EP0453850B1 - Device for applying and withdrawing a blanket cylinder in the printing unit of a sheet-fed offset printing machine - Google Patents

Abstract

A device for impression throw-on and throw-off of a rubber cylinder 2 in the printing unit of an offset printing machine is proposed, the rubber cylinder 2 being mounted on both sides in eccentric bushes 4 and the pivoting movement of the eccentric bushes 4 leading to impression throw-on and throw-off taking place by means of a toggle mechanism formed by the tabs 13 and 14. Two double-acting working cylinders 21.B, 21.C, which are arranged in parallel, are connected at their piston rods 23.B, 23.C to a coupler 26. Coupler 26 is articulated on tab 13. Working cylinders 21.B, 21.C can be acted upon both individually and simultaneously with compressed air so that especially in the latter case a particularly rapid throw-off of the rubber cylinder 2 from the printing cylinder 3 and plate cylinder 1 is ensured. <IMAGE>

Description

The invention relates to a device for printing on and off the blanket cylinder according to the preamble of the first claim.

From DE-PS 934 407 it is known, for example, to press the rubber cylinder of the printing unit of an offset printing machine, which is mounted in eccentric bushes, in two phases and with a freely selectable intermediate time on the printing cylinder. For pre-inking, the rubber cylinder is first placed on the plate cylinder, only then is it placed on the printing cylinder. This is achieved by a cam-controlled roller lever with a two-stage jack clutch. The starting and stopping takes place in the area of the opposite cylinder channels. However, the disadvantage of such solutions is the unfavorable machine dynamics, particularly in the case of high-speed printing presses, due to the hard latching of the pawl and the associated high drive torque to be additionally applied by the main drive.

In order to switch the rubber cylinder mounted in eccentric bushings on and off in two stages without sudden torque from the main drive of the printing and plate cylinders, it is known from DE 3 232 171 A1 and DD 86 631 that the movement of the eccentric bushings by means of double-acting pressurized by pressure medium and successively switchable working cylinders. The disadvantage here is the very high design effort and the associated mass, which the bearing levers provided there cause the blanket cylinder and also that the effect of the working cylinder corresponds to a pure series or series connection, whereby the power delivery of a working cylinder always has an effect on the other working cylinder interacting with it.

US Pat. No. 3,067,674 describes a device for starting and stopping pressure with an actuator which can be actuated by pressure medium acting on a toggle lever mechanism and this in turn pivots the eccentric bushes of the rubber cylinder. The disadvantage here is that a three-point working cylinder is necessary for a two-stage printing on and off, which corresponds to a series connection of two double-acting working cylinders and which must be designed to be very expensive in terms of force in today's high-speed printing presses in order to operate the rubber cylinder at high printing speeds in the event of malfunctions to be separated from the impression cylinder quickly enough.

The object of the present invention is therefore to improve a device for printing on and off of the aforementioned type in such a way that two-stage printing on and off is made possible with simple constructional means and furthermore a quick and safe printing off is ensured especially in the case of high-speed printing machines.

The object is achieved by the characterizing features of the first claim. Further developments result from the subclaims in connection with the description and the drawings.

Fig. 1

eine Druckan- und -abstellvorrichtung gemäß dem Stand der Technik,

Fig. 2

die Vorrichtung nach der Erfindung in Druckanstellung,

Fig. 3

obige Vorrichtung in der Stellung mit vom Druckzylinder abgestelltem Gummizylinder,

Fig. 4

die Vorrichtung nach Fig. 2 in der Stellung mit vom Plattenzylinder abgestelltem Gummizylinder.

An advantageous embodiment of the invention is described below. In the accompanying drawings:

Fig. 1

a pressure switching device according to the prior art,

Fig. 2

the device according to the invention in pressure setting,

Fig. 3

the above device in the position with the rubber cylinder turned off from the impression cylinder,

Fig. 4

the device of FIG. 2 in the position with rubber cylinder parked from the plate cylinder.

