GB2331960A

GB2331960A - Ductor inking units in printing presses and control thereof

Info

Publication number: GB2331960A
Application number: GB9826774A
Authority: GB
Inventors: Joachim Mueller
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 1997-12-05
Filing date: 1998-12-04
Publication date: 1999-06-09
Anticipated expiration: 2018-12-04
Also published as: GB2331960B; GB9826774D0; DE19753944A1; DE19753944C2; FR2771964B1; FR2771964A1

Abstract

A process and a correspondingly constructed ductor inking unit of a printing press, particularly an offset sheet printing press, are described. A ductor roller (3) movable to and fro between an ink fountain roller (2) and an inking unit roller (4) is brought periodically timewise into contact with the ink fountain roller (2) and with the inking unit roller (4). The timewise ink transfer behaviour can be improved and thereby on printing less waste arises, by arranging that the duration of the contact time of the ductor roller (3) with the ink fountain roller (2) or of the ductor roller (3) with the inking unit roller (4) is sufficient that at all print speeds, the ductor roller (3) rolls against the respective roller (2, 4) by at least one revolution each time it contacts it. This may be achieved by mounting the ductor roller (3) in swivel levers (5), the position of which is controlled by a control cam against the exterior of which rollers (6.1, 6.2) mounted on the swivel lever (5) roll.

Description

2331960 DUCTOR INKING UNITS IN PRINTING PRESSES AND CONTROL THEREOF The

invention relates to a control for a ductor inking unit in a printing press, as well as to correspondingly constructed ductor inking units and associated control mechanisms.

In offset sheet printing presses, the ink which is to be fed is adjusted on an ink fountain roller to different layer thicknesses in metering zones. For this, a number of ink metering elements or the sections of a separated ink knife cooperate with the ink fountain roller. The ink at zonally varying ink layer thicknesses on the ink fountain roller is then taken off from the ink fountain roller by periodic contact with a ductor roller. By means of a further periodic contact of the ductor roller with a further inking unit roller constructed, in particular, as a vibrator roller, the ink is transported further in the direction towards the printing forme. Because of the periodic contact of the ductor roller with the ink fountain roller or the inking unit roller constructed as a vibrator roller, there arises a marked discontinuity in the ink flow from the ink fountain in the direction towards the printing forme and vice versa. This discontinuity is yet further increased if, determined by the ink requirements of the printing forme, a relatively high ductor rhythm is adjusted, i.e. a complete to and fro movement of the ductor roller between the distributor roller and the ink fountain roller is carried out in three or more press revolutions.

In the widespread ductor inking units, the intermittent movement of the ductor roller between the ink fountain roller of the distributor roller is generated by a cam disc driven from the printing unit or inking unit. In addition, running on this cam disc is a roller linked with the swivel lever of the ductor roller. Furthermore, the reduction ratio of the drive with which the cam generating the ductor roller movement is generated from the printing unit or inking unit can be changed. Thus, high ductor cycles (1:3, 1:6, 1:9, etc.) can be adjusted corresponding to the ink requirements of the order to be printed.

As a further adjustment parameter with respect to the quantity of the ink to be fed in the direction towards the printing forme, there is the ductor strip width. In this connection, the period of time of contact of the ductor roller with the ink fountain roller is adjustable so that by means of this variable time interval, the quantity of ink taken up by the ductor roller from the ink fountain roller and accordingly overall the quantity of ink forwarded to the distributor roller is adjustable. The width of the ductor strip is, in this connection, often 1 3 - given as a percentage value, i.e. this percentage value provides how large the ink width is taken on the overall periphery of the ductor roller. The ductor strip width is thereby adjustable in that either the rotational speed of the ink fountain roller is chosen correspondingly, or in that in the ductor roller drive, by means of a rotationally shiftable pair of cam discs, the period of time of contact of the ductor roller with the ink fountain roller is variable.

From DE 44 11 109 Cl, a process for adjustment of the quantity of ink in ductor inking units of printing presses, particularly offset sheet printing presses, is known in which the ductor roller is driven in each case by means of a pair of cam discs rotatable relatively to one another for intermittent movement.

