JPH0642171B2 - Concentration control device for alcohol aqueous solution - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlling the alcohol concentration of water containing alcohol, and more particularly to a device for controlling the concentration of an aqueous alcohol solution suitable for an alcohol dampening system in offset printing. .

[Background of the Invention]

As is well known, it is necessary to apply dampening water to the plate surface in offset printing. As a device for supplying the dampening water to the plate surface, that is, a dampening water device, a so-called Molton system using a molton as a watering roller for the plate surface has been widely used.

However, in recent years, the so-called alcohol dampening system, which does not use a Molton roller to supply water to the printing plate, is an alternative to the Molton method described above because it is easy to maintain stable image quality and is easy to operate and maintain. It has become widespread.

FIG. 16 shows an example of this alcohol dampening system. In this figure, reference numeral 1 is a dampening water tank, which is generally equipped with a constant temperature device and stores 15
The temperature is kept at about ℃. The dampening water in the tank 1 is pumped up by the pump 2 and sent to the water boat 3 of the printing machine. In the water boat 3, a part of the roller group 4 of the dampening water device is provided. It is soaked in dampening water. Therefore, the dampening water in the water boat 3 is fed to the roller group 4
And is supplied to the surface of the plate 6 wound around the plate cylinder 5.

On the other hand, the dampening water excessively supplied into the water boat 3 is returned to the dampening water tank 1 via the return pipe 7.

By the way, in this alcohol dampening system,
Since the roller for watering the plate surface itself does not have strong water retention like the Molton roller, in order to supply sufficient dampening water to the plate surface, a surfactant such as alcohol is added to the dampening water, It is said that it is necessary to reduce the surface tension so that water can be easily dispersed in the ink.

Here, the most commonly used surfactant is isopropyl alcohol among alcohols, and the alcohol concentration in the dampening water at this time is usually 5% to 20%. To some extent, this change in alcohol concentration has a very large effect on the amount of water supplied to the inking device and the plate, and also on the quality of the printed matter.

Therefore, in such an alcohol dampening system, maintaining the alcohol concentration in the dampening water at a predetermined value is an indispensable element, and for this purpose, it is necessary to measure the alcohol concentration.

However, as such a method for measuring the alcohol concentration, conventionally, the fact that the specific gravity of alcohol is smaller than water is used, a specific gravity bottle is used to measure the specific gravity of dampening water, and a method for determining the alcohol concentration is mainly used. Was used.

In the alcohol dampening system described above, the dampening water is usually pumped to the water boat on the printing press.
Since the dampening water is circulated between the tanks, there are many fine bubbles in the dampening water, which adhere to the specific gravity bottle, making accurate concentration measurement difficult. Further, the adhesion of ink or dirt in the dampening water to the specific gravity bottle also causes a measurement error and necessitates frequent cleaning, which makes the handling complicated.

[Object of the Invention]

The present invention has been made under the background described above, and an object thereof is that the alcohol concentration of an aqueous solution containing alcohol is influenced by dirt caused by bubbles or ink mixed in the aqueous solution. In other words, it is an object of the present invention to provide a concentration control device for an aqueous alcohol solution, which enables measurement with sufficient accuracy.

[Outline of Invention]

In order to achieve this object, the present invention detects the concentration of alcohol gas in the space in contact with the aqueous alcohol solution, measures the alcohol concentration of the aqueous alcohol solution based on this alcohol gas concentration, the alcohol concentration from this measurement result. Is characterized in that it is controlled.

Example of Invention

Hereinafter, a concentration control device for an alcohol aqueous solution according to the present invention will be described in detail with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of the present invention applied to an alcohol dampening system of an offset printing machine. In FIG. 1, 8 is an alcohol concentration measuring unit, which is sent from a pump 2 toward a water boat 3. A part of the dampening water is collected through the bypass pipe 9, and after measurement, is returned to the dampening water tank 1 through the pipe 10.

