EP4035899A1

EP4035899A1 - Calibration unit for a rotary printing press

Info

Publication number: EP4035899A1
Application number: EP21153648.7A
Authority: EP
Inventors: Gordon Whitelaw; Wolfgang Brusdeilins; Thomas Haecker
Original assignee: Allstein GmbH
Current assignee: Allstein GmbH
Priority date: 2021-01-27
Filing date: 2021-01-27
Publication date: 2022-08-03

Abstract

A calibration unit (24) for a rotary printing press having a central impression cylinder (10) and a number of colour decks (12a - 12h) disposed around the periphery of the central impression cylinder, each colour deck comprising a rotatable printing cylinder (14; 14') which carries a position mark (22) and is adapted to be set against the periphery of the central impression cylinder, the arrangement of the colour decks being symmetric with respect to at least one axis of symmetry (V, H), the calibration unit (24) having a number of sensor arms (30a-30h) each carrying a sensor (32) for detecting the position mark (22) of one of the printing cylinders, the calibration unit being adapted to be mounted on a frame (20) of the printing press such that the sensor arms project radially from the axis of rotation of the central impression cylinder (10) and are pivotable about that axis independently of the central impression cylinder, characterized in that at least two of the sensor arms (30a-30h; 30b, 30c) are interconnected by a drive mechanism (34; 36) configured for controlling a symmetric pivotal movement of the sensor arms (30d, 30e; 30b, 30c) with respect to a reference axis which, when the unit is mounted to the frame (20) is aligned with said axis of symmetry (V; H).

Description

The invention relates to a calibration unit for a rotary printing press having a central impression cylinder and a number of colour decks disposed around the periphery of the central impression cylinder, each colour deck comprising a rotatable printing cylinder which carries a position mark and is adapted to be set against the periphery of the central impression cylinder, the arrangement of the colour decks being symmetric with respect to at least one axis of symmetry, the calibration unit having a number of sensor arms each carrying a sensor for detecting the position mark of one of the printing cylinders, the calibration unit being adapted to be mounted on a frame of the printing press such that the sensor arms project radially from the axis of rotation of the central impression cylinder and are pivotable about that axis independently of the central impression cylinder.
A rotary printing press having a calibration unit of this type has been disclosed in DE 10 2014 215 648 A1 .
The calibration unit is used for adjusting the longitudinal register and side register of each printing cylinder by aligning the position mark with the sensor on the sensor arm. For example, the position mark may be formed by a magnet, and the sensor is a magnetic field sensor outputting an electronic signal that indicates an offset of the magnet relative to the sensor. During the process of a setting the longitudinal and side register, the sensor arm must be held in a position in which the radial direction of the sensor arm coincides with the radial direction from the axis of rotation of the CI (central impression cylinder) and the point of contact between the periphery of the CI and the periphery of the printing cylinder.
In a typical printing press, the printing cylinder in each colour deck is guided for linear motion relative to the CI, so that it can be set against the CI and lifted off from the periphery of the CI. In a typical printing press of this type, the direction of the linear motion of the printing cylinder of at least some of the colour decks forms an angle with the radial direction of the CI. This has the consequence that the point of contact between the printing cylinder and the CI is dependent upon the diameter of the printing cylinder and, accordingly, shifts when the printing cylinder is replaced by a printing cylinder with a different diameter so as to print images with a different repeat. Consequently, the angular position of the sensor arm must be changed in accordance with changes of the diameter of the printing cylinders.
In the known printing press, the arrangement of the colour decks relative to the CI has a 180° symmetry, so that pairs of printing cylinders are disposed diametrically opposite to one another. The calibration unit has two sensor arms that are rigidly connected to one another and extend in opposite directions from the axis of rotation of the CI, so that the register of the two opposite printing cylinders can be adjusted simultaneously. When the register of another pair of printing cylinders is to be adjusted, the sensor arms are rotated into a position in which the sensors are aligned with the points of contact of these printing cylinders.
It is an object of the invention to provide a calibration unit that is suitable for a more efficient register adjustment process.
In order to achieve this object, in the calibration unit according to the invention, at least two of the sensor arms are interconnected by a drive mechanism configured for controlling a symmetric pivotal movement of the sensor arms with respect to a reference axis which, when the unit is mounted to the frame, is aligned with said axis of symmetry.
In this design, only a single drive mechanism is needed for simultaneously moving two sensor arms which form an angle of less than 180° with one another to their respective target positions. Thus, the calibration unit is suitable for simultaneous register adjustment of two printing cylinders that are not diametrically opposite to one another, and it has the further advantage that the two sensor arms can be moved into the required positions simultaneously. The invention takes advantage of the fact that, in a typical printing press, the arrangement of the colour decks is also mirror-symmetric with respect to at least one axis of symmetry. Consequently, whatever the diameter of the printing cylinders may be, the points of contact of these two printing cylinders will be mirror-symmetric, so that the sensor arms can be adjusted to these positions by a symmetric pivotal movement.
More specific optional features of the invention are indicated in the dependent claims.
The drive mechanism configured for controlling the symmetric pivotal movement of the sensor arms may be constituted for example by a rack-and-pinion drive with two parallel racks meshing with the pinion such that they move in opposite directions when the pinion is rotated. In another embodiment, the drive mechanism comprises two links connected to one another and to each of the two sensor arms by articulated joints, and a linear drive arranged for linear displacement of the joint that interconnects the two links.
As in the known calibration unit, pairs of sensor arms that extend in opposite directions from the axis of the CI may be rigidly connected to one another, so that as many as four sensors can be moved into their target positions in a single operation and with only a single drive mechanism.
More generally, if a printing press has a number 2n of colour decks with n being even, only n/2 drive mechanisms are needed for positioning the sensor arms for all colour decks. If the arrangement of the colour decks relative to the CI has more than one axis of symmetry, the drive mechanisms may have different reference axes. For example, the reference axis of one drive mechanism may be horizontal and the reference axis of another drive mechanism may be vertical.
If a printing press has 2n of colour decks with n being odd, it is common practise to arrange the colour decks such that there are two diametrically opposite colour decks in which the direction of linear movement of the printing cylinders is a radial direction of the CI, so that the points of contact are independent from the diameter of the printing cylinders. In this case, the calibration unit may comprise a pair of sensors that are rigidly mounted to the frame for aligning the position marks of the printing cylinders of these two colour decks. The sensor arms for the remaining 2n-2 colour decks may then be arranged in the same manner as described above.
Embodiment examples will now be described in conjunction with the drawings, wherein:

