GB2331961A

GB2331961A - Device for the mutual throw-on of printing unit cylinders

Info

Publication number: GB2331961A
Application number: GB9826816A
Authority: GB
Inventors: Godber Petersen; Rainer Stamme; Wolfram Fischer
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1997-12-04
Filing date: 1998-12-04
Publication date: 1999-06-09
Also published as: DE19753820A1; GB9826816D0

Abstract

To be able to vary the mutual throw-on with eccentrically mounted printing unit cylinders 3 to 6 without the need to adjust machine elements, the position of the positioning element 26 to 29 that rotates the eccentric bushes 18, 20, 22, 24 can be set directly in a controllable manner. To this end the positioning element can be, for instance, a stepping motor or controllable hydraulic actuator.

Description

2331961 Device for the mutual throw-on of printing unit cylinders The

invention relates to a device for the mutual throw-on of printing unit cylinders, in particular forme cylinders, transfer cylinders and impression cylinders, in which the mutual approach and withdrawal of the cylinders is brought about by rotation about an eccentric mounting.

For print throw-on/off, printing unit cylinders, such as forme cylinders or transfer cylinders, are adjusted by means of eccentric bushes by which they are mounted in side walls of a printing unit. For the adjustment, the eccentric bushes are rotated by means of working cylinders. To set the throw-on pressure of the cylinders against each other, the actuation stroke of the working cylinder is limited, for example by means of adjustable stops. For the setting there is also the possibility of displacing the stroke of the working cylinder by adjusting the piston rod head on the piston rod.

With these devices it is a disadvantage that the stop systems give rise to additional costs. Furthermore, throw-on changes are only possible by means of time-consuming setting changes of stops or piston rod heads.

An Rbject of the invention is thus to create a setting device where the throw-on of the printing unit cylinders can be varied without it being necessary to set machine elements.

In accordance with the invention a controllable positioning element is used to set the cylinder distance directly. Thus within the limits of the construction any desired spacing can be set automatically. The invention makes additional setting or limit elements unnecessary, saves on setting operations and thereby reduces machine stoppage times. Furthermore, the setting process can be automated and the setting can be changed in printing operation, whereby misprints can be reduced and the print quality can be improved.

Further features and advantages are evident from the dependent claims in connection with the description.

For a better understanding of the invention embodiments of it will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 gives a view of a double printing unit, Figure 2 shows the section II according to Figure 1, Figure 3 shows the position of the printing unit cylinders and their eccentricities for adjustment.

Figure 1 shows a so-called double printing unit with the printing units 1 and 2. Each printing unit 1 and 2 contains a forme cylinder 3, 4 and a transfer cylinder 5, 6. For printing, the transfer cylinders 6 are thrown on against each other and print a web 7 which passes through between them. Furthermore, the transfer cylinders 5, 6 in printing operation are in contact with the respectively associated forme cylinder 3, 4. The printing units 1, 2 operate according to an indirect printing method, for example in offset printing, in indirect gravure printing or indirect letterpress printing (letterset). Accordingly, the forme cylinders 3, 4 are covered with a print forme for one of these methods.

The printing unit cylinders 3 to 6 are mounted in side walls 8, 9 (Figure 2). For this purpose, their journals 10 to 17 are mounted in eccentric bushes 18 to 25, which in turn rest in a rotatable manner in the side walls 8, 9. The position of the eccentricities e is of the eccentric bushes 18 to 25 is indicated in Figure 3. On each eccentric bush 18 to 25 a positioning element is articulated, which is likewise supported in an articulated manner on the respective side wall 8, 9. In the embodiment shown, commercially available electro-mechanical setting units 26 to 33 are used. Such an electromechanical setting unit 26 to 33 contains, for example, a stepping motor which, by way of a screw drive, sensitively moves a pushing element and holds it at the specified position arrived at. An adjustable hydraulic working cylinder with position control can also be used, for example, as the positioning element. With such commercial cylinders a setting path is specified by a stepping motor, this path being followed by a hydraulic cylinder. The electromechanical setting units 30 to 33 arranged on the far side wall 9 are not visible in Figure 1 and are therefore only indicated in brackets. The electromechanical setting units 30 to 33 are moved synchronously with the setting units 26 to 29.