Furthermore, in the case of this previously known process, it is provided that the ink fountain roller can be driven independently of the print speed, i.e. this always turns with an even preset rotational speed. Thereby in the metering slots for generating the ink layer thicknesses on the surface of the ink fountain roller, the same shear force conditions are always present. Thus the printing ink, which has non-Newtonian properties, is always in the same viscous condition independently of the speed of the press. Furthermore, it is provided that prior to changing the print speed, the change of the application angle (ductor roller/ink fountain roller) is introduced and thereafter the change of the print speed is carried out. There thus takes place a timewise advanced change of the ink metering corresponding to the ink changes generated by a print speed change.

From DE 43 14 426 C2, a ductor inking unit is known for a printing press, particularly an offset sheet printing press, in which an ink fountain roller cooperating with an ink fountain is driven by a motor and arranged downstream of the ink fountain roller is a ductor roller intermittently driven by means of a ductor drive between this and a first inking unit roller (distributor roller).

The ink fountain roller is, in this connection, driven by the motor in such a fashion so that this moves with a constant rotational speed independent of the print speed. Thereby the ink metering generates always the same shear force conditions in the ink layers on the ink fountain roller surface. In order to increase or to diminish the quantity of ink on changing print speed correspondingly, the contact (the contact time) of the ductor roller with the ink fountain roller is changed as a function of the print speed. For this, two cam discs are provided rotatable one relative to another on which a roller linked with the swivellable bearing of the ductor roller runs. The cam discs are driven from the printing unit via a phase adjustment drive, the relative rotation of this cam disc takes place via an adjusting motor which is operationally connected with a corresponding characteristic curve store.

Common to the previously described solutions is that the ink fountain roller is driven independently of the print speed by a separate motor and that cam discs rotatable relative one to another are used. Because of the ink fountain roller rotating always with the same peripheral speed, the ink layer on the ink fountain roller always has the same viscous properties so that the inking changes which arise especially at high print speeds can be countered. However, these known ductor drives furthermore have a very marked discontinuous transfer character. The basis for this is to be found in that, corresponding to the ductor rhythm adjusted, a change in the ink feed undertaken on the ink fountain roller (adjustment of an ink metering element with respect to the ink fountain roller) has its effect only after a number of press revolutions in terms of altering the ink layer thickness on the surface of the inking rollers to the far side of the ductor roller or of the vibrator roller cooperating with the ductor roller. Accordingly, the number of press revolutions which is necessary in order to be able to detect a change in the ink feed carried out on the ink fountain roller as a change in inking on the printed material is correspondingly large. These high time constants of known ductor inking units act likewise disadvantageously if, by closing certain ink metering elements, ink from the inking unit can be fed back into the ink fountain. This sort of inking breakdown is, for example, undertaken on changeover to a new print order.

From DE 44 29 481 C2, a process for feeding printing ink into a roller inking unit of a printing press with metering of the printing ink controllable in metering zones and with lateral distribution is known in which, also during continuous printing, certain ink metering elements are, in particular, left closed for a long time. Accordingly there arises in the corresponding metering zones in the upper part of the inking unit an ink flow directed in the direction towards the ink fountain roller which has to be compensated by a correspondingly higher flow in the zones 6 with ink feed. Thereby, the time constants on change of an ink feed, particularly with printing formes with a small proportion of surface to be printed, is notably improved. Especially by this previously known process, one can renounce adjusting to higher ductor rhythms. The time constant for an ink change, however, is still pronounced because of the strongly discontinuous transfer character of the ductor roller cooperating with the ink fountain roller and with the vibrator roller.

is The present invention seeks to improve the process as well as to provide a ductor inking unit using this process wherein the periodic ink transfer behaviour is noticeably improved and thereby, during printing, less waste arises.

According to a first feature of the present invention there is provided a process for controlling a ductor inking unit of a printing press in which a ductor roller is movable periodically to and fro between an ink fountain roller and an inking unit roller, and is thus brought periodically into contact with the ink fountain roller and with the inking unit roller, and wherein the movement of the ductor roller is controlled so that the length of time of the contact of the ductor roller with the ink fountain roller or of the ductor roller with the inking unit roller, at all printing speeds, is sufficient to enable the ductor roller to roll off against the respective ink fountain or inking unit roller for at least one revolution thereof.

