EP0545237A1 - Inking unit for a printing machine, especially an offset printing machine for sheets - Google Patents

Abstract

An inking mechanism for a rotary offset printing machine in which ink is taken from an ink reservoir in metered quantities and distributed by inking rollers to form an ink film which is adapted to be applied to a printing plate mounted on a plate cylinder, at least one of said inking rollers being a distributing roller mounted for rotational and axial reciprocating displacement. A distributing drive is provided which includes a releasable shift coupling operable for interrupting axial movement of the distributing roller upon a printing stoppage even though the printing machine continues to operate. Upon resumption of printing, the shift coupling is actuatable by a releasing mechanism so that the distributing rollers resume axial reciprocating movement. The illustrated shift coupling is shown as a pair of gear plates arranged between two drive wheels, and alternatively, a friction closure coupling can be used, either of which can be electromagnetically, pneumatically, or hydraulically actuated.

Description

The invention relates to an inking unit for a printing press, in particular a sheet-fed offset printing press according to the preamble of claim 1.

In sheetfed offset printing presses, the ink to be printed is fed via an ink fountain interacting with an ink fountain roller and a metering device (e.g. a large number of zone-wide ink metering elements); a siphon roller and a number of inking rollers on the printing plate stretched around a cylinder. One or more inking unit rollers - usually the one following the lifting roller, the one assigned to the inking rollers and a medium inking unit roller - are designed as so-called friction rollers and perform axial traversing movements during printing.

The friction rollers in an inking unit of the present invention are axially movable back and forth via their journals in the frame walls of the printing press and are connected to a distribution drive. The friction drive is, for example, a transmission which converts the rotary movement of a gear wheel rigidly connected to the plate cylinder via a crank mechanism whose stroke is adjustable and via further linkages into a corresponding reciprocating movement (EP 0 000 329 A1, DD-PS 113 718). In addition to the design of the friction drive as a crank mechanism, cam mechanisms (DE 3 424 721 C2) or gears with swash plates can also be provided. The stroke as well as the point of use of a lateral rubbing generated in this way is determined by the Printer adjusted according to the subject of the printing plate (ink drop in printing direction).

In the case of sheetfed offset printing machines, the paper inlet into the machine must first be blocked in the case of a faulty sheet system and then the printing unit must be switched off after the sheet that has last properly entered the machine. At the same time, the inking rollers stored in the appropriate suspensions are switched off by the plate cylinder and the clocking movement of the lifting roller is interrupted. With such stoppers, the speed of rotation of the printing press can also be automatically reduced. Due to the large number of splitting processes, the lateral rubbing and the lack of ink supply / ink take-off, the ink layer thicknesses are compensated for both in and across the printing direction during printing-free operation. In the upper part of the inking unit, there is a color balance between ink metering zones with large and small ink layer thicknesses. After resuming printing, i.e. After the paper has been properly fed in and the elements switched off have been switched on, a large number of sheets (e.g. pre-run waste) have to run through the printing machine again until a layer thickness distribution on the inking unit rollers is achieved, as was the case before the stopper. The first printed sheets after a stopper thus have strongly pivoting color density gradients across the format width.

In order to reduce the number of waste sheets after a stopper, inking units with a so-called ink flow separation have already become known. Ink flow separation here means that with "Printing from" the ink flow in the inking unit is interrupted at some points by separating the corresponding inking unit rollers. The ink layer thickness compensation then takes place only within a reduced number of inking unit rollers. Such a color flow separation is described, for example, in "Technology of Offset Printing", VEB Fachbuchverlag Leipzig 1989, from page 223 described. Color flow separation, however, prevents compensation of the ink layer thicknesses only in the direction of the inking unit.

The object of the present invention is thus to improve an inking unit for printing machines in accordance with the preamble of claim 1 in such a way that the number of waste sheets after a stopper can be reduced using simple means.

This object is achieved by the characterizing features of claim 1. Further developments of the invention result from the subclaims in connection with the description and the drawings.

According to the invention it is provided to interrupt the lateral rubbing during a stopper by using a shift clutch assigned to the rubbing drive. When the inking rollers are switched off, this clutch can cause the friction rollers to remain in the reverse position of the traversing movement. When the pressure is switched on again - inking rollers on - the shifting movement of the friction rollers is resumed by snapping the clutch in place. The release device that actuates the clutch. In terms of circuitry, it can be linked directly with the "Print on / down" command or with the switch-on and switch-off devices of the inking rollers - mostly pneumatic cylinders.

In a simple embodiment of the invention, the clutch is assigned to the input-side drive wheel of the friction drive and is designed in such a way that this drive wheel can be disengaged on a shaft in a specific angle of rotation position. Such a clutch is advantageously achieved by a form-fitting design of the coupling parts to each other. The form-fitting design of the coupling parts is such that the re-engagement takes place only when the coupling parts are at a certain angle of rotation. This ensures in a simple manner that after a stopper lateral rubbing is continued in phase with respect to the printing unit position. Suitable triggering devices are, for example, electromagnetic devices or devices that become effective when hydraulic fluid is applied - hydraulically / pneumatically. The latter devices are expediently actuated by electrically switchable solenoid valves.

