Rotary die cutter

Details Rotary die cutter Rotary die cutter

1999-03-17

2001-05-15

Goodman, Charles (Department: 3724)

Cutting

With means to control or modify temperature of apparatus or...

Of tool

C083S343000

Reexamination Certificate

active

06230597

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a rotary die cutter for blanking corrugated fiberboard sheets or the like.
As a rotary die cutter of this type, a cutter, for example, shown in
FIGS. 4
to
6
has been publicly known. In this cutter shown in
FIG. 4
, frames
1
are erected on both sides, right and left, and a die cut cylinder
3
and an anvil cylinder
4
are rotatably supported on these frames
1
via bearings
5
.
The die cut cylinder
3
has a cylindrical outer peripheral surface, and at opposite ends thereof are provided support shafts
3
a
coaxially. Each of the support shafts
3
a
is rotatably supported on the frame
1
via the bearing
5
. Similarly, the anvil cylinder
4
also has a cylindrical outer peripheral surface, and at opposite ends thereof are provided support shafts
4
a
coaxially. Each of the support shafts
4
a
is rotatably supported on the frame
1
via the bearing
5
.
At a portion where each support shaft
3
a
protrudes from the frame
1
, a gear
6
is provided to cause the die cut cylinder
3
to rotate. Also, at a portion where each support shaft
4
a
protrudes from the frame
1
, a gear
7
is provided to cause the anvil cylinder
4
to rotate. These gears
6
and
7
mesh with each other.
Each frame
1
is provided with a side cover
8
for covering the gears
6
and
7
. This side cover
8
is constructed such that a portion under the gears
6
and
7
(a portion under the bearings
5
) forms an oil reservoir
8
a
for storing a lubricating oil. The lubricating oil stored in the oil reservoir
8
a
adheres to a gear
10
supported rotatably on the frame
1
, and further adheres to the gear
7
meshing with the gear
10
, so that the gears
7
and
6
are lubricated. The bearing
5
is lubricated by grease loaded inside.
As shown in
FIG. 6
, a blanking section itself is constructed so that the rotation is transmitted from, for example, a printing unit (not shown) on the upstream side by a connection gear
13
meshing with the gear
6
, and is further transmitted to a unit (not shown) on the downstream side by a connection gear
14
meshing with the gear
6
.
As shown in
FIGS. 4 and 5
, a blanking die
11
is installed on the die cut cylinder
3
, and this blanking die
11
is provided with knives
11
a
. The knife
11
a
performs blanking of a corrugated fiberboard sheet
12
by holding the corrugated fiberboard sheet
12
between the knife
11
a
and the surface of the anvil cylinder
4
.
The rotary die cutters come in two types: a cutting type called soft cut in which a sawtooth knife is used as the knife
11
a
and a rubber anvil is used as the anvil cylinder
4
, and a cutting type called hard cut in which a straight tooth knife is used as the knife
11
a
and a metal anvil is used as the anvil cylinder
4
.
In the case of the latter hard cut, since cutting is performed by pressing the hard knife
11
a
on the hard anvil cylinder
4
, the pressing amount, in other words, a center distance between the die cut cylinder
3
and the anvil cylinder
4
is required to be maintained precisely (usually, an accuracy in the order of {fraction (1/100)} mm is strictly kept). If such a center distance cannot be kept, an uncut portion remains on the corrugated fiberboard sheet
12
, or the blade edge of the knife
11
a
is collapsed by an excessive pressure.
In the above-described rotary die cutter, the bearings
5
are heated by the rotation of the die cut cylinder
3
and the anvil cylinder
4
, and part of this heat is transmitted to the frames
1
, so that the temperature of the frames
1
rises. Therefore, the frame
1
is elongated by thermal expansion, resulting in an increase in the distance between the support shafts
3
a
and
4
a
of the die cut cylinder
3
and the anvil cylinder
4
.
For this reason, a cutting pressure of the knife
11
a
acting on the anvil cylinder
4
decreases, or sometimes a gap is produced between the knife
11
a
and the anvil cylinder
4
, which leads to a possibility that improper cutting occurs. To overcome this problem, with the elapse of time, it is necessary to adjust the aforesaid distance between the support shafts
3
a
and
4
a
, or to adjust the blanking die
11
, which causes the hindrance to productivity.
Also, part of the aforesaid heat is transmitted to the die cut cylinder
3
and the anvil cylinder
4
via the support shafts
3
a
and
4
a
, respectively, by which the temperature of the cylinders
3
and
4
are also increased. At this time, after the support shafts
3
a
and
4
a
first becomes hot, the heat conducts gradually from both the ends toward the central portion of the cylinders
3
and
4
. That is to say, in each cylinder
3
,
4
, a temperature gradient is created from both the ends to the central portion. Thus, as indicated by the dashed line in FIG.
4
, each cylinder
3
,
4
is thermally deformed into a concave form. In this case, a gap between the knife
11
a
and the anvil cylinder
4
is narrow at portions at both ends of each cylinder
3
,
4
, and a gap between the knife
11
a
and the anvil cylinder
4
is wide at the central portion thereof, so that the cutting conditions becomes nonuniform in the width direction.
Further, since the amount of temperature rises of the frames
1
and the cylinders
3
and
4
are not equal, there is a difference between the change amount of center distance between the cylinders
3
and
4
caused by the thermal expansion of the frames
1
and the change amount (average amount in the width direction) of outside diameter of each cylinder
3
,
4
caused by the thermal expansion of each cylinder
3
,
4
itself. Therefore, with the elapse of operation time, the pressing pressure (average pressure in the width direction) of the knife
11
a
on the anvil cylinder
4
changes undesirably, which also makes the cutting conditions nonuniform.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above situation, and an object thereof is to provide a rotary die cutter which can keep a steady cutting state even if the rotary die cutter is operated for a long period of time.
Invention of a first group
To achieve the above object, the invention of a first group provides a rotary die cutter having frames for rotatably supporting a die cut cylinder and an anvil cylinder via a bearing, characterized in that oil is circulated in the die cut cylinder and/or the anvil cylinder.
Thereupon, the heat which is generated at each bearing and heats the opposite end portions of each cylinder can be distributed to the whole of each cylinder. Therefore, the temperature difference in the width direction (axial direction) of the cylinder can be reduced, so that the temperature of the cylinder can be made substantially uniform. As a result, the cylinder can be prevented from being warped into a concave form, so tat a steady cutting state can be maintained even if the machine is operated for a long period of time.
Also, in the invention of the first group, a lubricating oil for a gear for driving they cylinder is used as the oil, and the lubricating oil can be scattered by the gear and splashed on the frame.
By this configuration, the temperature of the frame becomes almost the same as the temperature of the cylinder. Therefore, a difference between the change amount of center distance between the die cut cylinder and the anvil cylinder caused by the thermal expansion of frames and the thermal expansion amount of each cylinder can be decreased. Specifically, even if the center distance between the cylinders is changed by the temperature of lubricating oil, the dimension between the cylinders can be maintained precisely so that good cutting (blanking) work can be done. In other words, a steadier cutting state can be maintained even if the machine is operated for a long period of time.
Invention of a second group
To achieve the above object, the invention of a second group provides a rotary die cutter having frames for rotatably supporting a plurality of opposingly disposed cylinders, such as a die cut cylinder and an anvil

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