EP1170237B1 - Method for aligning sheet material - Google Patents

Abstract

The invention relates to a method for the alignment of sheet-like material (1). Its alignment occurs via rotation elements (25), wherein the sheet-like material (1) is rotated around its central axis in order to print on the front and backsides. During the rotation of the sheet-like material (1) around its central axis, the material's leading edge (23) remains in its aligned position. Into the conveyor surface (9) is incorporated a sensor pair (30), preferably in the form of CCD line sensors, with which the sheet-like material (1) is aligned on the same lateral edge (24) following the rotation, as is the case during the alignment procedure of the sheet-like material (1) before it is rotated around its center axis.

Description

The invention relates to a method and a device for improving the alignment accuracy of an arcuate material which, prior to further processing in a conveying plane, is precisely aligned with respect to its twisting position, its inclined position in the running direction, according to the preambles of claims 1, 5 and 6 ,

DE 44 16 564 A1 relates to a sheet alignment device. This device for aligning a sheet moving along a substantially planar transport path permits alignment of a moving sheet in a plurality of orthogonal directions, for example transversely to the transport path, in the direction of the transport path and to eliminate skews of the sheet material with respect to its transport path. The apparatus comprises a first roller assembly having a first pinch roller mounted to rotate about an axis which is in a plane parallel to the plane of the transport path and substantially perpendicular to the direction of sheet transport along the first roller Transport track runs. A second roller assembly has a second pinch roller mounted to rotate about an axis which is in a plane parallel to the plane of the transport path and substantially perpendicular to the direction of transport along the transport path. There is further provided a third roller assembly having a third pinch roller mounted to rotate about an axis which is in a plane parallel to the plane of the transport path and substantially perpendicular to the direction of sheet transport runs along the transport path. The third roller assembly, which is rotatable about an axis which lies in a plane parallel to the plane of the transport path and extends substantially perpendicular to the direction of sheet transport along the transport path, is movable along its axis of rotation in a direction transverse to the transport path. Finally, a control device is provided, which with the first and second or third roller assembly is operatively connected and selectively controls the rotation of the first and second roller assembly to align the leading edge of a rotating in the direction of sheet transport along the transport path sheet, arranged in a direction perpendicular to the sheet transport position. The controller further controls the rotation and transverse movement of the third roller assembly to align the moving sheet in the direction transverse to the sheet transport direction and in the direction in which the sheet travels along the transport path.

The known from DE 44 16 564 A1 sheet alignment device is able to meet the required alignment inaccuracies only to a limited extent. In order to achieve the required alignment inaccuracies, a comprehensive Modifi cation of the sheet alignment device of DE 44 16 564 A1 is required, which does not appear economical.

In sheet-fed rotary printing presses, which operate on the offset principle, the sheets are conveyed on the feed table in a shingled arrangement, before they are aligned at the feed table level provided side and Ziehmarken. After alignment of the sheet material, this is passed in the aligned state to a pre-gripper, which accelerates the sheet-shaped material to the machine speed and passes to a pre-gripper downstream paper-guiding cylinder. Other alignment concepts usually use cylindrical rollers, on whose core a rubber coating is added. With such a configuration, when alignment of sheet material is performed during its advancement by varying the speed between a left and right roll engaging the sheet material, the sheet material undergoes rotation about a pivot located or resting on the stationary roll the feed is located outside the lower speed roller or between the two rollers.

If the printing on the front and back sides of the sheet material is done in two passes with the same printing units, the orientation is twice of the sheet material essential. If the leading edge is to be retained during the turn, the sheet is rotated about the central axis in the running direction, the sheet side edges being reversed. If the lateral alignment takes place with only one sensor, the reference edge for the post-processing is lost, so that the quality of the registration of the print image on the front side to the printed image on the back side of the sheet-like material is limited by the angular tolerances and size variations of the paper format ,

From US-A-5,697,609 a method and a device of the type mentioned are also known.

The invention is based on the known from the prior art solutions and the indicated technical problem, the task to significantly improve the alignment accuracy of the sheet material during its feed in sheet travel direction.

