GB2415408A

GB2415408A - Web-fed printing machine with no bearer rings on the printing / impression cylinder

Info

Publication number: GB2415408A
Application number: GB0512857A
Authority: GB
Inventors: Stefan Albrecht; Norbert Dylla
Original assignee: MAN Roland Druckmaschinen AG
Current assignee: Manroland AG
Priority date: 2004-06-26
Filing date: 2005-06-23
Publication date: 2005-12-28
Anticipated expiration: 2025-06-23
Also published as: GB0512857D0; GB0722710D0; GB2415408B; GB2441076B; CH697939B1; GB2441076A; DE102004031029A1

Abstract

A web fed rotary printing machine has at least two pairs of cylinders (21 and 22) consisting of one transfer (25, 26) one forme (23, 24) and one printing / impression cylinder (27). Bearer or Schmitz rings (29) are attached to the ends of the transfer and forme cylinders. The print cylinder does not have any bearer rings fitted. The deletion of bearer rings serves to reduce pressure loadings on the roller drive train and improves bearing life. The forme and transfer cylinders may be sized to print up to six pages of print arranged axially side by side. The forme and transfer cylinders may have gaps in them for taking up dressings, printing plates or transfer blankets. The gaps may be staggered in a circumferential position.

Description

24 1 5408 '' 1 Printing unit for a web-fed rotary printing machine The

invention relates to a printing unit of a web-fed rotary printing machine in accordance with the preamble of claim 1 or 16 respectively.

In the case of printing units for web-fed rotary printing machines, in particular newspaper-printing machines, that have forme cylinders, transfer cylinders and printing cylinders, so-called bearer rings are used in order to minimize cylinder vibrations. In accordance with the prior art, bearer rings (Schmitz rings) are used in this connection on all the cylinders, that is, on the forme cylinders, the transfer cylinders and the printing cylinders (impression cylinders). If bearer rings are used on all of the above- mentioned cylinders, in particular in the case of the throw-on of a plurality of pairs of cylinders, consisting, in each case, of a forme cylinder and a transfer cylinder, onto a common printing cylinder, high bearer-ring forces have to be applied. This then results in great pressures in the region of the bearer rings and thus ultimately in a relatively large amount of wear of the same and also in relatively high bearing forces. High bearing forces reduce the service life of the bearings and necessitate mountings that have bigger dimensions and are therefore more expensive. All in all the use of bearer rings on all the cylinders, that is, on the forme cylinders, transfer cylinders and counter-cylinders, is disadvantageous.

Basing considerations on this, the problem that underlies the present invention is that of providing a new type of printing unit of a web-fed rotary printing machine.

This problem is solved by means of a printing unit of a web-fed rotary printing machine in accordance with claim 1 or 16 respectively.

In accordance with a first aspect of the invention, associated with the forme cylinder and the transfer cylinder of each pair of cylinders there are bearer rings which roll off on each other with a pre- tensioning force in the impression-on position, with the or each impression cylinder not having any bearer rings cooperating with the bearer rings of the respective transfer cylinders. For the purposes of the present invention it is proposed that bearer rings merely be associated with the forme cylinder and also with the transfer cylinder of each pair of cylinders and that bearer rings on the impression cylinders, on the other hand, be foregone. As a result of the omission of the bearer rings on the impression cylinder, high bearer-ring forces can be avoided. As a result, on the one hand the outlay for the mounting of the cylinders is reduced and on the other hand cost- savings are made as a result of the omission of the bearer rings on the printing cylinder.

In accordance with a second aspect of the invention, each transfer cylinder has a plurality of cylinder gaps that are staggered in relation to each other in the circumferential direction. As a result of the use of cylinder gaps that are staggered in the circumferential direction on the transfer cylinders of each pair of cylinders it is possible to minimize the excitation of vibrations of the cylinders so that the bearer rings can be omitted on the or each impression cylinder. The cylinder gaps on the transfer cylinders are preferably not merely staggered in relation to each other in the circumferential direction, but rather are also formed so that they are relatively narrow, namely with a width in the circumferential direction of approximately 1 mm to 5 mm.

