EP3251853B1

EP3251853B1 - Method for adjusting the position of form cylinders in a rotary printing machine

Info

Publication number: EP3251853B1
Application number: EP17000882.5A
Authority: EP
Inventors: Ivan Hejl; Lukas Skalicky
Original assignee: SOMA spol s ro
Current assignee: SOMA spol s ro
Priority date: 2016-05-31
Filing date: 2017-05-25
Publication date: 2019-01-02
Anticipated expiration: 2037-05-25
Also published as: EP3251853A1; ES2711766T3; CZ307067B6; CZ2016319A3

Description

Field of Invention

The invention relates to a method for adjusting the position of form cylinders in a rotary printing machine and the rotary printing machine using the technology of replaceable printing sleeves on the cylinders used for printing (form and raster cylinders), wherein the rotary printing machine comprises a movable arm provided with a position sensor.

Background of the Invention

Rotary printing machines are used for printing various materials, for example, paper, foil, laminates, with colors based on, for example, alcohol, water and UV.
In all rotary printing machines, great emphasis is put on the accuracy of adjusting the form and raster cylinders in relation to each other and to a central impression cylinder. In case of inaccurate adjustment, the printing output is of low quality, which is undesirable.
In present, there are known rotary printing machines with a so called "start-up" phase providing an accurate mutual adjustment of the cylinders, which is performed by means of adjusting a form cylinder and a raster cylinder to their optimal position during the printing process by moving the bearing blocks using suitably controlled servo motors. This method is highly time-demanding, with respect to the requirements on print quality, and at the same time it is highly ineffective due to production of large amount of waste.
Further, there is a known system in which the sensor head is fixed on a static arm, which protrudes from a frame element of the printing machine, wherein the sensor head faces a signaling device arranged on a circumferential surface of a replaceable cylinder. A drawback of such arrangement lies in a necessity to use great number of sensor heads provided on all replaceable cylinders.
Previously, in case of a change of order, whole cylinders had to be replaced in rotary printing machines, these cylinders being referred to as replaceable cylinders, wherein this term also included the form cylinder and raster (anilox) cylinder. In present, only print sleeves (cylinder sleeves) need to be changed, while the cylinders themselves remain in the machine. However, the central impression cylinder has not been and is not typically changed, being constructed to last the entire service life of a machine.
In another known arrangement, described for example in patent no. EP2227396 B1 , the sensor head is arranged on a movable element, which is provided as an integral part of a bearing for replaceable cylinder, which represents a form as well as a raster cylinder, excluding the central impression cylinder. This sensor head faces a signaling device arranged directly on the same replaceable cylinder. However, such arrangement is not advantageous due to lower accuracy of setting in relation to a central impression cylinder and due to necessity to use great number of sensor heads on all form cylinders and raster cylinders.
The patent EP2611614 B1 discloses a system, in which a reference number on a form cylinder is detected by a sensor installed on the surface of a central impression cylinder. A drawback of such system is a difficult installation of the sensor to the central impression cylinder, issues with eventual sensor repairs as well as with the data transfer from the sensor to a control unit during continuous rotation of the central impression cylinder.
The published German patent application no. DE102014215648 A1 discloses a rotary printing machine with a central impression cylinder rotating around the rotation axis and comprising at least one, preferably more, printing units arranged around the central impression cylinder, where each printing unit comprises a form cylinder with a reference number, and further on a separate rotary device a sensor for detection of reference number is provided, which is by means of a rotating device rotatable along a circular path around the same rotation axis as the central impression cylinder. This rotation device rotates independently of the movement of a central impression cylinder with a separate bearing housing and its angle of rotation is limited to an angle smaller than 360° or 180°. The rotating device may comprise one or more arms, separate electric drive, actuators, positioners for adjusting each printing unit to the correct angle position for detection of a reference sign, locking mechanism of the rotating device for attachment to a frame of a printing unit by means of which the rotating device may be locked in each position just for a period required for setting the position of each inking unit, in order to provide accurate adjustment and measurement, wherein there are as many locking mechanisms as the number of printing units in the printing machine. Adjustment of the form cylinders and detection of reference signs, preferably magnetic, is then performed independently of rotation of the central impression cylinder and the form cylinders which are not currently being used may be adjusted during printing. This solution requires its own drive and an accurate sensor of the position of a movable arm, which increases difficulty and thus probability of a defect, as well as acquisition and operating costs of a rotary printing machine. Moreover, this solution requires presence of a plurality of clamping mechanisms for particular frames of printing units.

