Method and direct-printing machine for printing containers of different material types in a direct-printing process

Abstract

A method and a direct-printing machine for printing on containers of different types of materials in a direct-printing process, wherein containers of a first type of material are conveyed by means of a conveyor and printed on, in several layers, with a plurality of printing units by means of direct-printing heads with a first basic ink compatible with the first type of material (102) and, on top of the first basic ink, with at least one colored ink. The first basic ink may be exchanged for a second basic ink, which is compatible with the second type of material, when a change to containers of a second type of material takes place, and the containers of the second type of material may then be printed on, in several layers, with the second basic ink (105) and, on top of the second basic ink, with the at least one colored ink.

Claims

1. A method for printing on containers of different types of materials in a direct-printing process, wherein containers of a first type of material are conveyed by means of a conveyor and printed on, in several layers, with a plurality of printing units by means of direct-printing heads with a first basic ink compatible with the first type of material and, on top of the first basic ink, with at least one colored ink, wherein when changing to containers of a second type of material different from the first type of material, the first basic ink is exchanged for a second basic ink, which is compatible with the second type of material, the containers of the second type of material are then printed on, in several layers, with the second basic ink and, on top of the second basic ink, with the at least one colored ink, and the at least one colored ink adheres to the first basic ink and the second basic ink.

2. The method according to claim 1, wherein the second basic ink is chemically and physically compatible with the first basic ink such that both basic inks can be mixed completely into one another, without any destabilization of the two basic inks being caused.

3. The method according to claim 1, wherein one of the printing units is configured for printing the first basic ink and the second basic ink with at least one direct-printing head, and an ink feed unit supplies the at least one direct-printing head selectively with the first basic ink or the second basic ink for purposes of printing.

4. The method according to claim 3, wherein, during a change, the at least one direct-printing head and/or the ink feed unit with the first basic ink are emptied at least partially, and filled with the second basic ink.

5. The method according to claim 4, wherein the direct-printing head and/or the ink feed unit are filled at least once with the second basic ink during flushing, so that the first basic ink remaining therein after emptying mixes with the second basic ink.

6. The method according to claim 4, wherein, the at least one direct-printing head and/or the ink feed unit with the first basic ink are flushed at least once, and wherein during the flushing, the at least one direct-printing head and/or a common supply section for both basic inks are flushed.

7. The method according to claim 4, wherein the at least one direct-printing head and/or the ink feed unit with the first basic ink are flushed at least once.

8. The method according to claim 3, wherein, during printing, the at least one direct-printing head is selectively supplied from a first ink supply with the first basic ink or from a second ink supply with the second basic ink by means of the ink feed unit, and wherein the ink feed unit switches from the first ink supply to the second ink supply during the change.

9. The method according to claim 3, wherein the ink feed unit mixes a basic component selectively with a first additive or a second additive so as to form therefrom either the first basic ink or the second basic ink, and wherein, during the change, the ink feed unit switches over from mixing the basic component with the first additive to mixing the basic component with the second additive.

10. The method according to claim 9, wherein the ink feed unit obtains the basic component, the first additive and the second additive from respective different supplies.

11. The method according to claim 1, wherein, during a change, switching over from one of the printing units for printing the first basic ink to another printing unit for printing the second basic ink, or an exchange of these printing units, is carried out.

12. The method according to claim 1, wherein the first type of material and the second type of material of the containers are different types of plastic material.

13. The method according to claim 1, wherein the first type of material and the second type of material of the containers are different types of plastic material selected from the group consisting of PET, HD-PE and PP.

14. The method according to claim 1, wherein the first type of material and the second type of material of the containers are different types of material selected from the group consisting of glass, plastic, metal, biodegradable materials and hybrid materials.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Additional features and advantages of the present invention will be explained hereinafter in more detail with reference to the embodiments shown in the figures, in which:

(2) FIG. 1 shows, as a flowchart, an embodiment of a method according to the present invention used for printing on containers of different types of materials in a direct-printing process;

(3) FIG. 2 shows substeps of the method according to FIG. 1 for changing to the containers of the second type of material according to a first variant;

(4) FIG. 3 shows substeps of the method according to FIG. 1 for changing to the containers of the second type of material according to a second variant;

(5) FIG. 4 shows substeps of the method according to FIG. 1 for changing to the containers of the second type of material according to a third variant;

(6) FIG. 5 shows an embodiment of a direct-printing machine according to the present invention in a top view;

(7) FIG. 6 shows a further embodiment of a direct-printing machine according to the present invention in a top view;

(8) FIG. 7A shows an embodiment of the printing unit according to FIG. 6 in a top view; and

(9) FIG. 7B shows a further embodiment of the printing unit according to FIG. 6 in a top view.

