Printing – Cleaning attachments
Reexamination Certificate
1999-02-23
2003-06-03
Eickholt, Eugene H. (Department: 2854)
Printing
Cleaning attachments
C101S211000, C101S229000
Reexamination Certificate
active
06571706
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for two-sided printing of a sheet of printing material having a front side and a rear side, in a sheet-fed rotary printing press, in which the front side is cleaned before being printed, and to a sheet-fed rotary printing press for two-sided printing of a sheet of printing material having a front side and a rear side and, in particular, for performing the method, the printing press having at least one printing unit for printing the front side and at least one other printing unit for printing the rear side, and having a first cleaning device for cleaning the front side before it is printed.
In German Patent 18 39 446, a rotary dust removal machine for paper sheets is described, in which both sides of the paper sheets are completely cleaned by roller brushes. This machine can be combined with other rotary processes or can be provided as an accessory to existing machines.
In the published German Patent Document DE 4 435 307 A1, a method and a device are described which ensure the realization, in sheet-fed offset printing presses, of other operations in addition to printing in a single sheet pass. Due to the provision of a printing blanket on the form cylinder, or due to the surface of the impression cylinder, the amount of dust in the printing material fed to the printing units is reduced.
The hereinaforementioned prior art does not relate to printing on both sides of a sheet of printing material, nor does it provide any solutions for avoiding problems which arise in such a process.
In the published German Patent Document DE 4 036 253 C1, a sheet-fed rotary offset printing press of in-line construction for smear-free printing of cardboard and paper in multicolor two-sided or recto/verso printing is described that includes an upending or tumbling device. One advantageous possible use of the upending device occurs in printing cardboard sheets, the top surface of which to be printed must be subjected to a cleaning treatment and thereafter, before recto printing on that cleaned top surface, the sheet is reversed by the upending device and verso printing is performed on the bottom surface thereof, after which, another reversal of the sheet takes place, with smear-free recto printing being performed on the previously treated top side of the sheet.
In the journal Offset-Praxis [Offset Industry] October 1997, beginning on p. 74, a contact-free dust removal system for printing material in sheet-fed and web-fed printing presses for offset, rotogravure and flexographic printing is described which, in sheet-fed offset machines, for example, is mounted in the first printing unit, whereas, in recto/verso or first-form and perfector printing presses, it is disposed in the first impression cylinder after the sheet reversal.
The devices described in the two last-mentioned references serve to provide one-sided cleaning of the sheet of printing material, but do not contribute to overcoming the problems occurring in two-sided printing.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for two-sided printing of a sheet of printing material, and a sheet-fed rotary printing press for performing the method, by which the printing quality is increased, and contamination of the printing press is reduced.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for two-sided printing of a sheet of printing material having a front side and a rear side, in a sheet-fed rotary printing press, wherein the front side is cleaned before being printed, which comprises also cleaning the rear side of the sheet before printing thereon.
In accordance with another feature, the method of the invention includes printing in multiple colors on at least one of the front and the rear sides of the sheet.
In accordance with a further feature, the method of the invention includes printing in multiple colors on both the front and the rear sides of the sheet.
In accordance with an added feature, the method of the invention includes cleaning both the front and the rear sides of the sheet, and printing on both the front and the rear sides of the sheet within a single pass of the sheet of printing material through the sheet-fed rotary printing press.
In accordance with an additional feature, the method of the invention includes initially cleaning the front side of the sheet with a first cleaning device, and thereafter cleaning the rear side of the sheet with a second cleaning device disposed downline of the first cleaning device, as viewed in a sheet transport direction.
In accordance with yet another feature, the method of the invention includes performing in the following order the steps of cleaning the front side of the sheet, printing on the front side of the sheet, cleaning the rear side of the sheet, and printing on the rear side of the sheet.
In accordance with yet a further feature, the printing on the front and the rear sides of the sheet is multicolor printing.
In accordance with yet an added mode, the method of the invention includes performing the steps in a sheet-fed rotary printing press embodied as a recto/verso printing press.
In accordance with yet an additional feature, the method of the invention includes performing a contact-free cleaning method for cleaning at least one of the front and the rear sides of the sheet.
In accordance with still another feature, the method of the invention includes performing a cleaning method acting by contact for cleaning at least one of the front and the rear sides of the sheet.
In accordance with still a further feature, the method of the invention includes both a contact-free cleaning method and a cleaning method acting by contact for cleaning at least one of the front and the rear sides of the sheet.
In accordance with still an added feature, the method of the invention includes cleaning the front side of the sheet by at least one method like an at least one method for cleaning the rear side of the sheet.
In accordance with another aspect of the invention, there is provided a sheet-fed rotary printing press for two-sided printing of a sheet of printing material having a front side and a rear side, comprising at least a first printing unit for printing the front side and at least a second printing unit for printing the rear side of the sheet, a first cleaning device for cleaning the front side of the sheet before it is printed, and a second cleaning device for cleaning the rear side of the sheet before it is printed.
In accordance with another feature of the invention, the second cleaning device is disposed downline of the first cleaning device, as viewed in a sheet transport direction.
In accordance with a further feature of the invention, the sheet-fed rotary printing press includes a reversing device disposed between the first printing unit and the second printing unit, as viewed in a sheet transport direction.
In accordance with an added feature of the invention, the sheet-fed rotary printing press includes a plurality of printing units, particularly at least four printing units, preceding the reversing device, as viewed in the sheet transport direction.
In accordance with an additional feature of the invention, the sheet-fed rotary printing press includes a plurality of printing units, particularly at least four printing units, following the reversing device, as viewed in the sheet transport direction.
In accordance with yet another feature of the invention, the first cleaning device is assigned to an impression cylinder of the first printing unit.
In accordance with yet a further feature of the invention, the second cleaning device is assigned to an impression cylinder of the second printing unit.
In accordance with yet an added feature of the invention, the sheet-fed rotary printing press includes a sheet transfer device having at least one sheet transport drum disposed between two of the printing units preceding the reversing device, and the second cleaning device being assign
Conzelmann Daniel
Seefried Karl-Heinz
Stephan Günter
Eickholt Eugene H.
Greenberg Laurence A.
Mayback Gregory L.
Stemer Werner H.
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