Digital printing press and operating method

Abstract

In a method for operating a digital printing press, a sheet (4) is aligned in an alignment station (1) and subsequently printed in a printing station (2). The sheet (4) is detected in the alignment station (1) by means of a first sensor (11, 12) and aligned by means of alignment rollers (15, 16). The sheet (4) is detected again by means of a second sensor (22, 23) after its alignment in the alignment station (1), and the signal from the second sensor (22, 23) is used to adjust the alignment station (1). Furthermore, a digital printing press suitable for performing the above operating method is provided.

Description

Technical Field

[0001] The present invention relates to a method for operating a digital printing press and a digital printing press wherein pages are aligned in an alignment station and subsequently printed in a printing station, the printing press comprising an alignment station for aligning pages and a printing station for printing the aligned pages.

[0002] In this type of method, alignment should be used to ensure that the appropriate orientation of the printed pages is achieved in the printing station. Background Technology

[0003] For example, methods and machines of the type described in the introduction are described in EP 1 110 888 B1. Summary of the Invention

[0004] The objective of this invention is to provide an additional method of operating a digital printing press and to provide a digital printing press suitable for performing the method of operating.

[0005] This task is solved by a method for operating a digital printing press, wherein pages are aligned in an alignment station and subsequently printed in a printing station, characterized in that the pages are detected in the alignment station by means of a first sensor and aligned by means of an alignment roller, the pages are detected by means of a second sensor after their alignment in the alignment station, and the signal from the second sensor is used to adjust the alignment station.

[0006] Furthermore, this task is also solved by a digital printing press comprising an alignment station for aligning pages and a printing station for printing the aligned pages, characterized in that the alignment station has a first sensor for detecting the pages and an alignment roller for aligning the pages, a second sensor for re-detecting the pages is arranged downstream of the first sensor in the page conveying direction, and the second sensor is incorporated into an adjustment loop for adjusting the alignment station.

[0007] The advantage of the method and machine of the present invention is that the control enables the compensation of errors on the rollers. These errors include diameter errors, which may be due to manufacturing defects or wear.

[0008] The following extensions to the method of the present invention can be implemented individually or in any combination thereof: The detection of the pages by the second sensor can be performed in the entrance area of ​​the printing station. The pages can be conveyed through an alignment path located between the alignment roller and the second sensor, the alignment path deviating from the nominal size of the alignment roller's circumference or a multiple thereof by a maximum of 5% of the nominal size of the circumference.

[0009] During sheet tilt correction, the alignment rollers can be driven asynchronously by different motors, which are part of the adjustment loop.

[0010] The slider of the alignment station, in which the alignment roller is rotatably supported, can be laterally shifted relative to the conveying direction during sheet lateral alignment correction.

[0011] The following extensions of the machine of the present invention can be implemented individually or in any combination thereof: The second sensor can be arranged in the entrance area of ​​the printing station. The length of the alignment path between the alignment roller and the second sensor deviates from the nominal size of the circumference of the alignment roller, or from a multiple thereof, by a maximum of 5% of the nominal size of the circumference.

[0012] The alignment roller can be connected to different motors, which are part of the adjustment circuit.

[0013] The alignment station may have a slider that can be laterally displaced relative to the conveying direction, and the alignment roller may be rotatably supported in the slider. Attached Figure Description

[0014] Further embodiments of the method and the machine of the present invention are also derived from the following description of the embodiments and the accompanying drawings. The drawings are as follows.

[0015] Figure 1 A digital printing press is shown.

[0016] Figure 2 Showing according to Figure 1 The cross-sectional view of section line II-II in the diagram.

[0017] Figure 3 Show Figure 1 A fragment.

[0018] Figure 4 A schematic diagram of the adjustment loop used for landscape format printing is shown.

[0019] Figure 5 A schematic diagram of the adjustment loop used for portrait format printing is shown. Detailed Implementation

[0020] Figure 1 (Side view) and Figure 2(Top view) shows a digital printing press, including an alignment station 1 and a printing station 2 for inkjet printing. Sheets 4 are conveyed on a plane 5 along a horizontal transport direction 6 to the alignment station 1 by means of roller pairs 3. There, the orientation of the corresponding sheet 4 is optically detected at the side 7 of the sheet 4 by line sensors 8 and 9 and at the front 10 of the sheet 4 by first sensors 11 and 12. If the sheet orientation deviates from the orientation necessary for printing in the printing station 2, lateral and / or slant corrections are performed in the alignment station 1.

