EP1531043B1 - Process and device for moving a doctor blade - Google Patents

Description

The invention relates to a method for displacing a doctor blade mounted on a cylinder of a printing press in the direction of the longitudinal axis of the doctor blade, in which the displacement movement of the doctor blade is subdivided in time into movement and standstill sections, as well as a device for carrying out the method.

In printing machines doctor blade doctor devices are generally used to doctor off the surface of a rotating cylinder, for example the printing cylinder, with the aid of a doctor blade. For example, such a squeegee device in a gravure printing machine has the function of smoothly doctoring off the smoothed surface of the gravure cylinder after inking and before the actual printing so that the ink remains only in the printing, recessed areas of the printing cylinder surface.

In conventional printing presses, the doctor blades are usually made of thin steel sheet of hardened or unhardened spring steel. An employed on the surface of the printing cylinder or the anilox cutting edge of a doctor blade is subject to significant wear. In order to increase the service life of the doctor blade, the doctor blade is set in an oscillation in its longitudinal direction, so that the wear of the doctor blade is distributed as possible. The frequency of such oscillation may be, for example, 1 Hz or more depending on the production speed, and the stroke of the oscillation may be, for example, up to 40 mm. Although the wear of the doctor blade is distributed locally by an oscillation of the doctor blade, it is still relatively often necessary to replace a worn doctor blade. This requires a standstill of the printing press.

To further reduce the wear of the doctor blade, doctor blades are used, which are ceramized on their wear side facing the pressure cylinder. The life of the doctor blade is thereby increased by a multiple.

From the European Patent Application EP 1 362 696 It is known to the Applicant to vibrate the doctor blade at a frequency which is in the acoustic range or in the ultrasound range. This measure serves to dissolve impurities from the gravure cylinder. The stroke of the vibration movement can be less than 0.2 mm.

Although on the one hand a lateral oscillation of the doctor blade is desired to reduce uneven wear of the doctor blade, but the oscillation can also adversely affect the printed image, as can result from differences in speed of the doctor blade slightly different amounts of ink in the wells of the printing cylinder to Differences in ink application lead to the substrate web. In particular, the difference between a region where the doctor blade moves at a uniform speed and a region where reversal of the direction of movement of the doctor blade takes place can be detected on the printed image. Since the frequency of the oscillation of the doctor blade is often coupled to the rotational speed of the printing cylinder, for example, in a quality multi-color printing, the course of movement of the different doctor blades is designed differently so that the deviations of the individual colors do not add up. Nevertheless, with particularly high-quality multicolor printing, the different speeds occurring during the oscillation of the doctor blade can be achieved. Directions of movement and turns negatively affect the printed image

From the FR 1 396 328 it is known to superimpose an oscillation with the oscillation movement of the doctor blade an oscillation with a multiple of the period, so that the reversal points of the first oscillation movement vary periodically. However, it still comes at different speeds of the doctor blade to standstill at the reversal points.

From the 749 890 a printing machine is known in which the doctor blade speed during the doctoring of the etching on the forme cylinder is either uniform or zero. A deviating movement of the doctor blade takes place after each squeegee period in the pressure gap. In machines with a gripper cylinder, which is twice as large as the forme cylinder, in particular the time of the idle rotation of the cylinder is available for this movement.

The object of the invention is to provide a method for moving an employee employed on a cylinder doctor blade, with the highest possible print quality can be achieved with uniform and minimal wear of the doctor blade as well as to create a printing machine for performing the method.

This object is achieved by a method of the type mentioned, in which the duration of the stoppage sections predominates during the printing operation and in which the movement sections are each in operating phases in which committee is printed. Furthermore, this object is achieved by a printing machine according to claim 4. The displacement speed of the doctor blade is therefore equal to zero during the predominant duration of the printing operation.

The specified for the vast duration of the printing operation shift speed may apply in particular for periods corresponding to a time proportion of 90%, in particular 99% of the duration of the printing operation.

If the doctor blade is stationary during the majority of the printing operation, negative effects of the movement of the doctor blade on the print quality can be significantly reduced compared to a conventional, faster oscillation of the doctor blade. The smaller a non-zero displacement speed, the less the displacement effect on the printed image. Nevertheless, it is achieved with an intervalwise displacement movement that the doctor blade is shifted over time by a stroke of several millimeters, so that the wear of the doctor blade is distributed over the stroke length.

The invention combines the avoidance of uneven wear of the doctor blade with the possibility of a particularly high print quality, since during the standstill of the doctor blade results in a particularly uniform application of ink to the substrate.

