · »« f * ... * To prevent damage to the web and the roll coating, i::: contaminants adhering to the roll surface are removed with a scraper during calender operation. In the event of a web break: _: 30 the scraper also prevents the web from rotating around the roll. The scraper has a roller shaft. . ·. parallel scraper bar with a blade holder holding the scraper blade.

. *. j Press the scraper blade against the roll using pneumatic loading hoses.

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The scraper beam is usually made by welding, which results in low damping capacity of the scraper beam oscillations. Therefore, the amplitude of the beam oscillation increases to a harmful level with relatively small resonant frequency excitations. The oscillations in the scraper bar 5 are both vertical and horizontal, and the oscillations can occur from both harmonic and impulse excitations. The scraper bar is mounted on the same supports as the roll, which causes the sudden movements of the rolls to pass through the scraper to the scraper bar and act as impulse exciters that cause the bar to oscillate at its critical characteristic frequency. In addition, both the harmonic and impulse excitations are transmitted from the rotating roll against which the 10 scraper blades are pressed, via the blade holder, to the scraper bar. If the excitation frequency of the roll is the same as the characteristic frequency of the scraper bar, the bar begins to oscillate at its characteristic frequency.

At present, the aim is to prevent vibrations caused by harmonic excitations by dimensioning the specific frequency of the scraper bar higher than the frequency of harmonic vibration caused by the rotation of the roll. The magnitude of the beam's specific frequency is influenced by its mass, stiffness, and support. However, raising the critical characteristic frequency of the beam usually increases the weight of the beam assembler, which complicates the beam design and increases the manufacturing cost. However, raising the critical characteristic frequency of the bar: 2 0 does not respond to oscillations caused by impulse-like excitations, t t *, because the impulse-like excitation on the beam generates a wide frequency band.

. The object of the present invention is to provide a novel method for the beam; to dampen vibrations. Another object of the invention is to provide: '25 a new kind of vibration damped beam.

I ·: *: The invention is based on providing at least one in connection with a non-rotatable bar-like body, preferably at the dome of the vibration damping mode; ; an oscillator whose oscillation frequency is set to

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: '' '; 30 lower, preferably substantially lower, than the frequency of the beam or the frequency range to be attenuated. In one preferred embodiment of the invention, the attenuator, ·. : consists of a damping element absorbing the vibration energy of the beam and • »3 115555 mass applied to the damping element. The damping element absorbs the vibration energy of the beam and converts it into another form of energy, such as heat, utilizing inertia.

More specifically, the method according to the invention is characterized in what is set forth in the characterizing part of claim 1.

The beam-shaped body according to the invention, in turn, is characterized by what is stated in the characterizing part of claim 6.

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The invention provides significant advantages.

By the method of the invention, the vibrations of the beam can be effectively suppressed. Because the vibration dampener operates by utilizing inertia, it also dampens 15 oscillations at non-beam frequencies. Further, the damper according to the invention is simple in construction and easy to install in connection with the beam to be damped.

The invention will now be described in more detail with reference to the accompanying drawings.

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Figure 1 is a perspective perspective view of one vibration damped bar flavored body.

Fig. 2 is a front view of the attenuator of Fig. 1.

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The bar 1 shown in Figure 1 is, for example, a scraper bar for a calender roll. Scraper bar,: is parallel to the axis of the roll and beam 1 is attached at its ends to the same brackets as the scraper roll. Scraper beam 1 is generally made by welding and is: ': enclosed. A scraper holder is attached to the scraper bar to hold the scraper blade.

: * “: 30 Press the scraper blade onto the roller and remove the pneumatic load from the roller. , *, with lightening hoses. The scraper blade snaps into the roll when the loading hose is filled

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. ·. : with air and detached from the roll when the loading hose is emptied of air. The scraper is rotated to 4 115555 service position by means of a swivel cylinder. The pivoting cylinder may be hydraulic or pneumatic. The doctor blade is usually made of composite material.

In order to dampen the vibrations of the beam 1, a so-called absorbing energy 5 is arranged in connection with the beam 1. a spring-mass damper 2. The damper 2 is attached to the upper surface of the beam 1, thereby damping the y-axis of the coordinate system shown in Fig. 1, i.e. the height of the beam 1. Corresponding damping in the y-axis is also achieved by the damping located on the underside of the beam 1. If it is desired to dampen the oscillation in the x-axis of the coordinate system, i.e. in the width direction 10 of the beam 1, a damper must be placed on the front and / or rear surface of the beam 1.

