EP1170235B1 - Method for compensating dimension variations of a sheet material - Google Patents

Abstract

The invention relates to a process for compensation of dimension changes on sheet material (1) which is first provided with a printed image (36) on the front (35) and which is then provided with a printed image (40) on its back (39). The dimensions (41, 42) of the sheet material (1) are determined before an image is printed on the front (35) and before an image is printed on the back (39), and before an image is printed on the back (39) of the sheet material (1) the latter is centered to its position when the image was printed on the front (35).

Description

The invention relates to a method for compensating for dimensional changes to sheet material, in particular such dimensional changes to sheet material, which is printed in duplicate.

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 the orientation of a moving sheet in a variety of orthogonal directions, for example transversely to the transport path, in the direction of the transport path and for the removal of imbalances. The apparatus comprises a first roller assembly having a first pinch roller mounted to rotate about an axis which lies in a plane parallel to the plane of the transport path and which is substantially perpendicular to the direction of sheet transport along the transport path , A second roller assembly includes a second pinch roller supported to rotate about an axis which lies in a plane parallel to the plane of the transport path and which is substantially right-angled to the direction of sheet transport along the transport path. There is provided a third roller assembly having a third pinch roller mounted to rotate about an axis that is in a plane parallel to the plane of the transport path and substantially perpendicular to the direction of sheet transport along the transport path runs. A 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 controller is provided operatively associated with the first and second and third roller assemblies, respectively, and selectively controls the rotation of the first and second roller assemblies about the leading edge of a sheet moving in the sheet transport direction along the transport path in a direction perpendicular to the direction of sheet transport to arrange arranged situation. 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 Ausrichtegenaulgkeiten only to a limited extent. To achieve the required alignment accuracies, a substantial modification of the prior art blade alignment apparatus is required which does not appear economical.

In sheet-fed printing presses operating on the offset principle, the sheets are conveyed on the feed table in a shingled arrangement, before being aligned with side and draw marks provided in the feed table plane. After alignment of the sheet material is this passed in the aligned state to a pre-gripper, which accelerates the sheet-shaped material to the machine speed and passes to a Vorgreifereinrichtung downstream sheet-guiding cylinder. Other Ausrichtekentzepte usually use cylindrical rollers on the Rollenkem 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 fulcrum located on the stationary roll or during the feed located outside the lower speed reel or between the two reels.

When printed on the surface of a substrate according to the electrography principle or applied images, the substrate is heated after application of the toner to about 150 ° C, wherein the substrate is withdrawn so much water that it depends on the sheet thickness and the fiber layer of the print Substance, for example, the Paplerfasem shrink differently. For the Longitudinal and latitudinal extension of the substrate in the Bedruckstoffförderebene set different shrinkage factors, so that a different shrinkage of the sheet material occur transverse to the fiber direction, which may differ significantly from the shrinkage of the material in the longitudinal direction. If the shrinkage error in the sheet orientation in duplexing, ie not considered when printing the back of the sheet material, the error is the sum of the tolerances, which cause different layers of front and back side printed on both sides sheet material, which in particular to a Loss of quality contributes to translucent types of substrates.

From DE-A-3 611 965 a method of the type mentioned is also known, in the dimensional changes of a sheet by means of a Messvor direction before the imaging of a first page, d. H. the front, the bow and before the illustration of the second page, d. H. the back, the bow are detected. According to the dimensional changes of the sheet is aligned before printing the back center to the position of the sheet when imaging the front page.

The invention is based on the known from the prior art solution and the indicated technical problem of sheet shrinkage in double-sided printing of the substrate based on the task to compensate when re-printing an already printed substrate adjusting dimensional changes of the sheet material as far as possible and this aligned correctly position.

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

The advantages that can be achieved with the solution according to the invention are, above all, to be seen in the fact that by means of the alignment method proposed according to the invention when printing the back of an already printed on the front sheet material, the shrinkage error caused by a Drying unit, such as a Fuser be considered. By determining the absolute changes in the dimensions of the sheet material in its width or longitudinal extent, which may be different from each other, the shrinkage error modified, ie shrunken surface of the sheet material, as it passes through the sheet material processing machine, in the alignment of the now shrinked sheet material are taken into account, whereby the applied on the back of the sheet material printed image can be largely adapted to the position of the already located on the front of the sheet material printed image.

