EP0623468B1 - Ductor inking device and method for controlling ink supply in printing presses - Google Patents

Abstract

In a ductor inking device for printing presses, in particular sheet-fed offset printing presses, an ink application on the printing carrier which develops at a low printing speed is to be prevented from decreasing when the printing speed is increased, in particular to very high speeds. Provision is made for the ink fountain roller (1) to be driven at a constant rotary speed for all printing speeds and for the ductor roller (3) to be engaged increasingly against the ink fountain roller as a function of the printing speed and for the duration of said printing speed. <IMAGE>

Description

The invention relates to a method for adjusting the amount of ink in lifter inking units of printing presses, in particular sheetfed offset printing presses according to the preamble of claim 1 and a correspondingly designed lifter inking unit, according to the preamble of claim 6, in which the method can be used.

In the case of sheet-fed offset printing machines, the ink to be printed has been supplied almost exclusively via lifter inking units for a long time. Such siphon inking units have an ink fountain roller which interacts with an ink fountain and metering devices (ink metering elements or divided or undivided ink knives), on the surface of which the ink to be printed is applied in the form of a layer of adjustable thickness. Due to the dosing elements on the ink fountain, the ink layer thickness on the ink fountain roller can be set differently across the printing direction according to the ink requirements of the printing form. An intermittent siphon roller removes a certain length of ink strip from the ink fountain roller due to occasional contact with the ink fountain roller and transfers this amount of ink to this ink roller in the event of subsequent contact with another ink roller. This ink roller is usually designed as a friction roller and carries out corresponding traversing movements of adjustable stroke and / or frequency. Further ink rollers following this friction roller cause the feed rollers fed through the lifting roller to split several times Ink quantity and by the inking rollers a corresponding inking of the printing areas of the printing form located on the plate cylinder.

The intermittent lifter roller is rotatably supported on its two journals in a pivotable bearing lever, these bearing levers being coupled to a cam roller drive, by means of which the intermittent, that is, the oscillating movement of the lifter roller between the ink fountain and the friction roller results. The cam of the lifter roller drive is directly reduced by the printing unit (e.g. 3: 1), so that based on a corresponding number of revolutions of the plate cylinder (e.g. 3) there is a reciprocating movement of the lifter roller between the ink fountain roller and the distributor roller (lifting stroke).

The ink fountain roller can have a mechanical or else controllable electrical drive derived from the printing unit drive. By appropriately designing this drive, the ink fountain roller is driven step by step or continuously, whereby, as is known from the prior art, in both cases the speed - in the case of the step-by-step drive also the step frequency - is coupled with the machine speed (printing speed) .

Such ink fountain roller drives are described, for example, in US Pat. No. 4,007,683, EP 0 518 234 A1, EP 0 264 838 B1. So that the width of the ink fountain roller can be supplied with increased and reduced ink at all printing speeds, depending on the needs, in the event of a drive of the ink fountain roller coupled to the printing press speed, the contact angle (contact time) of the lifting roller on the ink fountain roller (lifting strip width) is changed, which by a Appropriate training of the cam for the jack roller drive is achieved by means of adjustable control levels. Instead of a cam disc with adjustable control levels for the jack roller drive the ink fountain roller coupled with its own drive (electric motor) can also be increased or decreased in speed for the same purpose, so that there is also an increase or decrease in the width of the squeegee strip. In this case, which is used in the prior art, the speed of the ink fountain roller is not only determined directly by the speed of the printing press, but is also to be increased or decreased, for example from a control station, at the respective printing press speed in order to achieve an intended lifting strip width. The characteristic curve by means of which the drive speed of the ink fountain roller is coupled to the printing press speed is therefore changed. When adjusting the lift strip by means of a variable cam disc, the speed of the ink fountain roller is only coupled to the speed of the printing press by means of an unchangeable characteristic curve.

If the ink fountain roller of a printing press is driven by means of a switch drive, as is known, for example, from EP 0 264 838 B1, the lifting strip width results from the corresponding setting of the step width of the ink fountain roller. The drive of the lifting roller and the corresponding switching drive for the ink fountain roller work in such a phase that the rotation of the ink fountain roller takes place in the phase of contact with the lifting roller.