A printing unit is particularly preferred in which both of the above aspects are combined with each other, in which therefore on the one hand bearer rings that roll off on each other with a pre-tensioning force in the impression-on position are associated with the forme cylinder and the transfer cylinder of each pair of cylinders, with the or each printing cylinder not having any bearer rings cooperating with the bearer rings of the respective transfer cylinders, and in which on the other hand each transfer cylinder has a plurality of cylinder gaps that are staggered in relation to each other in the circumferential direction.

For a better understanding of the invention embodiments of it will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a side view of a web-fed rotary printing machine printing unit that is known

from the prior art;

Figure 2 shows a web-fed rotary printing machine printing unit as a first embodiment of the invention in a front view; Figure 3 shows a side view of the web-fed rotary printing machine printing unit in accordance with the invention from Figure 2; Figure 4 shows a side view of a web-fed rotary printing machine printing unit as a second embodiment of the invention; and Figure 5 shows a side view of a web-fed rotary printing machine printing unit as a third embodiment of the invention.

Figure 1 shows a printing unit 10 that is known from the prior art and pertains to a web-fed rotary printing machine, in particular a newspaperprinting machine, having two pairs of cylinders 11 and 12, with each of the pairs of cylinders 11 and 12 having, in each case, a forme cylinder 13 and 14 respectively and also a transfer cylinder 15 and 16 respectively. Positioned on the forme cylinders 13 and 14 there are printing plates and on the transfer cylinders 15 and 16 there are so- called transfer blankets, which are also referred to as rubber blankets. Furthermore, the printing unit 10 in accordance with Figure 1 in

accordance with the prior art comprises a printing

cylinder or impression cylinder 17, with the transfer cylinders 15 and 16 of both pairs of cylinders 11 and 12 cooperating with this printing cylinder 17 in an impression-on position, forming a respective print position 18. The print positions 18 are formed at that point where the transfer cylinders 15 and 16 roll off on the printing cylinder 17. In accordance with Figure 1, bearer rings 19 are positioned on each cylinder of the printing unit 10, that is, in the region of the forme cylinders 13 and 14 and also the transfer cylinders 15 and 16 and also in the region of the printing cylinder 17, with the bearer rings 19 being arranged at the axial ends of each cylinder.

With this prior-art arrangement, bearer rings 19 are positioned on each of the cylinders 13 to 17, so in the impression-on position high bearer- ring forces have to be applied. This is disadvantageous with regard to the wear of the bearer rings and also the bearings of the cylinders.

Figures 2 and 3 show a first embodiment of a printing unit 20 in accordance with the invention. The printing unit 20 of the embodiment of Figures 2 and 3 is in turn provided with two pairs of cylinders 21 and 22, with each of the pairs of cylinders 21 and 22 having, in each case, a forme cylinder 23 and 24 respectively and a transfer cylinder 25 and 26 respectively.

Furthermore, the printing unit 20 of the embodiment of Figures 2 and 3 comprises a printing cylinder or impression cylinder 27. The printing cylinder 27 in turn cooperates in an impression-on position with the two transfer cylinders 25 and 26 of both pairs of cylinders 21 and 22, forming so-called print positions 28. The print positions 28 in turn are formed at that point where the transfer cylinders 25 and 26 roll off on the common impression cylinder 27.

In accordance with a first aspect of the present invention, bearer rings 29 are associated with the forme cylinders 23 and 24 and also with the transfer cylinders 25 and 26 of both pairs of cylinders 21 and 22. As can be inferred from Figure 2, the bearer rings 29 can in each case be positioned in the region of the axial ends of the forme cylinders 23 and 24 and also the transfer cylinders 25 and 26. For the purposes of the present invention, however, no bearer rings are associated with the printing cylinder or impression cylinder 27. As a result, the bearer-ring forces that are to be applied in the impression-on position are reduced so that less wear occurs in the region of the bearer rings and also in the region of the bearings of the cylinders. As a result, all in all the costs for the printing unit can be reduced.