A control unit 11 calculates the alcohol concentration from the gas concentration signal and the signal representing the water temperature from the measuring unit 8. When the measured alcohol concentration is lower than the set concentration, the solenoid valve 12 is opened and the dampening water tank is opened. Serves to supply alcohol in one.

FIG. 2 is an enlarged cross-sectional view of the measuring section 8. When the dampening water collected through the bypass pipe 9 enters the measuring section 8, the dampening water passes under the shed plate 13. The shim plate 13 functions to prevent waves from being generated on the water surface in the measuring section 8. The return pipe 10 is formed so as to extend into the measuring section 8, and the excess dampening water is returned to the dampening water tank 1 while always keeping the height of the water surface in the measuring section 8 constant. A temperature sensor 15 and a gas sensor 16 are attached to the lid 14 of the measuring unit 8. The sensor cap 17 has a conical shape as shown in the figure, and the lower part thereof goes below the surface of the water to form a small closed space 18. The sensor 16 is vaporized from the dampening water 19 drawn into the measuring section 8. , Functions to detect the concentration of the alcohol gas filled in the closed space 18.

The sensor 16 is a well-known catalytic combustion type gas sensor as shown in FIG. 3, and comprises a measuring element 16a and a dummy 16b as shown in FIG. 4, and a detection signal is obtained by a bridge circuit. The sensor used in the present invention is not limited to such a catalytic combustion type, and any sensor may be used as long as it exhibits a detection characteristic required for alcohol gas. For example, a semiconductor type sensor, Any sensor such as an infrared absorption type sensor, a heat conduction type sensor, or a light wave interferometer sensor may be used. Note that the sensor cap 17 is made easy to attach and detach, and can be easily replaced when there is a risk of being affected by dirt or the like.

Reference numeral 20 is an air pump for supplying air in the closed space 18 to the pipe 2
It inhales through 1 and discharges to the outside. Along with this exhaust, fresh air containing no alcohol gas is newly sucked into the sensor cap 17 via the suction pipe 22.

FIG. 5 shows a schematic flow of the operation of the entire apparatus. Hereinafter, each step will be described.

Step 1 (S-1) Ventilation in the sensor cap 17 The air pump 20 is operated to exhaust the alcohol gas in the sensor cap 17. As a result, the inside of the cover is ventilated and there is almost no alcohol gas.

Ventilation inside the cover is for the following reasons.

When the measurement is continued while the cap 17 is covered on the surface of the dampening water 19, the alcohol gas concentration in the cap quickly increases in response to the change in the direction in which the alcohol concentration in the dampening water 19 increases. As a result, the sensor 16 rises and the change in alcohol concentration in the water can be quickly detected. However, with respect to the change in the direction in which the alcohol concentration in the dampening water decreases, the gas concentration in the sensor cap does not easily decrease because the high-concentration gas stays in the sensor cap 17, and the alcohol concentration in the water changes. However, the period when it is detected by the sensor as a change in the gas concentration will be delayed. Therefore, the gas in the sensor cap is once exhausted, and then the concentration of the vaporized alcohol gas is measured according to the alcohol concentration at that time.

Step 2 (S-2) Stopping the pump After ventilating for a certain period of time or until the inside of the sensor cap 17 reaches an appropriate gas concentration, the air pump 20 is stopped. At this time, the exhaust pipe 21 and the intake pipe 22 are appropriately thin and long, and after the pump is stopped, the measuring unit 8
Make sure that the inside of the sensor cap is not affected by the wind outside and the gas does not leak from the inside of the cap.

Step 3 (S-3) Measurement of gas concentration Sensor cap 17 with sufficient ventilation at steps 1 and 2
Alcohol gas is vaporized in due time, and the alcohol concentration in the dampening water at that time and a gas having a certain concentration depending on the liquid temperature of the dampening water are filled.

