PRINTING PROCESS FOR A METAL CONTAINER AND PRINTER FOR PRINTING ON A METAL CONTAINER

Abstract

A printing process for a metal container includes the steps: Heating the metal container, in particular formed as a metal bottle ready for filling, to a pre-treatment temperature lying in an interval between 100° C. and 250° C., cooling the metal container to a temperature below 100° C., locally activating a printing zone, formed on an outer surface of the metal container to increase a surface energy of the printing zone and/or locally heating the printing zone to a printing temperature which is in an interval between 30° C. and 70° C., printing the printing zone with a printing method.

Claims

1. A printing method for a metal container comprising the steps: heating the metal container to a pre-treatment temperature lying in an interval between 100° C. and 250° C.; cooling the metal container to a temperature below 100° C.; locally activating a printing zone which is located on an outer surface of the metal container to increase a surface energy of the printing zone and/or locally heating the printing zone to a printing temperature which is in an interval between 30° C. and 70° C.; and printing on the printing zone with a printing method.

2. The printing method according to claim 1, wherein with the step of heating the metal container to the pre-treatment temperature, a change in a local distribution of a lubricant layer applied to the outer surface of the metal containers is carried out.

3. The printing method according to claim 2, wherein the metal container is provided with a base coat before a plastic deformation process for the metal container and the printing process are carried out.

4. The printing method according to claim 1, wherein the printing of the printing zone is carried out using a non-contact inkjet printing process.

5. The printing method according to claim 1, wherein the printing zone is provided with a coating after the printing process has been carried out.

6. The printing method according to claim 5, wherein the coating is applied to the metal container in the printing zone using a contactless digital printing process.

7. The printing method according to claim 5, wherein the coating is applied to the outer surface of the metal container using a spraying method.

8. The printing method according to claim 1, wherein the heating of the metal container to the pre-treatment temperature is carried out with a holding time of at least 60 seconds.

9. The printing method according to claim 1, wherein the step of cooling the metal container after the step of heating the metal container to the pre-treatment temperature, which is carried out in a pre-treatment chamber, is carried out by transporting the metal container with a conveyor from the pre-treatment chamber to a printing machine.

10. The printing method according to claim 1, wherein the local activation of the printing zone is carried out with an activation process from the group: corona treatment, plasma treatment, gas flame, infrared irradiation.

11. The printing method according to claim 10, wherein the heating of the printing zone is carried out together with the activation.

12. The printing method according to claim 1, wherein the metal container for printing in the printing zone is gripped and fixed at a bottom region.

13. A printer for printing on a metal container having a conveyor for conveying metal containers along a conveying path, having a pre-treatment chamber which is arranged along the conveying path for heating the metal container to a pre-treatment temperature, which pre-treatment temperature lies in an interval between 100° C. and 250° C., and having a printing machine which is arranged downstream of the pre-treatment chamber on the conveying path and comprises an activator for activating a printing zone of the metal container and a printing unit for printing the printing zone.

14. The printer according to claim 13, wherein the activator carries out an activation process from the group: corona treatment, plasma treatment, gas flame, infrared irradiation.

15. The printer according to claim 13, wherein the pre-treatment chamber is a continuous furnace.

16. The printer according to claim 13, wherein the printing machine has a workpiece rotary table which is mounted rotatably on a machine frame and on which a plurality of receiving mandrels are arranged, each of which is designed for pushing on a metal container.

17. The printer according to claim 13, wherein the printing machine has a workpiece rotary table which is mounted rotatably on a machine frame and on which a plurality of gripping means are arranged, each of which is designed to grip a bottom region of the metal container.

18. The printer according to claim 16, wherein the activator and the printing unit are arranged along an arcuate conveying path defined by the receiving mandrels or the gripping means.

19. The printer according to claim 17, wherein the activator and the printing unit are arranged along an arcuate conveying path defined by the receiving mandrels or the gripping means.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] An advantageous embodiment of the invention is shown in the drawing. Here shows:

[0034] FIG. 1 a strictly schematic representation of a processing device, which comprises a conveyor, a pre-treatment chamber and a printer and is designed for printing on metal containers.

DETAILED DESCRIPTION

[0035] A processing device 1 shown in the single FIG. 1 is provided for printing on outer surfaces of metal containers 11, which metal containers 11 are realized purely exemplarily as metal bottles with a circular-cylindrical container section 30 and a bottle neck 31 which is tapered starting from the container section 30. The processing device 1 is used to print a printing zone 32 provided on the container section 30, which is of purely exemplary rectangular design. For example it is assumed that the metal container 11 is at least largely ready for filling with respect to its structure and geometry. In practice, this means that the metal container 11 is not subjected to further plastic deformation in the course of printing as well as after printing. Rather, the forming operations to be performed directly on the metal container 11 have already been performed before it is fed to the processing device 1. If necessary, it may be provided that after the printing of the metal container 11 as well as a transport of the metal container 11 to a filling device and the execution of the filling, for example with a soft drink, a closure such as, for example, a crown cap is applied to the open end region of the bottle neck 31, whereby a still minor plastic deformation of the metal container 11 may occur, which, however, does not lead to a substantial change in shape for the metal container 11.

