JPH08198234A - Method for checking flange length of can body - Google Patents

Abstract

PURPOSE: To automatically check a flange length with respect to all can bodies by a method wherein a flange part of the can body is photographed from above by an image sensor, and the image information is binarized to be counted in scanning. CONSTITUTION: Seamless can bodies 3 each having a flange part 3b equidistantly transported on a conveyor 2 are photographed from above by an image sensor 8c. By binarizing the image information, a can body image substantially made of a flange part image 3'b is obtained. A center position O of the flange part image 3'b is set, and an inner circle 32 and an outer circle 33 are set inside and outside the flange part image 3'b with the center O. Next, the flange part image 3'b is divided into a plurality of blocks having equal center angles. For every block, at least four scanning lines are run outward in a radial direction from the inner circle 32 to the outer circle 33. The number of scanned pixels is counted. An average flange length for every block is calculated for checking a flange length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to can bodies used for beer cans, carbonated drink cans, coffee drink cans, fruit drink cans, etc. (including can bodies in the manufacturing process before they become product can bodies). ) Of the flange length inspection method.

[0002]

2. Description of the Related Art Tin-free steel, tin-plated steel sheet,
A seamless can suitable for storing beer, fruit drinks, etc. has been proposed, which is made from a blank in which both sides or one side of a metal plate for a can such as an aluminum (alloy) thin plate is coated with an organic film such as a polyester film (for example, JP-A-1
-258822). In this type of seamless can, a blank is drawn to form a cup, and a redrawing die with a small radius of curvature at the processing corner is used for this cup, and a large height direction stretching force is applied to the body during molding. A thinning re-drawing process to be applied (simultaneously or in some cases, ironing process may be added in a later step) is performed once and then a bottom part is processed to form a seamless can body in which a flange part is left. Next, after heat treatment for removing residual strain due to drawing of the organic coating, the upper end of the can body is cut off together with the flange portion, and then the neck-in processing, the flange processing and the like are performed.

Due to the surface anisotropy of the metal plate, the setting of tools at the time of forming, a slight difference in the circumferential direction such as temperature, wrinkle holding pressure, etc., fluctuations in the wall thickness of the body and flange of the seamless can body. Is likely to occur. In particular, in the flange portion, a variation portion of the width in the circumferential direction of the ear or the like, that is, the length in the radial direction (referred to as flange length in this specification) is likely to occur. If there is a particularly long flange length, the can body is likely to be clogged or trimming failure in the trimming step of cutting off the upper end portion of the can body together with the flange portion. On the other hand, if there is a particularly short flange length, the thickness of the metal plate of the flange portion and the body portion below it becomes particularly large, so the organic coating peels off and corrosion resistance is reduced, or the flange portion is covered. Trouble is likely to occur such that a gap is generated during double-winding and the sealing performance is deteriorated. Therefore, it is desirable to perform an automatic 100% inspection of the flange length, but heretofore no proposal has been made for this type of inspection method.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for automatically inspecting all flange lengths of a can body.

[0005]

A method for inspecting a flange length of a can according to a first aspect of the invention is a substantially flange portion image obtained by image-capturing from above by an image sensor and binarizing the image-capturing information. It was measured by setting the center position of the can image consisting of only the image, then outwardly in the radial direction, passing through the flange image, and running at least four scanning lines to measure the number of pixels passing through. The invention is characterized in that the flange length is calculated based on the number of pixels, and the inspection is performed based on this flange length. In the invention according to claim 1, four scanning lines are run in an X-axis direction and a Y-axis direction from an arbitrary position inside the flange image, and the coordinate values X1 and Y1 at which each scanning line intersects with the inner edge of the flange image. , X2,
Y2 is calculated and X = (X1 + X2) / 2, Y = (Y1 + Y2)
It is preferable to set the X and Y coordinate values indicated by / 2 as the center position of the can body image (claim 2).

In the invention according to claim 1, the flange portion image is divided into four or more (p) blocks having the same central angle, and a plurality (q) of scanning lines are sequentially run in each block for calculation. It is preferable to inspect based on the average value of the flange lengths of the respective blocks (claim 3). In the case of the invention according to claim 1, the block is moved one scanning line at a time in the same circumferential direction, and each time obtained by repeating the method according to claim 3 a total number of scanning lines (p * q) times. It is also preferable to perform the inspection based on the average value of the flange length in each block calculated for each (claim 4).

