FI112879B - Method and apparatus for controlling the vibrations of a coating station's blade beam - Google Patents

Description

112879

The present invention relates to a method for controlling the vibrations of a blade beam used for coating paper or cardboard according to the preamble of claim 1.

These blade beams support a doctor blade or rod for leveling the coating 10 to be applied to the surface of the moving web.

The invention also relates to an arrangement for applying the method.

15 The printing properties of paper or cardboard can be improved by various coating compositions. Typically, the coating composition is applied to the web by a suitable application method and the applied coating layer is smoothed and scraped to a final coating thickness of 20 using a doctor blade or rod. To some extent scraping '' uses, for example, carton air brushes, 'but its limited scraping capacity prevents the use of an air brush' at much current production speeds.

\ '* I 25 Because the coating layer is quite thin and, on the other hand, needs to be very smooth to transfer the printable pattern as well as possible onto the surface of the paper,' '; the distance between the doctor blade and the moving web must remain exactly the right. Thus, the position of the blade 30 is monitored by various measuring devices and the quality of the coating remaining on the web is continuously monitored. These measurements can be used to adjust the position of the blade to the best! for a possible end result. Although the position of the blade can be controlled in many ways today, increasing the running speed of the 112879 2 and especially the width of the machine can cause problems in controlling the vibration of the blade beam. If the cutter bar is able to oscillate especially at one of its characteristic frequencies, the coating will become uneven.

5 Therefore, it should be possible to control the vibration in such a way that the amplifying vibration at the characteristic frequency of the beam cannot occur. In principle, the specific frequency of the cutter bar could be controlled and attenuated by additional masses mounted in the center of the bar. However, the masses should be quite large in order to achieve effective damping. However, this is not possible due to the limited space available. The large mass placed in the center of the beam also increases the deflection of the beam, so the beam should be heavier dimensioned or the straightness compensation of the blade beam 15 must be increased. These disadvantages affect the design of the cutter bar and contribute to limiting the maximum width of the cutter bar.

The currently used blade beams are supported at their ends by 20 pivots on the coating station body and in the center on the coating station lead-through tube. This structure has a number of characteristic frequencies, of which the lowest track specific frequency is very detrimental to the coating because it has the strongest effect on the position of the blade and the "· 25 web. The vibration of the blade bar is caused by periodic excitations occurring during driving. '*: Same as the directional specific frequency of the lowest track of the cutter bar.

As the rotation speed hits the specific frequency of the blade bar, the result is an increase in vibration amplitude and eventually large variations in the amount of coating on the surface of the paper or board. This kind of excitement could be avoided by changing the machine's running speed, but this is often not desired because the machine is driven at the best possible speed or the highest possible speed that guarantees good quality. Thus, it should be possible to control the blade beam vibrations to prevent any resonance vibrations.

It is an object of the present invention to provide a method by which the specific frequency of the cutter bar can be easily changed to shift the characteristic frequency away from the excitation frequency.

10

The invention is based on the fact that the support of the cutter bar is modified to include at least one rigidly variable member.

For example, the blade beam can be fitted with, for example, at least one support for supporting the blade beam to another structure. Preferably, there are two struts and are fitted to the ends of the blade beam in the vicinity of the pivot joints.

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

The arrangement according to the invention, in turn, is characterized by what is stated in the characterization part of claim 5.

The invention provides significant advantages.

The invention can easily be applied to existing ones; by adding even lockable sliding joints to the ends of the beam. There is usually sufficient space for such members in the vicinity of the beam. If rigidity-adjustable struts are fitted into the beam already during the design phase of 112879, there are many different support options. As the stiffness of the beam support is altered, its characteristic frequency also changes, so that by stiffening or loosening the support, the characteristic frequency of the beam is shifted away from the excitation frequency. In its simplest form, a bracket is sufficient, which can be locked stiff and removed as required. When amplified vibration is detected, the strut or struts are locked and the characteristic frequency of the blade bar changes and no resonance occurs or is substantially reduced.

Similarly, when it comes to the resonant frequency of the locked beam, the locking can be released, again moving away from the resonant frequency. It is also conceivable that the locking force should be adjustable, thus allowing greater variations in the characteristic frequency.

15 The adjustable support force can be implemented, for example, by hydraulic or pneumatic devices.

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

20

Figure 1 is a diagrammatic view of one embodiment of the invention.

Figure 2 shows one support member suitable for carrying out the invention.

Fig. 1 is a simple diagrammatic view of the hanging of the scraper bar 1. At the ends of the beam 1 are, ·: bearings 2 through which the beam is pivotally suspended on the body of the coating machine. Scraper blade; 18 is between the pivot points. Since the beam 1 can bend under load and under its own weight, the bearing points 2 are formed as a pivot so that the suspension point and thus also the end of the beam 1 can rotate transversely to the longitudinal axis of the beam. The ends of the beam 1 thus have articulated support according to the rules of statute 112879 5. In the center of the beam 1 is a screw jack 3, by means of which the beam is supported from the center and can be rotated according to changes in the blade angle and blade load. The screw jack is secured to the frame beam 17. The blade beam 1 is thus supported at its ends pivotally and centrally substantially in the longitudinal direction only by the support receiving the vertical loads.

