JPS605472B2 - Ink density control method and device for lithographic printing press - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for automatically controlling ink density in a lithographic printing press.

[Prior art] In planographic printing, dampening water is usually supplied to the printing plate where there are printed areas and non-printed areas, and the dampening water is applied to the non-printed areas. After preventing ink from adhering to non-image areas, ink is supplied to the print using an ink roll, and the ink is applied only to the image areas before being transferred to the printed matter.

However, even if the ink film thickness on the ink roll is constant, the state of ink adhesion to the plate surface varies depending on the amount of dampening water (hereinafter referred to as water amount) on the plate surface, and accordingly, depending on the amount of ink and water. The ink density on the fixed plate surface also changes,
The amount of ink transferred to the printed matter increases or decreases, and the ink density on the surface of the printed matter changes.

In other words, the ink density on the printing plate (hereinafter referred to as the printing plate ink density)
is determined by the amount of ink corresponding to the thickness of the ink film on the plate (hereinafter referred to as plate surface ink amount) and the amount of water corresponding to the thickness of the dampening water film on the plate (hereinafter referred to as surface water amount). If the amount of water on the printing plate is large, the ink concentration on the printing plate becomes small.If the ink components are constant, the ink density on the printing plate is expressed by the following equation.

Printing ink density: (printed version) f3----
-{・'ta), f,, f2, sweep function Also, the amount of ink transferred to the surface of the printed matter (hereinafter referred to as the amount of transferred ink) is
There is a relationship that the larger the print ink density is, the larger the print ink density is, and the lower the print ink density is, the smaller the transfer ink amount is.
There is a relationship in which the transfer ink concentration (transfer ink density) becomes large, and the smaller the amount of transfer ink, the smaller the transfer ink density.As a result, the transfer ink density becomes larger when the printing ink density is large, and becomes smaller when the print ink density is small. , is expressed by the following equation.

Transfer ink density = plate ink density L = (plate weight day) F-----■ta), shi, L
' is a function, and F=f3・ne.

In this way, the amount of water has a large effect on the transferred ink concentration of printed matter, so managing the amount of water is very important, but it is difficult to manage because the amount of water is easily influenced by various external conditions and changes easily. I'm making it a thing. As a countermeasure to this problem, methods have been tried in the past, such as detecting the amount of water on the surface of the printing plate and ink roll, or detecting the humidity in the vicinity, and keeping the amount of water constant and the concentration of transferred ink constant. .

That is, for example, in the means disclosed in Mochiseki Sumi No. 49-14211, the amount of ink and water on the printing plate are individually detected by a phototube through an optical filter, and the amount of ink and dampening liquid supplied is determined. It is supposed to be controlled. [Problem to be solved by the invention] However, it is very difficult to accurately detect the amount of water, and conventional methods have not yielded satisfactory results. The means disclosed in the publication requires separate optical filters for detecting the amount of ink and the amount of water, and requires the use of a rotating filter disk, resulting in an expensive and complicated configuration. The situation is uncertain, creating problems that prevent us from fully achieving our goals.

[Means to solve the problem]

The present invention was made in view of this problem, and based on the above phenomenon, the ink density of the printing plate or printed matter is detected as an electrical signal, the detected value indicating a good printing condition is memorized, and this and subsequent The detected value is compared with the detected value to determine the change in ink concentration on the target surface, and the water supply amount is adjusted accordingly.

[Effect]

Therefore, the amount of water supplied is adjusted so that the detected value of a good printing condition and the subsequent detected values match, and the ink density on the target surface of the printing plate or printed matter is maintained based on the good printing condition, and The amount of ink and water on the printing plate match the standard condition, and accordingly, the ink thickness and dampening water film thickness on the printing plate also match the standard condition and become almost constant, and the ink density of the printed matter matches the standard value. automatically controlled in the direction of

〔Example〕

Embodiments of the present invention shown in the drawings will be described below.

FIG. 1 is a block diagram of a control circuit, in which a density detector a detects the ink density on the surface of a printing plate or printed matter, generates an electrical signal, and sends it to a correction circuit c.

At this time, only the signal of a specific portion of the target surface is sent from the synchronizing circuit b' to the integrating circuit k, and its timing is extracted according to the rotation of the printing press i. Next, the detection value from the target surface of a certain length determined by the timing is integrated by the integrating circuit k and a signal is sent to the correction circuit c. The correction circuit c corrects a change in the detected value due to a change in the detection time based on a change in the rotational speed of the printing press i. The conversion circuit d converts the incoming analog signal into a digital signal to facilitate subsequent processing. Next, the signal is sent to either the storage circuit f or the comparison circuit g by the switch e. However, while the signal is being sent to the memory circuit f, the comparator circuit g does not perform any comparison, and the memory circuit f continues to update the stored value one by one until the switch e is switched to the comparator circuit g. The stored value is fixed at , and the next signal is sent to the comparison circuit g.

Then, the signal of the stored value is also entered here, and both signals are compared.The change in ink concentration is determined based on the comparison result, and a signal is output that indicates how much the amount of water supply should be increased or decreased. The output circuit h outputs commands to the water supply amount adjusting devices of various water supply devices. Furthermore, if a very large difference is found as a result of the comparison, a warning device j is activated to notify that a defective printed matter has occurred. Note that the concentration detector a shown in FIG.
One or several monitor image areas 2a, 2b are created in a part of the monitor image areas 2a, 2b or the printed matter 1' printed by the monitor image areas 2a, 2b can be monitored. -Pictures 2a', 2 injuries, concentration detectors 3a, 3b
Or, set the head facing the target surface so as to pass through the front surfaces of 3a' and 3b'.

