EP0598240A1 - Rotogravure printing machine and method - Google Patents

Abstract

In a rotogravure printing machine (1) having at least two printing units (24 to 27 and 30 to 33) and a drying device (34 to 36; 38 to 40) arranged between said printing units, through which a paper web (2) to be printed runs one after the other, to simplify the operation and to reduce the occurrence of waste, provision is made for the printing units to be aligned in such a way that the paper web runs in a straight line from the preceding printing unit through the drying device without contact to the subsequent printing unit, guided only by the forme cylinders (55, 55) and impression cylinders (56, 56) of these two printing units. <IMAGE>

Description

The invention relates to a rotogravure printing machine of the type mentioned in the preamble of claim 1, and to a method for operating such a machine according to the preamble of claim 11.

Such machines and methods are generally known and are also described, for example, in DE-PS 35 30 561. In order to print a multicolor paper web, a separate printing unit is provided for each printing ink, the core of which forms a rotating forme cylinder immersed in an ink tray, against which the continuous paper web is pressed with the aid of a rotating impression roller. The paper web is fed from above to the "pressure gap" formed between the forme cylinder and impression roller, the guiding and deflection taking place with the aid of lead spindles. The paper web must pass through drying facilities behind each printing nip, since in rotogravure printing, unlike in offset printing, Up to now, the freshly printed color has been largely dried before the next color is printed. The drying devices can either be formed by drying cylinders, as shown in DE-OS 35 30 561, or by drying chambers, which have a considerable length, in particular in modern machines which are run at high speeds, in order for each paper web section to be dried to achieve a sufficiently long residence time inside these chambers. Regardless of the special design of the drying device, the paper web is also guided in these areas with the aid of a large number of guide or deflection rollers, which are referred to below as lead screws. For example, since eight printing units are required for two-sided four-color printing, each of which comprises seven to ten lead screws on the order of magnitude, a number of difficulties arise with the known rotogravure printing machines:
A major problem is that none of the many leading spindles has its own drive, but each one is driven by the paper web to be printed. As a result, there is a large amount of waste with every speed change, especially when starting and stopping the machine. When the paper web is accelerated, the leading spindles exert a braking effect, while when decelerating they tend to continue to rotate at the previously driven high speed, so that they first have to be braked by the paper web. It therefore takes a long time before the newly desired stable state is reached when the speed changes, in which the register status can be adjusted with the required accuracy. All the paper that is in the machine during this transition period and that is entering the machine is printed with an insufficient register accuracy and can therefore not be used.

Particular problems arise when the machine has to be stopped very quickly due to a tear in the paper web or a fire. Not least because of the immense size of the conventional rotogravure printing presses, which are particularly suitable for two-sided four-color printing, such incidents are not uncommon and, depending on the printed product produced, a waste content of 6% to 10% must be expected.

In contrast, the object of the invention is to develop a rotogravure printing press and method of the type mentioned at the outset in such a way that a substantially higher level of operational reliability is achieved and in particular the amount of waste can be reduced considerably. In addition, the amount of work required to operate the machine is to be reduced.

To achieve this object, the invention provides the features summarized in claims 1 and 11, respectively.

This solution is based on the knowledge that, in the case of the gravure printing inks available today, it is entirely sufficient if the top layer of the ink applied to the paper web in the preceding printing unit is dried so as to be smudge-proof so that the next color can be easily printed on in the subsequent printing unit. The previous thorough drying of the previous color before application of the subsequent one is no longer necessary. Therefore, the drying devices arranged between the successive printing units can be designed in a straight line and so short that the guidance which the paper web to be printed receives through the forme cylinders and impressioners of the preceding and the following printing unit is completely sufficient. An additional guide between the printing units, one after the other Print the same side of the paper web, and in particular in the drying devices is not required, so that most of the leading spindles previously used can be omitted. In fact, it is possible to equip a rotogravure printing machine according to the invention, comprising eight printing units, for two-sided four-color printing overall with no more lead spindles than are used in conventional machines for a single printing unit.

