EP1243414A1 - Printing method - Google Patents

Abstract

The rotary printing machine comprises several printing cylinders (18,20) which can be placed against, and removed from the print by means of a regulator (32). A control periodically stops and starts at least one (20) of the printing cylinders during operation and within a time-span less than the time the printing cylinder takes to revolve, between the start and stop position. Each of the printing cylinders has its own motor on the axle of the printing cylinder.

Description

The invention relates to a method for printing on a rotary printing press with several printing cylinders that can be set against a printing material web are.

In conventional printing machines of this type, the multiple printing cylinders are used for printing in multiple colors. Examples are flexographic printing machines known in which several inking units, each a printing cylinder have, arranged on the circumference of a common impression cylinder are. The substrate runs over the impression cylinder and is in the individual inking units one after the other with the color separations of the print Printed on the picture. Because the print image changes with every revolution of the printing cylinder repeated, is the print length, that is, the extent of the print Image in the direction of travel of the substrate, by the circumferential length of the Limited printing cylinder. Therefore, for printing large format images a printing press is required in which the printing cylinder has a large diameter have and thus allow a large print length and / or a large have an axial length and thus enable a correspondingly large printing width, so that the image can be printed in landscape format. In both cases an expensive printing press is required, which is so designed that it enables large print lengths and / or print widths.

The object of the invention is to provide a method for printing large format Images with a small and inexpensive printing machine allows.

This object is achieved in that the print image in several elements is split, which is printed with different impression cylinders be, and that at least one of these pressure cylinders during the Printing operation periodically, each for the duration of at least one revolution of the printing cylinder, is turned off by the printing material.

The circumferential length of the printing cylinder therefore does not need to be the same as the total length of the printed image, but only needs the length of the with this Corresponding printing cylinder to the element to be printed. After while one revolution of the impression cylinder, an element of the image was printed, this printing cylinder is at least for one revolution of the substrate turned off so that the corresponding place on the printing material is free remains. In this vacant position, another printing cylinder is used other element of the image printed. The longitudinal register is selected so that the elements successively printed with different impression cylinders complement each other precisely to the desired print image. The largest format the printed image that is printed in this way with a printing press can be limited in one direction by the printing width of the machine, can, however, in the other direction a multiple of the circumferential length of the Printing cylinders, depending on the number of printing cylinders used.

The method thus enables an extremely versatile use of the printing press. If the desired print length is not greater than the circumferential length of the largest printing cylinder, each printing cylinder can use a different color component be used so that a multi-color print with one of the number of Printing cylinder corresponding number of colors is made possible. Optional However, larger image formats can also be printed by at least two printing cylinders can be used for different elements of the same image. If these elements are to be printed in the same color or a common one Color component, however, is the total selection available standing inks are restricted accordingly. However, this is for many practical applications are perfectly acceptable.

One application example is the printing of large-format tablecloths, for example of disposable paper tablecloths. On a printing press with six inking units, for example, is a three-color print with one Printing length possible, which is twice the circumferential length of the printing cylinder.

Another example of practical application is printing on Packaging material, in which the printed images of each use, which later each form a single package, partly matching, but partly also have different picture elements. With the different For example, picture elements can be different type designations, trade a printed packaging date and the like. If in the conventional printing process, the circumferential length of the printing cylinder For example, is three times the useful length, so in one Pass-through printed with a maximum of three different prints become. If a machine with four inking units is used for printing, for however, the print image only requires two colors, e.g. B. a color for the matching single color picture elements and a second color for the variable Imprint, so two inking units of the printing machine remain unused. at the method according to the invention, it is now possible to use the two free inking units also to be used for printing overprints. Every impression cylinder these two inking units can then again produce three different prints, so that in a single print run benefit with a total of nine have different prints printed in a very efficient way.

The invention also relates to a printing press that is used to carry out of the described method is suitable. This printing press has as is known per se, an adjusting device for moving the printing cylinder between one attached to the substrate and one from the substrate parked position and is characterized by a control device, the at least one of the printing cylinders periodically during the printing operation turns on and off.

