EP2109577A2

EP2109577A2 - Printing press for printing printing-material webs and method for setting and maintaining the register of a printing press of this type

Info

Publication number: EP2109577A2
Application number: EP07848099A
Authority: EP
Inventors: Manfred Loddenkötter
Original assignee: Windmoeller and Hoelscher KG
Current assignee: Windmoeller and Hoelscher KG
Priority date: 2006-12-18
Filing date: 2007-12-14
Publication date: 2009-10-21
Anticipated expiration: 2027-12-14
Also published as: DE102006060212B4; WO2008074732A9; EP2109577B1; DE102006060212A1; WO2008074732A2; WO2008074732A3

Abstract

A printing press for printing printing-material webs is described, which printing press has at least two inking units (10, 20, 30) which in each case have a press nip (45, 46, 47), in which the printing image is transferred onto the printing material (1), and at least one web guiding section (41, 42) which comprises the web path between the at least two press nips (45, 46, 47), and at least one register regulator (50) which sets the maintenance of register of the print before and/or during printing operation. This is characterized by at least one controllable means (25, 35, 51, 52) for the targeted setting and maintaining of a web tension gradient (ΔF41) in a web guiding section (41,42) of the printing-material web (1), which controllable means (25,35,51,52) acts on the printing-material web (1) within the at least one web guiding section (41, 42), und by which controllable means (25,35,51,52) the relevant web guiding section (41,42) can be divided into web guiding part sections (41a,b;42a,b) with a different web tension (F41a,F41b), wherein the register regulator is set up in such a way that it actuates the at least one controllable means (25,35,51,52) for the targeted setting and maintaining of a web tension gradient (ΔF41).

Description

Printing machine for printing substrate webs and method for setting and maintaining the register of such a printing press

The invention relates to a printing press for printing substrate webs and a method for adjusting and maintaining the register of such a printing press. In multi-color rotary presses, there is a need to adjust the register and maintain the appropriate register quality once achieved. For these purposes, methods for setting the method before the start of the printing operation (pre-register method) and method for maintaining the register quality (register or register control method) have been devised and published.

In many of these methods, the relative position, that is to say basically the phase position of the cylinder of the various inking units carrying the print image, is changed relative to one another, thus bringing about the desired registration correction. In this case, therefore, the cylinder carrying the printed image and optionally its drive is the register actuator, that is to say the device component which effects the register correction mechanically.

Alternatively, it is also customary to provide guide rollers between successive inking units whose relative position to the inking units is variable, so that the distance between the inking units changes. In this case, this guide roller and optionally the drive which changes the position of the roller, the register actuator.

EP 1 520 696 A1 shows a machine which prints a printing material web in a counter-printing process. This machine uses both types of register actuators already described. In particular, after the introduction of individual drives for the individual inking units and partly also different individual drives for the various cylinders involved in the printing process of an inking unit, great effort is also expended to early detect register errors during printing operation and correct them by correction signals to the said drives.

In general, a distinction is made in the recognition of the register deviations between the web and the web cylinder processes. In the case of web-to-web processes, register marks are usually printed in the different inking units on the printing material web and the deviation of the same from the desired position is examined. Such a web-path register method is shown for example by DE 43 01 272 A1. In the web-cylinder method, a desired position of the web is measured on the printing cylinders. There are a large number of publications on these various register measuring and control methods, of which the following documents are representative: DE 20 46 131 B2, DE 42 18 760 A1, DE 199 17 773 A1.

Despite the considerable progress made in registering and regulating register quality in recent years, there is still a need for improvement. Thus, it is one of the constant goals of the printing press development to increase the speed at which register errors occurring in the printing operation are corrected. Particularly in the case of row-fed printing presses, which have long web guide sections between the inking units due to their construction, the register quality and the speed at which register errors are eliminated create problems.

Therefore, the object of the present invention is to propose a printing machine in which register errors can be compensated faster. If register errors can be corrected more quickly, less waste will result and register deviation will generally become smaller.

To achieve the object, the invention is based on a printing press for printing substrate webs, which has the following features: at least two inking units each having a printing nip in which the printed image is transferred onto the printing substrate, at least one web guide section which comprises the web path between the at least two press nips,

- At least one register controller, which adjusts the registration of the pressure before and / or during the printing operation.

The object is solved by the characterizing features of claim 1.

