PRINTING MACHINE AND METHOD FOR CHANGING A COLOR SEQUENCE WITHIN A PRINTING PROCESS

Abstract

A printing machine (10) for printing on a substrate having the form of a web (12) is described. It comprises a web entry unit (14) for receiving the web (12) on which a printing process is to be performed and a web exit unit (20) for dispensing the web (12) after the printing process. Furthermore, at least two printing units (26, 28, 30, 32, 34, 36, 38) are provided, wherein each of the printing units (26, 28, 30, 32, 34, 36, 38) is configured for applying an ink of a predetermined color on the web (12). Additionally at least two web paths (A, B) are provided between the web entry unit (14) and the web exit unit (20), each of the web paths (A, B) passing by all of the printing units (26, 28, 30, 32, 34, 36, 38). The web paths (A, B) pass the printing units (26, 28, 30, 32, 34, 36, 38) in a differing sequence. Moreover, a method for changing a color sequence within a printing process is presented. According to this method, the web (12) is arranged along an alternative web path (A, B) passing by the printing units (26, 28, 30, 32, 34, 36, 38) in a differing sequence, whereas a travelling direction of the web remains the same.

Claims

1. A printing machine, especially a label printing machine and a machine for printing flexible packaging, for printing on a substrate having a form of a web, the printing machine comprising: a web entry unit for receiving the web on which a printing process is to be performed, a web exit unit for dispensing the web after the printing process, and at least two printing units, wherein each of the at least two printing units is configured for applying an ink of a predetermined color on the web, wherein at least two web paths are provided between the web entry unit and the web exit unit, each of the at least two web paths passing by the at least two printing units, and wherein the at least two web paths pass by the at least two printing units in a differing sequence, whereas a traveling direction of the web remains the same.

2. The printing machine according to claim 1, wherein the at least two printing units are arranged along a substantially straight or arched line.

3. The printing machine according to claim 1, wherein the entry unit and the exit unit are arranged on the same side of the at least two printing units.

4. The printing machine according to claim 1, wherein a gap is located between the at least two printing units, wherein only a first one of the at least two web paths comprises a portion extending through the gap.

5. The printing machine according to claim 4, wherein the first one of the at least two web paths, along a travelling direction of the first one of the at least two web paths, extends through the gap, subsequently passes by a second one of the at least two printing units and subsequently passes by a first one of the at least two printing units.

6. The printing machine according to claim 5, wherein the first one of the at least two web paths, along the travelling direction of the first one of the at least two web paths, extends through the gap after having passed by the first one of the at least two printing units.

7. The printing machine according to claim 4, wherein a second one of the at least two web paths, along a travelling direction of the second one of the at least two web paths, passes by a first one of the at least two printing units and subsequently passes by a second one of the at least two printing units.

8. The printing machine according to claim 1, wherein the at least two printing units are ink jet printing units or laser printing units.

9. The printing machine according to claim 1, further comprising: at least one pinning unit, wherein the pinning unit is arranged adjacent to one of the at least two printing units.

10. The printing machine according to claim 9, further comprising: at least two coupling units for mounting the at least one pinning unit within the printing machine, wherein the at least one pinning unit may be selectively coupled to any one of the at least two coupling units.

11. The printing machine according to claim 1, wherein the at least two printing units include at least three printing units, being subdivided into two printing unit groups, wherein the at least two web paths pass by the at least two printing unit groups in a differing sequence.

12. The printing machine according to claim 1, further comprising: a curing unit, wherein the curing unit is arranged between the at least two printing units and the web exit unit in respect of the at least two web paths.

13. The printing machine according to claim 1, wherein each of the at least two printing units has a single, fixed position within the printing machine.

14. The printing machine according to claim 1, wherein the at least two printing units include one single printing unit per color.

15. The printing machine according to claim 1, wherein the at least two printing units are configured for applying an ink of white color.

16. A method for changing a color sequence within a printing process, especially a label printing process, performed by a printing machine configured for printing on a substrate having a form of a web and comprising at least two printing units, wherein each of the at least two printing units is configured for applying an ink of a predetermined color on the web, and wherein the web is arranged along an alternative web path passing by the at least two printing units in a differing sequence, whereas a travelling direction of the web remains the same.

