METHOD AND APPARATUS FOR ATTACHING A PRINTING PLATE TO A PRINTING CYLINDER

Abstract

A method for attaching a printing plate (12), especially a flexographic printing plate, to a printing cylinder (14) is described. In a first step, the printing plate (12) is provided in a substantially flat condition. Thereafter, an outer circumference of the printing cylinder (14) is arranged adjacent to an edge of the printing plate (12). Subsequently, the printing cylinder (14) is translatorily moved over the printing plate (12) while rotating such that the printing plate (12) is rolled-up on the printing cylinder (14). Additionally, an apparatus (10) for attaching a printing plate (12) to a printing cylinder (14) is presented. The apparatus (10) comprises a printing plate support unit (16) having a substantially flat support surface (18) for supporting the printing plate (12) to be mounted on the printing cylinder (14), and a printing cylinder support unit (36) for supporting and moving the printing cylinder (14). The printing cylinder support unit (36) comprises a translatory drive means (42) for translatorily moving the printing cylinder (14) in a direction parallel to the support surface (18).

Claims

1. A method for attaching a printing plate, especially a flexographic printing plate, to a printing cylinder, the method comprising: providing the printing plate in a substantially flat condition, arranging an outer circumference of the printing cylinder adjacent to an edge of the printing plate, and subsequently translatorily moving the printing cylinder over the printing plate while rotating the printing cylinder such that the printing plate is rolled-up on the printing cylinder, wherein one or more 3-dimensional images of the printing plate and/or the printing cylinder are/is captured.

2. The method according to claim 1, wherein the printing plate is provided on a substantially flat support surface of a printing plate support unit, in particular on top surface of a vacuum table.

3. The method according to claim 2, wherein the printing plate is moved to a predefined position before the printing cylinder is provided adjacent to the edge of the printing plate.

4. The method according to claim 3, wherein the printing plate is aligned with a reference mark, especially wherein the reference mark is projected on the support surface and/or on the printing plate.

5. (canceled)

6. The method according to claim 1, wherein at least one 3-dimensional image is compared to a digital representation of the printing plate and/or the printing cylinder in order to control or check the attachment of the printing plate.

7. An apparatus for attaching a printing plate to a printing cylinder, the apparatus comprising: a printing plate support unit having a substantially flat support surface for supporting the printing plate to be mounted on the printing cylinder, and a printing cylinder support unit for supporting and moving the printing cylinder, and having a rotational drive means for rotating the printing cylinder, wherein the printing cylinder support unit comprises a translatory drive means for translatorily moving the printing cylinder in a direction parallel to the support surface and a 3D camera unit configured for capturing a 3-dimensional image of the printing plate and/or the printing cylinder.

8. The apparatus according to claim 7, further comprising: an adhesive application unit for applying an adhesive, in particular an adhesive tape, to the printing cylinder or the printing plate.

9. The apparatus according to claim 7, further comprising: a printing cylinder handling unit for inserting a printing cylinder into the printing cylinder support unit and withdrawing a printing cylinder from the printing cylinder support unit, in particular wherein the printing cylinder handling unit comprises an industrial robot.

10. The apparatus according to claim 7, further comprising: a feeding unit for automatically arranging a printing plate on the support surface.

11. The apparatus according to claim 7, wherein the printing plate support unit comprises a vacuum table, and wherein the substantially flat support surface is a top surface of the vacuum table.

12. The apparatus according to claim 7, wherein the printing plate support unit is movable in two directions being parallel to the support surface, in particular a longitudinal and a transversal direction of the support surface.

13. The apparatus according to claim 7, further comprising: a projector unit being configured and arranged for projecting an image of a printing plate on the support surface and/or a printing plate provided thereon.

14. (canceled)

15. The apparatus according to claim 7, further comprising: a control unit being coupled to the 3D camera unit and being configured for comparing a 3-dimensional image captured by the 3D camera unit to a digital representation of the printing plate and/or the printing cylinder.

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 is a schematic top view of an apparatus according to a first embodiment of the invention which can be used for performing a method according to the invention,

[0039] FIG. 2 is a schematic side view of an apparatus according to a second embodiment of the invention which can also be used for performing a method according to the invention, and

[0040] FIGS. 3a, 3b, and 3c schematically illustrate the method according to the invention.

[0041] FIG. 1 shows an apparatus 10 for attaching a printing plate 12 to a printing cylinder 14.

[0042] In the present example the printing plate 12 is a flexographic printing plate and the printing cylinder 14 is a printing cylinder of a flexographic printing machine.

