JPH0257037B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an apparatus for automatically controlling the concentration of additives mixed into water supply for printing.

[Prior art]

In general, printing plates are supplied with ink and moisture during printing.
Particularly in offset printing, additives such as alcohol are mixed into the water supply for the purpose of lowering the surface tension of the water supply and reducing staining of the plate.

However, the mixing status of additives is adjusted empirically, and it is difficult to maintain the mixing concentration at the optimum value, and excessive additives are consumed.
This has resulted in disadvantages such as being uneconomical.

[Summary of the invention]

The purpose of the present invention is to fundamentally solve such drawbacks of the conventional methods, and in addition to inserting a hydrometer into feed water mixed with additives, a means for controlling transmitted light is provided at the head of the hydrometer, and a means for controlling transmitted light is provided at the head of the hydrometer. A light-emitting element and a light-receiving element are provided through the hydrometer, and the output of the light-receiving element is changed by the up-and-down movement of the hydrometer, and an electric valve is driven by a control circuit that responds when this output reaches a predetermined value. The present invention provides an extremely effective additive concentration control device for printing water supply in which the concentration of additives mixed in is controlled by this electric valve.

〔Example〕

Hereinafter, details of the present invention will be explained with reference to figures showing examples.

FIG. 1 is a block diagram showing the water supply system of a printing press. In order to keep printing conditions constant, water supply 2 in a water tank 1 maintained at a predetermined temperature is supplied to a water tank 4 and a water tank 1 by a pump P and a water supply pipe 3. Water is supplied to the detection tank 5, and in the water tank 4, a water supply roller (not shown) supplies moisture to the plate cylinder on which the plate is mounted, and excess water is returned to the water tank 1 via the drain pipe 6. In the detection tank 5, for the water supply 2 supplied through the water volume adjustment pot V,
Alcohol supplied from the alcohol tank 7 in response to the opening of the solenoid valve SV is mixed in, and when the water level reaches a certain level or higher, it is discharged to the water tank 1 via the drain pipe 8.

In addition, a hydrometer 10 is placed in the water supply 2 of the detection tank 5, and is supported by a guide 9 fixed to a drain pipe 8 so as to be able to float and sink. If the hydrometer 10 increases, it will sink. Therefore, for the purpose of detecting this floating motion, a transmitted light control means 11 (described later) is applied to the tip of the head of the hydrometer 10.
is provided, and the light emitting element PS is connected via this.
and photodetector PR are provided facing each other,
These are supported by an arm 12 fixed to the detection tank 5.

The hydrometer 10 and the guide 9 have a vertical continuous protrusion 10a formed on the outside of the main body of the hydrometer 10, as shown in FIG. A corresponding groove 9a is formed inside the guide 9, which prevents horizontal rotation of the hydrometer 10.

FIG. 3 is an enlarged sectional view showing the head of the hydrometer 10. In order to change the transmittance of light rays along the vertical direction, a translucent material such as colored glass is used as a transparent material 21 such as transparent glass. 22 is fixed with its occupied cross-sectional area gradually increasing from the tip downward, and these constitute the transmitted light control means 11, which projects a light beam from the light emitting element PS from the direction of the dotted line, and also controls the transmitted light. When the transmitted light is received by the light receiving element PR on the opposite side of the means 11, the output of the light receiving element PR changes according to the ups and downs of the hydrometer 10, and the concentration of alcohol mixed in can be detected based on this.

By adding the transmitted light control means 11 to the hydrometer 10, the hydrometer 10 can be adjusted according to the weight of the transmitted light control means 11.
This requires a large air chamber volume, and the hydrometer 10 becomes larger, and the width of floating and sinking movements for the same change in specific gravity becomes large. The diameter is approximately 2 mm, improving detection accuracy.

