Digital web printing press, control apparatus and method for operating the digital web printing press

Abstract

A digital web printing press, control apparatus and method for operating the digital web printing press includes selecting a frequency for actuating a digital printing head at the frequency to output printing ink onto a print web, wherein a specified conveying speed for conveying the print web is ascertained based on the selected frequency and printing data, a motor driving a first roller and/or a motor driving a second roller is controlled based on the specified conveying speed such that the print web between the first roller and the second roller is conveyed at the specified conveying speed and the digital printing head at the selected frequency and activated based on the printing data such that the digital printing head is advantageously actuated at a selected, fixed frequency, and such that complex dynamic actuation of the digital printing head and an associated measurement and control system are eliminated.

Claims

1. A method for operating a digital web printing press comprising an adjusting unit and an ascertaining unit, the method comprising: selecting, by the adjusting unit, a frequency for actuating a digital printing head at the frequency to output printing ink onto a print web; ascertaining, by the ascertaining unit, a specified conveying speed for conveying the print web based on the selected frequency and printing data; controlling a motor driving at least one of (i) a first roller and (ii) a motor driving a second roller based on the specified conveying speed such that the print web is conveyed at the specified conveying speed; and actuating the digital printing head at the selected frequency and based on the printing data.

2. The method as claimed in claim 1, further comprising: capturing a conveying parameter of at least one of (i) the first roller and (ii) the second roller; ascertaining a conveying speed of the print web based on the captured conveying parameter; and controlling at least one of (i) the first motor and (ii) the second motor based on the ascertained conveying speed to ensure the conveying speed corresponds to the specified conveying speed.

3. The method as claimed in claim 1, further comprising: capturing a print web parameter of the print web; and controlling at least one of (i) the first motor and (ii) the second motor based the captured print web parameter.

4. The method as claimed in claim 2, further comprising: capturing a print web parameter of the print web; and controlling at least one of (i) the first motor and (ii) the second motor based the captured print web parameter.

5. The method as claimed in claim 1, further comprising: periodically printing a register mark onto the print web via the digital printing head; capturing a distance between two successively printed register marks on the print web; and controlling at least one of (i) the first motor and (ii) the second motor based on the captured distance.

6. The method as claimed in one of claim 1, further comprising: generating image data based on a printed design printed onto the print web by the digital printing head; comparing the generated image data with the printing data; and controlling at least one of (i) the first motor and (ii) the second motor based on a result of the comparison.

7. The method as claimed in claim 1, further comprising: setting an output quantity of the printing ink for a printing nozzle of the digital printing head in one period of the selected frequency based on the printing data and the specified conveying speed.

8. The method as claimed in claim 1, wherein the print web between the first roller and the second roller is directly below the digital printing head.

9. A control apparatus for operating a digital web printing press, comprising: an adjusting unit for setting a selected frequency; an ascertaining unit for ascertaining a specified conveying speed of a print web based on the frequency and printing data; a controller for controlling at least one of (i) a first motor driving a first roller and (ii) a second motor driving a second roller to set a conveying speed (v) of the print web running between the first roller and the second roller based on the specified conveying speed; and an actuating unit for actuating a digital printing head to output printing ink at the frequency and based on the printing data.

10. The control apparatus as claimed in claim 9, further comprising: a first capture unit for capturing a conveying parameter of at least one of (i) the first roller and (ii) the second roller; wherein the ascertaining unit is configured to ascertain the conveying speed (v) based on the captured operating parameter and the controller is configured to control at least one of (i) the first motor and (ii) the second motor based on the ascertained conveying speed.

11. The control apparatus as claimed in claim 9, further comprising: a second capture unit for capturing a print web parameter of the print web; wherein the ascertaining unit is configured to ascertain the conveying speed based on the captured print web parameter and the controller is configured to control at least one of (i) the first motor and (ii) the second motor based on the ascertained conveying speed.

12. The control apparatus as claimed in claim 10, further comprising: a second capture unit for capturing a print web parameter of the print web; wherein the ascertaining unit is configured to ascertain the conveying speed based on the captured print web parameter and the controller is configured to control at least one of (i) the first motor and (ii) the second motor based on the ascertained conveying speed.