The displacement movement of the doctor blade is temporally divided into motion and standstill sections, and during the printing operation outweighs the duration of the stoppage sections. In particular, the duration of the movement sections may be less than 10 percent of the duration of the downtime sections, preferably less than 1 percent. It can also be much lower. The duration of the standstill sections is preferably to be chosen so that there is no perceptible uneven wear of the doctor blade during standstill of the doctor blade. In this embodiment, the uniformity and thus the quality of the printed image during the standstill of the doctor blade is particularly high.

In a printing machine, in which the printing material is withdrawn from a roll and / or wound onto a roll, it is known that a roll change leads to temporary production of waste during the current printing operation. This is the case, for example, when a splice of the printing material web produced during an automatic reel change runs through the printing unit or when a web section is printed which must later be severed during an automatic change of the take-up reel. Preferably, therefore, in the method according to the invention, the movement sections during the movement of the doctor blade are selected in time so that they coincide with the production of rejects. The disturbances of the printed image, which are caused by the movement of the doctor blade, then do not affect the quality of the printed result, since they are eliminated together with the already incurred committee.

Advantageous embodiments of the invention will become apparent from the dependent claims.

The displacement movement of the doctor blade is preferably synchronized automatically with the role change processes.

The sliding movement can be a vibration movement with a frequency of at least 1 Hz, in particular at least 5 Hz, superimposed. This vibration movement may also be an acoustic oscillation or an ultrasonic oscillation. The vibratory movement is preferably carried out in the direction of the longitudinal axis of the doctor blade. On the one hand, it serves to remove impurities from the recesses of the cylinder to remove or detach from the doctor blade, as in the European patent application EP 1 362 696 the applicant is described. The movements of the doctor blade occurring during the vibration do not count as part of the "displacement movement" in the sense of the invention, and the standstill specified in claim 1 relates only to the pure displacement movement without consideration of the vibration.

Claim 4 is a printing machine with a doctor device which comprises a doctor blade engageable against a cylinder and a displacement device for displacing the doctor blade in the direction of the longitudinal axis of the doctor blade, wherein the displacement device is adapted to a method for moving the doctor blade attached to the cylinder To carry out according to claim 1. The displacement device can be designed to execute the method semi-automatically or fully automatically. The printing press has the advantages indicated in the description of the method.

In a preferred embodiment, the squeegee device of the printing machine comprises an oscillator for generating a vibratory movement of the doctor blade, and the displacement device and the oscillator are adapted to carry out a method according to claim 1, in which the displacement movement is a vibratory movement with a frequency of at least 1 Hz, in particular at least 5 Hz, is superimposed.

In a particularly preferred embodiment of the printing press, the doctor blade is ceramized on its wear side. This allows during the sliding movement of the doctor blade a long duration of a standstill section, without causing uneven wear of the doctor blade.

In the following preferred embodiments of the invention will be explained with reference to the drawing.

Figur 1

eine schematische Ansicht einer Tiefdruckmaschine;

Figur 2

einen schematischen Schnitt längs der Linie II - II in Figur 1;

Figur 3

eine schematische Teilansicht der Tiefdruckmaschine mit einem Aufwickler;

Figur 4

ein schematisches Diagramm einer Verschiebebewegung mit Bewegungs- und Stillstandsabschnitten;

Figur 5

ein schematisches Diagramm einer periodischen Hin- und Herbewegung;

Figur 6

eine schematische Ansicht einer Tiefdruckmaschine mit einer Rakelvorrichtung mit einem Oszillator; und

Figur 7

ein schematisches Diagramm von Abschnitten einer periodischen Hin- und Herbewegung, der eine Vibrationsbewegung überlagert ist.

Show it:

FIG. 1

a schematic view of a gravure printing machine;

FIG. 2

a schematic section along the line II - II in FIG. 1 ;

FIG. 3

a schematic partial view of the gravure printing machine with a winder;

FIG. 4

a schematic diagram of a sliding movement with movement and standstill sections;

FIG. 5

a schematic diagram of a periodic reciprocation;

FIG. 6

a schematic view of a gravure printing machine with a doctor device with an oscillator; and

FIG. 7

a schematic diagram of sections of a periodic reciprocation, which is superimposed on a vibrational movement.

In the FIG. 1 The gravure printing press shown comprises a gravure cylinder 10, an applicator roller 12 and a impression roller 14, which are rotatably mounted between side parts 16, 18 of a machine frame. Associated drive and control devices have not been shown here, as they are not essential to the understanding of the invention.

