Printing – Rolling contact machines – Rotary
Reexamination Certificate
2002-01-18
2004-03-16
Hirshfeld, Andrew H. (Department: 2854)
Printing
Rolling contact machines
Rotary
C101S410000, C271S225000, C271S228000, C271S301000, C271S204000, C271S206000, C271S082000, C271S902000
Reexamination Certificate
active
06705221
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a device for turning or reversing flat copies in half-revolution sheet-processing machines, such as rotary printing machines.
The published German Patent Document DE 37 10 257 A1 is concerned with a sheet-fed rotary printing machine for performing single-sided multicolored printing or first form and perfecter printing, also known as recto/verso printing. A sheet transfer drum is accommodated between sheet-carrying cylinders of two printing units, which are disposed in a travel direction of sheet material; according to the proposal in this document, in order to achieve a construction which, in particular, operates independently of format, the transfer nip between the sheet transfer cylinder and the impression cylinder of the second printing unit is enlarged in comparison with the normal nip width to the impression cylinder of the first printing unit, and the clear interspace is bridged by a gripper system that is movable out of the circumference of the sheet transfer cylinder in order to grip the sheet leading or trailing edge.
The published German Patent Document DE 37 17 093 A1 is also concerned with a rotary printing machine for recto and recto/verso printing. Arranged between the impression cylinders of two printing units, in the travel direction of the sheet, is a sheet transfer cylinder, all of the cylinders having gripper systems assigned thereto. In order to achieve a construction with increased transfer reliability, even in the case of very thick printing material, a sheet feeder arranged downline from the sheet transfer cylinder is provided with a feeder top side configured at least approximately flat and extending somewhat tangentially to the sheet transfer cylinder. While the grippers of the sheet transfer cylinder holding the sheet trailing edge approach the feeder top side, the cylinder pushes the sheet onto the feeder top side with the free sheet leading edge in front, the sheet being lifted by the sheet transfer cylinder off the feeder top side by the trailing edge of the sheet.
The proposed embodiments outlined above are subject to the disadvantage that the sheet material necessarily rests with the respectively freshly printed side thereof on the outer surface of the transfer drum (storage drum) and is tensioned in order to achieve in-register turning or reversing. Damage to the printed image results from this unavoidable relative movement between the drum outer cylindrical surface or jacket and the sheet.
The published German Patent Document DE 196 15 730 A1 is concerned with a turning or reversing device for a printing machine, in particular to a sheet-fed rotary offset printing machine. The turning or reversing device for a printing machine comprises a transfer drum arranged between a first impression cylinder and a second impression cylinder. Below the transfer drum is a register cylinder having a large number of suction openings for holding the sheet by suction; after the gripper device has opened, the register cylinder conveys the sheet in-register into a temporary storage system. In the latter, the sheet is stored temporarily, in an approximately stretched-out form, on a first sheet guide device provided with blower or blast nozzles. A tongs-type turning or reversing gripping device arranged on the transfer drum grips the trailing edge of the sheet deposited in the temporary storage system, and transfers the edge to a conventional gripper device formed on the downline impression cylinder, which then supplies the sheet turned or reversed in this manner to a downline printing nip in order to print the underside of the sheet.
A disadvantage of this method is that operations are not performed with simultaneous gripper closure on the leading and trailing edge of the sheet.
In addition to the possible embodiments outlined from the prior art, the sheet material can also be stored on the impression cylinder. Following printing, the sheet material is stored on the impression cylinder, subsequently gripped by the gripper systems of the transfer drum, and turned or reversed. With regard to the half-revolution machine concept, i.e., constructing the cylinder with twice the circumference of that of the impression cylinder, the printing operation is completed, i.e., the sheets are printed out until, in recto printing mode, the leading edge thereof is transferred to the following transfer drum. For this reason, it is necessary to provide a complete sheet length between the printing point and transfer center line. Should it be possible for the sheet material to be turned or reversed, a further sheet-length space must be provided under the impression cylinder in order to store the sheet.
Reserving a further sheet-length space underneath the impression cylinder necessarily results in a specific relative arrangement of transfer cylinders, i.e., blanket cylinder, impression cylinder and transfer drum, relative to one another. If the necessary installation space upline from the printing point is to remain for the sheet guiding elements necessary to ensure the print quality, a large cylinder diameter is required in relation to the maximum Printing-material length. This entails higher production and manufacturing costs, greater dynamic problems due to the higher masses to be moved and, overall, an increase in the length of printing machines which, in print shops, occupy adjusting or installation area which is tight in any case.
A common factor in all of the heretofore proposed constructions is that they require a different configuration of the transfer drum in the turning or reversing printing unit compared with the configuration of the transfer drum in the other printing units. This results in considerable problems in the recto printing mode, wherein a multicolor rotary printing machine is also intended to be operated, in particular when processing a relatively stiff printing material such as pasteboard or cardboard.
SUMMARY OF THE INVENTION
Starting from the prior art outlined hereinabove, it is an object of the invention to provide a device for reversing flat copies in half-revolution sheet-processing machines, the device utilizing simultaneous gripper closure of the sheet material at the leading and trailing edge of the respective sheets, and operating with the greatest accuracy.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, in a sheet-processing rotary printing machine operatable in recto printing and recto/verso printing modes, a device for reversing sheets, comprising a transfer drum bounded by two sheet-guiding cylinders, a reversing/storage drum and an additional transport element assigned to the transfer drum, the transfer drum being drivable in opposite directions of rotation in the recto printing and the recto/verso printing modes, and gripper systems actable in both directions of rotation of the transfer drum, the gripper systems being in accommodated on an imaginary jacket surface of the transfer drum.
In accordance with another feature of the invention, the reversing/storage drum and the additional transport element, in the recto printing mode, are located outside a transport path of a sheet on the sheet-guiding cylinders.
In accordance with a further feature of the invention, a transport path of a sheet, in the recto/verso printing mode, is located on a side of a jacket surface of the transfer drum, which is located opposite the transport path of the sheet in the recto printing mode.
In accordance with an added feature of the invention, the transfer drum has a contour set back with respect to an enveloping curve of the gripper systems.
In accordance with an additional feature of the invention, the reversing/storage drum and the additional transport element are driven only in the recto/verso printing mode, and are stopped in the recto printing mode.
In accordance with yet another feature of the invention, the sheet-reversing device includes a first one of the sheet-guiding cylinders, the transfer drum drivable in a direc
Evans Andrea H.
Heidelberger Druckmaschinen AG
Hirshfeld Andrew H.
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