This constant gas concentration is measured, but in the present embodiment, the output of the sensor 16 is monitored from the time when the process of (S-2) ends, and the increase rate of the sensor output due to the increase in gas concentration is The measured value is obtained by using the sensor output when it becomes smaller than a certain level.

As another method, the sensor output after a fixed time from the end of ventilation can be used as the measured value.

Further, while this step 3 is being performed, the liquid temperature is also measured by the thermometer 15 in parallel, and the average value of the liquid temperature measurements over the entire step 3 is adopted as the liquid temperature value.

Step 4 (S-4) Calculation of alcohol concentration in dampening water In this step, the alcohol concentration in dampening water is calculated from the sensor output value and the liquid temperature value measured in Step 3. The contents of the calculation are as follows.

The relationship between the output of the sensor 16 and the alcohol concentration in the dampening water is almost linear at a constant temperature as shown in FIG. 6 (a), but when the liquid temperature changes, the sensitivity (see FIG. The slope of the straight line) changes as shown in Fig. 6 (b).

Therefore, it is easy to store the sensitivity characteristics shown in Fig. 6 (b) in advance, obtain the sensitivity from the measured liquid temperature, and if the sensitivity is obtained, obtain the alcohol concentration in the dampening water from the sensor output. is there. In addition, in this embodiment, FIG.
The relationship between the concentration and the sensor value shown in (a) is approximately calculated as a straight line. However, depending on the sensor used, the temperature may deviate from the straight line depending on the liquid temperature. Therefore, if the deviation is corrected, more accurate measurement can be performed.

The measured value obtained in this way is displayed on the digital meter 24 provided in the control unit 11 as a percentage display, which is convenient for the operator.

Step 5 (S-5) Comparison with Set Concentration In this step, the alcohol concentration in the dampening water already calculated in Step 4 is set in the digital switch 2 of the control unit 11.
3. If the measured value is lower than the set value, the solenoid valve 12 is opened, alcohol is added (step 6), and if the measured value is higher than the set value, If it is within the predetermined tolerance, do nothing.

In this embodiment, since the capacity of the dampening water tank 1 is limited, if the alcohol concentration is too high, dampening water without alcohol is added to reduce the concentration. Such control is not performed because dampening water may overflow from the tank 1. If there is no such fear, the fountain solution may be added with the alcohol-free fountain solution when the alcohol concentration of the fountain solution is too high. Since the circulating dampening water has a considerable amount, even if alcohol is added, it takes several minutes or more before the alcohol becomes uniform. Therefore, in this example, the amount of alcohol added was an amount commensurate with the difference between the measured value and the set value, and after adding alcohol once, it was detected that the alcohol concentration of the fountain solution was too low for several minutes. However, by not adding alcohol, it is designed to prevent the alcohol from being added too much.

Step 6 (S-6) Addition of alcohol In this step, the solenoid valve 12 is opened to add alcohol. As a method of addition, the necessary amount may be added at one time, or it may be added in several times for the purpose of uniformly mixing. After step 6 is completed, the process returns to step 1 and the processing is repeated.

FIG. 7 is a block diagram of the control unit 11, and FIG. 8 shows a flow chart of control calculation contents. The operation of each part will be described below using both figures.

The CPU 25 controls all the operation calculations, and the ROM 26 stores data such as sensor sensitivity and programs, and the RAM for executing programs.
27 is connected to the data bus 28.

First, in step 10, the CPU 25 sends the control signal 1 / F
The air pump 20 is operated by sending it to the (interface) 29, after counting a fixed time, the control signal is sent again to 1 / F29 and the pump is stopped (step 11).

In steps 12 and 13, the CPU 25 A / D-converts the output signal of the gas sensor 16 by the A / D converter 30 and fetches it, and calculates the change rate of the alcohol concentration.

Similarly, in steps 14 and 15, the temperature detector 15
Signal is A / D converted, fetched, and added.

In step 16, it is judged whether or not the absolute value of the gas concentration change rate at that time has become smaller than a value determined in advance by a digital switch or the like.

