DE102017203491B4 - Plate cylinder - Google Patents

Abstract

Plate cylinder (07) with a casing (28) and at least one channel (27) extending in the direction of an axis of the plate cylinder (07) and recessed in the casing (28), in which a clamping device (30) for clamping an edge (40) of a printing plate (31) is accommodated, wherein the clamping device (30) is adjustable in the circumferential direction of the plate cylinder (07) with the aid of a pressure hose (50) elongated in the direction of the axis, which extends between a contact surface (58) of the casing (28) and a contact surface (48) of the clamping device (30), wherein the width (b1; b2) of a contact region (56) measured in section transverse to the axis, in which the pressure hose (50) touches one of the contact surfaces (58; 48), is smaller at a given pressure of the pressure hose (50) in a central section (53) of the pressure hose (50) than in the sections lying on either side of the central section (53). near-end sections (54) of the pressure hose (50), wherein at least one of the contact surfaces (48; 58) is concave in longitudinal section.

Description

The invention relates to a plate cylinder according to the features of claim 1.

Such a plate cylinder and such a sheet-fed printing machine are from the WO 2016/146461 A2 known. In this known plate cylinder, a rear clamping device, which clamps a rear edge of a printing plate mounted on the cylinder jacket, ie the edge that lags behind in relation to the direction of rotation of the plate cylinder during printing, is adjustable in the circumferential direction of the cylinder with the help of a pressure hose that extends between the contact surfaces of the clamping devices and the cylinder jacket. By adjusting the pressure plate, it is firmly clamped to the cylinder jacket and to a certain extent also stretched in the circumferential direction of the plate cylinder.

In practice, it turns out that this stretching is often greater in the middle of the printing plate than at its edges, which extend in the circumferential direction of the plate cylinder. The consequence of such uneven stretching is that a straight line that extends parallel to the rear edge of the printing plate in the printed image is printed as a curved line.

EN 10 2008 023 728 A1 highlights the problem that certain substrates can be deformed during printing and, in particular, have a tendency to stretch when they absorb moisture. If a leading transverse edge of a sheet is clamped along its entire length, the sheet is prevented from stretching along that transverse edge. Areas of the sheet following the leading transverse edge may stretch in the transverse direction, but at the same time the forces generated when the sheet passes through a printing nip counteract the transverse stretch, so that instead of stretching evenly lengthwise and crosswise, the sheet is shear deformed and the trailing transverse edge assumes a concave curvature. This deformation leads to registration errors when the sheet passes through another printing nip.

The EN 10 2007 047 842 B3 and the EN 10 2007 047 892 B4 reveal plate clamps using a hose. Tension in the circumferential direction is not provided.

The invention is based on the object of creating a plate cylinder, wherein a different clamping force in the circumferential direction is possible over a width of the printing plate.

The object is achieved according to the invention by the features of claim 1.

The advantages that can be achieved with the invention are in particular that it is possible, with the help of the pressure hose, to exert a tensioning force that is proportional to the width of the contact area and not evenly distributed along the channel on a printing plate mounted on the cylinder, e.g. forme cylinder, in particular plate cylinder. This makes it possible, on the one hand, to prevent uneven stretching of the printing plate across its width and the resulting distortion of the printed image. On the other hand, the printing plate can also be stretched differently across its width to adapt to an existing deformation of a sheet to be printed on it in order to minimize registration errors when printing the sheet.

A further advantage of the plate cylinder is that by setting different pressures in the chambers of the tube, it is possible to adjust the distribution of the tensile force exerted on the printing plate along its edge depending on the stretching behavior of the printing substrate used.

A variable width of the contact area can be achieved in different ways. One of these ways is to use a pressure hose whose circumference is smaller in the middle section than in the outer sections, in other words a waisted pressure hose.

Since the production of such a waisted pressure hose is complex, another approach is preferred, namely to make at least one of the contact surfaces concave in the longitudinal section.

