JP4602582B2 - Screen printing machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a screen printer, and more particularly to a screen printer having a configuration for detecting the amount of ink used during printing.
[0002]
[Prior art]
Conventionally, when screen printing is performed on a label of an optical disc such as a CD, ink is supplied to the screen by a manual method such as tilting an ink bottle and dropping a predetermined amount on the screen printing plate. When the viscosity of the ink is high and natural dripping is not possible, the viscosity is lowered by stirring with a stirrer in advance, or the viscosity is lowered by stirring the ink in the bottle with a spatula or the like.
[0003]
However, the method of manually supplying ink has poor workability and low production efficiency, and often causes accidents such as running out of ink, forcing the operation of the printing press to be stopped. When the operation of the printing press is stopped, there is a problem that defective products are likely to be generated on the first 3 to 5 sheets after the restart of the operation, and the production efficiency further decreases.
[0004]
In order to solve the above problem, Japanese Patent Application Laid-Open No. 2000-255153 discloses a method of sucking up ink in an ink bottle while stirring and automatically supplying the ink on a screen. In particular, when ink is automatically supplied, there is a problem with the ink supply method including the above-described countermeasure against ink shortage, but the technique disclosed in the above publication is performed as follows.
[0005]
FIG. 5 conceptually shows the configuration of the screen printing machine. In the printing machine 1, the screen printing plate 3 placed on a gantry (not shown) and the ink 4 are applied to the entire surface of the screen printing plate 3. A squeegee 7 that pushes the doctor blade 5 and the ink 4 to be stretched out through the gap between the screens is provided.
[0006]
Then, as shown in FIG. 6A, a screen printing plate 3 is disposed in proximity to a work (printed material) 2 placed on a gantry and screen printed through a tube (not shown) of an automatic feeder. A predetermined amount of ink 4 is dropped on the plate 3.
[0007]
Next, the ink 4 is stretched over the entire surface of the screen printing plate 3 from the left end to the right end in FIG. Then, the doctor blade 5 is lifted up, and instead the squeegee 7 is pressed against the screen printing plate 3, and while moving from the right end to the left end of FIG. 2 is printed (printing completed).
[0008]
As shown in FIG. 2B, the detection of the ink running out is performed by applying detection light from the sensor 8 for detecting the presence or absence of ink installed above the screen 3 and pasting it on the screen printing plate 3. The detected light is reflected by the reflective tape, and when the reflected light is detected by the detection sensor 8, an ink out alarm is issued.
[0009]
That is, the detection of the remaining amount of ink for screen printing is based on the phenomenon that when the doctor blade diffuses ink on the printing plate, the ink is not sufficiently diffused to the edge of the printing plate due to the decrease in the remaining amount of ink. Thus, a method of detecting with a light reflection sensor is used.
[0010]
Alternatively, a method of counting the number of times of printing, setting a count number based on the amount of ink used in advance, and generating a signal when the count number is reached has been conventionally used. In addition, both of these methods are also used.
[0011]
[Problems to be solved by the invention]
However, the detection method using the light reflection sensor may cause a detection error depending on the type of ink color and physical characteristics. In the method of counting the number of printings, the amount of ink used varies depending on the printing design. Therefore, there is a problem that it is difficult to set the count number.
[0012]
Therefore, in screen printing, a great deal of attention and labor is required to prevent printing defects caused by running out of ink, especially when using an automatic ink feeder to save ink supply. Thus, the emergence of an easier and more reliable method for detecting the remaining amount of ink has been desired.
[0013]
The present invention has been made in view of the above problems, and an object thereof is to provide a screen printing machine that can easily and reliably detect the remaining amount of ink to be used in screen printing with a simple configuration. There is to do.
[0014]
In order to achieve the above object, a screen printing machine according to claim 1 includes a screen printing plate having pattern holes, a doctor blade for diffusing ink supplied from an ink supply unit on the surface of the screen printing plate, and the doctor. A screen printing machine having an arm portion supporting a blade and a squeegee that moves while pressing the ink diffused by the doctor blade and pushes it out of the pattern hole, from the start of the ink diffusion operation of the doctor blade Load detecting means for detecting the load applied to the doctor blade during the diffusion operation period until the end, and the load applied to the doctor blade during the diffusion operation period based on the viscosity characteristics and thixotropic properties for each type of ink used The load waveform signal is stored and the load for each type of stored ink is stored. Ink amount on the screen printing plate is set a threshold value for determining whether or not smaller than the predetermined amount based on the shape signal, the ink supply portion when the load detection value from the load detecting means is equal to or smaller than the threshold And an ink amount detecting means for transmitting a signal for prompting ink supply.
