JP4332704B2 - How to detect wrinkles on the outer surface of the can - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting wrinkles on the outer surface of a can that inspects whether or not wrinkles are generated on the outer surface of a can such as a two-piece can with a film label.
[0002]
[Prior art]
Conventionally, two-piece can bodies applied to beverage cans such as juice and beer, cans for food canning, etc. are metal blanks such as aluminum and steel, or synthetic resin films such as these metal plates and PET films. The can body is molded from the laminated composite blank by drawing ironing, redrawing, etc., washed and surface-treated, and then printed on the outer surface of the can body by offset printing or direct printing from the plate cylinder Is doing. However, recently, in order to enhance the decorativeness of the container, it is required to print by a beautiful gravure printing or the like, and in order to meet this demand, it is difficult to directly perform gravure printing in the manufacturing process. As a means for overcoming the disadvantages of cans, various methods have been proposed for manufacturing two-piece cans by attaching a thermoplastic synthetic resin film such as a polyester film that has been pre-gravure-printed to a molded can body. (For example, Japanese Patent No. 2597020).
[0003]
The above-mentioned conventional can manufacturing method and apparatus for attaching a printed synthetic resin film (hereinafter referred to as “film label”) to a can body is mounted on a mandrel that revolves the formed can body, and a mandrel A can with a film label attached via a can body heating process for heating the can body by induction heating and a film attaching process for attaching a film label supplied from a film attaching roll to the can body The body is discharged from the mandrel and sent to the next necking process or the like. Further, as seen in JP-A-10-683, a mandrel heating step for heating the mandrel itself is provided before the can body heating step in order to raise the can body to a predetermined temperature in a short time. In some cases, the can body is also heated from the inner surface when the can body comes into contact with the mandrel. Alternatively, as can be seen in Japanese Patent Application Laid-Open No. 8-1778, it is known that the can body is preheated before being supplied to the mandrel roll.
[0004]
A conventional method for producing a film label sticking can body is to heat the can body to a normal temperature of 150 to 160 ° C. in the can body heating step, and press the film label to the can body surface at a predetermined pressure at the sticking station. Then, the adhesive applied on the surface of the film label is melted and thermally bonded to the surface of the can body. And after sticking, when a mandrel reaches a can body discharge position, a can body will be discharged from a mandrel in that state. Therefore, the can body is naturally cooled to some extent until it reaches the discharge position (see cooling section D of Japanese Patent No. 2597020), but when the line speed increases, the can body is discharged from the mandrel with little cooling. It will be. As a result, when the line speed is increased by 1000 to 2000 cans / minute or more, a film label at the time of discharging from the mandrel, and in the case of a can body in which a synthetic resin film is laminated on the inner and outer surfaces, the inner side synthetic resin still in a high temperature state There is a problem that the film is likely to be wrinkled or scratched by friction with the mandrel.
[0005]
In addition, when the film label is attached to the can body, there is a possibility that dust such as fine powder made of plastic strips / powder generated during molding of the can body may adhere to the surface of the can body. If a synthetic resin film is laminated on the surface of the can body with dust attached, the sticking property of the film label is deteriorated, causing wrinkles and the like.
[0006]
Therefore, in the can production line or the filling line, the appearance of the can and the surface condition such as printing are inspected, the cans with wrinkles are excluded as defective cans, and only good cans are used. Yes.
[0007]
The surface of the cylindrical can is printed with advertisements, marks, etc., but it is inspected whether the printing is done properly, and the can within the allowable width is filled as a good product. Yes. As an example of such an automatic inspection of cans, a rotating can on a turntable provided on an inspection table is divided in the circumferential direction by a camera for visual inspection provided opposite to the inspection table. It is obtained by photographing, detecting a reference point mark preprinted on the can with a mark detection sensor, generating a trigger signal by detecting the reference point mark, controlling the imaging of the camera and driving of the driving means, and imaging. The image data is processed, the inspection image is compared by the image processing comparison means, and the reference image storing the good image previously captured for each circumferential division of the can by the camera is compared, and the image or pattern is printed A can inner / outer surface inspection apparatus for inspecting the quality of the surface state of the inner surface of the can represented by the state has been proposed. In this can inner / outer surface inspection device, as with the mark detection sensor, a wrinkle detection sensor consisting of a gloss meter that images the entire circumference of the can is arranged, and the entire circumference of the neck of the can is inspected to detect wrinkles. (Patent Document 1).