1 shows a printing unit of an offset printing machine with a plate cylinder 1, a rubber cylinder 2 and a printing cylinder 3. The cylinders are mounted on both sides with their pins in the frame walls of the offset printing machine. The rubber cylinder 2 is mounted on both sides in eccentric bushes 4 for switching the pressure on and off. By pivoting the eccentric bushes 4, the rubber cylinder 2 can be released from the pressure cylinder 3 and from the plate cylinder 1.

In today's offset printing presses, the print setting process proceeds from the print shutdown as follows:
If the channels of plate cylinder 1 and blanket cylinder 2 correspond to each other, i.e. the two cylinders face each other with their channels, by turning the eccentric bushes 4 by a certain angle, blanket cylinder 2 is turned on the plate cylinder 1 and continues to run until blanket cylinder 2 is optimal Has coloration and the first sheet to be printed has reached the printing cylinder 3. If the channels of the blanket cylinder 2 and the pressure cylinder 3 correspond, the pressure adjustment is carried out by turning the eccentric bushes 4 accordingly; thus the first sheet located on the printing cylinder 3 is printed.

Fig. 1 shows the three angular positions A, B, C of the eccentric bushing 4 and an eye 5 fastened to the eccentric bushing 4. In the angular position A, the plate and rubber cylinders 1, 2 as well as rubber and pressure cylinders 2, 3 are in contact with each other . In angular position B, plate and blanket cylinders 1, 2 remain in contact with each other, but blanket and impression cylinders 2, 3 are separate. Angular position C corresponds to the print stop - the rubber cylinder 2 has no contact with the other printing unit cylinders and has the largest gap to the printing cylinder 3.

If only one sheet is missing (wrong system), the channels of the rubber and impression cylinders 2, 3 eccentric bushing 4 are rotated from position A to position B in order to print on the impression cylinder 3 to prevent if the sheet is missing. If the pressure is to be switched off completely (longer interruption), the eccentric bushing 4 is rotated in position C to avoid over-coloring of the rubber cylinder 2 when the channels of the plate and rubber cylinder 1, 2 correspond.

For the rotatability of the eccentric bushes 4, an eye 5 is attached to the latter, to which a tab 7 engages via hinge bolts 6 and which is connected via hinge bolts 8 to a release lever 9 of the release shaft 10. Moving shaft 10 extends across the width of the machine and is supported in both frame walls. The four-bar linkage formed from eccentric bushing 4 with eye 5, release lever 9 and bracket 7 is located on both sides of the machine. The eccentric bushes 4 on both journals of rubber cylinder 2 can thus be rotated into positions A, B, C by correspondingly turning the pull-off shaft 10, and accordingly the axis of the rubber cylinder 2 can be moved parallel to the axes of the other cylinders.

To generate the rotation of the release shaft 10, this has a second lever 11 on a machine side, to which a toggle lever mechanism, which is formed from the brackets 13, 14 and hinge bolts 15, engages via hinge pins 12 and has its abutment in the hinge pin 16 and in an arm of the pressure assist lever 17 sits. Druckbeistellhebel 17 is rotatably mounted about a pin 18 fixed to the frame.

In the Druckan position (eye 5 of the eccentric bush 4 in position A), the toggle lever mechanism formed from the tabs 13, 14 assumes an extended position, ie the hinge pins 12, 15, 16 lie almost in line. In this Druckan position, the pressure supply from blanket cylinder 2 to pressure cylinder 3 can be adjusted via set lever 17. Thus, a spindle nut 19 is attached to the upper arm of the pressure control lever 17, which is driven by an adjusting spindle 20 that is supported in a machine-fixed manner in its axial direction and is adjustable on the outside of the machine by a handwheel. Rotation of the adjusting spindle 20 causes the release shaft 10 via the pressure adjusting lever 17, the extended toggle lever 13, 14 Rotation of the eccentric bushes 4 and thus the contact force of the rubber cylinder 2 to the pressure cylinder 3. Position A thus corresponds to a certain pressure supply. The positions B, C of the eccentric bushes 4 with the eye 5 therefore always refer to the position A, ie they change with this (other pressure provision).

