Method and apparatus for cold-stamping onto three-dimensional objects

Abstract

The invention relates to a method and an apparatus for cold-stamping onto a three-dimensional object. In a first step, an adhesive is applied to the object at a first workstation. In a second step, a transfer film is pressed onto the object by a pressing device at a second workstation. At the same time, the adhesive is cured at the second workstation. As a result, the decorative material of the transfer film adheres to the object at the positions on the object which are provided with adhesive. If, following this, the transfer film is removed from the three-dimensional object after being pressed on, the decorative material remains on the object at the desired positions. At the positions at which in the first step no adhesive has been applied to the object, the decorative material does not adhere to the object but rather remains on the carrier film of the transfer film.

Claims

1. A method for cold-stamping a three-dimensional object, wherein the three-dimensional object is held either rotatably around an axis of rotation or is firmly fixed by a holding device, the method comprising: applying an adhesive to the three-dimensional object at a first work station, wherein the adhesive is a UV-adhesive and wherein a curing of the adhesive is performed by irradiation with UV-radiation generated by a UV-radiation source; and pressing a transfer film comprising a decorative layer and a carrier film onto the three-dimensional object by a single pressing device at a second work station, wherein the adhesive is initially simultaneously at least partially cured by UV radiation at the same time as the transfer film is pressed onto the three-dimensional object by the single pressing device at the second workstation at a position where the transfer film is in contact with the single pressing device, wherein the single pressing device comprises a cylinder which can be rotated around a cylinder axis, wherein the UV-radiation source can be arranged within the cylinder of the single pressing device; wherein the single pressing device is transparent for UV-radiation at least in partial regions and is arranged at least partially between the UV-radiation source and the holding device; wherein the single pressing device comprises a flexible pressing layer, and wherein after at least partial curing of the adhesive, the carrier film is removed from the three-dimensional object and the three-dimensional object is subjected once again to UV-radiation.

2. The method according to claim 1, wherein at least one of the single pressing device or the flexible pressing layer is made of silicone and comprises a thickness in the range of 1 mm to 20 mm in a region to be penetrated by UV-radiation.

3. The method according to claim 2, wherein the silicone comprises a hardness in the range of 30? Shore A to 70? Shore A.

4. The method according to claim 1, wherein the decorative layer comprises at least one of at least one metallic layer, at least one dielectric layer or at least one transparent, translucent, or opaque color layer.

5. The method according to claim 4, wherein the decorative layer comprises the metallic, dielectric, and/or color layer in each case over an entire surface or partially.

6. The method according to claim 1, wherein at one or a plurality of further workstations downstream of the second workstation for pressing the transfer film and curing the adhesive an additional coating is provided on the three-dimensional object in the region of the decorative material, and/or in regions adjacent thereto, or on the entire surface thereof.

7. The method according to claim 6, wherein the coating is performed by one or plurality or additionally applied transparent, translucent, or opaque lacquer layers.

8. A method according to claim 1, wherein the pressing of the transfer film onto the three-dimensional object comprises: rotating the three-dimensional object around the axis of rotation; guiding the transfer film tangentially with respect to an outer periphery of the three-dimensional object; and pressing the transfer film onto the three-dimensional object along a contact line between the three-dimensional object and transfer film by the single pressing device.

9. A method according to claim 1, wherein the single pressing device is moved such that a surface speed of the single pressing device corresponds to a surface speed of the three-dimensional object, and wherein the transfer film is moved such that the surface speed of the transfer film corresponds to the surface speed of the three-dimensional object.

10. The method according to claim 1, wherein the pressing of the transfer film onto the three-dimensional object is performed by guiding the transfer film between the cylinder and the three-dimensional object while the cylinder rotates around the cylinder axis and the three-dimensional object simultaneously rotates around the axis of rotation.

11. The method according to claim 1, wherein the pressing of the transfer film onto the three-dimensional object is performed by guiding the cylinder linearly over the three-dimensional object as a stationary object while the cylinder simultaneously rotates around the cylinder axis.

12. The method according to claim 1, wherein the transfer film or the decorative layer comprises a transmittance in the range of 5% to 70%, for UV-radiation in the wavelength range of 250 nm to 420 nm.

