METHOD FOR CONTROLLING A PRINTING MACHINE AND STOPPING A TRANSPORT DEVICE THEREOF

Abstract

A method for controlling a printing machine including a revolving transport device for transporting a substrate, includes continuously scanning the surface of the transport device using a detection device, evaluating measured results to find defects on the surface, saving the defects in a data memory and outputting information on the defects. The method advantageously provides an operator with targeted information on defect type, defect location and defect frequency and thus allows a targeted elimination of defects, which may increase the overall productivity of the printing machine.

Claims

1. A method for controlling a printing machine including a revolving transport device for transporting a substrate to be printed on or already having been printed on, the method comprising the following steps: a) using a detection device for continuously scanning a surface of the transport device; b) evaluating measured results from the detection device to find defects on the surface of the transport device; c) using a data memory to save the defects and to additionally evaluate repeated defects; and d) outputting information about the defects.

2. The method for controlling a printing machine according to claim 1, which further comprises carrying out step d) by at least one of displaying information on a display or switching on a warning light or outputting an acoustic signal.

3. The method for controlling a printing machine according to claim 1, which further comprises carrying out an additional step e) of stopping the transport device if a repeated defect occurs.

4. The method for controlling a printing machine according to claim 3, which further comprises carrying out the additional step e) as a further step e') of stopping the transport device at a machine angle permitting a defect location of the defect to be visible and accessible to a machine operator.

5. The method for controlling a printing machine according to claim 4, which further comprises setting the machine angle in a region of an access opening of the printing machine.

6. The method for controlling a printing machine according to claim 4, which further comprises carrying out an additional step f) of marking the location of the defect by using spot illumination.

7. The method for controlling a printing machine according to claim 1, which further comprises carrying out step a) of scanning the surface of the transport device by scanning support surfaces of the transport device and scanning the substrate resting on the support surfaces.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0025] FIG. 1 is a diagrammatic, longitudinal-sectional view of a digital printing machine having a sensor system;

[0026] FIG. 2 is a more detailed longitudinal-sectional view of the digital printing machine of FIG. 1; and

[0027] FIG. 3 is a view similar to FIG. 2 of an alternative to the embodiment of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

[0028] Referring now in detail to the figures of the drawings, in which elements and components that correspond to one another have the same reference symbol and which are not drawn to scale, and first, particularly, to FIG. 1 thereof, there is seen a sheet-fed printing machine 100 constructed as a digital printing machine. A respective sheet 1000 coming from a feeder 1 is transported through a printing unit 2 to a delivery 3 in a direction of transport T. The respective sheet 1000 is transported mostly on cylinders, namely transfer cylinders 5 and a printing cylinder 10. Inkjet heads 4 disposed at a distance a above the printing cylinder 10 print on a sheet 1000 that is transported past at a short distance by the printing cylinder 10. Thus, the printing cylinder 10 is also referred to as a jetting cylinder or a transport device.

[0029] In the illustrated embodiment, the printing cylinder 10 has three sheet-holding regions or sheet-supporting surfaces 11 separated from one another by respective gaps 12. The sheets 1000 are held on the sheet-holding regions 11 by grippers 13.

[0030] A machine control unit 15, including a user interface and a memory, is provided to control the printing machine 100. A sensor system 14 for continuously monitoring the sheets 1000, the surface of the jetting cylinder 10 and the grippers 13 of the jetting cylinder 10, is disposed upstream of the inkjet heads 4 as viewed in the direction of transport T. For this purpose, the sensor system 14 is disposed in the path of sheet travel. The sensor system 14 may in particular monitor the traveling of the sheets, i.e. a printing material thickness d indicating how far the sheets 1000 protrude above the sheet-holding regions 11. In this way, creases, dog-ears, folds, waves, and sheets 1000 that are held insufficiently or badly may be detected. Surface contamination of the jetting cylinder 10 or defective or bent grippers 13 may likewise be detected. A data transmission connection is provided between the sensor system 14 and the machine control unit 15, which also includes sensor control.

[0031] The sensor system 14 is to be disposed sufficiently far upstream of the inkjet heads 4 to ensure that a collision between sheets 1000 and inkjet heads 4 may be avoided, for instance by stopping the machine 100, lifting the inkjet heads 4, or diverting the defective sheet 1000 (not illustrated), even if a defect occurs at the trailing sheet edge of a sheet 1000.

[0032] A removal drum 25 for removing defective sheets, e.g. sheets 1000 with an incomplete print, is disposed downstream of the jetting cylinder 10.

[0033] FIG. 2 illustrates a section of the printing machine 100 shown in FIG. 1. The housing of the printing machine 100 includes an access opening 19, which is for instance constructed as a flap that may be opened and closed. While in an ergonomically favorable position, a machine operator 200 has a field of vision 210 that extends through the access opening 19 and as far as the printing cylinder 10.

[0034] A detection device 14, which may include sensors or cameras, continuously monitors the surface of the printing cylinder 10. A machine control unit 15 evaluates measured results. If defects are detected, they are saved in a data memory connected to the machine control unit 15. The machine control unit 15 examines the defects saved in the data memory to find repetitive defects, also referred to as systematic defects, by evaluating defect type, defect location, and defect frequency. If a defect 1001 or a repetitive defect has been detected, the relevant information is output to the machine operator 200 on a screen or display of the machine control unit 15. In addition, the printing cylinder 10 may be stopped in the following angle-controlled way: since the defect location is documented in the machine control unit 15, a drive motor 18 of the printing cylinder 10 may be actuated in such a way that the printing cylinder 10 is stopped at a machine angle , positioning a defect 1001 precisely in the field of vision 210 of the machine operator 200 and consequently in the region in which the machine operator 200 may intervene through the access opening. For this purpose, there is a data transmission connection between the drive motor 18 and the machine control unit 15. Based on the defect information indicated on the display of the control unit 15, the machine operator 200 may effect a quick and simple elimination of the defect 1001.

[0035] As shown in FIG. 3, the printing machine 100 may additionally be equipped with a loudspeaker or a signal horn 17 as well as a warning light 16 to alert the machine operator 200 to a defect 1001 and the need for intervention. A data transmission connection is provided between these components and the machine control unit 15.

[0036] In order to be able to accurately indicate the defect location of the defect 1001 to the machine operator 200, an illumination device 20 that is actuated by the machine control unit to accurately illuminate the defect location may be provided in the printing machine 100. The illumination device 20 may be used to mark the location of the defect 1001 by using spot illumination.