EP0509278B1 - Device for controlling the sheet run in the region of laymarks in sheet offset printing machines - Google Patents

Abstract

The invention relates to a device for controlling the sheet run in the region of lay marks in sheet offset printing machines. To ensure that the sheet at the lay marks has as much stabilisation time as possible for self-alignment, it is proposed according to the invention to select the sampling point for sheet scanning at the lay marks in dependence on the condition of the machine (pressure on, pressure off). In both the pressure-on position and the pressure-off position, the sampling point (angular value of a constant speed shaft) is set sufficiently late for the elements which release or lock the sheet run and switch the printing mechanism cylinders on and off to be still actuable. Switching between these sampling points occurs automatically.

Description

The invention relates to a device for controlling sheet travel in the area of the application marks of sheet-fed offset printing presses according to the preamble of claim 1.

At the high machine speeds of sheet-fed offset printing presses required today, the sheets to be printed are removed from the stack of feeders via a conveyor table, which is designed in particular as a suction belt table (DE 3 138 481 C2), to the feed marks. An alignment of the leading edge of the sheet in the direction of sheet travel is then carried out on the contact marks, in particular by additional conveying devices (DE 3 331 662 C2), and also an alignment of the sheet side edge (side mark). After the alignment process, a cam-controlled pre-gripper grips this printed sheet and after the application marks have been pivoted away, the pre-gripper transfers the printed sheet, for example, directly to the gripper system of the impression cylinder.

From the prior art it is known to arrange so-called sheet scanning devices in the area of the application marks, by means of which it can be checked whether the sheet is in time enough (detection of late sheets) and is not so incompletely applied that the pre-gripper does not cover it over its entire width can be grasped (inclined arch). Such sheet scanning devices mostly work according to the light barrier principle, for example as known from DE 3 907 583 A1. The result of the arc scan is negative (Sheet does not fit correctly), the pre-gripper does not grasp the sheet, the contact marks do not pivot, the blanket cylinder is turned off by the impression cylinder and the plate cylinder (print-down). As is sufficiently known from the prior art, the movements of the contact marks (swiveling), those of the pre-gripper (sheet gripping, transfer movement) are generated by gears with cam rollers and roller levers, shift pawls being provided, the engagement of which can interrupt the movements (blocking of the sheet run). It is also sufficiently known from the prior art that in the most widespread sheetfed offset printing presses the blanket cylinder is mounted eccentrically on both sides and can be completely turned off by turning this eccentric mounting of both counterpressure and plate cylinders, for coloring the blanket only on the plate cylinder, but not on the impression cylinder can be adjusted, and can be adjusted on plate and impression cylinders. The eccentric bearings are also rotated by cam rollers, roller levers and controllable pawls. The blanket cylinder is turned on and off on the plate and impression cylinders at the time of the so-called channel correspondence of the corresponding printing unit cylinders, i.e. exactly when the cylinder channels roll against each other.

The sheet scanning devices according to the prior art, however, not only serve to control the sheet infeed when the machine is running, ie the printing press in the print-on position, but also serve to control the sheet infeed in the machine in the print-down position, in which case after detection of a first sheet correctly conveyed to the feed marks, the blocking of the sheet run (feed marks, pre-gripper) is released and the blanket cylinder is first placed on the plate cylinder and then on the impression cylinder which carries this first print sheet.

At high machine speeds, the sheet tends to rebound somewhat from the contact marks (high impact speed), but then to calm down again on its own, i.e. to apply correctly to the contact marks. If the sheet is scanned at a point in time at which the sheet has not yet calmed down (shortly after arrival), such a device for checking the sheet inlet will cause the sheet to be blocked.

From DE 3 044 643 A1 it is known to determine the sampling time in such a way that actuation, i.e. So a control of the organs for sheet release and sheet blocking is possible. The time of measurement is assigned a fixed angular value of a one-turn shaft and is taken, for example, from a clock generator or pulse generator on a single-turn shaft. The sampling time must be chosen such that when the press is on the machine it is still possible to block the sheet inlet and the print-down position of the printing unit, and when the press is down the machine can still release the sheet inlet and the printing on.