This enables the use of a pressure hose that can be inexpensively prefabricated with a constant cross-section, e.g. as a continuous product, and can be closed at its ends. These closed ends will generally take on a convex, curved shape due to the pressure inside the pressure hose, so that the width of the contact area decreases towards the outside in the area of these ends. However, these areas should only make up a small proportion of the total length of the pressure hose; typically, the pressure hose should have a constant circumference over at least 80% of the length of the contact area when depressurized.

In order to be able to stretch the printing plate more along its edges running in the direction of sheet travel than in the middle, the clamping device should be flexible to a certain extent. For this purpose, the clamping device can comprise several pairs of inner and outer clamping jaws, which are axially successively attached to a common flexible bar.

This strip can simultaneously form the contact surface; this or generally a concave contact surface provided on the side of the clamping device enables a conversion of an existing printing press, in particular a sheet-fed printing press, without having to make changes to the jacket of the plate cylinder.

Forming a concavity in an elongated strip that extends over a large part of the length of the strip is complex and expensive in terms of manufacturing technology. Therefore, when manufacturing a new printing machine, it is preferable if the concave contact surface is provided on the side of the casing.

In a sheet-fed printing press with several printing units printing one after the other on a sheet, at least one printing unit should have a plate cylinder as described above.

The clamping device described above should be arranged in such a printing machine so that it clamps the rear edge of the printing plate.

The plate cylinders of such a printing machine can have contact surfaces with different concave shapes. For example, a contact surface of a first printing unit can be relatively concave to ensure even expansion of the printing plate, while in a subsequent second printing unit the concavity can be reduced to take account of any deformation of the sheets that occurs in the first printing unit. The contact surface of a third printing unit can, however, be more concave than that of the second printing unit to compensate for any deformation of the sheets that occurs when they pass through the second printing unit.

If the contact surfaces are formed on interchangeable components, in particular strips, as mentioned above, the plate cylinders of the various printing units can otherwise be identical in construction.

Embodiments of the invention are illustrated in the drawings and are described in more detail below.

• 1 einen schematischen Schnitt durch eine Bogendruckmaschine;
• 2 einen schematischen Schnitt durch ein Druckwerk der Bogendruckmaschine;
• 3 ein Detail eines Plattenzylinders des Druckwerks in einem ersten radialen Schnitt;
• 4 einen Druckschlauch des Plattenzylinders gemäß einer ersten Ausgestaltung der Erfindung;
• 5 einen zweiten radialen Schnitt gemäß der ersten Ausgestaltung;
• 6 eine Anlagefläche gemäß einer zweiten Ausgestaltung der Erfindung;
• 7 einen zweiten radialen Schnitt gemäß der zweiten Ausgestaltung;
• 8 einen zweiten radialen Schnitt gemäß einer dritten Ausgestaltung;
• 9 einen Schnitt entlang der Ebene IX - IX der 8;
• 10 einen zu 9 analogen Schnitt gemäß einer vierten Ausgestaltung.

Show it:

• 1 a schematic section through a sheet-fed printing press;
• 2 a schematic section through a printing unit of the sheet-fed printing press;
• 3 a detail of a plate cylinder of the printing unit in a first radial section;
• 4 a pressure hose of the plate cylinder according to a first embodiment of the invention;
• 5 a second radial section according to the first embodiment;
• 6 a contact surface according to a second embodiment of the invention;
• 7 a second radial section according to the second embodiment;
• 8th a second radial section according to a third embodiment;
• 9 a section along the plane IX - IX of the 8th ;
• 10 one to 9 analogous cut according to a fourth embodiment.

