METHOD AND DEVICE FOR PRODUCING A PRINTED CAN LID

Abstract

A method for manufacturing a printed can lid (1) of a can with a digital printing method; comprising at least the following steps: a) making available a shell (2) with an outer face (3) and an inner face (4); b) making available a control unit (9) and a printed image (8), wherein the printed image (8) can be processed in the control unit (9); c) making available at least a first digital printing unit (10) with at least one printing head (11); wherein the printed image (8) which is made available by the control unit (9) can be printed onto the outer face (3) with the printing head (11); and d) printing the printed image (8) which is made available by the control unit (9) onto the outer face (3) with the printing head (11).

Claims

1. Method for manufacturing a printed can lid of a can with a digital printing method; comprising at least the following steps: (a) making available a shell with an outer face and an inner face; (b) making available a control unit and a printed image, wherein the printed image can be processed in the control unit; (c) making available at least a first digital printing unit with at least one printing head; wherein the printed image which is made available by the control unit can be printed onto the outer face with the printing head; (d) printing the printed image which is made available by the control unit onto the outer face with the printing head.

2. Method according to claim 1, wherein in step a) the shell has, at least on the outer face, at least one structure which predefines a first orientation of the shell, and therefore a first position of a printed image which is to be applied to the outer face; wherein the method comprises, before step d), at least the following further steps: (a1) detecting the first orientation of the shell by the control unit; (b1) determining a first position of the printed image which is to be applied, as a function of the detected first orientation; and (c1) making available a printed image which is generated computationally as a function of the first position in the control unit, for the at least one first digital printing unit; wherein in step d) the printed image which is made available by the control unit is printed onto the outer face in the first position with the printing head.

3. Method according to claim 2, wherein in step c1) the printed image is rotated computationally by the control unit.

4. Method according to claim 2, wherein in the control unit there are a multiplicity of printed images which are each rotated by a predefined angular value; wherein in step c1) a printed image which is oriented in a way matching the first orientation by the control unit is selected and is made available for the first digital printing unit.

5. Method according to claim 4, wherein the predefined angular values of the printed images, which are present in the control unit, differ by at maximum 5 angular degrees in each case.

6. Method according to claim 1, wherein the structure is an opening element; wherein a removal opening in the can lid can be opened by a user by the opening element.

7. Method according to claim 1, wherein the at least one printing head is arranged with respect to the outer face in such a way that at least one partial surface, to be printed, of the outer face is moved at least two millimetres away from the printing head during the printing.

8. Method according to claim 1, wherein the shell has, directly before the printing according to step d), a temperature of at least 40 degrees Celsius.

9. Method according to claim 1, wherein the first digital printing unit comprises at least four printing heads, wherein each printing head applies a different printing ink.

10. Method according to claim 1, wherein water-based colors are applied by the first digital printing unit.

11. Method according to claim 2, wherein between the steps a1) and d) the shell is fed to the first digital printing unit in a feed direction, wherein only before step a1) the shell is moved in a lateral direction, perpendicularly with respect to the feed direction, and is aligned therewith.

12. Method according to claim 1, wherein after step d) the shell is fed to a pad-printing unit, wherein the printed image is coated over by the pad-printing unit.

13. Method according to claim 1, wherein before step d) the shell is at least partially printed with a white printing ink by a printing unit or by a second digital printing unit.

14. Device for manufacturing a printed can lid of a can with a digital printing method; wherein a shell has an outer face and an inner face; wherein the device comprises at least: (1) a control unit for processing the printed image; (2) a feed unit for feeding the shell in a feed direction; (3) a first digital printing unit with at least one printing head with which the printed image which is made available by the control unit can be printed onto the outer face.

15. Device according to claim 14, wherein the shell has, at least on the outer face, at least one structure which predefines a first orientation of the shell and therefore a first position of a printed image which is to be applied to the outer face; wherein the device additionally comprises a sensor unit for detecting the first orientation of the shell on the feed unit by the control unit; wherein by the control unit it is possible to determine a first position of the printed image as a function of the first orientation of the shell which is detected by the sensor unit, and therefore to generate a computationally generated printed image for the first digital printing unit and to apply said printed image to the outer face in the first position with the printing head.

