FI104209B - Hardware for damping vibrations in a paper machine environment - Google Patents

Description

104209

Apparatus for damping vibrations in a paper machine environment

The invention relates to an apparatus as defined in the preamble of claim 1 for damping vibrations in a paper machine environment.

In paper machines and paper finishing machines, oscillations form one of the noteworthy problems of ever increasing speeds. There are several possible sources of vibration in paper machines, such as rollers and cylinders, which comprise a very large mass rotating at considerable speed. The aim is to eliminate the vibrations of the rolls by making the rolls with high dimensional accuracy, and in addition to balancing them.

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However, current paper machines and paper finishing equipment are increasingly using soft-coated rollers, which can provide a significant source of vibration when used. Such rolls are used, for example, in presses, calenders, coating machines, adhesive presses, supercalenders, and the like, wherein said soft-coated roll forms a nip with another roll. A paper web and possibly a felt, wire or the like are passed through the nip. When a wire, felt or web seam passes through the nip during such a nip roll solution, significant impurities or anything else that causes a significant change in the thickness of the web passing through the nip, the coating will need to be resilient to act as an oscillating spring.

For example, in an adhesive press and an adhesive press type coating device, the nip ^ · is formed by two rolls with one nip roll mounted directly on the bearing housing of the device while the opposite roll 30 is mounted from its bearing housing to the load arms. In this case, especially the roller mounted on the load arms starts to vibrate, whereby the coating of the soft surface roller is modified, as a result of which the vibration is increased 2,104,209 and the roller begins to resonate. In such a situation, one oscillation frequency is generally formed at a clearly amplitude of its amplitude, whereby the situation can be addressed by a dynamic attenuator tuned to the problematic excitation frequency. The dynamic attenuator is capable of attenuating a very narrow frequency band and excitations outside the 5 narrow frequency band are not affected by the dynamic attenuator.

With presses in which a press nip can be formed between two hard surface rolls or between a hard surface and a coated roll, the press nip and the press felt 10 passing through the press nip can cause problematic vibrations. The press felt seam and water bound to the press felt can cause a discontinuity in the press felt that causes the vibrator to vibrate. This produces a higher frequency oscillation due to the rolls and a lower frequency oscillation due to the press felt. In such a situation, only 15 dynamic attenuators tuned to one narrow frequency band will attenuate only the problematic excitation frequency within that frequency band and other problem frequencies will not be attenuated.

Applicant Fl patent application 971864 discloses a method and apparatus for damping vibration in a paper machine or paper finishing device. In the method; a dynamic damper is used, which comprises an additional weight suspended by a spring on the vibrating object. In the method, the vibration frequencies of a continuously oscillating object are measured by one or more oscillation sensors. The oscillation-Turin measurement signals are amplified by an amplifier and fed to a vibration analyzer which detects the problematic excitation frequency and converts that problematic. as an excitation frequency control signal. The control signal is supplied to a control device for changing the spring constant of the dynamic damped spring and / or the mass of the dynamic dampener to obtain substantially the same dynamic frequency of the problematic excitation frequency.

U.S. Patent No. 4,420,371 to 30,310,0209 discloses a vibration damper for use in a vibrating headbox. The patent discloses a headbox fitted with three separate vibration dampers. The first vibration damper mounted on the rear of the headbox damps the machine vibrations, the second vibration damper mounted on the headbox 5 dampens the vertical vibrations and the third vibration damper mounted on the side of the headbox damps the horizontal deviations from the machine direction. The first vibration dampener, which dampens machine-directional vibrations, consists of three separate vibration dampers mounted on a common platform, each consisting of a rod attached to both ends at the abovementioned base and a weight attached to the center of the rod, each tuned to a different frequency. One of the vibration dampers for the aforementioned machine oscillation is tuned to the midpoint of the problem oscillation frequencies, the second oscillation dampener is tuned below the midpoint and the third vibration dampener is tuned above the midpoint, thus covering a larger area than just one damp.

• · *

It is an object of the present invention to provide an apparatus for attenuating a plurality of problematic oscillations in a different frequency range by means of a dynamic attenuator.

20, the main features of the apparatus according to the invention are set forth in the characterizing part of claim 1.

The invention measures the vibration frequencies of a vibrating system with one or more vibration sensors. The measurement signals of the vibration transducer are amplified by an amplifier and fed to an oscillation analyzer which detects the problematic excitation frequencies and converts those problematic excitation frequencies into control signals which control the dynamic mode via the control device. 1

The invention can attenuate several oscillations in the various frequency bands.

The apparatus according to the invention is extremely simple in construction and implementation and can be incorporated into existing structures by simple means to dampen vibrations. ,

The invention will now be described, by way of example, with reference to Figures 5 of the accompanying drawings.

Figure 1 is a diagrammatic view of a known dynamic damper apparatus.

Fig. 2 is a schematic diagram of the oscillation occurring in several frequency bands

Figure 3 is a diagrammatic view of another known dynamic damping apparatus.

