Printing – Printing members – Blanks and processes
Reexamination Certificate
1999-11-01
2001-06-19
Funk, Stephen R. (Department: 2854)
Printing
Printing members
Blanks and processes
C101S486000, C101SDIG029
Reexamination Certificate
active
06247404
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an improved method of making newspaper printing plates. More particularly, the present invention relates to a method of making newspaper printing plates which eliminates failure of exact image superimposition in color printing, through strict control of positional relation between the image formed on each plate in a set of four color printing plates and bent edge stoppers formed along two edges of the plate.
2. Description of the Prior Art
FIG. 8
shows an example of a prior art rotary press for newspaper printing, which works in this manner. Streams of paper
1
unwinding from paper rolls in paper feeders A, A, A are printed on both sides in monochromatic printer sections B, B, B and a color printer section Ba. Three streams of paper
1
, put one on another, are then sent in to a folder section C where they are cut and folded into one sheet of newspaper one after another and sent out through a delivery fan D or the like.
The color printer section Ba includes a common or center printing cylinder
2
and four blanket cylinders
3
and four color plate cylinders
4
. On the four color plate cylinders
4
are mounted printing plates
5
which have an identical image thereon and are for printing in four different colors, respectively—yellow, red, blue, and black (for glossing). Such prior art arrangements are disclosed, for example, in unexamined Japanese patent applications laid open under Nos. H08-267724 and H08-290543.
Most commonly, the printing plate
5
is mounted on the color plate cylinder
4
in the following manner. The forward and backward edges of the printing plate
5
are bent to form stoppers
5
a
,
5
b
, which are put in slits
4
a
,
4
a
provided on the plate cylinder
4
for holding the printing plate as shown in FIG.
9
. The printing plate is closely wound around the plate cylinder
4
and held that way.
The printing plate
5
is wound around the plate cylinder
4
and held in position. That is usually effected in this manner. An axial positioning hole
5
c
is provided in one or both of the bent edge stoppers
5
a
,
5
b
at specific points. Into the hole
5
c
is inserted a positioning protrusion
4
b
provided on the plate cylinder
4
so that the axial-directional position of the printing plate
5
is held at a predetermined place.
FIGS. 10
,
11
, and
12
show a typical prior art apparatus for forming bent edge stoppers
5
a
,
5
b
on printing plate
5
. The apparatus has a printing plate loading table
7
with an edge blade
6
, a plate presser
8
vertically movable in relation to the printing plate loading table
7
, a movable bending tool unit
9
including bending tools
9
a
,
9
b
and a vertically movable positioning pin unit
10
on each side—the front and rear sides of the printing plate loading table
7
.
After the printing plate
5
is placed on the printing plate loading table
7
, positioning pins
10
a
are inserted into positioning holes
5
d
provided at the forward and backward edges of the printing plate
5
—the positioning holes
5
d
place the printing plate
5
in position on the printing plate loading table
7
. The plate presser
8
is moved down to clamp the printing plate
5
as shown in FIG.
11
. Then, the positioning pins
10
a
are moved back downward and the bending tool
9
a
of movable bending tool unit
9
is turned by a drive unit (not shown). In that way, the forward and backward edges of the printing plate
5
are bent along the edge line of the edge blades
6
,
6
to form bent edge stoppers
5
a
,
5
b
as shown in FIG.
12
. This technique is disclosed in Japanese utility model application No. S53-159703.
The prior art bent edge stopper forming apparatus shown in
FIG. 10
can form bent edge stoppers in the printing plate
5
for monochromatic printing with great efficiency and has proved to be highly practical. But the color printing plates processed by the prior art apparatus have often failed in exact image superimposition, presenting a number of problems in practical application.
To prevent the failure in exact image superimposition in color printing, it is necessary to position a set of four printing plates—for yellow, red, blue, and black—on the four color plate cylinders so accurately that the four images overlap almost perfectly. That is, care has to be taken in forming the positioning holes
5
d
in the four printing plates
5
that place the printing plate
5
in position on the printing plate loading table
7
so that the positional relation between the image T on each printing plate and the positioning holes
5
d
may always be maintained uniformly.
That is also applicable to formation of bent edge stoppers
5
a
,
5
b
and the axial positioning hole
5
c
in the printing plate
5
. The positional relation between the image T on all four printing plates and the bent edge stoppers
5
a
,
5
b
and the axial positioning hole
5
c
must be maintained to be the same.
In the prior art of making a printing plate for newspaper printing, the positions of the positioning holes
5
d
for positioning the plate
5
on the table
7
are decided upon on the basis of the dimensions of the printing plate, center of the printing plate, or the like. Positioning holes
5
d
are formed at the positions thus decided upon. In other words, the prior art method of making a printing plate for newspaper printing neither checks nor controls the positional relation between the image T formed on the printing face of the printing plate
5
and the positioning holes
5
d.
Some adjustment is made in forming the image T on the printing face of the printing plate
5
so that the images T on the four printing plates may be placed at the same position. But it is visual adjustment that is used, which is inexact. No precision positioning is involved.
The result is that the four printing plates
5
that form a set of color printing plates tend to be slightly different from each other in regard to positional relation between the image T on the printing face and the positioning holes
5
d
to position the printing plate
5
on the printing plate loading table
7
, bent edge stoppers
5
a
,
5
b
, and axial positioning hole
5
c
. Then, it is impossible to prevent failure of exact superimposition of the color printing faces no matter how precisely the four color plates were adjusted in mutual positional relation on a color plate cylinder in a color printer section B.
SUMMARY OF THE INVENTION
The present invention addresses the above-described problem with the prior art method of making printing plates for newspaper printing, that is, failure in exact image superimposition in color printing. This occurs because, in the prior art, when the four color printing plates are mounted on the color plate cylinders, the image T is not placed in the exactly identical position however carefully the positional relation is adjusted on the plate cylinders. The problem is that no strict controls are exercised on the positional relationships between: (1) an image T drawn on a printing face of a printing plate
5
and positioning holes
5
d
formed at the forward and backward edges of the printing plate
5
to put plate
5
in position on a printing plate loading table
7
; (2) the image T and an axial positioning hole
5
c
to position the printing plate
5
on a plate cylinder
4
in the axial direction; and (3) the image T and bent edge stoppers
5
a
,
5
b
for mounting the printing plate
5
on the plate cylinder
4
. It is, therefore, an object of the present invention to provide a method of making color printing plates for newspaper printing which makes it possible to consistently and economically prevent color images from getting deviated.
An object of the present invention is to provide a method of making printing plates for newspaper printing which method comprises an exposure step
12
of directly drawing a desired image T on a plate material E (in claim
2
, from a plate feeding step
11
) by laser beam in accordance with image drawing signals from a computer, a
Funk Stephen R.
Griffin & Szipl, P.C.
Kabushiki Kaisha Kaneda Kikai Seisakusho
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