The eccentric bushes 18 to 25 are rotated according to the adjustment of the electromechanical setting units 26 to 33 in response to an electronic control command and in this way effect an adjustment of the spacing of the printing unit cylinders 3 to 6 with respect to each other. The distances al, a2, a3 to be set are drawn in Figure 3. The inked forme cylinders 3, 4 (inking units and optionally damping units are not shown) transfer the printed image by way of the transfer cylinders 5, 6 to both sides of the web 7. For this purpose, in addition to an even line force, a defined pressure between the transfer cylinders 5, 6 must also be maintained. The thickness of the web 7 which is guided through between them influences this pressure. The distance a2 between the transfer cylinders 5, 6 is therefore to be set according to the thickness of the web 7. This takes place by means of appropriate control with accompanying positioning of the electromechanical setting units 28, 29 and 32, 33. A position change of the transfer cylinders 5, 6 to change the distance a2 also influences the distances al and a3 between the transfer cylinders 5, 6 and the associated forme cylinders 3, 4. For this reason, to maintain faultless image transfers from the forme cylinders 3, 4 to the transfer cylinders 5, 6, the distances al and a3 of these cylinders with respect to each other must also be adjusted. This takes place by controlling the electromechanical setting units 26, 30 and 27, 31. In this respect, the position of the electromechanical setting units is accordingly adjusted and the rotation of the eccentric bushes 18, 19 or 20, 21, effected in the process, performs the distance change of the forme cylinders 3, 4 with respect to the transfer cylinders 5, 6. With the device it is also possible to make changes to the distances al, a2, a3 during printing and therefore to change printing parameters.

The print throw-off is also realized by means of the electromechanical setting units 28, 29, 32, 33. For this purpose, first of all by means of appropriate control of the electromechanical setting units 26, 30, 27, 31 the forme cylinders 3, 4 are rotated into the extreme positions, with the distances al and a3 reaching a maximum. Subsequently, by means of appropriate control of the electromechanical setting units 28, 32, 29, 33, the transfer cylinders 5, 6 are rotated away from each other so that they release the web 7. The adjusting possibilities of the printing unit cylinders 3 to 6 are indicated in Figure 3 by the arrows 34 to 37.

With certain web guide paths it is also possible that for the print throwoff only one transfer cylinder is or 6 is pivoted away. It is likewise possible that also only one printing unit cylinder 3 to 6 is adjusted for a distance change between two adjacent printing unit cylinders 3 to 6. Accordingly, it is also possible to design only one of two printing unit cylinders 3 to 6, mounted in eccentric bushes 18 to 25, so that it is distance-adjustable.

The invention can also be used with a threecylinder printing unit with forme cylinder, transfer cylinder and impression cylinder. Such a printing unit is constituted, for example, by omitting the forme cylinder 4, using an impression cylinder for the transfer cylinder 6 and keeping the forme cylinder 3 and the transfer cylinder 5. The invention can also be used with printing units operating in direct printing, with, for example, the forme cylinder 3 then only ccoperating with an impression cylinder. Here also it is sufficient if only one of these two cylinders is mounted in eccentric bushes in a distance-adjustable manner, for example the forme cylinder 3 in eccentric bushes 18, 19.

In all the named variants of printing units the device is also usable if the printing unit cylinders 3 to 6 are mounted in a flying manner only in one side wall 8, 9. Such a mounting possibility is shown, for example, in DE 196 24 394 Cl.

For the use of the device it is furthermore insignificant whether the printing unit cylinders 3 to 6 have their own respective drive motors, whether they are in drive connection with another cylinder by way of a spur wheel on a journal 10 to 17 or whether they are not driven at all. Impression rollers or intermediate rollers for gravure printing are named as examples for driveless printing unit cylinders.

Claims

Claims:

1. A device for the mutual throw-on of printing unit cylinders, including at least two cylinders mounted in a machine frame, at least one of these cylinders being mounted in an eccentric bearing enabling distance adjustment of the two printing unit cylinders, and a positioning element engaging the or each eccentric bush for rotating it, characterized in that the position of the positioning element (26 to 33) can be set in a controllable manner according to the desired distance adjustment of the printing unit cylinders (3 to 6).

2. A device according to claim 1, in which an electromechanical setting unit (26 to 33) is used for the positioning element.

3. A device according to claim 2, in which the electromechanical setting unit is a stepping motor.

4. A device according to claim 1, in which an adjustable hydraulic working cylinder is used for the positioning element.

5. A device according to any preceding claims, in which the printing unit cylinder (3 to 6) is mounted on both sides in side walls (8, 9).

6. A device according to one of claims 1 to 4, in which the printing unit cylinder (3 to 6) is mounted in a flying manner in one side wall (8, 9).

7. A device according to any preceding claim, in which the cylinders are forme cylinders, transfer cylinders or impression cylinders.

8. A setting device substantially as described herein with reference to the accompanying drawings.