Summary of the Invention

The above described drawbacks are eliminated by a method for adjusting the position of form cylinder in a rotary printing machine according to claim 1 of the present invention. Further preferred embodiments are defined in claims 2 and 3.
The method for adjusting the position of form cylinders in a rotary printing machine is characterized in that a central impression cylinder rotates to rest position of a movable arm with a sensor, the movable arm clamps to the central impression cylinder, and subsequently, together with the central impression cylinder driven by a drive of the central impression cylinder, the movable arm rotates gradually to each form cylinder, wherein for adjusting the position of a form cylinder the movable arm together with the central impression cylinder stops so that the sensor gets to a plane connecting the central impression cylinder axis and the form cylinder axis in the adjustment position, then the form cylinder shifts to the adjustment position and rotates so that the reference sign provided on a print sleeve of the form cylinder aligns with the sensor axis, and after adjusting the last form cylinder, the movable arm together with the impression cylinder rotate back to the rest position of the movable arm and subsequently the movable arm unclamps from the central impression cylinder. The adjustment position of form cylinders is determined by distance of the reference sign (magnet) from the sensor, which has to be identical for all form cylinders. Shift of the form cylinders to the adjustment position thus means shifting the form cylinders as close to the central impression cylinder as possible at a predetermined distance, however, so as the printing sleeve provided with the reference sign would not come into contact with the sensor or surface of the central impression cylinder. In order to maintain the accuracy as high as possible, the distance on the mounting stand should preferably be the same as between the reference sign (magnet) and the sensor. The rest position is a position in which the movable arm with the sensor rests when the adjustment of the form cylinders is not performed. This rest position may theoretically be chosen optionally, however, in practice it is preferably chosen so that the movable arm would not interfere during the other operational phases of the rotary printing machine and so that the sensor would be highly protected, e.g. from being stained by ink or solvent, or mechanical damage, during operation of the rotary printing machine, i.e. outside the phases of adjusting the form cylinders before printing.
Movement of the movable arm in a particular cycle with the central impression cylinder ensures higher accuracy of adjustment than the movable arm with its own drive would provide. Arrangement of the sensor on a separate movable arm is more advantageous than the arrangement on a central impression cylinder, due to the possibility of utilizing a wire data transfer (not only wireless) as well as due to easier repair or replacement in case of a sensor defect. Another advantage is that providing security against explosion during printing using solvent based inks is easier than in case of a device with a wireless data transfer or a device not utilizing data transfer via rotary cable feed. It is not necessary anymore, due to risk of explosion, to detach the sensor of the central impression cylinder before printing and install it again before adjusting the positions of form cylinders very precisely, which had been very difficult and time-demanding operation. Higher speed of adjusting the positions of form cylinders as well as adjusting the positions of form cylinders without the necessity to print significantly reduces the print costs and increases the print effectivity thanks to minimum amount of produced waste. Higher accuracy of positioning the cylinders increases the print quality, independently of the skills for operating the machine. Besides higher accuracy of adjustment, another advantage is the simplicity of the system in comparison to the solution described in the document DE10201421 5648 A1 , a separate drive of the movable arm is not necessary (the arm is positioned/rotated by the central impression cylinder), also an accurate sensor of the movable arm position is not necessary (the central impression cylinder is provided with its own position sensor) and only one clamping means is required (for clamping the movable arm to the central cylinder).
In a preferred embodiment of the adjustment of positions of form cylinders in a rotary printing machine is the central impression cylinder rotated to rest position of the movable arm, wherein the movable arm, after or simultaneously with being clamped to the central impression cylinder, unclamps from a frame of said rotary printing machine, and before or simultaneously with being unclamped from the central impression cylinder it clamps back to the frame of said rotary printing machine. Advantage of clamping the movable arm in a rest position means that clamping of the movable arm to the central impression cylinder in this position is performed safely.
The method of the present invention in a preferred embodiment allows simultaneous adjustment of two or more form cylinders, wherein at least one movable arm with the central impression cylinder stops so that two or more sensors arranged on at least one movable arm get to the plane connecting the axis of the central impression cylinder with the axis of the respective form cylinder, and reference signs of the form cylinders, which are being adjusted, would get to the axis of the respective sensor.