[0007]

In the case of the invention according to claim 1, since the image is taken from above by the image sensor, only the flange portion of the can can be taken out and taken.
This imaging information is binarized by a computer and easily and automatically subjected to high-speed image processing. Since the center position is set from the can body image that substantially includes only the flange portion image obtained by the image processing, the radial direction can be determined. Therefore, the number of pixels passing through can be measured by running the scanning line radially outward and passing through the flange image. Based on the measured number of pixels, the length of the flange portion where the scanning line runs can be calculated. By comparing the length (flange length) of the flange portion with the determination reference value, it is possible to reject a can body having a too large flange length or a can body having a too small flange length. It is preferable to have as many flange length measurement points as possible, but if there are at least four points (preferably center angles are separated by about 90 degrees), that is, if four scanning lines are run, it is the minimum practical value. It is possible to carry out an inspection. As described above, there are various causes for the flange length to change, particularly the surface anisotropy of the metal plate, and the influence of the surface anisotropy due to the rolling direction is large, and the flange length is particularly large in the rolling direction portion. On the other hand, there is a tendency for the size to become particularly small in the direction perpendicular to the rolling direction. Therefore, it is sufficient that there are at least two points in the rolling direction and two points in the direction perpendicular to the rolling direction.

The center position of the image of the can body coincides with the center of the inner edge of the flange image because the inner edge of the image is theoretically a perfect circle (in actual images, it is often slightly distorted). The line satisfying the X value obtained by the method according to the second aspect is a straight line perpendicular to the center of the chords X1-X2 of the inner edge.
The line satisfying the Y value is a straight line perpendicular to the center of the inner edge chord Y1 + Y2. Since the X and Y coordinate values are the intersections of the above two straight lines, they are the center of the inner edge, that is, the center position of the can body image.

The variation of the flange length depends on the wall thickness of the body of the can when the flange portion is protruding or recessed with a certain width in the base portion such as a ridge of a mountain shape or an arc shape. Has a relatively large impact. Claim 3
As described above, when inspecting based on the average value of the flange length in each block calculated by sequentially running the plurality (q) of scanning lines in the plurality of (p) blocks, the peak in the flange portion It is possible to inspect protrusions or recesses such as shapes or arcs. Therefore, more reliable inspection becomes possible. As described in claim 4, the block (the number of blocks p) is moved by one scanning line in the same circumferential direction,
4. When the inspection is performed based on the average value of the flange length in each block calculated for each time, which is obtained by repeating the described method for all scanning lines (p * q) times, the method according to claim 3, With the method described above, the missed protrusions or recesses in the shape of a mountain or arc can be detected, so that a more reliable inspection becomes possible.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a front view of an example of an apparatus for carrying out the inspection method of the present invention. 1 is a transfer press, in which a cup formed by drawing from a blank coated with an organic coating such as polyester film on both sides of tin-free steel is thinned and redrawn twice, and then the bottom is processed. Then, the seamless can body 3 having the flange portion 3b is formed, and the seamless can body 3 made of a non-magnetic material (for example, rubber or plastic) is continuously moved at a speed of, for example, about 100 to 500 cans / minute. The cans 3 are delivered so that they are evenly spaced from each other.
A side wall plate 4 and a bottom plate 5 are provided on both sides and the bottom of the conveyor 2, respectively. The upper surface of the conveyor 2 is painted black with magic ink or the like in order to clarify the contrast of the image pickup screen with the flange portion 3b of the seamless can body 3. The bottom plate 5 located below the lighting umbrella 10 described later.
Similarly, the lateral portion of the conveyor 2 including the groove portion 5b is also painted black (see FIG. 3). The conveyor 2 advances in the direction of arrow A along the central upper surface 5a of the bottom plate 5. As shown in FIGS. 1 and 2, the side wall plate 4 near the exit of the transfer press 1 is automatically centered so that the center axis of the seamless can 3 to be transferred is on the center line 2a of the conveyor 2. For this reason, the trapezoidal centering tool 6 is fixedly installed as seen from the upper surface in which the interval is narrowed in the traveling direction. The distance d between the outlet portions of the centering tool 6 is equal to the body portion 3a of the seamless can body 3.
The outer diameter D is set to be about 5 mm larger.

The projector 7a is fixed to the fixture 19 on the upper part of the side wall plate 4 on the downstream side of the aligning device 6 by approaching it.
The photoelectric switch 7 including the light receiver 7b is provided (FIG. 3). The fixture 19 is slidable along the upper end of the side wall plate 4. Before starting the work, the position of the attachment 19 in the longitudinal direction of the side wall plate is finely adjusted, and a signal is emitted from the light receiver 7b, and at the moment when the CCD camera 8 described later takes an image, the optical axis 8a of the CCD camera 8 is changed. The alignment is performed so that the seamless can 3 is substantially positioned on the diameter perpendicular to the traveling direction A. The condenser lens 8b and the CCD are arranged at a position where the optical axis 8a is located directly above the conveyor center line 2a, which is separated by a distance D / 2 upstream of the light flux 7c of the photoelectric switch 7.
A CCD camera 8 having an image sensor 8c is arranged. CCD camera 8 is a frame (not shown)
Is fixed to a bracket 11 fixed to the optical axis 8 by a screw 12 passing through a horizontal slot 11a.
The axis of a and the conveyor center line 2a can be aligned.

