Foil transfer device

Abstract

A foil transfer device comprising a counter-pressure cylinder (7) for transporting the substrate (2) and a pressure cylinder (6) for pressing the foil web (8) against the substrate (2) on the counter-pressure cylinder (7) in a transfer gap (4) formed by the pressure cylinder (6) and the counter-pressure cylinder (7), wherein a blowing device (15) blows into a discharge gusset (14) of the transfer gap (4) and a deflecting element (13) for deflecting the foil web (8) is provided, which is arranged such that the foil web (8) has a web section extending freely from the pressure cylinder (6) to the deflecting element (13), characterized in that the blowing device (15) is arranged on the same side of the foil web (8) as the counter-pressure cylinder (7).

Description

[0001] The present invention relates to a foil transfer device for transferring foil onto a substrate.

[0002] Lamination uses a multi-layered film web, from which a film layer is transferred to the substrate in a transfer gap. The transfer gap is formed by a counter-pressure cylinder and a pressure cylinder, which the film web wraps around. Within the transfer gap, the pressure cylinder presses the film web against the substrate, which is transported on the counter-pressure cylinder.

[0003] German patent DE102006004094A1 describes a device in which a blowing device is arranged on the inlet side of the transfer gap – the so-called inlet gusset – which blows air between the film web and the counter-pressure cylinder. On the outlet side of the transfer gap – the so-called outlet gusset – a support plate pressurized with blowing air is arranged, which is located between the film web and the pressure cylinder and thus on the opposite side of the film web than the counter-pressure cylinder.

[0004] EP1676702A1 describes a device in which a compressed air bar is arranged on the exit side of the transfer gap, introducing a burst of compressed air between the film web and the pressure cylinder. The compressed air bar is located on the same side of the film web as the pressure cylinder and on the opposite side from the counter-pressure cylinder.

[0005] DE 295 17 315 ​​U1 describes a foil transfer device in which an air squeegee is directed towards the transfer foil emerging from the transfer gap.

[0006] The air squeegee is directed at the transfer film within a web section, with which web section the transfer film wraps around the pressure cylinder, so that the web section is not a freely extending web section.

[0007] With foil transfer machines, a common problem is the so-called "following" of the foil web on the substrate. This occurs when the foil web adheres to the substrate as it leaves the transfer gap, impairing the quality of the transferred foil layer. Previously, the web tension of the foil web was increased as a countermeasure, but this led to other problems, such as transverse waves in the foil web.

[0008] The invention is based on the objective of creating a further foil transfer device.

[0009] This problem is solved by a foil transfer device having the features of claim 1.

[0010] The foil transfer device according to the invention comprises a counter-pressure cylinder for transporting the substrate and a pressure cylinder for pressing the foil web against the substrate on the counter-pressure cylinder in a transfer gap formed jointly by the pressure cylinder and the counter-pressure cylinder. A blowing device blows into a slit after the transfer gap and is arranged on the same side of the foil web as the counter-pressure cylinder. Furthermore, the foil transfer device according to the invention comprises a deflecting element for deflecting the foil web, which is arranged such that the foil web has a section extending freely from the pressure cylinder to the deflecting element.

[0011] The advantage of this process is that the blowing unit assists in separating the film web from the substrate, thus preventing any impairment of the transfer quality. Therefore, increasing the web tension as a measure against trailing is no longer necessary. The consequential problems that would otherwise arise from increased web tension, such as transverse web waves, are avoided.

[0012] Constructively and functionally advantageous further developments of the invention result from the following description of an exemplary embodiment and the associated drawing, which shows: Fig. 1 of a foil transfer device of a printing press and Fig. 2 a blowing device of the foil transfer device Fig. 1.

[0013] Fig. Figure 1 shows a section of a printing press 1 for planographic offset printing on sheets 2, which can also be referred to as the substrate. The section shows a foil transfer device 3 for laminating the sheets 2 in a transfer gap 4. The sheets 2 are printed in one or more printing units of the printing press 1, which are arranged upstream and / or downstream of the foil transfer device 3 in the sheet transport direction 5 and are not shown in the drawing.