13. The method according to claim 1, wherein at least one of the single pressing device or the flexible pressing layer is transparent or translucent in the range of 30% to 100% in the wavelength range of 250 nm to 420 nm.

14. The method according to claim 1, wherein the flexible pressing layer is formed to be flat.

15. The method according to claim 1, wherein at least one of the single pressing device or the flexible pressing layer at least partially comprises a structured or textured surface.

16. The method according to claim 1, wherein the decorative layer comprises a lacquer having impressed relief structures, which are macroscopic, refractively effective, and/or microscopic, in particular effective in terms of diffractive optics.

17. The method according to claim 1, wherein the decorative layer is applied in a desired position on the three-dimensional object with a register accuracy of ?1 mm.

18. The method according to claim 1, wherein at one or a plurality of further workstations upstream of the first workstation for applying the adhesive, a coating is provided on the three-dimensional object partially or on the entire surface thereof, by screen printing, flexographic printing and/or digital printing.

19. The method according to claim 1, wherein the first workstation for applying the adhesive, the second workstation for pressing the transfer film and curing the adhesive are arranged in-line.

20. A method for cold-stamping a three-dimensional object, wherein the object is held either rotatably around an axis of rotation or is firmly fixed by a holding device, the method comprising: applying an adhesive to the object at a first work station, wherein the adhesive is a UV-adhesive and wherein a curing of the adhesive is performed by irradiation with UV-radiation generated by a UV-radiation source; and pressing a transfer film comprising a decorative layer and a carrier film onto the object by a single pressing device at a second work station, wherein the adhesive is simultaneously cured at the same time as the transfer film is pressed onto the object by the single pressing device at the second workstation at a position where the transfer film is in contact with the single pressing device; wherein the single pressing device is transparent for UV-radiation at least in partial regions and is arranged at least partially between the UV-radiation source and the holding device; wherein the single pressing device comprises a planar plate, wherein the planar plate is arranged between the UV irradiation device and the three-dimensional object; and wherein the single pressing device comprises a flexible pressing layer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be explained in detail hereinafter with reference to the drawings, in which:

(2) FIG. 1a shows a schematic view of a first workstation of an embodiment of an apparatus in accordance with the invention;

(3) FIG. 1b shows a schematic view of a first workstation of another embodiment of an apparatus in accordance with the invention (i) in a side view and (ii) in a perspective view;

(4) FIG. 2 shows a schematic view of a second workstation of a preferred embodiment of an apparatus in accordance with the invention;

(5) FIG. 3 shows a schematic view of the first workstation of FIG. 1 and of the second workstation of FIG. 2 in a perspective view;

(6) FIG. 4 shows a schematic view of a first exemplary holding device;

(7) FIG. 5 shows a schematic view of a second exemplary holding device; and

(8) FIG. 6 shows a schematic view of a second workstation of another embodiment of an apparatus in accordance with the invention.

(9) FIG. 1a shows a first workstation 1 which is designed as a flexographic printing station. Mounted on a printing block cylinder 11 is a printing plate 12, which determines the motif in which the adhesive is to be applied to the object 4. Using an anilox roller 13 the adhesive is transferred from a reservoir to the printing plate 12. The adhesive is applied to the anilox roller 13, e.g., by a fountain roller printing unit or a chamber scraper system.

(10) The object 4 is held from the inside by a holding device 3 which is designed as a holding mandrel 31. By rotating the mandrel 31 about the axis of rotation 32, the object 4 can also be rotated about this axis. The printing block cylinder 11 together with the printing plate 12 is also rotated at the same time as the holding mandrel 31, so that the adhesive applied to the printing plate 12 is transferred to the surface of the object 4.

(11) FIG. 1b shows a first workstation 1 which is designed as a screen printing station. A screen 15 having a fine-meshed fabric determines the motif in which the adhesive is to be applied to the object 4 by virtue of the fact that the mesh openings of the fabric are made impermeable for the adhesive, e.g., by a template, at the positions where no adhesive is to be applied. A scraper 14 is used to press the adhesive through the fabric of the screen 15 onto the object 4.

