JP7185819B2 - Container inspection method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for inspecting a container having a mouth portion formed by cutting, and more particularly to a method for inspecting a container capable of accurately determining whether the container is good or bad based on an image photographed from one direction.

Plastic containers are molded, for example, by blow molding, but in blow molding, it is necessary to blow air into the parison in a sealed state, so it is not possible to mold with the mouth open. , the mouth is formed by cutting the excess part after molding.

At this time, due to poor cutting, so-called high cutting (cutting at a position higher than the predetermined cutting position. This makes the height of the mouth higher than the original height) or deep cutting (conversely, cutting too much) , cutting defects such as oblique cutting may occur. These cutting defects cause troubles such as capping defects and sealing defects when caps are attached after the containers are filled with contents, so inspections in the container production process are indispensable.

Methods for inspecting containers include, for example, detection methods using mechanical devices. A detection method using a mechanical device is a method in which the container is held by a driving device such as a cylinder and the stroke is determined. However, the determination of only the mechanical stroke may miss deep cuts, such as oblique cuts, for example.

There is also a method of detecting with a sensor that uses a laser beam, etc., but in order to stably detect diagonal cuts, it is necessary to inspect the circumference of the mouth from multiple directions, which requires large-scale equipment and increases capital investment. Besides, there is still the possibility of overlooking.

In view of this situation, examination using images is also under consideration (see, for example, Patent Document 1 and the like). In Patent Document 1, a plurality of reference images obtained by sequentially changing the angle of the opening of a normal container in the circumferential direction are stored, and a screw is specified from an inspection target image obtained by photographing the opening. A method of detecting a pattern and performing difference processing on each of a reference image and an image to be inspected to determine the quality of a container is disclosed.

JP 2016-8930 A

However, the inspection method described in Patent Literature 1 detects the pattern of the screw, and cannot be applied as it is to the detection of oblique cutting or the like. In addition, the detection device described in Patent Document 1 requires a plurality of cameras for photographing images, and determination of the quality of the container is complicated.

SUMMARY OF THE INVENTION The present invention has been devised in view of such conventional circumstances, and aims to provide a method for inspecting a container that can simplify the apparatus configuration and that enables accurate detection with simple operation. aim.

In order to achieve the above object, the container inspection method of the present invention is a container inspection method for a container having a mouth formed by cutting, wherein an image of the vicinity of the mouth is photographed from one direction, and in the image, Then, from the photographed image, the line formed by the tip surface of the mouth is extracted as the edge extraction line, and the line formed by the step formed near the mouth of the container by molding is extracted as the reference line, and these reference lines are extracted. and the edge extraction line, the presence or absence of high cutting or deep cutting is determined, and the difference between the maximum value and the minimum value in the container height direction of the edge extraction line, and / or the edge relative to the reference line It is characterized in that the oblique cutting of the container is determined based on the angular difference of the extraction lines .

In the inspection method of the present invention, observation from only one direction is sufficient, and cutting defects such as high cuts, deep cuts, and oblique cuts can be detected with high accuracy.

According to the present invention, it is possible to accurately detect cutting defects such as high cutting, deep cutting, and oblique cutting with a simple operation and device configuration.

It is a figure which shows the structural example of an inspection system. It is a figure which expands and shows the mouth part of a container. It is a figure which shows an edge extraction line and a reference line. FIG. 4 is a diagram schematically showing images of the mouth, where (a) shows a high-cut state, (b) shows a left-right diagonal cut state, and (c) shows a diagonal cut state from the front to the back. FIG. 10 is a diagram showing calculation elements in an edge extraction line; (a) is a diagram showing calculation elements in a state of diagonal cutting in the horizontal direction, and (b) is a diagram showing calculation elements in a state of diagonal cutting from the front to the back. FIG. 10 is a diagram showing an angular difference α of an end extraction line with respect to a reference line;

Hereinafter, a container inspection method to which the present invention is applied will be described with reference to the drawings.

First, in the inspection method of the present invention, an object to be inspected is, for example, a blow-molded container molded by blow molding. When molding a blow-molded container, a cylindrical molten resin (parison) is sandwiched between molds, and air is blown into the mold cavity to bring it into close contact with the mold cavity and shape it into a predetermined container shape.

In blow molding, since the parison is molded by blowing air into it, the mouth cannot be molded as an opening. form as During this excision, the cutting position is higher than the original cutting position, and the height of the container is higher than the standard value. In some cases, cutting defects such as a deep cut that becomes lower and an oblique cut that cuts obliquely may occur. These cutting defects cause troubles such as capping defects and sealing defects in user lines.

