EP2481585B1 - Method and device for processing a sheet of a printing material into printed products - Google Patents

Description

The invention relates to a method for processing a web of a printing material into printed products and to an apparatus for carrying out the method.

Rotary printing machines in the offset and gravure printing process and high-performance digital printing machines print webs of a substrate from a roll. After printing, the web must be cut and optionally folded into sheets. The web usually has to travel a longer distance from the print location to the finishing devices which cut and fold the printed sheets. In this case, the printed image must be synchronized to the cross cutter and the folding device, so that the sheets are cut and / or folded correctly. In this case, print marks are printed at relevant points on the web, which are identified by means of recognition systems. Print marks are in addition to the printed image applied symbols, usually a bar, which indicate by their position on the substrate, where a follow-up process, such as. Folding and / or cutting, to take place. The corresponding further processing devices read for this purpose by means of optical readout units, the print marks. In this case, the print marks can vary for different finishing processes, for example, different print marks for cutting and folding are well known. Accordingly, these print marks are also referred to as cut or fold marks. The known recognition methods assume that the print marks are free, i. that in a Nutzspur the web only print marks are, or that at least in the vicinity of the print marks no other printing is available.

In the context of print marks, there are other, related measurement and control problems that are being solved today with additional special sensors. In particular, in digital printing from the role of the sheet after printing on the web still be identified, because after the cross cutter the different sheets have to be merged into printed products. It is absolutely necessary to be able to reliably identify the first sheet of a printed product, which may consist of several single sheets. Next, the web can move laterally. Therefore, the transverse position of the web must be detected, which is accomplished with other special sensors. Furthermore, in known methods with multiple uses arranged side by side on the web, in which the printed web is cut into a plurality of individual webs in the transport direction, it is advantageous to be able to readjust the position of the cutting as well.

Print marks and in particular cut marks are today usually created so that in the transport direction of the web a track of at least a few mm width is left unprinted and only the print marks, especially the crop marks are printed in this track. A fast photo sensor detects the occurrence of a stroke or other simple symbol of a print mark with virtually no time delay and sets a signal with only a few microseconds delay, which is processed for example by a servo control unit of the cross cutter. From the known theoretical target position and the actual measured actual position, the servo control unit can determine and correct the deviation. However, clearing a track in the print mark web produces more trimming and thus more waste.

In the DE102008059584A1 is described in detail how print engines can be synchronized to each other by means of print marks. In particular, it describes that print marks can not only be strokes, but also more complex printed symbols. It also describes how matrix cameras can be used instead of ordinary light sensors. The synchronization of printing units is basically the same problem as the synchronization of subsequent processing devices to the cross-cutting of the printed web. The disadvantage of these methods, however, is that they are only applicable if the print marks are free, that is none other printing in the immediate vicinity at least in the direction of the printed web is present. Light scanners as well as matrix cameras, which read the usual print marks today, can not reliably distinguish the print marks from the rest of the print. With a so-called window technique can be attempted to activate the light sensor or the camera only in a known, short window in which the print mark must pass under the light sensor or camera. However, the unprinted area between two sheets must be so large that the variation of the transport path is smaller than the unprinted area with the print marks. Thus, usually much trimming and thus costly loss of paper is generated again.

Methods are also known, such as printing units in rotary printing presses, which control the exact position of the printing position of the various inking units. High-resolution digital cameras are used to analyze images of the print taken at approximately known positions of the print substrate, whereby the position of the various print images can be determined against each other. With such a method one could basically do without print marks and determine via images of the sheet imprint and their analysis, where to fold and cut. However, these methods are expensive and also difficult to implement for the finishing area, which is especially true for digital printing, in which the printing of the sheet is constantly changing.

From the European patent application EP2062738 For example, a method and a device are known in which a code which is read in by a further processing device is printed in a separate track of the paper web. The code contains indications which allow the further processing devices to make new adjustments to the processing device by searching and reading in the code. However, the imprinted position of the code has no direct relation to the function of the code, which means that a code printed by a few millimeters has no influence on the further processing devices which read and interpret the code.