After the press has been set up, the ink guide is adjusted in accordance with predetermined target specifications, as a rule at a lower printing speed (for example 5,000 sheets / h) than the subsequent production. The production speeds of the high-speed sheet-fed offset printing presses known today can be 15,000 sheets / h and more. With this procedure, typical in printing practice, it is always found that a coloration set at a low machine speed changes when the printing speed is subsequently increased (for example 15,000 sheets / h) changed that the color densities determined on the print sheet on a print control strip but also in the image decrease overall. The printed sheets produced when tuning at a low printing speed thus have a higher color density than those which are then produced at the actual production speed. Color density changes in the range of a few 0.1 color density units are typical. Here and further, this effect, which can be observed particularly in the case of very high-speed sheet-fed offset printing machines, is referred to as color drop. Even very complex changes in the inking unit structure, which have often been carried out in the past, could not remedy this. The reverse effect - increased coloration - occurs when the printing speed is reduced.

GB-A-2 193 926 discloses a lifter inking unit for a printing press, in which a roller (ink fountain roller) interacting with a ink reservoir and a downstream lifter roller each have their own controllable drive. A controller influencing the movement of the rollers is connected to a sensor for detecting the printing speed.

From US-A-2 223 945 a lifter inking unit for printing machines is known, in which an ink fountain roller is connected to two further rollers and each of these rollers is assigned a lifter roller which performs an intermittent movement. The lifter rollers perform movements that are out of phase with each other and transfer the ink film to downstream inking unit rollers.

GB-A-1 024 211 describes a lifter inking unit for a printing press, in which the ink fountain roller and the downstream lifter have their own drive. The ink fountain roller rotates at a peripheral speed regardless of the printing speed. A controller is provided which processes pulses corresponding to the printing speed.

The object of the present invention is therefore to design a method for adjusting the amount of ink in lifter inking units of printing machines in accordance with the preamble of claim 1 and a suitably designed lifter inking unit for carrying out the method in accordance with the preamble of claim 6 in such a way that a change in the ink layer thickness application on the printing material when Changing the printing speed is counteracted.

This task is solved by the characteristic features of the respective method or device claim. Further developments of the invention result from the corresponding dependent claims.

According to the invention, a complete departure from the conventional way of adjusting the amount of ink in a lifter inking unit of printing machines, in particular sheet-fed offset printing machines, is thus provided. So it is no longer the speed or step frequency of the ink fountain roller coupled to the speed of the printing unit, but it is provided according to the invention that the speed or step frequency of the ink fountain roller, which has its own controllable drive, at all Printing unit speeds is kept at a constant value. So that depending on the printing speed, more or less ink is nevertheless conveyed from the ink fountain via the ink fountain roller in the direction of the printing plate, it is provided according to the invention that the contact angle of the lifting roller on the ink fountain roller is changed depending on the printing unit speed. This is carried out in such a way that when the printing unit speed (number of sheets per hour) is doubled, the contact angle of the lifting roller, based on one machine revolution or on one lifting cycle interval during unwinding on the ink fountain roller driven at constant speed, is also doubled. Because of the longer contact angle of the lifter roller on the ink fountain roller, at higher printing speeds, a larger amount of ink corresponding to the printing speed is transported to the rest of the inking unit, in that the width of the lifter strip always remains the same, but the lifter driven at the machine speed (for example 1: 3) is correspondingly more frequently delivered to the Ink fountain roller is started.

The present invention makes use of the knowledge that the colors used in offset printing technology have pronounced non-Newtonian properties and therefore, because of the drive of the ink fountain roller at a speed independent of the printing speed, there are always the same - regardless of the printing speed - color properties.

According to the invention it is provided that the contact angle of the lifter roller on the ink fountain roller is chosen to take off a corresponding amount of ink as a function of the printing or machine speed. A simple linear characteristic curve can be provided here, which shows the dependence of the required system time as a function of the respective printing unit speed. The characteristic curve mentioned can be determined theoretically and / or empirically. A characteristic curve can also be provided which has non-linear properties at least in sections.