Figure 4 is a diagrammatic view of a dynamic damping apparatus according to the invention.

Fig. 5 is a schematic view of an oscillation pattern of an attenuator according to the invention.

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In Fig. 1, the dynamic damper is mounted on a vibrating object, i.e., in this case, a bearing housing 2 of the roller 1. The dynamic damper comprises a mass 4 suspended by a spring 3 on the vibrating object 2. The rod 3 is rigidly mounted on the bearing housing 2 by means of fastening means 5. it is mounted in a substantially horizontal plane on the bearing housing 2. The mass is a disk-shaped weight 4 with an internal threaded hole, by means of which the weight 4 is fitted to the outer threads of the rod 3. The weight 4 can be displaced by rotating the rod 3 in the longitudinal direction so that the distance a of the weight 4 from the attachment point * of the rod 4 in the bearing housing 2 is adjustable.

30 5 104209 Such a dynamic damper has one degree of freedom and can be dimensioned by the basic equation: 'k / m = Ω2, 5 where k is the spring constant of the spring, i.e. rod 3, m is the mass of weight 4 and Ω is the angular velocity of the oscillating object .

The effect of dynamic attenuation is based on tuning the attenuated specific frequency 10 to the problematic excitation frequency. In the case of the figure, the spring constant of the rod 3 is inversely proportional to the third power of the length of the rod 3, so that the specific frequency of the damper can be adjusted by adjusting the distance 4 of the weight 4 from the rod attachment point in the bearing housing. When adjusting the distance a, the characteristic frequency of the attenuator is equal to the problematic excitation frequency, the bearing-15 tumbler 2 ceases to vibrate, and accordingly the weight 4 on the rod 3 begins to vibrate. In this case, the dynamic damper generates an equal * force on the opposite phase of the excitation, whereby the vibration of the machine itself stops.

In the solution of Figure 1, the adjustability of the dynamic dampener is implemented such that the bearing housing 2 whose vibration is to be damped is provided with a vibration transducer v · 6. The oscillation transducer 6 transmits a signal amplified by amplifier 7 and further transmits to the vibration analyzer and looks for problematic wake-ups in the spectrum. Once the problematic excitation frequencies have been determined, the computer 8 calculates the distance a so that the characteristic frequency of the dynamic attenuator coincides with the problematic excitation frequency. Thereafter, the data processing device 8 controls the adjusting device 9 associated with the weight of the dynamic attenuator, which transfers the weight 4 by the rod 3. The adjusting device 9 is preferably, for example, a step motor. The apparatus thus comprises a closed control circuit which continuously measures the oscillation of the meter and thereby adjusts the characteristic frequency of the dynamic attenuator.

6 104209

Fig. 2 is a schematic diagram of the vibration of e.g. The figure shows that there are several problem oscillation frequencies f j, f 2, f 3. This may be because the oscillating system has a plurality of devices that oscillate at different frequencies. For example, at the press section, the press rolls form a source of vibration 5 and the passage of discontinuities of the press felt through the press nip forms another source of vibration. Their oscillation frequencies differ from each other and thus several problematic oscillation frequencies are formed in the system. For example, in adhesive presses, the rolls constitute a significant source of vibration, but the specific frequency of the entire vibrating system is not necessarily the same as the rotation of the rolls that cause the vibration to occur multiple times (in most cases, this is not the case).

The control circuit of the known dynamically damped based apparatus shown in Figure 3 corresponds to the control circuit shown in Figure 1. The dynamic damper spring 3b 15 comprises a rod mounted and secured to the bearing housing 2 as shown in Fig. 1 .... The weight of the dynamic attenuator 4b consists of the reservoir and the fluid contained therein, the amount of which is controlled by the pump 21 and the valve 22. By pumping more liquid from the storage container 23 to the container forming the weight 4b, the mass of the weight 4b can be increased and vice versa. The control device 9 thus controls the pump 21 and the valve 22 on the basis of the control signal received by it to change the amount of liquid in the container associated with the weight 4a. This is only a matter of adjusting the mass of the dynamic damper 4b. In the case of Fig. 3, it is conceivable that the distance a of the weight 4b from the attachment point of the rod 3b is also adjustable.

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The dynamic damping apparatus according to the invention shown in Figure 4 differs from the apparatus of Figure 1 in terms of additional weights. The device according to the invention has three additional weights 4j, 42, 43 instead of one. Equipped with three additional weights, the dynamic damper has three degrees of freedom and three features-30 yokes. The equations of motion for a multiple-degree unmodified system are of the form: 4 »7 104209 [M] {*} + [K] {x} = (P (t)} where [M] is the mass matrix, {x} is the acceleration vector, [K] is the stiffness matrix , {x} 'is a transition vector and {P (t)} is an external force vector.