13. The control apparatus as claimed in claim 9, further comprising: a third capture unit for capturing sensor data from the printed print web; and a correction unit for ascertaining a correction value based on the printing data and the sensor data; wherein the ascertaining unit is configured to ascertain a corrected conveying speed based on the correction value and the controller is configured to control at least one of (i) the first motor driving the first roller and (ii) the second motor driving the second roller to set the corrected conveying speed.

14. The control apparatus as claimed in claim 10, further comprising: a third capture unit for capturing sensor data from the printed print web; and a correction unit for ascertaining a correction value based on the printing data and the sensor data; wherein the ascertaining unit is configured to ascertain a corrected conveying speed based on the correction value and the controller is configured to control at least one of (i) the first motor driving the first roller and (ii) the second motor driving the second roller to set the corrected conveying speed.

15. The control apparatus as claimed in claim 11, further comprising: a third capture unit for capturing sensor data from the printed print web; and a correction unit for ascertaining a correction value based on the printing data and the sensor data; wherein the ascertaining unit is configured to ascertain a corrected conveying speed based on the correction value and the controller is configured to control at least one of (i) the first motor driving the first roller and (ii) the second motor driving the second roller to set the corrected conveying speed.

16. A web printing press having a print web running between a driven first roller and a driven second roller, comprising: a digital printing head, arranged between the first roller and the second roller above the print web, for outputting printing ink onto the print web; and a control apparatus as operating the web printing press comprising: an adjusting unit for setting a selected frequency; an ascertaining unit for ascertaining a specified conveying speed of the print web based on the frequency and printing data; a controller for controlling at least one of (i) a first motor driving the first roller and (ii) a second motor driving the second roller to set a conveying speed of the print web running between the first roller and the second roller based on the specified conveying speed; and an actuating unit for actuating the digital printing head to output printing ink at the frequency and based on the printing data.

17. The web printing press as claimed in claim 16, further comprising: a device for capturing a conveying parameter of at least one of (i) the first roller and (ii) the second roller; wherein the control apparatus is configured to operate the printing press based on the captured conveying parameter.

18. The web printing press as claimed in claim 16, further comprising: a device for capturing a print web parameter of the print web; wherein the control apparatus is configured to operate the printing press based on the captured print web parameter.

19. The web printing press as claimed in claim 17, further comprising: a second device for capturing a print web parameter of the print web; wherein the control apparatus is configured to operate the printing press based on the captured print web parameter.

20. The web printing press as claimed in claim 16, further comprising: a sensor, arranged downstream of the digital printing head in the direction of conveyance of the print web, for capturing sensor data from the printed print web; wherein the control apparatus is configured to ascertain a correction value based on the captured sensor data and the printing data and is further configured to operate the web printing press based on the correction value.

21. The web printing press as claimed in claim 17, further comprising: a sensor, arranged downstream of the digital printing head in the direction of conveyance of the print web, for capturing sensor data from the printed print web; wherein the control apparatus is configured to ascertain a correction value based on the captured sensor data and the printing data and is further configured to operate the web printing press based on the correction value.

22. The web printing press as claimed in claim 18, further comprising: a sensor, arranged downstream of the digital printing head in the direction of conveyance of the print web, for capturing sensor data from the printed print web; wherein the control apparatus is configured to ascertain a correction value based on the captured sensor data and the printing data and is further configured to operate the web printing press based on the correction value.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention is explained in more detail below on the basis of preferred embodiments with reference to the accompanying figures, in which:

(2) FIG. 1 is an illustration of a schematic block diagram of an exemplary embodiment of a method for operating a digital web printing press;

(3) FIG. 2 is an illustration of a schematic block diagram of a first exemplary embodiment of a control apparatus in accordance with the invention;

(4) FIG. 3 is an illustration of a schematic block diagram of a second exemplary embodiment of a control apparatus in accordance with the invention; and

(5) FIG. 4 is a schematic illustration of an exemplary embodiment of a web printing press in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

(6) In the figures, elements that are the same or have the same function have been provided with the same reference signs, unless indicated otherwise.