(12) The object 4 is held from the inside by a holding device 3 which is designed as a holding mandrel 31. By rotating the holding mandrel 31 about the axis of rotation 32, the object 4 can also be rotated about this axis. At the same time as holding mandrel 31 rotates, a relative linear movement is effected between the holding mandrel 31 and the screen 15 so that as a result the object 4 is rolled along the screen 15. The scraper 14 remains stationary relative to the holding mandrel 31. Therefore, the adhesive is applied to the object 4 in accordance with the motif defined by the template.

(13) FIGS. 2 and 3 show an embodiment of a second workstation 2. The holding device 3 with the object 4 held thereon was moved on from the first workstation 1 to the second workstation 2 after the adhesive was applied to the object 4. The second workstation comprises a film unwinding arrangement 22, on which the supply of transfer film 21 is received. The transfer film 21 is guided to the object 4 by a plurality of guide rollers 23. The guide rollers 23 are used to adjust inter alia the web tension of the transfer film 21, in order to guide the transfer film 21 without any folds to the object 4. Two further guide rollers 23a ensure that the transfer film is guided tangentially past the object 4. The used transfer film 21 is finally guided by further guide rollers 23 to a film wind-up arrangement 24 and is wound up thereon.

(14) In the contact region 29 between the object 4 and transfer film 21, the transfer film 21 is pressed against the object 4 by a pressing device. The pressing device comprises a cylinder 25 which is coated with a silicone layer 26 to compensate for any unevenness. The cylinder 25 is designed as a hollow cylinder so that a UV-radiation source 27 can be disposed in the interior thereof. In order to ensure that the UV-radiation emitted by the UV-radiation source 27 in the direction of the object 4 can exit the cylinder 25, the cylinder 25 and also the coating 26 are formed from materials which are transparent for the UV-radiation required for curing purposes. The cylinder 25 can be made in particular from soda-lime glass, borosilicate glass, PMMA (polymethacrylate, referred to colloquially as plexiglass) or polycarbonate (PC). The coating 26 is mechanically attached on the cylinder 25 in particular by clamping strips. However, this can also be achieved by adhesion by adhesives which are highly transparent in particular for the UV-radiation used and are stable over a period of time when subjected to UV-radiation.

(15) During operation of the second workstation 2, the holding mandrel 31 is rotated with the object 4, which is located thereon, about the axis of rotation 32, while at the same time the transfer film 21 is guided past the object 4. Furthermore, at the same time the cylinder 25 is rotated about the cylinder axis 28 so that the transfer film 21 is pressed against the object 4. The rotational speeds of the cylinder 25 and of the holding mandrel 31 and the transport speed of the transfer film 21 are adapted to one another such that these three elements are moved without rubbing against one another.

(16) The UV-adhesive is cured by the UV-radiation at the same time as the transfer film 21 is pressed onto the object 4. By virtue of the rotation of the object 4 and the tangential progression of the transfer film 21 with respect to the object 4, the transfer film 21 is then removed from the object 4 immediately after curing. At the positions where adhesive has been applied to the object 4, the decorative material (e.g. the metal layer) of the transfer film 21 adheres to the object 4 once the adhesive has cured. At the positions where there was no adhesive, the decorative material remains on the transfer film 21.

(17) Further steps for treating the object 4 can be carried out at further workstations. For example, the object 4 can have different colors printed thereon, the surface of the object 4 can be treated in order to ensure, e.g., a better reception of color, or finally the object 4 can be provided with a protective layer. These steps can be performed at workstations upstream or also downstream of the workstations responsible for cold-stamping. The workstations can be arranged, e.g., in a longitudinal transfer system or in a revolving transfer system.

(18) By virtue of the fact that the cold-stamping method in accordance with the invention can be performed at workstations of a longitudinal transfer system or a revolving transfer system, without the object having to be transferred to a different holding device, it is possible to integrate the cold-stamping method in a problem-free manner into the process of producing the object.