In accordance with the invention, the movement of the ductor roller between the ink fountain roller and the inking unit roller (vibrator roller) arranged downstream of the ductor roller takes place in such a fashion that the ductor roller rolls off both against the ink fountain roller and also against the subsequently arranged inking unit roller (vibrator roller) over at least one revolution. By means of this at least one rolling off of the ductor roller during the contact with the ink fountain roller as well as with the vibrator roller, it is guaranteed that the quantity of ink transferred from the ink fountain roller on to the ductor roller and from the ductor roller on to the vibrator roller is transferred wholly - corresponding to the principle of ink splitting during one contact with the respective roller and not an ink layer transferred from the ink fountain roller on to the ductor roller - by further splitting processes - transferred after the next or next but one contact of the ductor roller with the vibrator roller on to this.

The process in accordance with the invention can be used in the case of ductor inking units in which the ink fountain roller has its own drive (motor) as well as also in the case of ductor inking units in which the ink fountain roller is driven via a mechanical drive from the printing unit. If the ink fountain roller has its own drive, which, via a control, makes the rotational speed of the ink fountain roller track correspondingly to the print speed, then the cam disc generating intermittent movement of the ductor roller is to be set out in such a way that the ductor roller, during the contact with the ink fountain roller and during the contact with the distributor roller in each case runs round at least once, i.e. for more than one peripheral length (ductor roller periphery) the ductor roller cooperates with the respective roller.

Correspondingly the diameter of the ductor roller needs to be chosen taking into account the diameters of the ink fountain roller and the distributor roller.

If the process in accordance with the invention is used in a ductor inking unit in which the ink fountain roller is always driven independently of the print speed with an even. choosable peripheral speed, then the diameter of the ductor roller is to be matched relative to the ink fountain and the vibrator roller. In addition to all of this, also a pair of cam discs rotatable relative one to another is to be provided so that, at all print speeds, the contact time of the ductor roller with the ink fountain roller gives at least one revolution of the ductor roller. If the pair of the cam discs are driven direct from the printing unit and also the vibrator roller rotates with a corresponding peripheral speed, the section of the cam effecting the contact of the ductor roller with the vibrator roller can remain unchanged. In order to achieve that the ductor roller cooperates with the ink fountain roller (constant peripheral speed) always to generate at least one overrolling of the ductor roller, the corresponding cam section is adjustable which can be achieved by means of a rotation of the cam disc pair dependent upon the print speed.

According to a further development of the invention, it is provided that the number of rollings off of the ductor roller against the ink fountain roller or against the vibrator roller is chosen to be the same size. Thereby it is achieved that the time constants for transferring ink from ink fountain in the direction towards the inking unit and the other way round are the same size.

- 9 By means of the process in accordance with the invention for controlling a ductor inking unit, a parameter for offset sheet printing presses which would otherwise have to be used for adjusting the ink feed, the ductor strip width, falls away. Because the ductor roller always cooperates over at least one revolution with the ink fountain roller and the vibrator roller, the ductor strip width is constant and also maximum. Accordingly, the matching of the ink feed to the inking requirements of the printing forme takes place exclusively via the ink metering elements.

If the process in accordance with the invention is used in a ductor inking unit in which the ink fountain roller is driven independently in the printing unit via a separate motor (constant rotational speed), then the ductor roller takes up for a period of time, as a function of the print speed after contact with the ink fountain roller and before contact with the vibrator roller, a position between both of these rollers, i.e. out of contact with either one of these rollers. In the case of a constantly driven ink fountain roller, the phase of the contact of the ductor roller with the ink fountain roller relative to the machine angle is different. In contrast to this, the phase of the contact of the ductor roller with the distributor roller with reference to the press angle is always the same. The remaining angular difference of the sum of these angular degrees to 360 or to an integral multiple thereof (corresponding to the ductor rhythm) is then to be taken up by the ductor roller in the intermediate or rest position.

If the process in accordance with the invention is used to control a ductor inking unit with a ductor roller driven by a pair of cam discs one rotatable relative to the other, then the cam discs preferably have three radii, wherein the greatest radius is arranged, for example, to correspond to the contact of the ductor roller with the ink fountain roller, the smallest radius the contact of the ductor roller with the inking unit roller and the middle radius matched to the intermediate or rest position.

