Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05C1/00—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating
  • B05C1/04—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length
  • B05C1/08—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line
  • B05C1/0826—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line the work being a web or sheets
  • B05C1/083—Apparatus in which liquid or other fluent material is applied to the surface of the work by contact with a member carrying the liquid or other fluent material, e.g. a porous member loaded with a liquid to be applied as a coating for applying liquid or other fluent material to work of indefinite length using a roller or other rotating member which contacts the work along a generating line the work being a web or sheets being passed between the coating roller and one or more backing rollers
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
  • D21H23/22—Addition to the formed paper
  • D21H23/52—Addition to the formed paper by contacting paper with a device carrying the material
  • D21H23/56—Rolls
  • D21H23/58—Details thereof, e.g. surface characteristics, peripheral speed

Definitions

• the present invention relates to a method according to the preamble of claim 1 for preventing vibrations of the rolls of a film transfer coater.
• the invention also relates to a method for adjusting linear pressures between rolls.
• the invention further relates to an arrangement for implementing the aforesaid methods.
• a roll group comprises at least two rolls forming a nip.
• the paper or board web being manufactured is taken through said nip.
• Roll groups comprising at least one soft roll are employed in, e.g. calenders and film transfer coaters.
• Film transfer coaters are used for surface sizing or coating paper.
• the film transfer coaters currently employed have at least one soft roll and applicator means for applying the treating agent onto one or both rolls.
• the web being treated travels through the nip between the rolls whereby a film of treating agent applied onto one roll or both rolls is transferred onto the web surface.
• the vibrations are only intensified at the natural frequencies of the apparatus, and thus, the vibration problem could be eliminated by varying the driving speed such that the vibration impulses would not coincide with the natural frequencies of the apparatus. It is clear that paper and board manufacturers wish to run their machinery at speeds achieving maximal productivity and product quality. Therefore, having to change the speed of the production machinery due to the vibrations of the film transfer press is unacceptable. In addition, variations in speed will also increase the risk of web breaks. The number of web breaks has a significant effect on productivity wherefore their number must be kept as low as possible. Controlling and varying the speed of the production line is difficult. The speed of the production line is controlled to an optimal level such that maximal productivity is obtained, whereby web breaks are taken into account, and simultaneously the quality of the product remains adequate.
• the vibration tendency can be reduced by using rolls having a thin surface material layer and a thick jacket. In practice this is not a good solution because rolls having thick jackets are heavy.
• the thickness of the roll surface material layer can only be reduced to a certain extent because the rolls must be dressed at regular intervals due to wear and deformations of the coating. What is more, film transfer coaters are designed for a certain type of rolls wherefore the use of a new type of rolls in existing film transfer coaters may prove difficult.
• the risk of vibrations is increased by the fact that the loading cylinders are arranged at the ends of long shafts whereby the movements of the roll are repeated in a manner determined by the geometry of the shafts on the loading cylinder, and correspondingly, the movements of the loading cylinder as roll movements.
• Microspheres are minuscule capsules containing colouring agent, used in the manufacture of self-copying papers.
• the spheres must not be broken during the coating of the base paper wherefore excessive force must be avoided during their application onto the paper surface.
• the linear pressure of the film transfer coater must be kept very small.
• loading cylinders are difficult to control at small forces. Therefore, in order to achieve the small forces needed for microsphere coating, the structure of the loading system of the rolls must be altered.
• a spring or another actuator device operating against the loading force of the cylinder is arranged in connection with the hydraulic cylinders loading the backing roll- or the loading roll.
• the linear pressure is controlled, the cylinder operates against the spring and the forces required for moving the cylinder are greater. Because the cylinder operates against a greater counterforce, friction inside the cylinder does not affect its movements as greatly as in the case of small forces.
• the above-described structure is probably suited for small linear pressures and low speeds.
• the loading of the roll of a film transfer coater is arranged by means of a shaft turning round a joint such that the loaded roll is arranged at one end of the shaft and the loading cylinder is at the other end, the construction is highly susceptible to vibrations. If the speed is increased and the speed used coincides with the vibration frequency of the loading roll, not even a spring-loaded cylinder, which is arranged far from the vibrating rolls and on the opposite side of the joint of the loading shaft to the loaded roll, can suppress the vibrations of the rolls.
