Printing – Inkers – Fountains
Reexamination Certificate
2000-03-28
2002-05-21
Eickholt, Eugene (Department: 2854)
Printing
Inkers
Fountains
C101S211000, 36, C356S407000, C382S112000
Reexamination Certificate
active
06389968
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an ink supply control device for printing machines and a method for controlling ink supply, specifically to an adjustment of ink volume under consideration of color impurities contained in each of the color inks.
2. Description of the Prior Art
Generally, color-printed-matters are printed with four-color inks such as cyan (C), magenta (M), yellow (Y) and black (K).
FIG. 11
is a brief side view illustrating the overall structure of an offset press.
Printing plates for black, for cyan, for magenta, and for yellow are respectively disposed on each of plate cylinders
45
installed in a first-printing-unit
41
, a second-printing-unit
42
, a third-printing-unit
43
, and a fourth-printing-unit
44
.
Color printing is carried out on printing papers fed from the feeder
40
and passing through each of the printing units with the four-color inks by superimposing each of the color-inks. Each of the color-inks is printed on the printing paper as a plurality of fine dots. A variety of colors can be expressed by accurately adjusting the dot area ratios of each of the color-inks.
Inking units
55
for supplying ink to the printing plates disposed on the plate cylinders
45
are provided respectively to the first-printing-unit
41
, the second-printing-unit
42
, the third-printing-unit
43
, and the fourth-printing-unit
44
.
FIG. 12
is a side view illustrating the overall structure of the inking unit and vicinity thereof. Ink is stored in an ink fountain
50
consisting of an ink fountain roller
52
and a blade
51
.
The ink
10
fed via a gap
51
S formed between the blade
51
and the ink fountain roller
52
is supplied to the printing plate disposed on the plate cylinder
45
through an ink roller group
53
including pluralities of ink rollers therein. A volume of the ink supplied to the printing plate can be adjusted by controlling an opening degree of the gap
51
S formed between the blade
51
and the ink fountain roller
52
as a result of opening and closing the blade
51
.
Dots printed on the printing papers become unexpectedly larger than they should be if a larger volume of ink than the adequate volume is supplied to the plate. This is because a variation of colors can only be expressed by accurately adjusting densities of the dots (an ink volume on the printing paper). As a result, printing accuracy may be decreased if the dots are formed inaccurate in size.
Ink supply volume to each of the printing units needs to be accurately adjusted. It is, however, hard for the operator to calibrate the ink supply volume to an adequate volume through his/her visual observations. In order to solve the problems, a conventional technique is used in which ink densities (ink volume) are measured at solid patches (patches having 100% dot area ratios) each consisting of cyan (C), magenta (M), and yellow (Y) and respectively printed on a printing paper. Ink supply volume is adjusted by controlling opening degrees of the gap
51
S of the ink fountain
50
determined according to the densities thus measured.
In the case of adjusting ink volume by measuring the solid patches, the following problems may occur; 1) A phenomenon called “dot gain” in which the size of dots printed on the printing paper is unexpectedly increased due to viscosity of ink and other factors, and 2) Another phenomenon called “trapping” in which superimposition of the color ink is in poor condition because of characteristics of the inks and improper conditions of the printing machine.
By carrying out printing with dots, a slight shift in color may be observed because of “dot gain” and/or “trapping”. There is then a high probability of decreasing printing accuracy as well as obtaining undesired colors if ink supply volume is adjusted according to color densities measured at a solid patch. This is because solid patches are patches having 100% dot area ratios, not consisting of dots.
In order to solve the problems, Japanese laid-open publication No. SHO 62-146633 discloses a technique in which ink supply volume is adjusted according to ink densities measured at a gray patch consisting of cyan (C), magenta (M), and yellow (Y) and printed on a printing paper.
With this technique, ink supply volume can be adjusted in a relatively accurate manner because densities of the color inks can be detected in consideration of “dot gain” and/or “trapping” as a result of printing the inks of cyan (C), magenta (M), and yellow (Y) in dots so as to superimpose them on one another.
A certain amount of color component different from the original color component of color ink (color impurity) is contained in each of the color inks as illustrated in FIG.
13
A. Color-ink, such as cyan (C) does not consist solely (100%) of the color component of cyan, but also contains other color components such as magenta (M), and yellow (Y).
In
FIGS. 13A and 13B
, Cc, Cy, and Cm respectively represent color components of cyan, yellow, and magenta contained in cyan ink. Similarly, Mm, My, and Mc respectively represent color components of magenta, yellow, and cyan contained in magenta ink in these figures. Further, Yy, Yc, and Ym respectively represent color components of yellow, cyan, and magenta contained in yellow ink.
As described earlier, a certain amount of color-impurities are contained in each of the color inks as illustrated therein. The ratios of the color-impurities vary depending on the color ink (those color-impurities are exemplarly illustrated in the same ratios in FIGS.
13
A and
13
B). For instance, if the color-component of cyan on a gray patch is detected, the color density of cyan in the gray patch is measured as a total sum of color density of color-impurities of Mc and Yc each contained respectively in magenta ink and yellow ink in addition to color-component of cyan Cc contained in cyan ink.
Similarly, if the color-component of magenta on the gray patch is detected, the color density of magenta in the gray patch is measured as a total sum of the color density of Ym and Cm in addition to Mm. Further, if the color-component of yellow on the gray patch is detected, the color density of yellow in the gray patch is measured as a total sum of the color density of Cy and My in addition to Yy.
As described earlier, the ink supply volume of cyan ink, magenta ink, and yellow ink can not be adjusted based solely on the color densities of the color-component of cyan, magenta, and yellow detected from the gray patch because the ratios of the color-impurities vary depending on the color of the ink.
In order to solve such a problem, Japanese patent laid-open publication No. SHO58-45527 discloses a method for measuring ink densities and a device using the same in which the following procedures are described. Color densities of solid patches printed with color-inks of cyan, magenta, and yellow being used for actual printing are measured respectively prior to the printing, and then color densities Cc, Cm, Cy, Mm, Mc, My, Yy, Ym, and Yc are stored as predetermined values.
Thereafter, color-densities of an area where color-inks of cyan, magenta, and yellow being superimposed on one another are measured. Then, the color densities of the color-component of cyan, magenta, and yellow at the area (color-densities of each color component shown in
FIG. 13B
) are measured. Ink supply volumes of the color inks are then respectively adjusted in accordance with values obtained by deducting an ink supply volume representing the predetermined amount of color-impurity (predetermined values) of each of the color inks from the original ink supply volume.
During printing procedures, however, ink on the plate cylinder
45
shown in
FIG. 12
, which is not yet dried, could undesirably be mixed with an ink different in color stored in the ink fountain
50
as a result of transferring the ink through rollers belonging to the ink roller group
53
in a reverse manner. In that case, the amounts of color-impurities vary with time during the printing procedures.
In the conventional method and
Ejiri Yukio
Ikeda Hideki
Sugimoto Hiroshi
Eickholt Eugene
Merchant & Gould P.C.
Ryobi Ltd.
LandOfFree
Ink supply control device for printing machines and a method... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Ink supply control device for printing machines and a method..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ink supply control device for printing machines and a method... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2837006