In the DE-A-103 38 973 a method and apparatus for disturbance detection during transport of a material web is described. By means of a sensor unit connected to a computing unit, for example a CCD camera, a register mark applied to the material web or at least a part of the printed image is detected. Downstream of the sensor unit, a cutting roller for transverse cutting of the material web is arranged. The arithmetic unit compares the acquired data with the data supplied by an encoder of the cutting roller and regulates the angular position and / or the speed of the cutting roller with a longitudinal displacement of the printed image until the cross section takes place at the desired location between the printed images of the web.

It is therefore the object to provide a method and an apparatus for processing a web of a printing material in which the synchronization of the web of the printing material with the further processing can be made more cost effective and flexible even in the early stage.

The object is achieved by a method and a device according to the independent claims.

1. a) Aufbringen mindestens einer einem auf die Bahn aufgedruckten Druckbogen zugeordneten Druckmarke auf eine Nutzspur der Bahn, wobei die mindestens eine Druckmarke eine kodierte Druckmarke aufweist,
2. b) Aufnehmen mindestens eines Bildes, das einen Bereich der Bahn abbildet, in dem sich die mindestens eine aufgebrachte Druckmarke befindet,
3. c) Suchen nach und Identifizieren der mindestens einen Druckmarke in dem mindestens einen aufgenommenen Bild,
4. d) Bestimmen der Position der Druckmarke in dem mindestens einen aufgenommenen Bild und aus der bestimmten Position erfolgendes Ableiten einer Position der Druckmarke auf der Bahn, wobei die Lage einer Kante der Bahn bezogen auf ein stationäres Referenzelement, welches maschinenlesbare Markierungen aufweist, aus dem mindestens einen Bild bestimmt wird, und die Position der Druckmarke auf der Bahn bezogen auf das stationäre Referenzelement und/oder auf die Kante der Bahn aus dem mindestens einen Bild ermittelt wird,
5. e) in Abhängigkeit von der Position der Druckmarke auf der Bahn erfolgendes Bestimmen mindestens eines Korrekturwerts zur Synchronisierung einer nachfolgenden Weiterverarbeitung mit der Bahn.

The process according to the invention for processing the web of a printing substrate into printed products comprises the steps

1. a) applying at least one print mark associated with a printed sheet printed on the web to a payload track of the web, the at least one print mark having an encoded print mark,
2. b) taking at least one image depicting a portion of the web in which the at least one applied print mark is located,
3. c) searching for and identifying the at least one print mark in the at least one captured image,
4. d) determining the position of the print mark in the at least one captured image and from the determined position deriving a position of the print mark on the web, the position of an edge of the web relative to a stationary reference element having machine readable markings from the at least one Image is determined, and the position of the print mark on the web relative to the stationary reference element and / or on the edge of the web is determined from the at least one image,
5. e) depending on the position of the print mark on the web, determining at least one correction value for synchronizing a subsequent further processing with the web.

In contrast to the conventional printing marks known from the prior art, which merely indicate the position of process steps to be carried out, encoded print marks contain references to the positioning of conventional print marks and / or references to information which is required in the further processing process, such as the thickness of the substrate, the number of the sheet, the format or type of the printed product.

The device according to the invention for processing a web of a printing material into printed products comprises an image acquisition system for taking pictures, which is connected to an image processing system for evaluating the images, and a control unit for the image acquisition system and the image processing system, which are used for the control the process steps of the inventive method is configured, wherein before or behind the web, a stationary reference element provided with substantially parallel to the web, machine-readable markings and is arranged in particular overlapping to the web.