In the language of the present application, a nip is the location where the print image is transferred to the substrate. In general, this is done in a nip between a pressure plate and a counter-pressure cylinder. In the most common forms of offset printing, however, the transfer of the printed image takes place in a nip between a blanket cylinder and an impression cylinder. In this case, the printing plate cylinder is upstream of the blanket cylinder. Since a multicolor print image is usually composed of a plurality of monochrome print images, a multicolor print engine contains several color works. In each of these inking units is a printing nip and between the printing nips of the various inking units is a web guide section. To him counts the distance between the printing gaps of the adjacent or successive printing units.

In the case of central cylinder machines, such a web guide section is usually simply the distance between the two pressure gaps which the central cylinder covers by turning. However, it is also conceivable to lift the printing material web between two printing gaps from the central cylinder and, for example, for the purpose of cooling or drying pass over guide rollers on corresponding devices. In the case of series machines, for reasons of construction, a web guiding section, which is by no means negligible in length, results between such pressure gaps. Often, the length of these web guide sections is still deliberately extended in order to pass the web back to such drying or tempering devices that require a long exposure time or distance.

A register controller in the sense of the present application comprises all devices which are necessary for register errors or their causes recognize (usually by measurement), to generate control signals from these (measurement) values (usually by calculation, recourse to empirical values, etc.) to transmit these control signals to actuators or their power controller so that they correct the register error or Take countermeasures.

The way in which the registration error is detected (eg, train orbit or web-cylinder method) and the physical measuring principle are of peripheral interest at first. However, it will be shown below that a register method according to the invention (and thus also a register controller according to the invention) can also operate on the basis of web tension measured values alone-that is to say without the evaluation of register errors. Another possibility of obtaining measured values which can be used as a basis for registering is presented in WO 2004/048093 A2. Here, mechanical markings on the web are measured. These mechanical markings may be increases on the printing material web, the z. B. can be measured when passing through a pressure nip. Here, the force required to carry out the marking through the pressure gap-which manifests itself in, among other things, an increase in the torque of the drives-can be measured. Independently of all these register measuring or monitoring methods, the drives of the cylinders transmitting the printed image (in operative connection with the respective cylinder) are generally suitable as register actuators. According to the prior art, these drives are controlled so that changes the phase position of the print image bearing cylinder adjacent inking units to each other. Of course, this measure in printing presses of the prior art also has an influence on the web tension in the corresponding web tension section. However, the change in the web tension in these machines, which work with a change in the phase position of the printing cylinder, not just by the fact that the means for influencing the web tension on the printing material within the web guide portion acts (as is the subject of the present invention), but the action is made in the nip by the cylinder transferring the print image. In addition, the change in the phase position (as shown below with reference to FIGS It will be understood that there is only a "global" increase in web tension in the entire web guide section, that is, between the two adjacent press nips that define the respective web guide section If, as already noted, the register actuators comprise guide rollers that are in their relative position the printing gaps can be changed, wherein the adjustment is made with any drives, then there is also a "global" increase in web tension in the respective web guide section. With regard to this type of register actuator, however, it must be acknowledged that the influence is often effected within the web path section concerned.

If, as provided in the invention, a controllable means (25,35,51, 52) for selectively impressing and maintaining a Bahnspannungsgradienten (.DELTA.F41) in a web guide portion (41, 42) of the printing substrate (1) acts, arise two web guide sections with different web tension. If two such means for influencing the web tension act on a web guide section, three such subsections with different web tension arise, if n of such means act on the web in a web guide section, n + 1 of such web guide sections are produced.

Already from this explanation it is clear that a means for influencing the web tension generally imparts force to the printing material web in any way - even in the web running direction. Typically, this force lowers the web tension in one and increases the web tension in the other section.

It is to be admitted that even web guiding elements such as guide rollers or turning bars exert such forces, so that even web guide subsections can arise virtually automatically. However, such elements are not controllable means for specifically influencing the printing material web, which are in connection with a register controller and are specifically controlled by the latter for register correction and adjustment, as in the present invention. Also a temporary, thus temporary intervention in the web tension - as in the present invention - is of course not possible with normal guide rolls.