[0008]
The inspection methods described in each of the above-mentioned documents are aimed at speeding up can manufacturing, but in recent can manufacturing lines and can filling lines, the entire system has been speeded up, and in order to cope with such speeding up, There is also a need for a correspondingly high speed in the inspection of the outer surface of the can. In addition, advanced cameras and image processing can obtain results according to the introduction of high-definition equipment, but system construction is expensive. As for the wrinkles on the outer surface of the can, it is difficult to detect without leakage any can in which wrinkles that should be defective are generated from the camera image taken from the front of the can.
[0009]
[Patent Document 1]
JP-A-6-174649 ([0018] to [0019], [021], [0031] to [0035], FIGS. 1 to 4 and FIG. 6)
[0010]
[Problems to be solved by the invention]
Therefore, in general, we focused on the fact that small bumps on the surface are easier to find when viewed under the light than when viewed from the front. There is a problem to be solved in terms of accurately detecting wrinkles generated in a can by applying the method to detecting wrinkles on the outer surface of a can that detects wrinkles generated in a can based on image processing.
[0011]
The object of the present invention is to make it easier to optically detect wrinkles that may occur on the outer surface of the can, and even if inspection time spent on individual cans is shortened, it is possible to overlook cans with wrinkles. It is an object of the present invention to provide a method for detecting wrinkles on the outer surface of a can that can be accurately detected and can cope with an increase in the speed of can manufacturing.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, a method for detecting wrinkles on the outer surface of a can according to the present invention irradiates the outer surface of a rotating can with illumination means, and illuminates the illumination means from the side that becomes the shadow of the can by irradiation with the illumination means. The outer surface of the can is photographed by an image pickup means, and the presence of the wrinkle is detected by photographing the reflected light reflected by the illumination means by the wrinkle generated on the outer surface of the can. Yes.
[0013]
According to this can outer surface wrinkle detection method, the outer surface of the can is illuminated by the illuminating means, and the can facing the imaging means is shaded by the irradiation light. When wrinkles are formed on the outer surface of the can, the wrinkles become a position where the outer surface of the can is covered with the irradiation light from the illumination means as the can rotates. The irregularities of the eyelids reflect the irradiation light even before the tangential position is exceeded. Even if the reflected light is instantaneous, it reaches the image pickup means, and the image picked up by the image pickup means is an image in which only the portion of the outer surface of the can that has become wrinkled is white. When no wrinkles are generated on the outer surface of the can, the captured image is a dark image, and this white glowing image portion does not appear. Therefore, the generation of wrinkles can be reliably detected by detecting an image shining white.
[0014]
It is preferable that the illuminating unit is arranged such that an irradiation position of the outer surface irradiated by the illuminating unit is within an elevation angle range of 0 ° to 80 ° from a tangential plane where the imaging unit faces as a tangential position. By irradiating at an elevation angle within a range of 0 ° to 80 °, preferably 20 ° to 40 ° with respect to the tangent plane, the wrinkles on the outer surface of the can can be efficiently detected as an image portion that is white. .
[0015]
In this method for detecting wrinkles on the outer surface of the can, the imaging means can be a line camera capable of photographing the tangential region at a time. By using a line camera as the imaging means, it is possible to photograph a tangential region extending in the generatrix direction on the outer surface of the can at a time, and to detect wrinkles generated on the can body at high speed.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a method for detecting wrinkles on the outer surface of a can according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic view showing an embodiment of a method for detecting wrinkles on the outer surface of a can according to the present invention. FIG. 2 is a diagram illustrating an example of a photographed image including a white glowing portion due to a cocoon.
[0017]
According to the embodiment of the method for detecting wrinkles on the outer surface of the can shown in FIG. 1, the can 1 is located at an inspection station on the inner and outer surfaces in the can making line, although not shown. The detection of wrinkles in the can 1 is performed while the can 1 is transported while rotating. In the inspection station, a camera (CCD camera) 4 which is an image pickup means is arranged in a mode in which a light receiving axis is in a tangential plane 3 in contact with the outer surface 2 of the can 1. The can 1 is rotating in the direction of the arrow, and the rotation speed is about 2600 rpm.