16. Device according to claim 15, wherein the device comprises an orientation unit, by which the shell can be moved by the sensor unit in a lateral direction, perpendicularly with respect to the feed unit and aligned therewith.

17. Device according to claim 14, wherein the device comprises a heating apparatus for heating the shell to a predefinable temperature, with the result that immediately before the printing by the printing head the shell is at a temperature of at least 40 degrees Celsius.

Description

[0074] The invention as well as the technical field are explained in more detail below with reference to the figures. It is to be noted that the invention is not intended to be restricted by the exemplary embodiments shown. In particular, unless not explicitly presented otherwise, it is also possible to extract partial aspects of the contents which are explained in the figures and combine them with other components and realizations from the present description and/or figures. Identical reference symbols denote identical objects, with the result that, where appropriate, explanations from other figures can be used in a supplementary fashion. In the drawings, in each case in a schematic form:

[0075] FIG. 1 shows a shell in a plan view;

[0076] FIG. 2 shows the shell according to FIG. 1 in a side view;

[0077] FIG. 3 shows a device in a plan view; and

[0078] FIG. 4 shows a further device in a side view.

[0079] FIG. 1 shows a can lid 1 or shell 2 in a plan view. FIG. 2 shows the shell 2 according to FIG. 1 in a side view. FIGS. 1 and 2 are described together below.

[0080] The can lid 1 has an outer face 3 with a circular lid base area and an inner face 4 which is arranged on the opposite side of the can lid 1. The can lid 1 has a core wall 25 and a core bead 26 which is arranged between the lid base area and the core wall 25. At its outer circumference, the can lid 1 has a flanged edge 27 for connection to a can body to form a beverage can.

[0081] On the outer face 3 a bead 28 is arranged which is embodied in a non-rotationally symmetrical fashion and serves to reinforce the can lid 1. An opening element 30 which is embodied as a clip is attached to a rivet 29 of the can lid 1. A scoring line 31, by means of which a drink opening or removal opening 13 of the can lid 1 can be opened by the opening element 30 being handled by a user is formed on the outer face 3. The scoring line 31 of the exemplary can lid 1 which is illustrated in FIG. 1 is formed by two parallel lines, the first ends of which are visible, and the second ends of which are, however, arranged underneath the opening element 30.

[0082] The opening element 30 forms here a structure 5 which predefines a first orientation 6 of the shell 2 and therefore a first position 7 of a printed image 8 which is to be applied to the outer face 3.

[0083] The can lid 1 has on its outer face an area for a printed image 8, which corresponds to the example shown in FIG. 1 essentially to the entire outer face 3 and is also embodied in an (approximately) circular shape. In the example shown in FIG. 1, an upper side of the opening element 30 is completely printed, as is also the rivet 29. In the example illustrated in FIG. 1, the scoring line 31 is also printed to form the part which is not covered by the opening element 30. The part of the scoring line 31 which is arranged under the opening element 30 is not printed.

[0084] With the digital printing method proposed here it is possible to print the outer face 3 of the can lid 1 as far as the flanged edge 27.

[0085] FIG. 3 shows a device 20 for carrying out the proposed method in a plan view. The shell 2 has an outer face 3 and an inner face 4 and at least on the outer face 3 at least one structure 5 which predefines a first orientation 6 of the shell 2 and therefore a first position 7 of a printed image 8 which is to be applied to the outer face 3. The device 20 comprises a control unit 9 for processing the printed image 8, a feed unit 21 for feeding the shell 2 in the feed direction 15, a sensor unit 22 for detecting the first orientation 6 of the shell 2 on the feed unit 21 by means of the control unit 9, and a first digital printing unit 10 with a multiplicity of printing heads 11, with which the printed image 8 which is made available by the control unit 9 can be printed onto the outer face 3 or the can lid 1. By means of the control unit 9 it is possible to generate a computationally generated, rotated printed image 8 for the first digital printing unit 10 as a function of the first orientation 6 of the shell 2 which is detected by means of the sensor unit 22, and to apply said image to the outer face 3 or the shell 2 in the first position 7 with the printing heads.