The forme cylinders 23 and 24, the transfer cylinders 25 and 26 and also the printing cylinder 27 have an axial width for printing at least two pages of print that are to be printed and that are arranged axially side by side. It is thus possible for the cylinders 23 to 27 to have an axial width for printing two or three or four or even six pages of print that are to be printed and are arranged axially side by side. Furthermore, the forme cylinders 23 and 24, the transfer cylinders 25 and 26 and also the printing cylinder 27 have a circumference for printing at least two pages of print that are to be printed and that are arranged one after the other in the circumferential direction. In the embodiment shown in Figures 2 and 3 the cylinders 23 to 27 have an axial width for printing six pages of print that are arranged axially side by side and also a circumference for printing two pages of print that are arranged one after the other in the circumferential direction. Accordingly, twelve pages of print can be printed simultaneously with each full revolution of the cylinders of one pair of cylinders.

The forme cylinders 23 and 24 and also the transfer cylinders 25 and 26 are provided with cylinder gaps for taking up dressings. The cylinder gaps of the forme cylinders 23 and 24 are used to take up the printing plates; the cylinder gaps in the region of the transfer cylinders 25 and 26 are used to take up transfer blankets, which are also referred to as rubber blankets. In the exemplary embodiment shown it may be assumed that each printing plate has a width to enable two pages of print positioned side by side in the axial direction to be printed with one printing plate, and also a height that corresponds to one page of print.

In the exemplary embodiment of Figures 2 and 3 this means that then in total six printing plates need to be positioned in the region of each forme cylinder 23 and 24, with in each case three printing plates being positioned axially side by side and with in each case two printing plates being arranged one after the other in the circumferential direction on the respective forme cylinder 23 and 24.

In the embodiment of Figures 2 and 3, for the purposes of positioning the printing plates on the forme cylinders each of the forme cylinders 23 and 24 is provided with two cylinder gaps 30, with each of the cylinder gaps 30 of the forme cylinder 23 and 24 respectively extending over the whole axial length of the respective forme cylinder 23 and 24. The two cylinder gaps 30 are staggered in relation to each other by approximately 180 in the circumferential direction of the respective forme cylinders 23 and 24.

It follows from this that two printing formes can be positioned one after the other in the circumferential direction on the respective forme cylinders 23 and 24.

Accordingly, when viewed in the circumferential direction, two axially extending cylinder gaps 30 are located at each axial position of the forme cylinder.

In order now to minimize the cylinder vibrations of the printing unit 20 of the exemplary embodiment of Figures 2 and 3, for the purposes of the present invention it is proposed that the transfer cylinders 25 and 26 also have cylinder gaps 31 that are staggered or offset in relation to each other in the circumferential direction of the transfer cylinders 25 and 26. In the embodiment of Figures 2 and 3, each of the transfer cylinders 25 and 26 has three cylinder gaps 31, which extend in the axial direction of the transfer cylinders 25 and 26 in sections along the respective transfer cylinder, each over approximately one third of the axial width of the same. The cylinder gaps 31 of the transfer cylinders 25 and 26 then extend in such a way in the axial direction that, when viewed in the circumferential direction, at each axial position of the respective transfer cylinder 25 and 26 there is only a single cylinder gap 31. A transfer blanket or rubber blanket that is held in the cylinder gaps 31 accordingly extends over the whole circumference of the respective transfer cylinder 25 and 26.

The cylinder gaps 31 in the region of the transfer cylinder 25 and 26 are now positioned in such a way on the transfer cylinders 25 and 26 that the two outer cylinder gaps 31 are in alignment with each other, whilst a central cylinder gap 31, which cannot be seen in Figure 2, is staggered in relation to the two outer cylinder gaps 31 by approximately 180 in the circumferential direction. As a result of the staggering of the three cylinder gaps 31 of each transfer cylinder 25 and 26 respectively in the circumferential direction, it is possible to minimize the excitation of vibrations of the cylinders 23 to 27 to such an extent that it is possible to dispense with bearer rings for the printing cylinder 27.