As already mentioned above, an essential feature of the present invention is that the speed of the ink fountain roller is kept at a constant value by its own drive regardless of the printing unit speed. This speed value of the ink fountain roller itself can, however, be set by the printer, for example from the control station, so that the lifting strip removed from the lifting roller can be increased or decreased by a somewhat higher or a somewhat lower speed value of the ink fountain roller at all printing unit speeds.

According to a development of the invention, it is provided that the change in the contact angle of the lifter roller on the ink fountain roller is initiated a certain number of machine revolutions (angular degrees) before the change in the printing speed. If, for example, the command to increase the printing speed from 5,000 B / h to 15,000 B / h is entered on a control panel, the contact angle of the lifting roller with respect to the ink fountain roller is first changed from the value provided for 15,000 B / h to the for after a predetermined time ramp 15,000 B / h ramped up. The machine is then ramped up by 5,000 b / h to 15,000 d / h with a certain number of machine revolutions. A corresponding procedure is followed when the printing press speed is reduced, i.e. First, after entering a corresponding command, the system angle is reduced in accordance with a predetermined time law and, after a certain number of machine revolutions, the printing machine speed is increased and decreased.

The number of machine revolutions by which the initiation of the speed change is initiated in relation to the change in the system angle of the jack is determined from the lifting stroke of the printing press, the geometry of the inking unit and the printing unit. For this purpose, it is determined by how many revolutions the printing unit or the machine (single-speed shaft) must be rotated until a change in layer thickness on the first friction roller corresponding change in layer thickness on one of the inking rollers. In particular, the inking roller that causes the largest percentage of inking on the printing form or the inking roller that has the shortest and therefore the least number of machine degrees that cause a change in color from the friction roller to the inking roller can be selected here as a reference.

Furthermore, the above-mentioned deceleration in machine rotation or angular degrees takes into account the number of degrees that the printing press executes until a change in coloration on the printing plate comes to rest on the printing sheet, the printing zone.

Furthermore, it is provided that the change in the system angle following the input command for changing the printing speed and the change in printing machine speed which is then delayed to be initiated are always initiated with the same angular position of the lifting gear. This can mean, in particular, that the change in the contact angle is only initiated when the lifting roller bears against the friction roller.

According to one exemplary embodiment of the invention, the intermittent drive of the lifting roller takes place by means of an adjustable pair of cams driven by the printing unit. This intended pair of cams consists of two cams lying side by side, the axes of rotation of which coincide and which are driven together by the printing or inking unit. On the outer contours of these cams, a roller pressed under spring force runs, which is coupled to the one lever arm of the lifter roller bearing and accordingly generates the pendulum movement of the lifter roller.

Instead of a drive for the lifting roller with cam disks that are adjustable relative to one another, it is of course also possible to provide a drive of a different design, by means of which it is possible to determine the contact angle of the lifting roller on the ink fountain roller to change as a function of printing speed while the machine is running.

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

Fig. 1

schematisch das erfindungsgemäße Heberfarbwerk,

Fig. 2

eine Kennlinie für den Antrieb der Farbkastenwalze,

Fig. 3

eine Kennlinie, nach welcher der Anlagewinkel der Heberwalze gegenüber der Farbkastenwalze als Funktion der Druckgeschwindigkeit gesteuert wird,

Fig. 4

das Prinzip des verstellbaren Heberwalzenantriebs,

Fig. 5-8

eine weitere erfindungsgemäße Kurvensteuerung, und

Fig. 9

der Zusammenhang zwischen Veränderung der Maschinengeschwindigkeit und dem Heberanlagewinkel.

It shows:

Fig. 1

schematically the lifter inking unit according to the invention,

Fig. 2

a characteristic curve for the drive of the ink fountain roller,

Fig. 3

a characteristic curve according to which the contact angle of the lifting roller with respect to the ink fountain roller is controlled as a function of the printing speed,

Fig. 4

the principle of the adjustable lifter roller drive,

Fig. 5-8

another curve control according to the invention, and

Fig. 9

the relationship between changing the machine speed and the lifting system angle.

