Method for operating a printing unit

Abstract

The invention relates to a method for operating a printing unit (1) comprising a first forme cylinder (2-1), a first transfer cylinder (3-1), a second transfer cylinder (3-2), a second forme cylinder (2-2), a first inking unit (4-1) and a second inking unit (4-2), wherein in a printing position of the printing unit (1) the first forme cylinder (2-1) is in contact with the first transfer cylinder (3-1), wherein the first transfer cylinder (3-1) is in contact with the second transfer cylinder (3-2) and wherein the second transfer cylinder (3-2) is in contact with the second forme cylinder (2-2). The invention is based on the object of creating a solution in which a substrate web (6) is to be printed on one side with a higher number of colors than the number of printing units (1) to be passed through in I-construction or in series construction. The object is achieved in that the substrate web (6) to be printed is guided from the outlet side (9) into a second cylinder gap (11-2) of the second forme cylinder (2-2) and the second transfer cylinder (3-2) and is printed there directly on a first side by the second forme cylinder (2-2), the second transfer cylinder (3-2) being at least partially wrapped around by the substrate web (6) and the first side of the substrate web (6) being printed by the first transfer cylinder (3-1) and being guided out of the printing unit (1) in the direction of the outlet side (9).

Description

[0001] The invention relates to a method for operating a printing unit comprising a first forme cylinder, a first transfer cylinder, a second transfer cylinder, a second forme cylinder, a first inking unit and a second inking unit, wherein in a printing position of the printing unit the first forme cylinder is in contact with the first transfer cylinder, wherein the first transfer cylinder is in contact with the second transfer cylinder and wherein the second transfer cylinder is in contact with the second forme cylinder, wherein the first inking unit is in contact with the first forme cylinder and the second inking unit is in contact with the second forme cylinder, and wherein the first transfer cylinder and the second transfer cylinder rotate in opposite directions such thatthat a substrate web to be printed can be conveyed in a direction from an inlet side of the printing unit to an outlet side of the printing unit when passing through a printing gap created between the first transfer cylinder and the second transfer cylinder.

[0002] Printing presses and printing units designed as so-called I-printing units or in-line printing units are known from the prior art. These are used in an offset printing unit design in so-called commercial or illustration printing presses. A printing press for four-color printing on a web thus usually comprises four such printing units, through which the substrate web to be printed is guided horizontally through the printing units, allowing the substrate web to be printed in four colors on both sides without the printed web being deflected by other cylinders or web guide rollers.This is particularly advantageous when printing heatset or UV printing inks and / or when using a substrate web made of coated or non-absorbent printing material, since the printing ink applied to the substrate web only dries after passing through a drying device and is therefore only mechanically resilient after passing through a drying device.

[0003] Therefore, printing units with such a design, which are referred to as I-printing units or in-line printing units, are often used in illustration or commercial printing machines, where coated papers and heatset inks are often printed to create the gloss effect.

[0004] Such printing presses often comprise four printing units, each for printing on both sides of the substrate web in monochrome, although printing presses with five or six such printing units are also known. Even if such printing units have two transfer cylinders and two forme cylinders, it is also possible for such a printing unit to print a substrate web on only one side. For this purpose, for example, in a printing unit designed as an offset printing unit, a dummy plate is mounted on the non-printing side of the substrate web on the forme cylinder designed as a plate cylinder. However, this dummy plate cannot transfer a print image.

[0005] Although single-sided printing of the substrate web is possible with such printing units in I-construction, it is only known from the prior art that with such printing units, which only comprise two transfer cylinders and two forme cylinders, namely a first forme cylinder and a first transfer cylinder for printing the first side of the substrate web and a second forme cylinder and a second transfer cylinder for printing the second side of the substrate web and do not contain an additional impression cylinder such as, for example, imprinting units in 5-cylinder construction, one side of the substrate web can only be printed with the same number of colors as the number of printing units that can be passed through with the substrate web.

[0006] However, if one side of the substrate web is to be printed with a higher number of colors than the number of printing units, this is not possible with current production methods and printing presses. Additional colors can be, for example, colors for six-color printing or special colors such as metallic colors.

[0007] The invention is therefore based on the object of creating a solution which makes it possible to print a substrate web on one side with a higher number of colours than the number of printing units to be passed through in I-construction or in-line construction.