• the roll/loading cylinder combination functions as a spring-loaded mass having its own vibration frequency.
• a film transfer coater implemented using this manner of loading is more sensitive to vibrations than conventional film transfer coaters intended for great linear pressures.
• the aim of the present invention is to achieve a method and an arrangement which can be used to prevent the generation of increasing vibrations in a film transfer coater.
• the film transfer coater can also be reliably used at low linear pressures.
• the invention is based on setting a desired linear pressure in the film transfer coater and supporting the moving loading roll with regard to the fixedly fitted roll by means of a separate device acting against the loading direction and by means of a controllable supporting force.
• the force of the loading cylinders is increased to an essentially higher level than is required for achieving the linear pressure applied when the apparatus is driven.
• the invention offers considerable benefits.
• the invention can be used to efficiently prevent the vibrations of a film transfer coater by changing the natural frequency of the coater frame. Supporting stiffens the structure of the coater whereby its natural frequency is altered, and thus, by changing the supporting force the natural frequency of the apparatus can be removed from the area of vibration impulses occurring at a certain speed, whereby resonance vibration which gains strength will not occur.
• a force sensor can be connected to the support means and said sensor can be used to monitor the linear pressure.
• the sensor may comprise a pressure sensor or another sensor suited for force/stress measurements, such as a suitably mounted strain gauge strip.
• the supporting capacity of a hydraulic or some other kind of support means can be determined, e.g. , by means of the pressure of the working liquid.
• linear pressure may vary due to variations in the temperature of the roll surface and many other factors, it is of advantage to monitor the linear pressure whereby changes in said linear pressure can be easily compensated.
• small linear pressures can be controlled by first closing the roll nip at a greater linear driving pressure than desired, whereafter the mechanical locking device can be controlled such that its position determines the desired linear pressure.
• Low linear pressures are often preferred if they are suitable for the product being manufactured. At a low linear pressure, for instance, less deformations of a soft roll surface occur, whereby the risk of vibrations caused by such deformations is smaller.
• a lower linear pressure also increases the service life of the roll coating.
• a suitable actuator for example a hydraulic cylinder
• a hydraulic cylinder can be used to diminish the load of the mechanical actuator, should this be required e.g. to control the reach of a hydraulically driven mechanical device for instance when the power of a hydraulic motor is insufficient to change the reach of a mechanical jack.
• the desired linear pressure can be set by controlling the mechanical actuator. Said control is accurate even at low linear pressures because it operates against a mechanical stop. As the travel paths of the means operating against the mechanical stop are very short, no actuators performing long movements are needed.
• the pressure sensor or a corresponding force sensor can be arranged under the mechanical locking device because it is slowly brought in contact with its stop surface and is not exposed to any blows when the nip of the film transfer coater is being opened or closed.
• the hydraulic cylinder can also be exploited for the purpose of diminishing the force exerted on the mechanical actuator where very large loading cylinder forces are desired.
• the hydraulic cylinder is also operable without a mechanical actuator. Hereby the linear pressure is obtained by deducting the effect of the hydraulic cylinder from the effect of the loading cylinder.
• Fig. 1 is a side view of a film transfer coater according to the invention.
• Fig. 2 is an enlarged detail of the film transfer coater of Fig. 1 and the Figure illustrates an embodiment of the invention.
• Fig. 3 is an enlarged detail of the film transfer coater of Fig. 1 and the Figure shows another embodiment of the invention.
• Fig. 4 is an enlarged detail of the film transfer coater of Fig. 1 and the Figure shows a third embodiment of the invention.
• Fig. 1 illustrates a film transfer coater where the film to be transferred onto the web is applied onto the lower roll 1.
• the film is applied by means of an applicator 3.
• the upper roll that is, the backing roll 2 is arranged directly above the lower roll, that is, the applicator roll 1.
• the apparatus of Fig. 1 is intended for one-sided treatment of the web, wherefore no applicator is provided at the upper roll and the upper roll may be hard, e.g. a chrome plated steel roll.
• the upper roll In arrangements intended for two-sided treatment the upper roll is usually arranged sideways shifted in view of the lower roll and naturally, it has an applicator of its own.
• the positions of the rolls are determined according to the incoming direction of the web being treated.
• the rolls may be arranged at any angle in relation to each other, and thus, there are several possible ways of arranging the rolls. Either one of the rolls may be movable by means of the loading shaft.