In the 1 The illustrated printing press, in particular a sheet-fed printing press, comprises a sheet feeder 01, a belt table 02, a sheet system 03 and a sheet delivery 04. Between the sheet system 03 and the sheet delivery 04, so-called units 05; 06 are arranged, which are designed, for example, as a printing unit, coating unit, calibration unit or in another suitable manner. 1 shows two printing units 05 and a varnishing unit 06 as an example; further printing and varnishing units not shown in the figure can be provided between the printing units 05 and the varnishing unit 06. The printing units 05 shown in the figure each print different colors, in particular printing ink on the same side of the sheets passing through them, and the varnishing unit 06 applies a varnish layer to the same side.

Both printing and varnishing units 05; 06 use exchangeable plates 31, in particular printing plates 31 or varnishing plates 31, in particular letterpress plates 31, which are mounted on a rotating cylinder 07, e.g. forme cylinder 07, in particular plate cylinder 07 of unit 05; 06, and whose surface is structured so that parts of the surface transfer printing ink or varnish to the passing sheets and other parts do not. The following description only deals with the clamping of a printing plate 31 on the plate cylinder 07 of a printing unit 05. It is also possible to transfer the mounting of the plate 31 to a varnishing unit 06 or other devices that use cylinders 07 with exchangeable plates 31.

2 shows one of the printing units 05 in a schematic section. The printing unit 05 is divided into a superstructure module 08 and a substructure module 09. The superstructure module 08 comprises in particular the plate cylinder 07, an inking unit 10, a dampening unit 11, a printing plate changer 12 and a cylinder 13, e.g. transfer cylinder 13, in particular blanket cylinder 13. The substructure module 09 has in particular a cylinder 14, in particular an impression cylinder 14, which together with the blanket cylinder 13 forms a printing nip 15, and a transfer drum 16 for the further transport of a sheet printed in the printing nip 15 to a subsequent printing unit 05, the coating unit 06 or the sheet delivery 04.

Deviating from the representation of the 1 and 2 the impression cylinder 14 can be replaced by a second blanket cylinder 13, which in turn cooperates with a second plate cylinder 07 in order to print on both sides of a sheet as it passes through the printing nip 15.

The inking unit 10 can be designed as a short inking unit, as a ductor inking unit or in another suitable way. If designed as a ductor inking unit, the inking unit 10 comprises at least one ink fountain 17 with at least one roller 18, e.g. ink fountain roller 18, roller 19, e.g. ink unit rollers 19 and in particular an ink ductor 20 which oscillates between the ink fountain roller 18 and a first inking unit roller 19. Among the inking unit rollers 19 there are driven rollers 21, e.g. ink distribution rollers 21 (shown in hatched lines) and rollers 22, e.g. ink unit rollers 22, which are driven by friction from the ink distribution rollers 21. At least one roller 23, e.g. B. ink application roller 23 is provided. In this embodiment, four ink application rollers 23 are provided.

In the direction of rotation of the plate cylinder 07, a roller 25, e.g. a dampening roller 25, is optionally arranged in front of the ink form rollers 23. This is assigned to the dampening unit 11, which is intended for applying dampening liquid to the surface of the printing plate 31. A switchable roller 26, e.g. a bridge roller 26, can be provided between a first ink form roller 23 in the direction of rotation of the plate cylinder 07 and the dampening roller 25. This enables a functional connection between the dampening unit 11 and the inking unit 10. This allows several operating modes to optimize the dampening liquid supply.

A cylindrical shell 28 of the plate cylinder 07 is interrupted by at least one channel 27 extending in the axial direction, in which clamping devices 29; 30 for clamping a printing plate 31 onto the circumference of the plate cylinder 07 are arranged.

The printing plate changer 12 contains a stack of these printing plates 31. In order to mount one of the printing plates 31 onto the plate cylinder 07, a lock at a lower end of the printing plate changer 12 releases the printing plate 31 located at one end of the stack, so that it slides downwards until its front edge 36 is against the 2 in a position ready for recording, hits the clamping device 29 of the plate cylinder 07 and is clamped thereto.

