Printing – Intaglio – Rotary
Reexamination Certificate
2002-03-29
2004-05-25
Colilla, Daniel J. (Department: 2854)
Printing
Intaglio
Rotary
C101S156000, C101S155000, C101S168000, C101S169000
Reexamination Certificate
active
06739247
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention refers to a printing device for rotogravure printing machines, and in particular to a printing device comprising an improved doctor member.
2. Background Information
The current rotogravure printing machines are equipped, as can be seen in
FIG. 1
, with a printing device
1
that substantially comprises at least one printing cylinder
3
equipped on its external surface with a plurality of notches
5
adapted to contain printing liquid (usually ink), and at least one scraper member
7
for every printing cylinder
3
. This scraper member
7
is of a type commonly known as doctor and is thrust in contact with the surface of the printing cylinder
3
in order to remove the ink that can be found on the cylinder
3
surface outside of the notches
5
, in order to clean the cylinder
3
itself. Ink is “fished” from a tank (not shown) placed under the cylinder
3
and wets the cylinder
3
surface when this latter one performs a rotation printing pass.
Printing on paper supports
2
(usually continuous webs of paper of various types) is carried out through the pressure of a rubber roller
4
that thrusts the paper itself against the printing cylinder
3
. This pressure, that is usually applied vertically towards the ground, for 3680-mm wide paper webs (that are the typical paper webs that are commonly used) can reach values that are equal to 15 kg/cm and therefore the rubber roller
4
applies to the printing cylinder
3
a force that is equal to about 6000 kg. Since the printing cylinder
3
is connected to two fixed ends
11
,
13
in order to rotate around its longitudinal axis, this force tends to thrust the cylinder
3
downwards (towards the ground) progressively distorting through flexure the cylinder
3
surface up to a value that, next to the central part of the cylinder
3
itself, gets to 1 mm of downwards flexure (starting from a 0-mm flexure value next to the fixed ends
11
,
13
).
When working, therefore, the printing cylinder
3
, the paper web
2
and the rubber roller
4
assume an arc-shaped configuration due to the downwards flexure of all three components, with a flexure difference that progressively goes from 0 to 1 mm along the whole extension of the cylinder
3
. Obviously, for different types of workings, different flexure extensions can and could be provided, that anyway all imply the same problem that follows.
The doctor-type scraper member
7
is composed of an elongated blade
16
, commonly 0.15-mm thick, that is pressed in contact with the cylinder
3
surface in order to allow it to scrape ink away. Due to the simultaneous presence of a high working speed, of the contact pressure between scraper member
7
and cylinder
3
, for the thrust of all ink to be moved and above all for the above flexure to which the cylinder
3
is subjected, the scraper member
7
works differently along the cylinder
3
extension: in fact, ink is completely removed next to the ends
11
,
13
and always more poorly removed when going away from the ends
11
,
13
, since the cylinder
3
surface is also moving away by flexure from the blade
16
of the scraper member
7
. This different ink-scraping capability is further translated into a different wear of the scraper member
7
, since a smooth contact between itself and the cylinder
3
is progressively missing.
SUMMARY OF THE INVENTION
Object of the present invention is solving the above prior-art problems, by providing a printing device
1
in which the scraper member
7
follows with a maximum accuracy the progressive flexure of the printing cylinder
3
, in order to guarantee a smooth ink scraping in all its points.
A further object of the present invention is providing a printing device
1
of the above-mentioned type that can be realised with a minimum number of pieces, at a reduced cost and without increasing the final encumbrances of the rotogravure machine to which it is applied.
A further object of the present invention is providing a printing device
1
and a related process for which the force applied to the scraper member
7
in order to allow it to follow the flexure of the printing cylinder
3
can be automatically determined according to the diameter of cylinder
3
and roller
4
, and according to other working parameters, also automatically determined.
The above and other objects and advantages of the invention, as will appear from the following description, are obtained by a printing device and a process as claimed in claims
1
and
6
. Preferred embodiments and non-trivial variations of the present invention are claimed in the dependent claims.
REFERENCES:
patent: 5437227 (1995-08-01), Straubinger
patent: 5636566 (1997-06-01), Kipp
patent: 3201178 (1983-07-01), None
patent: 57070666 (1982-05-01), None
patent: 10278221 (1998-10-01), None
patent: 2003260393 (2003-09-01), None
patent: WO 9814329 (1998-04-01), None
Machine translation of JP 10278221 A to Ishimoto from Japanese Patent Office website.
Carmichael James T.
Colilla Daniel J.
Miles & Stockbridge P.C.
Officine Meccaniche Giovanni Cerutti S.p.A.
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