FIG. 4 is a circuit diagram of the control circuit, in which the output of the light receiving element PR is inverted and amplified by the amplifier circuit A consisting of the differential amplifier DA ₁ and the resistors R ₁ to R ₃ , and the output of the light receiving element _PR is inverted and amplified. Comparison circuit consisting of R ₄ to R ₆
It is applied to CP and compared with the reference voltage obtained by dividing the power supply voltage E with the potentiometer VR, and the hydrometer 1
0 floats up and the output of the photodetector PR drops to a predetermined value, the output voltage of the amplifier circuit A increases accordingly, and if it becomes equal to or higher than the reference voltage, the output of the comparator circuit CP changes to positive polarity, and the resistor Transistor Q is turned on via _R7 to produce a drive output.

Then, current passes through the solenoid of solenoid valve SV,
The solenoid valve SV is driven and opened to start supplying alcohol, so the hydrometer 1
0 sinks, and due to the hysteresis characteristic of the comparator circuit CP provided by the positive feedback by the resistor _R6 , when the output of the circuit CP sinks to a state where the polarity becomes negative, the transistor Q returns to OFF, solenoid valve
SV is restored and stops supplying alcohol.

If a dial is provided on the knob of the potentiometer VR and the indicated value is calibrated based on the concentration of alcohol mixed in, the concentration of mixed alcohol can be set accurately and easily.

Further, the mixing status of alcohol in the water supply 2 is set by the degree of opening of the pot V.

Therefore, if the concentration of alcohol mixed in the feed water 2 circulating between the water tank 1 and the detection tank 5 decreases, alcohol will be automatically supplied, and once the supply has started, some amount of alcohol will be added to the hydrometer 10. Even if there is ups and downs, this is ignored due to the hysteresis characteristics of the comparator circuit CP, and the concentration of alcohol mixed in the feed water 2 is stably and accurately maintained within a predetermined range, so that the printing situation is always maintained in a suitable state. .

Further, the concentration of alcohol mixed in is indicated by the dial of the potentiometer VR, and can be finely adjusted using this as a reference, making it easy and accurate to set the mixed concentration.

However, the transmitted light control means 11 may roughen the transparent material 21 unevenly in the vertical direction as a translucent material 22, or mix an opaque material such as opaque powder into the transparent material 21. well or the same means 1
1 may be made separately and fixed, and an opaque material in which a slit whose width changes in the vertical direction is formed, a triangular opaque material, or the like can also be used as the means 11.

In addition, the control circuit can be selected arbitrarily as long as it has the same function, and instead of the solenoid valve SV,
A motor valve or the like may be used as an electric valve, and
The additive may be selected from not only alcohol but also alcohol substitute liquid, etching liquid, etc. depending on the situation, and various modifications are possible.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, with a simple configuration, the additive concentration of printing water supply water is stably and accurately maintained within a predetermined range, and the printing condition is always maintained in an appropriate state. Excess consumption of additives is prevented, cost savings are achieved, and significant effects are achieved in controlling additive concentrations in various printing water supplies.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, Fig. 1 is a configuration diagram showing a water supply device of a printing press, Fig. 2 is an X-Y sectional view of Fig. 1, and Fig. 3 is an enlarged view showing the head of a hydrometer. The top view and FIG. 4 are circuit diagrams of the control circuit. 1...Water tank, 2...Water supply, 5...Detection tank, 7...
... Alcohol tank, 9 ... Guide, 10 ... Hydrometer, 11 ... Transmitted light control means, PS ... Light emitting element,
RR... Light receiving element, SV... Solenoid valve (motorized valve), A
...amplifier circuit, CP...comparison circuit, Q...transistor.

Claims (1)

[Claims] 1. A hydrometer that is floatable and sinkable in printing water mixed with additives, and a transmitted light control means that changes the transmittance of light rays along the vertical direction, which is provided at the head of the hydrometer. a light-emitting element and a light-receiving element arranged opposite to each other via the transmitted light control means; a control circuit that generates a driving output when the output of the light-receiving element reaches a predetermined value; and a control circuit that is driven by the driving output. An additive concentration control device for printing water supply, comprising: an electric valve for controlling the concentration of the additive mixed in.