Printing – Planographic – Multicolor
Reexamination Certificate
2001-02-13
2003-09-02
Eickholt, Eugene H. (Department: 2854)
Printing
Planographic
Multicolor
C101S352010, C101S352050, C101S137000, C101S211000, C101S492000
Reexamination Certificate
active
06612233
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a method for operating a sheet-fed offset press and, more particularly, to a method for operating a sheet-fed offset press in which an oscillating roller accomplishes an oscillating motion. Also, the present invention relates to an oscillation mechanism for an oscillating roller in an ink supply system for a sheet-fed offset press.
First, a method for operating a sheet-fed offset press, which relates to the present invention, will be described.
To distribute ink on rollers, some number of ink rollers in an offset press have so far been oscillated in the axial direction of the rollers. For a multi-color sheet-fed offset press in which ink rollers are oscillated, sheets supplied from a sheet-feeder are generally printed in one color at each printing station. Each printing station consists of an ink supply system, a dampening system for supplying water, and a number of rollers. Some of these rollers act as oscillating rollers that serve to distribute ink in the roller-width direction.
Many of these oscillating rollers always oscillate by a fixed amount. However, if the oscillating motion of the oscillating rollers continues during the time when printing operation is stopped temporarily for some reason, an ink supply-demand balance between ink transferred to a sheet and ink on the roller, which has been attained during printing operation, is lost undesirably. Specifically, during a steady printing operation, a balance is maintained between the amount of ink supply and the amount of ink transferred to paper sheets such that in printing portions where ink transfers to sheets, the ink supply amount increases, and in non-printing portions where only a small amount of ink transfers to the sheet, the ink supply amount decreases. Therefore, the ink distribution in the axial direction on the rollers is not uniform. However, when the press operation is stopped for some reason, for example, for an error in sheet position setting, if the oscillating rollers continue to be driven, the distribution of ink on the rollers becomes uniform by the distributing effect of the oscillating motion. As a result, when the printing operation is restarted, a number of paper sheets are printed with undesirable nonuniformity until the balanced state maintained before the stoppage of printing operation is achieved again.
In recent years, in some offset presses, the oscillation is started and stopped according to the timing of press operation to decrease such spoilage at the start of printing operation. An example of such a press is in Japanese Patent Laid-open Publication No. 11-240139 (No. 240139/1999). In this press, as the printing operation is started, the oscillation of the oscillating roller having a null or minimum amplitude at first is gradually increased, and the amplitude of the oscillating roller reaches a maximum when a form roller is brought into contact with a plate cylinder. In addition, Japanese Patent Publication No. 7-102698 (No. 102698/1995) discloses a printing press in which the oscillation is started or stopped at the same time that a form roller is separated from or is brought into contact with a plate cylinder.
Next, a conventional oscillation mechanism for an oscillating roller in an ink supply system for a press will be described.
A conventional example of an oscillation mechanism for a form roller, which has been disclosed in the aforementioned Japanese Patent Provisional Publication No. 11-240139 (No. 240139/1999), is explained below with reference to
FIG. 9
showing the outline of a general offset press,
FIG. 10
showing a oscillation drive system,
FIG. 11
showing an essential part of a mechanism for starting and stopping oscillation, and
FIG. 12
showing a cross section of FIG.
11
.
Referring now to
FIG. 9
, paper sheets supplied from a sheet-feeder
301
are printed in a printing system
302
, and are stacked and discharged to a sheet discharge section
305
. The multi-color printing system
302
such as an offset press is composed of a plurality of printing units
302
a
,
302
b
,
302
c
and
302
n
provided according to the number of printing colors, and each printing unit include an ink supply system
303
for supplying ink, which is composed of a plurality of rollers, and a dampening system
304
for supplying dampening water. Of these systems, the ink supply system
303
is provided with a plurality of oscillating rollers
306
that oscillate in the axial direction to slidingly rub form rollers in order to distribute ink uniformly in the width direction.
FIG. 10
is a system diagram of a drive for oscillating the oscillating rollers
306
. In this drive system, a driving force is transmitted from a crank of an oscillation drive source
307
, which is driven by a drive system
309
for the machine, to an oscillation drive pin
310
provided at the tip end of an oscillation drive lever
311
via a drive link
308
. Also as shown in
FIG. 12
, the oscillation drive lever
311
oscillates around a pin
312
provided on bearers
318
fixed to a machine frame. An oscillating lever
313
, which oscillates around the pin
312
in the same way, consists of portions
313
a
and
313
b
for driving the oscillating rollers
306
and a portion
313
c
subjected to an oscillating force by the oscillation drive pin
310
.
At the end of the oscillating lever
313
a
,
313
b
is provided an oscillation transmitting portion (details thereof is omitted)
317
for transmitting the oscillating force to the shaft end of the oscillating roller
306
. Also, the portion
313
c
is provided with an oscillation drive changeover mechanism
319
that is composed of a change over member
314
engaging with the oscillation drive pin
310
to accomplish a changeover from transmission to stoppage of oscillation and vice versa and a changeover actuator
316
which moves the changeover member
314
to accomplish a changeover from transmission to stoppage of oscillation and vice versa.
As shown in
FIG. 11
, the changeover member
314
is formed with an arcuate elongated hole
315
such that there is a gap large enough for the oscillation drive pin
310
to slide, and the oscillation drive pin
310
is moved by the drive link
308
so that the range of oscillation produced by the oscillation drive lever
311
is not interfered. Thus, as shown in
FIG. 12
, the changeover member
314
engages with the oscillation lever
313
c
so as to fit to it and be capable of turning around the oscillation drive pin
310
.
The changeover member
314
is moved by the actuator
316
or change over the direction of the elongated hole
315
from A to B and vice versa in
FIG. 11
, by which the oscillation force is transmitted and stopped. Specifically, when the changeover member
314
is made in the state of A by the actuator
316
, the oscillation drive pin
310
oscillated by the oscillation drive lever
311
oscillates only in the elongated hole
315
, so that the oscillation force is not transmitted to the oscillation lever
313
. On the other hand, when the changeover member
314
is made in the state of B, the oscillation force can be transmitted.
OBJECT AND SUMMARY OF THE INVENTION
In these related arts, the timing of start or stop of oscillation consists of synchronization with the contact of form rollers with the form plate and the start and stop of printing operation. According to a study made by the inventors, it has been found that the timing of start and stop of drive of oscillating rollers described in the related arts is not always optimum. Accordingly, an object of the present invention is to provide a method in which the drive of oscillating rollers is optimized, and spoilage caused by the short-time stoppage of a printing press during operation is minimized.
The present invention provides a method for operating a sheet-fed offset press in which an oscillating roller accomplishes an oscillating motion, comprising: a step of receiving a command to stop printing operation; a step of stopping the oscillating motion of the os
Armstrong Westerman & Hattori, LLP
Eickholt Eugene H.
Mitsubishi Heavy Industries Ltd.
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