Such a rigid assignment of the sampling time to a fixed angular value of a single-turn shaft has the disadvantage that, in certain printing unit and pre-gripper arrangements, the sampling time must be assigned to an angular value of the single-turn shaft, at which the triggering of the print-on actuating process and the release of the sheet travel still is possible. Such printing unit and pre-gripper arrangements are characterized in that the angular value of a single-turn shaft, in which the blanket cylinder can be adjusted to the plate cylinder (channel correspondence) lies before the angular value, at which the release of the sheet path is possible (swiveling off the application marks, triggering the pre-gripper) and this in turn lies in front of the angle value at which the blanket cylinder can be adjusted to the impression cylinder.

With such a sheetfed offset printing machine, should the sampling time be as "late" as possible, be placed in such a way that the sheet has a sufficiently long settling time at the feed marks even at high machine speeds, the sampling time must be assigned an angle value which corresponds to the sheet travel control in the print-down position. The sampling time (angular value) must therefore be placed before the angular value for the blanket cylinder to be applied to the plate cylinder. The time (the angle value interval) between the angle value for the positioning of the rubber blanket cylinder on the plate cylinder and the angle value for releasing the sheet travel cannot be used. The sheet is therefore not given enough time to calm down at the feed marks. If the printing press is in the print-on position, false triggering can often occur, i.e. sheet travel is blocked, printing is stopped, just because the sheet was not correctly aligned with the feed marks at the time of scanning, but could easily have been aligned the next moment. This is almost always the case, especially with a shingled sheet feeder and in connection with additional conveyors in the area of the feed marks.

DE 4 019 293 A1 describes a device for sheet control on the feed marks of printing presses, in which the scanning time is provided variably and inversely proportional to the machine speed. In this way, an increased time for calming the sheets on the feed marks is to be achieved. However, such a device only takes into account the dead time of the organs causing the blocking or releasing of the sheet travel and the switching on and off of the printing unit cylinders. If the machine speed is increased, the sampling time is therefore brought forward. In the printing unit and pre-gripper arrangements described above, the time for calming the sheet is certainly not increased.

From DE-A-2 202 851 a device for automatic print adjustment and later entry and feed control in sheet-guiding printing presses is known, in which in the area of the feed marks it is checked by determining the presence of paper at three sampling times whether a sheet leading edge is correct Time is created or or whether it is an early or late sheet. The three sampling times are not provided as a function of the position of the printing group cylinders relative to one another (print-on / print-off), and accordingly, depending on the position of the printing group cylinders, it is not switched between different sampling times.

The object of the present invention is therefore to design a device according to the preamble of claim 1 such that, in all arrangements of the printing unit cylinder and the arrangement of the pre-gripper for the impression cylinder, the sheet is given a long calming time at the application marks even at the highest machine speeds.

This problem is solved by the features of the characterizing part of the main claim.

Fig. 1

ein Winkelwertdiagramm einer Eintourenwelle mit den Abtastzeitpunkten nach der Erfindung

Fig. 2a) - g)

die Anordnung von Druckwerkszylindern sowie deren Stellungen bei den Winkelwerten a-g nach Fig. 1,

Fig. 3

ein Blockschaltbild einer Bogeneinlaufkontrollvorrichtung nach der Erfindung.

Furthermore, the invention is explained with reference to the drawings. In the accompanying drawing:

Fig. 1

an angular value diagram of a one-way wave with the sampling times according to the invention

2a) - g)

the arrangement of printing unit cylinders and their positions at the angular values ag according to FIG. 1,

Fig. 3

a block diagram of a sheet entry control device according to the invention.