An advantage of the method and device according to the invention is that no free track is required in the transport direction of the web, since the print marks can be printed in the payload track of the web. Due to the use of coded print marks, it is also possible to identify the area of the web currently located in a further processing device. On the one hand, these advantages lead to a saving in the printing material, which lowers the production costs. On the other hand, the processing process is more flexible, since due to the coding of the print marks position information of the web or printed on the web sheets can be determined, so that subsequent processing steps can be easily adapted to the currently valid requirements of the further processing device. The flexibility is particularly important in digital printing, since constantly changing formats of the substrate must be processed and the editions can be so small that they include only one copy.

In the device according to the invention, a stationary reference element is provided, which has machine-readable markings. The reference element extends the flexibility of the device according to the invention by supporting the generation of correction values for the synchronization of the web with the subsequent further processing, which will be described in more detail below in connection with particularly preferred embodiments of the invention.

• Fig. 1 eine Seitenansicht einer beispielhaften Druckweiterverarbeitungsanlage,
• Fig. 2 ein stationäres Referenzelement,
• Fig. 3 eine Draufsicht auf die Bahn der Anlage aus Fig. 1 in einer ersten Situation, mit einer im Sichtbereich des Bilderfassungssystems befindlichen Druckmarke,
• Fig. 4 eine Draufsicht auf die Bahn der Anlage aus Fig. 1 in einer zweiten Situation, in der sich keine Druckmarke im Sichtbereich des Bilderfassungssystems befindet und
• Fig. 5 ein aufgenommenes Bild gemäss Fig. 3, in vergrösserter Darstellung.

Further advantageous embodiments of the invention will become apparent from the following description with reference to the figures. Show it:

• Fig. 1 a side view of an exemplary print finishing plant,
• Fig. 2 a stationary reference element,
• Fig. 3 a plan view of the path of the plant Fig. 1 in a first situation, with a print mark located in the field of vision of the image acquisition system,
• Fig. 4 a plan view of the path of the plant Fig. 1 in a second situation where there is no print mark in the field of view of the image capture system and
• Fig. 5 a recorded image according to Fig. 3 , in an enlarged view.

In the figures, like reference numerals designate like or equivalent components.

Fig. 1 shows a side view of a simplified processing plant P, in which an exemplary embodiment of the device V is used. A web 10 of a printing material is unwound from a roll 1 and enters a printing machine 50. The printing press 50 comprises a printing unit 52 and a drive 51, preferably a first servo unit, for transporting the web 10 in a transport direction T. The drive 51 lays essentially the speed of the printing material, which consists of paper in the described embodiment. Of course, other substrates, such as films are suitable.

The printed web 10 coming from the printing press 50 is cut into individual printed sheets in a further processing device 60 designed as a cross cutter. The cross cutter is an example of a further processing device 60, but other devices may be considered, such as a folding device. The further processing device 60 includes a second servo unit 61, which cooperates with the first servo unit 51 to adjust or maintain the tension of the web 10. Due to the position of the second servo unit 61 is also the position of the web 10 with known a certain deviation. The deviation results above all from inhomogeneities of the web 10 and from the slippage between the web 10 and drive rollers of the first and second servo units 51, 61, not shown here. The further processing device 60 additionally comprises a cutting drum 62 with an exemplary knife 63, designed in particular as a drum knife ,