The cylinder gaps 31 in the transfer cylinders 25 and 26 are preferably not merely staggered in relation to each other in the circumferential direction, but also have a relatively small width in the circumferential direction of approximately 1 mm to 5 mm. The width of the cylinder gaps 31 is preferably smaller than or equal to 3.5 mm.

The cylinder gaps 30 in the forme cylinders 23, 24 and also the cylinder gaps 31 in the transfer cylinders 25, 26, despite the circumferential staggering of the cylinder gaps 31 in the region of the transfer cylinders 25 and 26, are aligned in relation to each other in such a way that the forme cylinders 23 and 24 and also the transfer cylinders 25 and 26 of each pair of cylinders 21 and 22 respectively roll off on each other in the impression-on position so that the cylinder gaps 31 of the transfer cylinders 25 and 26, in the region of contact 32 with the forme cylinders 23 and 24 respectively, coincide with the cylinder gaps 30 of the corresponding forme cylinder. In the embodiment of Figures 2 and 3 the central cylinder gap 31 of the transfer cylinders 25 and 26 is staggered in relation to the outer cylinder gaps 31 of the same transfer cylinders 25 and 26 by approximately 180 in the circumferential direction.

As an alternative to this it is also conceivable for the printing plates to have a width such that two pages of print that are positioned side by side in the axial direction can be printed with one printing plate and also a height that corresponds to two pages of print that are positioned one after the other. This would mean that then in total three printing plates are to be positioned in each forme cylinder, for which then in this respect the forme cylinders merely need one cylinder gap that extends over the whole axial length of the forme cylinders. The forme cylinders and also the transfer cylinders of each pair of cylinders then roll off on each other in the impression-on position in such a way that the cylinder gaps of the transfer cylinders, in the regions of contact with the respective forme cylinders, meet with the cylinder gaps of the corresponding forme cylinder or with the region of separation between two pages of print positioned one after the other.

At this point reference may be made to the fact that the cylinder gaps 31 in the region of the transfer cylinders 25 and 26 can also be staggered or offset in relation to each other at a different angle; thus, for example, the central cylinder gap 31 can be staggered in relation to the two lateral cylinder gaps 31 by approximately 90 or 120 . In order, however, in this case to guarantee that the forme cylinders 23 and 24 roll off on the corresponding transfer cylinders 25 and 26 properly, it is then also necessary for the two cylinder gaps 30 in the region of the forme cylinders 23 and 24 to be made up of cylinder gaps that are staggered in relation to each other in the circumferential direction and that each extend only over a part of the axial length of the forme cylinders.

Thus, in order to print properly, it must be guaranteed that when the forme cylinders 23 and 24 roll with the transfer cylinders 25 and 26 in the region of contact 32 of the same, the cylinder gaps 31 of the transfer cylinders 25 and 26 coincide with the cylinder gaps 30 of the corresponding forme cylinder 23 and 24.

In the embodiment of Figures 2 and 3 the printing unit 20 is constructed as a so-called five-cylinder satellite printing unit formed from two pairs of cylinders 21 and 22 each with one forme cylinder 23 and 24 and one transfer cylinder 25 and 26, with both pairs of cylinders 21 and 22 cooperating with a single printing cylinder 27. Figures 4 and 5 show printing units having a higher number of cylinder pairs. Thus, for example, the embodiment of Figure 4 shows a printing unit 33 that is formed as a nine-cylinder satellite printing unit and is formed from in total four pairs of cylinders 21 and 22 respectively, with each of the four pairs of cylinders 21 and 22 having in turn one forme cylinder 23 and 24 respectively and one transfer cylinder 25 and 26 respectively. All four pairs of cylinders cooperate with the same printing cylinder 27. In the embodiment of Figure 5 a printing unit 34 is shown that is formed as a ten-cylinder satellite printing unit and just like the printing unit 33 of Figure 4 has in total four pairs of cylinders 21 and 22 respectively. In the embodiment of Figure 5, in contrast with the embodiment of Figure 4, however, there are two satellite printing cylinders 27.