DETAILED DESCRIPTION

(10) FIG. 1 shows, as a flowchart, an embodiment of a method 100 according to the present invention used for printing on containers of different types of materials in a direct-printing process.

(11) What can be seen is that containers of the first type of material are conveyed to the printing units in step 101. The printing units may here be arranged stationarily at a conveyor, the containers being conveyed to and away from the individual printing units during conveyance. It is also imaginable that a conveyor, e.g. a carousel, has arranged thereon container holders which each have a printing station, each of these printing stations comprising a plurality of printing units for printing at least one basic ink and at least one colored ink.

(12) In step 102, the containers of the first type of material are then printed on with a first basic ink, which is compatible therewith, in a direct-printing process. The first basic ink is here of such a physical and chemical nature that it will adhere particularly well to the first type of material. The containers in question are made e.g. of HDPE. In addition, the first basic ink is white in color, so that the colored inks printed on in the subsequent step 103 will appear as brilliant as possible.

(13) In step 103, the containers of the first type of material are then printed on, again in a direct-printing process, with a plurality of colored inks, such as cyan, magenta, yellow and black. Special colors are, however, imaginable as well. In steps 102 and 103, the printing inks are printed on, one on top of the other in several layers, so that finally a multi-color direct print will be created.

(14) Direct-printing process means here that the containers are printed on with direct-printing heads that work according to a digital or ink jet printing process. Preferably, each of the direct-printing heads comprises four rows of nozzles with e.g. 1024 printing nozzles. However, also any other suitable configuration of the printing nozzles is imaginable.

(15) When the containers of the first type of material have been finished, a change to the containers of the second type of material will take place in steps 200, 300 or 400. These steps will be explained hereinafter in more detail making reference to FIGS. 2, 3 and 4. When a change to the containers of the second type of material takes place, the first basic ink is replaced by a second basic ink which is compatible with the second type of material. The second basic ink is chemically and physically compatible with the first basic ink such that both basic inks can be mixed so as to form a single phase, so that neither accumulations of color particles nor color particles of increased size will be caused. A change is thus substantially simplified, since there is no need for removing the first basic ink completely from the respective printing unit.

(16) After the change, the containers of the second type of material are conveyed, according to the above described step 101, to the printing units in step 104. There, the containers are first printed on with the second basic ink compatible with the second type of material in step 105, in a manner similar to step 102, but with the second basic ink instead of the first basic ink. Subsequently, the containers of the second type of material are printed on in step 106 with the same colored inks as in step 103. In other words, there is no change of colored inks, since the latter are also compatible with the second basic ink and adhere to it.

(17) Subsequently, the method allows changing back to the containers of the first type of material, i.e. a change to the first basic ink takes place, or changing to a further type of material and to a further basic ink compatible with the further type of material.

(18) FIG. 2 shows, as a flowchart, the substeps of the method 100 according to FIG. 1 for changing to the containers of the second type of material according to a first variant 200.

(19) First, the direct printing head of the printing unit has fed thereto the first basic ink from a first ink supply in step 201. The first ink supply may e.g. comprise a reservoir from which the first basic ink is pumped to the direct-printing head by means of the ink feed unit. This is done during the above-described step 102.

(20) Upon changing to the second basic ink, the first basic ink is then first emptied from the printing unit in step 202. This is done from all supply sections and lines into which the second basic ink will be filled subsequently. For example, emptying takes place into a waste container or the like.

(21) Following this, the ink feed unit is switched over to the second ink supply in step 203. This is done e.g. by means of a directional valve or some other suitable unit. Also the second ink supply may comprise a reservoir from which the second basic ink is pumped to the direct-printing head by means of the ink feed unit.

(22) In addition, the printing unit is flushed in step 204. In so doing, all the supply sections of the ink feed unit, which are used by the first and the second basic ink in common, are flushed. It will be advisable to execute flushing with the second basic ink, since the latter is chemically and physically compatible with the first basic ink. For example, when the emptying step 202 is carried out, 20% of the first basic ink still remain in the printing unit. It follows that, during flushing, the remaining 80% will be filled with the second basic ink. When the two basic inks have been mixed, the mixture is emptied once more and refilling with the second basic ink takes place. Subsequently, the percentage of first basic ink in the mixture will only be 4%. The steps of emptying and refilling with the second basic ink are continued until the residual amount of the first basic ink falls below a desired percentage of the total mixture.

(23) Subsequently, the direct-printing head of the printing unit has fed thereto the second basic ink from the second ink supply in step 205. This is done during the above-described step 105, so as to print the second basic ink onto the containers of the second type of material.

(24) FIG. 3 shows, as a flowchart, the substeps of the method 100 according to FIG. 1 for changing to the containers of the second type of material according to a second variant 300.

(25) This differs from the first variant 200 essentially insofar as, at the printing unit, the first basic ink is mixed from a basic component and a first additive and the second basic ink is mixed from the same basic component and a second additive.