By means of the method proposed according to the invention, the absolute dimensional changes of the sheet material upon passage of a fixing unit, e.g. of a fuser, before imaging the back of the sheet material. The determination of the absolute dimensional changes of the sheet material for carrying out the imaging of the rear side of the sheet material allows the different shrinkage values depending on the direction of fiber travel in the sheet material to be in the longitudinal extent or in the width extent of the sheet material, while the orientation is reduced by the shrinkage errors to consider sheet material with reduced area.

Prior to imaging the backside of the sheet material, it is centered in its now increasing areal extent compared to the first pass through the sheet processing machine to the position that the sheet material had in the first pass through the sheet processing machine. In this aligned position, the front of the 8edruckstoffes has been imaged, whereas with the proposed method according to the invention, the shrinkage errors of the sheet material can be considered when applying the printed image on the back of the sheet material. The tolerances of the positions of the printed image on the front of the sheet material to the position of the printed image on the back of the sheet material can thus be minimized.

In a variant of the method proposed according to the invention, the absolute dimensional changes in longitudinal extent and width extension of the sheet material can be determined, whereby the position tolerances of the printed image on the back of the sheet material are minimized compared to the position of the printed image applied on the front side of the sheet material. With the method proposed according to the invention, the averaging of the absolute dimensional changes of the sheet material, i. From a corrected by the shrinkage error surface of the sheet material determine correction values for the position of the printed image on the back of the sheet material.

In this case, the corrected position of the printed image on the back side of the sheet-shaped material can be adapted to the surface of the sheet-like material modified by the absolute dimensional changes in an advantageous manner. Thus, the position of the applied on the back of the sheet-shaped material printed image is substantially congruent with located on the front of the sheet material imaged area, so that in translucent substrate, the printed images are printed substantially congruent to each other.

By the orientation of the sheet material before the second pass through the sheet material processing printing unit, also the edge regions of the printed image on the back surrounding non-printed area in width and longitudinal extent to the now changed, shrunk, i. in their length shorter and narrower their width surface of the substrate adapt.

Reference to a drawing, the invention is explained in more detail below.

Figur 1

eine sich einstellende Lageabweichung eines gedruckten Druckbildes relativ zur dieses aufnehmenden Bedruckstofffläche.

Figur 2

einen 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 Widerdruck aufgedruckten Druckbildes,

Figur 4

die Seitenansicht eines Bogeneinlaufbereiches einer bogenverarbeitenden Maschine in schematischer Wiedergabe.

Figur 5

die Draufsicht auf die Ausrichtekomporienten, die Sensorik sowie die Antriebe für das bogenförmige Material relativ zur Bogenlaufrichtung ausrichtender Rotationselemente,

Figur 6

die oberhalb der Förderebene des bogenförmigen Materials als Segmentrollen ausgebildeten Rotationselemente,

Figur 7

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

Figuren 8.1 und 8.2

den sich im Vergleich zum Druckbild auf der Vorderseite einstellenden Versatz der Druckbildlage auf der Rückseite, ohne Berücksichtigung der Schrumpfungseffekte und

Figuren 9.1 und 9.2

eine unter Berücksichtigung der Schrumpfungseffekte korrigierte Lage des Druckbildes auf der Rückseite eines bogenförmigen Materials.

It shows:

FIG. 1

a self-adjusting position deviation of a printed print image relative to this receiving substrate surface.

FIG. 2

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

FIG. 3

an offset, the printed on the underside and top of a sheet-shaped material in perfecting printed image,

FIG. 4

the side view of a Bogeneinlaufbereiches a sheet processing machine in a schematic representation.