An advantageous embodiment of the invention should therefore be equipped with at least one controllable means for selectively impressing and maintaining a Bahnspannungsgradienten in a web guide portion of the printing material, in which the amount (the force or torque) and the duration of the action are regulated or adjustable , On the basis of internal investigations, the mode of action of the conventional register actuators and the controllable means according to the invention for the purpose of memorizing and maintaining a function are to be compared

Bahnsteuungsgradienten in a web guide portion of the printing substrate to say the following: Serve the print image bearing rollers and their drives as register actuators, then the register correction is effected by an adjustment of the phase position of the cylinder carrying the print image. In this case, the preferred method should be to design the phase shift so that the amount of the arc length on the peripheral surface of the cylinder carrying the print image in the web running direction corresponds to the amount of the measured register error. In particular, in machines with web sections of great length, in series machines and / or in the use of stretchable substrates (such as plastics), the register correction mainly leads to a temporary increase in the web tension in the affected web guide section. A slippage of the printing plate on the web is here rather secondary and also not desired to the full extent.As a result, the stretching of the printing material web changes (also the length of the printed images is changed.) The thus stretched web section is through the normal transport The registration correction becomes effective only when this process has been completed, before a web section having at least the length of the web guide section is printed with reduced print quality. This is also the case with the use of register actuators comprising guide rollers which can be changed in their relative position to the printing nips, the adjustment being made with any of the drives. As already stated, here too there is a "global" increase in the web tension in the entire web guide section, which results in a change in the relevant web stretch. "Stationary state only sets in again as a result of the" removal "of the section of track that has changed in its stretch , in which the desired print quality is achieved, since the registration correction becomes fully effective and the length of the printed images printed by the first inking unit of the web guide section again shows a satisfactory degree of correspondence with the printing length of the second inking unit.

When using controllable means for targeted impressing and maintaining a web tension gradient in a web guide section of the printing material web, the web tension in a web guide section, for example, specifically change so that the measured register error is compensated by the change in web elongation in this section. This is a completely different approach than in the aforementioned methods. It no longer needs a long compensation phase of the web tension, which is printed with limited print quality. In the illustrated case, it is advantageous to use the longer of the two web guide sections to compensate for registration error by changing the web stretch. It is also advantageous if this is the first web guide part section in the web running direction. In a further web guide section, the web tension can be such that the web stretch leads to a satisfactory repeat length. This can be achieved by physical compensation or other adjustments.

For the reasons mentioned above, the register controller for carrying out the method according to the invention should also be set up in a different manner than the register controller in conventional methods. First, it must have the controllable means for selectively impressing and maintaining a web tension gradient in a web guide section of the web Control printing material web and not conventional register actuators. This requires loading of the register controller with corresponding control commands (eg programming) and any kind of signal connection between register controller and the controllable means for the targeted impressing and maintaining a Bahnspannungsgradienten in a web guide section of the printing material ahead. Furthermore, special specifics of the registration have to be considered. Thus, an iterative approach to the full amount of register correction when applying a force is recommended, since the modulus of elasticity of the printing material fluctuates. However, a simple version of a method according to the invention should be able to stretch or "squeeze" a web guide section with, for example, a moment-loaded guide roller by the amount of register error It is advantageous to program register controllers with the aid of data carriers (eg CD DVD or electronic communication means (eg e-mail)) so that the inventive methods can be executed on the corresponding printing press be referred to as electronic data transfer agents.

During a period in which there are no or only slight register errors, the means are maintained the Bahnspannungsgradienten or the different web elongation. In this case, they should exercise a permanent force on the web.

In general, such controllable means for the targeted impressing and maintaining a web tension gradient in a web guide section of the printing material web must - at least temporarily - have mechanical contact with the printing material web within the relevant web guide section in order to influence the web tension there. An advantageous embodiment of such a controllable means for selectively impressing and maintaining a web tension gradient in a web guide portion of Substrate web comprises a roller which can be acted upon in any way with a torque. By "torque" is meant here both a braking "negative" torque which brakes the web and which occurs when the roll or its axis is brought into operative connection with a brake in any way. A "positive" driving torque can be imparted to the guide roll by a drive such as an electric machine Such an embodiment with an electric machine has the advantage that it can usually produce both positive and negative torques Targeted impressions and maintenance of a web tension gradient in a web guide section of the printing material web is a guide roll, which is acted upon by a brake or a motor, for example, by means of a torque control.

However, it is equally possible to provide, for the purpose of loading the web with a force, a roller assembly containing at least one such moment-loaded roller. It can be very advantageous if such an arrangement contains at least one nip.