The embodiments of Figures 4 and 5 differ from the embodiment of Figures 2 and 3 merely in the number of cylinders. As regards the details that are relevant to the invention, namely with regard to the arrangement of the bearer rings 29 and the arrangement of the cylinder gaps 30 and 31 in the region of the forme cylinders and transfer cylinders respectively, however, all the exemplary embodiments correspond, so that in order to avoid unnecessary repetitions for the exemplary embodiments of Figures 4 and 5 reference is made in this respect to the statements that have been made with regard to the exemplary embodiment of Figures 2 and 3.

List of reference numerals Printing unit 11 Pair of cylinders 12 Pair of cylinders 13 Forme cylinder 14 Forme cylinder Transfer cylinder 16 Transfer cylinder 17 Printing cylinder 18 Page of print 19 Bearer ring Printing unit 21 Pair of cylinders 22 Pair of cylinders 23 Forme cylinder 24 Forme cylinder Transfer cylinder 26 Transfer cylinder 27 Printing cylinder 28 Page of print 29 Bearer ring Cylinder gap 31 Cylinder gap 32 Region of contact 33 Printing unit 34 Printing unit

Claims

Claims 1. A printing unit for a web-fed rotary printing machine, having at

least two pairs of cylinders (21, 22) consisting of, in each case, one forme cylinder (23, 24) and one transfer cylinder (25, 26), and having at least one printing cylinder (27), with the transfer cylinders (25, 26) of, in each case, at least two pairs of cylinders (21, 22) cooperating with each printing cylinder (27) in an impression-on position, characterized in that associated with the forme cylinder (23, 24) and the transfer cylinder (25, 26) of each pair of cylinders (21, 22) there are bearer rings (29) which roll off on each other with a pre-stress in the impression-on position, and in that the or each printing cylinder (27) does not have any bearer rings cooperating with the bearer rings of the respective transfer cylinders (25, 26).
2. A printing unit according to claim 1, in which the forme cylinders (23, 24) and the transfer cylinders (25, 26) and also the or each printing cylinder (27) have an axial width for printing at least two, preferably two or three or four or six, pages of print that are to be printed and that are arranged axially side by side.
3. A printing unit according to claim 1 or 2, in which the forme cylinders (23, 24) and the transfer cylinders (25, 26) and also the or each printing cylinder (27) have a circumference for printing at least two pages of print that are to be printed and that are arranged one after the other in the circumferential direction.
4. A printing unit according to any preceding claim, in which the forme cylinders (23, 24) and the transfer cylinders (25, 26) have cylinder gaps (30, 31) for taking up dressings, in particular for taking up printing plates on the forme cylinders and for taking up transfer blankets on the transfer cylinders.
5. A printing unit according to claim 4, in which the cylinder gaps (30) of the forme cylinders (23, 24) and the cylinder gaps (31) of the transfer cylinders (25, 26) extend substantially in the axial direction.
6. A printing unit according to claim 4 or 5, in which each transfer cylinder (25, 26) has at least two cylinder gaps (31) staggered in relation to each other in the circumferential direction.
7. A printing unit according to claim 6, in which the forme cylinders (23, 24) also have at least two cylinder gaps (30), staggered in relation to each other in the circumferential direction.
8. A printing unit according to claim 7, in which the forme cylinder (23, 24) and the transfer cylinder (25, 26) of each pair of cylinders (21, 22) roll off on each other in the impression-on position in such a way that the cylinder gaps (31) of the transfer cylinders, in the region of contact (32), meet with the cylinder gaps (30) of the corresponding forme cylinder.
9. A printing unit according to any of claims 4 to 8, in which the cylinder gaps (31) of the transfer cylinders (25, 26) have a width of 1 mm to 5 mm in the circumferential direction.
10. A printing unit according to any of claims 4 to 9, in which the forme cylinder (23, 24) of each pair of cylinders (21, 22) has two cylinder gaps (30), each extending over the whole axial length of the forme cylinder (23, 24) and being staggered in relation to each other in the circumferential direction of the same forme cylinder (23, 24) by approximately 180 , in such a way that in the axial direction in each case at least two printing plates can be guided side by side in the corresponding cylinder gaps (30) and in the circumferential direction in each case at least two printing plates can be guided one after the other in the corresponding cylinder gaps (30).