Description

[0037] The invention will now be explained with reference to two embodiments which are shown in the attached drawings. In the drawings,

[0038] FIG. 1 shows a printing machine according to the invention, wherein a method according to the invention can be performed with this printing machine, and

[0039] FIG. 2 shows a slightly modified printing machine according to the invention, wherein also in connection with the slightly modified printing machine a method according to the invention can be performed.

[0040] FIG. 1 shows a printing machine 10 which is configured as a label printing machine.

[0041] Furthermore, the printing machine is configured for printing on a substrate having the form of a web 12.

[0042] The printing machine 10 comprises a web entry unit 14 for receiving the web 12 on which a printing process is to be performed.

[0043] The web entry unit 14 has an entry roller 16 and two auxiliary entry rollers 18a, 18b.

[0044] The entry roller 16 and the auxiliary entry rollers 18a, 18b are rotatable around respective axes of rotation which are arranged in parallel.

[0045] In the example shown the auxiliary entry rollers 18a, 18b are arranged below the entry roller 16. This is one possibility, but the entry rollers or at least one of them could be also be arranged above the entry roller according to another embodiment. The auxiliary rollers mainly have the function to have a good wrapping of the entry roller, to avoid any slipping of the substrate on the roller and so to ensure a stable web tension.

[0046] Moreover, auxiliary entry roller 18a is arranged on a first lateral side of an axis 16a of rotation of the entry roller 16 wherein auxiliary entry roller 18b is arranged on a second lateral side of the axis 16a of rotation. The second lateral side is opposed to the first lateral side.

[0047] The printing machine 10 also comprises a web exit unit 20 for dispensing the web 12 after the printing process.

[0048] The web exit unit 20 is configured in a similar manner as the web entry unit 14.

[0049] It comprises an exit roller 22 being rotatable around a corresponding axis 22a of rotation.

[0050] Furthermore, two auxiliary exit rollers 24a, 24b are provided.

[0051] The auxiliary exit rollers 24a, 24b are rotatable around respective axes of rotation which are arranged in parallel to the axis 22a of rotation of the exit roller 22.

[0052] In the example shown the auxiliary exit rollers 24a, 24b are arranged below the exit roller 22. Moreover, the auxiliary exit roller 24a is arranged on a first lateral side of the axis 22a of rotation of the exit roller 22 and the auxiliary exit roller 24b is arranged on a second lateral side of the axis 22a of rotation. The second lateral side is opposed to the first lateral side.

[0053] Additionally, the printing machine 10 comprises a total of seven printing units being designated by reference signs 26 to 38.

[0054] Printing unit 26 is configured for applying an ink of white color on the web 12. Consequently the printing unit 26 is also designated a white printing unit or by the letter W.

[0055] Printing unit 28 is configured for applying an ink of orange color on the web 12. Thus, the printing unit 28 is also designated an orange printing unit or by the letter O.

[0056] Printing unit 30 is configured for applying an ink of violet color on the web 12. Accordingly, the printing unit 30 is also designated a violet printing unit or by the letter V.

[0057] Printing unit 32 is configured for applying an ink of cyan color on the web 12. The printing unit 32 is also designated a cyan printing unit or by the letter C.

[0058] Printing unit 34 is configured for applying an ink of magenta color on the web 12. Consequently the printing unit 34 is also designated a magenta printing unit or by the letter M.

[0059] Printing unit 36 is configured for applying an ink of yellow color on the web 12. Therefore, the printing unit 36 is also designated a yellow printing unit or by the letter Y.

[0060] Printing unit 38 is configured for applying black ink on the web 12. Thus, the printing unit 38 is also designated a black printing unit or by the letter K. This designation is due to the fact that black ink often is also called key.

[0061] Consequently, the printing machine 10 comprises one single printing unit 26 to 38 per color.

[0062] The color sequence of the print section as described by example could also be different. The example is described by using OV-CMYK, but all other combinations are possible, e.g. also CMYK-OV.