Fig. 1: is a schematic side view of essential parts of a printing press having a calibration unit according to the invention;
Figs. 2 and 3: show the calibration unit in two different positions;
Fig. 4: is a sectional view taken along the line IV-IV in Fig. 2; and
Fig. 5: is a schematic side view of a calibration unit according to an-other embodiment.

Fig. 1 schematically shows essential parts of a rotary printing press, e.g. a flexographic printing press, comprising a central impression cylinder (CI) 10 and eight colour decks 12a - 12h symmetrically disposed around the periphery of the CI. Each colour deck comprises a printing cylinder 14 and an inking cylinder 16 (anilox roller). In this specification, the term "printing cylinder" is to designate not only a one-piece printing cylinder but also a coaxial arrangement of one or more sleeves on a mandrel. The peripheral surface of the printing cylinder 14, which carries a printing form, engages the peripheral surface of the CI 10 at a point of contact P.
The printing cylinder 14 and the inking roller 16 of each colour deck are guided for linear movement relative to the CI 10 in a direction (horizontal in this example) that forms an angle with the radius from the central axis of the CI to the point of contact P. As a consequence, if the printing cylinders 14 are replaced by printing cylinders 14' that have a different diameter, then the point of contact P shifts in circumferential direction of the CI, and this amount of shift is different for different colour decks. For example, in case of the colour deck 12a, the amount of shift is larger than in case of the colour deck 12b, and in case of the colour decks 12c and 12d the point of contact shifts in opposite direction.
In the example shown, the arrangement of the colour decks 12a-12h around the periphery of a CI 10 is symmetric with respect to a vertical axis of symmetry V and with respect to a horizontal axis of symmetry H. As a consequence, the positions of the points of contact P are also symmetric under a 180° rotation about the central axis of the CI 10.
The CI 10 has a shaft 18 that has been shown in cross-section in Fig. 1 and is supported with its opposite ends in side frames 20 of the printing press. These side frames have not been shown in Fig. 1, but one of them is visible in a sectional view in Fig. 4.
As is well known in the art, the printing cylinders 14 of the various colour decks 12a-12h serve for printing superposed images in different colours onto a web that is trained around the periphery of the CI 10. In order for these images to be perfectly aligned with one another, the rotary position of each printing cylinder 14 (longitudinal register) and the axial position (side register) of each printing cylinder have to be properly adjusted. For that purpose, a position mark 22 (see colour deck 12d in Fig. 1) is embedded in the printing cylinder in an end portion that projects beyond the end of the CI 10, and a calibration unit 24 is provided for detecting the positions of the position marks 22 of all printing cylinders.
As is shown in Fig. 1, the calibration unit 24 has a star-shaped configuration with four bar-shaped sub-units 26 that are rotatably supported on the shaft 18 via nested hubs 28. Each sub-unit 26 constitutes two sensor arms 30a, 30e; 30b, 30f; 30c, 30g and 30d; 30h, respectively, that project radially from the hubs 28 in opposite directions. Each sensor arm carries at its free end a sensor 32 for detecting the magnetic field of the position mark 22 of the printing cylinder of an associated colour deck. Each sensor 32 points towards the point of contact of the associated printing cylinder and is configured to output an electronic signal indicating the axial and circumferential deviation of the position mark 22 from the position of the sensor 32. Thus, the position mark 22 can be aligned with the sensor 32 by rotating the printing cylinder about it axis and shifting it in axial direction in a process of adjusting the longitudinal register and the side register of the printing cylinder. Since a separate sensor arm 30a-30h is associated with each of the colour decks 12a-12h, the adjustment operations can be performed simultaneously for all colour decks, which has the advantage that the time needed for preparing the printing press for a new print run is greatly reduced, in particular, if the adjustment process is automated.
If the printing cylinders are exchanged by cylinders with a different diameter, the angular positions of the sub units 26 have to be shifted in accordance with the shift of the points of contact P.
In view of the symmetry with respect to the vertical axis V, the sub units having the sensor arms 30a, 30e and 30d, 30h, respectively, have to be shifted symmetrically, i.e. by the same amount but in opposite directions. This shift is achieved by means of a drive mechanism 34 the function of which will be described below with reference to Figs. 2 and 3. Similarly, in view of the symmetry with respect to the horizontal axis H, another drive mechanism 36 is provided for inducing a symmetric shift of the sub-units that comprise the sensor arms 30b, 30f and 30c, 30g, respectively.
Fig. 2 shows the calibration unit 24 in the same condition as in Fig. 1, with the sub-units aligned with the points of contact P of the printing cylinders 14.
Fig. 3 shows the calibration unit in a state adapted for the printing cylinders 14' having a smaller diameter. The points of contact have shifted to positions P', and the sub-units of the calibration unit 24 have been shifted accordingly.