According to the type of the invention, it is now provided that the toggle lever mechanism, formed from the tabs 13, 14, is actuated by means of two parallel-arranged, double-acting working cylinders 21.B, 21.C (FIG. 2). These working cylinders 21.B, 21.C are supported with their base fixed to the frame via swivel eyes 22. The piston rods 23.B, 23.C of the double-acting working cylinders 21.B, 21.C are connected to a coupling 26 by means of pivot pins 24, 25. Tab 13 has a third hinge pin 21 with which it is articulated on coupling 26. The stroke paths of the similar double-acting working cylinders 21.B, 21.C are dimensioned such that the piston rods 23.B, 23.C in the extended state press the toggle lever mechanism of the brackets 13, 14 into the extended position, that is to say, the eye 5 of the eccentric bush 4 assumes position A (Fig. 1). The extended state of the piston rods 23.B, 23.C thus corresponds to the pressure setting.

The double-acting working cylinders 21.B, 21.C are advantageously cylinders which can be pressurized with compressed air, that is to say correspondingly double-acting pneumatic cylinders. The compressed air is provided by a pressure pump of the printing press and passed to the cylinders via pressure lines, with compressed air stores also being provided. The piston rods 23.B, 23.C can then be individually retracted and extended individually via the respective working chambers of the double-acting working cylinders 21.B, 21.C associated with electrically controllable valves, in particular electrically switchable solenoid valves. Of course, it is also possible to design the double-acting working cylinders 21.B, 21.C as hydraulic cylinders, in which case a corresponding hydraulic system effects the strokes of the piston rods 23.B, 23.C. The advantage of designing the working cylinders 21.B, 21.C as a pneumatic cylinder lies in the well-known fact that the compressed air can be discharged via electrically switchable solenoid valves where it is no longer needed. A hydraulic system, however, requires a complex return system (oil circuit). Compressed air is also required at many points in today's sheet-fed offset printing presses, so that the device for supplying and stopping the pressurized air according to the invention can be easily integrated into the pneumatics of the printing press if the system supplying the compressed air is designed accordingly.

Fig. 2 shows like Fig. 1 the extended position of the toggle lever of the tabs 13, 14, that is, the pressure adjustment. For this reason and the inhibiting effect of the eccentric bushes 4, there is also no reaction of the pressure between the blanket cylinder 2 and the pressure cylinder 3, in particular in the case of the so-called channel impacts (inlet and outlet of the channels) on the working cylinders 21.B, 21.C.

If only the rubber cylinder 2 is to be turned off from the pressure cylinder 3 (e.g. missing or late sheet on the system), the corresponding chamber of the working cylinder 21.B is pressurized with appropriate actuation of a solenoid valve, so that piston rod 23.8 moves at maximum speed into it retracted position immersed (Fig. 3).

FIG. 3 shows this pressure cut-off with the rubber cylinder 2 still positioned towards the plate cylinder 1. The toggle lever mechanism of the plates 13, 14 has been displaced into a kinked position by the retracted piston rod 23.B and the coupling 26 thereby pivoted away. Eye 5 of eccentric bushing 4 was pressed into position B by way of the release shaft 10 and release lever 9 (FIG. 1). If the pressure is to be switched on again, this is achieved by pressurizing the corresponding chamber of working cylinder 21.B. Piston rod 23.B thus extends and, via coupling 26, presses the toggle mechanism of the tabs 13, 14 back into its extended position.

As provided, the blanket cylinder 2 is turned off or on by the impression cylinder 3 (corresponding switching times for the solenoid valves) when the channels of the blanket cylinder 2 and the impression cylinder 3 correspond to one another. The last sheet is then still fully printed out or the rubber cylinder 2 does not touch the printing cylinder 3 without a sheet when printing is started. The switching times for the operations described further below are taken from a switching device which detects the angular position of the printing press and forms control signals for the electrically switchable solenoid valves with appropriate commands (print off, rubber blanket coloring, etc.). This switching device can be formed by a high-resolution rotary angle encoder running synchronously with the machine with a downstream computing device. The rotary encoder can be located on a single-speed shaft on the feeder of the sheet-fed printing press.

