Foil Transfer Unit Having a Material Application Device

Abstract

An apparatus, a method and a transfer foil for transferring a transfer layer onto a printing material in a transfer unit. In order to avoid the adhesion, and simultaneously retain the flexibility of the transfer cylinder, it is proposed that the transfer unit has at least one material application device for applying friction-reducing material onto the transfer cylinder and/or the carrier foil reverse side. Furthermore, a transfer foil is proposed, the carrier foil of which has a rear-side coating of friction-reducing material. The friction-reducing material may be a fluid or powder.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a diagrammatic side view of a transfer unit having a material application device on the transfer cylinder;

FIG. 2 is a similar view of a transfer unit having a material application device on the transport path of the transfer foil; and

FIG. 3 is a sectional view taken through the structure of a transfer foil having an antiadhesion layer.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown a transfer unit for transferring a transfer layer onto a sheet 6. As is intended to be shown here, this transfer unit can be a printing unit of a printing press.

A transfer foil 1 is unwound from a foil supply roller and is guided around deflection rollers 2 along a transport path to a transfer nip 3. The transfer nip 3 is formed by an impression cylinder 5 and a blanket cylinder 4 which serves here as transfer cylinder. After it has passed through the transfer nip 3, the transfer foil 1 is fed back via a deflection roller 2 to a foil collecting roller.

A sheet 6 is likewise guided through the transfer nip 3 along a dedicated transport path. An adhesive layer in regions which has been applied to the sheet 6 in an application unit (disposed upstream, not illustrated) is situated on the sheet 6. The sheet 6 is then guided together with the transfer foil 1 through the transfer nip 3, and the transfer layer 12 of the transfer foil 1 is transferred to those regions of the sheet 6 which are coated with adhesive as a result of the contact pressure between the blanket cylinder 4 and the impression cylinder 5. Here, the transfer layer 12 is removed from the transfer foil 1 in the transfer nip 3.

In order to avoid adhesion of the transfer foil 1 on the blanket cylinder 4, a friction-reducing material is applied via a material application device 7 to the blanket cylinder 4, that is to say to its surface. This friction-reducing material can be, for example, French chalk powder. It can also be a fluid, such as silicone oil, or a powder, as is preferred. This can be, for example, a mineral powder having a type designation KSL-K2 or an organic powder having the type designation KSL-S5 of the company KSL-Staubtechnik GmbH. Overall, it is desirable that the powder have grain sizes between 10 and 90 μm here, grain sizes in the range between 15 and 35 μm being preferred particularly.

Here, a powdering device such as has been described, for example, in German patent DE 197 51 383 B4 (cf. U.S. Pat. No. 6,413,580 B1) for the application of powder onto a sheet can be used as the material application device 7. The prior disclosures are herewith incorporated by reference.

As it is a printing unit which is used as transfer unit in the case which is described here, a plate cylinder 9 is situated in the vicinity of the blanket cylinder 4. This plate cylinder 9 is either thrown off the blanket cylinder 4 or there is an intermediate space 10 between the printing plate cylinder 9 and the blanket cylinder 4 as a result of a printing plate not being used, that is to say no printing plate is clamped onto the printing plate cylinder 9. That is to say, the powder or in general the friction-reducing material which is applied via the material application device 7 cannot be transferred to the plate cylinder 9 by the blanket cylinder 4. It cannot therefore also pass into a dampening unit or inking unit of the printing unit. It is therefore also possible to provide the material application device 7 either in front of or after the intermediate space 10 in the circumferential direction of the blanket cylinder 4. Here, a corresponding position of the material application device 7 in front of the intermediate space 10 is shown with dashed lines.

In a further method, the printing unit which is shown here can also be used as a normal printing unit and not as a transfer unit. For this purpose, it is firstly necessary that no transfer foil 1 is guided through the transfer nip 3. This can be achieved by the transfer foil 1 being removed from the transfer unit. In order that no powder or no friction-reducing material can pass into the inking units or dampening units of the printing unit, it is necessary that the blanket cylinder is freed of residues of the friction-reducing material before the printing unit is started. This can take place via a washing device. In this case, a rubber blanket washing device 8 is provided which is provided at any desired location of the blanket cylinder 4. This rubber blanket washing device 8 can act, for example, via brushes or compressed air or via a cloth which acts on the surface of the blanket cylinder. Corresponding rubber blanket washing devices are disclosed, for example, in the European patents EP 715 956 B1 and EP 291 745 B1 (U.S. Pat. No. 4,867,064), and in German published patent application DE 102 44 218 A1 (cf. U.S. Pat. No. 6,732,652 B2). These documents are herewith incorporated by reference in their entirety, concerning the disclosures in relation to the embodiments of rubber blanket washing devices.

Furthermore, in order to prevent a corresponding friction-reducing material or powder passing into other regions of the printing press or the printing unit, an extraction device 17 is additionally provided here around the material application device 7. This extraction device 17 is shown only for one material application device 7, but can be provided in principle and should also be provided preferably in every possible position of the material application device 7.