• the applicator roll 1 is fixed to the frame 4 via bearing housings 5. As only one end of the apparatus is visible is Fig. 1, the following description only relates to one end of apparatuses. The opposite end is identical.
• the bearing system of the applicator roll 1 is provided with a cooling water inlet 6 through which cooling water and, if needed, heating water, can be taken to the roll.
• the bearing housing 7 of the upper roll is fixed to an auxiliary frame 10 which is fixed to the frame 4 via a joint 8 and a lug protrudes from the bearing housing 7 , the rod of the loading cylinder 9 piston being fixed thereto.
• the backing roll of the film transfer coater can be lifted off the lower roll in order to open the nip by means of the loading cylinder 9 by turning the bearing housing 7 round the joint 8 by means of the auxiliary frame 10.
• a load is provided in the nip, i.e. the linear pressure.
• the linear pressure in the nip is, to be precise, not a linear load; rather, due to deformations of the roll 1, 2 surface, the load is divided onto a narrow, longitudinal area.
• an elevation 11 is provided- on which there is a mechanical jack 12.
• the elevation 11 and the jack 12 are dimensioned such that the jack 12 touches the lower surface of the bearing housing 7 of the backing roll 2 when the nip is closed.
• the jack 12 can in other words be used to arrest the movement of the bearing housing of the backing roll 1 in the vertical direction.
• the supporting force is in this case provided by increasing the effect of the loading cylinders.
• Fig. 2 illustrates one alternative for connecting the jack 12 to the bearing housing 7 of the backing roll 2.
• a lug 13 is fixed to the upper surface of the jack 12 and a corresponding lug 14 is provided in the bearing housing 7 of the backing roll 2.
• the lugs 13, 14 are connected to each other by means of a shaft 15 which simultaneously serves as a dynamometric sensor.
• the jack 12 is a mounting jack whose height adjustment takes place by turning the screw 16.
• the jack or another supporting device is preferably placed between the bearing housings of the film transfer coater, whereby it does not make changing the rolls difficult.
• a hydraulic jack 22 is arranged on an elevation 11 next to the jack 12 and the end bearing 17, said hydraulic jack being used for reducing the force affecting the mechanical jack when controlling the reach of the mechanical jack 12 in situations where controlling the mechanical jack by means of e.g. a hydraulic motor is not possible without a relief of load due to the great frictional forces.
• Another possible way of using the parallel hydraulic jack 22 is influencing the natural frequency, because the hydraulic jack can receive part of the force caused by the loading cylinder 9. The hydraulic jack can be used even alone for controlling the natural frequency of the film transfer coater.
• the supporting device comprises a hydraulic cylinder 23 mounted between the bearing housings 5, 7 of the rolls 1, 2.
• a lug 24, 25 is fixed to each bearing housing 5, 7, the cylinder 23 end being connected to one 25 of the lugs and its piston rod to the other one 24.
• the supporting cylinder 23 is arranged on the opposite side of the rolls 1, 2 in relation to the loading cylinder.
• the invention can be applied in accordance with the supporting arrangement having versatile uses, and in the following, the main alternatives are described which can then be combined in different ways according to the run situation and the tendency of the apparatus to vibrate.
• the main principle is changing the natural frequency of the coater such that it does not coincide with the area of impulse vibrations.
• the natural frequency is advantageously controlled on a continuous basis, whereby the natural frequency is always swiftly removed from the impulse frequency.
• a run on the apparatus is commenced in the conventional manner by adjusting the linear pressure between the rolls 1, 2 to a desired level.
• the run is continued at this pressure until the rolls 1, 2 have reached their operating temperature, that is, their equilibrium temperature.
• the temperature of the rolls 1, 2 After the temperature of the rolls 1, 2 has been stabilized they are mechanically locked such that they cannot be moved closer to one another.
• the locking is performed by means of a jack 12 which during locking is controlled such that it is in contact with the lower surface of the bearing housing 7 of the upper roll l, i.e. the jack is brought is contact with the lower surface of the bearing housing.
• the effect of the loading cylinders 9 is raised to a level greater than is required for providing the linear- pressure of the nip.
• the effect of the cylinders may even be twice the force required for providing the linear load. Even if a loading force which only slightly exceeds the loading force required for the desired linear pressure may sometimes suffice, the loading force may advantageously be double or even greater in order to provide a secure locking.
• the upper roll 2 is locked by the force of the mechanical jack 12 and the loading cylinders 9. Due to the great locking force the upper roll 2 is now supported against the frame 4 as in a fixed installation.
• the locking reduces vibrations in two ways. Firstly, the bearing housing 7 of the upper roll 2 cannot move and vibrations cannot affect the loading cylinders via the bearing housings. In other words, the vibrations are reduced because the parts are locked in their places and cannot vibrate.
