EP2686168B1 - System consisting of a printing cylinder and a printing blanket or printing plate and manufacturing method - Google Patents

Description

• einem Druckzylinder, der einen Spalt in axialer Richtung aufweist,
• einem Drucktuch oder einer Druckform mit einer Deckschicht, die eine nach radial außen gerichtete Druckschicht enthält, und mit einer Tragschicht, wobei das vorlaufende und das nachlaufende Ende der Tragschicht frei von der Deckschicht ist,

wobei das vorlaufende Ende und das nachlaufende Ende der Tragschicht derart in dem Spalt des Druckzylinders eingespannt sind, dass ein in axialer Richtung des Druckzylinders verlaufender Kanal zwischen den umlaufenden Enden der Deckschicht verbleibt.The invention relates to a system consisting of:

• a printing cylinder having a gap in the axial direction,
• a blanket or printing form having a cover layer containing a radially outwardly directed printing layer and a backing layer, the leading and trailing ends of the backing layer being free of the cover layer,

wherein the leading end and the trailing end of the support layer are clamped in the gap of the printing cylinder such that a channel extending in the axial direction of the printing cylinder remains between the circumferential ends of the cover layer.

The invention further relates to a method for producing such a system.

A system of the type mentioned has long been known from the prior art. Such systems are used both in offset printing on blankets and metal blankets as well as in high-pressure forms such. Flexographic printing applications in which the blanket has a comparatively high flexibility or compressibility.

An advantage of the system is that the blanket or printing form can first be fabricated as a two-dimensional flat surface with a beginning and an end. The production of such a blanket or such a printing form is possible in a simple manner, whereas the production of an endless printing cylinder is expensive.

The disadvantage of a system of the type mentioned is, however, to be seen in that after the clamping of the blanket or the printing forme on the printing cylinder remains a channel between the peripheral ends of the cover layer. In this channel impurities such as e.g. Collect paper dust or paint that may fall out of the channel during printing, which can damage the paper webs you are printing.

From the DE 103 07 382 A1 a system is known in which the channel is closed with an elastomer. In the system known from this document, the blanket is first made from a production cylinder. For this purpose, a support layer is first clamped on the production cylinder, on which the cover layer is attached. Thereafter, the remaining between the peripheral ends of the cover layer channel is closed with a curable elastomer. After curing, the blanket is cut in the region of the elastomer in the axial direction of the production cylinder and removed from the production cylinder. Finally, the printing blanket is clamped on the printing cylinder in such a way that the end faces of the elastomer are in contact with each other. The channel is thus closed on the printing cylinder. However, it should be noted that the production of the from the DE 103 07 382 A1 known blanket is expensive. In addition, between the peripheral ends of the cover layer of the blanket in the region of the channel due to the separation of the elastomer remains a narrow gap in which can collect impurities. Finally, it should be noted that the elastomer introduced into the channel is incompressible. If forces are thus applied in the radial direction to the printing blanket, then the elastomer can avoid these forces only in that it expands in the circumferential direction of the blanket. This leads to the initiation of unwanted forces in the circumferential direction of the blanket, which can be accompanied by a deterioration of the printed image.

The WO 2010/061413 A1 describes a typographic plate cylinder having a groove or nip for mounting a coating, which in turn has two flaps which, when bent and inserted into a groove or gap of the cylinder, form a gap in the coating. A completion member is provided which has an elongated member which is intended for insertion and which remains clamped in the gap without projecting radially from the coating, thereby obscuring the gap.

The invention has for its object to provide an optimized system of the type mentioned, in which no impurities can penetrate into the region of the cover layer of the blanket or the printing plate. The invention is further based on the object to provide a method for producing such a system.

The object is solved by the characterizing feature of claim 1. In this case, the complete filling of the channel takes place in such a way that the peripheral ends of the blanket or of the printing forme are non-positively connected with one another via the compressible material.

According to the independent claim 4, the object is further achieved in that after the drawing of the blanket or the printing forme on the printing cylinder, the remaining between the peripheral ends of the outer layer structure channel is completely filled with a compressible material according to its characterizing feature.

The advantage achieved by the invention can be seen in the fact that in the region of the printing layer, in particular in the channel, no impurities can penetrate. This is due to the fact that the channel is completely filled with a compressible material which frictionally connects the peripheral ends of the cover layer. Thus, neither in the compressible material, nor at the transitions from the compressible material to the cover layer are scratches in which contaminants can penetrate. Another advantage of the invention is that the system can be easily manufactured. In particular, it is not necessary to manufacture the blanket or the printing form on a separate production cylinder.