[0086] Furthermore, the device 20 comprises a heating apparatus 23 for heating the shell 2 with the result that immediately before the printing by means of the printing heads 11 the shell 2 is still at a temperature of at least 60 degrees Celsius.

[0087] Furthermore, the device 20 comprises an orientation unit 24 by means of which the shell 2 can be moved in front of the sensor unit 22 in a lateral direction 16, perpendicularly with respect to the feed unit 15, and can be aligned therewith, wherein after the movement by means of the orientation unit 24 and until the printing with the printing heads 11 the shell 2 remains in this position and in the first orientation 6.

[0088] The device 20 also comprises a first sensor 32 by means of which the applied printed image 8 is checked. If an error is detected here, the affected can lid 1 can be removed from the feed unit 21 by means of the ejection device 34.

[0089] Furthermore, the device 20 comprises a second sensor 33 which checks e.g. a height of the can lids 1 which are positioned on the feed unit 21. If a fault is detected here, the affected can lid 1 is also removed from the feed unit by means of an ejection device 34.

[0090] The method for manufacturing a printed can lid 1 of a can with a digital printing method comprises the following steps which are carried out by means of the device 20. According to step a) a shell 2 with a structure 5 is made available, wherein the structure 5 predefines a first orientation 6 of the shell 2 and therefore a first position 7 of a printed image 8 which is to be applied to the outer face 3. According to step b) a control unit 9 and a printed image 8 are made available, wherein the printed image 8 can be processed in the control unit 9. According to c) a first digital printing unit 10 is made available with a multiplicity of printing heads 11, wherein a printed image 8 which is made available by the control unit 9 can be printed onto the outer face 3 or the shell 2 with the printing heads 11. In step a1), the first orientation 6 of the shell 2 is sensed by means of the control unit 9. In step b1), a first position 7 of the printed image 8 which is to be applied is determined by means of the control unit 9 as a function of the detected first orientation 6. In step c1), a printed image 8 which is generated, if appropriate rotated computationally, as a function of the first determined position 7 of the printed image 8 is made available for the first digital printing unit 10. In step d), the rotated printed image 8 which is made available by the control unit 9 is printed onto the outer face 3 in the first position 7 with the printing heads 11.

[0091] In step a1), the first orientation 6 of the shell 2 is sensed or detected by means of the control unit 9. The sensing or detection of the first orientation 6 is carried out using a sensor unit 22 whose measurement signal is sensed and processed by means of the control unit 9. An optical sensor, by means of which e.g. the position of an opening element 30 is sensed, is preferably used here.

[0092] In step c1), a printed image 8 which is generated (and if appropriate rotated) computationally in the control unit 9 as a function of the first orientation 6 of the shell 2 is made available for the at least one first digital printing unit 10.

[0093] In contrast to known methods, the shell 2 is not rotated or moved here in such a way that the printed image 8 can always be applied in the same way to the shell 2. It is proposed here that the printed image 8 be oriented (in a virtual fashion) in the control unit 9 in such a way that it can then be applied with the suitable orientation by means of the printing heads 11 to the (always differently) oriented shell 2.

[0094] Therefore, a movement of the shell 2, e.g. a rotation of the shell 2 or lateral shifting is not necessary before the printing in the first digital printing unit 10. An adaptation of the position of the printing head 11 or of the first digital printing unit 10 is also not necessary, since a rotated data record or a laterally offset data record which is made available by the control unit 9 of the printing image 8 is applied to the shell 2.

[0095] The shells 2 are fed to the first digital printing unit 10 at a speed of at least 30 metres per minute. In the time between the sensing of the first orientation 6 in step a1) (at the sensor unit 22) and the making available of the rotated (and/or laterally shifted) printed image 8 according to step c1) the shell 2 may have travelled at maximum the distance e.g. between the sensor unit 22 which is used in step a1) and the first digital printing unit 10.

[0096] Alternatively, there are a multiplicity of printed images 8 which are each rotated by a pre-defined angular value 12 (and/or which are offset laterally by a value) in the control unit 9, wherein in step c1) a printed image 8 which is oriented in a way matching the first orientation 6 is selected by means of the control unit 9 and made available for the first digital printing unit 10.

