CH665800A5 - ROLL ROTATION OFFSET PRINTING MACHINE. - Google Patents

Description

DESCRIPTION

The invention relates to a web-fed rotary offset printing machine with at least one printing unit having an impression cylinder, in which a printing medium web is printed in at least two printing processes and dried in a dryer after each printing process and then passed over cooling rollers.

A major disadvantage of web-fed rotary offset printing presses of the aforementioned type is the change in the printing length that occurs during the first drying and cooling process. Depending on the quality of the print carrier web, the printing length can be both lengthened and shortened, which is important for the printing process the back can cause considerable train and register problems.

From DE-OS 3 131 170 a web-fed rotary offset printing machine has become known, in which the problem is solved in that the diameter of the printing unit cylinders can be changed depending on the type of paper, which is achieved by placing calibrated underlay sheets under the rubber blankets or. under the offset printing plates. Such a procedure requires the precise prior knowledge of how the corresponding quality of the print carrier web in the first drying and cooling process will react with regard to the print length and has the major disadvantage that the cylinder diameter can only be adjusted when the machine is at a standstill and only before it is drawn in the print carrier web can take place. A reaction to event. Inconsistencies in the assessment of the behavior of the print carrier web are excluded during operation.

The invention has for its object to provide a web-fed rotary offset printing machine with which the web tension and registration problems shown can be countered during operation.

According to the invention, the object is achieved in that the at least one impression cylinder can be regulated in relation to the peripheral speed independently of the plate / rubber cylinder pairs assigned to it.

In the description, two exemplary embodiments of the invention are explained with reference to the drawing. It shows:

Fig. 1 is a schematic side view of a web-rotary offset printing machine with two so-called satellite printing units

Fig. 2 is a schematic side view of a web-rotary offset printing machine with a satellite printing unit for the two-pass through a half-width print carrier web

3 shows a section through the impression cylinder of a satellite printing unit for a web-fed offset printing machine according to FIG. 2.

In the web-fed rotary offset printing press shown schematically in FIG. 1, a print carrier web 1 is drawn off in a known manner from a supply roll 3 stored in a roll changer 2 and fed to a first satellite printing unit 4, where it is fed by means of four plate / Gummizy-Linderpaare 6 is printed on one side in four colors. After this first printing process, the print carrier web 1 is dried in a first dryer 7 and then passed over a first cooling roller set 8.

For four-color printing of the back, the print carrier web 1 runs through a second satellite printing unit 9, which in turn consists of a central impression cylinder 10 with four plate / rubber cylinder pairs 11 assigned to it. After the second printing process, the print carrier web 1 is dried again in a second dryer 12 and then fed to a folder 14 via a second cooling roller set 13.

Since the printing length can change during the drying and cooling process depending on the quality of the print carrier web 1, web tension and registration problems can occur for the second printing process. In order to be able to counteract this during operation, according to the invention at least one of the two impression cylinders 5, 10 is independent of the plate / rubber cylinder pairs 6, 11 assigned to it, e.g. driven by a commercially available, not specifically shown fine adjustment gear adjustable at circumferential speed. The transmission can be regulated either manually or in conjunction with known web tension measuring and register scanning devices.

The object of the invention can also be achieved in that the peripheral speed is regulated by changing the cylinder diameter. Since it is fundamentally very small change values, this is e.g. to achieve in a known manner by the action of controllable thermal means.

The realization of the inventive idea is also possible in a web-fed offset printing machine according to FIG. 2. The only half-wide print carrier web 15 is also drawn off from a supply roll 16 and, viewed in the axial direction, fed to one half of a satellite printing unit 17. After the first printing process, it is dried in the dryer 18 and fed to a turning device 20 via a first cooling roller set 19. Here it is turned in a known manner and deflected sideways by at least its width parallel to its direction of travel. To print on the back, it now runs through the other half of the satellite printing unit 17. Now it is again dried in the dryer 18 and a second cooling roller

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set 21 fed to the folder 22. In this machine variant, the impression cylinder 23 is subdivided into two cylinder halves 24, 25 which can be driven independently of one another. The first cylinder half 24 is firmly connected to the cylinder axis 26. The second cylinder half 25 is freely rotatably mounted and fixed on the cylinder axis 26

665 800

connected to a drive wheel 27 which is in engagement with a countershaft 28. At least in the drive connection for one of the two cylinder halves 24, 25, a commercially available, as described in FIG. 1, controllable fine adjustment gear is arranged.

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3 sheets of drawings

Claims (6)

665 800 1.Rotary rotary offset printing machine with at least one printing unit having an impression cylinder, in which a printing medium web is printed in at least two printing processes and dried in a dryer after each printing process and then passed over cooling rollers, characterized in that the at least one impression cylinder (5 or 10 ) regardless of the plate / rubber cylinder pairs assigned to it (6 resp. 11) peripheral speed is adjustable. 2. Web-fed rotary offset printing machine according to claim 1, characterized in that the circumferential speed-adjustable impression cylinder is driven by means of a fine adjustment gear. 2nd PATENT CLAIMS 3. Web-fed rotary offset printing machine according to claim 1, characterized in that the diameter of the counter-pressure cylinder which can be regulated at the peripheral speed is variable. 4. Web-fed offset printing machine according to claim 3, characterized in that the diameter change is effected by the action of controllable thermal means. 5. Web-fed rotary offset printing machine according to one of the preceding claims, characterized in that the change in the peripheral speed is automatically controllable. 6. Web-fed rotary offset printing machine according to claim 1, characterized in that for the two passes of a half-wide print carrier web (15) through the same printing unit, the impression cylinder (23) is divided into two cylinder halves (24, 25) which can be driven independently of one another.