[0008] The object is achieved according to the invention in that the substrate web to be printed is guided from the outlet side into a second cylinder gap of the second forme cylinder and the second transfer cylinder and is printed there directly on a first side by the second forme cylinder, wherein the second transfer cylinder is at least partially wrapped around by the substrate web and wherein the first side of the substrate web is printed by the first transfer cylinder and is guided out of the printing unit in the direction of the outlet side.

[0009] Such a solution has the advantage that one side of the substrate web can be printed in two colors using only one printing unit for double-sided, single-color printing of the substrate web.

[0010] If the method according to the invention is applied to a printing unit of a printing machine comprising four printing units, the substrate web can be printed on one side with five colors.

[0011] According to one embodiment of the invention, the substrate web is guided to the inlet side of the printing unit and guided around the printing unit by means of at least one web guiding device and guided to the second cylinder gap by means of at least one web guiding device.

[0012] Such a solution offers the advantage that the web guide can be passed through a plurality of printing units in a plurality of successively arranged printing units, regardless of whether the substrate web is printed in one side multi-colour in only one printing unit or in several printing units in one side multi-colour.

[0013] According to a further embodiment of the invention, the printing unit is designed as an offset printing unit.

[0014] This design offers all the advantages of offset printing, such as the correction of ink flow independent of the printing form, as well as very simple, fast, and cost-effective production of the printing form. This allows one side of the substrate web to be printed first using the dilitho printing process and then using the standard offset printing process, or vice versa, resulting in very high print quality.

[0015] According to a further embodiment of the invention, the substrate web is fed to at least one further printing unit after one-sided printing and / or the substrate web is printed by at least one printing unit before one-sided printing.

[0016] Such a solution has the advantage that one side of the substrate web can be printed in four colors using only two printing units for double-sided, single-color printing of the substrate web.

[0017] If the method according to the invention is applied to a printing unit of a printing machine comprising four printing units, the substrate web can be printed on one side with up to eight colors.

[0018] Preferred developments of the invention will become apparent from the dependent claims and the following description. Various embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 A printing unit in series design in a mode of operation known from the state of the art Fig. 2 A printing unit in series construction in an operating mode according to the invention Fig. 3 A printing unit in series construction in an operating mode according to the invention with web guiding devices

[0019] Fig. 1 shows a printing unit 1 known from the prior art in I-construction or in-line construction, as is known, for example, in offset printing units for web-fed commercial printing presses from the prior art.

[0020] Such a printing unit 1 comprises four printing cylinders arranged essentially in series, namely a first forme cylinder 2-1, a first transfer cylinder 3-1, a second transfer cylinder 3-2, and a second forme cylinder 2-2. Furthermore, the printing unit 1 comprises a first inking unit 4-1 for inking the first forme cylinder 2-1 and a second inking unit 4-2 for inking the second forme cylinder 2-2.

[0021] In a printing position of the printing unit 1, the first forme cylinder 2-1 is in contact with the first transfer cylinder 3-1, the first transfer cylinder 3-1 is in contact with the second transfer cylinder 3-2 and the second transfer cylinder 3-2 is in contact with the second forme cylinder 2-2, the first inking unit 4-1 is in contact with the first forme cylinder 2-1 and the second inking unit 4-2 is in contact with the second forme cylinder 2-2. The first transfer cylinder 3-1 and the second transfer cylinder 3-2 rotate in opposite directions such that a substrate web 6 to be printed can be conveyed in a direction from an inlet side 8 of the printing unit 1 to an outlet side 9 of the printing unit 1 when passing through a printing nip 10 created between the first transfer cylinder 3-1 and the second transfer cylinder 3-2.

[0022] At the Fig. In the exemplary printing unit 1 shown in Figure 1, the substrate web 6 is guided from the right side and thus from the inlet side 8 of the printing unit 1 through the printing gap 10 between the first transfer cylinder 3-1 and the second transfer cylinder 3-2 and printed there, for example using the offset printing process. The thus printed substrate web 6, which usually passes horizontally through the printing unit 1, leaves the printing unit 1 on the outlet side 9 and is then either Fig. 1 processing station not shown or another in Fig. 1 not shown printing unit 1.