[0097] During the printing according to step d), the printing heads 11 are arranged with respect to the outer face 3 or to the shell 2 in such a way that at least one partial surface 14, to be printed, of the outer face 3 is at least two millimetres away from each printing head 11 during the printing. In particular, this distance (measured essentially in a direction in which the printing ink moves from the printing head 11 to the partial surface 14) of the printing head 11 from the outer face 3 is necessary for no contact to occur between the printing head 11 and the shell 2 in the other areas of the shell 2, e.g. at places where the structure 5 is arranged.

[0098] The first digital printing unit comprises here six printing heads 11, wherein each printing head 11 applies a different printing ink.

[0099] After step d), the applied printing ink is visibly dried by means of heat, e.g. as a result of drying with hot air or of infrared drying in a drying unit 37.

[0100] Between the steps a1) and d) the shell 2 is fed to the first digital printing unit 10 in a feed direction 15, wherein only before step a1) the shell 2 is moved in a lateral direction 16, perpendicularly with respect to the feed direction 15, and is aligned therewith. This movement or orientation in the lateral direction 16 positions the shell 2 under the at least one printing head 11 in such a way that the printed image 8 can be applied in each case in a centred fashion on the shell 2.

[0101] The movement or orientation is carried out by means of guide devices or guide rails of an orientation unit 24 which shift the shell 2 on the feed unit 21.

[0102] The feed unit 21 comprises a conveyor belt on which the shells 2 are secured e.g. by means of the application of a partial vacuum. A movement of the shell 2 with respect to the feed unit 21 can then be carried out only by means of external force, e.g. by means of guide devices or guide rails of the orientation unit 24 by means of the ejection devices 34.

[0103] The shell 2 is at least partially printed here before step d) by means of a printing unit 18 or by means of a second digital printing unit 19, with a white printing ink as a primer coat by means of three printing heads 11 here.

[0104] The first orientation 6 of the shell 2 is also sensed for this printing, with the result that a correspondingly oriented application of the white printing ink can be carried out.

[0105] In addition, at least before step d), and here also before the printing by means of the second digital printing unit 19 or by means of the printing unit 18, at least the outer face 3 or the shell 2 is cleaned and/or surface activated (e.g. by means of a plasma treatment) by means of a cleaning unit 36.

[0106] FIG. 4 shows a further device in a side view. This further device comprises a pad-printing unit 17 to which the shell 2 is fed by means of the feed unit 21 after step d), wherein the printed image 8 is coated over by means of the pad-printing unit 17. In the pad-printing method, a printed image 8 is applied, by means of a deformable compression die 38, to a surface which is to be printed on (the shell 2 or the can lid 1). The surface to be printed on does not have to be flat here but rather can have depressions and elevated portions. This is made possible by the deformable compression die 38 which is composed of a soft, elastic material and is designed to deform when in contact with a surface to be printed, and in this case transfer previously absorbed printing media, e.g. printing inks or surface coating agents, to the surface to be printed.

[0107] Here, a (single-coloured or colourless) surface coating agent which covers at least the printing inks applied in step d) (or at least the printing inks without regulatory approval for use in the food industry).

LIST OF REFERENCE NUMBERS

[0108] 1 Can lid [0109] 2 Shell [0110] 3 Outer face [0111] 4 Inner face [0112] 5 Structure [0113] 6 First orientation [0114] 7 First position [0115] 8 Printed image [0116] 9 Control unit [0117] 10 First digital printing unit [0118] 11 Printing head [0119] 12 Angular value [0120] 13 Removal opening [0121] 14 Partial surface [0122] 15 Feed direction [0123] 16 Lateral direction [0124] 17 Pad-printing unit [0125] 18 Printing unit [0126] 19 Second digital printing unit [0127] 20 Device [0128] 21 Feed unit [0129] 22 Sensor unit [0130] 23 Heating apparatus [0131] 24 Orientation unit [0132] 25 Core wall [0133] 26 Core bead [0134] 27 Flanging edge [0135] 28 Bead [0136] 29 Rivet [0137] 30 Opening element [0138] 31 Scoring line [0139] 32 First sensor [0140] 33 Second sensor [0141] 34 Ejection device [0142] 35 Motor [0143] 36 Cleaning unit [0144] 37 Drying unit [0145] 38 Compression die