[0015]
According to this configuration, the amount of ink on the screen printing plate can always be grasped quickly and accurately. As a result, ink can be supplied at an appropriate timing, and the reliability and accuracy of printing can be improved. In addition, the process from the detection of the ink amount to the supply of ink is performed without delay in timing. Therefore, it is possible to reliably prevent the occurrence of problems due to a decrease in the ink amount. As a result, in addition to the action of always quickly and accurately grasping the amount of ink on the screen printing plate, it is not affected by the difference in the type of ink having different characteristics such as color and viscosity of the printing ink, and on the printing plate. The amount of ink can always be detected properly and higher quality printing is achieved.
[0016]
A screen printing machine according to claim 2 comprises:
The load detection means is configured by fixedly attaching the load cell as a part of the arm portion. With this configuration, the load detection means can be installed with an extremely simple configuration, and the load on the doctor blade can be detected directly and instantaneously with the configuration of fixed mounting to the arm. This improves the accuracy of ink amount detection.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional side view of a screen printing machine according to an embodiment. As shown in the figure, an operation of diffusing ink over the entire surface can be performed on a screen printing plate 21 having pattern holes. Thus, a doctor blade 25 is provided.
[0021]
That is, the doctor blade 25 is supported by the drive unit on the main body side by the arm 26, and the squeegee 27 for applying ink to the position shifted from the doctor blade 25 above the screen printing plate 21 on the main body side. Is supported by the squeegee unit 29.
[0022]
The arm 26 of the doctor blade 25 is equipped with a load cell 28 as load detecting means for detecting a load applied to the doctor blade 25 and outputting a signal based on the detected load. The output signal (load signal) S1 from the load cell 28 is amplified by the amplifier 201 and sent to the storage / control device 202 as the ink amount detection means (load signal S2).
[0023]
That is, the load cell 28 is fixedly attached as a part thereof so that a load applied to the arm 26 is directly transmitted. In the present embodiment, it is fixedly attached between the upper arm 26a and the lower arm 26b. Therefore, the load cell 28 can capture a change in strain that causes a change in the load applied to the arm 26 according to the remaining amount of ink on the screen printing plate 21, and can instantaneously output this as an electrical signal. The storage / control device 202 can easily detect the ink amount based on the amplified load signal S2.
[0024]
Next, when it is determined that the amount of ink is less than a predetermined amount, an ink supply signal is sent to the automatic ink feeder, and this storage / control device 202 further sends a doctor blade 25 for each ink to be used. The characteristics of the applied load are stored in advance. This is to store a change in the output value from the load cell 28 accompanying the movement operation of the doctor blade 25. For example, the first data supplied with a predetermined amount of ink is detected and its characteristics are recognized. Accordingly, it is possible to specify the corresponding ink type and the like, and to detect the ink amount more accurately based on the output value and the characteristics of the change.
[0025]
Ink supply control signal output to the automatic ink feeder is performed by setting a threshold value in advance, making a determination based on the threshold value, and automatically generating a control signal based on the amount of ink. The threshold value may be set by the user according to the type of ink, or data for each ink type stored in advance may be mapped and the threshold value may be automatically determined therefrom.
[0026]
FIG. 2 is a diagram for explaining a method for detecting the amount of ink in actual printing using the screen printer shown in FIG. Elements that are the same as those shown in the configuration of FIG.
[0027]
An ink 31 is applied on the screen printing plate 21 having pattern holes (usually automatically supplied by an automatic supply device), and the doctor blade 25 diffuses the ink 31 over the entire surface of the printing plate. Therefore, the state where the printing plate 21 is moved to the middle while performing the operation is shown.
[0028]
Since the ink used has different physical properties (viscosity, etc.) for each type, the storage / control device 202 stores the characteristics of the load applied to the doctor blade 25 for each type of ink, The load signal S2 is determined according to the feature. That is, a control signal is generated based on a threshold value set for each ink type.
[0029]
Basically, when the amount of ink on the screen printing plate 21 is large, the load applied to the doctor blade 25 is large, but when the ink is consumed and decreased, the load applied to the doctor blade 25 is also small. The output value (voltage value) from the load cell 28 also decreases.
