DE102008054814B4 - Device for detecting the position of a printing plate - Google Patents

Abstract

Device for detecting the position of a printing plate (4) on a cylinder (1) of a printing press with a position of the printing plate (4) in the axial and circumferential direction on the casing (27) of the cylinder (1) by means in the area of a printing plate front edge (12 ) provided registration marks (15, 16) register measuring system (11), wherein the register measuring system (11) additionally detects the position of a printing plate trailing edge (24) of the printing plate (4) on the cylinder (1), wherein, in the area of the printing plate trailing edge (24) a first rear registration mark (25) and a second rear registration mark (26) are provided, characterized in that the rear registration marks (25, 26) are designed to match the registration marks (15, 16) and are arranged in mirror image thereto and that in the register measuring system (11) or an assigned evaluation unit, the measured values determined by the register measuring system (11) and characterizing the position of the leading edge (12) of the printing plate are compared with the measured values determined by the register measuring system (11) and characterizing the position of the trailing edge (24) of the printing plate.

Description

The invention relates to a device for detecting the position of a printing plate on a cylinder of a printing press with a register measuring system that detects the position of the printing plate in the axial and circumferential direction on the jacket of the cylinder by means of registration marks provided in the area of a printing plate front edge.

To increase productivity in printing presses, it is common practice to work with automatic plate changing machines. The printing plates intended for printing are positioned in the automatic plate changing machines and after a printed printing plate has been removed, they are fed to the cylinder that carries the printing plate during the printing process. For clamping and tensioning the printing plates on the jacket of the cylinder, a clamping unit receiving and fixing the front edge of the printing plate and a clamping/clamping unit receiving and fixing the rear edge of the printing plate and subsequently clamping the printing plate are provided. Alignment pins arranged at a distance from one another and corresponding to alignment punchings provided in the front edge of the printing plate are assigned to the clamping unit. When feeding in a printing plate, the clamping unit and the clamping/clamping unit are open and the printing plate is positioned with the fitting punches on the fitting pins. After the printing plate has been clamped, the cylinder is rotated in the opposite direction to the printing direction and the trailing edge of the printing plate is brought to the clamping/clamping unit, with means being provided which bring the printing plate closer to the jacket of the cylinder and position the free trailing edge of the printing plate in the clamping/clamping unit. The clamping/tensioning unit is then closed and the pressure plate is clamped on the cylinder by moving it in the circumferential direction.

The disadvantage is that although the contact of the pressure plate with the fitting stampings on the fitting pins can be signaled, there is generally no provision for measuring the position of the rear edge in the clamping/clamping unit. This can result in the trailing edge of the printing plate not being fixed, which can lead to machine damage when the press is started up. It is also known to provide the clamping/clamping unit with sensors that detect the rear edge of the printing plate, which leads to increased costs and to a larger space requirement.

In printing presses, printing plates for the individual color separations are produced and clamped on cylinders of the printing press provided for this purpose in order to produce multicolored print images. During printing, the partial images are transferred one after the other from the printing plates to the material to be processed. The accuracy of the superimposed printing of the individual sub-images is decisive for the quality of the multicolor print applied to the material to be processed. In order to obtain a flawless multicolor print image, the individual printing plates must each be applied to the cylinders in an exactly specified target position, with the printing plates being positioned and fixed both in the axial direction and in the circumferential direction with an accuracy of about 10 μm.

These are, as in the DE 103 452 90 A1 described, assigned registration marks to each printing plate. The registration marks can be in the form of data codes which contain information about the dimensions, orientation, format and/or color of the printing plate, it also being possible to provide position marks in addition to these data codes. A register mark is assigned to each register punch, so that when the printing plate is applied to the cylinder, the register marks are positioned in the immediate vicinity of a register pin. A register measuring system is assigned to the register pins, which generally consists of two register measuring elements, each of which has a field of view in which a register pin and a register mark are located.

The register measuring elements or the register measuring system are arranged exactly at a fixed distance from the cylinder and thus from the printing plate provided on the jacket of the cylinder and in a fixed desired position relative to the cylinder. The calibrated register measuring elements/register measuring system and an evaluation unit assigned to them, if applicable, can be used to determine the position of the register marks and to identify the printing plate when the printing plate is in contact with the register pins. If the registration marks are in a specified target position, quality printing is possible. If the actual position of the registration marks deviates from the target position, the actual position is brought into the target position by an adjusting movement in the axial and/or circumferential direction, initiated by register adjusting units assigned to the cylinder. There is no provision for detecting the distance between the printing plate and the cylinder jacket or between the printing plate and the register measuring elements/register measuring system.

The DE 198 54 845 A1 describes a device for detecting the position of a printing plate on a cylinder of a printing press with a register measuring system that detects the position of the printing plate in the axial and circumferential direction on the shell of the cylinder by means of registration marks provided in the area of a printing plate leading edge, the register measuring system also measuring the position of a printing plate trailing edge of the printing plate captured on the cylinders.