Controllable means for selectively impressing and maintaining a web tension gradient in a web guide section of the printing substrate web may also comprise surfaces which are brought into frictional contact with the printing substrate web. For this purpose, the objects that contain these surfaces, again with actuators such as linear motors with targeted controllable force against the track should be able to be employed. This can be done by placing an object, such as a beam or bar, against the track of the track. But you can also provide two or more bars that cooperate like a pair of pliers. However, great care must be taken in these procedures to avoid surface damage.

In particular, when materials such as plastics, which have a considerable modulus of elasticity, are printed, it is advantageous to have the effective range of the agent for specifically influencing the printing material web relative close to the next in the web running direction printing nip (ie, just before the end of the respective web run section) provided. This measure takes account of the following fact:

If the controllable means for selectively impressing and maintaining a Bahnspannungsgradienten in a web guide portion of the printing substrate imprinting a force on the web, this acts on the longer part of the web tension section and there leads to a change in the repeat length of the printed images. This change eventually causes the desired register change. If the web is braked, for example, the web tension in the web tension subsection drops. As a result, the repeat length decreases on this longer in the web running direction first web guide portion. After passing through the means, the physically caused repeat length stationary again, since the web tension in the second web guide section in this case is higher than in the first.

The force which is imparted to the web and brings about the different web tension in the two web guide sections is advantageously kept constant if the measured values which the register controller receives have a desired register quality (within a desired range). The register actuators should therefore have the possibility of keeping the tension and thus the web elongation constant in at least one web guide section. This will usually happen just by the entry of a constant force on the web during this period. When the register controller receives measured values indicating a change in the register (or, for example, in the case of monitoring the web tension, or suspecting it), it will control the means for impressing and maintaining the web tension gradient such that it gives the web a different path Impart power. Another advantage of an arrangement of the controllable means for selectively impressing and maintaining a Bahnspannungsgradienten in a web guide section of the printing material just before the corresponding web guide section downstream printing nip comes into play, if the web tension as measured and controlled variable is taken into account in the register control. Usually one will use measuring rollers in which the force exerted by the web on the axle is measured. As a rule, the measurement takes place on the roll axis. If one now measures the web tension fluctuations-preferably in a long first web guide section-many of the machines are already able to achieve satisfactory register qualities on the basis of these measurement results, if one regulates according to a web tension setpoint.

This circumstance can be explained as follows: Particularly in the case of long web guide sections between the inking units, significant contributions to the overall register deviations occur in the web guide sections. This is especially true when these web guide sections are used functionally to dry or cool the web. Of course, fluctuations in the humidity, especially in the case of paper, lead to changes in the length of the substrate web. Against this background, it becomes clear that register errors can occur in this way due to drying efforts or, on the other hand, as a result of increasing moistening. In particular, when printing on plastic webs temperature gradients play a similar role, since the temperature has a significant influence on the moduli of elasticity and thermal expansion of these substances.

Also, disturbances of the web tension in the section, as they occur in the acceleration by inertia forces, are worth mentioning. Inhomogeneities in the printing material as well as a splice pass when changing rolls lead to such web tension disturbances. In particular, the concept with a torque-loaded auxiliary guide roller can compensate for disturbances, in particular with a subordinate web tension control loop, with significantly higher frequency than conventional control systems. The today usual registration accuracy on flexible substrates can be improved with the invention by a factor of 5 -10, so register accuracies on row machines are possible, which can be achieved today only with central cylinder machines. Now, if the first web guide part section covers a large part of the distance - for example 95% - of the entire web guide section, a measuring element is able to quantitatively detect the influence of all these disturbance variables on the web tension in this first large web guide section. Based on these measured values, the means for selectively influencing the web tension can be controlled in such a way that it corrects the influence of all these disturbance variables acting on the first web guide subsection on the web tension. As already mentioned above, a register controller, which only receives measured values of web tension as measured values, is also a register controller in the sense of this application. However, it is also advantageous to use, for example, the very common optical sensors.

Particularly advantageous is a combination of different measuring methods. In view of the extensive combination options, specific advantages of individual combinations must also be taken into account. The control hierarchy must also be taken into account in the combination. If one combines, for example, a method which records a register error that has occurred on the printing material web, or a running error (incorrect positioning of the web to the printing cylinder) with the method described above, in which the web tension is measured, then the web tension is first applied to the web tension Set point to control (internal control loop). The control after the occurring register error or run error follows this regulation. Are within a web guide section several (s) controllable means for selectively impressing and maintaining a

Bahnspannungsgradienten provided in a web guide portion of the printing substrate, so the web guide part section in question can be divided into n + 1 web guide sections with different web tension. In this case, the last means for selectively influencing the web tension is usually assigned the "main register work".

