Advancing material of indeterminate length – Processes – Involving plural feeding means
Reexamination Certificate
1999-04-19
2001-01-23
Walsh, Donald P. (Department: 3653)
Advancing material of indeterminate length
Processes
Involving plural feeding means
C226S008000, C226S024000, C226S111000, C101S228000
Reexamination Certificate
active
06176410
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a method and an apparatus for controlling web delivery running in a printing machine (electronic printing machine etc.).
FIG. 6
is a schematic view showing the whole of an electronic printing machine used for printing one side and both sides of paper. For this electronic printing machine, as shown in
FIG. 6
, a web
14
supplied by a roll
20
set on a feeder
1
is drawn by a feed drag roller
7
and is supplied to a printing unit
2
. Subsequently, the web
14
is put into print (toner is made to adhere), and toner is fixed to the web
14
by a first fixing roller
3
and a second fixing roller
4
. Thus, after passing through the second fixing roller
4
, the web
14
is discharged by a discharge drag roller
13
, and is cut and arranged properly by a cutter
6
, thereby completing printed matters. In
FIG. 6
, reference numerals
9
a
,
9
b
and
9
c
denote paper pressing rollers,
10
a
,
10
b
and
10
c
denote servomotors, and
11
denotes a web brake.
When only one side of the web
14
is printed by the aforementioned electronic printing machine (in the case of one-side printing), after the web
14
passes through the feed drag roller
7
, one side of the web
14
is printed by printing units
2
a
and
2
b
, and toner is fixed by the first fixing roller
3
. Then, the web
14
is introduced to an intermediate drag roller
8
. Further, after one side of the web
14
is printed by printing units
2
c
and
2
d
and is fixed by the second fixing roller
4
, the web
14
, being sent to the cutter
6
by the discharge drag roller
13
, is cut and arranged properly, thereby completing printed matters.
When both sides of the web
14
is printed by the aforementioned electronic printing machine (in the case of two-side printing), after the top surface (one side) of the web
14
is printed by the printing units
2
a
and
2
b
and is fixed by the first fixing roller
3
, the web
14
is turned over by an inversion turn bar
5
and sent to the printing units
2
c
and
2
d
by the intermediate drag roller
8
, by which the back surface is printed. Next, after being fixed by the second fixing roller
4
, the web
14
is cut and arranged properly by the cutter
6
as in the case of one-side printing, thereby completing two-side printed matters.
In the conventional electronic printing machine, the web
14
is heated when passing through the first fixing roller
3
, so that the length of paper is changed. Therefore, in multi-color printing by process color, in which overprinting must be performed by the printing units
2
c
and
2
d
successively, there arises a problem in that the print registering (printing registration) goes wrong, and accurate multi-color printing cannot be performed. For this reason, conventionally in the actual situation, a configuration is used such that the intermediate drag roller
8
is disposed between the feed drag roller
7
and the discharge drag roller
13
to control tensions between the feed drag roller
7
and the intermediate drag roller
8
and between the intermediate drag roller
8
and the discharge drag roller
13
, by which the elongation of the web
14
passing through the printing units
2
a
and
2
b
and the elongation of the web
14
passing through the printing units
2
c
and
2
d
are made equal to each other, whereby the accuracy of print registering (printing registration) is improved.
Next, a mechanism of generating a tension between the drag rollers will be described below with reference to the figure. The book titled “Offset Printing Machines” published by Japan Printing News Co., Ltd. describes that generally, an inlet tension of printing section, that is, a tension in a region ranging from the feeder
1
to the feed drag roller
7
is a base tension for paper tension at all paper paths of the printing machine downstream of the feed drag roller
7
, and is a dominant factor contributing to the stabilization of printing accuracy etc. Also, the aforementioned book gives an equation for infeed tension. If in this equation, the metering roller is replaced with the feed drag roller and the printing unit peripheral velocity is replaced with the intermediate drag roller peripheral velocity, the following equation can be obtained.
F
z
≈
1
(
1
+
E
η
T
z
)
{
a
·
1
·
E
V
0
-
V
1
V
0
+
F
1
}
(
1
)
where, F
2
is infeed tension, F
1
is feed drag roller inlet tension, V
0
is intermediate drag roller peripheral velocity, V
1
is feed drag roller peripheral velocity, E is Young's modulus of paper, &eegr; is coefficient of viscosity of paper, a is paper thickness, l is paper width, and T
2
is time constant (time taken for paper to pass through a span from the feed drag roller to the intermediate drag roller).
A tension between the intermediate drag roller
8
and the discharge drag roller
13
can also be determined if in Equation (1), the intermediate drag roller peripheral velocity is replaced with the discharge drag roller peripheral velocity, the feed drag roller peripheral velocity is replaced with the intermediate drag roller peripheral velocity, and the feed drag roller inlet tension F
1
is replaced with the infeed tension F
2
determined by Equation (1).
Thereupon, for example, even if the tension F
1
of the feeder
1
is kept constant, when the peripheral velocity V
1
of the feed drag roller
7
or the peripheral velocity V
0
of the intermediate drag roller
8
is changed, the infeed tension F
2
, that is, the paper tension between the feed drag roller
7
and the intermediate drag roller
8
changes. This also holds true for the paper tension between the intermediate drag roller
8
and the discharge drag roller
13
. In this tension control, it is unpreferable to carry out torque control for keeping the torque of motor for driving the drag roller because the torque control causes a fluctuation in drag roller peripheral velocity. Conventionally, therefore, the speed has been controlled for the drive of the drag roller.
However, when such speed control is carried out, a problem described below arises. In the conventional speed control, in the case where slack is produced in the web
14
after it passes through the drag rollers
7
,
8
or
13
, if the peripheral velocity difference between the drag rollers is small, it takes considerable time before the slack is removed and the tension is stabilized, so that much spoilage (paper loss) occurs before printed matters with accurate print registering (printing registration) in the running direction of the web
14
can be obtained.
OBJECT AND SUMMARY OF THE INVENTION
The present invention has been made to solve the above problem, and an object thereof is to provide a method and an apparatus for controlling web delivery running at the start time of printing, in which the slack of a web (paper) can be removed in a short period of time, the time taken for a tension to be stabilized after the start of printing (after the start of operation) can be shortened greatly, and the occurrence of spoilage caused by inaccurate print registering (deviation of registering) in the web running direction can be reduced significantly.
To achieve the above object, in the method for controlling web delivery running at the start time of printing in accordance with the present invention, drag rollers disposed in a region from the paper feed side to the paper discharge side of a printing machine are driven one after another from the paper feed side with torque control, by which the slack of a web is removed successively from the upstream side of a web delivery running path.
Also, in the method for controlling web delivery running at the start time of printing in accordance with the present invention, by giving a preliminary tension to between the drag rollers, the time from when the torque control state in which the drag roller is driven with torque control is switched to the speed control state in which the drag roller is driven with speed control to when the tension
Akatsuka Masakazu
Hirose Hitoshi
Tasaka Norifumi
Ueda Yoshio
Alston & Bird LLP
Mitsubishi Heavy Industries Ltd.
Walsh Donald P.
Webb Collin A.
LandOfFree
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