Printing – Embossing or penetrating – Processes
Reexamination Certificate
2000-04-28
2001-09-04
Eickholt, Eugene (Department: 2854)
Printing
Embossing or penetrating
Processes
C101S485000, C101S401100, C409S108000, C409S109000, C358S296000, 36
Reexamination Certificate
active
06283019
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is in the field of electronic reproduction technology and is directed to a method for engraving printing cylinders for rotogravure, whereby at least two engraving lanes of predetermined lane widths lying next to one another in axial direction are engraved with a respectively allocated engraving element, and is also directed to an electronic engraving machine for the implementation of the method.
When engraving printing cylinders in an electronic engraving machine, the engraving element that, for example, comprises an engraving stylus as a cutting tool, moves axially along a rotating printing cylinder continuously or in steps. The engraving stylus controlled by an engraving control signal cuts a sequence of depressions, referred to below as cups, arranged in an engraving raster into the generated surface of the printing cylinder. The engraving control signal is formed from the superimposition of an engraving signal representing the tonal values between “black” and “white” with a periodic raster signal. Whereas the periodic raster signal effects a vibrating lifting motion of the engraving stylus, the engraving signal controls the depths of the cups engraved into the generated surface of the printing cylinder in conformity with the tonal values to be reproduced.
For magazine printing, a plurality of strip-shaped cylinder regions, called engraving lanes, that lie axially next to one another must be simultaneously engraved with a respective engraving element on a printing cylinder or, respectively, on the printing cylinders of a color set that are successively engraved in one engraving machine or, on the other hand, are engraved simultaneously in a plurality of engraving machines. For example, the various printed pages of a print job are engraved in the individual engraving lanes. The engraving elements allocated to the individual engraving lanes are mounted on a common engraving carriage that moves along the printing cylinder in an axial direction during engraving.
A prerequisite for a good reproduction quality is the registration-exact adherence to the lane widths of the individual engraving lanes in the axial direction of the printing cylinder. In order to achieve a registration-exact engraving of the engraving lanes, the distances between the engraving stylus tips of the individual engraving elements in the axial direction of the printing cylinder due to axial displacement of the engraving elements on the engraving carriage must be set with high precision to the required lane widths according to the traditional method, and the engraving carriage with the exactly spaced engraving elements must then be displaced relative to the printing cylinder such that the engraving stylus tips are positioned to the respective, axial engraving start position of the engraving lanes. It is thereby not so much a matter of the absolute setting of the lane widths within an allowable range of tolerances but that all lane widths on a printing cylinder exactly coincide within the range of tolerance.
The traditional alignment of the engraving stylus tips of the engraving elements to the lane widths to be engraved occurs essentially manually by an operator in that the operator initially roughly sets the spacings of the engraving elements corresponding to the lane widths and then finely positions the engraving stylus tips of the engraving elements with visual observation of the engraving stylus tips with the assistance of a specific microscope unit (stylus allocation gauge) and manually actuatable spindle drives.
This manual procedure is time-consuming, particularly when a great number of engraving lanes are to be positioned and, thus, a great plurality of engraving elements must be positioned. Moreover, the adjustment precision is essentially dependent on the care of the operator.
WO Published Application 95/21332 already discloses an apparatus for automatic, axial positioning of a plurality of engraving elements when engraving printing cylinders with the assistance of motor drives for the individual engraving elements arranged on an engraving carriage and a sensor monitoring for the automatic motion sequences.
SUMMARY OF THE INVENTION
An object of the present invention is to improve a method for engraving printing cylinders for rotogravure, whereby at least two engraving lanes with predetermined lane widths lying side-by-side in the axial direction are engraved with a respectively allocated engraving element, to improve an electronic engraving machine for implementation of the method, as well as to improve a position measuring unit such that exact, manual or automatic settings of the axial spacings of the engraving elements relative to one another are no longer required in order to achieve a good engraving quality.
According to the method of the invention for engraving printing cylinders for a rotogravure and an electronic engraving machine, at least two engraving lanes with predetermined lane widths are provided lying next to one another in an axial direction of the printing cylinder. The engraving elements respectively engrave a sequence of cups arranged in an engraving raster into the rotating printing cylinder. Engraving control signals for drive of the engraving elements are formed by superimposition of engraving signals that represent tonal values to be engraved with a periodic raster signal for generating a raster. For engraving the cups, the engraving elements execute a feed motion along the printed cylinder in the axial direction of the printing cylinder. Before engraving, axial spacings of the engraving elements are set relative to one another. An axial reference position is predetermined for each engraving element, axial spacings of the reference positions relative to one another corresponding to the predetermined lane widths of the engraving lanes. The engraving elements are roughly positioned to their reference positions. Axial spacing errors between the reference positions and actual positions of the engraving elements based on the rough positioning are measured. During engraving, the engraving elements execute a feed motion along the printing cylinder with faulty spacings relative to one another caused by the rough positioning. The axial spacing errors are compensated by a shifted engraving of the engraving lanes on the printing cylinder such that the engraving lanes exhibit the predetermined lane widths despite the faulty spacings of the engraving elements relative to one another.
The invention is explained in greater detail below with reference to FIGS.
1
through
4
.
REFERENCES:
patent: 4174527 (1979-11-01), Schaefer
patent: 4259697 (1981-03-01), Doelves
patent: 4729037 (1988-03-01), Doelves
patent: 5492057 (1996-02-01), Bornhors, Jr. et al.
patent: 5532731 (1996-07-01), Mihara et al.
patent: 5663802 (1997-09-01), Beckett et al.
patent: 5808748 (1998-09-01), Brewer et al.
patent: 5828464 (1998-10-01), Yoshida et al.
patent: 5831746 (1998-11-01), Seltz et al.
patent: 5894354 (1999-04-01), Beckett et al.
patent: 5947020 (1999-09-01), Bornhorst, Jr. et al.
patent: 6007230 (1999-12-01), Beckett et al.
patent: 6025921 (2000-02-01), Beckett et al.
patent: 0 762 723 (1997-03-01), None
patent: WO 95/08443 (1995-03-01), None
Eickholt Eugene
Heidelberger Druckmaschinen AG
Schiff & Hardin & Waite
LandOfFree
Method for engraving printing cylinders does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for engraving printing cylinders, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for engraving printing cylinders will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2526823