The rubber cylinder 2 is switched off from the plate cylinder 1 - starting from the position according to FIG. 3 - by switching the working cylinder 21.C in such a way that the piston rod 23.C is immersed in its end position. This also takes place during the correspondence of the channels of the plate and rubber cylinders 1, 2. The toggle lever mechanism of the tabs 13, 14 now assumes its completely kinked position (FIG. 4). 1 eye 5 is rotated from eccentric bushing 4 to position C.

Pressure starting from the position shown in Fig. 4 is now done in reverse order. During the channel correspondence of plate and rubber cylinders 1, 2, the corresponding chamber is switched by working cylinder 21.C - piston rod 23.C extends and presses tabs 13 and 14 into the position according to FIG. 3 via coupling 26. Rubber cylinder 2 is now located on the plate cylinder 1 and is colored.

The positioning of the rubber cylinder 2 against the impression cylinder 3 when the first sheet to be printed lies on the impression cylinder 3 - starting from the position according to FIG. 3 - is carried out by switching the corresponding chamber of working cylinder 21.B, such that piston rod 23.B extends into its end position. The tabs 13, 14 of the toggle lever mechanism assume an extended position - the rubber cylinder 2 is engaged on the pressure cylinder 3.

The previously described three positions of the rubber cylinder 2 relative to the plate and pressure cylinder 1, 3 was achieved by three positions of the articulated bolt 27, corresponding to the angular positions of the toggle mechanism of the tabs 13, 14 according to FIGS. 2, 3 and 4. These three positions of the toggle mechanism , that is, the pivot pin 27 would in principle also be possible by means of a so-called three-point working cylinder (pneumatic, hydraulic) with appropriate control. A three-point working cylinder corresponds to a series connection of two double-acting working cylinders, the cylinder following the first working cylinder being supported, for example, with its pivoting eye on the piston rod of the first. With such a three-point working cylinder, the three positions of the pivot pin 27 described could be approached in a completely equivalent manner. However, the use of a three-point working cylinder has the following basic disadvantage. If the first working cylinder is extended, and if the second one downstream of it is also to be extended (against a force), then an unfolding force fully affects the first (pressurized) working cylinder. Because of the compressibility of the pressure medium, especially with compressed air, there is a more or less strong yielding of the first working cylinder or its piston rod.

However, the three-point working cylinder has another disadvantage. Because the two double-acting working cylinders are connected in series or in series, the stroke lengths (hence three approachable points) do not add up, but the forces of the working cylinders do not. This results in a simple manner from the fact that the second working cylinder must be supported on the first one upstream of it.

According to the invention described above, the rubber cylinder 2 is shut off from the pressure cylinder 3 by immersing the piston rod 23.B, i.e. pulling the hinge pin 27 of the toggle lever mechanism of the tabs 13, 14 downward via coupling 26 with the aid of a force-increasing lever action (FIGS. 2 and 3). Hinge pin 25 acts as a counter bearing and is pressed forcefully upwards. A force acts on the pivot pin 25 parallel to the direction of the piston rod 23.C in such a way that the pivot pin 25 tries to pull the piston rod 23.C beyond its upper end position. However, since the piston end 23.C is in the extended end position, the piston rod 23.C with the working cylinder 21.C acts like a rigid connection between the swivel eye 22 and the pivot pin 25. There is therefore no reaction on the working cylinder 21.C in the sense of FIG Feathers or giving way instead.

At the high printing speeds that can be achieved today (20,000 sheets / h), the phase of lifting the blanket cylinder 2 from the printing cylinder 3 is particularly time-critical, since a too late, i.e. Lifting outside the channel, for example in the case of a missing sheet, due to the inking of the printing cylinder 3, requires a longer downtime because of the necessary cleaning of the printing cylinder 3. It is precisely in this phase that the repercussions that inevitably arise in a three-point working cylinder and are caused by the series connection, have a particularly negative effect on the reaction behavior. Because of the high compressibility of compressed air, the use of pneumatic three-point working cylinders is only possible with great effort (very high pressures).