The plate cylinder 07, together with the printing plate 31 clamped by the clamping device 29, is then rotated counterclockwise as indicated by an arrow 37. The printing plate 31 is progressively pulled out of the printing plate changer 12 and, as it passes through a gap 38 between the plate cylinder 07 and a pressure roller 39, is pressed firmly against the casing 28 of the plate cylinder 07. Shortly before the rear edge 40 of the printing plate 31 reaches the gap 38, it lies so close to the inner clamping jaws 35 of the rear clamping device 30 that its outer clamping jaws 34, when pivoted against the inner clamping jaws 35, grasp this rear edge 40 and the rear edge 40 is clamped in the rear clamping device 30.

3 shows a schematic cross-section through the channel 27 of the plate cylinder 07. The edges 36; 40 of the printing plate 31 are held on the clamping devices 29; 30. The clamping devices 29; 30 here each comprise pairs of outer clamping jaws 32; 34 and inner clamping jaws 33; 35, wherein the outer clamping jaws 32; 34 are each pivotable or radially movable about an axis parallel to the axis of rotation of the plate cylinder 07 in order to press an edge 36 or 40 of the printing plate 31 onto the inner clamping jaws 33 or 35.

The clamping device 29 is mounted on a side wall 41 of the channel 27.

On a bottom 42 of the channel 27, rails 43 extending in the circumferential direction, e.g. in the form of T-profiles, are arranged, which engage in an undercut groove of the clamping device 30 and on which the rear clamping device 30 is movably guided.

The rear clamping device 30 comprises several, preferably three, pairs of clamping jaws 34; 35, which abut successively in the axial direction along the channel 27 on a component 47, in particular a strip 47.

At least one spring 45 is supported on a projection 44 protruding from the floor 42, which presses the clamping device 30 against a second side wall 46 of the channel 27; preferably, a spring 45 acting on the clamping jaw 35 is provided for each inner clamping jaw 35 of the clamping device 30. An undercut is formed in the side wall 46, into which the strip 47 of the clamping device 30 engages. A pressure hose 50 extends along the channel 27 between a contact surface 48 of the strip 47 and an opposite wall 49 of the undercut. By applying compressed air to the pressure hose 50 after the rear edge 40 has been clamped in the clamping device 30, the clamping device 30 is pressed away from the side wall 46 against the force of the spring 45, and the pressure plate 31 is pulled taut so that it rests against the casing 28 over its entire surface.

The pressure hose 50 has flexible but non-stretchable walls, e.g. made of a flexible plastic reinforced by an embedded fabric. A connection piece 51 is used for the inlet and outlet of compressed air. The circumference of the pressure hose 50 increases from a middle section 53, in particular from the middle 53 to its longitudinal ends 52 and reaches a maximum in a section 54 near the end, in particular in a plane 54 shortly (less than 20 mm) in front of the longitudinal ends 52. 4 shows the pressure hose 50 unrealistically shortened, so that the increase in circumference from the center 53 to the levels 54 is more clearly visible than in reality. Along the pressure hose 50, the outlines of three inner clamping jaws 35 of the clamping device 30 are shown, with which the pressure hose 50 interacts via the bar 47. While the clamping device 30 extends over the entire length of the channel 27, the pressure hose 50 cannot rest against the bar 47 over this entire length, since the connecting piece 51 and the tips 55 extending between the level 54 and the adjacent longitudinal end 52, narrowing towards the longitudinal end 52 and not touching the bar 47 or at most over a negligibly small area must also find space in the channel 27.

A flat contact area 56 of the pressure hose 50, which rests on the bar 47, therefore lies between the three inner clamping jaws 35 only over a part of their axial extension.