According to the invention, this object is solved by the features of claim 1.

The achievable with the present invention advantages are to be seen in all that now the influences of angular tolerances and size variations of each substrate to be printed in relation to the quality of alignment are eliminated, since the sheet material during the first pass and after turning to a and the same side edge is aligned. The lateral alignment with only one line sensor would mean a loss of the reference edge for post-processing, while the two inventively provided line sensors within the alignment plane in both the Perfecting as well as the perfecting allowed a reference to one and the same position.

According to the method proposed by the invention, the line sensors in the conveying plane for the sheet material within the areas of Provided side edges of the sheet material, wherein the line-shaped extension perpendicular to the direction of the arcuate material sweeps over such an area in which the respective sheet side edge is likely to be encountered. The greater the extent of the linearly arranged line sensors is dimensioned perpendicular to the direction of the sheet material, the greater the flexibility of the processable substrate format.

In a further embodiment of the method proposed according to the invention, the same measuring point is always used to align the sheet-like material on the side edge. As a result, the orientation of the sheet material after its turn in a turning module is independent of the printing material tolerance, such. B. lateral shrinkage of the printing substrate. The determination of the position of the side edge of the sheet material via perpendicular to the direction of the sheet material oriented sensor lines of the line sensors. As line sensors, in an advantageous embodiment, CCD line sensors can be arranged in the sheet running plane within a feed device of sheet-like material. The alignment according to the method proposed according to the invention takes place in the region of regions of the respective reference side edge of the sheet-like material adjacent to its front edge. By evaluating the offset of the respective front region of the side edges with respect to the leading edge of the sheet-shaped material, smallest offsets can be measured by the line sensors arranged in the conveying plane of the sheet material and corrected by the downstream segment rolls. A recording of the lateral offset of the rear portions of the side edge of the sheet material would delay the detection of the offset of the side edges to one side, on the other hand, the adjusting at the trailing edge of the sheet material offset would be sized so large that it is outside of the recognition - and detection range of the CCD line sensors would lie.

The inventively proposed device for detecting the lateral position of an arcuate material by means of a pair of sensors, which in the conveying plane is arranged, in particular on sheet-processing printing machines or according to the electrography principle or the electrophotography principle working machines are used, or other digital printing presses are used. It is irrelevant whether an image on the surface of image-forming or image-bearing cylinders of enumerated printers or printing machines on the application of a toner is generated, which is then fixed or the image is produced according to other methods on the surface of image-transmitting components. Essential for the transfer of the printed image on the surface of the sheet material is its correct orientation with respect to its direction of travel through the printing press or the printer.

Reference to the drawings, the invention will be explained in more detail below.

Figur 1

eine sich einstellende Lageabweichung eines bedruckten Druckbildes relativ zur dieses aufnehmenden Bedruckstofffläche,

Figur 2

eine durch einen Drehversatz gekennzeichneten Versatz des Druckbildes auf dem bogenförmigen Material,

Figur 3

einen Versatz der auf Unterseite und Oberseite eines bogenförmigen Materials in Schön- und Wiederdruck aufgedruckten Druckbildes,

Figur 4

die Seitenansicht eines Bogeneinlaufbereiches einer bogenverarbeitenden Maschine in schematischer Wiedergabe,

Figur 5

die Draufsicht auf die Ausrichtekomponenten, die Sensorik sowie die Antriebe für das bogenförmige Material relativ zu dessen Laufrichtung ausrichtenden Rotationselementen,

Figur 6

die oberhalb der Bogenförderebene des bogenförmigen Materials als Segmentrollen ausgebildeten Rotationselemente und

Figur 7

die Ausrichtung eines bogenförmigen Materials mit den Antrieben der die Ausrichtung bewirkenden Segmentrollen.