Description of Figures

Fig. 1 illustrates the arrangement of printing units around the central impression cylinder with the movable arm in the rest position of the movable arm.
Fig. 2 illustrates the position of the movable arm, sensor and reference sign on the connecting plane of the form cylinder axis and the central impression cylinder axis for one of the printing units.
Fig. 3 illustrates a cross-section through the arrangement of the central impression cylinder with the movable arm and the form cylinder.

Examples of Exemplary Embodiments

The rotary printing machine (see fig. 1) in one of the possible embodiments comprises at least two printing units, wherein each of the units (see fig. 2) further comprises a form cylinder 2, a raster cylinder 3 and an ink container 12, for example doctor blade chamber with a wiper, wherein the particular printing units are arranged around the central impression cylinder 1 integrated in the frame of the rotary printing machine. Further, on a pivot 8 of the central impression cylinder (see fig. 3), a movable arm 4 with a sensor 5 for detection of the position of the reference sign 9 on a print sleeve of the form cylinder 2 is rotatably arranged, wherein the movable arm 4, after being clamped to the central impression cylinder 1 via clamping means 6, is moving together with the central impression cylinder 1 by means of drive of the central impression cylinder 1, thus the movable arm 4 does not have its own drive.
The number of printing units arranged around the central impression cylinder 1 is limited exclusively by the diameter of the central impression cylinder 1 and the size of the rotary printing machine, the number does not typically exceed 12 printing units, wherein this number is not limited, i.e. it may be higher. The number of used printing units for a specific printing action is primarily determined by the number of colors required for printing, and further, the full and raster areas are separated due to technologic reasons (they require various pressure forces when printing). The cylinders of printing units which are not currently being used may remain fitted with the replaceable print sleeves, however, the operating person usually removes them from the rotary printing machine so that they could be prepared for the next printing task (washing, gluing of printing forms, etc.).
Directly on the pivot 8 of the central impression cylinder a bearing 10 is provided, in order to clamp the movable arm 4 by means of a flange 11. The movable arm 4 is fixedly connected on the pivot 8 of the central impression cylinder 1 via the bearing 10, it is rotatable around the axis of the central impression cylinder 1, and in the rest position of the movable arm 4, it is preferably latched by means of latching means 7 to the frame 13 of the rotary printing machine. The pivot 8 of the central impression cylinder is then moved to another bearing housing.
The method for adjusting the position of form cylinders 2 in the rotary printing machine is characterized in that, at the beginning of the cycle, the central impression cylinder 1 rotates in the direction of a strip of material during printing to the so-called rest position of the movable arm 4 with the sensor 5, wherein the rotating action takes certain time, for example, up to 15 sec. The movable arm 4 is clamped to the central impression cylinder 1 by means of the clamping means 6, and in an exemplary embodiment, the movable arm 4 is unclamped from the frame 13 of the rotary printing machine.
Rotation of the central impression cylinder 1 to the rest position of the movable arm 4 is performed so that the latch provided on the central impression cylinder 1 would face the movable arm 4, which is clamped to the central impression cylinder 1 by means of clamping means 6, preferably a cam positionable via a pneumatic cylinder. The cam of the clamping means 6 arranged on the movable arm 4 is inserted by means of the pneumatic cylinder into the latch provided on the central impression cylinder 1 so that when the pneumatic cylinder is ejected, the cam leans on the sides of the shaped latch on the central impression cylinder 1 and tension formed in the clamping means 6 allows the movable arm 4 to clamp accurately to the central impression cylinder 1.
The clamping means 7 may be in form of a pulling pin with pneumatic latch. In such case, only a flange with circular opening, into which the pulling pin is inserted, is provided on the movable arm 4. The pulling pin is positionable by means of the pneumatic cylinder, and together with the pneumatic cylinder it is arranged in the side wall of the printing unit. Unclamping of the movable arm 4 from the rest position of the movable arm 4 is then performed by pulling the pulling pin by means of the pneumatic cylinder.