[0014] The transfer gap 4 is formed by a pressure cylinder 6 and a counter-pressure cylinder 7. In the transfer gap 4, a film layer from a multi-layer film web 8, or portions of the film layer, are transferred to the sheet 2, which has been previously printed with adhesive or partially coated, during lamination. The film web 8 is a composite film and comprises, in addition to the film layer to be transferred (transfer layer), a carrier film (carrier layer) and, optionally, a release layer between them, which facilitates the separation of the film layer from the carrier layer. The pressure cylinder 6 is enclosed by the film web 8 and presses the film web 8 against the sheet 2, which is transported by the counter-pressure cylinder 7. The counter-pressure cylinder 7 holds the sheet 2 at its leading edge by means of a gripper acting either by clamping or suction.The transfer of the foil layer is carried out solely by pressure and without the application of heat; accordingly, the foil transfer device 3 is a cold foil transfer device.

[0015] The foil transfer device 3 comprises a supply reel 9 with an unused section of the foil web 8 on a take-up reel and a collection reel 10 with a section of the foil web 8 consumed by the detachment of pieces of the transfer layer in the transfer gap 4 on a winding reel.

[0016] The film web 8 is transported in a film transport direction 11 from the supply reel 9 through the transfer gap 4 onto the collating reel 10, passing a first guiding element or first deflecting element 12 before the transfer gap 4 and a second guiding element or second deflecting element 13 after the transfer gap 4. The two deflecting elements 12, 13 are deflecting rollers, with the second deflecting element 13 being pneumatically actuated from within its interior to minimize friction between the second deflecting element 13 and the film web 8. Specifically, the second deflecting element 13 is a deflecting roller with an air-permeable, microporous roller shell through which the compressed air from the interior of the roller passes to the outer surface of the roller, where the escaping compressed air forms an air cushion between the second deflecting element 13 or its outer surface and the film web 8.

[0017] After the foil transfer is complete, sheet 2 and the foil web 8 still adhering to it exit the transfer gap 4 together. In a run-out gusset 14, which follows the transfer gap 4 in the direction of rotation of the cylinders 6, 7 or in the transport direction of the foil web 8 or sheet 2, and which is formed by the diverging circumferential surfaces of the two cylinders 6, 7, sheet 2 and foil web 8 separate from each other, with sheet 2, including its leading edge, resting on the counter-pressure cylinder 7. The separation occurs at a release point that follows the transfer gap 4 in the direction of rotation of the counter-pressure cylinder 7. The circumferential angle of the counter-pressure cylinder 7 between the transfer gap 4 and the release point – the so-called trailing angle – is greater the stronger the adhesion of the foil web 8 to sheet 2. The trailing angle should be kept as small as possible to avoid impairing the foil transfer.

[0018] As a countermeasure against overflow, a blowing device 15 is directed at the outlet 14, which is designed as a blowpipe and is provided with first blowing openings 16 that are in a plane relative to the image plane of the Fig. The blowing openings 16 are arranged in two vertical rows with a constant distance between openings. The blowing openings 16 can be designed as bores with a diameter ranging from 1.5 mm to 3.0 mm or as nozzles with a diameter ranging from 1.5 mm to 5.0 mm, preferably from 2.5 mm to 4.0 mm. The blowing device 15 expels blowing air from the first blowing openings 16 in the direction of the transfer gap 4, as symbolized by arrows in the drawing, specifically into the wedge-shaped space between the film web 8 and the sheet 2 on the counter-pressure cylinder 7. The blowing direction of the blowing device 15 or the first blowing openings 16 is almost parallel to the film web 8 or inclined to it at an acute angle. The blowing device 15 acts as an air scraper or air blade, and the expelled blowing air peels the film web 8 from the sheet 2.

[0019] The cone of air blown from the first blowing opening 16 strikes at least the majority of the sheet 2, where the incoming air is trapped and deflected. The resulting stagnation pressure of the air blown in the discharge gusset 14 and between the sheet 2 and the film web 8 causes the film web 8 to detach from the sheet 2. The trapped or deflected air blown then forces the film web 8 towards the pressure cylinder 3.

[0020] The blowing device 15 or the first blowing openings 16 can be angle-adjustable with respect to their blowing direction, e.g., rotatable or pivotable by the operator within a limited angular range. The angle adjustment can be made depending on other parameters, e.g., the film strength. The ejected volume flow can be, for example, 70 to 150 m³ / h. 3 / h and can be adjusted by the operator at a control unit of the blowing device 15 not shown in the drawing, or can be controlled on the basis of a characteristic curve stored in the control unit depending on the machine speed.