In a further development in accordance with the invention, it can be provided that for improving the time behaviour of the ink transfer, the ink layer thickness profile on the ink fountain roller is adjusted to one in which the ink layer in one metering zone is surrounded by two ink layers with greater or with smaller thickness. Overall, accordingly, there thus arises a toothed or comb-like stepped ink profile for adjustment, wherein the average value of the ink layer thicknesses or metering element adjust positions corresponds to the ink requirements of the printing forme. Because the ink metering elements and accordingly the ink layer thicknesses on the ink fountain roller are adjusted varying from metering zone to metering zone, there also arises, at high proportions of the surface to be printed (on the printing forme), at least in the upper parts of the inking unit (ink fountain roller, ductor roller, vibrator roller) an ink flow directed in the zones with smaller ink layer thickness in the direction towards the ink fountain, which is compensated by a correspondingly higher ink flow in the direction towards the printing f orme.

The invention is illustrated, by way of example, with reference to a typical embodiment which is shown diagrammatically in the accompanying drawing, in which Figures 1 to 3 show the principle of the ductor control in accordance with the invention; Figure 4 shows two cam discs rotatable relative to one another; Figure 5 shows the pair of discs of Figure 4 in side view, and Figures 6 and 7 show the two cam discs separately.

The ductor inking unit schematically illustrated in Figures 1 to 3 consists of an ink fountain roller 2 cooperating with an ink fountain I and an inking unit roller 4 constructed as a vibrator roller running parallel thereto. Arranged between the ink fountain roller 2 and the inking unit roller 4 is a ductor roller 3 which, at both of its ends, is rotationally mounted in the movable end in each case of a swivel lever 5. The swivel levers 5 are mounted fast with respect to the frame at a pivot point and have on one end a roller 6 or a pair of rollers 6.1, 6.2 which cooperate with the cam disc as explained in more detail below with reference to Figure 4. Further indicated in Figures I to 3 is spring means by which the pair of rollers 6.1, 6.2 are biased to continuous contact with the cam discs.

Figures 4 to 7 show the cam discs in detail, and the cooperation of the rollers 6.1, 6.2 of the swivel lever 5 with the cam discs. These are denoted 8 and 9 in Figures 4 to 7. The discs are so arranged that if one of the rollers 6.1, 6.2 rolls off on the smallest radius of the cam discs 8, 9, the ductor roller 3 is in contact with the ink fountain roller 2 (Figure 1) and rolls off against this.

If one of the rollers 6.1, 6.2 is located on the largest radius of the cam discs 8, 9 then the ductor roller 3 is in contact with the inking unit roller 4 (Figure 2) and rolls off on this. If one of the rollers 6.1, 6.2 is located on the middle radius of the cam discs 8, 9, then this corresponds to a position of the ductor roller 3 in which this has contact neither with the ink fountain roller 2 nor with the inking unit roller 4.

The ink fountain roller 2 has its own not illustrated drive, by means of which this can be driven independently of the print speed always with an even preset rotational speed (and accordingly also peripheral speed). The rotation of the cam discs 8, 9 relative one to another now takes place arranged in such a fashion that the ductor roller 3 at all print speeds rolls off for at least one revolution against the ink fountain roller 2 (Figure 1). Then the ductor roller 3 takes up the intermediate or rest position shown in Figure 3, following which the ductor roller 3 is then set against the inking unit roller 4 (Figure 2) by the cam sections of the cam disc 9 characterised by U in Figures 4 and 7 for rolling off of at least one revolution.

Figures 6 and 7 show the adjacently lying cam discs 8, 9 individually. Obviously the cam disc 8 has substantially over its entire exterior periphery the middle radius R, in contrast to which the peripheral contour V has a smaller 13 - radius. The cam disc 9 illustrated in Figure 7 has a peripheral contour U with a large radius, a peripheral contour V with a small radius and in the region remaining between these, a contour with the middle radius R.