The inspection method of the present embodiment accurately detects these cutting defects to prevent troubles such as capping defects and sealing defects.

FIG. 1 shows an example of an inspection system for carrying out the inspection method of this embodiment. The inspection system of this embodiment is centered on a programmable logic controller (PLC) 1, which is a control unit. Prepare.

A controller 4 and an imaging camera 5 are connected to the image processing device 3 , and the quality of cutting is determined based on the image of the mouth of the container captured by the camera 5 . In the present embodiment, only one camera 5 is required to be installed because determination is made using only images taken from one direction. A lighting device 6 is installed near the camera 5, and a controller 7 for operating the lighting device 6 is connected to the lighting device 6. FIG.

The PLC 1 detects the container transported to the inspection device with the first photoelectric sensor 8, and instructs the image processing device 3 to inspect the container. Based on the determination output from the processing device 3, an operation instruction for the discharge electromagnetic valve 10 is issued. Specifically, when the image processing device 3 outputs a defective judgment, the corresponding container is detected by the second photoelectric sensor 9 and is removed from the carry-out route by operating the ejection electromagnetic valve 10 .

Next, a determination method in the image processing device 3 will be described.

FIG. 2 is an enlarged view showing the vicinity of the mouth portion 12 of the container 11. As shown in FIG. A plurality of stepped portions (first stepped portion 13 and second stepped portion 14 in this example) are provided at the mouth portion 12 of the container 11 . Further, in this example, in the region between the first stepped portion 13 and the second stepped portion 14, a threaded portion 15 is provided on the outer peripheral surface to be screwed with the threaded portion of the cap.

The container 11 is molded, for example, by blow molding, and the tip surface 16 of the mouth portion 12 is formed by cutting after molding. At this time, as described above, defects such as high cutting, deep cutting, and oblique cutting may occur. On the other hand, the first stepped portion 13 and the second stepped portion 14 are formed by being shaped into the cavity shape of the mold during molding, and there are no factors that change. It does not change.

Therefore, in the present embodiment, as shown in FIG. 3, a line formed by the tip surface 16 of the mouth 12 (extracted edge line T) and a line formed by the first stepped portion 13 (reference line K), and the presence or absence of high cutting or deep cutting is determined based on the interval (distance) D between the reference line K and the edge extraction line T.

If the tip surface 15 of the mouth portion 12 is formed with a high cut, the height of the tip surface 16 will be higher than the original height, and the interval (distance) between the reference line K and the end extraction line T will be increased. D becomes larger than a prescribed value (reference value). If deep cutting occurs when forming the tip surface 16 of the mouth portion 12, the height of the tip surface 16 becomes lower than the original height, and the interval (distance) D between the reference line K and the end extraction line T is smaller than the specified value (reference value).

Therefore, a reference value is set for the interval (distance) D between the reference line K and the edge extraction line T, and the interval (distance) D between the reference line K and the edge extraction line T measured from the image is the reference. If the value falls outside the allowable range, it should be judged as defective.

Note that when an image is captured, the position of the container 11 may move back and forth depending on the configuration of the transport path, etc., and the distance between the container 11 and the camera 5 may fluctuate. If the distance between the container 11 and the camera 5 changes, the interval (distance) between the reference line K and the end extraction line T also changes in the captured image. In such a case, for example, the dimension (diameter) R of the first stepped portion 13 is measured, and the ratio ( D/R) may be used to determine the quality. Even if the position of the container 11 moves back and forth, the ratio (D/R) does not change.

On the other hand, oblique cutting cannot be determined by the interval (distance) D between the reference line K and the end extraction line T. FIG. 4 is a diagram schematically showing the shape of the photographed mouth. In the case of a high cut, the edge extraction line T is the height reference (original height) as shown in FIG. 4(a). It can be determined from the interval (distance) D between the reference line K and the end extraction line T because it crosses the reference line K. However, if the cut is made obliquely, the photographed image shows the obliquely cut state in the horizontal direction, that is, FIG. 4(b). Even in the state of , it is possible to make an accurate judgment by comparing the height of the edge extraction line T with the reference even in the state of diagonal cutting from the front to the back, that is, the state of FIG. 4(c). can't

Regarding oblique cutting, the quality of the container is determined based on the difference between the highest value and the lowest value of the edge extraction line T in the height direction of the container. That is, as shown in FIG. 5, a plurality of extraction line calculation elements (dots indicated by circles in the figure) are set on the edge extraction line T, and the height of each of these calculation elements is measured. The difference between the highest value and the lowest value is obtained and compared with the reference value to determine the quality.