[0063] In the examples shown in the figures, the printing units 26 to 38 are ink jet printing units.

[0064] Furthermore, all printing units 26 to 38 are arranged along a slightly arched line 40.

[0065] Each of the printing units 26 to 38 has a single, fixed position along this line 40 and thus within the printing machine 10.

[0066] Moreover, the respective front sides of the printing units 26 to 38, i.e. the sides from which the printing units 26 to 38 may apply ink to the web 12 are all oriented towards the same side, in the example shown a lower side of the printing machine 10.

[0067] Furthermore, printing units 28 and 30 are arranged adjacent to one another and form a first printing unit pair.

[0068] In an analogous manner, printing units 32 and 34 are arranged adjacent to one another and form a second printing unit pair.

[0069] Also printing units 36 and 38 are arranged adjacent to one another. They form a third printing unit pair.

[0070] Printing unit 26 is not paired with another one of the printing units 28 to 38.

[0071] Furthermore, a gap 42 is provided between the printing unit 26 and the first printing unit pair, more precisely the printing unit 28. This gap 42 is configured such that the web 12 may pass therethrough as will be explained below.

[0072] The gap 42 also separates the printing units 26 to 38 into two printing unit groups, wherein a first printing unit group is formed by printing units 28 to 38 and a second printing unit group is formed by printing unit 26.

[0073] It is noted that also between the printing units 30 and 32 as well as between the printing units 34 and 36 a certain spacing is provided. However, this spacing is considerably smaller than the gap 42. As will be explained later, the web 12 does not extend through these spacings. Thus, the spacings will not be designated as gaps.

[0074] In the configuration of the printing machine 10 as shown in the Figures, the printing units 26 to 38 are arranged above the entry unit 14 and the exit unit 20. In other words, the entry unit 14 and the exit unit 20 are arranged on the same side of the printing units 26 to 28 which is a lower side in the examples shown.

[0075] The printing machine 10 also comprises a pinning unit 44. The pinning unit 44 is used for pre-curing ink applied to the web 12.

[0076] In the example of FIG. 1 the pinning unit 44 is arranged adjacent to printing unit 26.

[0077] The printing machine 10 is also equipped with a curing unit 46.

[0078] The curing unit 46 comprises a supporting roller 48 which is optionally chilled and a curing energy source 50.

[0079] In the examples shown, the curing energy source 50 comprises a UV light source configured for curing UV light sensitive inks.

[0080] Moreover, within the printing machine 10 two alternative web paths A, B are provided between the web entry unit 14 and the web exit unit 20.

[0081] A first web path A along which the web 12 may travel through the printing machine 10 starts at the entry unit 14 where the web 12 is wound around the first auxiliary entry roller 18, the entry roller 16 and the second auxiliary entry roller 18b.

[0082] Thereafter, the web path A extends to a first deviating roller 52 which is generally arranged above the entry unit 14.

[0083] The first deviating roller 52 is also arranged at a backside of the printing units 26 to 38, i.e. above the printing units 26 to 38.

[0084] From there, the first web path A extends through the gap 42 to a second deviating roller 54 being arranged at an end of the gap 42.

[0085] In doing so, the first web path A has circumvented the printing unit 26 at its backside.

[0086] The first web path A continues to pass by the printing units 28 to 38 at a respective front side thereof until it reaches a third deviating roller 56.

[0087] In between the deviating rollers 54 and 56, the web 12 travelling along the first web path A is supported by a total of three supporting rollers 58a, 58b, 58c.

[0088] Using deviating rollers 54 and 56 and supporting rollers 58a, 58b, 58c the web 12 travelling along the first web path A is precisely positioned with respect to the printing units 28 to 38.

[0089] The first web path A further extends from the third deviating roller 56 to a fourth deviating roller 60 which is substantially arranged below the curing unit 46.

[0090] From there it continues to a fifth deviating roller 62 and further to a sixth deviating roller 64.

[0091] The portion of the first web path A extending between the fifth deviating roller 62 and the sixth deviating roller 64 passes by the front side of the printing unit 26 and by the pinning unit 44 which is arranged adjacent to the printing unit 26.