Then, when the monitor image area 2a, 2b or the monitor picture frame 2a', 2b' comes to the front of the respective detector 3a, 3b or 3a', 3b', the detected ink density signal is detected by the correction circuit c. The timing of the signal given from the printing press i to the synchronization circuit b is set so that detect it and integrate it with the integrator circuit k'
The signal is integrated using a trowel and the resulting signal is sent to a correction circuit c.

In addition, the output circuit h' is designed to send a command signal to the water supply amount adjusting device of the water supply device by changes in voltage, current, or the number of pulse signals, and examples of its application to various water supply devices will be described below. Shown in FIGS. 4 to 8. Fig. 4 shows an application example for a transfer roll type water supply device, Fig. 5 shows an application example for a brush type water supply device, and Fig. 6 shows an application example for a contact surface speed difference control type water supply device. All three devices supply water from the output circuit h. A command signal is sent to the amount adjusting device 5, and the rotational speed of the water source motor 6 is changed to increase or decrease the amount of water supplied.

FIG. 7 shows an example of application to a water supply device using ultrasonic waves, in which a command signal is sent from the output circuit h to the water supply amount adjusting device 7 to change the amount of mist 8 generated.

FIG. 8 shows an example of application to a spray type water supply device, in which a command signal is sent from the output circuit h to the water base adjustment device 9 to change the amount of water coming out of the nozzle 10. Next, the operation status of the above-mentioned apparatus according to the present invention will be described as follows. The operator first sets the ink supply amount according to the picture to be printed.

Next, while performing trial printing, the timing of the synchronization circuit b is adjusted, and then the water supply amount is adjusted. Since the OFF switch e is connected to the memory circuit f at this time, the memory value is updated every time the printing operation is performed.

When the water supply amount adjustment is completed and good printed matter is produced, the changeover switch e is connected to the comparison circuit g. This completes the operator's operation, and the ink density for a good printing condition is stored in the memory circuit f. From now on, the plate surface ink density or the transferred ink density is controlled based on this stored value, and as a result, the transferred ink density is The concentration is automatically controlled to a good condition. That is, the density detector a in FIG. 1 detects the plate surface ink density or the transferred ink density according to the formula {2), and each detected value of a good printing condition is designated as D,,D2, and the corresponding values are When the detected value is d,,d2, the memory circuit f stores D,
Or D2 is stored, and D,=d due to the action of the comparison circuit g.
, or D2= Since the m-type plate surface water amount is controlled in the original direction, the ink film thickness and dampening water film thickness on the plate surface are almost constant, matching the values in a good state, and in any case Also, the transfer ink density is maintained at a good level.

As described above, by applying the present invention, the management of the amount of water supply, which is the most difficult problem in lithographic printing, becomes extremely easy with a simple configuration, and the burden on the operator is reduced.

Moreover, once the settings are made, the printing is automatically controlled to approximate one standard printed matter, and there are no individual differences, and the quality of the printed matter is always constant.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing a water supply amount control circuit showing an embodiment of the present invention, Fig. 2 is a perspective view showing an embodiment of the concentration detection section, and Fig. 3 shows another embodiment of the concentration detection section. Perspective view, 4th
Figures 8 to 8 show examples of water supply devices, in which Figure 4 is a transfer roll type water supply device, Figure 5 is a brush type water supply device, Figure 6 is a contact surface speed difference control type water supply device, and Figure 7 is a Ultrasonic Water Supply Device, FIG. 8 is a schematic diagram of a spray type water supply device. a...Concentration detector, b...Synchronization circuit, c...Correction circuit, d...Conversion circuit, e...Cut-off switch, f...
Memory circuit, g...Comparison circuit, h...Output circuit, i...Printing machine, i...Warning device, k...Integrator circuit, so...Water supply amount adjustment device, 1...Plate surface, 1'.・Printed matter, 1/2a
, 2b... Monitor drawing area, 2a', 2b'... Monitor picture frame, 3a, 3b, 3, 3b'... Concentration detector, 5, 7, 9... Water supply amount adjustment device, 6... - Water motor, 8...mist, 10...nozzle, 11, 11'...picture.
Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8

Claims (1)

[Scope of Claims] 1. Detecting the ink density of the printing plate or printed matter as an electrical signal, storing the detected value from the above-mentioned detection of a good printing condition, and comparing this stored detected value with the detected value from the above-mentioned detection thereafter. and determines a change in the ink concentration, and when the ink concentration is high, the water supply amount is automatically increased, and when the ink concentration is low, the water supply amount is automatically decreased. Ink density control method for lithographic printing presses. 2. A density detector that detects the ink density of a printing plate or printed matter as an electrical signal, a memory circuit that stores the detected value by the detector in good printing condition, and a detection value stored by this memory circuit and a subsequent detection value by the detector. It has a control circuit that includes a comparison circuit that compares the detected value with a detection value and outputs a command signal to adjust the water supply amount according to the comparison output of the comparison circuit, and an adjustment device that adjusts the water supply amount in response to the adjustment command. This is an ink density control device for a lithographic printing press. 3. The ink density control device for a lithographic printing press according to claim 2, characterized in that the control circuit includes a circuit for extracting a detected value of the ink density of a specific portion of the printing plate or printed matter. 4. The ink density control device for a lithographic printing press according to claim 2, further comprising a circuit for integrating a detected value of ink density in the control circuit. 5. The ink density control device for a lithographic printing press according to claim 2, wherein the control circuit includes a circuit for correcting changes in the detected ink density value due to changes in the rotational speed of the printing press. 6. The ink density control device for a lithographic printing press according to claim 2, wherein the control circuit includes a circuit for converting a detected value of ink density into a digital signal.