FIG. 2 shows one alternative position of the material application device 7, the remaining elements corresponding substantially to those of FIG. 1. Identical elements are denoted here with identical designations.

In the case which is shown here, the carrier foil 1 is guided over two deflection rollers 2 for passage through the transfer nip 3. This is therefore naturally also possible for the case which is shown in FIG. 1. Overall, a very wide variety of guide means are possible for the carrier foil 1.

In the case which is shown in FIG. 2, the material application device, which is also preferably a powdering device, is not provided here in the vicinity of the blanket cylinder 4, but instead in the region of the transfer foil 1, that is to say in the region of the transport path of the transfer foil 1; to be precise, the material application device 7 is attached here in such a way that it applies the friction-reducing material to the rear side of the transfer foil, before the latter is guided through the transfer nip 3. Even if the material application device 7 is shown here without an extraction device 17, it is naturally possible and can also be provided that it is enclosed by an extraction device 17, in order also to avoid here that friction-reducing material passes from the region of the material application device into the air space within the printing unit.

In one alternative embodiment (not illustrated here), it is naturally also possible that material application devices 7 are provided both in the region of the transport path of the transfer foil 1 and in the region of the blanket cylinder 4.

For the case where the friction-reducing materials are applied to the rear side of the transfer foil 1, the latter is guided with these materials through the transfer nip 3. Here, the powder or the friction-reducing material then lies between the rear side of the transfer foil 1 and the blanket cylinder 4, and therefore reduces the friction between the blanket cylinder 4 and the transfer foil 1. It can occur here that friction-reducing material passes onto the blanket cylinder 4 and is collected here. In order to avoid, in a subsequent offset printing process, residues of the friction-reducing material passing onto the printing plate cylinder 9, a rubber blanket washing device 8 is also provided here, as has already been described in FIG. 1.

FIG. 3 shows the structure of a transfer foil 1 according to the invention. The transfer foil 1 is constructed from a carrier foil 11, to which first of all a transfer layer 12 is applied on the front side, which transfer layer 12 can also have an adhesion promoter 15 on its surface. The transfer layer 12 can be constructed in general in different ways; it serves for being applied to a printing material and highlighting a region. Here, this is the customary cold foil transfer process. The transfer foil 1 can be configured here in such a way that it has, as transfer layer 12, a release layer 13 and a metal layer 14, as in the example here which is shown. Here, the metal layer 14 can also comprise, in particular, a varnish which colors the metal, or the metal of this layer leads to a metallic gloss of a varnish layer.

In order then to reduce the friction between a blanket cylinder 4 and the transfer foil 1, there is provision for an antiadhesion layer to be provided on the rear side of the transfer foil 1, that is to say on the rear side of the carrier foil 11. This antiadhesion layer comprises friction-reducing material and ensures the above-described reduction in the friction between the transfer foil 1 and the blanket cylinder 4. This antiadhesion layer 16 can be, for example, a powder coating which is also applied, in particular, within a printing unit or a transfer unit directly onto the rear side of the transfer foil 1. There can also be provision for the transfer foil 1 to be manufactured in such a way that it already has a rear-side antiadhesion layer 16. This can then be, for example, PTFE or another friction-reducing layer.

As a result of the embodiments of the transfer units or the transfer foil which are shown here, it is possible to load the transfer foil 1 directly or a transfer cylinder surface, that is to say the surface of the blanket cylinder 4, with a friction-reducing material, such as powder, in order thus to reduce the friction between the transfer cylinder, that is to say the blanket cylinder 4, and the transfer foil 1. Adhesion between the blanket cylinder 4 and the transfer foil 1 is reduced as a result. The adhesion can no longer take place, as in the known prior art. Embossing of structures into the transfer foil 1 or the sheet 6 can also not occur as a result of the smooth surface of the applied material layer.

Here, there is provision, in particular, for a conventional rubber blanket to be used. This rubber blanket is fastened to the surface of the blanket cylinder 4 and should have substantially a smooth surface. In particular, it can also be elastic. It is also possible that although a smooth surface is preferred as surface of the blanket cylinder 4, this surface is intended to be as nonelastic and hard as possible. This can be achieved, for example, by a metal plate. For example, a rubber blanket of the company I.M.C. GmbH Munich having the commercial name Perfect Dot® MX can be used as standard rubber blanket. This has a preferred smooth surface structure and does not lead to any impairments, that is to say to any embossments in the sheet 6. High quality coating of the printed sheet 6 can therefore be carried out, the release of the transfer layer 12 of the transfer foil 1 being assisted in an improved manner as a result of the reduced frictional force between the blanket cylinder 4 and the transfer foil 1, and a smooth structure of the transfer layer being achieved on the sheet 6.

Claims

1. An apparatus for transferring a transfer layer from a front side of a carrier foil onto a printing material, the carrier foil and the transfer layer together forming a transfer foil, comprising: at least one transfer unit for transferring the transfer layer onto the printing material;said transfer unit including at least one transfer cylinder for transferring the transfer layer; andsaid transfer unit including at least one material application device disposed to apply friction-reducing material onto at least one of said transfer cylinder and a reverse side of the carrier foil.