[0021] The blowing unit 15 can be connected to a temperature control unit, and the blown air expelled from the blowing unit 15 or its first blowing openings 16 can be temperature-controlled blown air, e.g., warm air, to accelerate the drying of the adhesive on the sheet 2 and to improve the removal of the film web 8 from the sheet 2. The expelled blown air can be ionized to reduce electrostatic charges during the removal of the transfer layer. For this purpose, an anti-electrostatic device can also be arranged in the exit gusset 14, e.g., in the form of an anti-electrostatic rod parallel to the blowing unit 15.

[0022] The blowing device 15 includes second blowing openings 17, which are arranged in a plane relative to the image plane. Fig.The second blowing openings 17 are arranged in two vertical rows with a constant distance between openings. These second blowing openings 17 are oriented in a different direction than the first blowing openings 16 and can be described as transverse blowing openings. The second blowing openings 17 are oriented towards the film web 8 such that the blowing air expelled from the second blowing openings 17 strikes the film web 8 at a right angle, as symbolized by an arrow in the drawing. The second blowing openings 17 blow onto the film web 8 within a section extending from the transfer gap 4 to the second deflecting element 13. More precisely, the second blowing openings 17 blow onto the film web 8 within a section of the film web 8 that extends freely from the pressure cylinder 6 to the deflecting element 13.The blowing air expelled from the second blowing openings 17 positively influences the tracking behavior of the film web 8, with this influence being more effective the lower the film web tension is set. Furthermore, the second blowing openings 17 protect the blowing device 15 from the film web 8 striking the blowing device 15.

[0023] In the film transport direction 11 after the second deflection element 13, a further blowing device 18 is arranged, which is designed as a series of fans and could alternatively be designed as a blowing box. The second blowing device 18 is directed towards the film web 8, specifically towards the side of the web containing the transfer layer. The second blowing device 18 blows onto the film web 8 and thereby deflects it in order to increase the web tension of the film web 8 back to the required level if the web tension has dropped undesirably. Reference symbol list 1 printing press 2 sheets 3 Foil transfer device 4 Transfer gap 5. Bow transport direction 6 pressure cylinders 7 counter-pressure cylinders 8 foil strips 9 storage wraps 10 collecting coils 11. Film transport direction 12 first deflection element 13 second deflection element 14 outlet gussets 15 Blowing device 16 first blow opening 17 second blowing opening 18 more blowing devices

Claims

A foil transfer device comprising a counter-pressure cylinder (7) for transporting the substrate (2) and a pressure cylinder (6) for pressing the foil web (8) against the substrate (2) on the counter-pressure cylinder (7) in a transfer gap (4) formed by the pressure cylinder (6) and the counter-pressure cylinder (7), wherein a blowing device (15) blows into a discharge gusset (14) of the transfer gap (4) and a deflecting element (13) for deflecting the foil web (8) is provided, which is arranged such that the foil web (8) has a web section extending freely from the pressure cylinder (6) to the deflecting element (13), characterized in that the blowing device (15) is arranged on the same side of the foil web (8) as the counter-pressure cylinder (7). Foil transfer device according to claim 1, characterized in that the blowing device (15) is arranged between the foil web (8) and the counter-pressure cylinder (7). Foil transfer device according to claim 1 or 2, characterized in that the blowing device (15) forms an air squeegee for peeling the foil web (8) from the substrate (2). Foil transfer device according to claim 1 or 2, characterized in that the blowing direction of the blowing device (15) is aligned with the substrate (2) on the counter-pressure cylinder (7). Foil transfer device according to claim 1 or 2, characterized in that the blowing device (15) is designed to be angle-adjustable with respect to its blowing direction. Foil transfer device according to claim 1 or 2, characterized in that the blowing air ejected from the blowing device (15) is tempered. Foil transfer device according to claim 1 or 2, characterized in that the blowing air ejected from the blowing device (15) is ionized. Foil transfer device according to claim 1 or 2, characterized in that the blowing device (15) has first blowing openings (16) and second blowing openings (17) oriented transversely relative to the first blowing openings (16). Foil transfer device according to claim 8, characterized in that the second blow openings (17) blow onto the foil web (8) within the web section extending freely from the pressure cylinder (6) to the deflecting element (13). Foil transfer device according to claim 9, characterized in that a further blowing device (18) is arranged in the foil transport direction (3) of the foil web (8) after the deflecting element (13) and blows onto the foil web (8).

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