[0023] Is the Fig. 1 is designed as an offset printing unit, at least one printing plate is mounted on each of the first forme cylinders 2-1 and the second forme cylinder 2-2, and the first transfer cylinder 3-1 and the second transfer cylinder 3-2 each carry at least one printing blanket, also referred to as a rubber blanket, on their circumferential surface. The print image of the printing plate mounted on the first forme cylinder 2-1 is transferred via the first transfer cylinder 3-1 and printed onto the first side of the substrate web 6. The print image of the printing plate mounted on the second forme cylinder 2-2 is transferred via the second transfer cylinder 3-2 and printed onto the second side of the substrate web 6. The substrate web 6 can thus be printed on both sides in one color, i.e. with one printing ink, until it leaves the printing unit 1 on the outlet side 9.In a conventional offset printing process, the application of a dampening solution is also required, which is why the printing unit 1 can also comprise a first dampening unit 5-1, which is in contact with the first forme cylinder 2-1, and why the printing unit 1 can also comprise a second dampening unit 5-2, which is in contact with the second forme cylinder 2-2.

[0024] Fig. 1 shows a printing unit 1 as it is operated according to the prior art, namely that the substrate web 6 passes through the printing unit 1 essentially in a straight line and can be printed in one color on the first side and on the second side.

[0025] Although printing units with five or six printing cylinders are also known from the prior art, it should be noted that the method according to the invention relates exclusively to printing units which comprise a first forme cylinder 2-1, a first transfer cylinder 3-1, a second transfer cylinder 3-2 and a second forme cylinder 2-2, but do not comprise an additional fifth or sixth printing cylinder such as, for example, an impression cylinder designed as an impression cylinder.

[0026] Fig. 2 shows the same printing unit 1 from the Fig. 1, which, however, uses a different procedure than in Fig. 1 is operated.

[0027] In the Fig. 2, the substrate web 6 to be printed is guided from the outlet side 9 into a second cylinder gap 11-2 of the second forme cylinder 2-2 and the second transfer cylinder 3-2 and there is printed directly on a first side by the second forme cylinder 2-2. The second transfer cylinder 3-2 is at least partially wrapped around by the substrate web 6; depending on the inclination of the printing cylinders to the perpendicular to the substrate web 6 or depending on the angular offset between the first transfer cylinder 3-1 and the second transfer cylinder 3-2, the wrap angle at which the substrate web 6 wraps around the first transfer cylinder 3-1 is essentially 180°.

[0028] Subsequently, the first side of the substrate web 6 is printed by the first transfer cylinder 3-1, in that the print image located on the first forme cylinder 2-1 is transferred to the substrate web 6 by means of the first transfer cylinder 3-1. After the substrate web 6 has been printed by the first transfer cylinder 3-1, the substrate web 6 is guided out of the printing unit 1 in the direction of the outlet side 9. There, the substrate web 6 printed on one side in two colors or on one side in two layers can either be fed to a further printing unit 1 in order to be printed there either on one side or on both sides, or the substrate web 6 printed on one side in two colors or on one side in two layers can be fed to a Fig. 2 additional components not shown.

[0029] If the Fig. 2 is operated purely in the offset printing process, the substrate web 6 is printed by the second forme cylinder 2-2 in the direct offset printing process, which is also known as the dilitho process, in that the print image is printed directly from the printing plate attached to the second forme cylinder 2-2, which is in Fig. 1 and in Fig. 2, is transferred to the substrate web 6. For this purpose, the print image of the printing plate must be reversed, unlike in the normal offset printing process. However, the print image of the first forme cylinder 2-1 can be transferred to the substrate web 6 using the conventional offset printing process, i.e., using the first transfer cylinder 3-1.

[0030] Although Fig. 2 shows an embodiment in which the substrate web 6 is guided into the second cylinder gap 11-2, which is arranged in the lower half of the printing unit 1. It is also possible for the substrate web 6 to be guided into the first cylinder gap 11-1 between the first forme cylinder 2-1 and the first transfer cylinder 3-1, which is arranged in the upper half of the printing unit 1. Due to the selected nomenclature of the first cylinder gap 11-1 and the second cylinder gap 11-2, the invention is independent of the geometric position of the feed and the initial printing of the substrate web 6.

[0031] Fig. 3 shows the same printing unit 1 from the Fig. 1 or the Fig. 2, which is basically the same as in Fig. 2, whereby the Fig. 3, the printing unit 1 also has additional web guiding devices 7, which enables a further possibility of guiding the substrate web 6.

[0032] Fig. 3 shows an embodiment in which the substrate web 6 is guided to the inlet side 8 of the printing unit 1, which means that the substrate web 6 is fed to the inlet side 8 of the printing unit 1. When using a plurality of printing units 1, the substrate web 6 is fed in mostly, although not necessarily, essentially in a horizontal direction. On the inlet side 8, the substrate web 6 is deflected by means of at least one web guiding device 7 and guided around the printing unit 1. Here, the term "guiding around the printing unit 1" means that the substrate web 6, coming from the inlet side 8, is guided either on the top side or on the bottom side around the printing unit 1 to the outlet side 9, i.e. that the printing unit 1 is either passed under or transferred over by the substrate web 6.