In Figure 4, both of the cam discs 8, 9 are illustrated superimposed cooperating with the rollers 6.1, 6.2. Correspondingly the pair of cam discs 8, 9 has in an angular region WU the exterior contour U with the largest radius corresponding to the relative rotation of the cam discs 8, 9 to one another in a resulting angular region WV the small radius of contour V. In the angular region lying between these, this pair of cam discs 8, 9 has the middle radius R via which, in accordance with Figure 3, the ductor roller 3 is neither in contact with the ink fountain roller nor in contact with the inking unit roller 4. Figure 5 shows the arrangement of the cam discs 8, 9 rotatable relative to one another in a side view. Illustrated are the rollers 6.1, 6.2 fitted on the ends of the swivel levers 5 and cooperating with the cam discs 8, 9.

The pair of cam discs 8, 9 is driven by an adjusting drive from the printing unit wherein this adjusting drive (phase difference drive) is connected to an adjusting motor operationally connected to a characteristic curve store. By means of the adjustment motor, the rotation of the cam discs 8, 9 relative to one another takes place so that independently of the print speed, the ductor roller is always set against the ink fountain roller 2 for so long that the ductor roller 3 always rolls off against this over at least one revolution. Correspondingly, the angular region WV for the resulting cam section V of the cam discs 14 - 8, 9 is chosen and the cam discs 8, 9 turned relative to one another.

Claims

1. A process for controlling a ductor inking unit of a printing press in which a ductor roller is movable periodically to and fro between an ink fountain roller and an inking unit roller, and is thus brought periodically into contact with the ink fountain roller and with the inking unit roller, and wherein the movement of the ductor roller is controlled so that the length of time of the contact of the ductor roller with the ink fountain roller or of the ductor roller with the inking unit roller, at all printing speeds, is sufficient to enable the ductor roller to roll off against the respective ink fountain or inking unit roller for at least one revolution thereof.

2. A process according to Claim 1 and wherein the contact times of the ductor roller with the ink fountain roller and with the inking unit roller are chosen in such a fashion that the ductor roller experiences the same amount of 20 rolling off against each of these rollers.

3. A process according to Claim 1 or 2 wherein the ink fountain roller is driven with a rotational speed corresponding to the print speed.

4. A process according to Claim 1 or 2 wherein the ink fountain roller is driven with a rotational speed independent of the print speed and the ductor roller, in dependence on the print speed, after its contact with the ink fountain roller and before its contact with the inking unit roller is brought for a preset period of time into a position not in contact with either of these rollers.

5. A process for operating a ductor inking unit in which a ductor roller is moved periodically into contact with an ink fountain roller and an inking unit roller, in each case for an amount of time sufficient to rotate while in such contact at least one revolution, and substantially as hereinbefore described with reference to the accompanying drawings.

6. A ductor inking unit for a printing press comprising an ink fountain roller, a ductor roller and an inking unit roller and drive means for moving the ductor roller to and fro between the ink fountain roller and an inking unit roller, and wherein the drive means for moving the ductor roller is so constructed as to ensure that at all print speeds, contact of the ductor roller with the ink fountain roller and contact of the ductor roller with the inking unit roller occur in each case for a time sufficient for the ductor roller to undergo one revolution.

7. A ductor inking unit according to Claim 6 wherein the ink fountain roller drive is derived from a printing unit to which the ductor inking unit is attached.

8. A ductor inking unit according to Claim 6 and including independent drive means for driving the ink fountain roller in rotation at a preset rotational speed value independently of the print speed.

9. A ductor inking unit according to Claim 8 and wherein the drive means for moving the ductor roller to and fro includes two cam discs rotatable relative to one other, means for the exterior contours of the cam discs, and at least one swivel lever between the roller(s) resting on the cam discs and the ductor roller.

10. A ductor inking unit according to Claim 9 and including an adjustment drive drivable from a printing unit and adapted to adjust the cam discs relative to one another rotationally.

11. A ductor inking unit according to Claim 9 or 10 and wherein one of the cam discs has a standard radius and a peripheral contour with a section of relatively smaller radius, and the other of the cam discs has the same standard radius and a peripheral contour with sections of a relatively larger radius and of relatively smaller radius.

12. A ductor inking unit for a printing press substantially as hereinbefore described with reference to the accompanying drawings.