Between printing machine 50 and further processing device 60, an exemplary embodiment of the inventive device V is arranged. It is also possible to arrange a plurality of further processing devices 60, each with its own device V, along the path 10. The device V comprises an image acquisition system 30, an image processing system 40 and a control unit 80. In addition, a stationary reference element 20 is provided with machine-readable markings arranged substantially parallel to the web 10 and designed, for example, as a reference line or barcodes. The markings are related to Fig. 2 explained in detail. The machine-readable marking 21 formed as a reference line and the tip of the knife 63 define a distance L, which is preferably chosen as short as possible. The structure of the stationary reference element 20 is associated with Fig. 2 and the function related to Fig. 3 . 4 and 5 explained in detail. The control unit 80 is connected via control lines to the image acquisition and image processing system 30, 40 and controls them. Preferably, it is further connected to a control unit 64 of the further processing device 60. Furthermore, the control unit 80 may be connected to a central system control, which is not shown here. This has the advantage that programming adjustments or inputs of correction values, information on the printing and on the printed print marks, etc., can be made directly from a central control panel of the system. The connections of the control unit 80 with the other components via data and control lines, which may be designed as a data bus system. The imaging system 30 in this example includes a camera 35, but may include multiple cameras. The camera 35 may in particular be a matrix camera or a line camera. The data bus system includes a Data line 71 for the transmission of the camera data, in particular of recorded images, to the image processing system 40. Control signals for triggering the recording of images are sent in this example from the control unit 80 via a control line 70 to the camera 35. In this case, the control unit 80 notifies the further processing device 60, for example, the position of a cutting mark. The further processing device 60 can now resynchronize the cutting drum 62 accordingly. The control signal for triggering the recording of an image 31 can also come from the further processing device 60, in which case the image processing system does not know any position information of the web 10 and only has to transmit the value of the distance L associated with the corresponding control signal to the further processing device 60 in a sufficiently short time , The data bus system further comprises a cut line setting control line 73 and a line 72 for transferring a position value from the second servo unit 61 to the control unit 80. The lines 70, 71, 72, 73 are configured to provide the data with a required accuracy can be transmitted. For example, the data line 71 can have 16 individual lines for a 16-bit data width. This is known to the person skilled in the art and will not be explained in detail.

Fig. 2 shows an example of a stationary reference element 20 with machine-readable marks 21 formed as a reference line or scale; 22a-22d. The stationary reference element 20 is preferably a fixedly mounted plate which is as close as possible to the web 10 and substantially parallel thereto. In this case, the web 10 facing surface of the plate is carried out in a color which offers a maximum possible contrast with the color of the markings 22a-22d printed thereon and / or the reference line designed as a mark 21. Preferably, the surface of the plate is executed in black color, while the markings 21, 22a-22d are shown in white color. Depending on the requirement, only the mark 21 designed as a reference line can be present or only the markings 22a-22d are used. The reference line 21 is approximately at the center of one of the camera 35 recorded image 31 is arranged. The markers 22a-22d represent an example of a scale easily interpretable by the image processing system 40. The markers 22a-22d in this example are short barcodes, hereafter abbreviated codes, which have numerical values of, for example, 0, 1, 2, .... 99 can represent. The lines of the markings 22a-22d are offset from one another so that the individual short bar codes are not superimposed. The numbers represented by the short bar code increase from left to right and represent the position of their own first black and white transition, for example in mm. The geometrical quantities, such as the distance between individual markings 22a-22d in a row, the line spacing of the markers 22a-22d, the height of the markings 22a-22d, etc., are known or transmitted to the image processing system 40. The location of all the first black and white transitions of each individual block of short bar codes can be used to increase the accuracy of detection of the markers 22a-22d. Other encodings are also possible. The web 10 has two lateral edges 13 and 15. By means of the markings 22a-22d, the position of the edge 13 of the web 10 relative to the stationary reference element 20 can be determined from the image 31. This is related to Fig. 3 explained in more detail. Of course, the reference element and the device V can also be arranged so that the position of the edge 15 can be determined. A Nutzspur the web 10 is denoted by N. The Nutzspur N is understood as the area of the printing of the web 10, which is visible later in the finished printed product. As in Fig. 3 can be seen, the web 10 in each case in the region of the edges 13, 15 on a narrow, non-printed track. These two tracks do not belong to the Nutzspur N. The Nutzspur N can also be arranged so that only on one side of the web 10, an unprinted track is present. If the payload track N has the same width as the track 10, the unprinted tracks are eliminated.