The ring-shaped fluorescent lamp 9 and the illuminating umbrella 10 are arranged in a CCD so as to substantially surround the lens 8b of the CCD camera 8.
It is arranged coaxially with the camera 8. The fluorescent lamp 9 is lit during the inspection work by a high frequency power source (not shown) (a frequency of 20 KHz: when the frequency is 20 KHz or more, it becomes similar to a direct current lighting). A light diffusing plate 10b made of a white acrylic plate is attached to the lower portion of the lighting umbrella 10 excluding the central hole 10a. As shown in FIG. 1, on the downstream side of the conveyor 2, an upstream permanent magnet 13 and two electromagnets for receiving the seamless can 3 by magnetic attraction from the conveyor 2 and suspending and transporting it in the direction of arrow A. 14, a downstream permanent magnet 15, and an intermediate conveyor device 17 including a belt conveyor 16 made of a non-magnetic material (for example, rubber or plastic).
Is provided. A delivery belt conveyor 18 is disposed below the intermediate conveyor device 17 on the downstream side.

The light receiver 7b of the photoelectric switch and the CCD camera 8 are connected to the camera controller 25. The camera controller 25 sets the shooting conditions such as the shutter opening degree of the CCD camera 8 and the opening time. In the case of this embodiment, the shutter opening time is 1/1000 second. Two
Reference numeral 6 denotes a host computer (for example, a personal computer), which includes a CPU 26a, an image memory board 26b, and an interface 26c. The camera controller 25 is connected to the image memory board 26b, and C
The image pickup signal of the CD image sensor 8c is input to the image memory board 26b after passing through the camera controller 25, and the built-in A / D converter 256 is used for the grayscale gradation.
Numerical data of gradation is stored in the image memory board 26b. When the value of the numerical data is low, it is close to black, and when the value is high, it is close to white. The CPU 26a compares the numerical data with a preset appropriate binarization level (threshold value) to create a binned can body image 3 '(FIG. 4). The host computer 26 is an interface 26
It is connected to the M / G control mechanism 27 via c. The output signal of the M / G control mechanism 27 is input to the electromagnet 14 to input to the electromagnet 1.
4 is ON-OFF controlled.

The inspection of the width of the flange portion 3b of the seamless can 3, that is, the flange length, by the above-mentioned apparatus is performed as follows. Seamless can 3 placed on the conveyor 2 and transferred in the direction A at equal intervals.
When the light beam 7c of the photoelectric switch 7 is cut off, the signal from the light receiver 7b is input to the CCD camera 8 via the camera controller 25, the electronic shutter (not shown) of the CCD camera 8 is driven, and the image sensor 8c becomes seamless. The upper part of the can body 3, especially the flange part 3b, is photographed. The photographed image, after passing through the camera controller 25, is converted into numerical data of black and white gradation 256 gradations, and is fetched and stored in the image memory board 26b. The flange 3b
An appropriate binarization level (threshold value) is set in advance so that (normally an average width of about 4 mm) is clearly displayed over the entire circumference. The CPU 26a compares the numerical data with this binarization level to create the binarized can body image 3 '. The image sensor 8c has a lateral width of 102.4.
The horizontal division is 256 mm, and the vertical length is 96.8 mm, which is 242 vertical divisions. Therefore, the image data is 256 horizontally.
It is composed of (0 to 255) pixels and 242 (0 to 241) pixels in the vertical direction, and one pixel is 0.4 mm * 0.4 mm square.