It shows:

FIG. 1

a self-adjusting positional deviation of a printed print image relative to this receiving substrate surface,

FIG. 2

an offset of the printed image on the sheet material characterized by a rotational offset,

FIG. 3

an offset of printed on the bottom and top of an arcuate material in beautiful and reprinted printed image,

FIG. 4

the side view of a sheet inlet region of a sheet-processing machine in a schematic representation,

FIG. 5

the top view of the alignment components, the sensors and the drives for the sheet material relative to the direction of rotation aligning rotational elements,

FIG. 6

the above the sheet conveying plane of the sheet material formed as segment rollers rotation elements and

FIG. 7

the orientation of an arcuate material with the drives of the alignment causing segment rolls.

From the illustration according to FIG. 1, an arcuate material oriented at right angles to its feed direction 22, for example a printed sheet 1, emerges. The printed sheet 1 contains on its surface a printed image 2, which is surrounded by a frame-like edge 3. The deviations from Δx or Δy marked within the printing surface 2 and the frame 3, which designate positional errors in the x and y directions 4 and 5, can be set on the surface of the printed sheet 1 when printing the printed image 2. The deviations denoted by reference numerals 4 and 5 are positional deviations, whereas in the illustration according to FIG. 2 angle deviations δ θ of the printed image two are shown with respect to its position on the printed sheet 1.

From the illustration according to FIG. 2, the angle errors Δφ that occur are identified by reference numeral 6. The printed image 2 can be printed in the indicated positions on the surface of the printing material 1, wherein this is conveyed in the sheet running direction with its leading edge 23 ahead.

The illustration according to FIG. 3 shows, in a schematic view, the so-called reversible register, the reference character 7 being used to characterize the offsets between the printed images 2 on the front and back sides of the sheet-like material 1. These are designated in the illustration according to FIG. The reversible fuser plays a particular role in translucent papers of low grammages and extremely light paper weight as well as in booklet printing.

From the illustration according to FIG. 4, the interface of sheet alignment and emergence onto a conveyor belt is shown schematically in a side view. An around a caster 11 and a control roller 12 circulating conveyor belt 10, on the surface of the sheet-like material 1 is received in the conveying plane 9, is an alignment unit. 8 upstream. After passage of the alignment unit 8, which will be described in more detail below, reaches the aligned sheet material 1 on the surface of the conveyor belt 10 in the conveying plane 9. After passage of the caster 11, the sheet material 1 by means of a positioning flap or Anstelllippe, which in Anstellrichtung 13 is movable, charged. The Anstelllippe or Anstellklappe may be a plastic component, which can be moved from a salaried position 13.1 in a parked position 13.2. This is shown here only schematically in solid or dashed lines, wherein for employment a separate drive in the form of a pneumatically switching actuator, an electric drive can be provided, as well as a job by manual means is conceivable.

By means of the positioning flap or adjusting lip is a pressing of the sheet material 1 on the surface of the conveyor belt 10, wherein at the moment of adjusting the sheet-shaped material 1 is located in its aligned state. After passage of the pressure element of the recorded on the surface of the conveyor belt 10 arc passes a charging unit 14. This charging unit 14 is housed within a hood-shaped cover an electrode 15, which for a static charge of the sheet material 1 and thus for its adhesion to the surface of it supporting conveyor belt 10 provides. The loading unit 14, which is shown only schematically in the illustration according to FIG. 4, is followed by a front edge sensor 17. This consists of a below the sheet conveying plane 3 arranged radiation source 18, which is preceded by a lens assembly 19. The radiation field 20 emanating from the lens arrangement 19 penetrates the sheet conveying plane 9 and strikes a diaphragm arrangement which is provided above the conveying plane 9 of the sheet-like material 1. The diaphragm arrangement is arranged downstream of a receiver 21, which senses the presence of a front edge 23 of the sheet-like material 1 and transmits it in accordance with the radiation which is transmitted through the diaphragm arrangement.