[0043] The apparatus 10 comprises a printing plate support unit 16 having a substantially flat support surface 18.

[0044] The printing plate support unit 16 comprises a vacuum table 20, wherein the support surface 18 is formed by a top surface 22 of the vacuum table 20.

[0045] The top surface 22 is oriented in a substantially horizontal manner and comprises a plurality of suction openings 24 which are configured for aspiring the printing plate 12.

[0046] For the ease of representation only two of the suction openings 24 are designated with a reference sign.

[0047] The suction openings 24 are fluidically connected to a vacuum pump 26.

[0048] Furthermore, a shut-off valve (not shown) is fluidically interposed between each of the suction openings 24 and the vacuum pump 26.

[0049] By operating the shut-off valves, each of the suction openings 24 may be selectively connected to the vacuum pump 26, i.e. each of the suction openings 24 may individually and selectively be put in a condition in which it may aspire the printing plate 12 or in a condition where it does not aspire the printing plate 12.

[0050] Moreover, the printing plate support unit 16 is coupled to a first support drive 28 and a second support drive 30.

[0051] The first support drive 28 is configured for moving the printing plate support unit 16 along an x direction and the second support drive 30 is configured for moving the printing plate support unit 16 along a y direction.

[0052] The x direction and the y direction are substantially parallel to the support surface 18. In this respect the x direction may be designated a transversal direction and the y direction a longitudinal direction.

[0053] In the present example the printing plate 12 to be mounted on the printing cylinder 14 is arranged in on the support surface 18 i.e. on the top surface 22 of the vacuum table 20.

[0054] The apparatus 10 also comprises a feeding unit 32 for automatically arranging the printing plate 12 on the support surface 18.

[0055] The feeding unit 32 comprises a conveyor belt 34 which is configured for moving the printing plate 12 substantially along they direction and placing it on the support surface 18.

[0056] Furthermore, the apparatus 10 comprises a printing cylinder support unit 36 for supporting and moving the printing cylinder 14.

[0057] The printing cylinder support unit 36 has a first support structure 38a for supporting a shaft end 14a of the printing cylinder 14.

[0058] The printing cylinder support unit 36 has also a second support structure 38b for supporting a shaft end 14b of the printing cylinder 14.

[0059] The shaft ends 14a, 14b are arranged on opposing ends of a shaft of the printing cylinder 14. Consequently, the support structures 38a, 38b are also arranged on opposing sides of the printing cylinder 14.

[0060] Moreover, the support structures 38a, 38b are arranged on opposing sides of the printing plate support unit 16.

[0061] Both support structures 38a, 38b are coupled to respective guide means 40a. 40b which are guide rails in the present example.

[0062] The guide means 40a, 40b substantially extend over the entire length of the printing plate support unit 16 in the y direction.

[0063] Moreover, the printing cylinder support unit 36 comprises a translatory drive means 42 for translatorily moving the support structures 38a, 38b and the printing cylinder 14 supported therewith in they direction.

[0064] Thus, the printing cylinder 14 may travel over the entire length of the printing plate support unit 16 in the y direction.

[0065] The printing cylinder support unit 36 also has a rotational drive means 44. The printing cylinder 14 may be rotationally coupled to the rotational drive means 44 such that it may be rotated.

[0066] Furthermore, the apparatus 10 has a printing cylinder handling unit 46 comprising an industrial robot.

[0067] The printing cylinder handling unit 46 is configured for inserting the printing cylinder 14 into the printing cylinder support unit 36 and withdrawing the printing cylinder 14 therefrom.

[0068] Moreover, the apparatus 10 comprises an adhesive application unit 48 for applying an adhesive to the printing cylinder 14.

[0069] In the present example the adhesive application unit 48 is configured for applying straps of an adhesive tape to an outer circumference of the printing cylinder 14. The adhesive is used for sticking the printing plate 12 on the outer circumference of the printing cylinder 14 as will be explained below.

[0070] The apparatus 10 also comprises a 3D camera unit 50.

[0071] It is configured and arranged for capturing 3-dimensional images of the printing plate 12, the printing cylinder 14 and the adhesive.

[0072] In other words, the 3D camera unit 50 is configured for monitoring the entire process being performed by the apparatus 10 and all parts being involved in this process.

[0073] The 3D camera unit 50 is connected to a control unit 52.

[0074] Also the first support drive 28, the second support drive 30, the translatory drive means 42 and the rotational drive means 44 are connected to the control unit 52.