In order to effect the shift of the sensor arms 30a, 30e, 30d, 30h, the drive mechanism 34 comprises two links 38 connected etween the sensor arms 30d and 30e via articulated joints. The joint that interconnects the two links 38 is driven for linear movement in radial direction of the CI by a linear drive having a stationary part 40 and a movable part 42. The stationary part 40 has a reference axis that defines the direction of movement of the moveable part 42, and it is attached to the frame 22 of the printing press (Fig. 4) in a position in which the reference axis is aligned with the vertical axis of symmetry V. For example, the movable part 42 may comprise a spindle, and the stationary part 40 may comprise a nut that is in engagement with the spindle and is driven for rotation by a motor. When, in the situation shown in Fig. 3, the movable part 42 is withdrawn in a downward movement, the links 38 push the sensor arms 30d and 30e apart symmetrically, so that the angle between these sensor arms becomes larger. Since the sensor arm 30d is rigidly connected to the sensor arm 30h and the sensor arm 30e is rigidly connected to the sensor arm 30a, the angle between the sensor arms 30a and 30h is increased by the same amount. In this way, the angular positions of the sub-units 26 can be adjusted to the respectively desired positions with high accuracy. When the diameter of the printing cylinders 14, 14' is known, the positions of the points P, P' of contact and, accordingly, the target positions of the sub-units 26 can be calculated and the sub-units can be adjusted to these positions with high accuracy.
The drive mechanism 36 for the sensor arms 30b, 30c, 30f and 30g has the same design as the drive mechanism 34, with the only difference that the stationary part 40 is aligned with the horizontal axis of symmetry H.
Fig. 4 is a view of an end portion of the CI 10 and a portion of the shaft 18 supported in the side frame 20 of the printing press on the drive-side, i.e. the side where a drive motor (not shown) is arranged for driving the shaft 18. The calibration unit 24 is accommodated in a narrow space between the side frame 20 and the end of the CI. The sub-units 26 on the nested hubs 28 are offset from one another in axial direction of the CI, but the sensor arms are configured such that all sensors 32 are aligned in a common plane. The sensor arms 30a and 30e are shown in a side view in Fig. 4, whereas the sensor arms 30h, 30g and 30f are shown in slanting views. The other sensor arms 30b, 30c and 30d are shown in sectional views. Also shown in sectional views are the movable part 42 and the links 38 of the drive mechanism that drives the sensor arms 30d and 30e. A part of the link 38 that connects the movable part 42 to the sensor arm 30e is also shown in a slanting view.
Near its free end and on the side facing the side frame 20, each sensor arm has a locking member 44 that can cooperate with a locking device 46 on the side of the frame 20 for tightly locking the sensor arm to the frame without altering the angular position of the sensor arm. This assures that the sensors 32 can be held stably in position during the register adjustment process.
Thus, the process of adjusting the longitudinal register and side register of all printing cylinders may be performed as follows. When a new set of printing cylinders is to be inserted into the colour decks, the angular positions of the sensor arms 30a-30h are calculated and adjusted on the basis of the known diameter of the printing cylinders. Then, the locking mechanisms 46 are actuated to firmly lock or clamp the sensor arms to the side frame 20 in the correct angular positions. Once the printing cylinders have been inserted, they are moved linearly against the CI until they engage the CI at their respective point of contact P. Then, the printing cylinders are withdrawn by a small amount, just enough to avoid friction between the printing cylinders and the CI, so that the printing cylinders can be rotated freely. Then, the longitudinal register and the side register of the printing cylinders are adjusted by rotating the printing cylinders about their respective axis and moving them in axial direction until the position mark 22 of each printing cylinder is perfectly aligned with the corresponding sensor 32. These processes can be performed in parallel for all printing cylinders, so that the printing press will be ready for starting a print run within short time.
When the printing press has to be prepared for a print run with a different repeat, the locking mechanisms 46 will be released and the sensor arms will be adjusted to the new points of contact.
Fig. 5 shows an example of a calibration unit 24' for a ten-colour printing press, i.e. a printing press wherein the number of colour decks divided by two is an odd number (5).
Consequently, compared to Fig. 1, the printing press has two extra colour decks with printing cylinders 48. these printing cylinders are arranged in the horizontal plane of symmetry H, so that the direction of linear movement relative to the CI 10 is a radial direction of the CI, which has the consequence that the position of the point of contact does not depend upon the diameter of the printing cylinders 48. Consequently, sensors 52 for detecting the position marks of these printing cylinders may be stationary relative to the machine frame. In the example shown, these sensors 52 are mounted on another sub-unit having sensor arms 30i, 30j that project from the shaft 18 but are not rotatable about this shaft relative to the frame 20. As an alternative, the sensors 52 might also be mounted directly on suitable brackets on the frame 20. The other four sub-units 26 of the calibration unit form two pairs, and each of these pairs has a drive mechanism 34 and 36, respectively, for symmetrically shifting these two pairs.