(26) First, the direct-printing head has fed thereto the first basic ink (during the above described step 102) in step 301, the first basic ink being mixed from the basic component and the first additive. The basic component is e.g. a carrier liquid that can be used for both the first and the second basic ink. The basic component is taken from a suitable supply and the first additive from a further supply via suitable supply sections of the ink feed unit, whereupon they are mixed with each other and fed to the direct-printing head.

(27) Upon changing to the containers of the second type of material, the first basic ink is first emptied, in step 302, from the printing unit, in particular from the supply sections, which will subsequently also be used with the second basic ink.

(28) Following this, the ink feed unit is switched over to the second additive in step 303. Similar to step 301, the basic component is then mixed with the second additive and fed to the direct-printing head. In so doing, the second additive is taken from a further supply.

(29) In the subsequent step 304, the printing unit is then flushed with the second basic ink, i.e. with a mixture of the basic component and the second additive. This is done in a similar way as described above in step 204. Also in this case, the printing unit can be emptied more than once and refilled with the second basic ink consisting of the mixture of the basic component and of the second additive.

(30) In the further step 305, the direct-printing head of the printing unit has then fed thereto the second basic ink, which is mixed from the basic component and the second additive (during the above described step 105).

(31) FIG. 4, shows, as a flowchart, the substeps of the method 100 according to FIG. 1 for changing to the containers of the second type of material according to a third variant 400.

(32) This differs from the above described variants 200 and 300 insofar as the printing unit used here for printing the second basic ink differs from that used for the first basic ink. First, in step 401, the first basic ink is printed with a first printing unit, as described in the above described step 102.

(33) When, subsequently, containers of the second type of material are to be printed on, step 402 will either switch over to a second printing unit, which is already arranged at the printing position, or the first printing unit will be exchanged for the second printing unit at the same printing position.

(34) Subsequently, printing the second basic ink by means of the second printing unit, as described above in step 105, is started in step 403.

(35) FIG. 5 shows an embodiment of a direct-printing machine 1 according to the present invention in a top view.

(36) What can be seen is that the containers 2 are first applied by means of the infeed starwheel 3 to the container holders 5 on the conveyor 4, which is configured as a carousel. The conveyor 4 rotates about the axis A, so as to convey the containers 2 to the individual printing units 6.sub.B1, 6.sub.B2, 6.sub.C, 6.sub.M, 6.sub.Y and 6.sub.K. It is imaginable that further printing units, e.g. for special colors, are additionally arranged at the conveyor 4. The printing units 6.sub.B1, 6.sub.B2, 6.sub.C, 6.sub.M, 6.sub.Y, 6.sub.K operate according to the direct-printing method and are each provided with at least one direct-printing head and an ink feed unit (which is here not shown in detail).

(37) There, the containers 2 are printed on by means of one of the printing units 6.sub.B1, 6.sub.B2, selectively with a first basic ink or a second basic ink, depending on the type of material. The first and the second basic ink are here configured as a primer and they are compatible with containers 2 of a first type of material and of a second type of material, respectively. Subsequently, the containers 2 are conveyed to the printing units 6.sub.C, 6.sub.M, 6.sub.Y and 6.sub.K, where they are printed on with colored inks cyan, magenta, yellow and black in a direct-printing process. In this way, a multi-color direct print is created on the containers 2.

(38) Following this, the containers 2 are moved past the curing station 7 so as to cure the first and the second basic ink, respectively, as well as the colored inks. Alternatively, the curing station may also be arranged separately from the conveyor 4. It is also imaginable that a respective pinning station is arranged between the printing units 6.sub.B1, 6.sub.B2, 6.sub.C, 6.sub.M, 6.sub.Y, 6.sub.K in order to cure the previously applied printing ink at least partially for the printing of the subsequently applied printing ink. As a result, the printing inks will not run into one another and the quality will be improved.

(39) After the direct print on the containers 2 has been cured, the containers are advanced by the discharge starwheel 9 so as to undergo further treatment steps.

(40) In addition, the control unit 8 can be seen, which controls the direct-printing machine 1 according to the method 100 described above in FIG. 1 and the substeps according to the third variant 400 of FIG. 4. To this end, the control unit 8 is configured as a digital machine control.

(41) The direct-printing machine 1 according to FIG. 5 is used as follows: first, containers 2 of the first type of material are printed on according to the direct-printing method, the first basic ink being here applied first by means of the printing unit 6.sub.B1 and the colored inks being applied subsequently by means of the printing units 6.sub.C, 6.sub.M, 6.sub.Y, 6.sub.K. In the case of a change to the containers of the second type of material, it will then suffice to switch over from the printing unit 6.sub.B1 with the first basic ink to the printing unit 6.sub.B2 with the second basic ink. As a result, a change to containers of a different type of material will take place particularly quickly.

