WO2009101251A2

WO2009101251A2 - Method and arrangement for measuring the nip pressure and/or pressure profile in the nip of a printing unit of a printing press

Info

Publication number: WO2009101251A2
Application number: PCT/FI2009/050103
Authority: WO
Inventors: Tatu PITKÄNEN; Petteri Lannes; Mika Sundquist; Teuvo LEPPÄNEN; Raimo Rajala; Matti Innala; Teemu KÄLKÄJÄ; Klaus JERNSTRÖM; Mika J. Kosonen; Petri V. Hirvonen; Erik Ohls; Liisa Ranta
Original assignee: Upm-Kymmene Oyj; Metso Paper, Inc.
Priority date: 2008-02-12
Filing date: 2009-02-10
Publication date: 2009-08-20
Also published as: WO2009101251A3; EP2250111A2

Abstract

The invention relates to a method and an arrangement for measuring the nip pressure and/or pressure profile in the nip of a printing unit of a printing press. A force and/or pressure sensor, such as a pressure sensitive film, for example, an EMFi film sensor, is installed on the counter roller, rubber roller or roller forming the nip of a printing unit which participates in the printing unit in transferring printing ink onto the paper, plastic or other thin sheet-like material surface, wherein the pressure sensitive film is adapted to produce, in connection with a deformation of the force and/or pressure sensor, an electrical signal corresponding to the magnitude of the deformation. The rollers forming the nip are caused to rotate in relation to one another such that the nip pressure of the nip causes a deformation of the force and/or pressure sensor producing an electrical signal corresponding to the deformation of the nip. The nip pressure and/or pressure profile of the nip is calculated by using the electrical signal produced by the deformation of the force and/or pressure sensor.

Description

Method and arrangement for measuring the nip pressure and/or pressure profile in the nip of a printing unit of a printing press

Background of the invention

The invention relates to a method for measuring the nip pressure and/or pressure profile in the nip of a printing unit of a printing press according to the introduction of claim 1.

The invention also relates to an arrangement for measuring the nip pressure and/or pressure profile in the nip of a printing unit of a printing press according to the introduction of claim 8. The invention also relates to a method for adjusting a rotary printing press according to the introduction of claim 15.

The invention applies to improving the runnability of a printing press. In particular, the invention applies to offset- and gravure printing techniques. Offset printing technique is currently the most commonly used printing method. In offset printing technique, the non-printing surface and the printing surface are on the same level, wherein it can also be referred to as a planographic printing method. The printing element (printing plate) is a level surface on which can be discerned neither clearly raised areas (letterpress printing method) nor recesses (gravure printing method). The planographic printing method is based on the mutual relationship between oil and water, i.e. on that they repel one another.

The offset printing method is based on the fact that oil (ink) and water repel one another. The surface of the printing plate is exposed in a plate printer such that the areas to be printed become areas that attract oily printing ink but repel water. The non-printing areas, on the other hand, attract water but repel the oily ink. Because the printing ink is oily, it attaches only to areas accepting ink.

In the offset printing method, the image to be printed is not transferred directly from the printing plate to the paper rather first as a reversed image to the surface of the rubber cylinder, then from there the right way up to the paper. This has also given rise to the term "offset" because, in this -printing technique, the blank to be printed (the printing plate) is never in direct contact with the printing substrate (the paper) rather the blank is transferred from the printing plate to the rubber blanket of the printing unit and then from there to the paper. The material of the paper is too hard and it would quickly wear down and damage the surface of the printing plate.

When printing occurs in the offset printing method, the dampening rollers dampen the surface of the printing plate and, at the same time, the inking rollers spread ink on the printing plate, wherein the dampening water attaches to the nonprinting areas and the printing ink attaches to the printing areas. After this, the printing ink transfers from the printing plate to the rubber cylinder and the paper travels between the rubber cylinder and the counter cylinder, wherein the ink transfers to the printing paper.

Offset printing can be done in rotary printing or in sheet-fed printing. In rotary printing presses, an unbroken paper web travelling from a paper roll between the printing rollers is used as the printing paper which paper web is cut into page sheets only at the end of the presswork. Rotary printing is a faster printing method than sheet-fed printing and, for this reason, it is used when the amounts to be printed are relatively large.