In Step 17, since it is possible that the gas concentration change rate does not readily converge during the process in which the alcohol solution concentration changes abruptly, the measurement is completed if the change rate does not converge within a certain time. To do so, a software timer is provided.

In step 18, the gas concentration when the gas concentration change rate is determined to be sufficiently small in step 16 is used as the gas concentration detection value.

In step 19, the temperature added in step 15 is divided by the number of additions to obtain the average temperature.

In step 20, the sensitivity at the temperature calculated in step 19 is calculated based on the sensitivity data written in the ROM 26 in advance.

In steps 21 and 22, the alcohol concentration is calculated from the sensitivity calculated in step 20 and the gas detection value stored in step 15, and is supplied to the digital display 24 via 1 / F31 to display the alcohol concentration. To do.

In step 23, the target value set by the digital switch 23 is read via 1 / F33, compared with the calculated alcohol concentration in step 21, and within the allowable range set by the high and low and digital switch 34. Or not.

In step 24, when the alcohol concentration is lower than the set value, the solenoid valve 12 is opened / closed via the 1 / F 32 a required number of times or a required time, and a required amount of alcohol is added.

By the way, as is clear from the above description, in the embodiment of FIG. 8, the content of the measuring process is as follows.

 Monitor the rate of change in sensor output over time.

The sensor output when the time rate of change becomes smaller than a predetermined value is taken as the gas concentration measurement value.

The measured temperature is the average temperature during the period when the gas is filled.

From the above gas concentration measurement value and temperature measurement value,
The temperature is corrected to calculate the alcohol concentration.

That is, after the change in the gas concentration converges to a predetermined value or less, the temperature is corrected and the alcohol concentration is calculated.

As a result, in the above-described embodiment, as shown in FIG. 9 (a), the sensor output becomes a constant value according to the gas filling, and the measurement can be performed with high accuracy when there is almost no temperature change during the measurement. Is.

However, as shown in FIG. 9 (b), for example, when the temperature is rising, the sensor output also rises along with the temperature, the rate of change in sensor output time does not easily converge, and a measurement error is likely to occur.

Therefore, as an example in the case where temperature change is likely to occur,
The following measurement process may be applied.

 The gas sensor output is first detected.

 Measure the temperature.

 Calculate the alcohol concentration from the data of.

 Calculate the rate of change of alcohol concentration over time.

Repeating the above, the measured value is the alcohol concentration value at the time when the rate of change of the alcohol concentration with time becomes smaller than a predetermined value.

According to this embodiment, as shown in FIG. 9 (c), the change rate of the alcohol concentration converges in a short time, so that the measurement can be accurately performed even when the temperature change is large.

Next, FIG. 10 shows another embodiment of the measuring unit 8 (FIG. 1) in the present invention.

In the embodiment described so far, as shown in FIG. 2, all the ventilation in the sensor cap 17 was performed by the air pump 20, but in the embodiment of FIG. 10, the solenoid valve 36 is used instead. Provide ventilation and perform the following operations.

That is, when ventilation is performed, the electromagnetic valve 36 is opened for a certain period of time in response to a signal from the control unit 11 to drop the dampening water 19 in the measuring unit into the tank 1 and sufficiently lower the water surface. When the water surface drops, a gap is formed between the lower portion of the sensor cap 17 and the water surface, so that alcohol gas having a relatively large specific gravity escapes to the outside through the gap, and ventilation is performed accordingly. At this time, considering the case where the measuring section is filled with gas, it is more effective to provide an appropriate window on the side wall of the measuring section 8 or a fan that operates only during ventilation. The configuration other than the measuring unit 8 is the same as that of the embodiment shown in FIG.

FIG. 11 shows a measuring unit in still another embodiment of the present invention.