FIG. 5

the top view of the Ausrichtekomporienten, the sensors and the drives for the sheet material relative to the sheet running direction aligning rotation elements,

FIG. 6

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

FIG. 7

the orientation of an arcuate material with the drives of the alignment causing segment roles and

Figures 8.1 and 8.2

the resulting in comparison to the printed image on the front offset of the printed image position on the back, without taking into account the shrinkage effects and

Figures 9.1 and 9.2

a corrected position of the printed image on the back of an arcuate material, taking into account the shrinkage effects.

From the illustration according to FIG. 1, an arcuate material oriented at right angles to its feed direction, 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. Marked within the printing surface 2 and the frame 3 deviations of .DELTA.x or .DELTA.y, the positional errors in the x and y directions 4 and 5 indicative, can be set when printing the print image 2 on the surface of the sheet material 1. The deviations denoted by reference numerals 4 and 5 are positional deviations, whereas in the illustration according to FIG. 2 angular deviations of the printed image 2 with respect to its position on the printed sheet 1 are shown.

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 sheet-like material 1, wherein this is conveyed in the conveying direction with its leading edge 23 ahead.

The illustration according to FIG. 3 shows a diagrammatic view of the reversal register, wherein with reference numeral 7, which can be characterized between the printed images 2 on the front and rear sides of the sheet-like material 1, in each case, setting offsets. These are designated in the illustration according to FIG. 3 by reference numeral 7 or by Δx and Δy. The reversible fuser plays in particular a role in translucent paper types and 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, an alignment unit 8 is connected 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 brought from a salaried position 13.1 in a parked position 13.2, which is shown here only schematically in solid lines or dashed lines. By means of the positioning flap or the setting lip, the sheet-like material 1 is pressed onto the surface of the conveyor belt 10 in the aligned state of the sheet-like material 1. After passage of the pressing element 13, the sheet-shaped material 1 received on the surface of the conveyor belt 10 passes through a loading unit 14 this charging unit 14, an electrode 15 is accommodated within a hood-shaped cover, which is for a static charge of the sheet material 1 and thus ensures its adhesion to the surface of the conveyor belt 10.

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 arranged below the conveying plane 9 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 meets an aperture arrangement which is provided above the conveying plane 9 of the sheet-like material 1. The diaphragm assembly is a receiver 21 downstream, which senses the presence of the leading edge 23 of the sheet material 1.

From the illustration according to FIG. 5, the alignment unit 8 can be seen in plan view, the components of which are reproduced here in a schematic representation. The alignment unit 8 is reached by an arcuate material 1, which is conveyed in the conveying direction 22. The leading edge 23 of the sheet material 1 is offset with respect to the running direction of the sheet material 1, whereby an oblique course of the side edges 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 conveying direction 22 overflows a first light barrier 26, the drives 27, designated M 1 and M 2, which drive rotational elements 25 via individual axes 32, are accelerated to feed speed. By triggering the drive 27 or M 1 or M 2 triggered via the light barrier 26, it is ensured that each copy of the sheet-like material 1 comes into contact with identical peripheral sections of the rotary elements 25, which can be designed, for example, as segmented rollers , Any self-adjusting differences in the feed motion, which could be due to dimensional and form 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 photoelectric barrier 26, the two rotary elements 25 are set in rotation, the arcuate material transported at feed speed via one of the first light barrier 26 downstream further sensor unit 30.1. As soon as the first of the two sensors of the sensor pair 30.1 has detected the leading edge 23 of the sheet material 1, a counter unit starts counting the motor steps. The counting process is then terminated and the difference recorded when the second sensor of the sensor pair 30.1 switches.

From the counter reading determined in this way, a correction value is determined which is used as an additional feed to the last started segment roller drive, i. either the drive 27, which is designated M 1, or the drive 27, which is designated M 2, is passed. As a result, the corresponding rotational body 25 designed as a segmented roller is moved at an increased feed rate until the predetermined path difference is completely compensated. At the end of this correction process, the front edge 23 is oriented exactly perpendicular to the sheet running direction 21.

