EP1717026A2 - Process and device for moving a doctor blade - Google Patents

Abstract

The method involves shifting a doctoring device (26) such that the shifting velocity of the doctoring device is within the range of 0-0.1 meter/second during a predominant period of a printing operation. The doctoring device is fixed at a retainer. The shifting movement superimposes a vibration movement with a frequency of 1 Hertz, where the vibration movement is achieved in the direction of longitudinal axis of the doctoring device. An independent claim is also included for a printing machine with a doctor roller.

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, wherein the displacement movement of the doctor blade is such that during the predominant duration of the printing operation, the displacement speed of the doctor blade in the range of zero to 0, 1 m / s, in particular from zero to 0.01 m / s, and a printing machine 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.

In order to further reduce the wear of the doctor blade, doctor blades are used, which on their side facing the pressure cylinder wear side are ceramized. 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. In the case of particularly high-quality multicolor printing, however, the different speeds, directions of movement and turns occurring during the oscillation of the doctor blades can negatively influence 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 DE 749 890 For example, a printing machine is known in which the doctor speed is either uniform or zero during the doctoring of the etching on the forme cylinder. A deviating movement of the doctor takes place with each cylinder revolution in the pressure gap. At the high However, speeds of modern printing machines, this is not technically feasible.

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 above, in which the displacement movement is a vibratory movement with a frequency of at least 1 Hz, in particular at least 5 Hz, superimposed. Furthermore, this object is achieved by a printing machine according to claim 5.

Preferably, the displacement speed of the doctor blade during the majority of the printing operation in the range of zero to 1 mm / s, more preferably in the range of zero to 0.1 mm / s, in particular in the range of zero to 0.01 mm / s.

The shift speeds specified for the predominant duration of the printing operation can apply in particular for periods which correspond to a time proportion of 90%, in particular also 99% of the duration of the printing operation.

If, during the majority of the printing operation, the doctor blade is displaced or even stopped at a low translating speed, negative effects of the movement of the doctor blade on print quality can be significantly reduced as 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 a longer-lasting, slow displacement movement of the doctor blade or at 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 spreads 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 standstill or the very slow movement of the doctor blade results in a particularly uniform application of ink to the substrate.

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

In a first embodiment of the method, the displacement movement of the doctor blade is temporally divided into movement and stoppage sections, and during the printing operation, the duration of the stoppage sections prevails. 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.

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

In a second embodiment of the method, the displacement movement is a periodic reciprocating movement with a period of at least 10 seconds, in particular at least 1 minute, preferably at least 10 minutes. Such a displacement movement can be carried out continuously during the printing operation and significantly reduces the impairment of the printed image with respect to a faster oscillation of the doctor blade. With appropriate wear resistance of the doctor blade, the period can also be much higher, for example, 1 hour. Also in the second embodiment, the described negative influence of the blade movement on the printed image is greatly reduced while still preventing uneven wear.

In both embodiments of the method according to claim 1 of the sliding movement, a vibratory 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. It serves on the one hand to remove impurities from the wells of the cylinder or to solve the doctor blade, as in the European Patent Application EP 1 362 696 the applicant is described. However, particularly in the second embodiment, the vibratory motion also serves to reduce differences in the effectiveness of the doctor blade, which occur due to the standstill occurring during a periodic reciprocating motion during the reversal of the direction of movement. 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 speed limits specified in claim 1 relate only to the pure displacement movement without consideration of the vibration.

The subject of claim 5 is a printing machine with a squeegee device, which has a doctor blade engageable against a cylinder and a displacement device for moving the doctor blade in the direction of the longitudinal axis of the doctor blade, wherein the displacement device is adapted to cause a displacement movement of the doctor blade so that during the overwhelming duration of the printing operation, the displacement speed of the doctor blade in the range of zero to 0.1 m / s, in particular from zero to 0.01 m / s, and wherein the doctor device comprises an oscillator for generating a vibratory movement of the doctor blade and the displacement means and the oscillator are adapted to cause the displacement movement and a vibratory movement of the doctor blade so that the displacement movement of the Vibration movement is superimposed and this has a frequency of at least 1 Hz, in particular at least 5 Hz.

The displacement device may in particular be designed to carry out a method for displacing the doctor blade attached to the cylinder according to one of the claims 1 to 4. 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 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 or a periodic reciprocation with a particularly large period, 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 Figure 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.

The gravure printing machine shown in Figure 1 comprises a gravure cylinder 10, an applicator roll 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 can be seen more clearly in Figure 2. The application roller 12 thus absorbs ink from the ink tray 20 and transmits it to the peripheral surface of the gravure cylinder 10, which rotates in the direction of arrow in Figure 2 and transfers the ink to a printing substrate 22, the between passes through the impression roller 14 and 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 so against the circumference of the gravure cylinder, 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 Figure 1. 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.