For producing a compressible material, various materials may be used as raw materials in combination with blowing agents. Suitable starting materials are preferably elastomeric materials such as EPDM, NBR, modified epoxy resins or silicone rubbers or elastomers based on Polyurethane or polyurea. Also, thermoplastics such as PE or PP can be used if they are compliant at the temperature of the application. As blowing agents, both chemical and physical blowing agents can be used. By physical blowing agents, for example, compressed gases (eg air, CO2 or CFC) or volatile hydrocarbons are understood. Azodicarbonamides, sulfonylhydrazides or hydrogencarbonates can be used as chemical blowing agents.

Preferably, a combination of polyuritan or polyureas or a combination of polyurethane and polyureas with microspheres is used.

The color of the material is preferably black, e.g. by the addition of carbon black, so that it can be lasered. By laser ablation, a print template can be created on a printing form.

According to the invention, the compressible material consists of a chemically curing material in which microspheres are embedded. The advantage is the fact that you can first fill the channel with the compressible material initially evenly and completely and the mass hardens only afterwards. Preferably, a chemically curing material is selected which requires a maximum of 15 minutes to cure, so closing the channel does not take too much time. The compressibility of the material is brought about by means of embedded microspheres, which enclose air.

Furthermore, the cover layer has a compressible intermediate layer, wherein in the chemically curing material so many microspheres are embedded that the compressibility of the intermediate layer corresponds to the compressibility of the chemically curing material. In order to achieve this, according to the invention so many microspheres are embedded in the chemically curing material that the density of the cured material with microspheres is 20% to 40% lower than the density of the cured material without microspheres. The advantage is that the Compressible intermediate layer containing the top layer of a blanket or a printing plate usual manner is formed homogeneously over the entire circumference of the blanket or the printing plate. This ensures that the printing blanket or printing form behaves homogeneously in all directions during a printing process. Any chemically curing materials may be used to form the invention. In particular, it is possible to use materials that cure by irradiation. According to one embodiment of the invention according to claim 2, however, the chemically curing material is an epoxy resin, which is composed of an epoxy resin and a curing agent, being used as the epoxy polymer blocks, which carry so-called epoxide groups at the end. For this example, the reaction products of bisphenol-A and epichlorohydrin can be used, which form a stable thermoset after mixing with the curing agent containing amino or mercapto. The advantage of the development is the fact that the curing reaction can be carried out at room temperatures in a two-component epoxy resin. Another advantage of this development is the fact that epoxy resins are easy to work with and cure quickly.

According to one embodiment of the invention according to claim 3, the support layer is formed as a metal foil. The advantage of this development is the fact that the blanket or the printing forme can be clamped reliably on the impression cylinder with the aid of a metal foil, since the metal foil can absorb forces in the circumferential direction.

According to one embodiment of the invention according to claim 5, the compressible material is formed as a two-component epoxy resin, wherein at least one component of the epoxy resin contains microspheres. The advantage of this development is the fact that two-component epoxy resins cure quickly, so that the channel between the peripheral ends of the cover layer can be quickly closed.

According to one embodiment of the invention according to claim 6, the edges of the peripheral ends of the cover layer are sealed prior to introduction of the compressible material with an elastomer. The advantage of this development is the fact that the edges of the cover layer are completely sealed with the elastomer and thus the compressible material needs to bind exclusively to a single substance, namely the elastomer. The elastomer may be selected to provide a particularly strong bond between the compressible material and the elastomer. This leads to a particularly strong frictional connection between the peripheral ends of the cover layer.

Fig. 1

ein System, bestehend aus einem Druckzylinder und einem Drucktuch oder einer Druckform im Querschnitt, und

Fig. 2

ein System, bestehend aus einem Druckzylinder und einem Drucktuch oder einer Druckform in Draufsicht.

An embodiment and further advantages of the invention will be explained in connection with the following figures. It shows:

Fig. 1

a system consisting of a printing cylinder and a blanket or a printing plate in cross section, and

Fig. 2

a system consisting of a printing cylinder and a blanket or a printing plate in plan view.

Fig. 1 shows a system 2, consisting of a printing cylinder 4 and a blanket 6 or a printing plate 6 in cross section. The printing cylinder 4 has a gap 8 which extends in the axial direction of the printing cylinder 4. The printing blanket 6 or the printing forme 6 has a cover layer 10, which in the exemplary embodiment shown consists of a printing layer 12 directed radially outward, a fabric layer 14 and a compressible layer 16. The topcoat may optionally contain additional layers. The cover layer 10 is connected to a support layer 18, which is preferably formed as a metal foil.