2. The apparatus according to claim 1, wherein said material application device is disposed in a region of said transfer cylinder, and configured to apply the friction-reducing material to a surface of said transfer cylinder.

3. The apparatus according to claim 1, wherein the transfer foil is moved along a transport path to said transfer cylinder and said material application device is disposed in a region of the transport path of the transfer foil, positioned upstream of the transfer cylinder in a transport direction, for applying the friction-reducing material to a rear side of the transfer foil.

4. The apparatus according to claim 1, wherein said material application device is formed in a cassette removably disposed in said transfer unit.

5. The apparatus according to claim 1, wherein said material application device has at least one of the elements selected from the group consisting of a bush, a cloth, and an inflating element configured to apply the friction-reducing material to at least one of a surface of the transfer cylinder and the reverse side of the carrier foil.

6. The apparatus according to claim 5, wherein said material application device includes an extraction device for extracting residues of the friction-reducing material.

7. The apparatus according to claim 1, which comprises a washing device for washing a surface of said transfer cylinder.

8. The apparatus according to claim 7, wherein said washing device is a rubber blanket washing device.

9. The apparatus according to claim 8, wherein said rubber blanket washing device includes a first washing agent circuit for a first washing agent for cleaning the surface of the transfer cylinder of residues of the friction-reducing material and a second washing agent circuit for a second washing agent for cleaning the surface of the transfer cylinder of ink residues of an offset printing process.

10. The apparatus according to claim 1, wherein said transfer unit is a unit selected from the group consisting of a printing unit, a varnishing unit, and a modular unit of a printing press.

11. The apparatus according to claim 10, wherein said transfer cylinder is a blanket cylinder, and a plate cylinder which is thrown onto said blanket cylinder for offset printing is provided without printing plates or in a thrown-off position from the blanket cylinder.

12. The apparatus according to claim 1, wherein the friction-reducing material is a fluid or a powder.

13. The apparatus according to claim 1, wherein the material application device is a powdering device of a printing press.

14. The apparatus according to claim 13, wherein the friction-reducing material is a powder having a grain size in a range from 10 μm to 90 μm.

15. The apparatus according to claim 14, wherein the powder has a grain size in a range from 15 μm to 35 μm.

16. A method of transferring a transfer layer from a front side of a carrier foil onto a printing material, the carrier foil and the transfer layer together forming a transfer foil, the method which comprises: feeding the transfer foil to a transfer cylinder;applying a friction-reducing material for reducing an adhesion between the carrier foil and a surface of the transfer cylinder to at least one of a rear side of the carrier foil and the surface of the transfer cylinder; andtransferring sections of the transfer layer onto the printing material by detaching the transfer layer in sections from the carrier foil.

17. The method according to claim 16, which comprises applying the friction-reducing material by way of a method selected from the group consisting of brushing on, spraying on, rolling on, doctoring on, and applying with a cloth.

18. The method according to claim 16, which comprises extracting air that is contaminated with friction-reducing material from a region of application.

19. The method according to claim 16, which comprises employing a blanket cylinder of a printing unit as the transfer cylinder.

20. The method according to claim 19, which comprises setting a plate cylinder that is associated with the blanket cylinder to be without contact with respect to the blanket cylinder, at least during the transferring step.

21. The method according to claim 20, which comprises throwing off the plate cylinder from the blanket cylinder and/or operating the plate cylinder without plates.

22. The method according to claim 16, which comprises cleaning the surface of the transfer cylinder of residues of the friction-reducing material by way of a washing device.

23. The method according to claim 22, which comprises washing with a rubber blanket washing device.

24. The method according to claim 16, which comprises cleaning the surface of the transfer cylinder of residues of the friction-reducing material with a first washing agent from a first washing agent circuit and cleaning the surface of the transfer cylinder of ink residues from an offset printing process with a second washing agent from a second washing agent circuit.

25. The method according to claim 16, which comprise employing a fluid or a powder as the friction-reducing material.

26. The method according to claim 16, which comprises applying the friction-reducing material with a powdering device of a printing press.

27. The method according to claim 25, which comprises employing silicone oil as the friction-reducing material.

28. The method according to claim 25, which comprises powdering with a powder selected from the group consisting of French chalk, mineral powder, and organic powder.

29. The method according to claim 25, which comprises powdering with a powder having a grain size in a range from 10 μm to 90 μm.

30. The method according to claim 29, wherein the powder has a grain size in a range from 15 μm to 35 μm.

31. A transfer foil, comprising: a carrier foil having a front side and a rear side;a release layer applied to the front side of said carrier foil, and a transfer layer carried on said release layer; anda coating of friction-reducing material applied on said rear side of said carrier foil;wherein said carrier foil and said transfer layer are configured for a transfer method in which the transfer layer, or segments thereof, is transferred from said carrier foil onto a printing material.

32. The transfer foil according to claim 31, wherein said friction-reducing material is PTFE or a powder coating.

33. The transfer foil according to claim 31, wherein said front side of said carrier foil carries said release layer, a metal layer, and a layer comprising an adhesion promoter for entering into a contacting connection with an adhesive layer on a printing material.