2a) shows a printing unit of a sheet-fed offset printing press, which is characterized by the property described in the introduction to the description with regard to the printing unit and pre-gripper arrangement. In a known manner, an impression cylinder GD, a blanket cylinder GT and a plate cylinder PZ work together. The hatched areas of these cylinders represent their channels. It can be seen that this is a double-sized impression cylinder GD, but this is not a necessary prerequisite for the above property. The printing unit according to Fig. 2a) is in a position in which a previous sheet is still being printed, another, new sheet is currently being grasped by the pre-gripper VG. This new arch is in the area of the system, not shown.

Fig. 1 shows the angular diagram of a single-turn shaft of the printing unit according to Fig. 2a) over more than one revolution. This angle diagram was calibrated to the position of the printing unit according to FIG. 2a), that is to say to exactly the position in which a new printing sheet is gripped by the pre-gripper VG on the system. In the angle diagram according to FIG. 1, the letters b) to g) indicate the angle values of the printing unit cylinder positions according to FIGS. 2b) to 2g). It can be seen that these angular values are those positions in which the printing end DE of the blanket cylinder GT and impression cylinder GD corresponds to one another (FIG. 2b)), the beginning of printing DA of the blanket cylinder GT and impression cylinder GD corresponds to one another (FIG. 2d)), that Printing end DE of blanket cylinder GT and plate cylinder PZ corresponds to one another (FIG. 2e)), the beginning of printing DA of plate cylinder PZ and blanket cylinder GT corresponds to one another (FIG. 2g)). The angle values in the angle diagram according to FIG. 1 under c) and f) correspond to those printing unit cylinder positions in which the centers of the channels of impression cylinder GD and blanket cylinder GT correspond to one another or the channels of blanket cylinder GT and plate cylinder PZ correspond to one another. In the case of a pressure-on / pressure-off actuating gear, consisting of a cam disk, roller lever and shift pawl, the shift pawls can only be in these positions according to FIG. 2c) and FIG. 2f) (more precisely: in a small angular range around these positions) be indented in corresponding notches. Since the actuators which cause this still have a certain reaction time, the switching times which bring about the engagement or disengagement of the pawls must be brought forward accordingly. The same applies to the switching point for switching the pre-gripper on and off, and the contact marks (enabling or disabling the sheet path).

In the diagram according to FIG. 1, X is the angular value of the single-turn shaft, at which the paper run-up of a sheet to the contact mark takes place. If the printing unit is in the print-down state (command given for print-on) and a new sheet with the angular value X reaches the feed mark, then an angular value that has to lie approximately in the interval between e) and f) must have Set command to engage the pawl so that the blanket cylinder GT is then turned on the plate cylinder PZ in the interval between f) and e). Thereupon, up to the angular value a), a second actuating command must be issued so that the sheet travel is released, ie the pre-gripper VG detects this first new sheet. After the first sheet has been gripped by the pre-gripper VG, the angular value between b) and c) is then applied to the blanket cylinder GT against the impression cylinder GD, since the sheet has already been transferred to the impression cylinder and thus through the now colored blanket cylinder GT can be printed. Because of the described arrangement of the printing unit and the resulting processes in relation to the single-turn shaft, in the print-down state the sampling time at angle value A for the first sheet definitely has before angle value f, because of the already mentioned reaction times of the actuators to be the angular value e). This results from the fact that the rubber blanket cylinder GT is to be turned on the plate cylinder PZ in sequence, then the release of the sheet travel is to be switched, whereupon the blanket cylinder GT is turned on the impression cylinder GD.

If the machine is in the print-on state, it can be seen, as in the diagram under FIG. 1, that in the case of a missing sheet, the sheet travel must first be blocked. Then has the blanket cylinder GT from the impression cylinder GD (channel correspondence; interval b) - d)) and then the blanket cylinder GT from the plate cylinder PZ (channel correspondence; interval e) - g)). If the sheet scanning is also carried out at the machine state, print-on, at a sampling time, which is given by the angle value A (FIG. 1), it can be seen that, at high machine speeds, only a very short time interval is available to the sheet at the application marks for its reassurance .