Figure 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 onto a take-up reel 46 after being printed in the gravure printing press via deflection rollers 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 the rewinder have not been shown here since they are not essential to the understanding of the invention.

Two different displacement movements of the doctor blade 26 are sketched in FIGS. 4 and 5, 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 FIGS. 4 and 5 and FIG. 7 described below are not shown in relation to one another.

FIG. 4 illustrates a displacement movement of the doctor blade 26, which is subdivided in time into movement sections 50 and standstill 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 is displaced respectively in the same direction and by the same amount, for example 1 mm. 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.

Deviating from the example shown in FIG. 4, 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 take-up reel 46 is wound in each case. A not-shown sensor detects the radius of the roll on the take-up roll 46 and triggers, when a roll change is required, the moving portion 50 from. 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 has occurred due to the movement of the doctor blade 26, the defect is thus located in a section of the printing material web 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.

Figure 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.

Figure 6 shows a comparison with Figure 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 Gravure cylinder 10, that is 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 vibration movement is in the ultrasonic range, so that the vibration vibrations of the doctor blade 26 have the shape of running ultrasonic waves that propagate to the opposite end of the doctor blade and there by a between the lever 32 and the holder 28 inserted damper 56 are absorbed.

However, the frequency can also be significantly lower, and the oscillator 54 may be, for example, an acoustic vibrator. Even an even lower 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 sections of a displacement movement of the doctor blade 26 according to FIG. 5, which is superimposed on a vibratory movement. 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. As a result of the superposed vibration movement shown in FIG. 7, a further increase in print quality or, for the same quality, a higher displacement speed of the doctor blade is possible in comparison with the displacement movement shown in FIG. 5 without superimposed vibratory motion.

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 (10)

Method for displacing a doctor blade (26) mounted on a cylinder (10) of a printing machine in the direction of the longitudinal axis of the doctor blade (26), in which the displacement movement of the doctor blade (26) is such that during the predominant duration of the printing operation the displacement speed of the doctor blade (26) Doctor blade (26) in the range of zero to 0.1 m / s, in particular from zero to 0.01 m / s, characterized in that the sliding movement a vibratory movement with a frequency of at least 1 Hz, in particular at least 5 Hz, is superimposed. Method according to Claim 1, characterized in that the vibratory movement is carried out in the direction of the longitudinal axis of the doctor blade (26). Method according to Claim 1 or 2, characterized in that the displacement movement of the doctor blade (26) is subdivided into movement (50) and standstill sections (52) such that during the printing operation the duration of the stationary sections (52) predominates, in particular the duration of the Movement sections (50) is less than 10 percent of the duration of the stoppage sections (52), and that the movement sections (50) each lie in operating phases in which committee is printed. A method according to claim 1 or 2, characterized in that the displacement movement is a periodic reciprocating movement with a period of at least 10 seconds, in particular at least 1 minute. A printing machine with a squeegee device (24) which has a doctor blade (26) which can be turned 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). causing a displacement movement of the doctor blade (26) so that during the predominant duration of the printing operation, the displacement speed of the doctor blade (26) in the range of zero to 0.1 m / s, in particular from zero to 0.01 m / s, characterized in that the doctor device (24) comprises an oscillator (54) for generating a vibratory movement of the doctor blade (26) and the displacement device (38) and the oscillator (54) are designed to effect the displacement movement and a vibratory movement of the doctor blade (26) such that the displacement movement is superimposed on the vibration movement and this has a frequency of at least 1 Hz, in particular at least 5 Hz, Has. Printing machine according to claim 5, characterized in that the oscillator (54) is adapted to cause the vibratory movement of the doctor blade (26) so that the stroke of the vibratory movement is smaller than 0.2 mm. Printing machine according to Claim 5 or 6, characterized in that the doctor device (24) is designed to effect the vibration movement in the direction of the longitudinal axis of the doctor blade (26). Printing machine according to one of claims 5 to 7, characterized in that the displacement device (38) is adapted to effect the sliding movement in the form of a periodic reciprocating movement with a period of at least 10 seconds, in particular at least 1 minute. Printing machine according to one of Claims 5 to 7, characterized in that the doctoring device (24) is designed to effect the displacement movement of the doctor blade (26) in such a way that the displacement movement is subdivided in time into movement (50) and standstill sections (52) and during printing operation, the duration of the stoppage sections (52) predominates, in particular the duration of the movement sections (50) is less than 10 percent of the duration of the stoppage sections (52), and in that the movement sections (50) each lie in operating phases in which the board is printed becomes. Printing machine according to one of claims 5 to 9, characterized in that the doctor blade (26) is ceramized on its wear side.

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