Gravure printing is a typographical printing method in which gravure printing presses are used. In the gravure printing method, the printing portion of the printing surface is lower than the non-printing surface. The printing ink transfers to the material to be printed from the recesses in the printing surface from which the method got its name. Gravure printing does not use as a printing surface printing plates secured around a cylinder, as in the offset printing, rather, on each printing occasion, the content to be printed is engraved into the copper surfaces of cylinders with an engraving diamond. In addition to a high printing speed and sharp printing quality, the advantage of gravure printing is that relatively cheap mechanical supercalenderized paper can be used.

Gravure printing presses are also generally web printing presses (i.e. rotary printing presses), i.e. presses whose printing material comes from a roll. In the printing process, the gravure printing cylinder is first inked with a liquid printing ink, wherein the recessed cells on the surface of the cylinder are filled. Immediately after inking, a thin steel scraper, i.e. the doctor blade, removes the excess ink from the neck areas between the recessed cells. The material to be printed travels between the impression cylinder and the gravure cylinder, wherein the printing ink is transferred from the recessed cells to the material to be printed with a great compression force. After printing, the printing material travels through a drying device which evaporates the solvent of the printing ink and dries the printing ink.

The invention applies to diagnosing the nip of the printing unit of a printing press. In one printing press, there are usually several printing units for different colours of printing ink. In a four-colour press, for example, there are 4 units, one for black, one for cyan, one for magenta and one for yellow ink.

The nip can be, for example, between two or more rollers, between a tightened belt and a roller, or between a stiff plate and a roller. The nip is formed when the web or sheet-like piece goods are compressed by the roller, belt, shoe or some similar element. In the nip, there can then be the belt compressing the roller or two rollers opposite each other, and between the product that is being prepared or compressed itself and the compressing roller or other element can travel a blanket or wire or a plate or belt forming a printing pattern. The nip is then not just the area of compression between two rollers. ^'

In one printing unit, there are several rotating rollers/cylinders for different purposes and nips which are formed between two rotating rollers/cylinders such that the printing ink can transfer from the ink trough or suchlike via the nip formed by several pairs of rollers to the rubber cylinder and, finally, from the rubber cylinder to the paper, plastic or other thin sheet-like material onto which the printing ink is printed in the printing unit of the printing press. One of the nips of the printing unit is a so-called printing nip formed by the rubber cylinder and another cylinder or by two cylinders through which nip travels paper, plastic or other thin sheet-like or web-like material.

The printing nip causes the transfer of ink to the surface to be printed. If there is too much printing ink or if the web, for some reason, sticks to the roller and detaches later, then the force of detachment increases. In that case, the web attached to the surface of the roller may break or the print quality may decrease. The web's sticking to the roller may, for example, result from changes in adhesion between the printing ink and the roller or between the printing ink and the paper. Currently, no automatic method exists for defining the angle of detachment. Printers/operators monitor the situation visually and adjust the tension of the web based on experience.

Currently, it is not possible to measure the cross-directional profile of a printing nip in a printing press. It is not known whether the linear load in the nip is distributed evenly. For this reason, it is also impossible to adjust the linear load profile after measurement.

In the printing unit, the counter cylinder is coated with rubber. The function of the rubber is to assure the transfer of the printing ink to the substrate to be printed. Wearing on the rubber coating or an incorrect nip pressure will weaken the print quality. Currently, wearing cannot be monitored otherwise than by manual observation by the operators.

The printing ink and dampening water added in the printing unit have influence on the control of the web after the printing unit. If an excessive amount of ink is used, this will cause the rollers to become dirty. Excessive ink use also increases printing costs. Additionally, in the printing unit of the printing press, moisture from the printing ink and dampening water is also transferred into the paper. This decreases the web tension which can cause problems with runnability or colour superimposition. Currently, dosing of ink amounts is based on the personal experience of the printer/operator. Colour shades are measured with a densiometer but by using it it is not possible to control problems caused by the hydroexpansion of the web. Additionally, a disadvantage of gravure printing presses is that the profile of the doctor blade is not known, wherein application of inks can be uneven.

Brief description of the invention

The object of the invention is to solve the above mentioned problems. The object of the invention is achieved by a method according to independent claim 1.

The invention also relates to an arrangement according to independent claim 8. The invention also relates to a method according to independent claim 15. The preferred embodiments of the invention are presented in the dependant claims. The basis for the invention is that by installing a force and/or pressure sensor, such as an electromagnetic film sensor, on the counter roller, rubber roller or roller of the printing unit which participates in transferring printing ink to the paper, plastic, or other thin sheet-like surface, the event in the nip can be measured and the nip pressure and/or pressure profile of the nip can be calculated or produced or estimated. Using this information, the position of the rollers can be adjusted or the rollers can be manually profiled by the users or using automation, wherein, for example, the ink use can be decreased, hydroexpansion of the web can be better controlled and the colour superimposition can be improved.

