Screen printing device having a screen printing stencil

Abstract

A screen printing device has a screen printing stencil. At least two doctor blade systems, each acting on the screen printing stencil are provided. The at least two doctor blade systems are arranged to each apply printing ink to an object to be printed in the same printing process. Each of the doctor blade systems has at least one doctor blade. Each of the doctor blades is arranged to sweep over the screen printing stencil. Each of the doctor blade systems is individually controlled by a control unit. The at least one doctor blade of each of the doctor blade systems is moved by a robot. At least respective two-dimensional motion paths of the doctor blades of each doctor blade system are each freely programmed and are established by control of the robot.

Claims

1. A screen printing device comprising: a single screen printing stencil; at least first and second separate squeegee systems, each of the at least first and second separate squeegee systems acting independently on the single screen printing stencil, each of the at least first and second separate squeegee systems being positioned to apply printing ink, in a single printing process, to an object to be printed, each of the at least first and second separate squeegee systems each having at least one squeegee, wherein each of the at least one squeegee in each of the at least first and second separate squeegee systems is positioned to sweep independently over the single screen printing stencil; a control unit for individually, separately controlling each of the at least first and second separate squeegee systems independently of each other; wherein the at least one squeegee of each of the at least first and second separate squeegee systems is moved by a respective separate one of a first and second robot; wherein a respective at least two-dimensional, mutually individual motion sequence of the respective at least one squeegee of each of the at least first and second separate squeegee systems, by mutually independent individual motion sequence of each of the respective ones of the first and second robots, is individually programmed and is separately controlled by the control unit; and wherein each of respective ones of the first and second separately controlled robots is configured as a multiple parallel arm robot having delta kinematics.

2. The screen printing device according to claim 1, wherein the respective motion path of the respective at least one squeegee of each of the at least first and second squeegee system is specified based on contours of the object to be printed by the screen printing device.

3. The screen printing device according to claim 1, wherein the single screen printing stencil is one of configured as a flat screen printing stencil and is enclosed in a stationary frame.

4. The screen printing device according to claim 1, wherein the multiple arms of each of the respective first and second robots are each connected by articulated joints to a respective one of a first and a second base, wherein the respective base of each of the respective first and second robots is arranged above moving parts of each of the first and second robots and wherein the multiple arms of each of the first and second robots each extend downward from the respective one of the first and second bases, wherein lower ends of the multiple arms of each of the first and second robots are connected to a gripper platform for each of the first and second robots, which gripper platform is smaller than the respective one of the first and second bases, wherein the at least one squeegee of each of the at least first and second squeegee systems acting on the single screen printing stencil is connected to the respective gripper platform that is moved by the relevant multiple arms of each of the first and second robots, wherein, as a drive for a motion to be executed by at least one of the multiple arms of each of the first and second of the respective robot, at least one motor, which is controlled by the control unit, is arranged in the respective one of the first and second bases.

5. The screen printing device according to claim 1, wherein each at least one squeegee of each of the at least first and second squeegee systems is guided within a separate one of first and second planes, wherein the first and second planes are arranged being spaced apart from one another and parallel to one another.

6. The screen printing device according to claim 5, wherein, with respect to a longitudinal axis of the object to be printed, the mutually parallel ones of the separate first and second planes are arranged one behind the other.

7. The screen printing device according to claim 1, wherein one of a squeegee pressure and a squeegee position and a squeegee speed are adjusted individually in each of the at least first and second squeegee systems.

8. A method for using a screen printing device according to claim 1, including using the screen printing device for printing at least one object, with each object being configured as one of a hollow object and as a round object.

9. The method according to claim 8, further including measuring at least the contours of the at least one object to be printed, specifying a respective motion path of the respective at least one squeegee of each of the at least first and second squeegee systems, based on the measuring results, using a program, and controlling the relevant robot using the control unit in accordance with the program.

10. The method according to claim 8, wherein, if the contours of the at least one object to be printed are one of uneven and discontinuous, deploying the respective at least one squeegee of each of the at least first and second squeegee systems on the single screen printing stencil only at selected positions of a print image that is to be applied to the at least one object to be printed, and being positioned to sweep over the single screen printing stencil.

11. The method according to claim 8, further including deploying each of the respective at least one squeegee of each of the at least first and second squeegee systems in the printing process one of alternatingly and at staggered intervals.

12. One of a linear printing press and a rotary table printing press, each having at least one screen printing device according to claim 1, and each having a transport system, wherein the object to be printed is held in the transport system and is guided by the transport system through the printing press, wherein the object to be printed is positioned by the transport system, during the printing process, at the single screen printing stencil of the screen printing device located in the printing press.

13. The one of the linear printing press and the rotary table printing press according to claim 12, wherein, during a printing process, the object to be printed is positioned by the transport system beneath the single screen printing stencil of the screen printing device arranged in the printing press.