Subsequently, the movable arm 4 gradually rotates together with the central impression cylinder 1 driven by its own drive in the direction of the strip of material to each form cylinder 2. For adjusting the position of the form cylinder 2, the movable arm 4 with the central impression cylinder 1 stops in a position for adjusting the first printing unit so that the sensor 5 would get to the plane connecting the axis of the central impression cylinder 1 and the axis of the form cylinder 2 in the adjusting position. Then, the form cylinder 2 shifts to the adjustment position and rotates so that the reference sign 9 would get exactly to the axis of the sensor 5. In practice, adjusting of the form cylinder 2 and detection of the position of the reference sign 9 is controlled by an algorithm, which evaluates the difference between the real position of the reference sign 9 and the desired position, and the adjustment is repeated until a max. variation of these positions is reached. The algorithm takes into account tension in the arrangement of the form cylinder 2 and "learns" how to deal with it based on the first adjustment so that the most accurate position would be achieved (i.e. minimum difference between the real and the required position of the reference sign 9 ) in the shortest possible time. Improving the accuracy, in order to meet the requirement of the maximum allowed variation of the reference sign 9, is typically performed after 3 to 4 attempts, after which the central impression cylinder 1 with the movable arm 4 continues by rotating in the direction of the strip of material into the position of adjustment of another printing unit, by a predetermined angle, to set the next form cylinder 2. Setting time of one form cylinder 2 together with changing the position of the movable arm 4 is, for example, 40 sec. After adjusting the last form cylinder 2, the movable arm 4 together with the central impression cylinder 1 rotates in the opposite direction of the strip of material during printing, back to the rest position of the movable arm 4, in which the movable arm 4 unclamps from the central impression cylinder 1, wherein the cam can be pulled out of the latch by means of the pneumatic cylinder, and subsequently, the movable arm 4 unclamps and preferably clamps to the frame 13 of the rotary printing machine, which takes certain time, for example, up to 20 sec.
In another exemplary embodiment, the adjustment is performed always with two printing units using a movable system of two movable arms 4 with the sensors 5 simultaneously.
Rotation of the form cylinder 2 is solved by an own servo-drive of the form cylinder 2. Shifting of the form cylinder 2 is solved by moving it in its position on the side of the drive. Typically, in case of all rotary printing machines, the side shift of the form cylinders 2 is allowed, so that simultaneous printing could be set in a transverse direction. During setting the position of form cylinders in a rotary printing machine with automatic printing settings, the side shift of the form cylinder 2 is enlarged in comparison to conventional solutions, so that the print sleeve with the reference number 9 would shift to the level of the sensor 5 in the movable arm 4, next to the central impression cylinder 1.
The sensor 5 on the movable arm 4 and the reference number 9 on the print sleeve are intended exclusively for setting the simultaneous printing (rotation and side shift of the form cylinder 2 relative to the other form cylinders 2 ). The value of printing pressure is detected on an assembly device (device for assembly/gluing of print forms onto print sleeves). The correct value of pressure is saved in RFID sensor on the print sleeve and the same value is read upon insertion of the print sleeve to the rotary printing machine. The form cylinders 2 are adjusted in a different position than the printing position, in the so-called adjustment position, and just before initiation of printing, the form cylinders 2 get into contact with the central impression cylinder 1, moving to the so-called print position.
The rest position of the movable arm 4, thus the position in which the movable arm 4 is clamped to the frame 13 of the rotary printing machine, can be α₀ = 0°. The particular positions for adjusting the printing units in a specific rotary printing machine vary depending on the print length and the structural arrangement of the machine (according to the diameter of the central impression cylinder 1 and arrangement of the printing units), wherein the print length is the maximum length of a print form, which may be fixed on the surface of the given print sleeve. With the print length of 380 mm, the positions for adjustment of the next printing unit of the movable arm 4 for adjusting eight form cylinders 2, ordered from 1 to 8, can be as follows: α₁ = 38,8°, α₂ = 74,9°, α₃ = 105,1°, α₄ = 141,2°, α₅ = 218,8°, α₆ = 254,9°, α₇ = 285,1°, α₈ = 321,2°.