Claims

A calibration unit (24; 24') for a rotary printing press having a central impression cylinder (10) and a number of colour decks (12a - 12h) disposed around the periphery of the central impression cylinder, each colour deck comprising a rotatable printing cylinder (14; 14') which carries a position mark (22) and is adapted to be set against the periphery of the central impression cylinder, the arrangement of the colour decks being symmetric with respect to at least one axis of symmetry (V, H), the calibration unit (24; 24') having a number of sensor arms (30a-30h) each carrying a sensor (32) for detecting the position mark (22) of one of the printing cylinders, the calibration unit being adapted to be mounted on a frame (20) of the printing press such that the sensor arms project radially from the axis of rotation of the central impression cylinder (10) and are pivotable about that axis independently of the central impression cylinder, characterized in that at least two of the sensor arms (30a-30h; 30b, 30c) are interconnected by a drive mechanism (34; 36) configured for controlling a symmetric pivotal movement of the sensor arms (30d, 30e; 30b, 30c) with respect to a reference axis which, when the unit is mounted to the frame (20) is aligned with said axis of symmetry (V; H).
The calibration unit according to claim 1, comprising a number of sub-units (26) each of which has two sensor arms (30a, 30e; 30b, 30f; 30c, 30g; 30d, 30g) that are rigidly connected to one another and project from the axis of rotation in opposite directions.
The calibration unit according to claim 1 or 2, wherein at least one (34) of the drive mechanisms for said at least two sensor arms has a reference axis that, when the unit is mounted to the frame (20), is a vertical axis of symmetry (V).
The calibration unit according to any of the preceding claims, wherein at least one (36) of the drive mechanisms for said at least two pairs of sensor arms has a reference axis that, when the unit is mounted to the frame (20), is a horizontal axis of symmetry (H).
The calibration unit according to any of the preceding claims, comprising at least two drive mechanisms (34, 36).
The calibration unit according to claim 5, wherein said at least two drive mechanisms (34, 36) have different reference axes.
The calibration unit according to any of the preceding claims, wherein the drive mechanism (34, 36) comprises a linear drive arranged for linear radial displacement of a movable part (42) that is connected to the two sensor arms (30d, 30e; 30b, 30c) via articulated links (38).
The calibration unit (24') unit according to any of the preceding claims, comprising at least two sensors (52) that, when the unit is mounted to the frame (20), are stationary relative to said frame.
A rotary printing press having a calibration unit (24; 24') according to any of the preceding claims.
A rotary printing press having a calibration unit (24') according to claim 8 and having a number 2n of colour decks, wherein n is an odd number.