The cutting plane of the 3 crosses the pressure hose 50 near one of the planes 54, in an area where its circumference is maximum. The pressure hose 50 almost completely fills the space between the strip 47 and the wall 49 and rests against both of them at a width b1. The cutting plane of the 5 runs parallel to that of the 3 through the middle 53 of the pressure hose 50. Due to the smaller circumference there, the pressure hose 50 only fills the gap here over part of its height and rests against the bar 47 and the wall 49 over a width b2 that is smaller than the width b1. The force with which the pressure hose 50 drives the bar 47 away from the wall 49 per unit length is proportional to this width and is consequently greater at the longitudinal ends 52 of the pressure hose 50 than in the middle 53. The difference between the widths b1; b2 is dimensioned such that each inner clamping jaw 35 is opposite an equal area portion of the contact area 56. The same pressure thus acts on each clamping jaw 35. Although a different deflection of the clamping jaw pairs 34, 35 would be possible if the bar 47 were to bend, all clamping jaw pairs 34, 35 are deflected to the same extent. As a result, the pressure plate 31 is subjected to a constant tensile load over its entire edge 40, so that the edge 40 remains straight even under the tensile load.

6 shows a perspective view (also compressed in the axial direction) of the clamping device 30 according to a second embodiment of the invention. On the side of the bar 47 facing away from the viewer, as in the first embodiment, three pairs of clamping jaws 34; 35 are mounted one after the other in the axial direction. The contact surface 48 of the bar 47 facing the viewer is concave.

In this embodiment, the pressure hose 50 has a constant circumference between two levels 54, the distance between which makes up at least 80% of its total length. Such a pressure hose 50 can be manufactured inexpensively by first producing an endless hose, e.g. by extrusion, and cutting it into pieces of the required length, and then sealing these pieces at their ends or providing them with a connection piece 51.

Due to the concavity of the contact surface 48 of the bar 47, the pressure hose 50 must be 7 shown, in the middle 53 to a greater thickness than at the level of the planes 54 in order to be able to exert pressure on the strip 47 and the wall 49. Despite the constant circumference, this has the consequence that, as in the first embodiment, the width b2 of the contact area 56 in the middle 53 of the pressure hose 50 is smaller than the width b1 at the level of the planes 54 near the ends.

8th shows one to 5 and 7 analogous section along the center 53 of the pressure hose 50 according to a third embodiment of the invention, and 9 a cut along the 8th with IX - IX designated plane through an outer surface 57 of the shell 28 and its channel 27 bounding wall 49 and in which the cutting planes of the 3 and 8th designated III - III or VIII - VIII. In this embodiment, the contact surface 48 of the strip 47 facing the pressure hose 50 is flat, instead the wall 49 opposite the strip 47 has a concave contact surface 58. Here too, the width b2 of the contact area 56 in the middle 53 of the pressure hose 50 is smaller than the width b1 at the level of the planes 54 near the end.

Such a concave contact surface 58 can be manufactured with relatively little effort, because if the channel 27 or its undercut is milled out of the material of the casing 28 or a surface formed by metal casting is smoothed in order to create the contact surface 58, the associated work effort for the concave contact surface 58 is at most insignificantly higher than the creation of a flat contact surface.

As an example, only the case was described above in which the variable width b1; b2 of the contact area 56 is dimensioned such that bending of the strip 47 is avoided and the tensile load is evenly distributed along the edge 40 of the pressure plate 31.

In order to combat registration errors caused by the deformation of the sheets during printing explained above, the change in the circumference of the pressure hose 50 or the concavity of the contact surface 48 or 58 can also be dimensioned such that the printing plate 31 of a second or subsequent printing unit 05 is stretched more along its edges 36; 40 oriented in the direction of sheet travel than in the middle between them.

