JPH0343279Y2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application The present invention relates to a monitoring device for the polishing process of glossy paper.

B. Conventional technology Glossy paper is generally produced using the wet cast method, in which a wet coating layer is pressed against a specular drum for a glossy finish, the gel casting method, in which the wet coating layer is made into a gel state and pressed against a mirror drum, or the coating layer is After drying or semi-drying, wet casting is used to re-wet the paper and press it against a mirror-surfaced drum. During this glossing process, the paint on the paper surface adheres to the cast drum in dots, creating dents on the glossy surface and causing the cast drum to dry. Due to phenomena such as the paint adhering to the paper solidifying and creating dents in the coated surface of the paper that is subsequently pressed against it,
Defects appear on the surface of glossy paper. Conventionally, as a countermeasure against the occurrence of such defects, the paper that has been rolled up after the glossing process is visually observed to monitor the occurrence of defects, and when it is recognized that the number of defects is increasing, the cast drum is replaced. A method of cleaning the drum surface by buffing is used.

Since monitoring is performed intermittently in such a method, there is a problem that a response to a tendency for defects to occur frequently is delayed, or that the number of cleanings of the cast drum increases to avoid such a result, resulting in a decrease in production efficiency. There is also the problem that since humans are monitoring, subjective judgments are involved. For such problems,
This can be solved by continuously monitoring the surface of the glossy paper using photoelectric technology, but the cast drum is heated to about 80 to 120 degrees Celsius, and the paper that is pressed against the cast drum is preliminarily dampened. As a result, the atmosphere around the cast drum is hot and humid, making it unsuitable for installing photoelectric equipment. For this reason, a suitable location for monitoring the glossy paper surface is near the winder where the glossy paper that has gone through the glossing process is wound up, but since this location is quite long in terms of the distance the paper stretches from the cast drum, there are drawbacks to the monitoring level. A considerable amount of defective paper will be produced until it reaches a predetermined value and a buffing instruction is issued. Although it is desirable to monitor defects on glossy paper as close as possible to the point where the defects occur, it is difficult to monitor the surface of the cast drum photoelectrically due to the above-mentioned atmospheric problems.

C. Problems that the invention aims to solve In view of the above-mentioned situation regarding the monitoring of the polishing process of glossy paper, the present invention aims to enable continuous automatic monitoring at the position closest to the location where defects occur on glossy paper. That is.

D. Measures to solve the problem The change in the position of the paper being pressed against the cast drum leaving the cast drum is continuously monitored photoelectrically from the side of the cast drum. When this happens, a cast drum cleaning command will be issued.

E. Function In Figure 1, 1 is a cast drum, and 2 is coated paper that is polished. The drum 1 is rotating in the direction of the arrow, and the paper 2 begins to contact the drum 1 at a,
Leave the drum at point b. If there is no adhesion between the drum 1 and the paper 2, the point at which the paper separates from the drum is the contact point c between the common line between the drum 1 and the turning roller 3 and the drum 1; As the adhesiveness increases, the point at which the paper separates from the drum (release point) moves toward point b with a delay in the rotational direction of the drum. It has also been found that there is a correlation between this delay in the release point and the incidence of defects in glossy paper. The present invention is based on this knowledge and monitors the movement of the mold release point from the side of the drum 1. Monitoring of the mold release point does not require the imaging device to face the surface of the glossy paper or the drum, unlike the detection of abnormalities on the surface of the glossy paper or the cast drum, and can be monitored from the side. In particular, unlike the harsh environment above the drum, the monitoring device can be placed in a place with an atmosphere that is almost the same as a normal indoor environment, and continuous process monitoring can be easily performed at the location closest to the point where defects occur on glossy paper. be.

Embodiment FIG. 2 shows an embodiment in which the present invention is applied to a rewet casting device. 1 is a cast drum, and 2 is paper to be polished. The paper rewound from the unwinder 4 is coated and dried, and then the coated layer is re-wetted by the re-wetting liquid stored in the tap formed by the pressure roller 5 and the cast drum 1, and the paper is pressed against the cast drum 1. After rotating around the cast drum over an angular range of 200-odd degrees, it leaves the drum at point b, passes through the turning roller 3 and several guide rollers, and is wound into the winder 6. A light source 7 is positioned in the space sandwiched between the exposed surface of the cast drum 1 and the paper 2 separated from the drum 1, and illuminates the glossy surface of the paper 2 while facing toward the release point b. . The thus illuminated paper is imaged from the back side with a television camera 8.
Although the television camera 8 is shown above the drum 1 in FIG. 2, it is actually located on this side of the drum 1, and as shown in FIG. line) diagonally. paper 2
In Fig. 3, the light is illuminated from the bottom and the light is scattered and transmitted, so the area to the left of the mold release point b is bright, and the part wrapped around the drum 1 to the right of the mold release point is dark, resulting in a difference in brightness and darkness. The border is the mold release point. This boundary between light and dark moves to the left in FIG. 3 as the adhesion between drum 1 and paper 2 increases. Returning to FIG. 2, the video signal obtained by the television camera 8 is stored in the image memory 9 and is also used for monitoring.
The video signal visualized by the CRT 10 and stored in the image memory 9 is analyzed by the computer 11 and converted into position data of the mold release point. When the value is exceeded, a signal is sent to the buffing device 12 to cause the cast drum 1 to be buffed.

