EP0078253B1 - Relief printing plates employing rotary printing machine - Google Patents

Description

The invention relates to a rotary printing machine working with high-pressure plates, in which the plate cylinders deliver ink to the printing medium, from which the ink is built up on a printing cylinder of a first printing unit, and ink coming from a further plate cylinder by means of the other side of the printing medium to a printing cylinder of a downstream one Printing unit is built (DE-C-233 984).

In addition to the letterpress process, also called letterpress printing, the planographic printing process has been developed in which, in contrast to letterpress printing, the application of ink is made possible in one plane by the repulsive effect between fat and water.

So that the print carrier does not come into direct contact with the moistened print image, a cylinder covered with a rubber blanket is interposed, which, due to the elasticity of the rubber blanket on the print carrier and on the print image, causes an evenly equalizing color distribution and thus enables a true-to-original print. This process, in which the printed image is released from a flat, ink-rich ink-stained plate via a blanket cylinder to the printing medium, is the classic offset printing. The decisive factor for the quality of the offset print image is therefore the impression of the blanket cylinder, which becomes the actual ink carrier. In multi-color machines, the blanket cylinder also becomes the ink carrier from the previous printing units, because the printing carrier releases ink that builds up on each blanket cylinder as it passes through, and strikes the printing carrier evenly again.

The disadvantage of the offset printing method explained above lies in the mandatory use of water, which is often provided with an alcohol additive, and of ink which dries slowly due to the necessary fat additive. In the case of very fast-running machines with cylinder speeds of 40000-50,000 rpm and a web speed of 7 m / s, the ink on the printing medium, which is mainly paper, must also be printed after printing at very high temperatures, up to 250 ° C, be dried and the vapors released must be combusted; however, these measures prove to be economically unreasonable due to the large amount of energy required and the associated costs.

It is also already known to bring the printed image from a high-pressure image carrier with high-pressure ink onto the blanket cylinder. However, the high-pressure image carrier embosses the stretched rubber blanket at the pressure required for ink delivery, so that the rubber blanket could only be used once or a uniform ink delivery to the print carrier would no longer be guaranteed, which would impair the quality of the offset printing.

The letterpress is undoubtedly the most economical printing process, but it can affect the print quality which a. by the cuddly rubber blankets and by the multiple, thus distributing and equalizing color exchange is not achieved.

It is already known from DE-C-233984 a high-pressure rotary machine of the type described in the introduction, in which the printing lines run between the plate cylinders and associated printing cylinders. With this machine an offset printing effect rubber against rubber is not achieved, but only a simple perfecting.

The object of the invention is to provide a rotary printing machine of the type specified in the introduction, which avoids the disadvantages described above and enables the printing image to be applied to the blanket cylinder with high-pressure ink and an offset printing effect. The rotary printing machine according to the invention is characterized in that the printing cylinders represent blanket cylinders, an offset printing effect rubber against rubber being achieved by pressure lines between the individual blanket cylinders, and in that the last plate cylinder of the last printing unit is followed by an additional blanket and printing cylinder.

This blanket guide means that the blanket is not embossed by the high-pressure plate, because the blanket is connected in between. Since the invention explores the expression of a blanket cylinder against another blanket cylinder, there is a combined high-pressure offset method. The “high-offset printing machine” according to the invention is therefore a machine in which the ink freshly deposited on the printing medium is built up by the latter on a subsequent counterpressure and blanket cylinder and is printed by it. With the help of the printing medium, the colors are built up to the last blanket cylinder, with which the printing is ended, so that all colors are present in a precisely predetermined amount on the last blanket cylinder and a uniform, cloud-free color coverage of the uneven paper surface is achieved. Trailing sections of the printing substrate are used in the invention to compensate and smooth the ink, which is achieved by the multiple color exchange between the printing substrate and the blanket and impression cylinder. The print carrier is preferably an endless or arcuate print carrier.

In the printing press according to the invention, the dampening units in the printing units are advantageously omitted because no more bold ink is used is applied. The high-pressure ink dries faster, so that energy-consuming dryers and the afterburning of the vapors are not necessary. It is sufficient if, according to a further feature of the invention, when using an endless print carrier, the last printing unit is followed by a print carrier deflection for extending the print carrier path for drying the ink before the print carrier enters the folder. The air movement caused by the pressure medium deflection is sufficient for drying. This results in lower manufacturing costs for the machine, and with each start-up there is a significantly lower amount of waste, because the balance between dampening and ink application can only be achieved by running in for a long time.

• Figur 1 eine Seitenansicht einer Rotationsdruckmaschine gemäß der Erfindung ;
• Figur 2 eine Seitenansicht einer für endlose Druckträger bestimmten Ausführungsform der erfindungsgemäßen Maschine und
• Figur 3 eine Seitenansicht einer für bogenförmige Druckträger bestimmten Ausführungsform.

The invention is explained in more detail below using exemplary embodiments with reference to the schematic drawings. Show it

• Figure 1 is a side view of a rotary printing press according to the invention;
• Figure 2 is a side view of an embodiment of the machine according to the invention intended for endless print carriers and
• Figure 3 is a side view of an embodiment intended for arcuate print carriers.

In the rotary printing press shown in FIG. 1, which comprises a plurality of printing units D ₁ -D, _v , connected in series, of essentially the same type, for several colors, an endless print carrier web in the first printing unit D first runs over a plate cylinder 2, onto which a high-pressure plate is clamped, which carries the printed image colored with printing ink. A downstream blanket cylinder 4, which takes the print image directly from the offset plate in the classic offset printing process, acts as a printing cylinder. A blanket cylinder 5 connected downstream of the blanket cylinder 4 has the same function according to FIG. 1 as in the conventional offset printing method, only the print image is built up on the blanket cylinder 5 by means of the printing medium 1 and not from an offset plate.

