Printing – Rolling contact machines – Rotary
Reexamination Certificate
2001-03-30
2003-01-14
Evanisko, Leslie J. (Department: 2854)
Printing
Rolling contact machines
Rotary
C101S376000, C101S415100, C101S221000, C428S909000, C492S056000
Reexamination Certificate
active
06505555
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
1. Field of the Invention
The present invention relates to a printing press such as a multi-color press. In particular, the present invention relates to a construction of a blanket cylinder disposed in each printing unit of the printing press and, more particularly, to a cylindrical blanket that forms an outer peripheral surface of the blanket cylinder.
2. Description of Related Art
An offset rotary press (printing press) is provided with a plurality of printing units corresponding to colors to be printed. Each of the printing units is configured so as to distribute ink appropriately to form a thin ink film in a process in which ink charged in an ink fountain is transferred successively by an ink roller group arranged in a row. The formed ink film is transferred to a press plate wound around a plate cylinder, and after the ink film is transferred to the outer peripheral surface of a blanket cylinder, printing is performed on a web ruining while being brought into contact with the rotating blanket cylinders.
The outer peripheral surface of the blanket cylinder, which consists of an elastic member mainly made of rubber or the like, is liable to be subjected to permanent setting, breakage, and other damage, and therefore may need to be replaced. For this reason, the outer peripheral surface of the blanket cylinder has so far been constructed so as to be removable.
FIGS. 3
to
5
are schematic views showing typical constructions of conventional blanket cylinders. These figures show a printing unit capable of doing perfecting (printing on both sides of a web) by disposing the blanket cylinders on both sides of a sheet pass line in an opposed manner.
FIGS.
3
(
a
) and
3
(
b
) show a construction of a blanket cylinder of a type such that a sheet-form blanket is wound around a basic shaft roller. As shown in these drawing figures., a blanket cylinder
30
is formed with a slit-form groove
16
over the whole length in the axial direction in the outer peripheral surface of a basic shaft roller
24
. The blanket cylinder
30
is configured so that both ends in the circumferential direction of a sheet-form blanket
15
are inserted into the groove
16
so as to be held (fixed) by a tightening device
23
. A member denoted by reference numeral
12
in FIG.
3
(
a
) is a plate cylinder, and a member denoted by reference numeral
13
is a press plate. Both ends in the circumferential direction of the press plate
13
are gripped by a gripping portion
12
a
provided in the outer peripheral surface of the plate cylinder
12
so that the press plate
13
is wound on the outer peripheral surface of the plate cylinder
12
. Also, a web
14
runs while being held between the upper and lower blanket cylinders
30
,
30
.
The blanket cylinder
30
of this type has a problem in that the work efficiency in replacing the blanket
15
is low, so that the replacement work takes much time. Also, the blanket
15
is subjected to a high tension in the vicinity of the tightening device
23
and is less prone to be subjected to a tension in a portion distant from the tightening device
23
. Therefore, the blanket cylinder
30
also has a problem in that the thickness of the blanket
15
undesirably changes depending on the tension, so that the initial cylinder accuracy is poor and therefore the printing quality varies. Further, the blanket cylinder
30
also has problems in that rotating vibrations and noise are generated by the slit-form groove
16
opened in the axial direction in the cylinder surface of the tightening device
23
, and in that much spoilage is produced because the slit-form groove
16
provides a non-printing portion.
FIGS.
4
(
a
),
4
(
b
) and
5
show a blanket cylinder of a type such that a cylindrical (sleeve-form) blanket is fitted on a basic shaft roller. As shown in FIGS.
4
(
a
) and
4
(
b
), a blanket cylinder
31
is configured so that a cylindrical blanket
10
is fitted onto the outer peripheral surface of a basic shaft roller
3
. The cylindrical blanket
10
is constructed by integrally fitting a skin layer
17
formed of an elastic material, such as rubber, on a metallic sleeve
8
. Also, as shown in
FIG. 5
, the cylindrical blanket
10
is rotatably supported between frames
5
a
,
5
b
by bearings
6
a
,
6
b
fitted in bushes
7
a
,
7
b
. Therefore, the work for attaching and detaching the cylindrical blanket
10
to and from the shaft roller
3
is performed in the state in which one bearing
6
a
together with the bush
7
a
is once removed from frame
5
a
to form a predetermined space, and thereby the shaft roller
3
is supported on one side by the other bearing
6
b.
In the end portion of the outer peripheral surface of the shaft roller
3
on the side on which the cylindrical blanket
10
is attached or detached, a plurality of air holes
18
are formed in the circumferential direction. These air holes
18
communicate with an air supply hole
19
formed in the shaft roller
3
, and are connected to an air compression source
22
via a pipe
20
, a solenoid valve
21
, and the like, so that compressed air can be blown out in the radial direction through the air holes
18
at proper timing. The supply of compressed air toward the air holes
18
forms a compressed air layer in a gap between the shaft roller
3
and the cylindrical blanket
10
. This compressed air layer increases the inside diameter of the cylindrical blanket
10
so that the cylindrical blanket
10
can be attached and detached easily to and from the shaft roller
3
. The inside diameter of the cylindrical blanket
10
is formed so as to be slightly smaller than the outside diameter of the shaft roller
3
. At the time of operation after fitting, therefore, the supply of compressed air is stopped, by which the cylindrical blanket
10
is contracted so as to come into close contact with the shaft roller
3
.
For the blanket cylinder
31
of this type having the above-described configuration, the formation of the slit-form groove
16
in the outer peripheral surface of the shaft roller
3
, which is necessary for the before-mentioned blanket cylinder
30
, is unnecessary, and the time taken for the blanket to be replaced can be shortened. Also, since there is no joint on the surface of the blanket
10
, a non-printing portion on the. blanket cylinder
31
is eliminated, and the non-printing portion is decreased to only the range of a portion where the press plate
13
is fitted to the plate cylinder
12
, by which spoilage can be decreased. Also, since there is no joint on the surface and variations in thickness of blanket are small, the cylinder accuracy is increased so that vibration noise is reduced, and also the printing quality is stabilized from the early stage.
When the web
14
passes through the printing units successively, ink and moistening water are supplied to the web
14
, so that the moisture content of the web
14
increases gradually, with the result that the web
14
becomes liable to elongate in the running direction. In the rotary press for doing multi-color printing by arranging a plurality of printing units, therefore, the elongation is accumulated increasingly toward the downstream side, so that the tension acting on the web
14
tends to decrease gradually.
To cope with this problem, a method can be conceived in which as shown in
FIG. 6
, for example, the diameters D
1
, D
2
and D
3
of blanket cylinders
31
,
32
, and
33
are relatively increased successively toward the downstream side in the running direction of the web
14
(D
1
<D
2
<D
3
) and the peripheral speeds V
1
, V
2
and V
3
of the blanket cylinders
31
,
32
and
33
are slightly increased successively (V
1
<V
2
<V
3
), by which the elongation of the web
14
is absorbed to prevent the decrease in the tension. Also, a method can be conceived in which the rubber material on the outer peripheral surface of each blanket cylinder is made of a material having different paper feed characteristics, and the decrease in the tension is preve
Armstrong Westerman & Hattori, LLP
Evanisko Leslie J.
Mitsubishi Heavy Industries Ltd.
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