According to the invention, it is now provided to provide a second sampling time with an angle value B in the print-on state for the sheet scanning on the system. This is moved to the rear so that the sheets at the contact marks have a much longer time interval to calm down (interval X - B). This sampling time with the angle value B can, as shown in FIG. 1, be set so late that a safe blocking of the sheet travel (pre-gripper VG from) is still guaranteed even at the highest machine speed. According to the invention, depending on the machine condition, the sheet is scanned at the time (angle value) A or B.

In Fig. 3, a device for controlling the sheet travel according to the invention is shown schematically. The reference numeral 1 denotes a contact table, at the end of which, as is generally known, pivoting contact marks 2 are arranged. A sheet 3 is aligned with these contact marks 2 both in the sheet running direction and laterally thereto. To check the sheet entry, one or more sheet scanning devices 4 are arranged in the area of the application marks, which, as indicated in FIG. 3, can be designed as so-called reflective light barriers. Other scanning devices, such as mechanical touch probes, ultra-acoustic or capacitive probes are also conceivable. For the detection of so-called skewed sheets, two sheet scanning devices 4 can be provided which detect the front edge of the sheet at two points located apart. The sheet scanning device 4 is followed by an evaluation unit 5, which on the one hand the sheet scanning device 4 supplies the necessary operating voltage, but on the other hand also evaluates the output signal supplied by the sheet scanning devices 4 at the times of the angle values A or B with respect to good or missing sheets, so that a signal can be fed to a control device 6. The evaluation unit 5 is operatively connected to a clock generator 7, from which, as shown in the diagram according to FIG. 1, pulses corresponding to two angular values A, B of the single-turn shaft can be taken. The information about whether the machine is in the pressure-on or pressure-down state can be fed to the evaluation unit 5 via a machine status line 8. Depending on the machine state, the pulse at angle value A or pulse at angle value B is thus used by the sheet scanning device 4 for the sampling time or evaluation time. The sheet scanning can be a "real" scanning at the times of the angle values A, B or else a continuous measurement by the sheet scanning device 4, the output signal being evaluated by the evaluation unit 5 at the times A, B. In accordance with the result of the sheet scanning, that is to say the output signal of the evaluation unit 4, the control device 6 then controls the organs which block or release the sheet travel as well as the pressure on and pressure down, the control device 6 likewise with pulses at certain angle values is supplied, in which the corresponding switching operations are to be triggered (for example also by the clock 7). The control device 6 is also supplied with the commands for pushing on and pushing off via lines (not shown).

Reference list

DG

Impression cylinder

GT

Blanket cylinder

PZ

Plate cylinder

VG

Forerunner

THERE

Start of printing

DE

End of printing

1

Investment table

2nd

Landing marks

3rd

bow

4th

Sheet scanner

5

Evaluation unit

6

Control device

7

Clock

8th

Head of machine condition

A

Angular value (sampling time)

B

Angular value (sampling time)

X

Angle value (arch arrival)

Claims (1)

1. Device for checking the sheet running in the region of the front lays (2) of sheet offset printing presses, consisting of a sheet sensing device (4) together with evaluation unit (5), a control unit (6) connected to this which, in accordance with the result of the sheet sensing, controls the freeing or locking of the sheet running as well as the elements for effecting the throwing on or off of the printing unit cylinders at given angular values (A, B) of a one turn shaft and a timing generator (7) permanently in operational connection with the evaluation unit for preparing testing time points releasing the sheet testing in the form of pulses, which correspond to the given angular values of the one turn shaft, characterised in that two sensing time points at two different angular values (A, B) can be extracted from the timing generator (7) and fed to the evaluation unit (5), wherein a first testing time point for a sheet first running into the press with printing unit cylinders set off from one another and pre-selected print on adjustment and a second time sensing point for the sheet checking with a freed sheet running and the printing unit cylinders set against one anotheris set, and that the evaluation unit is so constructed, in dependence on the position conditions of the printing unit cylinders to switch between both of these sensing time points and to control the sheet sensing correspondingly.

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