Another advantage of a device according to the type of the invention results in a switching option with a very advantageous reaction behavior which has not yet been mentioned. If an irregularity is found in the sheet travel (eg double sheet handed over to the pre-gripper, winder), the pressure must be stopped completely by then placing the rubber cylinder 2 immediately at the greatest distance from the printing cylinder 3. Such situations have absolute priority, ie the gradual shutdown during the Channel correspondence between plate cylinder 1, blanket cylinder 2 and impression cylinder 3 has to be avoided, since a fold or double sheet entering the printing zone will cause tremendous shocks in the bearings of these cylinders and cause damage if the blanket is adjusted to the actual paper thickness from blanket cylinder 2 to impression cylinder 3 . To prevent this, the pressure in correspondence of the channels of the rubber and pressure cylinders 2, 3 can be switched off by simultaneous pressurization of the working cylinders 21.B and 21.C, ie coupling 26 pulled by the piston rods 23.B and 23.C brings the toggle mechanism of the tabs 13, 14 - starting from the position according to FIG. 2 - immediately into the position according to FIG. 4. Due to the parallel arrangement of the working cylinders 21.B, 21.C, pivot pins 26 pull the total of the forces of the piston rods 23.B, 23.C, at the same time this pressure shutdown process only takes the time that a piston rod 23.B or 23.C needs for immersion. A normal three-point working cylinder (series connection) would give the same speed advantage (addition of the stroke paths) when pressure medium was simultaneously applied to the working chambers connected in series, but not an addition of the forces generated in the working chambers. This inevitably results from the fact that the working chambers are connected in series, so that the stroke distances add up, but not the forces.

Especially with the high printing speeds and the associated short periods of time (width of the channels) in which blanket cylinder 2 has to be turned off, high forces would have to be applied to turn off blanket cylinder 2, i.e. to move them away from the other printing cylinders (inertia of the mass). In addition, a force has to be overcome when the eccentric bush 4 is rotated from position A to position B according to FIG. 1, since the eccentric bush bearing presses the blanket cylinder 2 more strongly against plate cylinder 1 in this angular range (overpressure). In this angular range, the distance between the axes of plate cylinder 1 and blanket cylinder 2 is reduced. It would be special to apply these high forces at high printing speeds in the shortest possible time A three-point working cylinder to be designed for this type of force is necessary, but it is correspondingly complex.

The pressure starting and stopping device according to the type of the invention thus avoids a complicated, complex, and therefore also expensive three-point working cylinder and enables the use of two similar, double-acting and pressurized working cylinders in a simple manner. In addition, the disadvantages resulting from the principle of a three-point working cylinder are not only avoided, but also supplemented by the advantages of a parallel connection. It should also be noted that a device according to the invention has a particularly favorable effect on the construction volume.

As already described above, the switching times for the pressure switching on and off for the solenoid valves are provided by a switching device which detects the position of the printing unit cylinders in such a way that the switching on and off of the rubber cylinder 2 to / from the printing and plate cylinder 3, 1 takes place in the area of the opposite cylinder channels. The switching times can be selected so that at the beginning of the channel correspondence, i.e. in the opposite pressure end areas of rubber, pressure cylinder 2, 3 or rubber, plate cylinder 2, 1, the corresponding solenoid valves are switched.

However, since a certain dead time and reaction time passes until pressure medium has flowed into the working chambers, the necessary pressure has built up in the working chamber and accordingly the piston gradually reaches maximum travel speed, the time at which, for example, the rubber cylinder 2 moves from the pressure cylinder increases with increasing pressure speed 3 is turned off in the direction of the start of printing, ie it is moved towards the end of the channel area. A further increase in the printing speed also has the effect that the rubber cylinder 2 has not yet reached its end position, for example with respect to the turning off of the printing cylinder 3, when the channels no longer correspond and printing areas are already opposed to one another. The rubber cylinder 2 would thus be at the start of printing possibly take up too little gap to the pressure cylinder 3. The same applies to the shutdown process rubber, plate cylinder 2, 1, and the pressure adjustment processes. The last-mentioned effect occurs precisely at the printing speed if the sum of the dead time and reaction time equals the period of the channel correspondence of the printing unit cylinders.

The sum of the dead and reaction times can be achieved by applying a correspondingly higher pressure medium, i.e. Avoid higher working pressures, but then requires a more complicated, complex and expensive design of the particularly pneumatic system.