(7) FIG. 1 shows a schematic block diagram of an exemplary embodiment of a method for operating a digital web printing press 200 (see FIG. 4). In a first step 10, a frequency F (see FIGS. 2 to 4) at which the digital printing head 210 (see FIG. 4) is actuated to output printing ink 212 (see FIG. 4) is selected. Here, selecting is understood to mean, for example, that an operator of the web printing press 200 inputs the frequency F using a suitable input means. Alternatively, the frequency F can be derived from specific constraints. Furthermore, there can be provision for the frequency F to be firmly prescribed by the printing head 210, for example, because the printing head can only be operated at a specific frequency F.

(8) In a second step 20, the selected frequency F is taken as a basis for ascertaining a specified conveying speed vs (see FIGS. 2 and 3) for the conveying speed v (see FIG. 4). The specified conveying speed vs can be ascertained, in particular calculated, from an association between the frequency F and a desired printing resolution, for example. The printing resolution is obtained from printing data D (see FIGS. 2 to 4).

(9) In a third step 30, the rollers 220, 230 (see FIG. 4) that convey a print web 240 (see FIG. 4) through a printing region 250 (see FIG. 4) are controlled such that the conveying speed v of the print web 240 corresponds to the specified conveying speed vs. This is accomplished in particular by virtue of a first motor M1 (see FIG. 4) that drives the first roller 220, and/or a second motor M2 that drives the second roller 220, being controlled accordingly.

(10) In a fourth step 40, the digital printing head 210 is actuated at the selected frequency F and with the printing data D.

(11) The inventive method can be employed in particular to operate a web printing press 200 whose printing head 210 is not actuated based on a captured conveying speed of the print web 240 at a variable frequency.

(12) FIG. 2 shows a schematic block diagram of a first exemplary embodiment of a control apparatus 100 that can operate a web printing press 200 via the above-described method. The control apparatus 100 comprises an adjusting unit 110 configured to set a selected frequency F. The adjusting unit 110 comprises in particular a clock generator. Furthermore, the adjusting unit 110 can have an input means or a receiving means for selecting the frequency F.

(13) The adjusting unit 110 outputs the selected and set frequency F to an ascertaining unit 120 and an actuating unit 140. The ascertaining unit 120 is configured to ascertain a specified conveying speed vs based on the frequency F and printing data D. The printing data D are in particular prescribed or input externally and comprise for example a printed design M to be printed (see FIG. 4) as machine-readable data. The actuating unit 140 is configured to read the printing data D and to actuate a digital printing head 210 (see FIG. 4) accordingly. Here, printing nozzles (not shown) of the digital printing head 210 are actuated to output printing ink 212 (see FIG. 4) at the frequency F. That is, in each period of the frequency F, a printing nozzle outputs a specific quantity or a specific volume of the printing ink 212. The printing ink 212 output in one period produces a picture element on the print web 240.

(14) The ascertaining unit 120 outputs the ascertained specified conveying speed vs to a controller 130. The controller 130 takes the specified conveying speed vs as a basis for controlling a first motor M1 (see FIG. 4) that drives the first roller 220 (see FIG. 4), and/or a second motor M2 (see FIG. 4) that drives a second roller 230 (see FIG. 4). This control sets the conveying speed v (see FIG. 4) of the print web 240 to the specified conveying speed vs. This ensures that the printed design M that has been printed is concordant with the printing data D.

(15) FIG. 3 shows a schematic block diagram of a second exemplary embodiment of a control apparatus 100 that can operate a web printing press 200 via the above-described method. This second exemplary embodiment has all the features of the first exemplary embodiment of FIG. 2. Furthermore, the control apparatus 100 in this case comprises three capture units 150, 160, 170 and a correction unit 172.

(16) The first capture unit 150 is configured to capture a conveying parameter P1, P2 of the first roller 200 (see FIG. 4) and/or of the second roller 230 (see FIG. 4). The first conveying parameter P1 comprises, for example, a conveying speed v1 (see FIG. 4) of the first roller 220 and the second conveying parameter P2 comprises, for example, a circumferential speed v2 (see FIG. 4) of the second roller 230. The ascertaining unit 120 is configured to ascertain the conveying speed v of the print web 240 based on the parameters P1, P2. The controller 130 is configured to control the conveying speed v based on the ascertained conveying speed v.

(17) The second capture unit 160 is configured to capture a print web parameter P3 that is, for example, a thickness of the print web 240. The ascertaining unit 120 is configured to ascertain the conveying speed v of the print web 240 based on the parameter P3. The controller 130 is configured to control the conveying speed v based on the ascertaining conveying speed v.