This has a number of advantages:
The path that the paper web to be printed travels within the rotogravure printing machine is considerably shortened. This increases the running safety significantly. The risk that the paper web will tear is greatly reduced. If such a malfunction does occur, the machine can be stopped much faster because the much reduced number of lead spindles stores considerably less rotational energy, which has to be converted into heat when stopped. Even with an operational change in the running speed, the above-mentioned delay effects due to the lead screws are greatly reduced, so that the new printing speed can be achieved much faster. Since the length of paper web in the machine at all times is much shorter than with conventional machines, the amount of paper waste is greatly reduced in this way.

The paper web experiences much less resistance and is therefore less stretched. The register accuracy is significantly increased in this way.

The energy requirement is due to the lower friction losses and the reduced "stored" rotational energy converted to lost heat when stopped, greatly reduced.

A major advantage of the straight-line, contact-free guidance of the paper web from one printing nip to the next can be seen in the fact that there are in particular the two leading spindles which, according to the prior art, are arranged directly in front of or behind the printing nip parallel to the forme cylinder, around the one coming from above To divert paper web for passing through the printing nip from a substantially vertical course into the horizontal and then back up again. At least one of these two leading spindles is necessarily in operation in the area of the movement path that the forme cylinders have to pass through, e.g. A cylinder change takes place when the machine is converted to another printed product.

In the prior art, each of the two stub axles, which protrude beyond the front ends of the forme cylinder, is mounted in a ring bearing, which in turn rests on the machine frame. When a forme cylinder is replaced, it is lifted upwards from the machine frame together with the two ring bearings using a special lifting device and then moved parallel to itself and transversely to its longitudinal axis into the space between its and the adjacent printing unit. The ring bearings are then pulled off in the axial direction and the forme cylinder is moved out of the space between the printing units by sliding in the longitudinal direction.

Conversely, the new forme cylinder to be installed is moved lengthways into this space and, after the ring bearing has been attached, transversely onto its stub axle moved to its longitudinal direction in a position above its actual working position, in which it is then finally lowered.

In order to be able to carry out these movements, not only must the relevant impression roller be raised by a considerable amount in the prior art, but also that of the last two leading spindles mentioned, which is located on the side of the printing unit, to which the forme cylinder is removed. This requires complex mechanics, which can be dispensed with in a rotogravure printing machine according to the invention together with the mentioned lead screws. Thus, the measures according to the invention also considerably simplify the installation and removal of the forme cylinders and make them more easily accessible to automation.

The printing units used to print a paper web side are advantageously positioned vertically one above the other in a tower arrangement, so that they are traversed vertically by the paper web to be printed.

This arrangement leads to a significant reduction in the footprint of such a machine.

Another advantage of this tower arrangement is that during operation each of the impressioners no longer sits exactly above the associated forme cylinder and presses it from above. Rather, it is possible to position the impression roller essentially laterally and with its axis only slightly above the axis of rotation of the forme cylinder. As a result, it is not necessary for a change of the forme cylinder to raise the impression roller strongly from its operating position; instead, it is sufficient to make it minor to fold away from the forme cylinder, for which a much simpler mechanism can be used. The tower arrangement of the printing units thus also makes it easier to install and remove the forme cylinders.

In order to keep the height by which the forme cylinder has to be raised or lowered during installation particularly small, it is provided according to a particularly preferred embodiment to provide a steady rest bearing for each axle stub instead of the previously customary ring bearing or comprises three support rollers and is open to the extent that the form cylinder with its stub shaft can simply be inserted from the front above or lifted out at the front. These bezel bearings can be firmly connected to the machine frame in such a way that they can be adjusted to adapt to different forme cylinder diameters. This also eliminates the need to remove the ring bearings from the forme cylinders to be removed and, in particular, to place them on the stub axles of the newly to be installed forme cylinders.