14. The one of the linear printing press and the rotary table printing press according to claim 12, wherein a respective one of first and second bases of each of the respective first and second robots is arranged fixedly on a mounting frame of the one of the linear printing press and the rotary table printing press.

15. A method for using one of the linear printing press and the rotary table printing press according to claim 12 one of wherein the screen printing device, which is arranged in the one of the linear printing press and in the rotary table printing press, is used in an industrial printing process for printing mass-produced articles and wherein, in the one of the linear printing press and in the rotary table printing press, between 300 and 600 objects per minute are printed in succession by the screen printing device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the present invention are depicted in the set of drawings and will be described in greater detail below.

(2) The drawings show:

(3) FIG. 1 a first embodiment of a screen printing device;

(4) FIG. 2 a second embodiment of the screen printing device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) FIGS. 1 and 2 show two embodiments of the proposed screen printing device by way of example. In both embodiments, a screen printing stencil 01, in particular a flat printing screen stencil, is enclosed in a stationary, for example, preferably rectangular, in particular rigid frame 02 and is arranged, e.g. in a linear printing press or in a rotary table printing press. A linear printing press that includes a screen printing device is known, e.g., from DE 10 2017 214 073 A1. A rotary table printing press having a screen printing device is known, e.g., from EP 2 995 453 A1. Both types of printing presses are used for printing objects 03, each of which is configured, e.g., as a round object 03 or as a hollow object 03, in particular as a rotationally symmetrical hollow object 03. Typically, each object 03 to be printed is held in a transport system and is guided through the printing press by means of the transport system, with the object 03 to be printed being positioned at least briefly during the printing process by the relevant transport system at the screen printing stencil 01, i.e. positioned there, preferably beneath the screen printing stencil 01. During the printing process, the relevant object 03, which is rotated, e.g. about its longitudinal axis 24, during the printing process, is printed, e.g. on its lateral surface by means of the screen printing device in that the object 03 to be printed comes into rolling contact with the screen printing stencil 01. A large number of objects 03 are preferably printed in succession by the screen printing device, e.g. in a linear printing press or in a rotary table printing press between 300 and 600 of these objects 03 are printed per minute by the relevant screen printing device. The screen printing device thus operates in an industrial printing process for printing mass-produced articles, in particular round objects 03 or hollow objects 03, e.g. the respective lateral surface of bottles made of glass or of plastic, preferably bottles used for beverages or cosmetics.

(6) For applying printing ink in the same printing process to the object 03 to be printed, multiple, e.g. two, squeegee systems 04; 06, each controlled separately, i.e. individually, by a preferably digital control unit 30 are provided, each of these squeegee systems 04; 06 having at least one squeegee 07; 08, and each of said squeegees 07; 08 being positioned so as to sweep over the screen printing stencil 01. Thus, each of these squeegees 07; 08 executes a relative movement with respect to the preferably stationary screen printing stencil 01. The at least one squeegee 07; 08 of each of the squeegee systems 04; 06 is guided in each case within a plane E1; E2, said planes E1; E2 being arranged spaced apart from one another and parallel to one another. In particular, the at least one squeegee 07; 08 of each of the squeegee systems 04; 06 is guided in each case within a vertical plane E1; E2. With respect to the longitudinal axis 24 of the objects 03 to be printed, the mutually parallel planes E1; E2 are arranged in particular in a row or one behind the other along said longitudinal axis 24, so that different squeegee systems 04; 06 can each also be used to print, e.g. different areas of the object 03 to be printed.

(7) Each respective squeegee 07; 08 of each of these squeegee systems 04; 06 is guided or moved by a robot 09; 11, with a motion path 21 (indicated in FIG. 2) of each relevant squeegee 07; 08 of each squeegee system 04; 06 being freely programmed or at least freely programmable, meaning that a respective at least two-dimensional motion path 21 of each relevant squeegee 07; 08 of each squeegee system 04; 06 is established by the control of the relevant robot 09; 11. The respective motion path 21 of the squeegee 07; 08 of the relevant squeegee system 04; 06 is preferably programmed, i.e. specified, based on the contours of the object 03 to be printed with this screen printing device, so as to deploy the respective squeegee 07; 08 on the screen printing stencil 01 selectively, i.e. only at selected positions of a print image to be applied, particularly if the contour profile of the object 03 to be printed is uneven or discontinuous, and to cause said squeegee to sweep over the screen printing stencil 01 in accordance with the input programming specification through a corresponding actuation of the robots 09; 11 carried out by the control unit 30.