FIG. 4 shows an example of a can body image 3 '. In the coordinate system, the origin (0,0) is at the upper left, and the X axis extends to the right (255,0). The Y axis extends downward to the point (0,241). In FIG. 4, the flange image 3'b is black, but this is done for the sake of convenience of illustration, and the black and white are actually reversed. The same applies to FIG. 5 described later. First, the center position O of the can body image 3'is determined as follows. The inner circle 30 is set at an arbitrary position in the flange image 3'b, and the flange image 3'b
An outer circle 31 concentric with the inner circle 30 is set outside. Then the inner circle 3
Four scanning lines x1, y1, x2, y2 are run from the center O ′ of 0 toward the outer circle 31 in the X-axis direction and the Y-axis direction, and each scanning line is an inner edge 3′b1 of the flange portion image 3′b. The coordinate values X1, Y1, X2, Y2 intersecting (see FIG. 6) are obtained. X
= (X1 + X2) / 2, Y = (Y1 + Y2) / 2, the X and Y coordinate values are the center position O of the can body image 3 '. The center position O of the can body image 3'obtained by this method often deviates slightly from the actual center position because the inner edge 3'b1 is not necessarily a perfect circle, but this deviation is within the allowable range, so it is practical. There is no problem on the top.

Next, as shown in FIG. 5, an inner circle 32 and an outer circle 33 whose center is O are set near the flange image 3'b and inside and outside the flange image 3'b, respectively. Further, the flange image 3'b is divided into 16 blocks having the same central angle. Next, for each block, and in the order of 1, 2, ..., 16 blocks, with the inner circle 32 as the starting point and the outer circle 33 as the ending point, 16 lines at the same center angle outward in the radial direction (in FIG. 5, , 12 scanning lines 34 are run to avoid obscuring the figure), and the gray level of each pixel between the inner circle 32 and the outer circle 33 through which each scanning line 34 passes is measured. The measured value is compared with a threshold value, and the number n of pixels higher than the threshold value, that is, having high whiteness is counted.
Blocks whose angle θ formed by the X-axis, that is, the X′-X ″ line is 45 degrees or less, that is, in the case of FIG. 5, 1, 2, 7, 8,
In blocks 9, 10, 15, and 16, pixels are counted in the X-axis direction. The counting method will be specifically described with reference to FIG. In the case of the scanning line 34a running in the X-axis direction from the center O of the can image 3 ', that is, the scanning line 34a in the line OX' direction.
In the case of, the count value n is the outer edge 3'b2 and the scanning line 34a.
Is the difference between the X-direction coordinate value m16 of the intersection point and the X-direction coordinate value m3 of the intersection point of the inner edge 3'b1 and the scanning line 34a, that is, 13.

A line OX 'at the center O of the can body image 3'.
In the case of the scanning line 34b forming an angle θ (θ is 45 degrees or less) with respect to the count value n, the count value n is the outer edge 3'b2 and the scanning line 34a.
The difference between the X-direction coordinate value m11 of the intersection point and the X-direction coordinate value m0 of the intersection point of the inner edge 3′b1 and the scanning line 34b is 11, that is, 11. When the count value is n, the length L (flange length: unit is mm) of the portion of the flange portion image 3′b scanned by the scanning line 34 is nx0.4 / cos θ.
0.4 is the length (mm) of one side of one pixel in the case of the present embodiment. An angle θ with the X axis is greater than 45 degrees and equal to or less than 90 degrees, that is, in the case of FIG.
In blocks 4, 5, 6, 11, 12, 13, and 14, the angle formed by the line OY ′ is θ, for example, like the scanning line 34c.
, The pixels are counted in the Y-axis direction. Count value n
The method for obtaining the length L is the same as that for counting in the X-axis direction. The coordinate value of the center O of the above can body image 3 ',
The CPU 26a calculates the count value n and the length L,
It is performed based on a program stored in advance. The number of scanning lines in each block does not have to be 16 and may be 32, for example.
An appropriate number of four or more may be used.

The CPU 26a obtains an average value of the flange length L obtained by each scanning line 34 for each block, and an average flange length L larger than an upper limit judgment reference value L '(for example 9.0 mm) or a lower limit judgment reference. When an average flange length L smaller than the position L ″ (for example, 1.0 mm) is detected, a reject signal is output to the M / G control mechanism 27 via the interface 26c. When the reject signal is input, M / G control is performed. Mechanism 27
When the seamless can 3 passes below the electromagnet 14 of the intermediate conveyor device 17, the electromagnet 14 is deenergized, and the seamless can 3 is gravity-dropped from the belt conveyor 16 in the direction of arrow B and rejected. To do. The normal can 3 passes directly under the electromagnet 14, is released from the magnetic force of the permanent magnet 15 at the downstream end of the belt conveyor 16, is dropped and placed on the delivery belt conveyor 18, and is transferred to the next step.