The applicator roller 12 is at its upper apex with the gravure cylinder 10 in contact and immersed with its lower apex in a paint tray 20, as more clearly in FIG. 2 can be seen. The application roller 12 thus absorbs ink from the ink tray 20 and transmits it to the peripheral surface of the gravure cylinder 10, in the direction of arrow in FIG. 2 rotates and transfers the ink to a substrate web 22, which is between the impression roller 14th and passes through the gravure cylinder and is pressed by the impression roller against the gravure cylinder.

The gravure cylinder 10 is associated with a doctor device 24. This doctor device is formed in a known manner by a doctor blade 26 which is attached to a holder 28. The holder is mounted on a shaft 30 which extends between two levers 32, 34. The lower ends of the levers 32, 34 sit on a rotatable shaft 36, with which the entire doctor device 24 can pivot against the circumference of the gravure cylinder so that its surface is doctored off with the cutting edge of the doctor blade 26. In this way, the ink absorbed by application roller 12 is removed from the smooth, non-ducking surface areas of the gravure cylinder 10, so that the ink remains only in the recessed areas that produce the printed image on the substrate web 22.

On the lever 34, a displacement device 38 is arranged, with which the holder 28 and thus the doctor blade 26 in the direction of the longitudinal axis of the doctor blade relative to the levers 32, 34 can be moved, as indicated by a double arrow in FIG. 1 is hinted at. The displacement device 38 thus forms a transverse thrust device which generates a movement of the cutting edge of the doctor blade 26 relative to the gravure cylinder 10 in the direction transverse to the direction of the printing material web 22, ie in the axial direction of the gravure cylinder. Instead of the displacement device 38 may also be provided a displacement device which shifts the entire doctor device 24 together with the levers 32, 34 in the direction indicated.

FIG. 2 shows on the underside of the doctor blade 26, a ceramic layer 40, through which the wear of the doctor blade 26 is reduced by the contact with the rotating gravure cylinder 10.

FIG. 3 shows that the printing material web 22 is wound on a Aufwikkelrolle 46 after printing in the gravure press on pulleys 42 and a dancer roller 44. A full take-up roll can be replaced in a known manner automatically or manually by a new roll 48, which then forms the interior of the next take-up roll. The storage of the pulleys 42 and the take-up roll 46 and associated facilities of the winder have not been shown here, as they are for the understanding of Invention are not essential.

In the FIGS. 4 and 5 Two different displacement movements of the doctor blade 26 are sketched, which can be effected by the displacement device 38 of the doctor device 24. The displacement movement takes place in each case in the direction of the longitudinal axis of the doctor blade. In each case, a position of the doctor blade 26 which varies over time in the direction of the displacement movement is indicated. In order to make clear differences between the various displacement movements, the diagrams of FIG FIGS. 4 and 5 and the one described below FIG. 7 not shown in proportion to each other.

FIG. 4 illustrates a sliding movement of the doctor blade 26, which is temporally divided into movement sections 50 and stoppage sections 52. The duration of the stationary sections 52 is at least 100 times the duration of the movement sections 50. During a movement section 50, the doctor blade 26 is displaced by a specific amount in the direction of the longitudinal axis of the doctor blade. In FIG. 4 two movement sections 50 are shown in which the doctor blade 26 in each case in the same direction and by the same amount, for example 1 mm, is moved. After the doctor blade 26 has been displaced to a predetermined position during a plurality of movement sections 50, a reversal of the direction of movement takes place. In this case, the amount by which the doctor blade is moved during the further movement sections can be varied.

Notwithstanding the in FIG. 4 In the example shown, a variation of the amount by which the doctor blade is displaced during a movement section 50 can also take place while maintaining the direction of movement. In order to ensure the highest possible uniformity of the wear of the doctor blade 26, it is advantageous to vary the amounts by which the doctor blade is displaced so that a position once occupied by the doctor blade is taken up again only after the longest possible time.

The movement portions 50 coincide with the time when the take-up roll 46 is changed. During the stoppage sections 52 a Aufwikkelrolle 46 is wound in each case. A sensor, not shown, detects the radius of the roll on the take-up roll 46 and solves when a roll change is required, the Movement section 50 off. The actual roll change is then triggered with such a time delay that the printing material web is cut when reel change approximately at the point that was printed at the time of the movement section 50. If an impairment of the printed image is effected by the movement of the doctor blade 26, the defect is thus in a portion of the printing material, which forms the end of the old take-up roll or the beginning of the new take-up roll and is later removed as a scrap anyway.