The latter is often difficult in practice because the stub axles have to fit very precisely into the inner bearing rings, so that no tilting or tilting can be absorbed. If the forme cylinder to be installed is only a few ° C too warm, which is easily possible due to the previous galvanic treatment, the bearings can often not be pushed open due to the temperature-related radial expansion of the axle stub unless there has been a corresponding cooling. When using bezel bearings according to the invention, all of these difficulties are eliminated. Since with bezel bearings, the bearing forces of fewer bearing elements have to be absorbed for longer periods of time than with the ring bearings conventionally used previously assumed that steady rest bearings, particularly at high speeds, such as those used today in rotogravure printing presses, become too hot and are not able to support a forme cylinder with the required stability. In practice, however, it has surprisingly been shown that these fears are unfounded. It is entirely possible to ensure sufficient cooling of the bezel bearings and the dead weight of the forme cylinder and the pressing force of the impression roller are sufficient to ensure stable storage.

Another obstacle to installing and removing the forme cylinder transversely to the longitudinal direction has so far been the doctor blade arrangements, which are positioned according to the prior art in such a way that the generatrix along which the doctor blade contacts the forme cylinder is as close as possible to the printing gap, i.e. located above the axis of rotation of the forme cylinder. This was considered necessary in order to avoid drying of the printing ink in the depressions of the forme cylinder on the way between the doctor blade and the paper surface to be printed. Not least because of the high printing speeds of modern rotogravure printing machines, this danger does not exist.

According to the invention, the doctor blade arrangement is therefore positioned such that the surface line along which the doctor blade contacts the forme cylinder is not higher and preferably lower than the axis of rotation of the forme cylinder taking its operating position. The doctor blade arrangement is thus arranged outside the area through which the forme cylinder moves when it is installed or removed. The hitherto customary mechanism for lowering and folding away the doctor blade arrangement can thus be dispensed with and it is only necessary to provide a way of adapting the squeegee position to different forme cylinder diameters. This measure also contributes to a greatly simplified and therefore easier to automate installation and removal of the forme cylinders.

A particular advantage of the tower arrangement is that the building surrounding the machine can be designed as a capsule into which the paper web to be printed enters through a narrow slot and which it leaves after printing and drying through an opposite, equally narrow slot.

Such an encapsulation enables extremely effective sound insulation to the outside and allows virtually complete recovery of the solvent released when the paint dries. Since nobody has to be inside the capsule while the machine is in operation, the values of the maximum solvent concentration at the workplace can be reduced to a minimum, so that they can be considerably below the permitted values.

In the event of a fire inside the capsule, which can be detected very easily due to the compact, closed arrangement, it is possible to automatically cut the continuous paper web at the entry and exit slit in order to close these slits within a very short time, after which the entire capsule inside can be flooded with CO₂ in a few seconds. In this way, the safety and environmental compatibility of such machines can be significantly increased.

In addition to the printing unit tower (s), an elevator can be arranged inside or outside the building capsule, which allows the forme cylinders that are no longer required to be removed from the printing units of a tower and the new forme cylinders to be introduced in the next step.

Advantageous further developments of the rotogravure printing machine according to the invention are laid down in the subclaims.

Fig. 1

eine stark schematisierte Seitenansicht einer erfindungsgemäßen Rotationstiefdruckmaschine für einen beidseitigen Vierfarbendruck,

Fig. 2

ein stark vergrößertes Detail der Maschine aus Fig. 1.

Fig. 3

in schematischer Weise die Lagerung eines Formzylinder-Achsstummels in einem Lunette-Lager.

The invention is described below using an exemplary embodiment with reference to the drawing; in this shows:

Fig. 1

2 shows a highly schematic side view of a rotogravure printing machine according to the invention for two-sided four-color printing,

Fig. 2

a greatly enlarged detail of the machine of Fig. 1st

Fig. 3

in a schematic way the storage of a forme cylinder stub in a Lunette bearing.

The rotogravure printing machine 1 shown in the figures is used for double-sided printing of a paper web 2, which is drawn off from a paper roll 5 mounted on a roll carrier 4, from which it runs approximately vertically upwards to three guide spindles 6, 7, 8, which leads to a deflection serve in the horizontal and of which the lead screw 7 serves as a tension roller so that the paper tension can be regulated again from the roller carrier 4 to the first printing unit 24.