As already stated several times, uses the register method according to the invention, special register actuators. Thus, in this method, the parts that apply force or torque are already multiple described controllable means for selectively impressing and maintaining a Bahnspannungsgradienten in a web guide portion of the printing substrate, which act on the printing material within the at least one web guide portion (ie between the printing gaps), wherein the tension of the printing substrate in this web guide section can be influenced.

In conventional register methods in which the registering is effected by a change in the phase angle of the cylinder transmitting the print image, the actuators are precisely the cylinders carrying the print image in operative connection with their drives. In addition to a combination of different measurement methods that can be used for register control, a combination of methods using different register actuators is also advantageous. Thus, a combination of the inventive method with a controllable means for selectively impressing and maintaining a web tension gradient in a web guide portion of the printing substrate as a register actuator with a method with a cylinder bearing the print image as a register actuator is particularly advantageous if you want to register large amounts. This is the case, for example, during pre-registration. A method with an adjustable in position roll guide could be advantageously combined with the inventive method. Particularly favorable conditions of use for the method according to the invention can be found in the longitudinal register of machines that print packaging material. Due to the longer web guide sections are here mainly stand machines, ie machines in which a cylinder which transmits the printed image on the printing material, a counter-pressure cylinder is assigned to call. Due to the role that the web elongation plays in the process according to the invention, the printing of plastic webs is a preferred field of application. So z. B. in packaging printing materials such as PE, PET, etc. printed. Among the printing methods used in this field are offset, gravure and flexo printing. The operation of packaging gravure printing machines with a method according to the invention is considered to be particularly advantageous. Further advantageous embodiments of the invention are explained below with reference to the figures. The figures show in detail:

Fig. 1 is a gravure printing machine in a lateral schematic view

Fig. 2, the web tension, plotted over the length of

Substrate web in the gravure printing machine, Figure 3 shows a web guide portion of a gravure printing machine in a side schematic view. Fig. 4 is a first control loop for the web guide section in Fig. 3 Fig. 5 shows a second control loop for the

Web guide section in Fig. 3 Fig. 6 The course of the web tension in a

Web guide portion of a state of the art

Registering Technique Fig. 7 The history of the register in a web guide section of a prior art machine in registering

1 shows the course of a printing material web 1 in a gravure printing machine 100 in a schematized schematic diagram. Shown are a total of three printing units 10, 20, 30, between which web guide sections 41, 42 are formed. Before the first printing unit 10 is a web feed section 40th

On a driven feed roller 14, the printing material web 1 is fed and fed to a first printing unit 10, where the printing material is pressed on a form cylinder 12 to a impression roller 1 1. From there, the transition to the downstream with respect to the conveying direction of the printing material located printing units 20, 30 with form cylinders 22, 32 and impression rollers 21, 31. In addition to mere deflection rollers are for guiding the printing material web in each web guide portion 41, 42nd Guiding rollers 13, 23, 24, 33, 34 are provided, on which the respective web tension is measured.

Between the revolving guide rollers 23, 24, 33, 34 according to the invention in each case torque-loaded auxiliary guide rollers 25, 35 are provided, on which the printing substrate 1 runs along.

In this embodiment, the torque-loaded 25, 35 guide rollers and their torque actuators 51, 52 thus play the role of controllable means for impressing a web tension gradient.

Between the nip of the first printing unit 10 and the additional guide roller 25, a first web guide portion 41 a is formed; between the auxiliary guide roller 25 and the printing nip of the second printing unit 20, a second web guide portion 41 b. This also applies analogously to the second web guide section 42 between the printing units 20 and 30, which is divided by the additional guide roller 35 in web guide part sections 42a, 42b.

2 shows the stationary course of the web tension acting on the printing material web at different positions of the gravure printing press. At the periphery of the first guide roller 23, a web tension F41a is measured in the first web guide portion 41a, and at the periphery of the second guide roller 24 a force which by definition corresponds to a web tension F41b in the second web guide portion. The resulting strains, as shown by the dot-dash line in the lower part, are proportional to the web tensions and inversely proportional to the E moduli.