5

In the embodiment of Figure 4, additional weights 41? The masses 42, 43 are kept constant, but the weights of the additional weights 4j, 42, 43 are not necessarily the same. It may be advantageous for the accuracy of the adjustment to select the masses of the additional weights 4 () 42, 43 such that the first additional weight 4 | the mass is highest, the weight of the second 10 additional weights 42 is the second highest, and that of the third extra weight 43 is the lowest.

The dynamic oscillator of Fig. 4 is adjusted in principle in the same manner as the dynamic oscillator of Fig. 1. The oscillations of the oscillating object are measured by at least one oscillation sensor 6, the measurement signals are amplified by an amplifier 7, after which they are supplied to the data processing device 8 for calculation. On the basis of the measurement results, the data processing device 8 determines the three most problematic excitation frequencies to be attenuated. Thereafter, the data processing device 8 calculates the distance a1 (a2, a3 from the clamping force of the rod 3 of each additional weight 4, 42, 43 so that the dynamic attenuator tunes to the above problematic frequencies. When the distances a, a2, a3 are determined The handwriting devices 8 provide - corresponding control commands for the adjusting devices 9j, 92, 93 which adjust the additional weights to the calculated distances aj, a2, a3 When the additional weights 4, 42, 43 are adjusted correctly, each additional weight 4j, 42, 43 locked in place, after which the dynamic attenuator oscillates at the desired three characteristic frequencies and attenuates the oscillating object 25 corresponding to the three problematic frequencies.

Figure 5 shows three characteristic vibrations of the dynamic attenuator of Figure 4. Each figure shows the envelope of the second extreme edge of the characteristic vibration form. Fig. 5B shows a situation depicting the lowest native frequency of the dynamic attenuator. All three additional weights 4t, 42, 43 vibrate in the same phase, with the first additional weight 4 {having the smallest vibration amplitude and the 8 104209 third additional weight 43 having the highest vibration amplitude. Fig. 5C shows a situation illustrating the mean characteristic frequency of a dynamic attenuation. The third additional weight 43 oscillates at this stage as the first additional weight 4j and the second additional weight 42. Fig. 5D, in turn, illustrates a situation of dynamic attenuation of maximum characteristic-5 where the second additional weight 42 oscillates at a different stage than the first 4j and third additional weight 43.

With the simple three dynamic dampers 4j, 42, 43 shown in Fig. 4, three problem oscillation frequencies can be suppressed. By increasing the amount of additional weights, the characteristic frequencies of the dynamic attenuation are also increased.

The invention may also employ the dynamic damper shown in Figure 3, whereby a plurality of additional weights 4b consisting of a liquid container are mounted on the rod 3b. Hereby the mass of each additional weight 4b can be adjusted instead of the distances, or both the mass of the additional weights 4b and the distance of the additional weights from the attachment point of the rod 3b.

The invention has been described above by way of example with reference to the accompanying drawings. However, the invention is not limited to the examples shown in Figures 20, but different embodiments of the invention may vary within the scope of the inventive idea defined in the appended claims.

Claims (2)

An apparatus for damping vibrations in a paper machine environment by means of a dynamic damping apparatus comprising at least one vibration sensor (6) for measuring the vibrations of a vibrating object, an amplifying device (7) for amplifying a measuring signal, a data processing device (8) for analyzing 9) controlled by a data processing device (8) and adjusting the adjusting device (9) to adjust a dynamic damper attached to a vibrating object to a desired problematic excitation frequency, characterized in that the dynamic damper 10 comprises at least two additional weights (4) mounted on a common bar (3). ,, 42, 43), wherein the dynamic attenuator can be tuned to a plurality of problematic excitation frequencies by means of said additional weights. Apparatus according to claim 1, characterized in that the dynamic attenuator 15 comprises three additional weights (4, 42, 43) mounted on a common bar (3), whereby the dynamic attenuator can be tuned to the three problematic excitation frequencies by means of said additional weights. «10 104209 1. An obfuscation of the vibration vibration of the pappersmaskmillion of the environment, the vibration of the vibration givare (6), 5 of the vibration of the detergent object (7), of the förstärkningsanordning (7), of the förstärkningsanordning (7). 8), I am analyzing mätsig-nalen, och ätminstone en regleranordning (9), wilk styrs med databe-handlingsanordningen (8), och med vilken regleranordning (9) en vid det vibrerande object fäst dynamisk dämpare avstäms account en suskad problematisk kännetecknad därav, att den dynamic dämparen omfattar ätminstone tvä en gemensam Stäng (3) monterade tillaggsvikter (4j, 42, 43), var den den dynamic dämparen kan avstämmas med hjälp av this tillaggsvikter account flera problem-matiska. is 2. Anläggning enligt patent kravet 1, a rotary link dnav, att den dynamo dämparen omfattar tre pä en gemensam Stäng (3) monterade tillaggsvikter (4j, 42, 43), var den den dynamic dämparen kan avstämmas med hjälp av nämnda tillaggsvik. 20 1 «