[0030]
FIG. 3 is a load signal waveform diagram showing both states. FIG. 3A shows a case where the amount of ink on the screen printing plate 21 is large, and FIG. 3B shows a case where the amount of ink is small. is there. As shown in the figure, the region where the voltage value of the output signal increases with the movement of the doctor blade 25 is close, but the value is clearly different depending on the amount of ink (the higher the amount of ink, the higher the transition. )
[0031]
Such a waveform naturally varies depending on the physical characteristics of the ink used, particularly the viscosity characteristics. That is, in the case of ink having a high viscosity, the output is at a high level even when the amount of ink is decreased, and in the case of low viscosity, the output is naturally low. Further, for example, the output varies depending on the degree of thixotropic property.
[0032]
FIG. 4 shows output signal waveforms in the case of two different types of ink. As shown in the figure, when (Example 1) in FIG. 10 (a) is compared with (Example 2) in FIG. 10 (b), only the overall output value of (Example 1) is larger than that of (Example 2). In the case of (Example 1), the rise point of the initial output is delayed, but the rise is steeper, and in the case of (Example 2), it rises relatively slowly. Further, when the rise of the output value is finished in both cases, a decrease in output value, that is, a decrease in viscosity is observed thereafter. Therefore, both (Example 1) and (Example 2) have thixotropic properties, but the degree of (Example 1) is considered to be greater than that of (Example 2).
[0033]
As described above, even in the case of the same amount of ink, the waveform of the output signal changes depending on the type of ink, particularly depending on the viscosity characteristics. Therefore, the load applied to the doctor blade 25 in advance for each ink as described above. It is preferable to store a characteristic (that is, an output signal waveform), set a threshold value for generating a control signal for ink supply according to the characteristic, and generate a signal below the threshold value.
[0034]
In other words, each ink type is preset to output a signal for ink supply at a point corresponding to the characteristics of the ink, or the point at which a signal is output automatically from the characteristics of the newly stored signal waveform It is also envisaged to set it automatically. Thereby, the supply point setting for various inks becomes more accurate. It is also suitable for performing high quality printing to set the amount of ink supplied on the printing plate depending on the type of ink.
[0035]
【The invention's effect】
According to the screen printing machine of the present invention, the amount of ink on the screen printing plate can always be accurately grasped. As a result, it is possible to perform printing by supplying ink quickly and accurately, particularly in screen printing equipped with an automatic ink feeder. In addition, since the amount of ink on the printing plate can always be properly detected without being affected by properties such as the color and viscosity of the printing ink, a high-quality printed matter can be obtained quickly and easily.
[Brief description of the drawings]
FIG. 1 is a side sectional view of an example of a screen printing machine according to the present invention.
FIG. 2 is an explanatory diagram of a method for detecting the amount of ink when printing is performed according to the present invention using the printing machine of FIG. 1;
FIGS. 3A and 3B are diagrams showing load signal waveforms when ink amounts are different from each other. FIGS.
FIGS. 4A and 4B are diagrams showing output signal waveforms of two different types of inks, respectively.
FIG. 5 is a cross-sectional view of an example of a conventional screen printing machine.
[Explanation of symbols]
1, 21 Screen printing plate 5, 25 Doctor blade 26 Doctor blade 7, 27 Squeegee 28 Load cell

Claims (2)

Screen printing plate having pattern holes, a doctor blade for diffusing ink supplied from an ink supply unit on the surface of the screen printing plate, an arm unit for supporting the doctor blade, and ink diffused by the doctor blade A screen printing machine having a squeegee that moves while pressing and extrudes from the pattern hole,
Load detecting means for detecting a load applied to the doctor blade during a diffusion operation period from the start to the end of the ink diffusion operation of the doctor blade;
The load waveform signal of the load applied during the diffusion operation period is stored in the doctor blade based on the viscosity characteristics and thixotropic properties for each type of ink to be used, and based on the stored load waveform signal for each type of ink A threshold for determining whether or not the amount of ink on the screen printing plate is less than a predetermined amount is set, and when the load detection value from the load detection means is equal to or less than the threshold, ink is supplied to the ink supply unit. An ink amount detecting means for transmitting a prompting signal;
A screen printing machine comprising: The load detection means includes
The screen printing machine according to claim 1, wherein the load cell is fixedly attached as a part of the arm portion.

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