Advantageous refinements of the invention result from the subclaims.

The actuator is preferably such that the period of time to Moving the impression cylinder between the set position and the set position is required, is significantly smaller than the rotation period of the Pressure cylinder. Such adjusting devices are used in conventional flexographic printing machines an anilox roller, which is used to apply the color to the Printing cylinder serves to park relatively far from the printing cylinder and the printing cylinder to be parked relatively far from the impression cylinder or central cylinder, so that, for example, there is enough space to handle when changing cylinders the cylinder is created. In the printing press according to the invention however, the printing cylinder needs during the periodic on and off movements only moved so far away from the substrate during printing be that no more printing ink is transferred to the substrate. A distance of just a fraction of a millimeter is sufficient. Also at high-speed printing presses can therefore neglect the time required be small in relation to the rotation period of the impression cylinder, so that the elements of the Join the printed image precisely and seamlessly and essentially without overlap to let.

The actuating devices can be designed in a known manner, for example as roller gear spindles with servo motors, in which the adjustment paths can be controlled precisely, so that an exact return to the original Position is possible. These drives act on trestles on which the pressure cylinders are stored and which are guided on ball linear guides, for example.

For the larger adjustment paths when changing cylinders on the one hand and the small ones Adjustment paths during the periodic on and off movements can a two-stage drive system can also be used. The long-stroke adjustment movements are then carried out with the first stage, while the second Level is only responsible for the very short-stroke adjustment movements. In this In this case, the short-stroke adjustment movements can also be limited by stops become. Hydraulic or pneumatic drives or piezoelectric drives can be used.

As a rule, it is advantageous if at least two printing cylinders periodically can be turned on and off. For special applications, for example if the printed image consists of only two elements, namely one relative short print and a background that is solid or periodic Pattern, it is sufficient if only the printing cylinder for printing is on and off.

The following are exemplary embodiments of the invention with reference to the drawing explained in more detail.

Figur 1

eine schematische Darstellung eines Teils einer Flexodruckmaschine;

Figur 2

eine schematische Abwicklung einer Bedruckstoffbahn mit zugehörigen Druckzylindern;

Figur 3

ein großformatiges Druckbild; und

Figur 4

eine schematische Darstellung des Verfahrens zur Erzeugung des Druckbildes nach Figur 3.

Show it:

Figure 1

a schematic representation of part of a flexographic printing press;

Figure 2

a schematic development of a printing material web with associated printing cylinders;

Figure 3

a large format print image; and

Figure 4

3 shows a schematic illustration of the method for generating the printed image according to FIG. 3.

The rotary printing press shown in FIG. 1, for example a flexographic printing press, has a central cylinder 10 with a large diameter, at the Several inking units are arranged. In the drawing are only three inking units 12, 14, 16 shown. A printing cylinder belongs to each inking unit 18, 20, to one not recognizable in FIG. 1, via the central cylinder 10 running printing material web is adjustable, an anilox roller 22 for application of printing ink on the impression cylinder and a chamber doctor blade 24, the serves to ink the anilox roller 22. The pressure cylinders 20 are rotatable Bucks 26 stored, which are slidably guided on guides 28, as in Figure 1 is only shown for the inking units 14 and 16. The anilox roller 22 and the chambered doctor blades 24 are supported on a common block 30 at each end, which can be moved on the same guide 28 or on a separate guide is. The brackets 26 for the printing cylinders are each an adjusting device 32 assigned, which in the example shown by a servo motor 34 and a spindle drive 36 is formed. The blocks 30 is a separate one Actuating device 38 assigned, which also by a servo motor 40 and Spindle drive 42 is formed. The servomotors 34 and 40 have an integrated one With which it is possible to precisely adjust the adjustment paths measure and control. In this way, the pressure cylinder 20 can be precise bring it into a pressure-effective position in which it can be attached to the central cylinder 10 are employed and are therefore in contact with the substrate. As well can the anilox rollers 22 to the printing cylinder 20 and from this Off.