To a certain extent, this can be avoided at high printing speeds if, as provided according to the invention, the switching points for the solenoid valves are formed by the switching device not only as a function of the position of the printing unit cylinders relative to one another, but also as a function of the speed. The switching device thus also detects the speed of rotation of the printing press, for example via a tachometer signal or the actual speed of the machine main drive control, and forms correspondingly advanced switching times. When the machine is running slowly, the switching time for the corresponding switching on or off is at the beginning of the channel correspondence, for example, at high speed it is brought forward in proportion to the speed, i.e. it is placed in the area of, for example, the sheet still to be printed. This ensures that the rubber cylinder 2 is always switched on and off in the channel area.

The speed-dependent or printing-speed-dependent ballast angle can be selected in proportion to the speed, but also according to an empirically determined characteristic curve. Such a configuration of a switching device thus additionally reduces the constructional complexity of a device for switching on and off the pressure according to the type of the invention.

Reference list

1

Plate cylinder

2nd

Rubber cylinder

3rd

Impression cylinder

4th

Eccentric bushing

5

eye

6

Hinge pin

7

Tab

8th

Hinge pin

9

Release lever

13

Breakaway wave

11

lever

12th

Hinge pin

13

Tab

14

Tab

15

Hinge pin

16

Hinge pin

17th

Pressure control lever

18th

bolt

19th

Spindle nut

20th

Adjusting spindle

21.B

Working cylinder

21.C

Working cylinder

22

Swivel eye

23.B

Piston rod

23.C

Piston rod

24th

Hinge pin

25th

Hinge pin

26

Paddock

27

Hinge pin

Claims (5)

1. Device for print throw on and throw off of a blanket cylinder in the printing unit of a offset sheet printing press wherein the blanket cylinder is mounted for throwing on and off relative to the plate and impression cylinder on both sides in eccentric bushes, the eccentric bushes are swivellable by means of a toggle lever drive supported on a counterbearing and pivoted to the toggle lever drive are adjusting means actuatable on subjecting to a pressure medium, characterised in that the adjusting means consists of two double acting working cylinders (21.B, 21.C) supported fixed to the framework and arranged in parallel, the piston rods (23.B, 23.C) of which are pivotally connected with a yoke (26) and yoke (26) is connected via a pivot pin (27) with the link (13) of the toggle lever drive constituted by the links (13, 14) and that the working cylinders (21.B, 21.C) can be subjected to a pressure medium for print throw on individually sequentially and for print throw off both individually sequentially and also simultaneously.
2. Device according to claim 1 characterised in that the pivot pins (16) forming the counterbearing of the toggle lever drive formed from links (13, 14) is seated on a pressure adjustment lever (17) mounted about a pin (18) fixed to the frame, this is swivellable to change the pressure adjustment between blanket and impression cylinder (2, 3) by means of a spindle nut (19) and adjusting spindle (20), that link (13) engages via pivot pin (12) on the lever (11) of a throw off shaft (10) and this is pivoted at both ends of the blanket cylinder (2) via throw off lever, link (7) to which eyes (5) installed on the eccentric bush (9) is pivoted.
3. Device according to claim 1 or 2 characterised in that the double acting working cylinder (21.B, 21.C) is constructed as two similar pneumatic cylinders which can be subjected to compressed air and the compressed air feed to the corresponding working chambers of the working cylinders (21.B, 21.C) results via electrically controllable magnetic valves.
4. Device according to claim 3 characterised in that to prepare the switching time points for the magnetic valves a switching device is provided which is constructed such that the position of the printing unit cylinders and also the print speed (rotational speed) are sensed and with increasing print speed as well as in dependence on this the switching time points are advanced in the direction of rotation of the printing unit cylinders in such a fashion so that at any printing speed the throwing on or off of the blanket cylinder (2) on to or away from the impression or plate cylinders (3, 1) takes place in the region of the cylinder channels.
5. Device according to claim 4 characterised in that the switching device is so constructed that the switching time points are advanced proportionally relative to the print speed or following an empirically determined characteristic.

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