Printing – Processes – Condition responsive
Reexamination Certificate
1999-08-31
2002-04-09
Eickholt, Eugene (Department: 2854)
Printing
Processes
Condition responsive
C101S365000
Reexamination Certificate
active
06367385
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an ink film thickness control method and apparatus used in exchanging a printing plate in a multi-color printing press having a plurality of printing units each of which supplies ink in an ink fountain to a printing plate through an ink roller group and prints the ink supplied to the printing plate on printing paper.
FIG. 8
shows the main part of an ink supply apparatus in each printing unit (printing section) of a multi-color printing press. Referring to
FIG. 8
, reference numeral
1
denotes an ink fountain;
2
, ink stored in ink fountain
1
;
3
, an ink fountain roller;
4
, a plurality of ink fountain keys juxtaposed along the axial direction of ink fountain roller
3
;
5
, an ink ductor roller;
6
, an ink roller group;
6
A, ink from rollers in the ink roller group
6
;
7
, a printing plate; and
8
, a plate cylinder.
In the ink supply apparatus having the above arrangement, the ink
2
in ink fountain
1
is supplied by adjusting the aperture ratios of ink fountain keys
4
. The ink supplied to ink fountain roller
3
is supplied to printing plate
7
via ink roller group
6
by feed operation of ink ductor roller
5
. Printing paper fed from a paper feed section is printed with the ink supplied to printing plate
7
.
When the printing plate is changed to a new printing plate
7
, the aperture ratio of each ink fountain key
4
and the rotation ratio of the ink fountain roller
3
are preset to values corresponding to the image of the printing plate
7
. More specifically, the aperture ratio of each ink fountain key
4
and the rotation ratio of ink fountain roller
3
are set to values corresponding to the image of printing plate
7
, and the ink
2
in ink fountain
1
is supplied to new printing plate
7
via ink roller group
6
. In this case, test printing is performed before final printing to adjust the ink supply amount, thereby obtaining a satisfactory color tone. With this operation, a desired ink film thickness distribution (gradient of thickness of the ink film) is formed on ink roller group
6
.
In the conventional ink supply apparatus, however, when the printing plate is exchanged with new printing plate
7
, the ink film thickness distribution for the previous printing plate remains on ink roller group
6
. In this case, the ink film thickness distribution for the previous printing plate must be gradually changed to the ink film thickness distribution for printing plate
7
. This operation requires excessive adjustment of the ink supply amount and test printing until a satisfactory color tone is obtained. The excessive adjustments of ink supply amount required by this operation results in problems including an increase in preparation time for printing, an increase in work load, waste of printing materials, a decrease in production efficiency, and increase in cost.
“INK FILM THICKNESS CONTROL METHOD FOR INK SUPPLY APPARATUS” is proposed in U.S. Pat. No. 5,884,562 for the purpose of decreasing the number of times ink supply amount is adjusted and test printing is performed until a satisfactory color tone is obtained. In this ink film thickness control method, “ink removing” is performed before exchanging the printing plate with a new printing plate.
This will be described in detail. After final printing using a printing plate, a printing unit is selected on a display (not shown). The “ink removing” mode (function) is selected, and the feed operation of ink ductor roller
5
is stopped. The printing press is operated while keeping the printing plate mounted, thereby printing a predetermined number of paper sheets. With this operation, a minimum ink film thickness distribution Ma (
FIG. 7A
; to be referred to as a first ink film thickness distribution hereinafter) necessary for printing is left on ink roller group
6
such that the ink film thickness decreases from the upstream to the downstream. More specifically, an ink film thickness distribution corresponding to the image of the printing plate is removed from the ink film thickness distribution formed on ink roller group
6
, and the first ink film thickness distribution Ma corresponding to the no-image portion of the printing plate is left.
After the printing plate is changed to a new printing plate
7
, the “pre-inking II” function is selected on the display to perform the “pre-inking II” operation. In “pre-inking II”, the aperture ratios of ink fountain keys
4
and the rotation ratio of ink fountain roller
3
are preset to values corresponding to the image of printing plate
7
. After this, the printing press is operated. Ink ductor roller
5
is caused to perform the feed operation a predetermined number of times to superpose an ink film thickness distribution Mb (
FIG. 7B
; to be referred to as a second ink film thickness distribution hereinafter) corresponding to the image of new printing plate
7
on the first ink film thickness distribution Ma left on ink roller group
6
.
After second film thickness distribution Mb is superposed on first ink film thickness distribution Ma, a predetermined number of sheets are test-printed. The density of the test-printed matters is checked. If the color tone is satisfactory, ink film thickness control by “ink removing+pre-inking II” is ended, and the operation shifts to final printing. On the other hand, if the color tone checked by density check is not satisfactory, the ink film thickness distribution is finely adjusted by “pre-inking (+)” or “pre-inking (−)”, and test-printing is performed again.
In this proposed method, however, when printing plates for the plurality of printing units are simultaneously exchanged, the printing units print the same number of printing sheets conveyed from a feed section upon “ink removing” in the respective printing units. At this time, because of ink trapping (a phenomenon wherein ink of early printing is superposed on ink of succeeding printing), the upstream printing units have too little ink while ink in the downstream printing units does not decrease. For this reason, a satisfactory ink film thickness distribution cannot be formed for the subsequent printing operation, and the amount of paper wasted in the transition to the new printing plate increases.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an ink film thickness control method and apparatus for a multi-color printing press, which accurately form an ink film thickness distribution for the next printing operation to prevent waste paper.
It is another object of the present invention to provide an ink film thickness control method and apparatus for a multi-color printing press, which can appropriately perform “ink removing” in each of printing units which simultaneously exchange printing plates.
In order to achieve the above objects, according to the present invention, there is provided an ink film thickness control method for a multi-color printing press. The printing press has a plurality of printing units for continuously performing designated color printing on a printing paper by means of ink supplied to a printing plate through an ink roller group. The method includes the steps of when at least two of the printing units, as plate exchange printing units, exchange to new printing plates are simultaneously performed, setting the number of printing sheets to be printed for ink removing in units of plate exchange printing units of at least two printing units of the printing press, turning off an ink feed operation in each of the plate exchange printing units, and performing printing for ink removing in each of the plate exchange printing units on the basis of the set number of printing sheets while keeping the previous printing plate mounted. The method can include exchange of printing plates used at the at least two printing units with second printing plates to be used at the at least two printing units. The method is employed to form a first ink film thickness distribution minimum necessary for printing on the ink roller group of the plate exchange prin
Blakely & Sokoloff, Taylor & Zafman
Eickholt Eugene
Komori Corporation
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