[0036] Furthermore, for the following description of the processing device 1 and the printing process for metal containers 11 that can be carried out therewith, it is assumed that the metal containers 11 have already been provided with a base coat before plastic deformation processes are carried out. The base coat on the one hand contributes to a stabilization of the metal container 11 and on the other hand ensures, in a combination with the local lubrication on the container surface, favourable sliding friction properties for the deformation tools with which the plastic deformation of the metal container 11 is carried out. It is further understood that the metal container 11, in particular in the area of the bottle neck 31, is provided with a lubricant application not shown in detail, which also serves to reduce the sliding friction between the bottle neck 31 of the metal container 11 to be formed and the deformation tools not shown.

[0037] The processing device 1 comprises a conveyor 2, by means of which a transport of the metal containers 11 can be carried out starting from a loading position 35 to an unloading position 36, wherein the conveyor 2 comprises, purely by way of example, different conveyor types such as a first conveyor belt 5, a loading starwheel 6, an unloading starwheel 9 and a second conveyor belt 10.

[0038] Purely exemplarily, the first conveyor belt 5 comprises an endlessly circulating chain belt 40, the upper run 41 of which is guided in sections through a pre-treatment chamber 3 designed purely exemplarily as a continuous furnace, while a lower run 42 of the chain belt 40 is guided below the pre-treatment chamber 3. Exemplarily, it is provided that the metal containers 11 are placed on the upper run 41 of the first conveyor belt 5 at the loading position 35 in a manner not shown in more detail, spaced apart manually by an operator or automatically by an industrial robot or another feeding device. In this regard, it is provided that the metal containers 11 are placed on the upper run 41 of the first conveyor belt 5 with a contact surface which is flat or circular in shape and which is determined by the geometry of a bottom region 33 of the respective metal container 11 that is not shown in greater detail.

[0039] By way of example, it is provided that the metal containers 11 are each placed on the first conveyor belt 5 with spacing in a single row and are conveyed by the conveying movement of the first conveyor belt 5 along a first conveying path section 45, which is formed in a straight line, to a first transfer position 37. In this case, a first distance 60 between the end of the pre-treatment chamber 3 and the first transfer position 37 is adapted to a pre-treatment temperature in the pre-treatment chamber 3 and to a geometry of the metal containers 11 and to a conveying speed of the first conveyor belt 5 in such a way that the metal containers 11 are cooled down at the first transfer position 37 to such an extent that, during the subsequently provided feed of the metal containers 11 to the printer 4, only a small amount of heat is applied to the printer 4, which does not impair the functioning of the printer 4.

[0040] Purely by way of example, it is provided that at the first transfer position 37 a removal process for the metal containers 11 is carried out with the aid of the loading starwheel 6, which carries out a counterclockwise rotational movement as shown in FIG. 1 and grips the metal containers 11 at the bottle neck 31. Accordingly, the bottom area 33 of the metal container 11 is free and can be fixed to the workpiece rotary table 7 by the respective gripping means 8 in the course of a counterclockwise rotational movement of the workpiece rotary table 7 arranged adjacent to the loading starwheel 6, in particular using frictional forces and/or a vacuum. Subsequently, the metal containers 11 fixed to the workpiece rotary table 7 by means of the gripping means 8 are guided past a series of work stations 15 to 21 described in more detail below in the course of the clockwise rotary step movement of the workpiece rotary table 7 provided as shown in FIG. 1. Here, work stations 15 to 21 are adapted to the rotary step movement of the workpiece rotary table 7 and the arrangement of the gripping means 8 on the workpiece rotary table 7 in such a way that the metal containers 11 j are arranged exactly opposite the work stations 15 to 21 during the movement pauses of the workpiece rotary table 7.

[0041] By way of example, it is provided that the first work station 15 is designed as an optical inspection device, with the aid of which it can be checked whether the metal container 11 is correctly aligned in the gripping means 8. Furthermore, the optical inspection device of the first work station 15 can also be used to determine a rotational positioning of the metal container 11 about its longitudinal axis, which is not shown, in order to be able to carry out the activation and printing process for the metal containers 11 in the correct position relative to the printing zone 32. Here, it is assumed that each of the gripping means 8 is rotatably mounted on the workpiece rotary table 7 about a rotational axis 12, which is aligned in the radial direction and shown and is coaxial with a rotational symmetry axis 34 of the respective metal container 11, which is also described as a central axis. Accordingly, for carrying out the optical inspection by means of the first work station 15, it can be provided to rotate the metal container 11 about its rotational symmetry axis in order to thereby be able to determine the rotational orientation of the metal container 11.

[0042] In the course of the execution of a rotary step movement by the workpiece rotary table 7, the respective metal container 11 is moved from the first work station 15 to the second work station 16 so that it is arranged opposite the second work station 16 in the subsequent movement of the workpiece rotary table 7. The second work station 16 is also referred to as an activation station and includes an activator, not shown in more detail, for carrying out an activation process from the group: corona discharge, plasma discharge, gas flame, infrared irradiation.