The damper 2 is attached to the beam 1 at the dome point of the damped oscillation mode, i.e., at the point where the amplitude of the damped oscillation is greatest. If the beam 1 has a plurality of dome locations, a dampener 2 is provided at each dome site. If necessary, multiple dampers 2 may be located at 15 dome locations. Since the damper 2 is practically non-pointy, it is symmetrically aligned on both sides of the dome site If the beam 1 is supported at both ends, the dome position of the damped vibration is usually between the support points at the center of the beam: 2 0 1, whereby the distance from the dome position to both support points is equal.

*, Similarly, if the beam 1 is supported not only at both ends but also at the center, it is; \ bar 1 usually has two dome locations of the damped vibration form which are the beam; 1 between the center point of support and the points of support at the ends of beam 1.

f I * • »»: * '. * 25 The damper 2 has a vibration energy absorbing damping element 3, which is secured by the fasteners 5 at its first end to the dome position of the beam 1 to be damped by the beam 1. At one end of the damping element 3, a mass 4 is attached. The damping element 3 is both flexible and damping. In the drawings: '; In the embodiment shown, the damping element 3 is made of a thread ': 30 bent wire and comprises two rows of wire coils disposed parallel to each other in the longitudinal direction (z) of the beam 1. The lower surfaces of the wire coils are attached to: the lower brackets 5 and the upper surfaces to the upper brackets 6. The mass 4 is attached to the 5 115555 upper brackets 6. The lower brackets 5 and upper brackets 6 are made of high vibration damping material, e.g.

5 The damping element 3 is flexible in all directions and effectively absorbs impact loads. Since the mass 4 is supported and secured only to the damping element 3, it can move freely on the damping element 3. The mass 4 resists the movement caused by the oscillation of the beam 1, whereby the damping element 3 between the mass 4 and the beam 1 is subjected to forces which cause the movement in the damping element 3 to be transformed into another form of energy, usually thermal energy. If a wire is used as the damping element 3, the strands in it will rub against each other as the wire moves, thereby producing heat due to friction. Because the attenuator 2 operates by utilizing inertia, it is capable of attenuating the oscillation of the beam 1 at different frequencies.

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The mass 4 and the spring constant and damping coefficient of the damping element 3 are chosen such that the specific frequency of the damping device 2 is lower than the frequency of the beam 1 or the frequency band to be damped. Usually, the frequency to be attenuated is the characteristic frequency of the beam 1 or the narrow frequency band on either side of the characteristic frequency. The characteristic frequency of the attenuator 2 is set such that it is less than 99%, preferably less than 90%, of the frequency of the vibration to be attenuated. The mass ratio of the beam 1 to the mass of the damper: 2 in one embodiment of the invention is about 10. The magnitude of the spring constant and the damping coefficient of the damping element 3 * · can be influenced e.g. by changing the number of threads on the wire s, changing the dimensions and stiffness of the threads used in the wire \ * 25, changing the weave pattern of the threads, and changing the dimensions of the wire loops and wire rows. The '·' friction damping elements 3 described above are generally available with different size spring constants and * »'·; · 'With damping factor values.

'... * 30 The invention has embodiments other than those described above.

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As a damping element 3, a fluid dampener, a gas dampener, a rubber or some other movement-resisting element having a high internal damping capacity may be used instead of, or in addition to, the friction dampener described above. Several types of damping elements of this type are also available and are not difficult to design by any person skilled in the art. The attenuator 2 may, if necessary, be positioned inside the beam 1 at the dome position or positions of the vibration form to be attenuated.

The damper 2 can also be used to dampen vibrations of other beam-like and non-rotating machine parts. Such machine parts include e.g. papermaking machine scraper beams, gauge beams, gauges, non-rotating 10 take-out rollers, calender humidifiers, presses, Yankee cylinders, dryers and coating equipment.

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Claims (6)

A method for attenuating the vibrations of a beam-like piece (1) in a calender, adjacent to which piece (1) is provided at least one vibration damper (2), whose intrinsic frequency is adjusted lower than the frequency or frequency band of the vibration to be damped; characterized in that the vibration damper (2) is arranged in the dome of the vibration mode to be damped. 2. A method according to claim 1, characterized in that a vibration damper (2) is used which is fastenable, resilient and damping damping element (3), on which a mass (4) is arranged. 10 Method according to claim 2, characterized in that a cables are used as damping element (3). 4. A vibration damped beam-like piece (1) in a calender, adjacent to which piece (1) is provided at least one vibration damper (2), whose intrinsic frequency is adjusted lower than the frequency or frequency band of the vibration to be: attenuated, characterized by that the vibration damper (2) is arranged in the dome point • of the vibration mode to be damped. A piece (1) according to claim 4, characterized in that the vibration damper, (2) comprises a resilient, resilient and damping damping element, (3), in which a mass (4) is arranged. • I ;, J 20 6. A piece (1) according to claim 4, characterized in that the damping element (3) comprises a cable. * 1 1 1 »• 1 * I · • 1 • 1 · • 1» »1