• the stiffness of the construction is changed and the distribution of vibrating masses in different parts of the structure changes whereby also the natural frequency of the apparatus changes.
• a changed natural frequency can be exploited in that, if there are vibrations at a certain speed, the locking force is altered whereby the natural frequency is removed from the impulse frequency. Even a small change in the loading force may suffice to achieve a sufficient change in the natural frequency, and thus, the force applied in addition to the force required for the linear pressure may even be very small.
• the above-mentioned control of vibration characteristics is exploited to prevent resonance vibrations.
• the force of the loading cylinder may be varied whereby the natural frequency of the frame continuously changes.
• the control range may be e.g. 0 to 100 kN of additional load in addition to the load required for the linear pressure used. If there is no additional load the jack is out of contact. If the jack at some point during the load varying cycle is out of contact, it must be controlled such that it is in contact before the cycle is continued.
• the load may be varied in many ways and the manner of varying the load is selected such that the risk of resonance vibrations is at its smallest.
• the load may be varied according to an even cycle, statistically, guided by vibration measurement results making use of previous measurement data or the derivative or second derivative of acceleration, or fuzzy control.
• the first or second derivative of acceleration has proved a good indication of vibrations which are about to set in.
• the jack When the basis weight of the product being manufactured is altered, the jack must be calibrated. The jack must be calibrated sufficiently often even where it is taken to use immediately at the start of coating and in order to compensate the thermal expansion caused by changes in the temperature of the coating.
• control method may be used with the arrangement of Fig. 4 or with another arrangement comprising an active actuator such that the loading cylinders and the hydraulic jack which provides the supporting force are used synchronously. It must be seen to by means of programs or sensors that the resultant force of the cylinders gives rise to the desired linear load.
• the linear pressure of the nip is kept constant or at a desired level because by controlling the reach of the jack and by measuring the load carried by the jack one always knows the calculated linear pressure, this being the calculated force generated by the loading cylinder minus the force carried by the jack.
• the mechanical jack may be operated by an electric or a hydraulic or pneumatic actuator.
• the jack cannot always provide sufficient forces for the above- described method of measurement. In such a case it is possible to use e.g. an arrangement according to Fig. 3 where a hydraulic jack is arranged next to the mechanical jack.
• the hydraulic jack may be used to reduce the load of the mechanical jack during controlling and controlling is easy.
• This manner of supporting ⁇ is suited for setting low linear pressures.
• the nip between the rolls is extremely difficult to control in a reliable manner partly due to friction in the construction and the fact that large loading cylinders cannot be used to provide small forces in a controlled manner.
• the nip is closed with a linear pressure which can be controlled, e.g. 20 kN and after the run has begun the linear pressure is reduced using the supporting force or by controlling the reach of the jack to a linear pressure of, e.g. 5 kN or another desired linear pressure.
• a lower linear pressure can be set by adjusting the mechanical jack when the dependence between the rotational speed of the jack and the nip gap is known.
• the desired nip pressure can be set by increasing the force reading of the mechanical jack (by controlling the jack) as the difference between the loading force and the force reading of the jack.
• the hardness of the roll coating is dependent on the temperature, also the dependence of the force on the temperature must be examined at least at the operating temperatures.
• the compression is between 0.1 to 0.5 mm/roll if the coat hardness is 35 P&J, wherefore the total control range is very small, about 1 mm. Thus, the movements required are very small.
• the linear pressure in the nip may change if the temperature of the coating changes. Changes in temperature give rise to drifting of the linear pressure, which is intolerable while the apparatus is in operation.
• the linear pressure can be monitored by arranging a pressure sensor under the mechanical jack 12 or by arranging some other sensor suited for force measurement in connection with the jack. When the pressure sensor indicates that the linear pressure between the rolls changes, extra loading force is removed from the loading cylinders whereby the operational linear pressure prevails between the rolls. Once the linear pressure has been set the mechanical jack 12 is again brought in contact with the bearing housing 7 of the moving roll and the bearing housing is locked in place by increasing the force of the loading cylinders.
• the constancy of the linear pressure between the rolls can also be measured by directly measuring the temperature of the roll coating or by monitoring the difference between the temperature of incoming and outgoing cooling water.