The basis for the invention is also that, in the printing press, a so-called iRoll roller is used with which the measurement is based on the use of a pressure sensitive film. After the printing unit, an iRoll tension measuring roller can be installed, and the information from this can be used as the basis for dosing the amount of ink or water such that the tension profile remains stable, wherein the runnability also remains good. On this basis, the optimization of ink consumption is also possible. A more exact measurement is obtained if the tension profile measurement roller is located both before and after the printing unit. In that case, the difference profile of tension depending on the amount of ink can be calculated.

The iRoll nip profile measurement can also be used to monitor and adjust the amount of inks and dampening water and evenness of application. The nip profile measurement is installed in an offset press, for example, to the ink transfer roller and the measurement of the doctor blade force profile is installed in a gravure printing press, for example, to the printing roller.

By installing a pressure sensitive sensor film on the surface or below the coating of a roller in the printing nip, it is also possible to measure the site of the detachment line and the form of the detachment line. In relation to the roller, the sensor film can be installed in the 'axial direction (cross-directionally) or alternatively peripherally (in the direction of the periphery of the blanket). The measurement result can be transmitted to an automation system from which comes infoπnation to the control system of web tension. For example, under the influence of delay of the detachment point of the web, the automation system increases the web tension, wherein the detachment occurs earlier influencing the site and foπn of the detachment line. At the same time, the detachment angle of the web can also be adjusted by means of the web tension or another adjustment parameter. If the web follows the counter roller after the printing nip, then it will decrease the print quality and may, at the worst, cause the breakage of the web and the loss of production. The angle of detachment can be influenced, among other factors, by the position of the next web guidance element after the printing nip, the profile of the printing nip, characteristics of the rubber coating, process temperature and characteristics influencing the printing ink adhesion. With a cross-directionally, spirally installed iRoll sensor, the profile of the nip can be measured which is used in profiling. By profiling the profile of the nip directly or as a desired profile in relation to the amount of printing ink in the cross direction, the detachment line can be corrected. Using the iRoll tension profile measurement, the tension profile can be measured which is profiled by means of actuators suited to this purpose, wherein the detachment line can also be optimized to make it straight when variations in the tension profile are eliminated. When the tension profile is straight or of the desired type in relation to the amount of printing ink in the cross direction of the press, the detachment line can be optimized. For example, at a site, where there is a great deal of "viscous" printing ink and the web continues further than a second roller, the tension is increased slightly, wherein the detachment occurs directly. The adjustment parameter can, of course, also be another parameter influencing the detachment line, such as the direction of the departure angle of the web from the printing nip, or, for example, some characteristic influencing the detachment angle of the printing ink. To the roller can also be installed point-like sensors, wherein is measured "sticking^" in the machine direction caused by the nip contact and the viscosity of the printing ink. A sensor has previously been installed on the surface of the roller and the cylinder but it can also be installed in the covering or coating of a detachable roller or cylinder which can easily be exchanged for a new one. Sensor placement in the coating can be done as a part of the coating production process but installation to some area of the coating is also possible after the production of the coating. In this manner, sensors can be quickly and inexpensively replaced, if needed, for example, if a sensor breaks or if, for some other reason, a sensor must be changed. It is advantageous for sensor placement if the sensor locates on the bottom side of the covering, i.e. on the side that is against the roller or cylinder. In that case, the sensor least disturbs the nip event. It is also advantageous if the sensor and the coating have in the installation level of the sensor physical characteristics that are as similar as possible. In that case, no site of discontinuity is created between the materials. The same kind of sensor placement could be used, among other examples, for measuring the printing nips during printing or in corresponding processes where the coating of the roller must be changed at regular intervals.

