Photography – Fluid-treating apparatus – Having testing – calibration – or indicating
Reexamination Certificate
2001-01-31
2002-04-02
Rutledge, D. (Department: 2851)
Photography
Fluid-treating apparatus
Having testing, calibration, or indicating
C396S626000
Reexamination Certificate
active
06364544
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an automatic developing apparatus for a photosensitive lithographic printing plate and to a method of replenishing a replenisher for developer for the apparatuses, and, in particular, to such a method as to minimize the fluctuation of developer sensitivity due to changes in developing conditions.
2. Description of the Related Art
In general, as a representative method of controlling the developer sensitivity in an automatic developing apparatus for photosensitive lithographic printing plates, there is adopted a method replenishing a replenisher for developer (hereinafter, just referred to as “replenisher”) with time and processing, which replenishes the replenisher with time to a developer tank that a developer is stored, measures the plate area of the processed plates, and replenishes an amount of the replenisher corresponding to the measured value (hereinafter, referred to as “plate area-based replenishing method”).
However, the plate area-based replenishing method requires a device for measuring a plate area of the lithographic plate in a developing part of the automatic developing apparatus, thus causing the structure of the developing apparatus complicated and expensive.
Further, it is difficult to judge whether a single surface or the both surfaces of the lithographic plate are processed, (hereinafter, referred to as “single surface/dual surface”.) and the type of plate (note that there are various kinds of plates differing in coated amount of the photosensitive layer). Thus, in case that the appropriate replenisher amount will change depending on the plate area, the single surface/dual surface, and the type of plate, there is a problem that it makes difficult to appropriately replenish the replenisher.
On the other hand, there is conventionally disclosed in JP-A-64-21451 (the term “JP-A” as used herein means a Japanese Patent Unexamined Publication), a method replenishing the replenisher for an automatic developing apparatus for photosensitive lithographic printing plates, which measures the electric conductivity of the developer, compares the measured value with the calculated value that has been experimentally determined for the optimum sensitivity, and replenishes the replenisher in the case where the measured value is smaller than the calculated value. (Hereinafter, this method will be referred to as “conductivity-based replenishing method”.)
The conductivity-based replenishing method can replenish the appropriate amount of the replenisher and can appropriately keep the developer sensitivity, even with the changes in plate area, single surface/dual surface, or type of lithographic plate to be processed.
However, it should be noted that the developer conductivity is affected (rises) by natural evaporation of water from the developer. Accordingly, when natural evaporation of water is promoted due to the affect of the installed conditions of the automatic developing apparatus or the like, an appropriate replenishing amount of the replenisher will be changed.
The aforementioned conductivity-based replenishing method cannot deal with the changes of the appropriate replenishing amount of the replenisher due to the natural evaporation of water. Thus, when the natural evaporation of water is increased, the appropriate replenishment is not realized, thus failing in keeping the developer sensitivity appropriately.
Moreover, the electric conductivity of the developer exhausted by carbon dioxide absorbed in elapsed time differs from that of the one exhausted by plate processing when the sensitivity of the two are recovered to their proper values. For example, a silicate-type processing agent exhibits 65 mS/cm when recovered from CO
2
fatigue in contrast to 55 mS/cm when recovered from plate processing, and a non-silicate-type processing agent exhibits 56 mS/cm when recovered from CO
2
fatigue in contrast to 39 mS/cm when recovered from plate processing. Therefore, if the frequency of processing, e.g., the processed amount per day changes, the electric conductivity for its optimal sensitivity tends to shift from the reference conductivity value set up in advance, thus it becomes impossible to keep the developer sensitivity appropriately.
SUMMARY OF THE INVENTION
By taking into account those situations described above, the object of the present invention is to provide an automatic developing apparatus and a method of replenishing the replenisher for said apparatuses, which can minimize the fluctuation of developing sensitivity against the changes in developing conditions, while using an economic and simple developing unit of the automatic developing apparatus, to thereby perform a stable development.
The purpose of the present invention can be achieved with the following apparatuses and methods.
(1) An automatic developing apparatus for photosensitive materials, includes:
a developer tank storing a developer;
a replenishing unit replenishing a predetermined amount of a replenisher for developer to maintain a developing activity of the developer in the developer tank;
a memory for memorizing a first preset replenishing condition of the replenisher to compensate the reduction of the developing activity during working and/or stopped period, and a second preset replenishing condition of the replenisher to compensate the reduction of developing activity caused by the processing of the photosensitive materials;
a calculating unit calculating a replenisher replacement ratio being a ratio that a charged solution of the developer is replaced by at least one of the replenisher and a diluent replenished for reducing an electric conductivity of the developer;
an electric conductivity sensor measuring the electric conductivity of the developer; and
a diluent replenishing unit replenishing the diluent to the developer tank until the electric conductivity becomes lower than an electric conductivity target value previously calculated from the replenisher replacement ratio, when the measured value of electric conductivity exceeds the target value.
(2) The automatic developing apparatus according to (1), wherein the electric conductivity target value is calculated from the replenisher replacement ratio, and one of the following values:
a) a dilution ratio of the sum of a diluent for diluting the replenisher and the diluent replenished for lowering the electric conductivity of the developer in the developer tank, relative to the replenisher, and
b) a ratio of the integral amount of the replenisher which is replenished to compensate the reduction of the developing activity during working and/or stopping period, relative to the product of the replenisher replacement ratio with the amount of the developer.
(3) The automatic developing apparatus according to (1), wherein at least one of the developer tank and the automatic developing apparatus is structured to suppress air ventilation so that the CO
2
concentration of the air in a direct contact with the developer in the developer tank is kept below 300 ppm.
(4) A method of replenishing a replenisher for a developer in an automatic developing apparatus for photosensitive materials, includes the steps of:
a) replenishing a replenisher for developer based on a first predetermined replenishing condition so as to compensate the reduction of a developing activity during working and/or stopped period;
b) replenishing the replenisher based on a second predetermined replenishing condition so as to compensate the reduction of the developing activity caused by the processing of the photosensitive materials;
c) measuring an electric conductivity of the developer replenished with the replenisher in the steps a) and b); and
d) replenishing a diluent into the developer until the electric conductivity of the developer falls below an electric conductivity target value predetermined by using a replenisher replacement ratio, when the measured value of the electric conductivity of the developer exceeds the target value.
(5) The method according to (4), wherein the electric conducti
Oishi Chikashi
Sasayama Hiroyuki
Fuji Photo Film Co., LTD
Rutledge D.
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