By means of a plate cylinder 3 connected to the blanket cylinder 5 of the first printing unit D, the printed image is applied to the top of the printing medium 1 and the printing image is built up on a blanket cylinder 8 corresponding to the blanket cylinder 4 of the second printing unit D, while the printing image is produced by a plate cylinder upstream of the blanket cylinder 8 6 of the second printing unit D, 1 is built up via the printing medium 1 on a blanket cylinder 9 connected downstream of the blanket cylinder 8.

The process described above is repeated in the same way in all printing units connected in series until the last print image from the last plate cylinder 10 of the last printing unit D _IV is applied to the printing medium 1. This last print image must be built up by the print carrier 1 onto an additional blanket cylinder 12 assigned to the blanket and impression cylinder 11 of the last printing unit Dv, so that the offset printing from the blanket is given for the last color.

As shown in FIG. 1, the last printing unit Dv is followed by a deflection device 13 for the print carrier web 1, in which the latter is deflected several times, as a result of which the non-greasy high-pressure ink is dried in a non-absorbent print carrier before the print carrier 1 enters a downstream folder 14. A separate heating device for drying is not necessary.

The measure according to the invention, to use the printing medium 1 for building up the ink on the blanket cylinder, can be used both for roller offset machines and for sheet offset machines, but a different arrangement of the cylinders is required than in the conventional offset machines, as is shown in the figures 2 and 3 is shown. The invention enables a simplified machine design with a cylinder arrangement that avoids free paper paths between the individual printing units, as will be explained below.

FIG. 2 schematically shows an embodiment of the invention for web offset machines with a plurality of printing units, which in principle correspond to the printing units of the machine according to FIG. 1. The printed image or a first color is applied to a plate cylinder 18 by means of a printing cylinder 17 on the top of the incoming endless print carrier 1. The printing medium 1 then arrives at a blanket cylinder 19 on which the printed image is built up; at the same time, the print carrier receives on its underside the printed image of plate cylinders 20 and 21, the cylinder 19 acting as a printing cylinder. The print carrier 1 is then taken over by a blanket cylinder 22 on which the color from the print image of the plate cylinders 20 and 21 builds up, and at the same time the print carrier 1 on its upper side takes over the print image from a plate cylinder 23, for which the cylinder 22 printing cylinder is. The color of this print image is built up on a downstream blanket cylinder 24 which also serves as a transfer cylinder to a downstream printing unit. The print carrier 1 is now already printed on the top and bottom with two colors. After the printing carrier 1 has been taken over by a blanket and printing cylinder 25, the ink is applied to the printing carrier from the printed image of a plate cylinder 26 and the process explained above starting from the plate cylinder 18 is repeated in the second printing unit.

The color of the printed image delivered by a plate cylinder 28 to the printing medium 1 is built up on a blanket cylinder 29 connected downstream of the plate cylinder 28, against which a blanket and printing cylinder 27 acts. In this way, the last ink delivery is evened out by a blanket cylinder. The printing medium 1 runs from the blanket cylinder 29 into the deflection device 13 already explained with reference to FIG. 1 and then into the folding device 14.

The rubber to rubber offset printing effect is achieved by the pressure lines between the blanket cylinders 4 and 5, 8 and 9, 11 and 12, 17 and 19, 19 and 22, 22 and 24. 24 and 25 and 27 and 29.

In the embodiment for a sheet-fed offset machine shown in FIG. 3, the operations on sheet 15 already explained with reference to FIG. 2 basically take place; A change results only in that the blanket cylinders are equipped with gripper systems as in sheet-fed offset presses in accordance with the arrangement previously described with reference to FIG. 2 and the first printing cylinder 17 is preceded by a contact cylinder 16 and the blanket cylinder 29 is followed by a delivery cylinder 30 with a delivery system 31. In the device according to FIG. 3, sheets are printed on both sides in one pass using the offset process with high-pressure plates.

In both of the above-described embodiments, the print carrier 1 or 15 can also be printed on one side after the upper or lower plate cylinders 18, 23 or 20, 21 etc. have been switched off. The machine according to the invention can be built printing on one or both sides and with any number of printing units.

Claims (3)

1. Relief printing plates employing rotary printing machine, in which the plate cylinders (2 ; 18) supply colour onto the print carrier (1 ; 15), from which the colour is built up on an impression cylinder (5 ; 19) of a first printing unit, and colour from a further plate cylinder (3 ; 20, 21) is being built up on an impression cylinder (8 ; 22) of a subsequent printing unit by means of the other side of said print carrier (1 ; 15), characterized in that the impression cylinders (5 ; 19 ; 8 ; 22) are rubber cloth cylinders, an offset printing effect rubber against rubber being achieved by the printing lines between the individual rubber cloth cylinders (4, 5 or 8, 9 or 11, 12, respectively ; 19 or 19, 22 or 22, 24 or 24, 25 or 27, 29, respectively), and in that an additional rubber cloth and impression cylinder (12 ; 29) follows the last plate cylinder (10; 28) of the last printing unit.

2. Rotary printing machine according to claim 1, characterized in that the print carrier is an endless or a sheet like print carrier (1 or 15, respectively).

3. Rotary printing machine according to claim 1, characterized in that in case of an endless print carrier the last printing unit is followed by a return means (13) for the print carrier in order to lengthen the path to dry the colour before the entry of the print carrier (1) into the folding apparatus.

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