From the illustration according to FIG. 5, the alignment unit 8 can be seen in plan view, the components of which reproduce here in a schematic representation are. The alignment unit 8 is reached by an arcuate material 1, which is conveyed in the conveying direction 22. The front edge 23 of the sheet material 1 is offset with respect to the conveying direction 22 of the sheet-like material 1, whereby an oblique course of the side edge 24 of the sheet-like material 1 sets. As soon as the sheet leading edge 23 lying in an oblique position with respect to the running direction 22 overflows a first light barrier 26, the drives 27, designated M1 or M2, which drive rotational elements 25 via individual axes 32, are accelerated to the feed rate. The triggering of the drives 27 (M1 or M2) triggered via the light barrier 26 ensures that each copy of the sheet-like material 1 comes into contact with identical peripheral sections of the rotary elements 25, which in a preferred embodiment are designed as segmented rollers. Any self-adjusting differences in the feed movements, which could be due to dimensional and shape tolerances of the two rotation elements 25, thereby occur in each copy of the sheet material 1 in the same way and can be easily herauskalibriert.

After passing through the first light barrier 26, the two rotation elements 25 are set in rotation, the sheet material 1 is transported at feed speed via one of the first light barrier 26 downstream another light barrier 30.1. This light barrier 30.1 may be arranged, for example, downstream of a CCD sensor line 30, which extends substantially perpendicular to the running direction of the sheet-like material 1. Due to the line-shaped configuration of the sensor line 30, the side areas of all common printing material formats can be detected.

As soon as the first of the two sensors of the light barrier 30.1 has detected the sheet leading edge 23 of the sheet material 1, a counter unit begins to count in motor steps. The counting process is then ended and the detected difference stored when the second sensor of the light barrier 30.1 switches. The CCD sensor lines of the sensor pair 30 are embedded in the sheet running plane so that they do not transport the sheet material 1 hinder. From the count determined in this way, a correction value is determined, which is forwarded as an additional feed to the last started segment roller drive, ie either the drive 27, which is designated M 1, or to the drive 27, which is designated M 2. As a result, the corresponding rotary body 25 designed as a segmented roller is accelerated to an increased feed speed until the predetermined path difference is completely compensated and the sheet leading edge 23 of the sheet-like material 1 is aligned exactly perpendicular to the conveying direction 22 of the sheet-shaped material 1. At the end of this correction process, the sheet leading edge 23 is oriented exactly perpendicular to the conveying direction 22.

After correction, the sheet-like material 1 is conveyed in the conveying direction 22 of the first pair of segment rollers 25 passed to this downstream pair of rotary body 25, which may be received on a common axis 31. Now, via the drive 27 or M 1 and the drive 27 (M 2) driven segment roller pair 25 is turned off and moves in its rest position in which it does not touch the sheet material 1 with its peripheral surfaces.

The now correctly aligned with respect to its angular position arcuate material 1 now runs on the sensor array 30, e.g. CCD line, in which the position of the side edges 24 of the sheet material is determined. From the measured value determined a change in position for the drive 27 is determined, which is designated M 4. The drive shaft of the drive M 4 extends parallel to the running direction 22 of the sheet-like material 1. By means of this recorded in a second orientation 29 drive 27 is a correction of the position of the sheet material 1 parallel to its direction 22 compare Figure 7 (ie, a lateral orientation of sheet-shaped material).

