Ryobi Limited

Masaki Shiki

Hideki Ikeda

In an apparatus for controlling the amount of ink to be supplied to a printing plate mounted on a printing cylinder, which ink is reserved in an ink fountain and transferred by an ink transfer roller to the printing plate via plural ink rollers, where an average value of image area ratios is not less than a given value, a normal mode is selected so as to preset, prior to starting printing operation, each of the opening degrees of the plural ink fountain keys based on a main conversion curve and the number of times at which the ink transfer roller touches the ink fountain roller per a given number of rotations of the plate cylinder to a given touching frequency, and where the average value is less than the given value, a small image mode is selected so as to preset, prior to starting printing operation, each of the opening degrees of the plural ink fountain keys based on a modified conversion curve and the number of times at which the ink transfer roller touches the ink fountain roller to a touching frequency lower than the given touching frequency of the normal mode. The modified conversion curve allows the increasing rate of the opening degree of each of the plural ink fountain keys relative to the increase of the image area ratio of a corresponding zone to be higher than the increasing rate of the main conversion curve of the normal mode.

Apparatus for controlling the amount of ink in a printing press

An apparatus for controlling ink supply by varying the opening degree of an ink fountain key according to a measured density of a printed matter includes a control means for determining a reference correction value of the opening degree of the ink fountain key according to a density difference between a target density of the printed matter or a reference density and a measured density, and determining a correction value by multiplying the reference correction value by a coefficient having a value of more than 1. The control means controls the ink fountain key according to the correction value of the opening degree of the ink fountain key until the number of sheets printed from the start of the printing exceeds a predetermined number, and controls the ink fountain key according to the reference correction value after the number of sheets printed exceeds the predetermined number.

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Fuchu, Japan

Masaki Shiki