FIG. 5 illustrates the sliding movement according to another embodiment. The displacement movement here is a periodic back and forth movement with a period of one hour. The stroke of the oscillation is for example ± 20 mm. The displacement speed of the doctor blade 26 is therefore in the range of 0 to 0.04 mm / s. This very low displacement speed affects the printed image at most to a very small extent. Other forms of oscillation are conceivable, for example a triangular oscillation.

A further improvement of the printed image is achieved by a vibrating movement explained below, which is superimposed on the displacement movement of the doctor blade 26.

FIG. 6 shows one opposite FIG. 1 modified gravure printing machine in which on the shaft 30 between the displacement device 38 and the holder 28, an oscillator 54 is inserted, the holder 28 and thus the doctor blade 26 in high-frequency oscillations in the direction parallel to the axis of the gravure cylinder 10, ie parallel to the direction of displacement of the doctor blade 26, offset. The oscillator 54 thus forms a further transverse thrust device, which generates a vibratory movement of the cutting edge of the doctor blade 26, which is superimposed on the displacement movement. The frequency of the vibratory motion is in the ultrasonic range, so that the vibratory vibrations of the doctor blade 26 are in the form of traveling ultrasonic waves which propagate to the opposite end of the doctor blade and are absorbed there by a damper 56 inserted between the lever 32 and the holder 28.

However, the frequency can also be significantly lower, and the oscillator 54 may be, for example, an acoustic vibrator. Also an even lower one Frequency of the vibration movement is conceivable. The stroke of the vibration movement can be very small, for example, it can be less than 0.2 mm.

FIG. 7 illustrates two portions of a sliding movement of the doctor blade 26 according to FIG. 5 which is superimposed on a vibratory motion. In a section 58 of the sliding movement, the center position of the doctor blade 26 gradually changes, while the doctor blade 26 performs a vibration with a much smaller stroke around the middle position. In a second section 60, a direction reversal of the displacement movement takes place. The superimposed vibration movement causes here that even at the reversal point of the sliding movement no temporary stoppage of the doctor blade 26 results. By the in FIG. 7 shown superimposed vibration movement is opposite to in FIG. 5 shown displacement movement without superimposed vibration movement a further increase in print quality or, for the same quality, a higher displacement speed of the doctor blade possible.

The embodiments shown each relate to a gravure printing machine. However, the invention is applicable not only to gravure printing machines but also to other printing machines.

Claims (7)

1. Method for displacing a doctor blade (26) which is positioned on a cylinder (10) of a printing press in the direction of the longitudinal axis of the doctor blade (26), wherein the displacement movement of the doctor blade (26) is sub-divided in terms of time into movement portions (50) and idle portions (52), characterised in that, during the printing operation, the duration of the idle portions (52) predominates and in that the movement portions (50) are each in operating phases during which reject material is printed.
2. Method according to claim 1, characterised in that a vibration movement having a frequency of at least 1 Hz, in particular at least 5 Hz, is superimposed on the displacement movement.
3. Method according to claim 2, characterised in that the vibration movement is carried out in the direction of the longitudinal axis of the doctor blade (26).
4. Printing press having a doctor device (24) which has a doctor blade (26) which can be positioned against a cylinder (10) and a displacement device (38) for displacing the doctor blade (26) in the direction of the longitudinal axis of the doctor blade (26), which displacement device (38) is constructed so as to bring about a displacement movement of the doctor blade (26) which is sub-divided in terms of time into movement portions (50) and idle portions (52), characterised in that the displacement device (38) is constructed so as to bring about the displacement movement in such a manner that, during the printing operation, the duration of the idle portions (52) predominates and that the movement portions (50) are each in operating phases during which reject material is printed.
5. Printing press according to claim 4, characterised in that the doctor device (24) has an oscillator (54) for producing a vibration movement of the doctor blade (26) and the displacement device (38) and the oscillator (54) are constructed so as to bring about the displacement movement and the vibration movement of the doctor blade (26) in such a manner that the vibration movement is superimposed on the displacement movement and has a frequency of at least 1 Hz, in particular at least 5 Hz.
6. Printing press according to claim 5, characterised in that the displacement movement (38) and the oscillator (54) are constructed so as to bring about the displacement movement and the vibration movement of the doctor blade (26) in such a manner that the vibration movement is carried out in the direction of the longitudinal axis of the doctor blade (26).
7. Printing press according to any one of claims 4 to 6, characterised in that the doctor blade (26) is ceramicised on the wear side thereof.

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