Thereafter, the thus aligned in its angular position and its lateral position arcuate material 1 runs below a provided in a position 13.1 or 13.2 Anstellklappen- or Anstelllippenelemente on the conveyor belt 10 in the correctly aligned position in the downstream printing unit einzulaufen. The illustration according to FIG. 6 shows a possible embodiment variant of the rotational elements 25 located in the alignment unit 8 and located above the conveying plane 9. The rotation elements 25 are formed in a preferred embodiment as a segmented rollers having a designated by an interruption peripheral surface 33. The segment rollers 25 rotate in the direction of rotation 34, indicated by the arrow shown and describe approximately a ¾ circle with respect to their respective axis of rotation. Below the respective segment roller 25, a roller supporting the sheet material 1 is shown. This can be made in one piece or record on its periphery a coating. The rotary bodies serving as segment rollers 25 are shown in a rest position in the left part of FIG. 6, while in the right part of FIG. 6 they grasp a specimen with the peripheral surface 33 conveyed in the conveying direction 22 of the sheet material 1. As a result, it is transported in the conveying direction 22 of the sheet-like material 1 in accordance with the direction of rotation 34. FIG. 7 shows the correction of the angular position of the sheet-like material 1 during the passage of the aligning unit 8. The position of the sheet-like material 1 shown in FIG. 7 has just reached the last sensor of the light barrier 30.1, so that now the drive designated M 1 is reached 27 of the segment roller 25 can be activated to compensate for the angular position of the sheet material 1 with respect to the conveying direction 22. In contrast to the drives M 3 and M 4, which may be connected to each other via a continuous drive shaft 31, the segment rollers 25, which are in communication with the drives M 1 and M 2, are each driven by individual shafts 32. After correction of the angular position of the sheet-like material 1 by different fast feed rates to the respective drives 27 (M 1 or M 2) of the respective segment rollers 25, the sheet-shaped material 1 undergoes a correction of its lateral position. After measuring the position of the side edges 24 of the sheet material 1 by line-shaped CCD sensors 30, the sheet material 1 is now properly aligned laterally to the direction 22, in which via the drive M 4, a shift of the sheet material 1 in its conveying plane 9 before reaching the Anstellelementes 13 and before emergence on this downstream conveyor belt 10 takes place. With the drive 27 (M 3), oriented in the first orientation 28, the advance of the sheet material 1 with correctly aligned leading edge 23 is ensured via a common shaft 31, while this is aligned via the recorded in a second orientation 29 drive 27 (denoted by M 4) in a lateral position.

With the method proposed according to the invention, to use a CCD line sensor pair 30, it is possible to maintain that side edge 24 in the lateral alignment of the sheet material 1, which has already served to align the sheet material 1 in the first printing pass. If the already printed in the first printing pass sheet material 1 in the same printing units again, so its side edge 24 comes to turn around the central axis of the sheet material 1 on the other sensor of the line sensor pair 30 to lie, so that the alignment on the same side edge 24 takes place. If the same measuring point in the region of the leading edge of the side edges 24 is used in both alignment operations, then the registration for the positioning of top sides to bottom side pressure is independent of the paper tolerances.

When re-printing the sheet material 1, which has already been printed on one side, can be avoided in the orientation of paper tolerances Ausrichtebeimträchtigungen if it is ensured that the orientation of the sheet material 1 at its second pass through identical printing units at the same position of the Side edge 24, that is done in the front region of the side edge 24, which extends from the front edge 23 of the sheet-like material 1 from. If in the conveying plane 9 for the sheet-shaped material 1 CCD line sensors used as a pair of sensors 30, they may extend so far perpendicular to the conveying direction 22 of the sheet material 1 that all common printing material formats, be it for paper, for cardboard or films can be covered. This allows an increase in the flexibility of a different substrates processing printing machine, be it an electrographic, an electrophotographic or other digital printing press. The proposed method for aligning the sheet material 1 before running onto a conveyor belt 10 can of course also conventionally operable rotary printing presses, the sheet material 1, use. For this purpose, the line sensor pair 30 is to be arranged at the end of the feed table directly in the area of the side and Ziehmarken, which are preceded by a Vorgreifeinrichtung with which the aligned sheet material 1 is accelerated to machine speed and transferred to paper-leading cylinder.

LIST OF REFERENCE NUMBERS

1

arched material

2

print image

3

frame

4

Position error Y direction

5

Position error X direction

6

Verdrehfehler

7

Offset printing floor front and back (1)

8th

Registration unit

9

conveying plane

10

conveyor belt

11

up roller

12

control roller

13

setting direction

13.1

first position

13.2

second position

14

charging unit

15

electrode

16

support

17

Leading edge sensor

18

radiation source

19

lens

20

radiation field

21

radiation receiver

22

Conveying direction arcuate material

23

leading edge

24

side edge

25

segmented rollers

26

light barriers

27

Drives Segmented roller

28

first orientation drive

29

second orientation drive

30

Line sensor pair

30.1

photocell

31

continuous wave

32

Single shaft

33

Segment roller circumference

34

direction of rotation

35

Segmented roller active position

36

Segmented roller inactive position

Claims (6)