Behind the torque-loaded auxiliary guide rollers 25, 35, ie directly in front of the respective printing gap, the self-adjusting web tension is stationary. A braking torque on the auxiliary guide roller 25, 35 reduces the stationary web tension in front of it; a drive torque increases the web tension here.

While the elongation behind the auxiliary guide roller 25, 35 thus remains constant, the elongation changes before the respective torque-loaded auxiliary guide roller, so that the register of the two successive Printing units 10, 20 and 20, 30 to each other is changed. The register change results from the fact that the print motif of the printing unit 10, 20 located in each case upstream of the torque-loaded auxiliary guide roller 25, 35 has a different length and thus the number of repetitions between the printing units 10, 20, 30 varies.

In Figure 3 of the web guide portion 41 shown schematically, a force diagram is shown, with respect to an incremental web location at the point at which the printing material 1 runs from the torque-loaded auxiliary guide roller 25, cut free in equilibrium of the forces acting.

The web tension F41 a, which adjusts itself in the web guide portion 41 a, results from the difference of the self-adjusting force F41 b in the web guide portion 41 b and the resulting from the moment of the auxiliary guide roller 25 circumferential force F25.

Behind the last printing nip, a register measuring device 50 is arranged, which determines a possible register deviation on the printing material, for example, via a digital camera and image-recognizing method. Due to the angular amount φ at the cylinder 22 carrying the print image, it is indicated that register control can also be achieved by shifting the phase position of the two forme cylinders 12 and 22 relative to one another. In state-of-the-art machines, such an approach is preferred. With regard to the present invention, this type of registration is used inter alia in an embodiment according to FIG.

FIG. 4 shows a first simple control loop 200 which represents the web guiding section shown in FIG. FIG. 3 shows the first web guide section 41 of the printing press shown in FIG. The starting point for the considerations in FIG. 4 is the force or web tension FE which lies in front of the first printing unit of the web guide section 41. By the transfer member 201 is indicated that the web tension F41 b in the stationary case of the aforementioned web tension FE and the ratio of the elastic moduli E41 / E40 of Web guide sections 40 and 41 results. As already explained above, differences between the moduli of elasticity can mainly be caused by temperature differences. It is important in this context to note that the elongation of the web in the inlet of the two pressure gaps has to be the same or sets at identical circumferential speed of the forme cylinder 12 and 22 equal. The transfer elements 206 and 207 and the addition point downstream of them indicate that the register between the forme cylinders 12 and 22 adjusts as a function of the web strains ε41 b and ε41 a and thus leads to the register actual value dRist. At this point, it is advisable to note that the web tension F41 a is equal to the F41 b, when the torque-loaded guide roller 25 just runs smoothly. The register deviation is measured by a register measuring device 50, compared with a desired value dRsetpoint and fed to a register controller 202. Register regulator 202 applies a moment to the brake which applies force F25 to the web at the circumference of the roll. In the simplest case, the amount of this force is proportional to the register error, which is also indicated by the transfer member 202. For the stationary case, the transmission member 205 illustrates the dependence of the web tension F41 a on the force F25 and the web tension F41 b described above.

For the transient case, the transmission elements 203 and 204, with the subsequent addition or subtraction points, illustrate the temporally limited effects of a change of the force F25 on the web stresses F41 a and F41 b.