[0033] At the Fig. 3, the substrate web 6 is deflected by a total of four web guiding devices 7 such that the substrate web 6 is guided to the second cylinder gap 11-2. However, it is also possible to deflect the substrate web 6 with a number of web guiding devices 7 other than four, so that it is guided to the second cylinder gap 11-2. The type of guidance of the substrate web 6 and the number of web guiding devices 7 depend essentially on the available space.

[0034] The at least one web guiding device 7 can be designed either as a web guiding roller, as a deflecting roller, as a driven pulling roller or, for example, as a deflecting beam with air flow around it.

[0035] The substrate web 6 printed on one side in this way can be fed to at least one further printing unit 1 after one-sided printing, so that the substrate web 6 printed on one side can be printed in a Fig. 2 and Fig. 3 not shown at least one further printing unit 1 can be printed either at least one-sided in two colors and / or both sides at least one color. However, it is also possible that the substrate web 6 before one-sided printing as exemplified in the Fig. 2 or Fig. 3, has already been previously recorded by at least one Fig. 2 or Fig. 3 printing unit 1 not shown.

[0036] The Fig. 2 or Fig. The printing units shown in Figure 3 can, for example, be operated using the offset printing process, so that the first forme cylinder 2-1 and the second forme cylinder 2-2 each accommodate at least one printing plate, and the first transfer cylinder 3-1 and the second transfer cylinder 3-2 are designed as rubber cylinders, which are also referred to as blanket cylinders. In this case, the printing unit can either be operated using the conventional offset printing process, where a dampening solution is applied to the forme cylinder in addition to the printing ink. In this case, the printing unit 1 also comprises at least one dampening unit 5; in this case, the printing unit 1 preferably comprises a first dampening unit 5-1, which can be brought into contact with the first forme cylinder 2-1, and a second dampening unit 5-2, which can be brought into contact with the second forme cylinder 2-2.

[0037] However, it is also possible for the printing unit 1 to be operated using a letterpress printing process. The letterpress printing process can, for example, be a flexographic printing process, in which the printing form consists of a relatively soft, elastic material, in which the printing areas are raised relative to the non-printing areas.

[0038] Such a first relief printing form, such as a flexographic printing form, which is Fig. 2 and Fig. 3 is not shown, can then be applied to the first forme cylinder 2-1, with the inking of the letterpress form or the flexographic printing form taking place via the first inking unit 4-1. The printed image is then applied to the substrate web 6 via the first transfer cylinder 3-1, which corresponds to an indirect letterpress process.

[0039] A second relief printing form such as a flexographic printing form, which is placed in the Fig. 2 and Fig. 3 is not shown, can then be applied to the second forme cylinder 2-2, with the inking of the letterpress forme or the flexographic printing forme taking place via the second inking unit 4-2. The printed image is applied directly to the substrate web 6 by the second forme cylinder 2-2, which corresponds to a direct letterpress process.

[0040] Although from the Fig. 2 and Fig. 3, it is also possible for the printing unit 1 to be operated in a letterpress printing process and simultaneously in an offset printing process. The letterpress printing process can, for example, be a flexographic printing process in which the printing form consists of a relatively soft, elastic material in which the printing areas are raised relative to the non-printing areas.

[0041] A relief printing form such as a flexographic printing form, which is used in the Fig. 2 and Fig. 3 is not shown, can be applied, for example, to the second forme cylinder 2-2, with the inking of the letterpress forme or the flexographic printing forme taking place via the second inking unit 4-2. The printed image is applied by the second forme cylinder 2-2 directly onto the substrate web 6, which corresponds to a direct letterpress process or a direct flexographic printing process.

[0042] An offset printing form, namely an offset printing plate, can be applied to the first forme cylinder 2-1, with the offset printing form being inked via the first inking unit 4-1. Optionally, the offset printing form can also be supplied with dampening solution via the first dampening unit 5-1. The print image is then applied from the first forme cylinder 2-1 via the first transfer cylinder 3-1 to the substrate web 6, which corresponds to a classic offset printing process.