A pressure sensitive measurement film installed under the printing rubber or printing plate, for example, EMFI or PVDF, can also function as the measurement sensor of the nip profile of a printing nip. In the film, there is arranged a narrow ribbon-like active area which measures the load profile of the printing nip when the ribbon-like portion winds over the nip. The rest of the film is of the same material but is electrically passive. The advantage in this is that the ribbon-like portion of the film does not disturb the nip load being measured because the portions of the film are essentially equally thick. This implementation has two alternatives. In the first embodiment, the active area is arranged such that the conducting area collecting the charge is only in the ribbon-like portion. The thickness of the conductive layers is the amount by which the thickness of the ribbon-like portion exceeds that of the passive portion of the film, i.e. the thickness is about 10-20 μm which, in practice, does not disturb the nip profile. The width of the ribbon-like portion is preferably 10-20 mm and its thickness is 10-20 μm greater than the thickness of the passive portion of the film. The pressure sensitive film has metallic coating for grounding as the EMFi film usually does. In other words, a film the size of a printing rubber or printing plate has both a passive portion of the film and an active portion of the film which active portion of the film is ribbon-like and its thickness is slightly greater due to the conductive layers, approximately 10-20 μm, compared to the passive portion of the film which passive portion of the film is located on both sides of the active film. In the second embodiment, the active and passive portions contain the same kind of conductive layer but the ribbon-like active portion is isolated from the passive portion, wherein only a narrow isolating portion is of differing thickness in the narrow, approximately 100 μm wide neck area. In other words, a film the size of a printing rubber or printing plate has both in the active portion and in the passive portion the same kind of conductive layer having the same thickness but between the ribbon-like active area and the passive portion is made, for example, by cutting the conductive layer a thin crack which isolates the measuring active portion from the passive portion. The cracks are then located on both sides of the active portion and in width they are preferably, for example, 100 μm wide.

Addition of ink to the paper web causes changes in the tension of the web. Web tension is measured in an iRoll measurement in the machine direction, i.e. lengthwise in relation to the web. If the measuring sensor is installed cross- directionally, then a measurement result is obtained for the entire length of the web. In that case, a cross-directional profile is obtained for the lengthwise tension of the web. In practise, the tension of the web is never entirely even throughout the entire length of the web. By using an iRoll roller after the printing unit to define the cross- directional tension profile of the web, the amount of ink and/or dampening water can be adjusted locally (profiled) cross-directionally. In that case, for example, the amount of dampening water can either be increased or decreased at the edges of the web. By using an even and adequate amount of printing ink, better web control is achieved and printing ink costs are reduced. Additionally, the roller nip profiles and nip forces of the ink feed and dampening equipment in an offset press can be measured and these can be adjusted to optimize the evenness of ink feed.

In gravure printing presses, the load force and force profile of the doctor blade can be measured with iRoll sensors installed under the roller coating. Using a combination of above mentioned techniques, the influence of inks and/or dampening water on the web tension profile can be measured first. In that case, the iRoll tension profile measurement is made before and after the printing unit and their difference profile is determined. When a need for adjustment procedures is noticed, the iRoll force profile of the doctor blade is checked, and the blade force is adjusted to the type desired (the magnitude of the blade force, the difference between the halves, and possibly even adjustment of profiling). After this, the tension profile is monitored and further actions are taken, if needed. Above mentioned measurement and adjustment actions can be executed either manually or automatically.

The invention preferably, but not necessarily, utilizes measurement methods of the type in publications WO 2006/075055 and WO 2006/075056 (METSO PAPER, INC.) and/or iROLL technology (METSO PAPER, INC.) for measuring the nip pressure and/or pressure profile. The invention preferably, but not necessarily, utilizes as a force and/or pressure sensor an electromagnetic film sensor, such as a piezo film, such as a EMFi film sensor, which is a permanently electrically charged cell plastic film which functions in the same manner as a piezoelectric sensor. The EMFi film is a foamed, plastic film with a metallic coating and an electrical charge which converts any mechanical movement caused to the film into electrical energy. The voltage signal produced by an EMFi film depends on the sum pressure change exerted on the element such that, when a pressure change occurs, each portion of the element produces an equally large change in the initial voltage. Consequently, the short-term voltage measured with a large-impedance amplifier is the integral of the sum pressure of the sensor. The sensor functions as a dynamic sensor, it does not give a steady result for a sustained applied pressure rather the direct-current voltage component influencing across the sensor changes as a result of leakage currents. Because of this, the sensor functions only when it experiences changes in pressure. A solution according to the invention can also be implemented by means of another sensor, for example, by means of a resistive pressure sensitive film, a piezoelectric PVDF film (polyvinylidene fluoride film) or a PLL film (piezo-pyroluminescent film).

In one solution according to the invention, the force and/or pressure sensor is installed under the rubber coating of the counter cylinder of the printing unit. Rubber coatings develop wear during printing, wherein the load of the printing nip weakens.