FIG. 5 shows a somewhat more complex control loop. Again, the formation of the web tension F41 b is illustrated by means of the transfer element 301. Likewise, again with the transfer elements 306 and 307 and the subsequent addition term the influence on the register is illustrated. However, this time the measured registration error does not directly produce a momentary impact on the roller 25, but rather a phase adjustment of the forme cylinder 22, which generates an extension εr in the web guide section 41b. The strain εr changes the web tension F41b. The web tension F41 a results from an inner Web tension control loop from web tension F41 b. In the stationary case, Delta F is the amount by which F41 a is set lower than F41 b, so that disturbances of the web tension in the positive and negative directions can be compensated by increasing or decreasing the braking torque. F41 a is measured with the measuring roller 23 (FIG. 3), the measured value is fed back to a reference point 323 and regulated via the transmission element 321. The delay element 322 causes the web tension F41 a to remain constant during a brief change in the web tension F41 b. With such a cascaded control loop 300, the total fluctuations, which occur in the usually very long web guide portion 41 a by disturbances such as temperature and humidity fluctuations, acceleration forces, defects in the material to be printed, etc., even before they become effective register. In summary, therefore, it should be emphasized that the control of the web tension in the embodiment of Figure 5 by an influence on the web within the web guide section (which here with a torque-loaded guide roller 25) is made. Here, a gradient is impressed and possibly maintained. Thus, the register actuator is formed here by the torque-loaded guide roller 25 and its torque plate 51. With the aid of the inner control loop and this pair 25, 51, in the exemplary embodiment illustrated in FIG. 5, initially only the web fluctuations are corrected. The compensation but still occurring register error, which can manifest themselves on the substrate or by the position of the printing material against a plate cylinder 12, 22 are then made again by a phase adjustment of the angular position of the forme cylinder (Here, the forme cylinder 12, 22 and their not drives shown the register actuators). In the detection of the aforementioned register errors, optical measuring methods can be used very advantageously. This combination contributes to the enormous speed with which register errors can be compensated with the system shown in FIG. Finally, it should be noted that the terms "web tension" and "force" (which acts on the web) in the present document merge into one another, since these sizes in the present context closely together and the term "web tension" has become established in the printing press world, while "force" is a fundamental physical quantity. However, in the present document, "web tension" has been used preferentially with respect to the web tension found in portions of the web (as in F41b). "Force" has been used in relation to punctiform web-mediated forces such as F25.

FIG. 6 contains a diagram showing the course of the web tension F _A in a web guide section of a machine of the prior art. The machine is registered by making a printing image bearing roller, which closes the web guide portion in the web running direction, a phase shift. FIG. 7 shows the course of the associated register at the same points in time. During the period Ti, stationary conditions prevail in the web guide section, which as a rule adjust themselves in such web guide sections.

At time T _A , the phase shift of the second pressure roller in the web running direction is performed in order to equalize the register difference ΔR between the register actual value Ri and the register setpoint value R ₂ . This phase shift is comparatively extremely fast. Therefore, the web tension, represented by the graph G _F, steeply increases. However, the decrease of the web tension to the initial value Fi and the setting of the register to the target value R ₂ continue during the periods T ₂ and T ₃ . The adaptation process does not run linearly as indicated by the lines L _F and L _R , but exponentially in the form of a decay function. During these periods a transient balancing process takes place in which printing is done with inferior quality. As already mentioned, the entire web section stretched by the phase shift of the printing cylinder must first have passed the second printing nip in the web running direction before stationary states again occur at time T3 and the register change becomes effective. In the first order, the duration of this compensation process is proportional to the length of the web guide section and anti-proportional to the printing speed. When an inventive method in a printing machine, as outlined by the figures 1 and 3 is performed by the register correction is made by a deliberate change in length of the web in the web guide portion 41 a (by stretching or by contraction of the web by lower web tension, what causes a Bahnspannientenienten to web tension F41 b), then find the transient compensation operations that precede the full effect of the registration, only in the web guide portion 41 b instead. This is naturally shorter than the entire web guide portion 41. The shorter the web guide portion 41 b, the faster the transient compensation. The longer the first web guide portion 41 a, the easier (with less force or torque) to stretch the web by a certain amount. Therefore, aspect ratios of significantly less than 1 between the second 41b and the first web guide portion (eg, 20, 7 or 3%) are advantageous.

Claims

Printing machine for printing substrate webs and methods for setting and maintaining the register of such a printing press patent claims

1. Printing machine for printing on substrate webs, which has the following features:

- At least two inking units (10,20,30), each having a printing nip (45,46,47), in which the printed image is transferred to the substrate (1),

at least one web guide section (41, 42) which comprises the web path between the at least two pressure nips (45, 46, 47),

- At least one register controller (50), which adjusts the registration of the pressure before and / or during the printing operation, characterized in that

at least one controllable means (25, 35, 51, 52) for the purpose of impressing and maintaining a web tension gradient (ΔF41) in a web guiding section (41, 42) of the printing material web (1),

which (25, 35, 51, 52) acts on the printing material web (1) within the at least one web guide section (41, 42),

- And by which (25,35,51, 52) of the respective web guide portion (41, 42) in web guide portion sections (41 a, b, 42a, b) with different web tension (F41 a, F41 b) can be dismantled, wherein the register controller such is set up, that it controls the at least one controllable means (25,35,51, 52) for the targeted imprinting and maintaining a web tension gradient (.DELTA.F41).