(18) The third capture unit 170 is configured to capture image data B of a printed design M (see FIG. 4) printed by the digital printing head 210 (see FIG. 4). The correction unit 172 takes the captured image data B and the printing data D as a basis for ascertaining a correction value K. The correction value K is used by the ascertaining unit 120 to ascertain a corrected conveying speed vk. By way of example, the corrected conveying speed vk is a sum of the specified conveying speed vs and the correction value K. The ascertaining unit 120 outputs the specified conveying speed vs or the corrected conveying speed vk to the controller 130, where the controller 130 then controls the conveying speed v of the print web 240 accordingly.

(19) FIG. 4 schematically shows an exemplary embodiment of a web printing press 200. The web printing press 200 comprises in particular a control apparatus 100 that is configured to operate the web printing press 200. The control apparatus 100 can correspond to one of the exemplary embodiments shown in FIG. 2 or FIG. 3, for example. The control apparatus 100 is configured to perform the method described on the basis of FIG. 1.

(20) The web printing press 200 comprises a digital printing head 210 that is arranged above a print web 240. The digital printing head 210 is configured to output printing ink 212 onto the print web 240 by means of printing nozzles (not shown). The region in which the printing head 210 can output printing ink 212 onto the print web 240 is referred to as the printing region 250.

(21) The printing region 250 is situated between a first roller 220 and a second roller 230 that convey the print web 240. The first roller 220 can also be referred to as the feed roller, and the second roller 230 can also be referred to as the discharge roller. Arranged between the rollers 220, 230 are four guide rollers 260, which serve to support and guide the print web 240 in the printing region 250. For reasons of clarity, only one guide roller 260 is denoted by a reference sign. The guide rollers 260 are not driven and are preferably mounted so as to be very smoothly rotatable, so that they rotate with the print web 240 without affecting it.

(22) The first roller 220 is driven by a first motor M1, and the second roller 230 is driven by a second motor M2. The motors M1, M2 are in particular electric motors and drive the rollers 220, 230 directly, i.e., there is no gearbox between the motor M1, M2 and the respective roller 220, 230. This allows particularly exact control of the conveying speed v of the print web 240 to be produced.

(23) The control apparatus 100 operates the web printing press 200. This is effected in accordance with the method described on the basis of FIG. 1. The control apparatus 100 operates the web printing press 200 based on printing data D and a selected frequency F. The frequency F determines the time intervals in which a printing nozzle of the printing head 210 can output printing ink 212. The control apparatus 100 takes the frequency F and the printing data D as a basis for ascertaining the specified conveying speed vs at which the print web 240 needs to be conveyed through the printing region 250, so that the printed design M that has been printed is concordant with the printing data D. For this purpose, the control apparatus 100 comprises in particular an ascertaining unit 120 (see FIG. 2 or 3). The control apparatus 100 additionally comprises a controller 130 (see FIG. 2 or 3) that controls the motors M1, M2 such that the print web 240 is conveyed at the specified conveying speed vs.

(24) In this exemplary embodiment, the printing press 200 furthermore comprises an optional sensor 270 which, in this instance, is formed as a charge-coupled device (CCD) camera. The CCD camera 270 is arranged downstream of the printing head 210 in the direction of conveyance. The CCD camera 270 captures the printed designs M printed by the printing head 210 and converts them into image data B. The image data B are output to the control apparatus 100, which monitors whether the image data B are concordant with the printing data D, i.e., whether the attained print result corresponds to the printing data D. If there is a discrepancy between the image data B and the printing data D, then a correction unit 172 (see FIG. 3) ascertains a correction value K, which the control apparatus 100 takes into consideration for operating the web printing press 200. In particular, the conveying speed v of the print web 240 is set to a corrected conveying speed vk. Moreover, an output quantity of printing ink 212 through a printing nozzle per actuation period can also be adapted, for example, if a color intensity of the printed design M that has been printed differs from the printing data D. In the case of multicolored prints, it is also possible for a color mix to be adapted.

(25) Although the present invention has been described on the basis of exemplary embodiments, it is modifiable in a wide variety of ways.

(26) Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described and the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.