The computer 11 calculates the position data of the above-mentioned mold release point as follows. FIG. 4 shows an image of the video signal obtained by the television camera 8. As shown in FIG. Since the television camera 8 is looking diagonally in front and behind the release point of the paper 2, the right half of the screen is dark and the left half is bright, with the line l indicating the release point as the border.
A video signal along an arbitrary horizontal line ab in this image is as shown in FIG. The computer 11 sets the video signal at an appropriately determined identification level (for example, brightness).
50%), and calculate the area ratio (dark)/(total area) of the bright and dark parts in the rectangular area R set in the TV image, and use this value as the data for the position of the mold release point. In this embodiment, a buffing command is issued when the area ratio exceeds 80%. The above-mentioned arithmetic operation is performed with one cycle of three minutes. The video signal for the first 30 seconds of this 3 minute period is stored in the image memory 9.
During the remaining 2 minutes and 30 seconds, the position data of the mold release point is calculated, compared with a predetermined value, and a decision is made as to whether or not to issue a buffing command.
is cleared and the next 3-minute cycle begins.

In this embodiment, the determination level for determining whether or not to issue a buffing command based on the position data of the mold release point is performed as follows. Light source 1 illuminates the glossy surface of paper 2 at guide roller 12 in front of winder 6.
3, and a portion of a certain width in the width direction of the paper 2 is monitored by a camera 14 having a CCD line sensor as an image sensor in the specular reflection direction of the illumination light on the paper 2. The visual field image of the camera 14 is a single line of light because it is an image of specularly reflected light from the light source 13 on the glossy surface of the paper 2 that is curved along the roller 12, and the CCD line sensor detects this light line. A line image is captured. If there is a defect on the glossy surface of the paper, light will be scattered there, so it will appear as a dark dot in the field of view of the camera 14, and the video signal obtained by the CCD line sensor will show the defect as shown in Figure 6. The point appears as a downward peak p. The defect detector 15 performs level selection from this video signal to detect defects. The computer 11 counts and stores the number of defects detected during a period of 12 minutes. In this manner, the position data of the release point immediately after the buffing of the cast drum 1 is completed and the number of defects in units of 12 minutes are displayed in a graph on the CRT 16. FIG. 7 is an example of such a graph in which time progresses from right to left over five hours. L is the position data of the mold release point, read on the scale on the left, and the bar graph is the number of defects per 12 minutes, read on the scale on the right. The change in the position of the mold release point is small for the first 80 minutes, then suddenly increases to 60-70%, and then increases somewhat gradually. Corresponding to this change, the disadvantages are almost 0 for the first 80 minutes, and the appearance rate is almost constant for about 2 hours after that (12.59 pieces / 12 minutes).
After that, the appearance rate increases rapidly. At the end of the period when the defect appearance rate is approximately constant, the position data of the mold release point is
This corresponds to 80%. In this example, the judgment level of the position data of the mold release point that issues the buffing command is set to 80.
The percentage was determined based on the above results.

As mentioned above, it is not necessary to set the discrimination level to a fixed value. For example, if the point where the slope of the video signal is the maximum in Fig. 5 is set as the discrimination level, the thickness of the paper to be processed changes and the transmitted light intensity changes. Even in such cases, stable binarization is possible.

G Effect This invention is based on the correlation between the change in the position where the processed paper leaves the cast drum and the defect appearance rate.
The system monitors the position of the mold release point and issues a command to clean the cast drum.Since the position of the mold release point can be monitored from the side of the cast drum, even if an imaging method is used, it will not be affected by high temperature and high humidity around the cast drum. Since it is not affected by the environment and is monitored at the location closest to the point where defects occur, there is no delay in issuing cast drum cleaning commands, and human subjectivity is not included, resulting in stable product quality and unnecessary cleaning of the drum. Inefficiency caused by increased cleaning frequency can also be avoided.

[Brief explanation of the drawing]

Fig. 1 is a diagram explaining the principle of the present invention, Fig. 2 is a block diagram showing the configuration of an embodiment of the invention, Fig. 3 is a plan view of the main part of the embodiment, and Fig. 4 is a monitor of the embodiment.
A diagram of the CRT screen, Figure 5 is a graph of the video signal,
Figure 6 is a graph of the video signal of the defect detection camera.
FIG. 7 is a graph of an example of recording defect appearance rate and position data of a mold release point.

Claims (1)

[Scope of utility model registration request] Imaging means for monitoring the movement of the release point where the workpiece paper leaves the cast drum is placed on the side of the cast drum where the workpiece paper is pressed against the cast drum, and the video signal obtained by this imaging means is analyzed to determine the release point. A glossy paper polishing process monitoring device comprising a control means for issuing a cast drum cleaning command when the movement of the cast drum exceeds a predetermined amount.