In this embodiment, a metering air pump 37 is used, and it is constantly operated to suck fresh air containing no alcohol gas from the outside through a pipe 38 and cover it with dampening water 19 as shown in FIG. It is guided to the measurement chamber 40 through the gutter-shaped portion 39 provided, and while passing through the gutter-shaped portion 39, the concentration of alcohol gas in the air containing alcohol gas vaporized from the dampening water surface is fed to the sensor 16. It is designed to measure all the time. At this time, the suction by the pump 37 needs to be reduced for a sufficient time necessary for detecting the alcohol concentration from the air in the measurement chamber 40 such that the same air remains in the measurement chamber 40. Further, the size of the trough-shaped portion 39 is long enough so that the air passing through the trough-shaped portion 39 is sufficiently filled with alcohol gas in accordance with the suction amount of the air pump 37. In order to be detected by the sensor 16 quickly, it is necessary to make the length as short as possible, and accordingly, it is necessary to set the dimensions in consideration of these.

Therefore, according to the embodiment of FIG. 11, it is possible to continuously measure the alcohol concentration, not the intermittent measurement by the intermittent ventilation as in the embodiments explained so far. Even in the case of this embodiment, it is needless to say that in order to make the air volume in the trough-shaped portion 39 constant, a device for keeping the liquid surface constant as in the embodiment of FIG. 2 is necessary. Therefore, therefore, the configuration therefor, the procedure for calculating the alcohol concentration from the output of the sensor 16 and the measurement value of the thermometer 15, and the other device configuration are similar to those of the above-described embodiment.

Next, as an embodiment of the present invention related to the embodiment of FIG. 10, an embodiment in which the sensor cap 17 is moved up and down instead of lowering the surface of the dampening water 19 is shown in FIG.
That is, in this embodiment, the sensor cap 17 is constructed so that it can be moved up and down by an appropriate actuator such as a solenoid, an air cylinder, a motor, etc., so that at the time of measurement, the sensor cap 1 can be moved as shown in FIG. 13 (a).
Keep the bottom of 7 below the surface of the dampening water 19,
When performing ventilation, the sensor cap 17 is lifted as shown in FIG. 3B so that the lower part of the sensor cap 17 moves away from the surface of the dampening water 19.

As already described in the embodiment of FIG. 10, the specific gravity of alcohol gas is larger than that of air. Therefore, if the sensor cap 17 is lifted as shown in FIG. The gas-containing air will flow away to the outside as indicated by the arrow, thus providing ventilation.

FIG. 14 is also an embodiment for ventilating the inside of the sensor cap 17. In this embodiment, the sensor cap 17 is provided with a window 41 which is opened and closed by an actuator such as a solenoid, and the window 41 is opened during ventilation. Is.

Further, FIG. 15 shows an embodiment in which another ventilation method is adopted, in which the ventilation air is sent in the form of bubbles from the dampening water 19 into the space 18 of the sensor cap 17. The air for this is supplied by the air supply pipe 42, and the air in the sensor cap 17 is the ventilation pipe 4
It is pushed out from 3 and escapes to the outside. Therefore, ventilation can be performed by sending air from the pipe 42 at every predetermined timing.

In the embodiment shown in FIG. 2, the air in the sensor cap 17 is sucked by the air pump 20 to perform ventilation, but instead of this, the air may be sent into the sensor cap by the pump. Good. This also applies to the embodiment shown in FIG.
It is also possible to connect 7 to the pipe 38, so that the outside air is sent into the measuring chamber 40 via the gutter-shaped portion 37.

By the way, in the above-mentioned embodiments, the structure centering on the micro computer is used as the control system, but in the present invention, the analog circuit may perform the same function. In particular, if the dampening water in the dampening water tank 1 is configured to accurately maintain a predetermined constant temperature, there is no need to measure the temperature and correct it, and directly from the sensor output.
Since the alcohol concentration in the dampening water can be measured, a thermometer is not required and the structure can be simplified.

Further, when there are a plurality of measuring units 8, one control unit 11 may be provided in common for these measuring units. According to the embodiment thus configured, the configuration is further simplified. It is possible and helps to reduce costs.