If the cut is correct (no oblique cut), the edge extraction line T is horizontal and the difference in height of each calculated element is zero. When oblique cutting occurs, the edge extracting line T is inclined obliquely as shown in FIG. 4(b), or becomes arcuate as shown in FIG. 4(b). Therefore, a difference occurs in the height of each calculation element. For example, when the end extraction line T is a slanted straight line as shown in FIG. 4(b), the height difference between the calculation elements a and b at both ends becomes maximum as shown in FIG. 6(a). Calculated element a is the highest value and calculated element b is the lowest value. When the end extraction line T is a circular arc as shown in FIG. maximum height difference between Therefore, the height difference between the highest value and the lowest value of the calculated element is calculated, and if the difference is equal to or greater than the allowable value, it can be determined as defective (diagonal cutting).

It should be noted that even in the same oblique cut state, the maximum calculation factor is calculated when the image is taken from the side as shown in FIG. The height difference between the value and the lowest value is different. As shown in FIG. 4(b), when the image is taken from the side and the end extraction line T becomes a slanted straight line, the height difference between the highest value and the lowest value of the calculation element becomes maximum, and FIG. 4(c) As shown in , when the image is taken from the back (front) and the end extraction line T becomes an arc, the height difference between the highest value and the lowest value of the calculation element is minimized. Therefore, it is necessary to consider the latter (in the case of a circular arc) and determine the allowable value of the height difference between the highest value and the lowest value of the calculation element.

Further, when the end extraction line T is a slanted line as shown in FIG. 4B, based on the angle difference α of the end extraction line T with respect to the reference line K, It is also possible to judge whether the container is good or bad. In addition to the height difference between the highest value and the lowest value of the calculation element, by calculating the angle difference α of the end extraction line T with respect to the reference line K, it is possible to more accurately determine the oblique cut. .

The determination method in the image processing apparatus 3 has been described above. Next, the operation procedure in the inspection method of this embodiment will be described.

When inspecting a container by the inspection system shown in FIG. 1, first, the setting screen is displayed by the touch panel 2, and the type of container to be inspected is selected. The container has a different shape depending on its type, and the height of the tip surface and the position of the step that serves as a reference also differ. Therefore, first, it is necessary to specify the type of container to be inspected.

After selecting the type of container, the setting scale of the XY stage of the camera 5 is checked and adjusted to the position according to the selected type. At the same time, the position, direction, etc. of the illumination 6 are also adjusted.

Containers to be inspected are conveyed by a conveyor or the like, each container is detected by the first photoelectric sensor 8, and the mouth of the container is photographed by the camera 5. - 特許庁The captured image is judged by the image processing section according to the aforementioned judgment criteria, and the PLC 1 outputs the judgment result. When there is an NG judgment, the PLC 1 issues an operation instruction based on the judgment output, the corresponding container is detected by the second photoelectric sensor 9, and the discharge solenoid valve 10 is operated to discharge it from the conveying path.

If the detection range is not appropriate, check the orientation of the container, camera position, etc. Further, when the inspection of non-defective products is NG, or when the inspection of defective products is OK, the determination range of various numerical calculations is changed based on the photographed image.

Although the embodiment to which the present invention is applied has been described above, the present invention is not limited to this embodiment, and it goes without saying that various modifications are possible without departing from the gist of the present invention. .

1 programmable logic controller (PLC)
2 touch panel 3 image processing device 4 controller 5 camera 6 lighting 7 controller 8 first photoelectric sensor 9 second photoelectric sensor 10 discharging solenoid valve 11 container 12 mouth 13 first stepped portion 14 second stepped portion 15 screw Part 16 tip surface

Claims (1)

A method for inspecting a container having a mouth formed by cutting,
Using an image taken near the mouth from one direction, in the image, a line formed by the tip of the mouth is extracted as an end extraction line, and a line formed near the mouth of the container by molding. The line formed by the stepped part is extracted as a reference line, and the presence or absence of high cutting or deep cutting is determined based on the interval between these reference lines and the edge extraction line,
Diagonal cutting of the container is determined based on the difference between the maximum value and the minimum value of the extracted edge line in the height direction of the container and/or the angular difference of the extracted edge line with respect to the reference line. Inspection methods.

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