To force peaks when re-engaging the clutch, i.e. To avoid the reconnection of the friction drive, the clutch can also have a pre-synchronization so that when the triggering device is actuated, the one clutch part is first taken along by the other clutch part by frictional engagement and only then does it engage in a positive and correct phase. The times for actuating the triggering device, that is to say engaging or disengaging the clutch, can take place at those times of movement of the friction drive in which the lowest drive torques prevail.

The shift clutches outlined above in terms of structure and function, which can be used in the present invention, are known, for example, from DE 2 854 032 A1 and have two toothed disks which are correspondingly toothed to one another, one toothed disk being axially displaceable relative to the other. Switching clutches which can be actuated electromagnetically and have toothed disks are widely used in sheet-fed printing machines and are used, for example, for coupling and uncoupling the sheet feeder (sheet transport) to the drive of the printing press.

In an inking unit according to the invention, there is no lateral rubbing with a stopper. The ink layer thickness profile located on the inking unit rollers transversely to the printing direction is therefore not rubbed during the stopper. Although the continuous inking unit rollers and the large number of splitting processes also result in an ink cross flow between the zones with high and those with a lower ink layer thickness, this remains the case Ink layer thickness profile obtained transversely to the printing direction with the friction drive switched off considerably longer than with further rubbing movements. The first friction roller following the lifting roller in particular has large ink layer thickness differences, ie a correspondingly significant ink layer thickness profile, which would degrade in a relatively short time if there were further rubbing movements during a stop. An inking unit with a so-called ink flow separation cannot remedy this, since the ink layer thickness gradient in the inking unit direction remains approximately "frozen", but due to the further rubbing movements, especially in the upper part of the inking unit, the ink layer thickness profile transverse to the printing direction is compensated for relatively quickly.

The present invention can be applied to inking units with or without devices for ink flow separation. In the case of a printing press inking unit with a plurality of friction drives for a plurality of friction rollers, provision can likewise be made for only the topmost friction roller (first friction roller) to be stopped with a stopper.

Furthermore, an embodiment of the invention is explained with reference to the following drawings.

Fig. 1

eine dem Verreibungsantrieb zugeordnete Schaltkupplung nach der Erfindung,

Fig. 2

ein Beispiel eines Verreibungsantriebs gemäß der Erfindung.

It shows:

Fig. 1

a clutch according to the invention assigned to the friction drive,

Fig. 2

an example of a friction drive according to the invention.

Fig. 2 shows the friction drive of a friction roller 1 of an inking unit, not shown. The friction roller 1 is mounted with its pin 2 axially back and forth in the side walls of the printing machine, not shown here. On a pin 2 is an arm of a via a transmission ring 3 with an elongated cross section, which engages in a corresponding annular groove of the pin 2 Angle lever 4 articulated. Angle lever 4 is pivotally mounted on the frame with an axis which is perpendicular to that of the friction roller. A rod 5 is rotatably articulated on a second arm of angle lever 4, for example by means of a fork-shaped end. The other end of the rod 5 is articulated on a crank wheel 6 of the friction drive. In order to be able to adjust the stroke of the friction roller 1, the crank wheel 6 has an elongated slot 7 in the radial direction, in which the end of the rod 5 articulated on the crank wheel 6 can be displaced when the locking screw 8 is loosened. The friction drive shown can also drive several friction rollers 1 via special mechanisms.

A drive wheel 9 of the friction drive is coaxially assigned to the crank wheel 6 of the friction drive, which meshes, for example, directly with a gearwheel 10 attached to the plate cylinder (not shown here) (FIG. 1). So that not only the stroke but also the time of use for the lateral rubbing is adjustable, the drive wheel 9 can be rotated relative to the crank wheel 6, for example after loosening screws or similar locking means, so that the angular position of the crank wheel 6 can then be changed relative to the angular position of the plate cylinder .

1, the crank wheel 6 and the drive wheel 9 are assigned a shaft 11, which is seated via a truncated cone in a bearing arranged in the wall of the side stand 12. Crank wheel 6 is fixedly attached to the free end of shaft 11 (or detachable for the adjustment of the starting point of friction), drive wheel 9 is freely rotatable on shaft 11. The end of shaft 11 assigned to crank wheel 6 is rotatably supported via a housing part 11.2. Housing part 11.2 is firmly connected to the side stand 12. The drive wheel 9 can be locked with respect to the shaft 11 via a clutch 13 arranged on the shaft 11.