11. A printing unit according to any of claims 4 to 9, in which the forme cylinder of each pair of cylinders has one cylinder gap, which extends over the whole axial length of the forme cylinder, in such a way that in the axial direction at least two printing plates can be guided side by side in the cylinder gap and in the circumferential direction one printing plate can be guided in the cylinder gap, with the height of each printing plate corresponding to two pages of print positioned one after the other.
12. A printing unit according to claim 10 or 11, in which the respective transfer cylinder (25, 26) of each pair of cylinders (21, 22) has a plurality of cylinder gaps (31) that extend in the axial direction in sections along the transfer cylinder (25, 26) in such a way that, when viewed in the circumferential direction, at each axial position of the transfer cylinder in each case there is only a single cylinder gap (31), with at least one cylinder gap (31) of the transfer cylinder being staggered in relation to other cylinder gaps (31) of the same transfer cylinder in the circumferential direction.
13. A printing unit according to claim 12, in which at least one cylinder gap (31) of the transfer cylinder (25, 26) is staggered in relation to the other cylinder gaps (31) of the same transfer cylinder (25, 26) in the circumferential direction by approximately 180 .
14. A printing unit according to any of claims 4 to 9, in which the forme cylinder of each pair of cylinders has a plurality of cylinder gaps that extend in the axial direction in sections along the forme cylinder in such a way that, when viewed in the circumferential direction, at each axial position of the forme cylinder there are two cylinder gaps, with at least two cylinder gaps of the forme cylinder at the same axial position being staggered in relation to the other cylinder gaps of the same forme cylinder in the circumferential direction.
15. A printing unit according to claim 14, in which the respective transfer cylinder of each pair has a plurality of cylinder gaps that extend in the axial direction in sections along the transfer cylinder in such a way that, when viewed in the circumferential direction, at each axial position of the respective transfer cylinders there is only a single cylinder gap, with at least one cylinder gap of the transfer cylinder being staggered in relation to the other cylinder gaps of the same transfer cylinder in the circumferential direction.
16. A printing unit according to claim 15, in which at least one cylinder gap of the transfer cylinder is staggered in relation to the other cylinder gaps of the same transfer cylinder in the circumferential direction by approximately 180 or by approximately 120 or by approximately 90 .
17. A printing unit of a web-fed rotary printing machine having at least two pairs of cylinders (21, 22) each consisting of one forme cylinder (23, 24) and one transfer cylinder (25, 26), and having at least one impression cylinder (27), with the transfer cylinders (25, 26) of each pair of cylinders (21, 22) cooperating with the impression cylinder (27) in the impression-on position, and with the forme cylinders (23, 24) and the transfer cylinders (25, 26) having cylinder gaps (30, 31) for taking up dressings, for taking up printing plates in the case of the forme cylinders and for taking up transfer blankets in the case of the transfer cylinders, characterized in that each transfer cylinder (25, 26) has a plurality of cylinder gaps (31) that are staggered in relation to each other in the circumferential direction.
18. A printing unit according to claim 17, in which the transfer cylinder (25, 26) of each pair of cylinders (21, 22) has a plurality of cylinder gaps (31) that extend in the axial direction in sections along the transfer cylinder in such a way that, when viewed in the circumferential direction, at each axial position of the respective transfer cylinders (25, 26) there is a single cylinder gap (31), with at least one cylinder gap (31) of the transfer cylinder being staggered in relation to the other cylinder gaps (31) of the same transfer cylinder in the circumferential direction.