After correction, the sheet-like material 1 in the conveying direction 22 is continuously passed from the first pair of segment rollers 25 to this downstream another pair of rotary body 25, which may be received on a common axis 31. Now driven via drive 27 or M 1 and M 2 segment roller pair 25 is turned off and moves to a rest position.

The now correctly aligned with respect to its angular position arcuate material 1 now runs on a sensor array 30 in which the position of the side edges 24 of the sheet material 1 is measured. From the measured value determined a change in position for the drive 27 is determined, which is designated M 4, the drive shaft extends parallel to the conveying direction 22. By means of this drive 27 received in a second orientation 29, the position of the sheet-like material 1 is corrected in parallel to its running direction 22 (see FIG.

Thereafter, the aligned in its angular position and its lateral position sheet 1 runs below a 13.1 or 13.2 provided in a position Anstellklappen or Anstelllippenelementes 13 on the conveyor belt 10 to run in the correct aligned position in the downstream pressure unit. From the illustration according to FIG. 6, a variant of the embodiment of the rotational elements 25 located in the alignment unit 8 and located above the conveying plane 9 emerges. The rotation elements 25 may be 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 34, indicated by the arrow shown, and describe approximately a ¾ circle with respect to its axis of rotation. Below the respective segment roller 25, a roller 34 supporting the sheet material 1 is shown.

The rotational elements 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 grip a copy of the sheet material 1 conveyed in the direction of travel 22 with their circumferential surface 33 and transport them in the direction of sheet travel 22 according to the direction of rotation , FIG. 7 shows the correction of the angular position of the sheet-like material 1 during the passage of the alignment unit 8. In the position of the sheet-like material 1 shown in FIG. 7, its leading edge 23 has just reached the last sensor of the sensor pair 30.1, so that now the one designated M 1 Drive 27 of the segment roller 25 can be activated to compensate for the angular position of the sheet material 1 with respect to the direction 22. It should be mentioned that in contrast to the drives M 3 and M 4, which are 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 material 1 by different fast actuations of the respective drives 27 (M 1 and M 2) of the segment rollers 25, the sheet-like material 1 undergoes a correction of its lateral position. After the measurement of the position of the side edges 30 of the sheet material 1 by the sensors 31, the sheet-shaped material 1 is now correct in now parallel to Direction of conveyance 22 aligned by a displacement of the sheet material 1 in its conveying plane before reaching the Anstellelementes 13 and before emergence onto the conveyor belt 10 via the drive M 4. With drive M 3, oriented in the first orientation 28, the feed of the sheet-like material 1 is ensured with a correctly aligned front edge 23 via a common shaft 31, while this on the recorded in a second orientation 29 drive 27, denoted M 4, in its lateral position is aligned.

FIGS. 8.1 and 8.2 show the imaging of an arched material 1 on the front and rear sides with printed image offsetting on the rear side.

Figure 8.1 shows the front side 35 of an arcuate material 1. On the front side 35 of the sheet material 1, a printed image 36 is applied, which at its edges with edge distances 37 in the x direction and an edge distance 38 in the y direction from the edges of the sheet material 1 is spaced.

In the illustration according to FIG. 8.2, the sheet-like material 1 according to FIG. 8.1 is seen from its rear side.

On the front side 35 is the printed image 36 on the rear side 39 of the sheet material 1 shown in Fig. 8.2 which is offset to this applied to the surface printed image 40. The planar extension of the sheet material 1 in the plane has in the illustration of FIG 8.2 is reduced by the absolute shrinkage 42 or 41 in the widthwise extension of the sheet material 1. The offset with which the printed image 40 is applied to the rear side 39 of the sheet-like material 1 is indicated by reference numerals 43 and 44, respectively. With translucent printing material, such as very thin substrate with low grammage, the offset shown in Fig. 8.2 of the print images 36 and 40, respectively Front side 35 and rear side 39 of the sheet-like material 1 of low quality.

The illustration according to FIG. 9.1 essentially corresponds to the illustration of the front side 35 of an arched material 1 according to the previously described FIG. 8.1.