In FIG. 1, in the inking unit 14, the printing cylinder 20 is from the central cylinder 10 turned off so that no ink is transferred to the substrate while in the inking unit 16, the printing cylinder 20 has a printing effect and on the central cylinder 10 is employed. Correspondingly, the inking unit 14 also has Anilox roller 22 turned off by the printing cylinder 20 while it is in the inking unit 16 is employed on the pressure cylinder 20. You could also choose the inking unit 14, that is, with the inking unit that is not currently printing, the anilox roller on the printing cylinder 20 remain on or are switched on and off with a time delay, so that the ink is fed as needed.

Figure 2 illustrates a printing process using the printing machine shown in Figure 1 can be executed. A printing material web 44 is schematic here represented in a settlement. Of the inking units 12, 14, 16 are only the pressure cylinders 18, 20 and drive motors 46 are shown, each directly sit on the axis of the associated pressure cylinder 18 or 20. The drive motors 46 are made electronic by a control device 48 synchronized with each other and with the central cylinder 10, not shown in Figure 2. The control device 48 also acts on the servo motors 34, 40 of the Actuators 32, 38 and thus controls the on and off movements of the Printing cylinder 20. These on and off movements can be done easily while running Printing machine run because of the associated drive motors 46 move with the respective pressure cylinders.

As an example, it should be assumed that the printing material web 44 for production of packaging material. Every benefit N of the packaging material should be provided with a print image, which in the example shown consists of two Elements exists, namely a frame 50 and one that are the same for all purposes text to use varying from use to use 52. With the one described here Procedures are carried out in a single operation, i.e. in one Print run, six different uses printed, which are reflected in their text 52 differentiate. The text prints are in Figure 2 by letter sequences "AAA", "BBB", ..., "FFF" symbolizes.

With the printing cylinder 18 of the inking unit 12, they are used for all purposes matching frame 50 printed. The circumferential length of the impression cylinder 18 corresponds to the length of a panel. With the inking unit 14 Text prints 52 (AAA, BBB, CCC) made for three different uses. For this purpose, the pressure cylinder 20 must be three times the pressure cylinder 18 Circumferential length and thus also three times the diameter (the Drawing is not to scale). It can be assumed that the Printing cylinders 20 have the largest diameter in the printing press is installable. It would therefore not be possible to print all six different text 52 to print with a single impression cylinder. Therefore at the method described here of the printing cylinder 20 of the inking unit 14, after providing three consecutive uses with the text imprints 52 has turned off substrate 44 for the duration of one cylinder revolution, so that the benefits that leave the inking unit 14 alternate with each other Form groups 54, 56 of three benefits each. The benefits of group 54 have one Text imprint 52, while the benefit of group 56 is just blank frames 50 exist.

With the inking unit 16, the benefits of group 56 with three others Provide text printing (DDD, EEE, FFF). For this purpose, the pressure cylinder 20 of the Inking unit 16 turned on and off in push-pull to the printing cylinder of the inking unit 14.

The print image ultimately obtained thus consists of a sequence of benefits six different text prints 52 and has a print length that is twice that is the same as the circumferential length of the impression cylinder 20.

If another inking unit is available, the process can be carried out without any problems generalize to applications where the effective print length is Is three times the circumference of the impression cylinder. The printed image could then, for example from a sequence of nine uses with different text imprints 52 exist. The pressure cylinders 20 would then alternate and clocked for one revolution and for two revolutions switched off.

FIG. 3 shows, as a further example, a tablecloth 58, which has an almost the The entire base area of the tablecloth is filled with a two-tone print image shall be. The printed image here consists of an outer frame 60 which runs a little to the edge of the tablecloth, and a different color Inner surface 62, the length of which is not more than half the length of the tablecloth is. The tablecloth 58 should have the dimensions 1900 x 1300 mm. It is assumed that a printing machine with three Printing cylinders are available, the maximum printing width is not essential is more than 1300 mm and their maximum circumferential length no longer than about 1000 mm. Three printing cylinders are then used for printing a circumferential length of 950 mm is used, which corresponds to exactly half of the Length of the tablecloth.