[0043] Preferably, it is provided that the printing zone 32 is aligned as exactly as possible opposite the activator in order to achieve the maximum possible activation result for the printing zone 32 with the lowest possible energy input into the metal container 11. Depending on the selection of the activation method and on the design of the respective activator, it may be provided to keep the metal container 11 in a constant rotational position during the execution of the activation or to rotate it at least by a certain angular amount.

[0044] In the course of the next three rotational step movements, the metal container 11 is arranged opposite the third work station 17, the fourth work station 18 and the fifth work station 19, each of which has one or more digital printing heads, not shown, and which in their commonality form a digital printing unit 25. At each of these work stations 17 to 19, an ink application takes place in the printing zone 32 of the metal container 11. Exemplarily, it is provided that at each of the work stations 17 to 19 exactly one color, for example cyan, yellow, magenta, is delivered to the printing zone 32 in order to realize a multicolor printed image for the metal container 11. Depending on the design of the digital printing unit 25, it may also have fewer or more work stations with print heads.

[0045] After the printing of the printing zone 32 at the work stations 17 to 19, it is provided, purely by way of example, that the printing zone 32 is provided with a coating which ensures, on the one hand, mechanical protection for the printed image produced and, on the other hand, protection against aggressive media, for example liquids, for the printed image. For example, the sixth work station 20 is designed for contactless application of the coating in an inkjet printing process and therefore also comprises one or more print heads.

[0046] In the course of a further rotary step movement for the workpiece rotary table 7, the metal container 11 passes to the seventh work station 21, which is provided purely by way of example for a subsequent and additional curing of the printing ink applied in the preceding printing steps, wherein the work stations 17 to 19 of the digital printing unit 25 can, if necessary, also be equipped with radiation sources for curing the printing ink applied in each case at the work station 17 to 19.

[0047] With a further rotary step movement of the workpiece rotary table 7, the respective metal container 11 reaches an unloading position 36, in which an unloading starwheel 9 can grip the respective metal container 11 at the bottle neck 31 in order to remove it from the gripping means 8 and place it on the second conveyor belt 10.

[0048] Due to the use of the loading starwheel 6, the workpiece rotary table 7 as well as the unloading starwheel 9, a circular section-shaped second conveyor path section 46, a circular section-shaped third conveyor path section 47 as well as a circular section-shaped fourth conveyor path section 48 result, which is followed by a straight-line fifth conveyor path section 49 determined by the second conveyor belt 10. It is understood that instead of the above-described components of the conveyor 2, other components can also be used in order to be able to specify a different conveyor path 44 for the metal containers 11.

[0049] The implementation of the printing process for the metal container 11 can be described as follows in connection with the processing device 1: in a first step, a metal container 11, which is preferably designed ready for filling, is placed from a cardboard box or from a pallet, manually or by means of an automatic handling device, in particular an industrial robot, at the loading position 35 on the upper run 41 of the first conveyor belt 5, so that it is aligned in a straight line with further metal containers 11 already placed on the upper run 41.

[0050] As a result of the conveying motion of the first conveyor belt 5 along the first conveying path section 45, the metal container 11 is transported through the pre-treatment chamber 3, where it is heated to a predetermined pre-treatment temperature, which is in a range between 100° C. and 250° C. Here, a temperature profile in the pre-treatment chamber 3, a conveying speed of the first conveyor belt 5, and a length of the pre-treatment chamber 3 are adjusted to the properties of the metal container 11 such that it is exposed to the pre-treatment temperature for a predetermined period of time, which is also referred to as the holding time, thereby achieving the desired homogenization of the lubricant layer.

[0051] After leaving the pre-treatment chamber 3, a at least predominantly passive cooling of the metal container 11 takes place, whereby the metal container 11 at the first transfer position 37 has a temperature with which an excessive heat input to the subsequent printing machine 4 is avoided. After the metal container 11 has been removed from the upper run 41 of the first conveyor belt 5 and fed to the gripping means 8 of the workpiece rotary table 7, the metal container 11 passes the work stations 15 to 21 in the course of the rotary step movements of the workpiece rotary table 7. First, the alignment of the metal container 11 with respect to the gripper 8 is checked, then the printing zone 32 of the metal container 11 is activated, and then the printing and subsequent coating of the printing zone 32 can be carried out in digital printing processes. Finally, the metal container 11 passes through the seventh and last work station 21, where a final curing of the pre-applied ink layers is performed. In a subsequent step, the metal container 11 is transferred at the second transfer position 38 to the unloading starwheel 9, which then deposits the metal container 11 on the second conveyor belt 10. The second conveyor belt 10 moves the metal container 11 to the unloading position 36, which is not shown in more detail, at which, for example, a manual or automated removal of the now completed metal container from the second conveyor belt 10 and an insertion of the metal container 11 into a transport box, which is not shown, or onto a pallet, which is not shown, can be carried out.