From the illustration according to FIG. 9.2, the rear side 39 of the sheet-like material 1 protrudes, onto which a printed image 40 in a corrected position 45 is printed. The flat, sheet-like material 1 according to FIG. 9.2 has shrunk in its absolute dimension in the longitudinal direction by the amount 42 and in the width direction by an amount 41. The shrinkages in the longitudinal and transverse directions may well differ from one another, depending on the grain of the fibers when it is sheet material 1 made of paper. Prior to printing on the back side 38, the material 1 shrunk by the absolute amounts 41 and 42 in the transverse direction and in the longitudinal direction, respectively, is readjusted before it is printed on its rear side 39. The shrinkage errors are detected during alignment and then determined before the back side 39 of the sheet material 1 to be printed is fed again to the machine 1 which processes the sheet material 1. Prior to re-passing the sheet material 1 through the sheet processing machine, the orientation of the now shrunken sheet material 1 is approximately centered to the position that the sheet material prior to printing from its top 35 in the sheet-shaped machine in the sheet material 1 processing machine has taken. As a result, in relation to the corrected position of the printed image 45 at the edges of narrower edge regions 46 and 47, respectively. On the one hand, the marginal areas take into account the corrected printed image layer 45 on the back 39 of the sheet-like material 1 and are therefore necessarily adapted to the new dimensions in the longitudinal extent or width extension of the shrunken sheet-like material.

LIST OF REFERENCE NUMBERS

1

arched material

2

print image

3

frame

4

Positional error y-direction

5

Position error x-direction

6

Verdrehfehler

7

Offset front / back

8th

Registration unit

9

conveying plane

10

conveyor belt

11

up roller

12

control roller

13

Anstellelemenf

13.1 1.

position

13.2 2.

position

14

charging unit

15

electrode

16

support

17

Leading edge sensor

18

radiation source

19

lens

20

radiation field

21

receiver

22

direction

23

leading edge

24

side edge

25

segment role

26

photocell

27

Drives segment rollers

28 1.

Orientation drives

29 2.

Orientation drives

30

sensor field

30.1

sensor pair

31

common wave

32

Single shaft

33

Segment roller circumference

34

Counterpressure element

35

Front sheet material

36

Printed image front side

37

Edge distance x front side

38

Edge distance y front side

39

Back sheet material

40

Printed image on the back

41

Absolute shrinkage x-direction

42

Absolute shrinkage y-direction

43

Offset print image layer 39 x component

44

Offset pressure layer 39 y component

45

Corrected print image position

46

averaged edge x-direction averaged edge y-direction

Claims (4)

1. Method for the compensation of dimensional changes of sheet material (1), wherein:

   - initially, the absolute dimensional changes (41, 42) of the sheet material (1) are determined before providing the front side (35) with a printed image (36);

   - the front side (35) of the sheet material (1) is provided with the printed image (36);

   - before providing the rear side (39) with a printed image (40), the absolute dimensional changes (41, 42) of the sheet material are determined, said printing image being brought into centered registration relative to the position of the sheet material (1) at the time the front side (35) is provided with the image, the registration being achieved by means of a registration unit (8) located upstream of a rotating transport belt (10) before the registered sheet material (1) is placed on the transport belt (10), and the mean of the absolute dimensional changes (41, 42) on the sheet material (1) being used to determine corrective values (43, 44) for the position (45) of the printed image (40) on the rear side (39) of the sheet material (1); and,

   - thereafter, the rear side (39) of the sheet material (1) is provided with the printed image (40).
2. Method as in Claim 1, characterized in that the mean is determined based on the absolute dimensional changes (41, 42) along the length and along the width of the sheet material (1).
3. Method as in Claim 3, characterized in that the corrected position (45) of the printed image (40) on the rear side (39) of the sheet material (1) is adapted to the area of the sheet material (1), said area having been modified by the absolute dimensional changes (41, 42).
4. Method as in Claim 3, characterized in that edge areas (46, 47) resulting from the corrected position (45) of the printed image (40) on the rear side (39) of the sheet material (1) are adapted to the resultant area of the sheet material (1).

Images