Printing – Multicolor – Rotary machines
Patent
1998-01-20
1999-06-08
Fisher, J. Reed
Printing
Multicolor
Rotary machines
101232, B41F 714
Patent
active
059097086
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a sheet-fed offset rotary printing press.
DESCRIPTION OF THE PRIOR ART
A three-cylinder rotary rubber-blanket printing press is known from DE-PS 435 592, wherein the plate cylinder and the rubber blanket cylinder each have at least two print areas, and an impression cylinder has one more print area than the rubber blanket cylinder.
It is a limitation of this prior printing press that registration problems can occur. A sheet to be printed is already removed from the impression cylinder by a gripper system before this sheet has been completely printed.
SUMMARY OF THE INVENTION
It is the object of the present invention to create a sheet-fed offset rotary printing press. By use of this press it is possible to imprint sheets of a sheet length matched to a single nominal diameter as well as a sheet length matched to twice the nominal diameter.
In accordance with the invention, this object is attained by means of a sheet-fed offset rotary printing press having the provision of a printing cylinder, a rubber blanket cylinder and a first, central impression cylinder that is provided with a plurality of controllable gripper systems. The number of gripper systems on the impression cylinder is not equal to the number of print areas on the printing cylinder. A second impression cylinder, that is provided with at least one controllable gripper system, is also assigned to the rubber blanket cylinder. Either the first or the second impression cylinder is arranged to selectively act together with the rubber blanket cylinder.
The sheet-fed offset rotary printing press in accordance with the present invention can be operated in an advantageous manner in two modes of operation: in the first mode of operation, sheets in a single length format can be printed in four colors. Sheets in a double length format can be printed in two colors by means of a second impression cylinder in the second mode of operation.
It is advantageous that by means of the sheet-fed offset rotary printing press in accordance with the present invention, a four-color printing process with a register of the highest accuracy can be achieved, since during all printing steps the sheets to be printed are maintained in a single gripper system on an impression cylinder. Only after each sheet has been completely printed, are the printed sheets taken over by a second gripper system and removed from the impression cylinder.
By the utilization of a sheet-feeding device synchronized with the impression cylinder, and which accelerates the sheets to be fed in from a state of rest to the circumferential speed of the impression cylinder, assured sheet-feeding with very accurate contact registration is achieved. This is achieved even at high speeds for example at speeds of 6,000 sheets per hour.
It is of particular advantage that a laser inscribing system is assigned to the printing cylinder and that therefore plates which can be laser-inscribed are inscribed directly in the printing press in a so-called computer-to-press process. Therefore, no registration difficulties occur, as have previously been caused by the mounting of the plates on the printing cylinder or because of errors during the production of the plates. It is therefore possible to omit circumferential, lateral or transverse registration adjustment devices.
The short inking units without inking zones minimize the set-up times and simplify the operation of the printing press. In particular, the short inking units make possible a very small structural size of the entire printing press. The short inking units are each only in contact with one print area of the printing cylinder, so that in the pulled-back state multiple rolling only takes place against a screen roller. By means of different diameters of the application roller and of the screen roller, an existing color relief is reduced in the circumferential direction. The screen roller cooperates with a chamber doctor blade, which completely removes remnants of the ink relief and generates a complet
REFERENCES:
patent: 4479431 (1984-10-01), Germann
patent: 4815376 (1989-03-01), Sarda
patent: 4854232 (1989-08-01), Oda
patent: 5036763 (1991-08-01), Germann
patent: 5469787 (1995-11-01), Turner et al.
patent: 5479856 (1996-01-01), Wirz
Fisher J. Reed
Koenig & Bauer--Albert Aktiengesellschaft
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