After obtaining the average value of the flange length L by the method described in paragraphs 0016 and 0017, each block is moved by one scanning line in the clockwise direction or the counterclockwise direction, that is, in the same circumferential direction. In FIG. 5, the operation of moving the scanning line 34d of one block onto the line OX ′ and repeating the above-described method to obtain the average value of the flange length L of each block is repeated several times for all scanning lines ( 1
6 × 16 = 256 times), and the rejection described in paragraph number 0018 may be performed based on the average value of the flange length L in each block calculated each time. At least 4 without blocks
The length L of the flange portion image 3′b calculated by the scanning lines of the book is used as the flange length, and this value is compared with the upper limit determination reference value L ′ and the lower limit determination reference value L ″ to perform the above inspection. The total number of scanning lines in claims 1 and 3 is preferably about 200 to 550. The reason is as follows: The larger the number of scanning lines, the more reliable the inspection becomes possible. Therefore, it is preferable that the number of scanning lines is about 200 or more.However, even if the number of pixels of the image sensor (usually 200 to 700 in the horizontal direction and 200 to 500 in the vertical direction) becomes too large, the resolution does not follow and the effect is not obtained. Further, since an image sensor having a large number of pixels is expensive and may be over-inspected, it is preferable that the number of scanning lines is about 550 or less, so that the number of scanning lines is generally 25.
6 or 512, preferably about 200-550.

The present invention is not limited to the above-described embodiments. For example, when the metal plate of the web is made of a non-magnetic material such as aluminum, vacuum suction is used as the suction means of the seamless can body 3. May be. That is, the conveyor belt 16 of the intermediate conveyor device 17 is
-16370, a slat conveyor having a large number of vacuum suction holes formed therein, and a permanent magnet 1
The lower portions of the portions corresponding to 3 and 15 are opened, and a vacuum chamber that is always in a vacuum state at least during work is set, and the portion corresponding to the electromagnet 14 is turned on and off by a vacuum valve operated by the M / G control mechanism. Alternatively, the vacuum chamber may have an open lower surface.

[0021]

The invention according to claim 1 has an effect that all the flange lengths of cans can be automatically inspected. The invention according to claim 2 has an advantage that the center position of the can can be easily set from the flange image of the can in the invention according to claim 1. The invention according to claim 3 has an advantage that it is possible to more reliably perform 100% automatic inspection of the flange length of the can body. The invention according to claim 4 has an advantage that the total number of flange lengths of cans can be automatically inspected even more reliably.

[Brief description of drawings]

FIG. 1 is an explanatory front view of an example of an apparatus for carrying out an inspection method of the present invention.

FIG. 2 is a plan view taken along line II-II in FIG.

FIG. 3 is a vertical sectional view taken along the line III-III in FIG.

FIG. 4 is an explanatory diagram showing a method of setting the center position of a can body image obtained by binarizing the image pickup information of the image picked up by the apparatus shown in FIG.

5 is an explanatory drawing for showing an example of a method of calculating a flange length from a flange portion image obtained by binarizing image pickup information of an image picked up by the apparatus shown in FIG. 1. FIG.

6 is an enlarged view of an essential part of FIG. 5 for explaining the method of calculating the flange length in FIG. 5 in more detail.

[Explanation of symbols]

 3 Seamless can body (can body) 3b Flange part 3'Can body image 3'b Flange part image 3'b1 Inner edge 8c Image sensor 28 Pixel 34 Scan line 34a Scan line 34b Scan line 34c Scan line

Claims (4)

[Claims] 1. A center position of a can body image, which is obtained by image-capturing from above by an image sensor and binarizing the image-capturing information, and substantially consisting of only a flange portion image, and then outwardly in a radial direction. , The number of pixels passing through the flange image and running at least four scanning lines is measured, and the flange length is calculated based on the measured number of pixels,
A method for inspecting a flange length of a can body, characterized by inspecting based on this flange length. 2. X from an arbitrary position inside the flange image
Coordinate values X1, Y1, where four scanning lines are run in the axial direction and the Y-axis direction, and each scanning line intersects the inner edge of the flange image.
X2 and Y2 are calculated, and X = (X1 + X2) / 2, Y = (Y1 +
The method for inspecting the flange length of a can according to claim 1, wherein the coordinate values of X and Y represented by Y2) / 2 are used as the center position of the can image. 3. A flange in each block, which is calculated by dividing the flange image into four or more (p) blocks having the same central angle and sequentially running a plurality (q) of scanning lines in each block. The method for inspecting a flange length of a can according to claim 1, wherein the inspection is performed based on an average value of the length. 4. The method according to claim 3, wherein the block is moved by one scanning line in the same circumferential direction, and the number of scanning lines (p * q) is applied.
The method for inspecting a flange length of a can according to claim 1, wherein the inspection is performed based on an average value of the flange lengths in each block calculated each time, which is obtained by repeating the operation.