Using the measurement coming from the force and/or pressure sensor, the load of the printing nip can be adjusted manually or automatically to an already familiar and well- tried load level. In that case, a uniform print quality is assured even with a worn coating, diagnostic information regarding wear is obtained, and, if needed, the rubber coating can be replaced for a new one. When the rubber coating wears unevenly, the measurement shows on the profile display the change as a local change in profile shapes.

By installing a force and/or pressure sensor under the rubber coating of the counter cylinder of the printing unit, wearing of the rubber coating can be diagnosed by means of a weakened measurement signal. By utilizing this kind of technique, nip events and wearing of the rubber coating can both be brought into the sphere of automatic diagnostics.

In the method and arrangement according to the invention, a force and/or pressure sensor can be used for monitoring/diagnostics of wearing of the rubber coating and, if needed, for compensating adjustments. A measuring pressure sensitive film is installed preferably in a shallow groove made on the surface of the cylinder under the rubber coating. The advantage of the method is the possibility of obtaining a measurement result and diagnostic information for the automation system of a printing press. The primary purpose of the automation system is to adjust the nip load (to compensate for wearing of the rubber coating) and the secondary purpose is to produce diagnostic information/alarm regarding wearing of rubber coatings for maintenance activities.

Rollers in the nip can be profiled, for example,

• by using T roller / FlyMaster -type simple, internally thrust bearing mounted two-shell rollers

• by using zonal profilable/bend-compensated SYM rollers • by profiling, for example, the metal roller in the nip contact inductively by heating, or otherwise by warming the roller/roller coating

• by changing the position of the rollers in relation to one another or by loading one end of a roller more than its other end (correction of nip distortion) • the sum level of force (mid-level) can be adjusted as currently, for example, by means of pneumatic/hydraulic or mechanical actuators

Currently, printing press operators adjust the printing nip as well as the amount of inks and dampening water based on experience. By using the method according to the invention, the printing event is made more uniform on a level based on experience and dependant upon the operator. The web control improves as the feeding of extra ink is decreased and, at the same time, there is attained an ability to see what occurs during printing. This improves opportunities to adjust devices in the proper direction. The sensor placement in the printing nip is easy to detect and monitor.

Likewise, it is easy to monitor the use of a system producing alarms according to the invention in an automation and maintenance system.

Brief description of the figures

In the following, some preferred embodiments of the invention are presented in more detail with reference to the accompanying figures of which

Fig. 1 shows the use of a tension measurement and blade profile according to the invention in a gravure printing press for ink adjustment,

Fig. 2 shows the use of a nip profile measurement according to the invention for adjustment of inks and/or dampening water in an offset press, Fig. 3 shows schematically the length of the nip in a printing nip, and Fig. 4 shows the detachment of the web from the roller of the printing cylinder in an offset press and the influence of ink on the detachment.

Fig. 1 depicts one unit of a gravure printing press in which is, by way of example, marked possible rollers from which a tension profile can be measured. Additionally, in the figure, there is shown the site for measurement of the blade profile of the doctor blade on the printing roller.

Marked with the letter A in Fig. 2, there are depicted sites which can be utilized when making iRoll nip profile measurements for adjustment of inks and/or dampening water in an offset press. In the figure, there is specifically a heatset printing unit in which printing occurs on both sides of the paper simultaneously. The parts of the printing unit are numbered as follows: 1 ink trough, 2 ink duct, 3 contact drum, 4 ink transfer roller, 5 distributor roller, 6 ink plate roller, 7 dampening water reservoir, 8 water duct, 9 water transfer roller, 10 water plate roller, 11 plate cylinder, 12 rubber cylinder and 13 paper web. Fig. 3 shows the length of the nip in a printing nip. When the linear pressure falls, also the length of the nip shortens, and, at the same time, the web travels in the nip a greater distance along the curving periphery, wherein the tension increases. This also occurs cross-directionally, if the nip is profiled. When the speed of the web increases and the tension increases, the web detaches from the roller faster. In the figure, there are an upper roller (14), lower roller (15) and paper web (13).

Fig. 4 depicts the travel of the paper web (13) between the upper rubber roller (17) and the lower rubber roller (18), wherein, as the paper web detaches from the roller, the printing ink (19) also detaches and attaches to the paper web. In Fig. 4, the web detaches from the lower rubber cylinder earlier and follows the upper cylinder for a short distance. Fig. 4 depicts the detachment of the web from the surface of the printing cylinder in an offset press. In the cross-directional sites of the press, in which the detachment occurs later, the web tension is increased or the linear load is reduced. When the tension increases, the web tension pulls the web free from the upper roller earlier. When the linear load decreases, the length of the nip decreases and the detachment also occurs earlier. Both the tension and nip profiling require actuators suitable for those purposes.