[0021] During lateral alignment, the slider 14, along with the alignment rollers 15 and 16 coaxially and rotatably supported therein, is moved in a horizontal transverse direction 17 by the driver 13. This transverse direction is orthogonal to the conveying direction 6. Here, the sheet 4 to be aligned is clamped between the two alignment rollers 15 and 16 and the cooperating clamping roller 18 (only one of the two clamping rollers is visible in the figure), so that the sheet 4 moves laterally together on the plane 5.

[0022] During slant correction, an alignment roller 15 is driven to rotate by an electric motor 19, and another alignment roller 16 is driven to rotate by another electric motor 20, wherein the two alignment rollers 15 and 16 rotate at different speeds. Due to the asynchronous rotation of the alignment rollers 15 and 16, the sheet 4 conveyed by them rotates about its (imaginary) vertical axis, which is orthogonal to the plane 5.

[0023] The properly aligned printed sheet 4 continues to be conveyed from the alignment station 1 to the printing station 2 on the plane 5. In the entry area 21 of the printing station 2, before reaching the print head, second sensors 22 and 23 are arranged for optical detection of the front edge 10 of the input sheet 4. The second sensors 22 and 23 send signals to the electronic control system indicating the actual orientation of the sheet 4. This electronic control system includes... Figure 4 or Figure 5 The regulating loop 24.

[0024] When aligning subsequent pages (which follow page 4 already in the entry area 21 in the page flow) through alignment station 1, the alignment station is adjusted by an electronic control system according to signals sent by second sensors 22 and 23 so that the orientation of the subsequent pages approaches the nominal orientation during alignment.

[0025] By re-measuring the position and slant of the front edge 10 of each page 4 after it has been transferred from the alignment station 1 to the printing station 2, errors in the alignment process can be corrected via the adjustment loop 24. This compensates for deviations in the diameters of the alignment rollers 15 and 16 from their nominal or target dimensions due to manufacturing tolerances or material wear. Without this compensation, such deviations would impair proper page alignment during printing.

[0026] Line sensors 8 and 9 are embedded in plane 5 in a staggered manner along the conveying direction 6 and are configured as CCD sensors. First sensors 11 and 12 are embedded in plane 5 in a staggered manner along the transverse direction 17 and are configured as reflective light scanners. Second sensors 22 and 23 are also embedded in plane 5 in a staggered manner along the transverse direction 17 and are configured as reflective light scanners.

[0027] exist Figure 3 The alignment path a is shown, which is the distance between the center points of the alignment rollers 15 and 16 to be measured and the second sensors 22 and 23 in the conveying direction 6. The diameter d of the alignment rollers 15 and 16 is also given. The length of the alignment path a is at least approximately equal to the circumference of the alignment rollers 15 and 16 or an integer multiple thereof, i.e., a ≈ n × π × d (n = 1, 2, 3…). Here, the tolerance range is preferably ±5%. Ideally: a = n × π × d (n = 1, 2, 3…). Therefore, the corresponding alignment rollers 15 and 16 perform one or more complete (360°) rotations when aligning each page 4. The advantage is that alignment errors caused by roundness deviations of the alignment rollers 15 and 16 can also be corrected by adjusting the circuit 24. Such roundness deviations may be caused by rubber wear during roller manufacturing or operation.

[0028] Figure 4 The adjustment loop 24 is shown when adjusting the alignment station 1 during a printing job of page 4 in landscape format. Such landscape printing jobs also... Figure 2 As shown in the figure. The adjustment loop 24, in addition to the previously mentioned components, includes a regulator 25 and a memory 26 for the most recent n measurements (n = 1, 2, 3…, e.g., n = 10). Reference numeral "27" indicates the actual position and actual slant of page 4 before the alignment process. Reference numeral "28" indicates the measured position and measured slant of the front edge 10 before the alignment process. Reference numeral "29" indicates the actual position and actual slant of page 4 after the alignment process. Reference numeral "30" indicates the measured position and measured slant of the front edge 10 after the alignment process. Reference numeral "31" indicates the average value stored in memory 26. Reference numeral "32" indicates an alignment error. Reference numeral "33" indicates the target position and target slant of the front edge 10 after the alignment process.