1, an ink fountain roller 1 interacts with an ink fountain 2. The color metering elements attached to the underside of the ink fountain 2 for setting a color profile are not shown.

The ink fountain roller 1 is coupled directly to a motor M with the interposition of a transmission (not shown), the motor M being controlled by an electronic drive A.

2 shows how the speed of the motor M (ordinate) can be regulated to a constant value as a function of the printing speed (abscissa). Since it is provided in accordance with this exemplary embodiment that the ink fountain roller 1 should always have a constant value regardless of the printing speed, the electronic drive A is not coupled to the control of the rest of the printing press, except for increasing or decreasing the speed specification (control station). Higher or lower speed values are shown in dashed lines in FIG. 2 and result in larger or smaller lifter strip widths.

In the transport direction of the ink, the ink fountain roller 1 is followed by a lifting roller 3, which is suspended via its two ends on a pivotable bearing arm 5, which in turn is mounted in a side frame (not shown) of the printing press or the inking unit. At the second end of a bearing arm 5, a roller 6 is attached, which is pressed under the force of a spring 7 against the outer contours of two cams 8, 9 lying next to one another.

The lifter roller 3 is followed in the lifter inking unit according to FIG. 1 by a first friction roller 4, which is in contact with further ink rollers, which are only indicated. By means of the lifter roller drive shown in FIG. 1 with the reference numerals 5, 6, 7, 8, 9, 10, 11, the lifter roller 3 executes an intermittent movement between the ink fountain roller 1 and the friction roller 4. The friction roller 4 can also be designed as a non-changing inking roller or, via an adjustable traversing drive, as a friction roller adjustable in the traversing stroke.

1 and 4, the explanation is given of the jack roller drive 5, 6, 7, 8, 9, 10, 11, which is only shown in principle. The two cams 8, 9 are driven by the printing unit or the inking unit with the interposition of an adjusting gear 10, a reduction gear, not shown, is also provided here. The representation of the cam disks 8, 9 with the adjusting gear 10 according to FIG. 1 is to be understood purely symbolically, whereby in principle, for example, the cam disk 8 (main cam) is driven directly from the printing unit / inking unit and the cam disk 9 (adjusting cam) is rotatable with respect to one another the cam 8 is arranged parallel to this.

Fig. 4 shows the cams 8, 9 with the profile of their outer contours once again individually (Fig. 4, left) and also superimposed (Fig. 4, right). Both cams 8, 9 have a large curve radius on the major part of their circumferential contour U, which merges into the remaining part of the circumferential contour V with a small radius of curvature via two S-shaped transitions. By superimposing the cam disks 8, 9 according to FIGS. 1 and 4, a control cam is thus created, through which the roller 6 runs on the circumferential contour U of the cam disk 8 and / or the cam disk 9 and in the remaining area - depending on the adjustment of the cam disks 8 , 9 to each other (arrow) - on the circumferential contour V. According to the basic illustration in FIG. 1, the common circumferential contour V of the cams 8, 9 is associated with the positioning of the lifting roller 3 on the ink fountain roller 1. The adjustability of the cam disks 8, 9 relative to one another with simultaneous drive from the printing / inking unit via the adjustment gear 10 (phase gear / differential gear) is identified in each case by an arrow in FIGS. 1 and 4. 1 also shows the direction of rotation of the cams 8, 9.

5 to 8 show a further preferred embodiment of the pair of cams 8, 9. In this case, the cams 8, 9 also each have a circumferential contour V with a small radius. As shown in Fig. 6, however, the cam plate 9 in an angular area WU has a circumferential contour U with a larger radius, which indicates the contact angle of the lifting roller 3 the friction roller 4 defined. The cam 8 thus has two radii and the cam 9 has three radii. If the roller 6 runs on the central radius of the cam disks 8, 9, the lifting roller 3 is located between the ink fountain roller 1 and the friction roller 3.