The horizontal section of the paper web 2 following the guide spindles 6, 7, 8 runs through a narrow entry gap 10 into a building area which encloses the entire rotogravure printing press 1 in the manner of a capsule 12 and during operation with the exception of the mentioned entry gap 10 and one on the opposite side of the exit gap 13 through which the finished printed paper web 2 leaves the capsule 12 is completely sealed.

Behind the exit gap 13, the paper web 2, printed on both sides, passes through a device 14, again consisting of three guide spindles, for adjusting the register position in a subsequent superstructure 15, which is only indicated in the drawing, in which it is divided lengthwise and placed on top of one another via turning bars and cut across with the aid of knife rollers until it is then folded and collected in a folder 16 to the intended product.

Inside the capsule 12, two groups of four printing units 24, 25, 26, 27 and 30, 31, 32, 33, each of which are arranged vertically one above the other, are provided on the building floor 18 and three walk-in galleries 19, 20, 21, of which the first group 24 to 27 for printing the face side with the four colors yellow, red, blue and black and the second group 30 to 33 for printing the reverse side with these colors.

Short drying sections 34, 35, 36 and 38, 39, 40 are provided between successive printing units of each of these two tower-type printing unit groups, each of which is assigned an extractor hood 42, 43, 44 or 46, 47, 48.

After passing through a horizontal section following the entry nip 10, the paper web 2 is deflected downward via a guide spindle 50 such that it enters the uppermost printing unit 24 of the first printing unit tower vertically from above. It runs through this entire printing tower, i.e. all the printing units 24 to 27 located here and the drying devices 34, 35 and 36 arranged between them in the vertical direction downwards so that they come into contact only with the four forme cylinders 55 and the associated impression rollers 56. The short drying devices 34 to 36 are sufficient to at least superficially dry the ink applied in the preceding printing unit 24 to 26 to such an extent that it is not blurred in the subsequent printing unit 25 to 27.

The bottom printing unit 27 of the fine printing tower is also followed by a drying device 58 with an associated extractor hood 59. These two units are located in a tub 60 under the building floor 18, the interior of which belongs to the interior of the capsule 12. For reasons of space saving, the drying device 58 is arranged horizontally, so that a lead screw 61 is provided between it and the preceding printing unit 27, which, like the lead screw 62 following the drying device 58, bears against the unprinted reverse side of the paper web 2.

With the help of the lead screw 62, the paper web 2 is redirected into the vertical. It runs upwards through a long drying device 65 which extends upwards beyond the printing units 24, 30 arranged in the uppermost gallery 21. The paper web emerging from the long drying device 65 is deflected twice via three guide spindles 67, 68, 69, of which the middle one is again displaceable for setting the register position, and enters from above into the counterpressure printing unit tower with the printing units 30 to 33 and interposed short drying devices 38 to 40 which they use in the same It goes through as described previously for the front printing tower, only that the reverse side is now printed with four colors.

The first leading spindles which come into contact with this side after printing on the face printing side are the lead spindles 67 and 68. Since the paper web has passed through the long drying device 65 at this time, this contact is completely uncritical because the colors printed on the face printing side are largely dry.

The bottom printing unit 33 of the counterpressure tower is followed by a short drying device 70 with an extractor hood 71 leading into the tub 60. This drying device is still traversed by the paper web 2 in the vertical direction, because the subsequent guide spindle 72, which serves to deflect it into the horizontal, comes into contact with the just printed reverse side. After passing through a short horizontal section, the paper web 2 is redirected into the vertical with the aid of a guide spindle 74, in which it passes through a further long drying device 75 vertically upward, which extends approximately to the level of the uppermost gallery floor 21. There is a further lead screw 77, with the aid of which the paper web 2 is redirected into the horizontal in order to leave the capsule 12 through the outlet gap 13.