The clutch 13 consists of a pair of toothed disks 13.1, 13.2, for example a toothed disk 13.1 on the shaft 11 is rotatably connected to the drive wheel 9 and the toothed disk 13.2 is rotatably and axially displaceably (for example via a multi-groove profile 13.3) connected to the shaft 11.

The toothed disks 13.1, 13.2 have an L-shaped profile and on the end face such a toothing 13.4 distributed asymmetrically over the circumference, so that mutual engagement is only possible with a single angle of rotation position. The toothed disks 13.1, 13.2 are pressed together, for example, by a compression spring associated with the toothed disk 13.2 (disc springs - not shown -).

A triggering device 14 in the form of a coil 14.1 which is attached to the housing part 11.2 and is oriented coaxially to the shaft and generates a magnetic field is arranged on the toothed disks 13.1, 13.2. A current flows through this to decouple the drive wheel 9 and shaft 11. The magnetic field generated by the coil 14.1 then tries to reduce the air gap 14.2 formed between the housing part 11.2 and the toothed disk 13.2 against the spring force (disengagement).

Instead of a coil 14.1 and air gap 14.2, the triggering device 14 can also be formed from a pressure cylinder (hydraulic / pneumatic) which can be pressurized and which is arranged in the shaft 11, for which purpose holes for the pressure medium supply would also have to be drilled in the shaft 11.

Instead of the embodiment of the clutch 13 described in FIG. 1 in addition to the release device 14, frictional clutches could also be used. The triggering device 14 of a friction clutch (for example hydraulic) is then acted upon at the exact time with the corresponding working medium, so that the separation or closing of the torque flow between the drive wheel 9 and the crank wheel 6 takes place only at a specific angular position of these wheels. The corresponding time switching points for this would be a rotary angle sensor attached to a single-speed shaft of the printing press, in addition to a computer with a stored target angle position can be removed. The triggering device 14 would then be controlled by correspondingly rapidly reacting solenoid valves. The release device 14 and the frictional properties of the clutch parts would then be dimensioned such that there is only negligible slip during the switching operations.

Reference symbol list

1

Grater roller

2nd

Cones

3rd

Transmission ring

4th

Angle lever

5

pole

6

Crank wheel

7

Long slot

8th

Locking screw

9

drive wheel

10th

gear

11

wave

11.1

warehouse

11.2

Housing part

12

Side stand

13

Clutch

13.1

Tooth lock washer

13.2

Tooth lock washer

13.3

Multi-groove profile

13.4

Gearing

14

Release device

14.1

Kitchen sink

14.2

Air gap

Claims (8)

Inking unit for a printing machine, in particular sheetfed offset printing machine, in which the ink that can be fed on an ink fountain roller across the printing direction in different ink layer thicknesses is applied to a printing form via a number of inking unit rollers and inking rollers and at least one inking unit roller is designed as a friction roller that is rotated by the rotary movement of the Printing unit driven friction drive is driven to periodic axial movements
characterized,
that the friction drive (4-9; 11) is assigned a clutch (13) which can be actuated by a trigger device (14) in such a way that the periodic axial movements of the friction roller (1) can be stopped when printing operation is interrupted and the printing unit continues to run. Inking unit according to claim 1,
characterized,
that the triggering device (14) is connected in terms of circuitry to the organs causing the switching on and off of the inking rollers. Inking unit according to claim 1 or 2,
characterized,
that the clutch (13) is designed as a positive coupling between a crank wheel (6) and the drive wheel (9) of the friction drive, the corresponding coupling parts being designed such that coupling of the crank wheel (6) with the drive wheel (9) only at a certain angular position of the wheels (6, 9) to each other is possible. Inking unit according to claim 3,
characterized,
that the clutch (13) is formed by two toothed disks (13.1, 13.2), each of which is non-rotatably connected to the crank wheel (6) or drive wheel (9) and is seated on a common shaft (11), a toothed disk (13.2) being arranged axially displaceably and which have a toothing distributed asymmetrically over the circumference on the end face and can be actuated by a triggering device (14) which causes an axial displacement. Inking unit according to claim 1 or 2,
characterized,
that the clutch (13) is designed as a friction clutch between the crank wheel (6) and the drive wheel (9), which can be actuated via the release device (14), so that there is a coupling of the wheels (6, 9) only at a certain angular position to each other. Inking unit according to claim 1 or 2,
characterized,
that the clutch (13) is designed as a positive coupling between the crank wheel (6) and drive wheel (9), so that coupling between the wheels (6, 9) is possible with each other only at a certain angle of rotation position and the positive coupling additionally a Frictional pre-synchronization is assigned. Inking unit according to claim 3, 4, 5 or 6,
characterized,
that the triggering device (14) is designed as an electromagnetically actuated device in the form of a coil (14.1). Inking unit according to claim 3, 4, 5 or 6,
characterized,
that the triggering device (14) is designed as a device in the form of a working cylinder that becomes effective when pressure medium (hydraulic / pneumatic) is applied.

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