Printing – Flexible-sheet-securing devices
Patent
1997-01-16
1998-09-22
Burr, Edgar S.
Printing
Flexible-sheet-securing devices
B41F 2712
Patent
active
058098895
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process and to a device for securing and tightening a packing on a cylinder of a rotary printing press.
DESCRIPTION OF THE PRIOR ART
A prior art device for securing and tightening a packing is known from EP 00 99 275 B1. A longitudinal and radial cut in a cylinder of a printing press is provided as a cylinder channel. It is possible to radially move a tightening strip in this cylinder channel by means of tightening screws. This tightening strip is provided with shoulders, offset from each other, for engagement with the print start and print end portions of the plate or packing. Edges of suspension strips, which are fastened on the respective ends of the packing, are held in place by means of these shoulders.
DE 37 07 066 C2 shows a tightening device for the interconnected fastening of a packing on a cylinder of a rotary printing press. The cylinder has a channel, extending axis-parallel in the cylinder surface, with a tightening strip, which can be moved radially inward during the tightening process. On its upper part, this tightening strip is provided on each of its two sides with a recess for receiving reinforced ends of the packing.
The disadvantage of these prior art devices is that it is not possible to compensate for the loosening of one end of the packing which arises because of flexing processes occurring during the first printing following the application of the packing. With these known prior art devices, it is only possible to tighten both ends of the plate or packing evenly, but an adjustment between the two ends is not possible because of large static friction forces between the packing and the cylinder. Thus it is either not possible to tighten the loose end portion of the packing in accordance with the requirements, or the fixed end is overstretched, i.e. destroyed. The reinforced ends can also be ripped off or torn.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a process and a device, which does not utilize a tightening spindle, for securing and tightening a packing on a cylinder of a rotary printing press, by means of which the one-sided loosening of the packing at the print end, which is caused by flexing processes in the course of printing, can be prevented.
This object is attained in accordance with the present invention by means of a process or a device for securing and tightening a packing on a cylinder of a rotary printing press. The surface of the cylinder is provided with a cylinder channel. A pair of suspension rails are provided at the ends of the cylinder packing and these suspension rails are securable in the axially extending cylinder channel. A tightening strip is situated in the cylinder channel. One suspension strip is held in a groove in the cylinder channel by a side surface of the tightening strip. The other suspension edge is movable radially in the cylinder channel by movement of the tightening strip, also in a radial direction in the cylinder channel. This allows one end of the packing to be tightened while the other end is held in place.
It is possible in an advantageous manner to retighten a packing of a cylinder at the print end portion of the packing. Packings on a cylinder of a rotary printing press which are applied and tightened for the first time are loosened by the flexing processes which typically occur in the course of printing. These flexing processes begin at the print start portion of the packing and flex the packing in the direction toward the print end portion of the packing, because of which loosening of the end portion of the packing located at the print end takes place. Experience has shown that therefore only the print end portion of the packing must be specially retightened, because an even tightening of the packing in accordance with the flexing process takes place because of this. A one-time retightening process is sufficient in most cases, but it is also possible to retighten several times.
The different lengths of lateral legs of the suspension str
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Burr Edgar S.
Grohusky Leslie
Koenig & Bauer--Albert Aktiengesellschaft
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