10 shows a longitudinal section of the clamping device 30 according to a further embodiment of the invention. The pressure hose 50 is divided into as many chambers 59 as the clamping device 30 has clamping jaws 35, and behind each clamping jaw 35 there is a chamber 59. The chambers 59 can be directly adjacent to one another within a common casing or as in 10 shown spaced apart from one another. Each chamber 59 has its own connection piece 51, via which it can be pressurized with compressed air, so that different pressures can be set in the chambers 59. In the case shown here, the connection pieces 51 each comprise a shut-off valve 60 and are connected to a common distributor 61. For example, after the middle chamber 59 has been brought to a target pressure, its shut-off valve 60 is closed as shown while those of the side chambers 59 remain open, and the pressure in the distributor 61 is changed, an equal pressure can be set in the side chambers 59, which deviates from that of the middle chamber 59 by an arbitrarily definable amount. This makes it possible to modify the expansion of the printing plate 31 along the edge 40 as required, for example to adapt it to different expansion behavior of different printing materials.

List of reference symbols

01

Sheet feeder

02

Belt table

03

Arch system

04

Sheet delivery

05

Work, printing works

06

Plant, paint shop

07

Cylinder, forme cylinder, plate cylinder

08

Superstructure module

09

Substructure module

10

Farbwerk

11

Dampening system

12

Printing plate changer

13

Cylinder, transfer cylinder, blanket cylinder

14

Cylinder, impression cylinder

15

Printing gap

16

Transfer drum

17

Paint box

18

roller, ink fountain roller

19

roller, inking roller

20

Color lifter

21

Roller, ink roller

22

roller, inking roller

23

Roller, ink application roller

24

-

25

Roller, dampening roller

26

Roller, bridge roller

27

channel

28

Coat

29

Clamping device, front

30

Clamping device, rear

31

plate, printing plate, lacquer plate, letterpress plate

32

Clamping jaw, outer

33

Clamping jaw, inner

34

Clamping jaw, outer

35

Clamping jaw, inner

36

Edge, front

37

Arrow

38

gap

39

Pressure roller

40

Edge, rear

41

Side wall

42

Floor

43

rail

44

head Start

45

Feather

46

Side wall

47

Component, strip

48

Contact surface

49

Wall

50

pressure hose

51

Connection piece

52

Longitudinal end

53

section, middle, middle

54

section, near-end, level

55

Tip

56

Contact area

57

Exterior surface

58

Contact surface

59

chamber

60

Shut-off valve

61

Distributor

b1

Width

b2

Width

Claims (7)

Plate cylinder (07) with a casing (28) and at least one channel (27) extending in the direction of an axis of the plate cylinder (07) and recessed in the casing (28), in which a clamping device (30) for clamping an edge (40) of a printing plate (31) is accommodated, wherein the clamping device (30) is adjustable in the circumferential direction of the plate cylinder (07) with the aid of a pressure hose (50) elongated in the direction of the axis, which extends between a contact surface (58) of the casing (28) and a contact surface (48) of the clamping device (30), wherein the width (b1; b2) of a contact region (56) measured in section transverse to the axis, in which the pressure hose (50) touches one of the contact surfaces (58; 48), is smaller at a given pressure of the pressure hose (50) in a central section (53) of the pressure hose (50) than in the sections lying on either side of the central section (53). near-end sections (54) of the pressure hose (50), wherein at least one of the contact surfaces (48; 58) is concave in longitudinal section. Plate cylinder after Claim 1 , characterized in that the clamping device (30) comprises several pairs of inner and outer clamping jaws (35; 34) which are fastened successively in the axial direction to a common flexible bar (47). Plate cylinder after Claim 1 or 2 , characterized in that the circumference of the pressure hose (50) in the middle section (53) is smaller than in the sections near the ends (54). Plate cylinder after Claim 1 , characterized in that the pressure hose (50) in the pressureless state has a constant circumference over at least 80% of the length of the contact region (56). Plate cylinder after Claim 1 or 4 , characterized in that the concave contact surface (48) is provided on the side of the clamping device (30). Plate cylinder after Claim 1 or 4 , characterized in that the concave contact surface (58) is provided on the side of the casing (28). Plate cylinder according to one of the Claims 1 , 4 , 5 or 6 , characterized in that the concave contact surface (48) is formed on an exchangeable component (47).

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