The DE 102 58 851 A1 discloses a device for detecting the position of a printing plate on a cylinder of a printing press with a register measuring system detecting the position of the printing plate in the area of a leading edge of the printing plate, with a measuring system also detecting the position of a trailing edge of the printing plate on the cylinder.

The DE 10 2004 006 943 A1 teaches the use of two optoelectric measuring devices mounted on the printing unit so that they can be moved and locked, with one measuring device being assigned to one side of the plate cylinder and the measuring devices, which can be in the form of CCD area cameras, for example, are connected to a computer, while the computer is linked to register setting devices is. Each plate cylinder is assigned a register setting device, by which the plate cylinders can be adjusted in the circumferential, diagonal and axial directions, with registration marks on the printing plate representing the information relevant to the register setting.

The object of the invention is to expand the functionality of the generic device in such a way that it is possible to apply a printing plate to a cylinder in a register-correct and trouble-free manner.

According to the invention, the object is achieved by a device according to the features of claim 1.

With the solution according to the invention it is possible with a register measuring system, which determines the position of the front edge of the printing plate on dowel pins, to also control the position of the rear edge of the printing plate during an automatic or semi-automatic plate change.

• 1 eine an Passstiften anliegende Druckplatte in der Draufsicht,
• 2 die Druckplatte nach 1 in der Seitenansicht,
• 3 die Darstellung nach 2 mit der auf dem Zylinder aufgebrachten Druckplatte und
• 4 die Lage des Zylinders in einer Kontrollposition.

The invention is explained in more detail using an exemplary embodiment. In the drawings show:

• 1 a top view of a pressure plate resting on dowel pins,
• 2 the pressure plate 1 in the side view,
• 3 the representation 2 with the pressure plate applied to the cylinder and
• 4 the position of the cylinder in a control position.

In 1 a cylinder 1 with a pressure plate resting against a first dowel pin 2 and a second dowel pin 3 is shown in plan view. The cylinder 1 has a cylinder channel 5 in which is provided a plate attachment unit 6, of which a front clamping unit 7 and a rear clamping/clamping unit 8 are shown. A clamping strip 9 is shown from the front clamping unit 7 and a clamping drawer 10 from the rear clamping/clamping unit 8 . The clamping strip 9 of the front clamping unit 7 can be guided in a known manner against a counter bearing, not shown, or removed therefrom, whereby the pressure plate 4 is clamped or released, while the clamping/clamping drawer 10 of the rear clamping/clamping unit 8 also clamps against a counter bar, not shown, is guided or removed to release it. In addition, the rear clamping/clamping unit 8 can be displaced in the circumferential direction within the cylinder channel 5 in order to clamp the pressure plate 4 on a jacket 27 of the cylinder 1 .

In 1 It is also shown that a first pass hole 13 and a second pass hole 14 are assigned to a pressure plate front edge 12 of the pressure plate 4 . The pressure plate 4 rests with the first fitting hole 13 on the first fitting pin 2 and the second fitting hole 14 on the second fitting pin 3 . But it is z. It is also possible, for example, to provide only a first fitting hole 13 and to arrange the second fitting pin 3 in such a way that the pressure plate 4 bears directly on the second fitting pin 3 with the front edge 12 of the pressure plate. A first register mark 15 is applied to the pressure plate 4 in the immediate vicinity of the first register pin 2 , and a second register mark 16 is applied to the second register pin 3 . In the exemplary embodiment, the registration marks 15, 16 each consist of a data code 17 and two position marks 18. However, it is also possible to provide only one data code 17 and to integrate the position marks 18 in this. A reference position mark 19 is also assigned to each of the dowel pins 2, 3.

The first register mark 14 and the first register pin 2 are in the field of view of a first register measuring element 20 and the second register mark 15 and the second register pin 3 are in the field of view of a second register measuring element 21 when the pressure plate 4 with the register holes 13, 14 is in contact with the register pins 2, 3 , wherein the register measuring elements 20, 21 form a register measuring system 11 ( 1 and 2 ). The register measuring elements 20, 21 are positioned at a fixed distance X from the casing 27 or from the surface of the printing plate 4 to be applied to the cylinder 1, so that the registration marks 15, 16 are in the focus of the register measuring elements 20, 21, while the reference position marks 19 are usually serve to calibrate the measuring elements 20, 21 or the register measuring system 11.