The length of the movable arm 4 can correspond to the diameter of the central impression cylinder 1 or be shorter by 10 mm than the diameter of the central impression cylinder 1 and on its end the sensor 5 is provided, increasing the length of its own movable arm 4. More particularly, the length of the movable arm 4 is 890 mm, wherein the radius of the central impression cylinder 1 is 900 mm, the width of the movable arm is 4 from 400 to 180 mm (the arm is narrower on its end), and the width of the movable arm 4 is 25 mm.
Two mutually fixedly connected movable arms 4 arranged opposite each other can be provided on the pivot of the central impression cylinder 1, forming a movable system of arms, and on each radial end of these movable arms 4 the sensor 5 for detection of position of the reference sign 9 is arranged. Adjusting is then performed radially and symmetrically in two opposite printing units at the same time and the movable system of arms is rotatable around nearly 180°.
The print sleeve of the form cylinder 2 is not wider than the width of the central impression cylinder 1. The width of the central impression cylinder 1 is determined by the max. width of a strip of material being printed, plus the reserve on the side regulation of the strip position, which is, for example, 30 mm. The width of the print sleeve of the form cylinder 2 is determined by the maximum printing width of the rotary printing machine, plus a reserve added due to geometrically inaccurate ends of the print sleeve, which is, for example, 20 mm. With a maximum print width of 1270 mm, the width of the central impression cylinder 1 can be 1350 mm and the width of the print sleeve of the form cylinder 2 1290 mm, wherein the maximum width of the strip of material being printed is 1320 mm.
The movable arm 4 or the movable system of arms can be arranged on one or the other side of the central impression cylinder 1 , however, it is preferably arranged on the side of the rotary printing machine drive, which is determined by the structural arrangement of the rotary printing machine, not by the function of the system for print settings.
The sensor 5 itself may be easily demounted from the movable arm 4. However, the sensor 5 is precisely aligned. After eventual temporal demounting of the sensor 5 from the clamping means 6, new alignment of the sensor 5 must be performed. The clamping means 6 ensures absolute permanence of the position of the sensor 5 in relation to the central impression cylinder 1 during adjustment of all printing units, thus during one adjustment cycle.
The sensor 5 can be a Hall probe working on the principle of Hall effect, for accurate detection of the position of the reference sign 9 of the particular form cylinder 2. The reference sign 9 is an integral part of the print sleeve on the form cylinder 2, and it is preferably arranged under the print sleeve surface. In case of using a Hall probe, the reference sign 9 consists of a magnet, which is integrated in the print sleeve of each form cylinder 2. The magnet is glued in the wall if the print sleeve provided on the form cylinder 2 by the print sleeve's producer and it does not protrude on the print sleeve surface. A magnet for the sensor 5 of the print setting system can be arranged on the side of the rotary printing machine drive on the unused margin of 10 mm. In order for the magnet to get into the level of the sensor 5 on the movable arm 4 next to the central impression cylinder 1, the form cylinder 2 with the print sleeve, shifts therefore to the side, thanks to which it protrudes over the margin of the print sleeve provided on the form cylinder 2 of the central impression cylinder 1 during print setting.
In case the movable arm 4 is provided on the side of the rotary printing machine drive, the reference sign 9 has to be provided on the margin of the print sleeve, closer to the side of the rotary printing machine drive, thus opposite the movable arm 4, and it should be provided at the same defined position on all print sleeves, e.g. at the angle of 180° from the latch of the print sleeve for the reference column in the print core. The latch of the print sleeve is a slot in the print sleeve (in case of thin print sleeves, it is only a slot in the wall of the print sleeve, in case of print sleeves with thicker wall a metal plate with a slot is fixed/inserted into the wall of the print sleeve) for the reference column in the print core. The reference column is made of steel in the print core, by means of which the position of the print sleeve during sliding in the longitudinal direction (rotation) is secured. The print core consists of a print cylinder, on which the print sleeve with a glued print form is slid. Inaccuracy of the position of the reference sign 9 increases the setting time, however, it does not decrease accuracy of the system.
Data from the sensor 5 are transferred via wire, preferably into a profibus, and then to PLC evaluation. The wire and the pneumatic pipes leading to the elements provided on the movable arm 4 are stored in an energy chain, which allows only one rotation of the movable arm 4 together with the central impression cylinder 1.