Detailed description of the invention

The invention relates to a method for measuring the nip pressure and/or pressure profile in the nip of a printing unit of a printing press. In the method, one or more force and/or pressure sensors, such as an electromagnetic film sensor, for example, an EMFi film sensor, are installed on the counter roller, rubber roller or roller forming the nip of a printing unit which participates in the printing unit in transferring printing ink onto the paper, plastic or other thin sheet-like material surface, wherein the pressure sensitive film is adapted to produce, in connection with a deformation of the force and/or pressure sensor, an electrical signal corresponding to the magnitude of the deformation.

In the method, the rollers forming the nip are caused to rotate in relation to one another, for example, by using the printing press such that the nip pressure in the nip causes a deformation of the force and/or pressure sensor producing an electrical signal corresponding to the magnitude of the deformation. In the method, the nip pressure and/or pressure profile of the nip is calculated or produced or estimated by using an electrical signal produced by the deformation of the force and/or pressure sensor.

In the method, the force and/or pressure sensor is preferably, but not necessarily, installed on the counter roller of the printing nip of the printing unit. In the method, the force and/or pressure sensor is preferably, but not necessarily, installed under the rubber coating of the counter roller of the printing nip of the printing unit.

In the method, the force and/or pressure sensor is preferably, but not necessarily, installed on the roller in a spirally slanting manner. In the method, the force and/or pressure sensor is preferably, but not necessarily, installed in a groove on the roller.

In the method, the electrical signal produced by a deformation of the force and/or pressure sensor arranged on the roller is preferably, but not necessarily, transmitted from the roller with the force and/or pressure sensor wirelessly to a data processing device for the purpose of calculating or producing or estimating the nip pressure and/or pressure profile.

In the method, the electrical signal produced by the deformation of the force and/or pressure sensor arranged on the roller is preferably, but not necessarily, transmitted from the roller with the force and/or pressure sensor at least partially wirelessly to the automation system of the printing press for the purpose of calculating or producing or estimating the nip pressure and/or pressure profile, wherein the automation system of the printing press adjusts the nip, if needed, on the basis of the calculated nip pressure and/or pressure profile. Alternatively or additionally, the automation system of the printing press produces diagnostic information about the nip on the basis of the calculated nip pressure and/or pressure profile. Alternatively or additionally, the automation system of the printing press produces an alarm on the basis of the calculated nip pressure and/or pressure profile. The invention also relates to an arrangement for measuring the nip pressure and/or pressure profile in the nip of a printing unit of a printing press.

In the arrangement, a force and/or pressure sensor, such as an electromagnetic film sensor, for example, an EMFi film sensor, is installed on the counter roller, rubber roller or roller forming the nip of a printing unit which participates in the printing unit in transferring printing ink onto the paper, plastic or other thin sheet-like material surface, wherein the pressure sensitive film is adapted to produce, in connection with a deformation of the force and/or pressure sensor, an electrical signal corresponding to the magnitude of the deformation. The force and/or pressure sensor is preferably, but not necessarily, installed on the counter roller of the printing nip of the printing unit.

The force and/or pressure sensor is preferably, but not necessarily, installed under the rubber coating of the counter roller of the printing nip.

The force and/or pressure sensor is preferably, but not necessarily, installed on the roller in a spirally slanting manner.

The force and/or pressure sensor is preferably, but not necessarily, installed in a groove on the roller.

The arrangement preferably, but not necessarily, comprises a transmission arrangement for transmitting wirelessly the electrical signal produced by the force and/or pressure sensor from the roller with the force and/or pressure sensor for the purpose of calculating or producing or estimating the nip pressure and/or pressure profile.