Fig. 3 shows a section of the printed web 10 seen from the direction of the camera 35. The stationary reference element 20 is overlapped by the web 10 in this example and is located behind the web 10. Overlapping is always ensured to reliably determine the position of the edge 13. Becomes For example, if a narrow web 10 is used, the stationary reference element 20 can be displaced correspondingly transversely to the transport direction T of the web 10 in order to ensure the overlap. Depending on the recording field of the camera 35, this can also be moved transversely to the web 10 in the said case. However, the stationary reference element 20 may also be arranged in front of the web 10, provided that it does not cover the print marks 11, 12 printed on the web 10. To the left of the web 10, an image 31 taken by the camera 35 is shown. This image 31 comprises at least a part of the stationary reference element 20 and a region of the web 10 which is sufficiently large for the detection of print marks 11, 12 Fig. 1 illustrated control unit 80 controls the camera 35 so that the web 10 is preferably imaged gapless in a wide track, for example, 10 cm. The timing of the respective control signals is derived from the knowledge of the position of the web 10 from the second servo unit 61. In this case, control signals are sent to the camera 35 at regular intervals of, for example, a few centimeters. For each control signal, the control unit 80 notes the current position of the printing material, which is done by taking place via the line 72 query the further processing device 60. The frequency of the control signals emitted for recording images 31 can also be changed during operation, which happens in particular automatically. The control signals could also be triggered directly by the further processing device 60. In this case, only the further processing device 60 has to store the exact position at which the respective image 31 has been taken.

In Fig. 3 FIG. 12 illustrates a situation in which the image capture system 30 has captured an image 31 and the image processing system 40 in the image 31 identifies a coded print mark 11 and an associated conventional print mark 12 formed as a cut mark. In the present case, the general term print mark is understood to include the coded print mark 11 and the conventional print mark 12 formed as a cut mark. It is also possible to use a conventional printing mark other than the cutting mark. The print mark 11, 12 is preferably in a, in particular unprinted, area of the web 10 is added between two successive printed sheets printed on the web as in Fig. 3 you can see. Since in this area, in which the web 10 is later cut into sheets, there is always a zone of a few millimeters of unprinted printing material, in this zone always a coded print mark 11 and possibly a corresponding conventional print mark 12 with a known, geometric Reference printed to the remaining printing. The coding of the print mark 11 represents a designation which does not appear anywhere else in the remaining print image of the payload track N of the web 10, in particular a one-dimensional or a two-dimensional barcode, for example a data matrix code, by means of which a printed sheet and / or a printed product are uniquely identified can. Particularly suitable is a longer bar code, for example the widely used code 128, which represents a 12-digit decimal number.

Possible codes of the print mark 11 of a printed sheet and / or of a printed product can be communicated to the image processing system 40 before the execution of step c) of the method according to the invention, ie the search for printed marks 11, 12 in FIG.

The position of the print mark 11, 12 is determined from the image 31 with reference to the mark 21 formed as a reference line and / or on the edge 13 of the web 10. Thereafter, the image processing system 40 calculates a shift (offset) of the print mark 11, 12 with respect to the reference line of the stationary reference element 20. The control device 80 adds one of the detected shift of the print mark 11, 12 corresponding value to the current position of the printing material and shares the further processing device on the Control line 73 with. The further processing device 60 knows with the distance L and the geometric path length of the web 10 from the center of the camera 35 to the knife 63. Due to the knowledge of the current position of the printing material, the further processing device 60 is able to correct the position of the knife 63 so in that it cuts through the web 10 precisely at the print mark 12 designed as a cut mark.

Fig. 4 shows a second situation in which camera 35 has received a control pulse for taking an image 31 before the coded print mark 11 and / or the conventional print mark 12 is within the field of view of the camera 35. In this case, the image processing system 40 unsuccessfully searches the image 31 for a print mark and finishes the evaluation therewith.