In FIG. 7 the two cams 8, 9 are shown in a superimposed form - corresponds to the situation according to FIG. 4, left - in a top view and in FIG. 8 in a side view. The fact that only the cam plate 9 has the circumferential contour U for the contact of the lifting roller 3 with the friction roller 4 ensures that the contact angle of the lifting roller 3 on the friction roller 4 is independent of the rotation of the cam discs 8, 9. The lifting roller 3 thus always executes the same number of revolutions - or fractions thereof - in contact with the friction roller 4, regardless of the position of the cams 8, 9 relative to one another. 5 to 8, WU and WV respectively denote the contact angle of the lifter roller 3 on the friction roller 4 and the ink fountain roller 1, based on one revolution of the cam disks 8, 9. In particular, from FIG. 7 it can be seen that in this embodiment, by turning the cams 8, 9 relative to one another, the contact angle WV of the lifting roller 3 with respect to the ink fountain roller 1 is variable, whereas the contact angle WU of the lifting roller 3 on the friction roller 4 always remains constant.

1 is actuated by a servomotor 11, so that the corresponding rotation of the cam disks 8, 9 takes place in a motorized manner relative to one another. The servomotor 11 receives its actuating signals from a controller S and furthermore, via an indicated signal line, information about the printing speed (printing unit speed), for example in the form of a speedometer signal or a pulse train proportional to the printing speed. The control S is assigned a characteristic curve memory K, in which the rotation of the cam disks 8 to be effected by the servomotor 11 via the adjusting gear 10, 9 are stored relative to one another as ordinate values over the printing speed as the abscissa (FIG. 3).

As already indicated, FIG. 3 shows in the form of a characteristic curve the relationship according to the invention of the rotation of the cam disks 8, 9 to be carried out by the servomotor 11 relative to one another as a function of the printing speed (abscissa). Since ultimately the rotation of the cams 8, 9 relative to one another according to the gear arrangement according to FIG. 1 changes the contact angle of the lifting roller 3 with respect to the ink fountain roller 1, that is to say also increases or decreases the circumferential contour V (circumferential contour U decreases or increases accordingly) 3, the characteristic curve according to FIG. 3 likewise shows the relationship of the contact angle of the lifting roller 3 on the ink fountain roller 1 (ordinate) as a function of the printing speed plotted on the abscissa (corresponding scaling of the ordinate).

9 shows the course of the contact angle WV of the lifting roller 3 with respect to the ink fountain roller 1 as a function of the machine angle MW and the machine speed MG as a function of the machine angle MW in two diagrams lying one above the other. In this exemplary embodiment it is assumed that the command for increasing the machine speed MG from the value MG1 to MG2 was entered at the time W1 of the machine angle MW. At a point in time W2 of the machine angle, for example when the lifting roller 3 is set against the friction roller 4, the contact angle WV is raised from a value WV1 corresponding to the current printing speed to the final value WV2 according to a predetermined time law. The increase in the machine speed MG from the initial value MG1 to the intended final value MG2 is initiated only at the time W3 of the machine angle MW. In relation to the machine angle MW, the machine speed MG is ramped up and the angle value W3-W1 is delayed at the time W1 which was given the command to increase the machine speed MG.

In the exemplary embodiment of FIG. 9, the ramping up of the machine speed MG from a value MG1 to a final value MG2 and the corresponding change in the contact angle WV of the lifting roller 3 with respect to the ink fountain roller 1 from a value WV1 to a value WV2 were described. Accordingly, the machine speed MG is reduced from a higher initial value to a lower final value. Here, too, the change in the contact angle WV of the lifting roller 3 with respect to the ink fountain roller 1 is always triggered to the same switching state of the lifting roller 3. Then, according to the contact angle WV of the lifting roller 3 with respect to the ink fountain roller 1, the starting value is changed to the corresponding one after a predetermined time ramp Shut down the final value, and - with a delay in relation to the machine angle MW - the machine speed MG is shut down.

