Method and device for operating a rotary screen-printing machine

Patent metadata

Field	Value
Publication number	US-10696041-B2
Application number	US-201716487499-A
Country	US
Kind code	B2
Filing date	Sep 22, 2017
Priority date	Feb 23, 2017
Publication date	Jun 30, 2020
Grant date	Jun 30, 2020

Abstract

A screen-printing unit in a printing machine comprises a screen cylinder which carries a screen-printing stencil and in which a squeegee is moved, from the inside, into contact with, and away from the screen-printing stencil. The screen cylinder is moved into contact with an impression cylinder, such that a printing position is formed, and is moved away therefrom, such that a gap is formed. The screen cylinder is moved away from the impression cylinder, in a first phase, when the squeegee is in a non-contacting position. In a second phase, at least one sheet of printing material is passed through the printing position when the squeegee continues to be in a non-contacting position and the screen cylinder is at least temporarily in a contacting position. For subsequent sheets of printing material, in a third phase, the screen-printing unit is operated with the squeegee one of permanently and cyclically, such as at least once for each sheet of printing material, in a contacting position.

First claim

The invention claimed is:

1. A method for operating a screen printing unit in a printing press comprising a screen cylinder, which carries a screen printing forme and in which a squeegee can be engaged, from the inside, against the screen printing forme and disengaged therefrom, and which screen cylinder can be thrown onto an impression cylinder, such that a print position is formed, and can be thrown off of said impression cylinder such that a gap is formed, wherein,
in a first phase, the screen cylinder is thrown off of the impression cylinder while the squeegee is in a disengaged position,
in a second phase, multiple printing substrate sheets are conveyed through the print position while the squeegee remains in a disengaged position, and the screen cylinder is at least temporarily thrown on,
and, in a third phase, for subsequent printing substrate sheets, an operation is carried out in which the squeegee is in an engaged position, one of perpetually and cyclically at least once for each printing substrate sheet.

2. The method according to claim 1 , characterized in that, in the second phase, multiple printing substrate sheets are conveyed through the print position, with the screen cylinder being thrown on at least temporarily for each sheet, while the squeegee remains in a disengaged position for the period of time required for this second phase.

3. The method according to claim 2 , characterized in that, in the second phase, two to nine, printing substrate sheets are conveyed through the print position with the screen cylinder thrown on at least temporarily for each sheet, while the squeegee remains in a disengaged position for the period of time required for this second phase.

4. The method according to claim 1 , characterized in that one of during and at least toward an end of the first phase, printing ink is located inside the screen cylinder, and one of the screen cylinder and the impression cylinder is in an idle state in the first phase, is accelerated to an operating speed in a startup phase between the first and the second phases, and is operated at this operating speed, at least for a time.

5. The method according to claim 1 , characterized in that the printing substrate sheets conveyed through the print position in the second phase, while the squeegee remains in a disengaged position, are separated from the good sheets as waste sheets, and one of are ejected and are collected separately, downstream of the screen printing unit.

6. The method according to claim 1 , characterized in that a fixed number of first printing substrate sheets, conveyed through the print position in the third phase, with the squeegee in an engaged position and the screen cylinder thrown on, are separated from good sheets as waste sheets, and one of are ejected and are collected separately, regardless of their quality.

7. The method according to claim 6 , characterized in that an operating speed, one of existing and reached in the second phase, is significantly lower than a target production speed and is one of at least one-third lower than the target production speed, and equal to a sheet feed rate through the print position of up to 4,000 sheets/hour.

8. The method according to claim 1 , characterized in that, during one of the second phase and the third phase, one of the screen cylinder and the impression cylinder is accelerated to a target production speed that is at least 1.5 times greater than one of a lower operating speed previously assumed and that is equal to a sheet feed rate through the print position of at least 6,000 sheets/hour.

9. The method according to claim 1 , characterized in that the operation comprising the first, second, and third phases is carried out as part of one of a commencement and a resumption of a production run.

10. The method according to claim 9 , characterized in that between the first and second phases, a sheet feeder begins feeding sheets into the printing press in synchronization with one of an angular position and an angular speed of the impression cylinder, and the second phase begins when the screen cylinder is thrown onto the first printing substrate sheet that is conveyed from the sheet feeder into the print position as part of one of a commencement and the resumption of a production run.

11. The method according to claim 9 , characterized in that the resumption of a production run is preceded by an error-induced interruption in the production run, and a machine stop, in which shutdown is controlled.

12. The method according to claim 11 , characterized in that the squeegee is moved to a disengaged position before the screen cylinder is thrown off.

13. The method according to claim 12 , characterized in that the screen cylinder is thrown off, after the screen cylinder has rolled, with at least a majority of its circumferential surface, along a printing substrate sheet that is conveyed through the print position while the squeegee is in a disengaged position.

14. The method according to claim 1 , characterized in that, during operation, in which the squeegee is engaged cyclically at least once per printing substrate sheet, one of an engagement and a disengagement of a squeegee against a screen printing forme is carried out in a repeating cycle comprising one of in a sequence of one or more phases relating to an engaged position and one or more phases relating to a disengaged position, and in that the squeegee is engaged and disengaged by a drive means that is mechanically independent of a rotary drive of one of the screen cylinder and the impression cylinder.

15. A device for operating a screen printing unit in a printing press, for use in a method according to claim 1 , comprising a screen cylinder, which carries a screen printing forme and in which a squeegee can be engaged from the inside against the screen printing forme and can be disengaged from said printing forme by a first drive means, and which screen cylinder can be thrown, by a second drive means, which is different from the first drive means, onto an impression cylinder such that a print position is formed and which screen cylinder can be thrown off of said impression cylinder, such that a gap is formed, wherein a control means is provided, which control means is connected, in terms of signals, to the first and second drive means, and, after a first phase, in which the screen cylinder is thrown off of the impression cylinder and the squeegee is in a disengaged position, in a second phase, in which the squeegee is perpetually in a disengaged position during the passage of multiple printing substrate sheets through the print position, said control means actuates the second drive means to throw the screen cylinder on, at least temporarily, for each printing substrate sheet and, in a subsequent third phase, for a number of printing substrate sheets, said control means actuates the first drive means to engage the squeegee from the inside against the screen printing forme, one of perpetually and at least once for each printing substrate sheet.

16. The device according to claim 15 , characterized in that one of the device and the control means is configured such that after a first phase, in which the screen cylinder is thrown off of the impression cylinder, and the squeegee is in a disengaged position, in a second phase, in which the squeegee is in a perpetually disengaged position, during the passage of one or more printing substrate sheets through the print position said control means throws said screen cylinder on at least temporarily for each printing substrate sheet, and in a subsequent third phase, said control means engages th

Assignees

• Koenig & Bauer Ag

Inventors

• Palme Martin
• Ruchti Vincent

Classifications

• B41F13/32

  Bearings mounted on swinging supports · CPC title

• B41F33/08

  for starting or stopping operation of cylinders · CPC title

• B41F33/06

  for starting or stopping operation of sheet or web feed · CPC title

• B41F15/423 Primary

  Driving means for reciprocating squeegees · CPC title

• B41F33/14

  Automatic control of tripping devices by feelers, photoelectric devices, pneumatic devices, or other detectors · CPC title