(19) FIGS. 4 and 5 show exemplified embodiments of holding devices which can be used in an apparatus in accordance with the invention or with a method in accordance with the invention. The holding device illustrated in FIG. 4 comprises a holding mandrel 31, onto which the object is slid. The diameter of the holding mandrel 31 is selected such that the object is held in a frictionally engaged manner on the holding mandrel 31. In order to improve the manner in which the object is held on the holding mandrel 31, air can be extracted by suction through openings 33 at the free end of the holding mandrel 31, whereby the object is drawn onto the holding mandrel 31 by reason of the vacuum in the interior. As a result, the object is seated firmly on the holding mandrel 31 and can be processed at the workstations, even on the entire surface if required.

(20) The holding device illustrated in FIG. 5 holds the object 4 (in this case a bottle, for example) by virtue of the fact that at one end the object 4 is clamped in a holder 35 and at the opposite end is mounted in a rotatable manner in a counter bearing 36. By rotating the holder 35 about an axis, the object 4 is also rotated about its axis of rotation and can be processed at workstations. Such a holding device can then be used, e.g., if one side of the object 4 does not comprise an opening large enough for a holding mandrel.

(21) FIG. 6 shows a further embodiment of a second workstation 2. The guide of the transfer film 21 corresponds substantially to the embodiment illustrated in FIGS. 2 and 3 and will not be described again. The pressing device which presses the transfer film 21 against the object 4 in the contact region 29 between the object 4 and transfer film 21 comprises in the embodiment of FIG. 6 a planar pressing plate 34 which is coated with a silicone layer 26, e.g., for compensating for any unevenness and for reducing the friction between the pressing device and transfer film 21.

(22) The UV-radiation source 27 is arranged above the pressing plate 34, i.e., on the other side of the pressing plate 34 than the transfer film 21. The pressing plate 34 and the coating 26 are formed from materials which are transparent for the UV-radiation required for curing purposes, which means that the UV-radiation emitted by the UV-radiation source 27 in the direction of the object 4 can pass through the pressing plate 34 and the coating 26. The pressing plate 34 can be made in particular from soda-lime glass, borosilicate glass, PMMA (polymethacrylate, referred to colloquially as plexiglass) or polycarbonate (PC). The coating 26 is mechanically attached to the pressing plate 34 in particular by clamping strips or screws. However, this can also be achieved by adhesion by adhesives which are highly transparent in particular for the UV-radiation used and are stable over a period of time when subjected to UV-radiation. During operation of the second workstation 2, the holding mandrel 31 is rotated with the object 4, which is located thereon, about the axis of rotation 32, while at the same time the transfer film 21 is guided past the object 4.

(23) The UV-adhesive is cured by the UV-radiation at the same time as the transfer film 21 is pressed onto the object 4. By virtue of the rotation of the object 4 and the tangential progression of the transfer film 21 with respect to the object 4, the transfer film 21 is then removed from the object 4 immediately after curing. At the positions where adhesive has been applied to the object 4, the decorative material (e.g. the metal layer) of the transfer film 21 adheres to the object 4 once the adhesive has cured. At the positions where there was no adhesive, the decorative material remains on the transfer film 21.

(24) As in the case of the embodiment of FIGS. 2 and 3, further steps for treating the object 4 can be carried out at further workstations.

(25) Of course, the invention is not limited to the holding devices which are illustrated. For the invention, any holding device can be used which renders it possible to hold the three-dimensional object in such a manner that all of the positions on the object which are to be processed are accessible.

(26) The second workstations illustrated in the drawings do not necessarily have to be used together with the first workstation illustrated in the drawings. In particular, it is not necessary for the first workstation to be a screen printing or a flexographic printing station. The first workstation could also be a digital printing station (e.g. ink-jet).

LIST OF REFERENCE NUMERALS

(27) 1 first workstation 2 second workstation 3 holding device 4 object 11 printing block cylinder 12 printing plate 13 anilox roller 14 scraper 15 screen 21 transfer film 22 film unwinding arrangement 23 guide rollers 23a guide rollers 24 film winding-up arrangement 25 pressing cylinder 26 pressing layer 27 UV-radiation source 28 cylinder axis 29 contact point 31 holding mandrel 32 axis of rotation 33 openings 34 pressing plate 35 holder 36 counter bearing