Fig. 5 shows the picture 31 Fig. 3 in an enlarged view, based on which the evaluation of the position detection of the print mark 11, 12 will be described in more detail below. Seen transversely to the transport direction T, the absolute position of the web 10 can be determined from the distance 33 of a black-and-white transition of the mark 22b formed here as a short bar code from the edge 13 of the web 10. To determine the position of the edge 13, one uses the fact that the printing material is unprinted a few millimeters around the printing marks 11, 12, so that it is always possible, the edge 13 of the web 10 against the black background of the stationary reference element 20th to recognize. It also follows that the detection of the edge 13 of the web 10 also detects a tear of the web 10, since no edge 13 is detected in the image 31. Furthermore, the orientation of the web 10 can be determined from the image 31 such that an angle between the edge 13 of the web 10 and the reference line of the stationary reference element 20 is determined and compared with a reference angle, in particular of 90 °. If a deviation is detected, this means that the web 10 is not aligned correctly and the subsequent processing step can probably not be carried out accurately. In such a case, the control unit 80 may generate a warning, which may be sent, for example, to the central system controller. It is also conceivable that the angular deviation is corrected by means of actuators.

The distance 34 corresponds to the position of the coded print mark 11 with respect to the edge 13 of the web 10 transversely to the transport direction T. In this case, the starting position of the barcode is first determined or, if already known, retrieved. The absolute position of the barcode results from the addition of the distance 33 and 34. Since the image processing system 40 has information about the type of printed matter Barcodes has, can be closed from the location of the found barcode on the location of the conventional print mark 12.

In the transport direction T, the distance 32 corresponds to the offset of the coded print mark 11 from the mark 21 formed as a reference line. The accuracy of the determination of the offset 32 can be increased by evaluating the position of the cut mark. If the reference element 20 is completely covered by the web 10 and the reference line is not visible, the image center of the camera 35 can be used as a reference.

The determined distances 32, 33, 34 thus provide correction values for synchronizing the further processing device 60 with the web 10 as a function of the position of the print mark 11, 12. In this case, in particular, the position of the coded print mark 11 is forwarded to the control unit 80 of the image processing system 40, i. the lateral or longitudinal displacement of the print mark 11, 12 with respect to a reference position or its angle or position relative to the web 10. The reference position is either the machine-readable marks 21, 22a, 22b, 22c, 22d of the stationary reference element 20 or the position of the camera 35. To adjust the cutting position, the correction values are finally transferred to the control unit 64 of the further processing device 60.

In another example, not shown here, a folding device can be provided as further processing device 60. In this case, the correction value to be transferred would be a position of a transverse fold of the print sheet on the web 10. This position could result from the already explained determination of a cut mark, in this case a fold mark.

Another use of the device V may be that a current tension of the web 10 is determined. This is done by measuring the size of a print mark 11, 12th

In the first case, by determining the size of a print mark 11, 12, in particular a width 36 of the coded print mark 11 perpendicular to the transport direction T, the tension of the web 10 can be calculated. Since the width of the web 10 decreases in proportion to the tensile stress in the transport direction, the width 36 of the coded print mark 11 decreases as the tensile stress increases.

In the second case, a reference size of the scale of the camera 35 from the ratio of the actual size of the print mark 11, 12 and recorded in a reference plane of the web 10 image size of the print mark 11, 12 are given. This reference variable can be compared during operation of the system with a calculated scale. When the web 10 sags, the image 31 is smaller than a fictitious image located in the reference plane. Consequently, the reference size would not agree with the calculated scale. From this difference, the deviation of the distance of the camera 35 from the print mark 11, 12 can be calculated, whereby further a measure of the tension of the web 10 can be derived. For example, known algorithms accurately calculate distances of two parallel edges in a print image subpixel.

The tension of the web 10 can also be determined absolutely if, from a plurality of temporally successive, overlapping images 31, the changing scale calculated for each image 31 is used to determine the oscillation frequency of the paper web.