2. Printing machine according to claim 1, characterized in that the controllable means (25, 35, 51, 52) for targeted impressing and maintaining a web tension gradient (ΔF41) in a web guide section (41, 42) of the printing substrate web (1) comprises at least one roller ( 25,35), which can be acted upon by a negative (brake) or positive (drive) torque.

3. Printing machine according to the preceding claim, characterized in that at least one of the following means (51, 52) for acting on the roller with torque in operative connection with the roller:

a mechanical or electrical brake,

an eddy current brake,

a hysteresis brake,

a magnetic powder brake,

- A drive, preferably by an electric machine.

4. Printing machine according to one of the preceding claims, characterized in that the controllable means (25,35,51, 52) for selectively impressing and maintaining a web tension gradient (.DELTA.F41) in a web guide portion (41, 42) of the printing substrate (1) at least one Identifies surface that can be brought in frictional connection to the printing material web (1) with a controllable actuator such that the web tension (F41 a, F41 b) changes.

5. Printing machine according to one of the preceding claims, characterized in that the web guide portion (41 a; 42a) of a web guide portion (41, 42) which in the web running direction (z) the location of the action of the controllable means (25,35,51, 52 ) for selectively impressing and maintaining a web tension gradient (.DELTA.F41) in a web guide portion (41, 42) of the printing material web (1) is upstream, is longer the web guide portion (41 b, 42 b) of the same web guide portion (41, 42), in the web running direction (z) the location of the action of the controllable means (25,35,51, 52) for selectively impressing and maintaining a Bahnspannungsgradienten (.DELTA.F41) in one Web guide portion (41, 42) of the printing substrate (1) follows.

6. Printing machine according to the preceding claim, characterized in that the aspect ratio of the second web guide portion (41 b, 42 b) to the first web guide portion (41 a, 42 a) of a web guide portion (41, 42), at most 0.75 but preferably 0.5 , more preferably 0.2 or even 0.1.

7. Printing machine according to one of the preceding claims, characterized by at least one means (13,23,24,33,34) for measuring the web tension.

8. Printing machine according to the preceding claim, characterized by at least one means (13,23,24,33,34) for measuring the web tension, which is positioned such that with it (13,23,24,33,34) web tension ( F41 a, F41 b) in a web guide portion (41 a, 41 b, 42 a, 42 b) is measurable.

9. Printing machine according to one of the two preceding claims, characterized by a signal connection (60) between the at least one register regulator (50) and at least one means (13,23,24,33,34) for measuring the web tension.

10. Printing machine according to one of the two preceding claims, characterized in that the register controller (50) comprises a control unit which generates and outputs control signals, which to the at least one controllable means (25,35,51, 52) for targeted influencing the voltage of the printing substrate are transmitted and this driving.

1 1. A method for setting and maintaining the register quality of a printing press, which has the following features:

- At least one register controller (50) which adjusts the register accuracy of the pressure before and / or during the printing operation, wherein the method is characterized in that the register controller (50) provides control and / or control signals, due to which the web tension (F41 a , F41 b) is acted upon within a web guide section (41, 42) such that at least two web guide subsections (41 a, 41 b, 42 a, 42 b) with different web tension (F 41 a, F 41 b) from the one web guide section (41, 42) arise.

12. The method according to the preceding claim, characterized in that the register controller (50) of the generation of the control and / or control signals at least partially web tension values (F41 a, F41 b) is based.

13. The method according to any one of the preceding claims, characterized in that the register controller (50) sets the generation of the control and / or control signals based at least partially register errors.

14. The method according to one of the two preceding claims, characterized in that the control after the web tension (F41 a, F41 b) precedes the control of the register errors.

15. The method according to any one of the preceding claims, characterized in that the web tension (F41 a, F41 b) is acted in a web guide portion at different locations such that from the one web guide portion (41, 42) at least three, but preferably four or more web guide sections (41 a, 41 b, 42 a, 42 b) with different web tension (F41 a, F41 b) arise.

16. The method according to the preceding claim, characterized in that the register controller (50) provides control and / or control signals, the influence on the web tension (F41 a, F41 b) of the rear or the rear web tension section (41 b, 42 b) have ,

17. The method according to any one of the preceding claims, characterized in that before or during the printing operation control and / or control signals are provided, due to which the phase position (φ) of the print image bearing cylinders (12,22) of the at least two inking units (10 , 20,30) are changed against each other.