19. A printing unit according to claim 17 or 18, in which the cylinder gaps (31) of the transfer cylinders (25, 26) and, if applicable, the cylinder gaps (30) of the forme cylinders (23, 24) are staggered in relation to each other in the circumferential direction in such a way that the forme cylinder and the transfer cylinder of each pair of cylinders (21, 22) roll off on each other in the impression-on position in such a way that the cylinder gaps (31) of the transfer cylinders, in the region of a point of contact (32), meet with the cylinder gaps (30) of the corresponding forme cylinder.
20. A printing unit according to one or more of claims 17 to 19, in which the forme cylinder (23, 24) of each pair of cylinders (21, 22) has two cylinder gaps (30), which extend over the whole axial length of the forme cylinder and are staggered in relation to each other in the circumferential direction of the same forme cylinder by approximately 180 , in such a way that in the axial direction in each case at least two printing plates can be guided side by side in the corresponding cylinder gaps (30) and in the circumferential direction in each case at least two printing plates can be guided one after the other in the corresponding cylinder gaps (30).
21. A printing unit according to any of claims 17 to 19, in which the forme cylinder of each pair of cylinders has one cylinder gap extending over the whole axial length of the forme cylinder, in such a way that in the axial direction at least two printing plates can be guided side by side in the cylinder gap and in the circumferential direction one printing plate can be guided in the cylinder gap, with the height of each printing plate corresponding to two pages of print that are positioned one after the other.
22. A printing unit according to claim 20 or 21, in which the respective transfer cylinder (25, 26) of each pair of cylinders (21, 22) has a plurality of cylinder gaps (31) that extend in the axial direction in sections along the transfer cylinder in such a way that, when viewed in the circumferential direction, at each axial position of the transfer cylinder in each case there is only one single cylinder gap (31), with at least one cylinder gap (31) of the transfer cylinder being staggered in relation to the other cylinder gaps (31) of the same transfer cylinder in the circumferential direction.
23. A printing unit according to claim 22, in which at least one cylinder gap (31) of the transfer cylinder (25, 26) is staggered in relation to the other cylinder gaps (31) of the same transfer cylinder (25, 26) in the circumferential direction by approximately 180 .
24. A printing unit according to any of claims 17 to 19, in which the forme cylinder of each pair of cylinders has a plurality of cylinder gaps that extend in the axial direction in sections along the forme cylinder in such a way that, when viewed in the circumferential direction, at each axial position of the forme cylinder there are two cylinder gaps, with at least two cylinder gaps of the forme cylinder that extend at the same axial position being staggered in relation to the other cylinder gaps of the same forme cylinder in the circumferential direction.
25. A printing unit according to claim 24, in which the respective transfer cylinder of each pair of cylinders has a plurality of cylinder gaps that extend in the axial direction in sections along the transfer cylinder in such a way that, when viewed in the circumferential direction, at each axial position of the transfer cylinder in each case there is only one single cylinder gap, with at least one cylinder gap of the transfer cylinder being staggered in relation to the other cylinder gaps of the same transfer cylinder in the circumferential direction.
26. A printing unit according to claim 25, in which at least one cylinder gap of the transfer cylinder is staggered in relation to the other cylinder gaps of the same transfer cylinder in the circumferential direction by approximately 180 or by approximately 120 or by approximately 90 .
27. A printing unit according to one or more of claims 17 to 26, in which the cylinder gaps (31) of the transfer cylinders (25, 26) have a width of 1 mm to 5 mm in the circumferential direction.
28. A printing unit according to one or more of claims 17 to 27, in which associated with the forme cylinder (23, 24) and the transfer cylinder (25, 26) of each pair of cylinders (21, 22) there are bearer rings (29) which roll off on each other with a pre-stress in the impression-on position, and in that the or each printing cylinder (27) does not have any bearer rings cooperating with the bearer rings of the respective transfer cylinders (25, 26).