A coded print mark, which is preferably a barcode and serves as a substitute or for finding conventional print marks, can be used at the same time for identifying the print sheets and also be referred to as an intelligent print mark due to its diverse application possibilities. In other words, the correction value from step e) of the method according to the invention may be an identification code associated with at least one printed sheet for a product tracking in the course of subsequent further processing steps. Especially in digital printing, it is important to verify which signature is currently in a finishing device. Particularly suitable is a "speaking" coding, which recognizes to which sheet number of a later printed product the encoded print mark belongs and / or in which the later printed product is uniquely identified. Advantageously, the print engine controller reports to the control unit 80 which print marks have recently been printed. In this way it can be achieved that barcodes or barcode-like symbols associated with the product printing do not trigger any misinterpretations, since the control unit accepts only the currently valid barcodes. The device V can therefore also be used only to reliably and uniquely identify a printed sheet in order to ensure an accurate product tracking and to be able to trigger further actions downstream, controlled by the product identification.

In summary, the device V in the described embodiment, which essentially comprises an image processing system 40, a control unit 80 with one or more connected cameras 35 and lines 70, 71, 72, 73 for internal data exchange and data exchange with external units 61, 62 able to search for coded print marks 11, 12 in a passing web 10. A control signal, which occurs at intervals of a few centimeters of feed of the web 10, triggers a picking up of an image 31 from the web 10. At the same time, the instantaneous position of the servo units 51, 61 is stored, for example, by the control unit 64 of the cross cutter and possibly by the control unit 80 of the image processing system 40. The image processing system 40 detects on the image 31 whether a coded print mark 11, 12 is present. If such has been found, then the exact position of the coded print mark 11 or the associated conventional print mark 12 is determined. Further, the position of the reference line formed as a mark 21 of the reference element 20 is determined, which is advantageously approximately in the center of the image. The position information of the print mark 11, 12 or an identification of a print sheet associated with the print mark is transmitted to the execution of subsequent processing steps to the formed as a cross cutter further processing device 60.

Another advantage of the device V is that by using a stationary reference element 20, which may be part of the device V, eliminating the calibration of the camera 35, or that at least then a calibration is fully automatic when no substrate is present. If the stationary reference element 20 is visible, then smaller, mechanical changes in the camera position due to vibrations, thermal deformation, etc. have no or negligible influence on the measurement. Again, each image capture allows recalibration of important parameters, which are described by the camera position and its imaging properties. For example, in the evaluation of an image 31, a deviation of the position of the mark 21, which is visible as a reference line, from the image center of the image acquisition system 30 can be determined. Thus, an exchange of the camera 35 can be done without calibration and smaller, mechanical changes can be compensated by redetermining the parameters.

Since the print marks no longer have to lie in an unprinted track, one can choose, at least in the direction transverse to the web 10, the position of the print marks where it is the best in the process, e.g. in the middle of the bow. This is particularly advantageous, for example, in the case of a plurality of partial webs, in order to ensure the positioning of the partial webs in a positionally correct manner to form a web composite. If a plurality of webs 10 are guided parallel to one another, the offset 32 of the coded print mark 11 in the transport direction T, the distance 33 of a scale mark 22a-d from the edge 13 and the distance 34 of the position of the coded print mark 11 from the edge 13 can be used for each sub-web be determined and the position of the partial webs are matched by means of actuators.

A further advantage is the saving of sensors, since instead of using different sensors for each measured variable (cutting mark position, measurement of web edges, sheet identification, position opposite the web), as has hitherto been customary, only one sensor, eg a matrix camera, has to be used, to measure the sizes mentioned.

In the figures, only a barcode is used as coded print mark 11 by way of example. Other symbols that do not occur in the payload track N can also be used as coded print marks.

The further processing of the web 10 is carried out after the synchronization on the basis of the correction value determined in step e) of the method according to the invention. In this case, not only cross cutter, as exemplified in the described embodiment, use coded print marks, but any further processing device, the synchronous operation such as punching and / or labeling and / or labeling and / or perforating and / or folding and / or cutting on or must perform on the web can be synchronized by means of coded print marks. The web can, as explained in the exemplary embodiment, be printed with a printing machine upstream of the further processing device. It is also possible for the further processing device to supply a previously printed web from the roll.