The leading end 20 and the trailing end 22 of the support layer 18 are free of the cover layer 10. With the help of the ends 20 and 22, the blanket 6 and the printing plate 6 in a conventional manner in the axially extending gap 8 of the printing cylinder 4 clamped. After clamping the blanket 6 and the printing plate 6 on the printing cylinder 4 remains between the peripheral ends 24 and 26 of the cover layer 10, a channel 28 which extends in the axial direction of the printing cylinder 4. The channel 28 is completely filled with a compressible material 30. Preferably, the filling of the channel 28 by means of the compressible material 30 is such that filling of the channel 28 in the radial direction is as thick as the cover layer 10 and the radially outward surface of the compressible material 30 with the radially outwardly facing surface of the print layer 12 forms a plane, as it does in the Fig. 1 is shown. The blanket 6 and the printing plate 6 then has the same thickness everywhere. This can be achieved, for example, in that the channel 28 is first filled to the extent that the compressible material 30 is beyond the pressure layer 12 and the excess compressible material 30 is abraded.

The compressible material 30 consists of a chemically curing material in which microspheres are embedded. Preferably, the chemically curing material 30 is a two-part epoxy resin. In the chemically curing material so many microspheres are embedded that the compressibility of the material 30 corresponds to the compressibility of the compressible layer 16. It is possible to seal the edges of the circumferential ends 24, 26 of the cover layer 10 of the blanket 6 and the printing plate 6 with an elastomer prior to introducing the compressible material 30 into the gap 8. For a better connection of the compressible material to the edges of the peripheral ends 24, 26 is achieved.

Fig. 2 shows the system 2 with the gap 8, which is filled with the compressible material 30, in plan view.

LIST OF REFERENCE NUMBERS (Part of the description)

2

system

4

pressure cylinder

6

Blanket or printing form

8th

gap

10

topcoat

12

print layer

14

fabric layer

16

compressible layer

18

base course

20

leading end

22

trailing end

24

The End

26

The End

28

channel

30

compressible material

Claims (6)

1. System (2), consisting of:

   - an impression cylinder (4) which has a gap (8) in the axial direction,

   - a printing blanket (6) or a printing forme (6) with a covering layer (10) which comprises a radially outwardly directed printing layer (12), and with a supporting layer (18) which comprises a leading end (20) and a trailing end (22), the leading end (20) and the trailing end (22) of the supporting layer (18) being free from the covering layer (10),

   the leading end (20) and the trailing end (22) of the supporting layer (18) being clamped in the gap (8) of the impression cylinder (4) in such a way that a channel (28) which runs in the axial direction of the impression cylinder (4) remains between circulating ends (24, 26) of the covering layer (10),
   the channel (28) being filled completely with a compressible material,
   the compressible material consisting of a chemically curing material, into which microspheres are embedded, and
   the covering layer (10) having a compressible intermediate layer (16),
   characterized in that so many microspheres are embedded into the chemically curing material of the channel (28) that the density of the cured material of the channel (28) is from 20% to 40% lower than the density of the cured material of the channel (28) without microspheres.
2. System (2) according to Claim 1, characterized in that the chemically curing material is an epoxy resin.
3. System (2) according to either of Claims 1 and 2, characterized in that the supporting layer (18) is a metal foil.
4. Method for producing a system (2) consisting of:

   an impression cylinder (4) which has a gap (8) in the axial direction,

   a printing blanket (6) or a printing forme (6) with a covering layer (10) which comprises a radially outwardly facing printing layer (12), and with a supporting layer (18) which comprises a leading end (20) and a trailing end (22), the leading end (20) and the trailing end (22) of the supporting layer being free from the covering layer, and

   the leading end (20) and the trailing end (22) of the supporting layer (18) being clamped into the gap (8) of the impression cylinder (4) in such a way that a channel (28) which runs in the axial direction of the impression cylinder (4) remains between circulating ends (24, 26) of the covering layer (10),

   the remaining channel (28) being filled completely with a compressible material,

   the compressible material consisting of a chemically curing material, into which microspheres are embedded, and

   the covering layer (10) having a compressible intermediate layer (16),

   characterized

   in that so many microspheres are embedded into the chemically curing material of the channel (28) that the density of the cured material of the channel (28) is from 20% to 40% lower than the density of the cured material of the channel (28) without microspheres.
5. Method according to Claim 4, characterized in that the compressible material is configured as a two-component epoxy resin, and in that at least one component of the epoxy resin comprises microspheres.
6. Method according to either of Claims 4 and 5, characterized in that the end faces of the circulating ends (24, 26) of the covering layer (10) are sealed with an elastomer before the introduction of the compressible material.

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