Industrial applicability

The above described device and method for adjustment of mutual position of cylinders is further suitable for use in such devices, where there is a need to adjust the mutual position (rotating and shifting in the axial direction) of parallel cylinders accurately.

List of Reference Signs

1-: central impression cylinder
2-: form cylinder
3-: raster cylinder
4-: movable arm
5-: sensor
6-: clamping mechanism
7-: latching mechanism
8-: central pressure cylinder pivot
9-: reference sign
10-: bearing
11-: flange
12-: ink container
13-: rotary printing machine frame

Claims

Method for adjusting the position of form cylinders in a rotary printing machine characterized in that a central impression cylinder (1) rotates to the rest position of a movable arm (4) provided with a sensor (5), the movable arm (4) clamps to the central impression cylinder (1) and subsequently, together with the central impression cylinder (1) driven by a drive of the central impression cylinder (1), the movable arm (4) rotates gradually to each form cylinder (2), wherein for adjusting the position of the form cylinder (2) the movable arm (4) with the central impression cylinder (1) stops so that the sensor (5) aligns with the plane connecting the axis of the central impression cylinder (1) and the axis of the form cylinder (2) in the adjustment position, then the form cylinder shifts into the adjusting position and rotates so that a reference sign (9) provided on a print sleeve of the form cylinder (2) aligns with the axis of the sensor (5), and after adjusting the last form cylinder (2) the movable arm (4) together with the central impression cylinder (1) rotates back to the rest position of the movable arm (4) and subsequently the movable arm (4) unclamps from the central impression cylinder (1).
Method for adjusting the position of form cylinders in a rotary printing machine according to claim 1, characterized in that when the central impression cylinder (1) is rotated to the rest position of the movable arm (4), the movable arm (4), after or at the same time with clamping to the central impression cylinder (1), unclamps from a frame (13) of said rotary printing machine, and before or at the same time with unclamping from the central impression cylinder (1) it clamps to the frame (13) of said rotary printing machine.
Method for adjusting the positions of form cylinders in a rotary printing machine according to claim 1 or 2 characterized in that when two or more form cylinders (2) are being adjusted, at least one movable arm (4) with the central impression cylinder (1) stops so that two and more sensors (5) arranged on at least one movable arm (4) get to a plane connecting the axis of the central impression cylinder (1) and the axis of the respective form cylinder (2), and reference signs (9) of form cylinders (2) which are being adjusted are adjusted to get to the axis of the sensor (5).