While advantageous embodiments of the invention have been shown and described, the invention is not limited to them, but may be otherwise practiced and practiced within the scope of the following claims.

Claims (14)

1. Method for processing a web (10) of a printing material into printed products, comprising the steps:

   a) applying at least one print mark (11, 12) assigned to a printed sheet (14) printed on the web (10), on a usable width (N) of the web (10), the at least one print mark (11, 12) including a coded print mark (11),

   b) recording at least one image (31) showing a region of the web (10) in which the at least one applied print mark (11, 12) is located,

   c) searching for and identifying the at least one print mark (11, 12) in the at least one recorded image (31),

   d) determining the position (32; 33, 34) of the print mark (11, 12) in the at least one recorded image (31) and deriving a position of the print mark (11, 12) on the web (10) from the position determined, the position of an edge (13, 15) of the web (10) in relation to a stationary reference element (20) which has machine-readable markings (21, 22a, 22b, 22c, 22d) being determined from the at least one image (31), and the position (32; 34) of the print mark (11, 12) on the web (10) in relation to the stationary reference element (20) and/or to the edge (13, 15) of the web (10) being determined from the at least one image (31),

   e) determining, in dependence on the position of the print mark (11, 12) on the web (10), at least one correction value for synchronising a subsequent further processing operation with the web (10).
2. Method according to Claim 1, characterised in that the at least one print mark (11, 12) is applied to an, in particular unprinted, section between two successive printed sheets (14) of the web (10).
3. Method according to Claim 1, characterised in that the orientation of the web (10) is determined from the image (31) by determining, and comparing to a reference angle, an angle between the edge (13, 15) of the web (10) and the machine-readable markings (21, 22a, 22b, 22c, 22d) of the stationary reference element (20).
4. Method according to any one of Claims 1 to 3, characterised in that the coding of the print mark (11) corresponds to a designation by means of which a printed sheet (14) and/or a printed product is unambiguously identified, in particular a one-dimensional or two-dimensional barcode being used as the coded print mark (11).
5. Method according to any one of Claims 1 to 4, characterised in that the codings of the print mark (11) of a printed sheet and/or of a printed product are transmitted to an image processing system (40) prior to execution of step c).
6. Method according to any one of Claims 1 to 5, characterised in that the print mark (11, 12) includes a conventional print mark (12), in particular a cutting mark.
7. Method according to any one of Claims 1 to 6, characterised in that the correction value denotes the position of the print mark (11, 12) on the web (10) in relation to a reference position.
8. Method according to any one of Claims 1 to 7, characterised in that the correction value denotes a position, designated for the further processing, of a printed sheet (14) on the web (10).
9. Method according to any one of Claims 1 to 8, characterised in that a frequency of control signals for the recording of images (31) is adapted during operation and, in particular, automatically.
10. Method according to any one of Claims 1 to 9, characterised in that an actual tension of the web (10) is determined by measuring the size of the coded print mark (11).
11. Method according to any one of Claims 1 to 10, characterised in that the coded print mark (11) is used as an identification code assigned to at least one printed sheet (14) and serving to track a product in the course of the further processing.
12. Method according to any one of Claims 1 to 11, characterised in that, in a step f), the further processing of the web (10) is carried out after the synchronisation on the basis of the correction value determined in step e).
13. Device (V) for processing a web (10) of a printing material into printed products, comprising an image capturing system (30) for recording images (31) which is directed at the printed side of the web (10) and which is connected to an image processing system (40) for evaluating the images (31) and to a control unit (80) for the image capturing system (30) and the image processing system (40), which control unit (80) is configured to control the process steps according to any one of Claims 1 to 12, wherein a stationary reference element (20) having machine-readable markings (21, 22a, 22b, 22c, 22d) arranged substantially parallel to the web (10) is provided in front of or behind the web (10), and in particular is arranged overlapping the web (10).
14. Device according to Claim 13, characterised in that the image capturing system (30) includes at least one camera (35), in particular a matrix camera.

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