[0075] On the control unit 52 a digital representation 54 of the printing plate 12, the printing cylinder 14 and the adhesive is provided.

[0076] In the present case this digital representation 54 comprises the printing plate 12, the printing cylinder 14 and the adhesive in a detached state, a state where the printing plate 12 is fully attached to the printing cylinder 14 via the adhesive and various intermediate states. All states forming part of the digital representation 54 are desired or ideal states.

[0077] Based on this the control unit 52 is configured for comparing a 3-dimensional image captured by the 3D camera unit 50 to the digital representation 54.

[0078] Depending on the outcome of this comparison, the control unit 52 may actuate one or more of the first support drive 28, the second support drive 30, the translatory drive means 42 and the rotational drive means 44.

[0079] Consequently, the attachment of the printing plate 12 to the printing cylinder 14 may be performed under closed-loop control wherein the 3D camera unit 50 acts as a sensor and the first support drive 28, the second support drive 30, the translatory drive means 42 and the rotational drive means 44 are actuators.

[0080] FIG. 2 shows an apparatus 10 for attaching a printing plate 12 to a printing cylinder 14 according to a second embodiment.

[0081] In the following, only the differences with respect to the first embodiment as shown in FIG. 1 will be explained. Corresponding parts will be designated with corresponding reference signs.

[0082] The apparatus 10 according to the second embodiment does not comprise a feeder.

[0083] The printing plate 12 is manually arranged on the support surface 18 by an operator 56.

[0084] In order to help the operator to correctly position the printing plate 12, a projector unit 58 is provided which is configured and arranged for projecting an image 58a of the printing plate 12 on the support surface 18 and/or the printing plate 12 provided thereon. The projector unit 58 may receive the image from the control unit 52. The image may form part of the digital representation 54.

[0085] For precisely positioning the printing plate 12, the operator 56 needs to bring the printing plate 12 substantially in registration with the image 58a.

[0086] Also the printing cylinder 14 needs to be manually arranged in the apparatus 10. In the second embodiment, the apparatus 10 does not comprise a printing cylinder handling unit.

[0087] For the remaining features and functions reference is made to the explanations given in respect of the first embodiment.

[0088] Both the apparatus 10 according to the first embodiment and the apparatus 10 according to the second embodiment may be used for performing a method for attaching the printing plate 12 to the printing cylinder 14.

[0089] As a first step of this method the printing plate 12 is provided in a substantially flat condition on the support surface 18 of the printing plate support unit 16, i.e. on the top surface 22 of the vacuum table 20.

[0090] If the apparatus 10 is configured according to the first embodiment, this is done automatically and the printing plate 12 is moved to a predefined position on the support surface 18.

[0091] If the apparatus 10 is configured according to the second embodiment, this is done by the operator 56, wherein the image 58a of the printing plate 12 is projected on the support surface 18 and/or on the printing plate 12 arranged thereon by the projector unit 58. The projected image 58a serves as a reference mark.

[0092] The operator 56 aligns the printing plate 12 with the reference mark such that the printing plate 12 is arranged in a predefined position.

[0093] At the same time, before or afterwards an adhesive is applied to the printing cylinder 14.

[0094] Thereafter, an outer circumference of the printing cylinder 14 is arranged adjacent to an edge of the printing plate 12 (see FIG. 3a).

[0095] Subsequently, the printing cylinder 14 is rotated by the rotational drive means 44 and moved translatorily by the translatory drive means 42 such that the printing plate 12 is rolled-up on the printing cylinder 14 (see arrows in FIG. 3b).

[0096] This is done until the printing cylinder 14 reaches the end of the printing plate 12, i.e. the translatory movement of the printing cylinder 14 covers the printing plate 12.

[0097] Then, the printing plate 12 is fully attached to the printing cylinder 14 (see also FIG. 3c).

[0098] During the entire course of the method, 3-dimensional images of the printing plate 12, the printing cylinder 14 and the adhesive are captured by the 3D camera unit 50.

[0099] Within predefined time intervals the 3-dimensional images are compared to the digital representation 54.

[0100] If the 3-dimensional image differs from the digital representation 54 more than a predefined tolerance, the rolling-up of the printing plate 12, i.e. the attachment of the printing plate 12 to the printing cylinder 14, is corrected by actuating one or more of the first support drive 28, the second support drive 30, the translatory drive means 42 and the rotational drive means 44.

[0101] Thus, the printing plate 12 is attached to the printing cylinder 14 under closed-loop control.

[0102] As a result of the method, the printing plate 12 is attached to the printing cylinder 14 in a precise manner.