Needless to say, the present invention is applicable not only to the above-mentioned alcohols and isopropyl alcohols but also to various water-soluble solvents such as methanol and ethanol.

〔The invention's effect〕

As described above, according to the present invention, since the alcohol concentration in the alcohol aqueous solution can be accurately detected by a known gas sensor, it is possible to obtain a good printing result by using it in an alcohol dampening system or the like in offset printing. It is possible to easily provide a useful concentration control device for an aqueous alcohol solution.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment in which the present invention is applied to an alcohol dampening system for offset printing, FIG. 2 is an explanatory view showing an embodiment of a measuring unit, and FIG. 3 is an external view showing an example of a sensor. FIG. 4 is a circuit diagram showing an example of a measuring circuit, FIG. 5 is a flow chart showing a measuring operation process in an embodiment of the present invention, and FIG. 6 is a characteristic diagram for explaining the operating principle of the present invention. FIG. 7 is a block diagram of an embodiment of a control unit, FIG. 8 is a flow chart showing an embodiment of a measurement process by the control unit, and FIG. 9 is a characteristic diagram showing an example of operation in the embodiment of the present invention. 10 is a block diagram showing another embodiment of the measuring unit in the present invention, FIG. 11 is a block diagram showing another embodiment of the same, and FIG. 12 is a line AA ′ in FIG. Sectional view, Fig. 13, Fig. 14, Fig. 1
FIG. 5 is an explanatory diagram showing a modified embodiment of the present invention, respectively.
FIG. 6 is a block diagram showing an example of a conventional alcohol dampening system. 1 ... Damping water tank, 2 ... Pump, 3 ... Water boat, 4 ...
... Roller group, 5 ... Plate cylinder, 6 ... Plate, 7 ... Return pipe, 8 ... Alcohol concentration measuring unit, 9 ... Bypass pipe, 10 ... Pipe, 11 ... Control unit, 12 ... Electromagnetic Valve, 13 ... Shroud plate, 14 ... Lid, 15 ... Thermometer, 16 ... Gas sensor, 17 ... Sensor cap, 18 ... Closed space, 19 ... Dampening water, 20 ... Air pump , 21 ... pipe, 22 ... suction pipe, 23 ...
… Digital switch, 24… Digital meter.

Claims (6)

[Claims] 1. A concentration control device for an alcohol aqueous solution, wherein the alcohol concentration of an alcohol aqueous solution is controlled to a predetermined value by independently supplying alcohol and water to a predetermined container. Detecting means for detecting the alcohol gas concentration in a predetermined space including the interface with the aqueous solution, and arithmetic means for outputting a signal representing the alcohol concentration of the alcohol aqueous solution based on the detection result by the detecting means are provided. A concentration control device for an alcohol aqueous solution, characterized in that the concentration of the alcohol in the alcohol aqueous solution is controlled by controlling the supply of at least one of the alcohol and water by a signal indicating the concentration. 2. The concentration control apparatus for an aqueous alcohol solution according to claim 1, wherein the arithmetic means is configured to include a correction process based on the temperature of the aqueous alcohol solution. 3. A concentration control device for an aqueous alcohol solution according to claim 1, wherein the air is kept substantially in the space. 4. The structure according to claim 3, wherein the predetermined space is repeatedly and intermittently ventilated, and the detection means detects the alcohol gas concentration intermittently between ventilations. An apparatus for controlling the concentration of an aqueous alcohol solution, which is characterized in that 5. The apparatus according to claim 1, wherein the predetermined space is kept in a continuous open air circulation state, and the alcohol concentration is continuously detected by the detecting means. A concentration control device for an aqueous alcohol solution, which is characterized by: 6. The volume and the distance between the detection means and the liquid surface of the predetermined space are kept constant by keeping the liquid surface height of the alcohol aqueous solution constant therein. An apparatus for controlling the concentration of an aqueous alcohol solution, which is configured to be kept constant.