Reference list

1

Ink fountain roller

2nd

Paint box

3rd

Lifter roller

4th

Grater roller

5

Bearing arm

6

role

7

feather

8th

Cam

9

Cam

10th

Variable speed gear

11

Servomotor

M

engine

A

Drive (motor M)

S

Control (servomotor 11)

K

Characteristic curve memory

U

Circumferential contour (lifter roller 3 on friction roller 4)

V

Circumferential contour (lifter roller 3 on ink fountain roller 1)

WU

Angle of contact (lifter roller 3 on friction roller 4)

WV

Contact angle (lifting roller 3 on ink fountain roller 1)

MG

Machine speed

MW

Machine angle

Claims (10)

1. Process for ink quantity adjustment on ductor inking units of printing presses with an ink fountain roller (1) rotating independently of the printing speed (MG), wherein an ink film on the ink fountain roller (1) is transferred by means of a timed contact of a ductor roller (3) from the ink fountain roller (1) on to a first inking unit roller (4) arranged after the ductor roller (3), and the contact of the ductor roller (3) is controlled according to guidelines, characterised in that the ink fountain roller (1) is driven at all printing speeds in accordance with a movement law which remains the same in time and that the contact angle (WV) of the ductor roller (3) against the ink fountain roller (1) is controlled corresponding to a characteristic curve reproducing the relationship of contact angle (WV) and print speed (MG).
2. Process according to Claim 1, characterised in that the ink fountain roller (1) at all printing speeds (MG) is driven with continuous peripheral speed at a constant rotational speed or stepwise with a constant stepping frequency and speed of rotation during the stepping phase.
3. Process according to Claim 1 or 2, characterised in that the rotational speed of the ink fountain roller (1) is adjusted corresponding to the ink requirements.
4. Process according to one of the preceding Claims, characterised in that the contact angle (WV) of the ductor roller (3) against the ink fountain roller (1) is changed in accordance with a characteristic curve reproducing the dependence on the print speed (MG) as a linear function.
5. Process according to one of the preceding Claims, characterised in that after a command effecting a change of the print speed (MG), after the ductor roller (3) has taken up a predetermined position with respect to the ink fountain and the first of the ink fountain rollers arranged subsequent to the ductor roller (1, 4), first a change of the contact angle (WV) of the ductor roller (3) with reference to the ink fountain roller (1) is introduced from the value corresponding to the then printing speed (MG) to the value coordinated to the printing speed (MG) provided in accordance with the characteristic curve, and that after a determined press angle (MW), the intended change of the printing speed (MG) is carried out.
6. Ductor inking unit for a printing press for applying the process according to one of Claims 1 to 5 in which an ink fountain roller (1) cooperating with an ink fountain (2) can be driven via motor (M) independently of the printing speed (MG) and an intermittent ductor roller (3) is arranged with a ductor roller drive downstream which has a control (S) which senses the printing speed, characterised in that arranged relative to the control (S) sensing the printing speed (MG) for the ductor roller drive (5, 6, 7, 8, 9, 10, 11) is a characteristic curve store (K) in which the dependence of the contact angle (WV) of the ductor roller (3) against the ink fountain roller (1) is stored as a function of the printing speed (MG) and via the ductor roller drive (5, 6, 7, 8, 9, 10, 11), the contact angle (WV) of the ductor roller (3) against the ink fountain roller (1) is changed in dependence on the printing speed (MG) corresponding to this characteristic curve (K).
7. Ductor inking unit according to Claim 6, characterised in that the ductor roller drive (5, 6, 7, 8, 9, 10, 11) has two cam discs rotatable relative to one another on the outer contour (U, V) of which runs a roller (6) coupled to the ductor roller (3), and the cam discs (8, 9) can be driven from the printing unit by an adjustment drive (10) and via an adjusting motor (11) connected via the adjustment drive (10) by the control (S) can be rotated relatively to one another corresponding to the data deposited in the characteristic curve store (K).
8. Ductor inking unit according to Claim 7, characterised in that one of the cam discs (8, 9) has in one angular region the peripheral contour (V) for contacting the ductor roller (3) against the ink fountain roller (1).
9. Ductor inking unit according to one of Claims 6 to 8, characterised in that the ink fountain roller (1) can be driven with a constant rotational speed by the motor (M) and the drive (A) and/or stepwise with a predetermined frequency as well as rotational speed during the stepping phase.
10. Ductor inking unit according to one of Claims 6 to 9, characterised in that differing rotational speeds can be predetermined for the drive (A) of the motor (M) of the ink fountain roller (1).

Images