From this description it follows that the entire rotogravure printing press 1 suitable for two-sided four-color printing only requires nine lead spindles between the entry nip 10 and the exit nip 13, which corresponds approximately to the number of lead screws that are used in conventional rotogravure printing presses in a single printing unit. The total paper length that located at any time in the rotogravure printing machine according to the invention, ie inside the capsule 12, is approximately four times the height of the overall arrangement plus the length, ie the distance between the entry nip 10 and the exit nip 13. It should be taken into account that for a conventional rotogravure printing machine with eight printing units needs about twice the length and the paper web in each conventional printing unit with associated drying device has to go through half the height of the system shown in Fig. 1, so there is a halving of the length of paper web in the system at any time in the arrangement according to the invention.

As can be seen from FIGS. 1 and 2, the printing units are "open" towards one long side so that the forme cylinders can be exchanged via this side. In Fig. 1 this "open" side of the printing units 24 to 27 of the printing tower is directed to the left and in the printing units 30 to 33 of the counter-printing tower to the right. Accordingly, there is an elevator 80 and 81 to the left of the printing tower and to the right of the counterpressure tower, which is designed here in the form of a paternoster, and with the help of which printing cylinders 55 that are no longer required are removed from all printing units of a printing tower and the new forme cylinders are removed in another Work step can be fed simultaneously. This is symbolically indicated in FIG. 1 for the uppermost printing units 24 and 30 of the two printing unit towers by a forme cylinder 55 ', which is located on a conveyor device 82 and 83 leading from the relevant elevator 80 and 81 to the printing unit 24 and 30, respectively . At the level of the upper gallery 21, two forme cylinders 55 'are shown in each of the two elevators 80 and 81 in order to indicate their mounting in the paternoster elements.

2 shows the uppermost printing unit 24 of the fine printing tower again on a greatly enlarged scale. It can be seen very clearly here how the forme cylinder 55 dips into an ink pan 85 and is freed of the excess ink on its outlet side with the aid of a doctor blade 86. This doctor blade is arranged so deeply in deviation from the usual in operation that the surface line, along which the doctor blade touches the forme cylinder 55 during printing operation, is lower than the axis of rotation 57 of the printing cylinder. As a result, the doctor blade 86 has to be lowered only slightly or not at all when the printing cylinder is to be replaced.

In order to keep the height, which the pressure cylinder 55 has to be raised or lowered during installation, as small as possible, the stub axles 87 are preferably, as shown in FIG. 3, in a bezel bearing 90, for example having three bearing rollers 88 stored.

On the one hand, it is essential to the whole arrangement that the printing units used for printing on one side of the paper web are arranged in such a way that the paper web can run from one pair of impression cylinders to impression presses without experiencing a significant change in direction. In this way, the guiding effect exerted by the forme cylinders and associated impression rollers is completely sufficient to guide the paper web at least through all of the printing units that are required for printing on one side. This measure, which leads to a considerable reduction in the number of guide spindles required, can be used not only in the tower arrangement shown in the exemplary embodiment but also when the printing units are installed horizontally one behind the other. Are also in the frame Rotogravure printing machines are conceivable in which the eight printing units required for two-sided four-color printing are distributed over four towers, each of which comprises two printing units positioned one above the other. The invention is also not limited to two-sided four-color printing, but can always be used when a paper web is to be printed using two or more printing units.

On the other hand, it is of great importance that the omission of the leading spindles arranged in the immediate vicinity of the printing nip, the lowering of the squeegee arrangement and the use of bezel bearings simplify the installation and removal of the forme cylinders transversely to the longitudinal direction to such an extent that it is can be done largely automatically.

The elevators 80, 81 can also be arranged outside the building capsule 12, in which case there is a provision device at the level of each printing unit outside the capsule, which is separated from the inside of the capsule during printing operation by a closure device, for example, designed as a blind. This offers the advantage that all forme cylinders required for the next printing process in a printing unit tower can be brought into position with a simple lift while the preceding printing process is still running. If this is then ended, the closure devices are opened, the forme cylinders previously used are conveyed out of the printing units and the building capsule and temporarily stored in the preparation device. The forme cylinders required for the next printing process can then be brought into the interior of the capsule and inserted into the printing units.

Then the shutters are closed and the next printing process can begin. Then there is again sufficient time to lower the previously used forme cylinders deposited on the provisioning device individually onto the floor with the aid of the lift and to remove them there.