When the pressure plate 4 is fed to the cylinder 1, it is applied with the fitting holes 13, 14 to the fitting pins 2, 3 and the front clamping unit 7 is closed by the clamping strip 9 being guided against the clamping bearing, not shown becomes. The pressure plate 4 is thus guided against the casing 27 in the area of the front edge 12 of the pressure plate, and the cylinder 1 is then rotated in the direction of the arrow 28 . The position marks 18/data codes 17 of the registration marks 15, 16 are detected by the register measuring elements 20, 21 and the actual position is compared with the desired position. If the actual position deviates from the desired position, control signals are generated and supplied to control units assigned to the cylinder 1 in order to implement control paths in the circumferential direction and/or in the axial direction. After the front clamping unit 7 has reached a plate guide unit 22 assigned to the cylinder 1, which is designed as a pressure roller 23 in the exemplary embodiment, it is activated and thus placed against the cylinder 1 so that the printing plate 4 is kept in operative connection with the jacket 27 until a Pressure plate trailing edge 24 reaches the open rear clamping/clamping unit 8. After closing and moving the rear clamping/clamping unit 8 in the circumferential direction, the pressure plate 4 is clamped on the cylinder 1 ( 3 ). The direction of rotation is then reversed and the area of the rear edge of the printing plate 24 is guided past the register measuring elements 20, 21, which are also activated by a control unit, and the distance to the surface of the printing plate 4 is recorded as an actual value and with the distance X stored as the target value compared ( 4 ). If the values match, the rear edge of the printing plate 24 has been correctly grasped, clamped and tensioned by the rear clamping/clamping unit 8 . This allows further process steps to be initiated. If the values do not match, this indicates that the rear edge of the printing plate 24 was not guided into the open rear clamping/clamping unit 8 and, after it was closed, e.g. B. rests on the clamping/clamping drawer 10 (dashed representation in 4 ). In this case, the plate change must be repeated. To detect the distance from the area of the rear edge of the printing plate 24 to the register measuring system 11, it is sufficient if a register measuring element 20, 21 is activated while the rear clamping/clamping unit 8 is being moved past after the movement of the cylinder 1 has reversed.

For reliable detection of the position of the area of the rear edge of the printing plate 24 when changing the plate, it is also possible, as in 1 shown to provide a first rear registration mark 25 and a second rear registration mark 26 in this area. The rear register marks 25, 26 can correspond to the register marks 15, 16 provided in the area of the front edge 12 of the printing plate and can be arranged as mirror images of these. With the rear registration marks 25, 26 it is possible to mark the surface of the printing plate 4 and thus to realize error-free detection by the register measuring elements 20, 21. It is also possible, however, if the rear registration marks 25, 26 correspond to the registration marks 15, 16 and are arranged as a mirror image of them, the measured values determined when scanning the registration systems 15, 16 and on which the adjustment actions required in the circumferential or axial direction are based with the values to compare, which are generated by the register measuring elements 20, 21 when the rear registration marks 25, 26 are detected. If these values match, the rear edge 24 of the printing plate has been gripped by the rear clamping/clamping unit 8 and the printing plate 4 has been placed on the cylinder 1 in the exact position. If the values do not match, the trailing edge of the printing plate 24 was not detected and the plate changing process must be repeated.

If rear registration marks 25, 26 are assigned to the printing plate rear edge 24, it is also conceivable, in order to be able to detect the position of the printing plate 4, to provide only one of the rear registration marks 25, 26 and to activate only one of the register measuring elements 20, 21.

Reference List

1

cylinder

2

First dowel pin

3

Second dowel pin

4

printing plate

5

cylinder channel

6

panel mounting unit

7

Front clamp unit

8th

Rear clamping/clamping unit

9

terminal strip

10

Clamping / clamping drawer

11

register measurement system

12

printing plate leading edge

13

First pass hole

14

Second pass hole

15

First registration mark

16

Second registration mark

17

data code

18

position mark

19

Reference position mark

20

First register gauge

21

Second register gauge

22

plate guiding unit

23

pressure roller

24

pressure plate trailing edge

25

First back registration mark

26

Second rear registration mark

27

Coat

28

arrow direction

X

Distance

Claims (6)

Device for detecting the position of a printing plate (4) on a cylinder (1) of a printing press with a position of the printing plate (4) in the axial and circumferential direction on the casing (27) of the cylinder (1) by means in the area of a printing plate front edge (12 ) provided registration marks (15, 16) register measuring system (11), wherein the register measuring system (11) additionally detects the position of a printing plate trailing edge (24) of the printing plate (4) on the cylinder (1), wherein, in the area of the printing plate trailing edge (24) a first rear registration mark (25) and a second rear registration mark (26) are provided, characterized in that the rear registration marks (25, 26) are designed to match the registration marks (15, 16) and are arranged in mirror image thereto and that in the register measuring system (11) or an assigned evaluation unit, the measured values determined by the register measuring system (11) and characterizing the position of the leading edge (12) of the printing plate are compared with the measured values determined by the register measuring system (11) and characterizing the position of the trailing edge (24) of the printing plate. device after claim 1 , characterized in that the register measuring system (11) detects the distance to the surface of the printing plate (4) in the area of the rear edge of the printing plate (24). device after claim 2 , characterized in that the register measuring system (11) consists of a first register measuring element (20) and a second register measuring element (21) and at least one register measuring element (20, 21) for detecting the distance in the area of the printing plate rear edge (24) can be activated. device after claim 2 , characterized in that in the region of the rear edge (24) of the printing plate there is a marking which supports the detection of the surface of the printing plate (4). device after claim 1 , characterized in that if the measured values match, the pressure plate (4) is clamped on the casing (27) of the cylinder (1). device after claim 3 , characterized in that at least one rear registration mark (25, 26) is provided in the area of the printing plate rear edge (24) and the register measuring element (20, 21) can be activated in whose field of view the rear registration mark (25, 26) arrives.

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