[0029] Figure 5 The adjustment loop 24 is shown when adjusting alignment station 1 during a printing job of page 4 in portrait format (Portrait format). Such portrait printing jobs are only shown in the figure. Figure 5 As shown. Combined Figure 4 The same applies to those in regulating loop 24. Figure 5 The explanations of the elements present in it also apply to... Figure 5 Furthermore, in Figure 5 In the figure, reference numeral "34" indicates the nominal position and nominal angle of side 7 after the alignment process. Reference numeral "35" indicates the determined angle between front 10 and side 7. The position and angle of side 7 measured before the alignment process are indicated by reference numeral "36", and the position and angle of side 7 determined after the alignment process are indicated by reference numeral "37".

[0030] List of reference numerals in the attached diagram: 1. Alignment Station 2 Printing Station 3 roller pairs 4 pages 5 planes 6. Conveying direction 7. Side 8 rows of sensors 9 rows of sensors 10 in front 11 Sensors 12 sensors 13 drives 14 sliders 15 Alignment Rollers 16 Alignment Rollers 17. Horizontal direction 18 Pressure Rollers 19 motors 20 motors 21 Entrance Area 22 sensors 23 Sensors 24. Regulation circuit 25 Regulator 26. Memory 27. Actual value before alignment 28 Front edge measurement before alignment 29. Aligned actual value 30. Front measurement after alignment 31 Average 32 Alignment error 33 Aligned front rating 34 Aligned side ratings 35 Angle between the front and side 36 Side measurements before alignment 37. Side value determined after alignment a alignment path d. Diameter.

Claims

1. A method for operating a digital printing press, wherein, Page (4) is aligned in alignment station (1) and subsequently printed in printing station (2), characterized in that, The page (4) is detected in the alignment station (1) by means of the first sensor (11, 12) and aligned by means of the alignment rollers (15, 16). The page (4) is detected again by means of the second sensor (22, 23) after its alignment at the alignment station (1), and The signals from the second sensor (22, 23) are used to adjust the alignment station (1).

2. The method according to claim 1, characterized in that, The detection of the sheet (4) by the second sensor (22, 23) is carried out in the entrance area (21) of the printing station (2).

3. The method according to claim 1, characterized in that, The page (4) is conveyed via an alignment path (a) located between the alignment rollers (15, 16) and the second sensor (22, 23), the alignment path deviating from the nominal size of the circumference of the alignment rollers (15, 16) or an integer multiple thereof by a maximum of 5% of the nominal size of the circumference.

4. The method according to any one of claims 1 to 3, characterized in that, During sheet tilt correction, the alignment rollers (15, 16) are asynchronously driven by different motors (19, 20), which are components of the adjustment loop (24).

5. The method according to any one of claims 1 to 3, characterized in that, The alignment rollers (15, 16) are rotatably supported in the slider (14) of the alignment station (1), which is laterally displaced relative to the conveying direction (6) during sheet side alignment.

6. A digital printing press for performing the method according to claim 1, comprising an alignment station (1) for aligning pages (4) and a printing station (2) for printing the aligned pages (4), characterized in that, The alignment station (1) has a first sensor (11, 12) for detecting the page (4) and an alignment roller (15, 16) for aligning the page (4). A second sensor (22, 23) for re-detecting the page (4) is arranged downstream of the first sensor (11, 12) in the conveying direction (6) of the page (4), and The second sensor (22, 23) is incorporated into the adjustment loop (24) for adjusting the alignment station (1).

7. The digital printing press according to claim 6, characterized in that, The second sensor (22, 23) is arranged in the entrance area (21) of the printing station (2).

8. The digital printing press according to claim 6, characterized in that, The length of the alignment path (a) between the alignment rollers (15, 16) and the second sensor (22, 23) deviates from the nominal size of the circumference of the alignment rollers (15, 16) or a multiple thereof by a maximum of 5% of the nominal size of the circumference.

9. The digital printing press according to any one of claims 6 to 8, characterized in that, The alignment rollers (15, 16) are connected to different motors (19, 20), which are components of the adjustment circuit (24).

10. The digital printing press according to any one of claims 6 to 8, characterized in that, The alignment station (1) has a slider (14) which is laterally displaceable relative to the conveying direction (6), and the alignment rollers (15, 16) are rotatably supported in the slider (14).

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