FIG. 4 illustrates how the complete printed image is generated on the tablecloth 58 can be. The frame 60 is divided into two mirror-image elements 64, 66, which are printed with printing cylinders DZ1 and DZ2 of two inking units, who work with the same color. A third element is through the inner surface 62 formed, which must be printed in a different color. Because the length of the Inner surface 62, however, is smaller than the circumferential length of the printing cylinder, is sufficient a third pressure cylinder DZ3. The on and off phases during of the printing operation are related to each of the three printing cylinders Position of the elements 62, 64, 66 shown on the printing material 44. dashed horizontal lines divide the substrate into sections whose Length corresponds to the circumferential length of the printing cylinder.

The pressure cylinders DZ1 and DZ2 work almost in push-pull, so that the Add elements 64, 66 to frame 60. The start and stop cycle of the Printing cylinder DZ3, on the other hand, is half a period longer than Stroke of the other two pressure cylinders, so that the inner surface 62 in the center of frame 60 is printed.

This exemplary embodiment can also be used analogously to use cases extend longer print lengths and a greater number of elements.

Claims (9)

Method for printing on a rotary printing press with a plurality of printing cylinders (18, 20; DZ1, DZ2, DZ3) which can be set on and off from a continuous printing material (44), characterized in that the printing length of the printed image is greater than the circumferential length of the largest printing cylinder (20; DZ1, DZ2, DZ3), that the print image is divided into elements (50, 52; 62, 64, 66) that are printed with different printing cylinders, and that at least one (20; DZ1, DZ2, DZ3) the printing cylinder is periodically switched off by the printing material (44) during printing operation, at least for the duration of one printing cylinder revolution. Method according to Claim 1, characterized in that the image to be printed consists of a number of successive uses (N) which have at least one element (52) which differs from use to use, and in that these elements (52) have a plurality of printing cylinders (20) are printed, each printing cylinder (20) printing one or more of the elements (52) and the starting and stopping movements of the printing cylinders (20) being timed such that each printing cylinder (20) leaves the blank for which the elements (52) are unprinted one of the other printing cylinders (20) are printed. Method according to Claim 2, characterized in that the printed image has an element (50) which repeats identically for each use and that this element (50) is printed with a separate printing cylinder (18) which remains constantly on. Method according to Claim 1, characterized in that a plurality of printing cylinders (DZ1, DZ2) are switched on and off with a time delay such that the setting of one printing cylinder takes place at the same longitudinal registers as the setting off of another printing cylinder, so that the elements printed by these printing cylinders are separated (64, 66) add register-perfect to a closed figure (60). Method according to claim 1 or 4, characterized in that elements (62), the length of which in the running direction of the printing material (44) is less than the circumferential length of the printing cylinder, are printed with a single printing cylinder (DZ3) and in that the starting cycle of this printing cylinder is offset in time is that the element (62) is inserted in the correct position in the image to be printed. Rotary printing machine for carrying out the method according to one of the preceding claims, with a plurality of printing cylinders (18, 20; DZ1, DZ2, DZ3), which can be individually adjusted to and removed from the printing material (44) with an adjusting device (32), characterized by a Control device (48) which periodically turns on and off at least one (20; DZ1, DZ2, DZ3) of the printing cylinders during printing operation. Printing machine according to claim 6, characterized in that the actuating device (32) is designed to close the periodically adjustable and deactivatable printing cylinder (20) within a period of time which is substantially smaller than one revolution period of the printing cylinder, between the setting position and the setting position adjust. Printing machine according to claim 6 or 7, characterized in that the distance between the setting position and the setting position of the printing cylinder (20) is less than 1 mm. Printing machine according to one of Claims 6 to 8, characterized in that each of the printing cylinders (20) which can be switched on and off periodically has its own motor (46) for driving it, which sits on the axis of this printing cylinder.

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