The arrangement preferably, but not necessarily, comprises a transmission arrangement for transmitting at least partially wirelessly the electrical signal produced by the force and/or pressure sensor from the roller with the force and/or pressure sensor to the automation system of the printing press for the purpose of calculating or producing or estimating the nip pressure and/or pressure profile, wherein the automation system of the printing press is adapted to adjust the nip, if needed, on the basis of the calculated nip pressure and/or pressure profile. Alternatively or additionally, the automation system of the printing press is adapted to produce diagnostic information about the nip on the basis of the calculated nip pressure and/or pressure profile. Alternatively or additionally, the automation system of the printing press is adapted to produce an alarm on the basis of the calculated nip pressure and/or pressure profile. The invention also relates to a method for adjusting a rotary printing press, characterized in that the crosswise profile of tension in the machine direction of the printing substrate used in the rotary printing press is measured from some process site roller of the printing press and/or the nip pressure and/or pressure profile is measured from at least one roller forming the nip which participates in the printing unit in transferring printing ink onto the printing surface of the substrate, such as paper, plastic or other thin web-like material surface, and the printing process is adjusted on the basis of the information obtained.

In one embodiment, the nip pressure and/or pressure profile of the nip is measured by installing a pressure sensor, such as a pressure sensitive film, for example, an EMFi film sensor, on the counter roller, rubber roller or roller forming the nip of a printing unit which participates in the printing unit in transferring printing ink onto the surface of the printing substrate, wherein the pressure sensitive film is adapted to produce, in connection with a deformation of the pressure sensor, an electrical signal corresponding to the magnitude of the deformation, causing the rollers forming the nip to rotate in relation to one another such that the nip pressure of the nip causes a deformation of the pressure sensor producing the electrical signal corresponding to the magnitude of the deformation, and calculating the nip pressure and/or pressure profile of the nip by using the electrical signal produced by the deformation of the pressure sensor.

In another embodiment, the measured crosswise tension profile of the printing substrate is compared to a known basic tension profile, a deviation between the basic tension profile and the measured tension profile is analysed, and the printing process is adjusted on the basis of the deviation in the tension profile. In that case, the basic tension profile can be a tension profile obtained from the paper factory for the paper roll or the basic tension profile is based on data collected earlier from the same roller. The basic tension profile can also be a tension profile obtained from another process site in the printing process, such as a tension profile obtained from a measurement after the unwinder.

In particular, the invention relates to a method in which the angle of detachment between a web-like printing substrate and a roller transferring ink is adjusted on the basis of measurement information obtained. In this case, the angle of detachment of the web can be adjusted by changing one or more of the following factors: web tension, position of the next or previous web guidance element, profile of the printing nip, machine speed, web strain, a characteristic of the rubber coating of a roller, process temperature, amount of printing ink, amount of water and dryness of the web. The profile of the printing nip can be changed by heating the metal roller in the nip contact using inductive heating, or otherwise warming the roller or roller coating. In one embodiment, the method according to the invention comprises the adjustment of the printing process by adjusting a roller of the printing press. The roller to be adjusted can be a guide roller, roller nip, dancing roller, leading roller or drawing roller. Correction of nip distortion can be done by changing the position of the rollers in relation to one another or by loading one end of a roller more than the other end. The sum level of nip force can be adjusted by means of pneumatic, hydraulic, or mechanical actuators.

Depending on the embodiment, the tension profile can be measured with a movable film-like pressure sensor that can be installed on the surface of a roller or with a permanent roller which contains a film-like pressure sensor. The information obtained from measurements can also lead to the adjustment of the process which comprises the maintenance of the roller system. Maintenance requirements may be washing a roller, sanding a cylinder, replacing a coating and/or overhauling roller bearings.

The method according to the invention adapts, in particular, to the adjustment of an offset printing process and a gravure printing process. In a gravure printing press, the load force and force profile of the doctor blade can also be measured with sensors installed under the coating of a roller. On the basis of the load force and/or force profile of the doctor blade, the blade load can be adjusted to the desired type by changing the magnitude of the blade force. In one preferred embodiment, in the method according to the invention, the influence of inks and/or dampening water on the web tension profile is measured by executing a web tension profile measurement before and after the printing unit and defining their deviation profile after which the amount of inks and/or dampening water is adjusted, if needed. Adjustment of the printing process and/or printing apparatus can be done manually but the method also enables the use of an automation system. The invention is directed also to a computer program into which is fed information obtained from the method according to the invention and which guides the automated adjusting of the claim as described above. It is obvious to a person skilled in the art that, as technology develops, the basic idea of the invention can be implemented in many different ways. The invention and its embodiments are not then limited only to the examples presented in the above rather many variations are possible within the scope of the claims.