[0043] Although not from the Fig. 2 and Fig.3, it is also possible for the first forme cylinder 2-1, the first transfer cylinder 3-1, the second transfer cylinder 3-2 and the second forme cylinder 2-2 to be aligned with one another in the circumferential direction in such a way that the substrate web 6 is printed continuously in the sense of without interruption in printing by non-printing areas of the first forme cylinder 2-1, the first transfer cylinder 3-1, the second transfer cylinder 3-2 and the second forme cylinder 2-2.Thus, with appropriate rotation of these cylinders, it is possible for the printing area of ​​the second forme cylinder 2-2 to be printed onto an area on the substrate web 6, onto which the non-printing area of ​​the first forme cylinder 2-1 and / or the non-printing areas of the first forme cylinder 2-1, the first transfer cylinder 3-1 and the second transfer cylinder 3-2 are subsequently placed, which is possible, for example, by appropriate circumferential register adjustment of the cylinders mentioned above.

[0044] Thus, a substrate web 6 can be printed with a continuous print image that is not interrupted by non-printing areas, even if the above-mentioned cylinders each have non-printing areas due to the tensioning channels. This is achieved, for example, by the non-printing area of ​​the first forme cylinder 2-1 and the downstream first transfer cylinder 3-1 and the second transfer cylinder 3-2 being covered, so to speak, with the print image of the second forme cylinder 2-2. List of reference symbols 1 printing unit 2 forme cylinders 3 transfer cylinders 4 inking units 5 Dampening system 6 lane 7 Railway guidance device 8 Inlet side 9 Outlet side 10 printing gap 11 Cylinder gap

Claims

[1] Method for operating a printing unit (1) comprising a first forme cylinder (2-1), a first transfer cylinder (3-1), a second transfer cylinder (3-2), a second forme cylinder (2-2), a first inking unit (4-1) and a second inking unit (4-2), wherein in a printing position of the printing unit (1), the first forme cylinder (2-1) is in contact with the first transfer cylinder (3-1), the first transfer cylinder (3-1) is in contact with the second transfer cylinder (3-2) and the second transfer cylinder (3-2) is in contact with the second forme cylinder (2-2), the first inking unit (4-1) is in contact with the first forme cylinder (2-1) and the second inking unit (4-2) is in contact with the second forme cylinder (2-2), and the first transfer cylinder (3-1) and the second transfer cylinder (3-2) rotate in opposite directions such thatthat a substrate web (6) to be printed can be conveyed in a direction from an inlet side (8) of the printing unit (1) to an outlet side (9) of the printing unit (1) when passing through a printing gap (10) created between the first transfer cylinder (3-1) and the second transfer cylinder (3-2), , characterized by that the substrate web (6) to be printed, coming from the outlet side (9), is guided into a second cylinder gap (11-2) of the second forme cylinder (2-2) and the second transfer cylinder (3-2) and is printed there directly on a first side by the second forme cylinder (2-2), the second transfer cylinder (3-2) being at least partially wrapped around by the substrate web (6) and the first side of the substrate web (6) being printed by the first transfer cylinder (3-1) and being guided out of the printing unit (1) in the direction of the outlet side (9). [2] Method according to claim 1, characterized bythat the substrate web (6) is guided to the inlet side (8) of the printing unit (1) and is guided around the printing unit (1) by means of at least one web guiding device (7) and is guided to the second cylinder gap (11-2) by means of at least one web guiding device (7). [3] Method according to one of claims 1 to 2, characterized by that the substrate web (6) is fed to at least one further printing unit (1) after one-sided printing and / or that the substrate web (6) is printed by at least one printing unit (1) before one-sided printing according to one of claims 1 to 2. [4] Method according to one of claims 1 to 3, characterized by that the printing unit (1) is operated in an offset printing process. [5] Method according to claim 4, characterized by that the printing unit (1) comprises at least one dampening unit (5). [6] Method according to one of claims 1 to 3, characterized bythat the printing unit (1) is operated in a high pressure process. [7] Method according to claim 6, characterized by that the printing unit (1) is operated in a flexographic printing process. [8] Method according to one of claims 1 to 3, characterized by that the first forme cylinder (2-1) is operated with the offset printing process and that the second forme cylinder (2-2) is operated with a letterpress process, in particular with a flexographic printing process. [9] Method according to one of claims 1 to 8, characterized by that the first forme cylinder (2-1), the first transfer cylinder (3-1), the second transfer cylinder (3-2) and the second forme cylinder (2-2) are aligned with one another in the circumferential direction in such a way that the substrate web (6) is continuously printed.

Images