(8) In the preferred embodiment, each of the robots 09; 11 is configured as a parallel arm robot with rod kinematics or as what is known as a delta robot 09; 11 or a robot with delta kinematics. Delta robots 09; 11 have multiple arms 12; 13, preferably at least three, connected by means of articulated joints, in particular universal joints, to a common base 14; 16, with the shape of said arms 12; 13 being reminiscent of the Greek letter delta. The axes of a spider-like delta robot 09; 11 interact to form a closed kinematic chain. The base 14; 16 of each respective delta robot 09; 11 is arranged, in particular fixedly, above the moving parts of the relevant delta robot 09; 11, i.e. on a mounting frame 17 of a linear printing press or a rotary table printing press, for example. The multiple, preferably at least three arms 12; 13, in particular articulated arms 12; 13, each extend down, i.e. downward, from the base 14; 16. The lower ends of these arms 12; 13 are in turn connected, e.g. to a triangular or rectangular platform 18; 19, known as the gripper platform, which has a smaller surface area than the respective base 14; 16. The respective squeegee 07; 08 of each of the squeegee systems 04; 06 acting on the screen printing stencil 01 is connected to the respective platform 18; 19, each platform being moved by the relevant arms 12; 13, and is therefore guided in its respective motion behavior by the respective movement of the relevant platform 18; 19.

(9) In the aforementioned type of robot 09; 11, the drive system is as follows: If at least one motor 22; 23, electric in particular, which is controlled by the control unit 30 and is located in the base 14; 16, drives the respective axis of at least one of the articulated arms 12; 13, the platform 18; 19 disposed therebeneath moves along X and/or Y and/or Z travel paths, i.e. along one-dimensional or two-dimensional or three-dimensional travel paths, visually along the sides of a parallelogram. Depending on the number of degrees of freedom, delta robots 09; 11 may also execute rotational movements. The articulated arms 12; 13 of robots 09; 11 of this construction can be driven, i.e. moved, by a linear drive and/or by a rotary drive. Since the respective drive or motor 22; 23 for the articulated arms 12; 13 is located in the relevant base 14; 16 in each case, the articulated arms 12; 13 themselves of the proposed robots 09; 11 do not have a drive or motor 22; 23 that is controlled by the control unit 30. As a result, the mass and/or inertia of the articulated arms 12; 13 is relatively low.

(10) It is proposed that the squeegee drive of the screen printing device be formed by means of robots 09; 11, preferably by means of delta robots 09; 11. This screen printing device is used in particular for the printing of objects 03, each of which is configured as a round object 03 or as a hollow object 03. In a highly advantageous embodiment, a linear printing press or a rotary table printing press is configured as having at least one screen printing device that has the features described above.

(11) A squeegee drive implemented by means of controlled robots 09; 11 is highly precise and allows individual adjustment of a squeegee pressure and/or a squeegee position and/or a squeegee speed. Advantageously, an object 03 to be printed is first measured, at least in terms of its contours, after which the respective motion path 21 of the relevant squeegee 07; 08 of each squeegee system 04; 06 is programmed and then executed based upon the results of the measurements. In that case, it may be provided for the relevant squeegees 07; 08 of different squeegee systems 04; 06 that are involved in the same printing process to be deployed alternatingly or at staggered intervals.

(12) A robot 09; 11 configured as a parallel arm robot with rod kinematics or as a delta robot has the advantage over known articulated arm robots, particularly those in industrial use, of actually enabling the cycle speeds that are required for printing mass-produced articles in the first place, these cycle speeds typically being in the range of up to three cycles per second. Articulated arm systems of the type used in an industrial robot are not equipped for this and are therefore unsuitable for the use intended according to the invention. The extensive spatial flexibility of handling offered by articulated arm systems is not an advantage for the present intended use in a screen printing device, particularly in a screen printing device arranged in a linear printing press or rotary table printing press; on the contrary, it results in substantial limitations in terms of dynamics due to the masses to be moved in articulated arm systems. The situation is entirely different for a parallel arm robot with rod kinematics or for a delta robot. Because the respective drives of a parallel arm robot with rod kinematics or a delta robot are located outside of the arm kinematics, these parallel kinematics have only small moving masses and can therefore achieve the very high speed and dynamics that are required.

(13) Furthermore, the free programmability of a robot according to the invention, as compared with the squeegee systems known from the prior art as described in the introductory section, solves a problem that lies in the high material load on the screen mesh during the printing process. Conventional systems, such as the chain system described in DE 20 20 424 A, for example, are characterized in that the same point load is always applied to the screen mesh at the site where the squeegee is deployed. After a certain period of time, the screen typically tears at that site, resulting in an interruption of the production process being carried out with the screen printing device. In contrast, a squeegee system guided by a robot enables the squeegee deployment point to be varied geometrically within a zone defined with respect to the screen printing stencil, while the functioning of the squeegee system otherwise remains the same (e.g. with respect to maintenance of register), thereby enabling a more uniform mesh load and a longer screen service life.

(14) While preferred embodiments of a screen printing device having a screen printing stencil, in accordance with the present invention, have been set forth fully and completely hereinabove, it will be apparent to one of skill in the art, that various changes could be made thereto, without departing from the true spirit and scope of the present invention, which is accordingly to be limited only by the appended claims.