(42) FIG. 6 shows a further embodiment of a direct-printing machine 1 according to the present invention in a top view. This differs from the embodiment according to FIG. 5 essentially insofar as only a single printing unit 60, 70 is here configured, which can be switched over for selectively printing the first or the second basic ink. All the other elements of the direct-printing machine correspond to the above described FIG. 5.

(43) The printing units 60, 70 will be explained hereinafter in more detail making reference to FIG. 7A, 7B:

(44) FIG. 7A shows the printing unit 60 that operates according to the substeps 200 in FIG. 2. It can be seen that the ink feed unit 63 comprises a first reservoir 633 with a supply of the first basic ink B1, a first conveying system 631 for the first basic ink, a second reservoir 634 with a supply of the second basic ink B2, a second conveying system 632 for the second basic ink and a direct-printing head 62 which is selectively usable for the first or the second basic ink B1, B2.

(45) In addition, the printing unit 60 comprises the cleaning unit 64 and the waste container 65. Making use of the cleaning unit 64, the first basic ink B1 or the second basic ink B2 can be emptied from the printing unit according to step 202. The cleaning unit 64 comprises e.g. a collecting basin for collecting ink from the direct-printing head 62. Likewise, it is imaginable that the cleaning unit 64 comprises a connection to the ink feed unit 63, into which excess basic ink can be discharged during emptying.

(46) It can also be seen that, according to the dashed arrows, the first and the second basic ink B1, B2 can be pumped from the direct-printing head 62 via the first and second conveying systems 631, 632 back into the reservoirs 633, 634. In this way, the printing ink can be caused to circulate.

(47) The ink feed unit 63 can thus selectively switch to the supply of the direct-printing head 62 with the first basic ink B1 or with the second basic ink B2. By way of example, the direct-printing head 62 is first supplied by the conveying system 631 with the first basic ink from the first reservoir 633.

(48) When changing, the first basic ink B1 is first emptied towards the cleaning unit 64 and into the waste container 65 (step 202). Then, the ink feed unit 63 is switched to the conveying system 632 and the second reservoir 634 with the second basic ink B2. Subsequently, the printing unit is first flushed according to step 204 and then supplied with the second basic ink B2 from the second reservoir 634 according to step 205.

(49) When switching back to the first basic ink B1 takes place, the above steps are executed in reverse order.

(50) FIG. 7B shows an alternative embodiment of the printing unit 70 according to FIG. 6 in a top view.

(51) The printing unit 70 differs from the embodiment of the printing unit 60 according to FIG. 7A with respect to the ink feed unit 73 essentially insofar as a basic component G from the reservoir 733 is here mixed with the first additive Z1 from reservoir 734 or the additive Z2 from reservoir 735, so as to selectively mix therefrom the first or the second basic ink at the printing unit 70.

(52) It can be seen that the conveying system 731 mixes, for containers of the first type of material, the first basic ink from the basic component G originating from reservoir 733 and the additive Z1 originating from reservoir 734. As a result, the first basic ink is formed and the direct-printing head 72 is supplied therewith.

(53) In a corresponding manner, when a change to containers of the second type of material and the second basic ink takes place, the basic component G is obtained from reservoir 733 by means of the conveying system 732 and has the additive Z2 originating from reservoir 735 admixed thereto.

(54) In the case of a change, a course of action in accordance with the substeps of the second variant 300 according to FIG. 3 is taken. First, the direct-printing head 72 has fed thereto the first basic ink, which is mixed from the basic component G and the additive Z1. Here, containers of the first type of material are printed on with the first basic ink.

(55) When changing to the containers of the second type of material, the first basic ink is first emptied from the printing unit 70 according to step 302 by discharging it, as described above, via the cleaning unit 74 into the waste container 75. Subsequently, the ink feed unit 73 is switched over to the second additive Z2 from the reservoir 735 (step 303) and the printing unit 70 is flushed therewith (step 304). Then, the direct-printing head 72 has fed thereto the second basic ink, which is mixed from the basic component G and the second additive Z2, according to step 305.

(56) By means of the printing units 60, 70 according to FIG. 7A-7B, printing with the first basic ink can be switched over to printing with the second basic ink without major effort.

(57) Due to the fact that, in the above described embodiments, the first and the second basic ink are chemically and physically compatible, it is possible to flush the printing unit 60, 70 with the second basic ink when changing from the first to the second basic ink, and, vice versa, with the first basic ink when changing from the second to the first basic ink. Hence, the printing unit can be switched over without any additional flushing solutions or the like being necessary.

(58) It goes without saying that the features mentioned in the above described embodiments are not limited to these combinations, but can be also be provided individually or in arbitrary other combinations.