• nip pressure can be set at a desired level in the manner described below.
• the method is suited for all nip pressures used with the apparatus and as the rolls can, if desired, in a controlled manner be made to stay even at a distance from one another, even low nip pressures are easily set.
• a hydraulic jack 22 is arranged next to the mechanical jack 12. This hydraulic jack can be used for reducing the load of the mechanical jack.
• low linear pressures are set for instance such that the greater linear pressure is set first whereafter the bearing housing 7 of the roll 2 subjected to loading is locked in plaee in the above-described manner.
• the bearing housing 7 is loaded by means of the hydraulic jack 22 against the loading force of the loading cylinders, whereby the reduction of the load is indicated by the pressure sensor of the mechanical jack 12.
• the linear pressure of the nip is obtained by calculations based on the compression of the coating.
• the movement of the bearing housing 7 of the upper roll 2 is, if needed, locked again by controlling the mechanical jack 12, whereafter the force of the loading cylinders can be increased in order to lock the bearing housing in place.
• the reach of the mechanical jack can be controlled to correspond to the desired linear load. After this the control of natural vibrations can be begun using the loading cylinder and/or the hydraulic jack.
• the invention can be applied in connection with many kinds of film transfer coaters.
• the basic types of film transfer coaters are the coater of Fig. 1 where the rolls are aligned directly on top of one another and a coater in which the rolls are arranged obliquely in relation to one another viewed from the side.
• What these apparatuses have in common is that one of the rolls is carried by an auxiliary frame or the like and the auxiliary frame is fixed to the frame of the apparatus by means of a joint.
• the auxiliary frame and the roll turn round the joint due to the loading cylinders, whereby a load is provided between the rolls.
• the auxiliary frame may have various shapes and in some cases it is no more than a simple articulated arm, the loading cylinder being mounted to one end thereof and the roll to be loaded to the other.
• the supporting means requires different positioning in different apparatuses. What is essential, then, is that the mechanical jack is arranged such that the movement of the roll being loaded or the moving roll towards the fixedly mounted roll can be attenuated.
• the jack may be supported against the bearing housing, auxiliary frame or shaft of the roll being loaded, the shaft turning round the above-mentioned joint.
• the jack must be fixed to a fixed part of the apparatus such as the frame or to the bearing housing of the stationary roll such that one of its sides is supported against the part which moves when the loading cylinder is being used.
• the hydraulic cylinder can, like the mechanical locking means, be arranged at a number of places in the apparatus.
• the mechanical locking can be implemented in many ways. In addition to a mounting jack, screw jacks, special wedge surfaces, or the like may be used. An automatically used actuator or one operated by remote control is preferably used for controlling such mechanical locking means, but if the need for control measures is small, the means can even be manually operated.
• the actuator can be used for setting even great linear pressures in a manner corresponding to the setting of low linear pressures.
• the actuator may be hydraulic, electric or pneumatic, or it may even be based on thermal expansion, because the distances which need to be covered are very small. Depending on the articulation of the moving roll and the positioning of the actuator, a longer path may sometimes be needed.
• the actuator may also be a spring or an actuator generating a similar constant force.
• the supporting must often be slightly giving in order for the structure of the coater to remain undamaged. Sufficient elasticity is provided by placing an elastic mat under the means providing the supporting force.
• the natural frequency may also be affected by controlling the attenuation of the support and here, a change in the supporting force also means a change in attenuation e.g. by choking the oil flow of the hydraulic cylinder.
• the supporting does not jeopardize the rapid opening of the roll nip if a break occurs.
• a hydraulic jack, hydraulic cylinder and spring or spring tabs is/are used, the opening of the nip in fact becomes more rapid if the supporting is only attached to one surface.

Landscapes

• Application Of Or Painting With Fluid Materials (AREA)
• Coating Apparatus (AREA)
• Paper (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (2)

Family

ID=8548385

Family Applications (1)

Country Status (6)

Cited By (3)

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Citations (5)

Family Cites Families (4)

• 1997
  • 1997-03-13 FI FI971062A patent/FI111134B/fi not_active IP Right Cessation
• 1998
  • 1998-03-10 AT AT0903998A patent/AT414245B/de not_active IP Right Cessation
  • 1998-03-10 AU AU64015/98A patent/AU6401598A/en not_active Abandoned
  • 1998-03-10 DE DE19882190T patent/DE19882190B4/de not_active Expired - Fee Related
  • 1998-03-10 WO PCT/FI1998/000209 patent/WO1998040558A1/en active Application Filing
  • 1998-03-10 BR BR9808316-3A patent/BR9808316A/pt not_active Application Discontinuation

Patent Citations (5)

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