[0092] Consequently, white ink can be applied to the web 12 and pre-cured by the pinning unit 44.

[0093] After that, the first web path A continues to the curing unit 46, more precisely to the supporting roller 48.

[0094] The ink applied to the web 12 by the printing units 26 to 38 can now be fully cured.

[0095] From the supporting roller 48, the first web path A extends over a seventh deviating roller 66 and an eights deviating roller 68 to a ninth deviating roller 70.

[0096] Thereafter, it passes again through the gap 42 until it reaches a tenth deviating roller 72.

[0097] Subsequently, the first web path A extends to the exit unit 20.

[0098] Since the first web path A first passes by the printing units 28 to 38, i.e. by the printing units being adapted for applying ink of orange, violet, cyan, magenta, yellow and black color to the web 12 and subsequently passes by printing unit 26, which is adapted for applying white ink to the web, the first web path A may also be designated as a “white last” path.

[0099] As an alternative to the first web path A a second web path B is provided.

[0100] The second web path B also starts at the entry unit 14 where the web 12 is wound around the first auxiliary entry roller 18a, the entry roller 16 and the second auxiliary entry roller 18b.

[0101] From there it directly extends to the fifth deviating roller 62 and subsequently travels along the front sides of all printing units 26 to 38 until it reaches the third deviating roller 56.

[0102] During its travel along the printing units 26 to 38, the second web path B is supported by the sixth deviating roller 64 and the support rollers 58a to 58c.

[0103] Consequently, the web 12 travelling along the second web path B will receive white ink first. Subsequently, it may receive ink of the colors orange, violet, cyan, magenta, yellow and black.

[0104] Thus, the second web path may be called a “white first” path.

[0105] Again, the white ink is pre-cured by the pinning unit 44 being arranged adjacent to the printing unit 26.

[0106] From the third deviating roller 56 the second web path B extends over the fourth deviating roller 60 and the seventh deviating roller 66 until it reaches the curing unit 46, more precisely the supporting roller 48.

[0107] After having passed the supporting roller 48 it reaches the exit unit 20 via the eights deviating roller 68, the ninth deviating roller 70 and an eleventh deviating roller 74.

[0108] It can be seen from the above explanations that each of the web paths A, B passes by all of the printing units 26 to 38. Consequently, independent from the web path A, B used, all colors may be printed on the web 12.

[0109] However, the sequences by which the printing units 26 to 38 are passed differ.

[0110] In the present example, in which the printing units 26 to 38 are subdivided into a first printing unit group and a second printing unit group, the differing sequence also applies to these printing unit groups.

[0111] It is noted that in this context only the first web path A comprises a portion extending through the gap 42.

[0112] Furthermore, along both web paths A, B the curing unit 46 is arranged between the printing units 26 to 38 and the web exit unit 20.

[0113] In FIG. 2 a second example of the printing machine 10 is shown.

[0114] The printing machine 10 according to the second example only differs from the printing machine 10 according to the first example in that two coupling units 76, 78 for mounting the pinning unit 44 within the printing machine 10 are provided.

[0115] Thus, the pinning unit 44 may selectively be coupled to one of the coupling units 76, 78.

[0116] In other words, depending on the printing job to be performed and on the web path A, B used the pinning unit 44 can either be arranged adjacent to the printing unit 26 via coupling unit 76 or adjacent to the printing unit 28 via coupling unit 78.

[0117] A method for changing a color sequence within a printing process can be performed in connection with both examples of the printing machine 10.

[0118] This method starts form a given color sequence within a printing process which is for example determined in that the web 12 is arranged within the printing machine 10 such that it travels along the first web path A.

[0119] In order to change the color sequence, the web 12 will be re-arranged to the second web path B.

[0120] The same applies if the method starts from a given color sequence being determined in that the web 12 is arranged along the second web path B. Then, the web 12 will be re-arranged to the first web path A.

[0121] In connection with the above examples the web paths A, B with differing color sequences have been explained using the printing unit 26 being configured for applying white ink to the substrate as an example. However, it is clear that a change in color sequence can also be performed with respect to any other color or group of colors. To this end, for example the position of the gap 42 can altered.