Claims

1. A method for measuring the nip pressure and/or pressure profile in the nip of a printing press, characterized in that a force and/or pressure sensor, such as an electromechanical film sensor, for example, an EMFi film sensor, is installed on the counter roller, rubber roller or roller forming the nip of a printing unit which participates in the printing unit in transferring printing ink onto the paper, plastic or other thin, sheet-like material surface, wherein the pressure sensitive film is adapted to produce, in connection with a deformation of the force and/or pressure sensor, an electrical signal corresponding to the magnitude of the deformation, that the rollers forming the nip are caused to rotate in relation to one another such that the nip pressure of the nip causes a deformation of the force and/or pressure sensor producing an electrical signal corresponding to the deformation of the nip, and that the nip pressure and/or pressure profile of the nip is calculated by using the electrical signal produced by the deformation of the force and/or pressure sensor.

2. A method according to claim 1, characterized in that the force and/or pressure sensor is installed on the counter roller of the printing nip of the printing unit.

3. A method according to claim 1, characterized in that the force and/or pressure sensor is installed on the counter roller of the printing nip of the printing unit, under the rubber coating.

4. A method according to any one of claims 1-3, characterized in that the force and/or pressure sensor is installed on the roller in a spirally slanting manner.

5. A method according to any one of claims 1-4, characterized in that the force and/or pressure sensor is installed in a groove on the roller.

6. A method according to any one of claims 1-5, characterized in that the electrical signal produced by the deformation of the force and/or pressure sensor arranged on the roller is transmitted wirelessly from the roller with the force and/or pressure sensor to a data processing device for the purpose of calculating the nip pressure and/or pressure profile.

7. A method according to any one of claims 1-5, characterized in that the electrical signal produced by the deformation of the force and/or pressure sensor arranged on the roller is transmitted at least partially wirelessly from the roller with the force and/or pressure sensor to the automation system of the printing press for the purpose of calculating the nip pressure and/or pressure profile, wherein the automation system of the printing press will, if needed, adjust the nip on the basis of the calculated nip pressure and/or pressure profile, and/or produce diagnostic information about the nip on the basis of the calculated nip pressure and/or pressure profile, and/or produce an alarm on the basis of the calculated nip pressure and/or pressure profile.

8. An arrangement for measuring the nip pressure and/or pressure profile in the nip of a printing unit of a printing press, characterized in that a force and/or pressure sensor, such as a pressure sensitive film, for example, an EMFi film sensor, is installed on the counter roller, rubber roller or roller forming the nip of a printing unit which participates in the printing unit in transferring printing ink onto the paper, plastic or other thin sheet-like material surface, wherein the pressure sensitive film is adapted to produce, in connection with a deformation of the force and/or pressure sensor, an electrical signal corresponding to the magnitude of the deformation.

9. An arrangement according to claim 8, characterized in that the force and/or pressure sensor is installed on the counter roller of the printing nip of the printing unit.

10. An arrangement according to claim 8, characterized in that the force and/or pressure sensor is installed under the rubber coating of the counter roller of the printing nip.

11. An arrangement according to any one of claims 8-10, characterized in that the force and/or pressure sensor is installed on the roller in a spirally slanting manner.

12. An arrangement according to any one of claims 8—11, characterized in that the force and/or pressure sensor is installed in a groove on the roller.

13. An arrangement according to any one of claims 8-12, characterized in that it comprises a transmission arrangement for transmitting wirelessly the electrical signal produced by the force and/or pressure sensor from the roller with the force and/or pressure sensor for the purpose of calculating the nip pressure and/or pressure profile.

14. An arrangement according to any one of claims 8-12, characterized in that it comprises a transmission arrangement for transmitting at least partially wirelessly the electrical signal produced by the force and/or pressure sensor from the roller with the force and/or pressure sensor to the automation system of the printing press for the purpose of calculating the nip pressure and/or pressure profile, wherein the automation system of the printing press is adapted to adjust the nip, if needed, on the basis of the calculated nip pressure and/or pressure profile, and/or is adapted to produce diagnostic information about the nip on the basis of the calculated nip pressure and/or pressure profile, and/or is adapted to produce an alarm on the basis of the calculated nip pressure and/or pressure profile.

15. A method for adjusting a rotary printing press, characterized in that the crosswise profile of tension in the machine direction of the printing substrate used in the rotary printing press is measured from some process site roller and/or the nip pressure and/or pressure profile is measured from at least one roller forming the nip which participates in the printing unit in transferring printing ink onto the substrate, such as paper, plastic or other thin web-like material surface, and adjusting the angle of detachment between the web-like printing substrate and the roller transferring ink on the basis of the information obtained.