The final drying device 75 can also be arranged outside the building capsule 12.

As an alternative to the horizontal arrangement shown in FIG. 1, the drying device 58 arranged below the front printing tower can also be designed and arranged vertically, as is shown for the drying device 70 arranged downstream of the counterpressure tower. In this case, the lead screw 61 is positioned behind the drying device 58, since the paper web 2 still runs through it vertically from top to bottom in a guide-free manner.

Claims (14)

Rotogravure printing machine in which a paper web to be printed passes through at least two printing units and a drying device arranged between these printing units in order to successively print at least two colors on one and the same side of the paper web, characterized in that the at least two printing units are aligned such that the paper web ( 2) from the forme cylinders (55, 55) and impression rollers (56, 56) of these two printing units (24 to 27; 30 to 33) guided in a straight line from the previous printing unit through the drying device (34 to 36; 38 to 40) to the subsequent printing unit runs and that the printed paper web side only comes into contact with the forme cylinders (55, 55). Rotogravure printing machine according to claim 1, characterized in that the paper web side which is not printed in the two printing units only comes into contact with the impression rollers (56, 56). Rotogravure printing machine according to claim 1 or 2, characterized in that, for two-sided multi-color printing, the printing units (24 to 27; 30 to 33) serving for printing on each side of the paper web (2) are arranged vertically one above the other in a tower-like manner and in that the paper web (2) is inside this tower only comes into contact with the forme cylinders (55) and the impression rollers (56). Rotogravure printing machine according to claim 3, characterized in that after leaving each printing unit tower , the paper web (2) is deflected into the horizontal and then back into the vertical with the aid of two guide spindles (61, 62; 72, 74). Rotogravure printing machine according to claim 4, characterized in that the paper web (2) passes through a drying device (65; 75) vertically behind the second lead screw (62; 74), the length of which is approximately equal to the height of the printing unit tower. Rotogravure printing machine according to one of claims 3 to 5, characterized in that a device (67, 68, 69) for coarse adjustment of the register position is arranged in the direction of movement of the paper web (2) in front of the impression tower and that the fine adjustment for each forme cylinder (55) is within the Printing unit with the aid of a device for changing the rotational speed of the forme cylinder (55) in question. Rotogravure printing machine according to one of the preceding claims, characterized in that each of the two stub axles (87) of a forme cylinder (55) is mounted in a steady rest bearing (90). Rotogravure printing machine according to one of the preceding claims, characterized in that the squeegee arrangement (86) for at least one of the forme cylinders (55) is positioned during operation such that the surface line along which the doctor blade contacts the forme cylinder (55) is no higher than the axis of rotation (57) of the forme cylinder (55). Rotogravure printing machine according to one of Claims 3 to 8, characterized in that an elevator (80, 81) for automatically feeding and removing the forme cylinders (55) is arranged next to each printing tower. Rotogravure printing machine according to one of claims 3 to 9, characterized in that the two printing unit towers are arranged in a capsule-like building (12), the interior of which during printing operation can only be closed via an closable inlet slot (10) and an closable outlet slot (13) for the printing paper web (2) with which external value is in direct connection. Rotogravure printing process, in which a paper web to be printed runs through at least two printing units, with the aid of which two colors are successively printed on one and the same side of the paper web, and in which drying takes place between these two printing units, characterized in that the preceding two Printing units printed ink is only dried to the extent that smudge-proof printing is possible in the subsequent printing unit and that the paper web is guided from the printing nip of the preceding printing unit to the printing nip of the subsequent printing unit in such a way that at least the paper web side printed by the two printing units remains contact-free. Rotogravure printing method according to claim 11, characterized in that the paper web is guided completely contact-free between the two printing nips. Rotogravure printing method according to claim 11 or 12, characterized in that deeper drying takes place only when one side of the web is printed with all the colors. Rotogravure printing method according to one of Claims 11 to 13, characterized in that both sides of the paper web are printed with a plurality of colors in each case and the complete drying takes place only after the last printing unit has been run through.

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