1. Method for the alignment of sheet material (1), said alignment being performed by means of rotating elements (25) and by means of a line sensor (30) integrated in a transport plane (9), and said sheet material (1) being turned over about its central axis in order to print said material's front and rear sides, with the lead edge (23) of said sheet material (1) remaining in its aligned position,
   characterized in that
   two line sensors (30) are provided, said sensors being arranged in such a manner that one of the line sensors (30) can detect the position of one lateral edge (24) of the sheet and the other line sensor (30) can detect the other lateral edge (24) of the sheet, in that the sheet material (1), after having been turned over about its central axis, is aligned along the same lateral edge (24) as during the alignment operation of the sheet material (1) prior to said material's being turned about its central axis in that the position of the lateral edge (24) of the sheet material (1) is determined by way of a sensor line of one of the line sensors (30), said sensor line being oriented perpendicular to the transport direction (22) of the sheet material (1), the linear extension of the sensor lines sweeping across a region perpendicular to the transport direction (22) of the sheet material (1), said region being highly likely to contain the respective lateral edge (24) of the sheet, and the lateral edge (24), after having been turned over about the central axis of the sheet material (1), coming to be located above the sensor line of the respectively other line sensor (30).
2. Method as in Claim 1, characterized in that
   the same measuring point is used at all times for the alignment of the sheet material (1) along the lateral edge (24).
3. Method as in Claim 1, characterized in that
   the sensor lines of the line sensors (30) are configured as CCD sensor lines.
4. Method as in Claim 1, characterized in that
   the alignment of the sheet material (1) occurs in the region of the lateral edges (24) adjacent to said material's lead edge (23).
5. Device for the alignment of sheet material (1), said device comprising rotating elements (25) performing the alignment and a line sensor (30) integrated in a transport plane (9), said sheet material (1) being turned over about its central axis in order to print said material's front and rear sides, with the lead edge (23) of the sheet material (1) remaining in its aligned position,
   characterized in that
   two line sensors (30) are provided, said sensors being arranged in such a manner that one of the line sensors (30) can detect the position of one lateral edge (24) of the sheet and the other line sensor (30) can detect the other lateral edge (24) of the sheet, in that the sheet material (1), after having been turned over about its central axis, is aligned along the same lateral edge (24) as during the alignment operation of the sheet material (1) prior to said material's being turned about its central axis in that the position of the lateral edge (24) of the sheet material (1) is determined by way of a sensor line of one of the line sensors (30), said sensor line being oriented perpendicular to the transport direction (22) of the sheet material (1), with the linear extension of the sensor lines sweeping across a region perpendicular to the transport direction (22) of the sheet material (1), said region being highly likely to contain the respective lateral edge (24) of the sheet, and the lateral edge (24), after having been turned over about the central axis of the sheet material (1), coming to be located above the sensor line of the respectively other line sensor (30).
6. Printing machine, in particular a digital printing machine, preferably an electrographic printer, comprising a feeder device for the alignment of sheet material (1), said device comprising rotating elements (25) performing the alignment and a line sensor (30) integrated in a transport plane (9), said sheet material (1) being turned over about its central axis in order to print said material's front and rear sides, with the lead edge (23) of the sheet material (1) remaining in its aligned position,
   characterized in that
   two line sensors (30) are provided, said sensors being arranged in such a manner that one of the line sensors (30) can detect the position of one lateral edge (24) of the sheet and the other line sensor (30) can detect the other lateral edge (24) of the sheet, in that the sheet material (1), after having been turned over about its central axis, is aligned along the same lateral edge (24) as during the alignment operation of the sheet material (1) prior to said material's being turned about its central axis in that the position of the lateral edge (24) of the sheet material (1) is determined by way of a sensor line of one of the line sensors (30), said sensor line being oriented perpendicular to the transport direction (22) of the sheet material (1), the linear extension of the sensor lines sweeping across a region perpendicular to the transport direction (22) of the sheet material (1), said region being highly likely to contain the respective lateral edge (24) of the sheet, and the lateral edge (24), after having been turned over about the central axis of the sheet material (1), coming to be located above the sensor line of the respectively other line sensor (30).

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