[0018]
A tangential portion 5 where the outer surface 2 of the can 1 is in contact with the tangential plane 3 is irradiated by the illumination means 7. The irradiation axis 8 by the illumination means 7 is arranged in the direction of the elevation angle θ within the range of 0 ° to 80 °, preferably 20 ° to 40 ° from the tangential plane 3. A region 6 closer to the camera 4 than the tangential portion 5 is a shadow region of irradiation by the illumination means 7. The elevation angle θ with respect to the tangent plane 3 is determined in consideration of directing light reflection by the eyelid to the camera 4.
[0019]
When the ridge 9 (see FIG. 2) is generated on the outer surface 2 of the can 1, the ridge 9 approaches the tangential portion 5 where the outer surface 2 contacts the tangential plane 3 as the can 1 rotates. Since the tangential portion 5 is illuminated by the illumination means 7, the reflected light reflected by the projections and depressions of the ridge 9 when illuminated by the illumination light is bright even if it is instantaneous. It reaches the camera 4 as a strong light. In the image captured by the camera 4 at this time, as shown in the area of the ellipse 10 in FIG. 2, only the portion that becomes the ridge 9 appears white on the outer surface 2 of the can 1 (black and white inversion in the figure). Show). The elevation angle θ is an angle smaller than 90 ° and the region 6 becomes a shadow. Therefore, when no wrinkle 9 is generated, a portion that is photographed dark and glows white does not appear in the image. It can be estimated that the wrinkles 9 are generated in the can 1 by detecting the white shining portion.
[0020]
In the can outer surface wrinkle detection method, it is possible to determine whether or not wrinkles 9 are generated in the can 1 by processing image data regarding the brightness of the image of the region 6 captured by the camera 4. The can 1 that has been estimated to have the bottle 9 can be automatically excluded from the can-making line based on the discrimination output signal from the data processing device.
[0021]
In this method of detecting wrinkles on the outer surface of the can, the camera 4 serving as the imaging means can be a line camera that can capture the region 6 at a time in the horizontal direction. By using the line camera, the region 6 extending in the generatrix direction of the outer surface 2 of the can 1 can be sequentially photographed as the can 1 rotates, and the ridge 9 generated on the can body can be detected at high speed. Become. Also when the line camera 4 is employ | adopted also about the illumination means 7, it is preferable to set it as the line light source arrange | positioned in parallel with the tangent part 5. FIG.
[0022]
【The invention's effect】
According to the method for detecting wrinkles on the outer surface of the can according to the present invention, as described above, the outer surface of the rotating can is irradiated with illumination means, and the can is placed on the illumination means from the side that becomes the shadow of the can by irradiation with the illumination means. The outer surface of the can is photographed by the imaging means, and the wrinkles generated on the outer surface of the can are detected by detecting the presence of the wrinkles by photographing the reflected light reflected by the illumination means, It is easy to optically detect wrinkles that may occur on the outer surface of the can, and it is possible to accurately detect without missing a can that has wrinkles, thereby preventing the shipment of defective products. Further, the speeding up of the can manufacturing line shortens the inspection time spent for each can, but this wrinkle detection method can cope with shortening the wrinkle detection time on the outer surface of the can.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an embodiment of a can outer surface wrinkle detection method according to the present invention.
FIG. 2 is a view showing an example of a photographed image including a portion that is lit white by a wrinkle when the can is photographed by the wrinkle detection method for the outer surface of the can according to the present invention.
[Explanation of symbols]
1 can 2 outer surface 3 tangent plane 4 camera (CCD camera)
5 Tangent part 6 Area 7 Illumination means 8 Irradiation axis 9 １０ 10 Ellipse θ Elevation angle

Claims (2)

The outer surface of the rotating can is irradiated with an illuminating means, and the outer surface of the can is photographed by the imaging means from the side that becomes a shadow of the can by irradiation with the illuminating means, and the outer surface of the can is exposed to the outer surface of the can A method for detecting wrinkles on the outer surface of the can, comprising detecting the presence of the wrinkles by photographing reflected light obtained by reflecting light generated by the illumination means .
The illuminating means is disposed within an elevation angle range of 20 ° to 80 ° from a tangential plane where the imaging means faces the irradiation position of the outer surface as a tangential position,
The imaging means images the reflected light in a mode in which a light receiving axis is in the tangent plane, and
A method for detecting wrinkles on an outer surface of a can, wherein the presence of wrinkles is detected by detecting a white-lighted portion in a dark image captured by the photographing means .   The method for detecting wrinkles on the outer surface of a can according to claim 1, wherein the imaging means is a line camera capable of photographing the tangential region at a time.

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