According to the present embodiment, the blade bar 1 is supported by locking brackets 4, 5 at both ends. These supports can be used to change the specific frequency of the blade bar. Each support includes a slide bar 19, a pivotable joint 15 for attaching the end of the bar 19 to the blade beam 1 and a lockable sliding sleeve 16 rotatably attached to the frame beam 17. When the lockable support, i.e. in this example sliding joint 4.6 is unlocked, the blade beam moves freely slides in sleeve 16 when the rod end joint 15 and the sliding sleeve joint rotate freely. The slide bar 19 can be locked into the sleeve 16 in a variety of ways, such as by taper connection, wedge, clamp or eccentric. The movement of these organs ·; Conventional actuators, such as hydraulics, pneumatics or electrical devices, can be used to achieve this. At the same time, when the lockable support is locked, clearance must be removed from its pivotal joints 15, 16.

J This can be done as described below.

Under normal driving conditions with no resonance, the struts are unlocked and do not support the beam in any way.

As the resonance frequency is approached, the supports 4, 5 are locked, whereby the support of the blade bar 1 becomes stiffer and the specific frequency increases. While reaching this new stiffened characteristic frequency 112879 6, the supports 4, 5 are released, whereby the characteristic frequency decreases. In this way, the characteristic frequency of the bar can always be shifted away from the excitation frequency and the resonance state of the blade bar 1 is avoided.

The struts must be designed in such a way that they can be released by turning the blade bar 1 and must not impede the movement of the bar 1. One embodiment of such a support is shown in Figure 2. The member of the figure must lock a sliding joint 6 consisting of an outer tube 7 and a rod 8 fitted therein. Normally, the bar 8 can move within the outer tube 7, but movement is prevented.

This provides a solid support for the ends of the blade bar 1. The ends of the outer tube 7 and the bar 8 have fastening members 9, 10 which are fitted to the blade beam 1 and sleeves 11, 12 fixed to a suitable fixed support point, for example, to the coating station body. The fastening members 9, 10 and bushes 11, 12 have concentric holes the conical pins 13, 14. The conical pins 13, 14 allow the clearance of the sliding joint 6 at the attachment points to be removed and •: ·: provides a solid support. Conical pin movement: the steering is synchronized with the sliding joint 6 locking control, i.e., when the blade beam angle is changed, the lockable sliding joint is opened and at the same time the conical locking pins are pulled out slightly to create clearance at the attachment points and to rotate the sliding joint securing members. The function of the sliding joint and taper pins can be hydraulically performed since hydraulic power is usually readily obtainable by the coating machine.

Of course, the operation can also be performed by electrical or pneumatic actuators.

11/879 7

In addition to the foregoing, the present invention has other embodiments.

Instead of the mechanical sliding joint described above, a double-acting hydraulic cylinder can be used which can be locked by closing the fluid lines leading to the work chambers. Pneumatic actuators can be used, but their flexibility can cause problems. However, these actuators may, if necessary, be provided with a mechanical lock. It is also conceivable that the thrust is adjustable if the number of excitations is large or their frequency range is wide. Usually, however, excitations only occur at specific frequencies, so a simple lock and unlock support is sufficient and inexpensive to implement. The adjustable support member could be friction locked, hydraulic or pneumatic.

Instead of the ends of the beam, the support member of variable stiffness may be located elsewhere in the beam. Admittedly, the above. the support placed in the example is easy to adjust. and the support is symmetrical.

Alternatively, it could be used at the ends of the beam. : Impressive beam axial support to prevent beam head rotation. Correspondingly, the pivot of the beam swivel joint can be prevented by force-adjustable, ·,: friction locking or locking support. Of course, there may be multiple support members, ···, but two support members on either side of the centerline provide symmetrical * support and the beam deflection is not adversely affected.

Claims (8)

112879 A method for controlling vibration of a blade beam of a coating station in a structure in which the blade beam (1) is supported at both ends by a joint (2) and at least one actuator (3) for changing the position of the blade beam (1) (4, 5) such that by changing the stiffness of the support, the specific frequency of the cutter bar (1) can be changed. Method according to Claim 1, characterized in that the blade beam (1) is supported symmetrically on both sides of the center line of the beam by at least two rigidly adjustable members (4,5). Method according to claim 1 or 2, characterized in that a rigidity-adjustable member (4, 5) which can be locked in position and released t for free movement, such as a lockable sliding joint or a hydraulic cylinder, is used. A method according to any one of the preceding claims, characterized in that it is operated with a support force. an adjustable member whose stiffness is controlled, for example, by frictional, hydraulic or pneumatic means. Arrangement for controlling vibrations of the blade beam of the coating station, comprising a joint (2) fitted at each end of the blade beam (1) for supporting the blade beam and for changing the position y of at least one actuator (3), characterized by at least one rigidity , 5) for supporting the blade beam (1) emiseksi Λ Γ · Ο Π Γ 'to support 1 blade (y) of blade beam (1) so that the specific frequency of the blade beam (1) can be changed by changing the stiffness of the support. Arrangement according to Claim 5, characterized in that at least two rigidity-adjustable members (4, 5) are arranged symmetrically on both sides of the beam center line. Arrangement according to Claim 5 or 6, characterized in that the rigidity-adjustable member (4, 5) can be locked in a fixed position and released for free movement, such as a lockable sliding joint or a hydraulic cylinder. Arrangement according to one of Claims 5 to 7, characterized in that the rigidity-adjustable member (4, 5) is a lockable sliding joint (6) fitted to the blade beam (1) via a conical pin connection which can be opened. 112879