Folding joint inspection method

Abstract

To provide a folding / joint inspection method capable of easily inspecting whether a corrugated cardboard sheet is suitably folded and joined to form a cylindrical shape by adhesion of a splicing margin piece, concurrent with manufacturing a corrugated cardboard box in a box making line.SOLUTION: In the box making line, a digital camera is arranged between a folding part and a counter ejector part, in a position isolated from a conveyance path in a folding direction of a corrugated cardboard sheet 10. The camera obtains a two-dimensional image of a first region 32a that includes at least a part of a portion in which an end side 14e of a fourth face 14 and a splicing margin piece 15 overlap. When an edge E1 is detected in image processing of this region, the splicing margin piece is inside the fourth face. If this state is detected when internal pasting is carried out in the box making line, the folding / joint is determined to be suitably carried out, and if this state is detected when external pasting is carried out in the box making line, the folding / joint is determined to be not suitably carried out.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a folded joint inspection method for inspecting whether jointing, in which a corrugated cardboard sheet is folded and formed into a cylindrical shape by adhering a joint margin piece, is properly performed in a corrugated box making line. [Background Art]

[0002] In a production line that continuously performs corrugated cardboard sheet production and box making, after the corrugated cardboard sheet formed by bonding a corrugating medium to front and back liners is scored with horizontal ruled lines and cut, printing, vertical creasing, formation of cut slots and joint margin pieces, adhesive application to the joint margin piece, folding and adhesion of the joint margin piece are continuously performed in the subsequent box making line. Then, a predetermined number of corrugated cardboard sheets cylindrically joined by adhesion of the joint margin pieces are stacked in a folded state and carried out from the downstream end of the box making line.

[0003] In the above process, a corrugated cardboard sheet (blank) with adhesive applied to the joint margin piece is gradually folded and joined, and there are two types of joining here: "inner pasting" and "outer pasting". Referring to Figs. 10 and 11, the four surfaces constituting the side surface of the corrugated box will be described, which are referred to as "first surface 11", "second surface 12", "third surface 13", and "fourth surface 14" in order starting from the surface adjacent to the joint margin piece 15.

[0004] As shown in Fig. 10, "inner pasting" is when adhesive G is applied to the surface (upper surface in the drawing) of the joint margin piece 15 in the direction opposite to the direction in which the corrugated cardboard sheet 10 is folded (lower direction in the drawing), and the first surface 11 is folded before the fourth surface 14. As a result, as shown in the lower left of Fig. 10, a normal product B1n is produced in which the joint margin piece 15 is adhered to the inner surface of the fourth surface 14 to form a cylindrical shape.

[0005] On the other hand, as shown in Figure 11, in the case of the splice piece 15, adhesive G is applied to the surface (shown as the bottom surface) in the same direction as the direction in which the corrugated cardboard sheet 10 is folded, and the fourth surface 14 is folded before the first surface 11, which is called "outer bonding". As a result, as shown in the lower left of Figure 11, the splice piece 15 is bonded to the outer surface of the fourth surface 14, and a normal corrugated cardboard box B2n is manufactured in a cylindrical shape.

[0006] However, due to warping or other reasons in the corrugated cardboard sheet 10, the first side 11 and the fourth side 14 may not be folded in the correct order. For example, even if the product is manufactured with an inner lining, if the fourth side 14 is folded before the first side 11, the seam allowance 15 will not be joined and the product will not be cylindrical, resulting in a defective product B1d, as shown in the lower right of Figure 10. In this case, not only is the corrugated cardboard sheet 10 a defective product B1d, but when a predetermined number of sheets are stacked in the folded state, the seam allowance 15 will adhere to the adjacent normal product B1n, causing even properly manufactured corrugated cardboard sheets to become defective.

[0007] Similarly, even though the manufacturing process involves external bonding, if the first surface 11 is folded before the fourth surface 14, the splice piece 15 will adhere to the inner surface of another side (the third surface, as shown) other than the fourth surface 14, as shown in the lower right of Figure 11, resulting in a defective product B2d.

[0008] Traditionally, inspections to check for such defects were performed visually by workers. However, visual inspection by humans had several problems, including a heavy workload for workers, the time-consuming nature of the inspection compared to the high-speed production of cardboard boxes, and the risk of missing defects when attempting to perform the inspection quickly.

[0009] Therefore, the applicant has already proposed a method and apparatus for inspecting whether the folding and joining of corrugated cardboard sheets into a cylindrical shape by bonding the seam pieces is done properly, in parallel with the manufacturing of corrugated cardboard boxes on a box-making line (see Patent Document 1).

[0010] The technology described in Patent Document 1 involves a box-making line in which a corrugated cardboard sheet, with adhesive applied to a seam, is gradually folded and joined into a cylindrical shape at a folding joint section, and the folded cardboard is discharged and stacked at a discharge section. A displacement sensor is placed at a position away from the movement path of the corrugated cardboard sheet in the direction in which the corrugated cardboard sheet is folded. The displacement sensor detects the distance to the corrugated cardboard along the path through which the seam is passed. A second displacement sensor is placed at a position away from the displacement sensor in a direction perpendicular to the movement path. The second sensor detects the distance to the corrugated cardboard sheet along the path through which the portion of the corrugated cardboard sheet without a seam is passed, at the same timing as the detection by the displacement sensor.

[0011] When the folded corrugated cardboard sheets are joined using the "internal joining" method, the distance detected by the displacement sensor and the distance detected by the second displacement sensor are approximately equal, so the difference between them is almost zero. On the other hand, when the folded corrugated cardboard sheets are joined using the "external joining" method, at the time the displacement sensor detects the distance to the seam allowance, there is a difference between the distance detected by the displacement sensor and the distance detected by the second displacement sensor that corresponds to the thickness of the seam allowance. Therefore, based on the difference between the distance detected by the displacement sensor and the distance detected by the second displacement sensor, it is possible to detect whether the seam allowance is on the outside or inside of the folded corrugated cardboard sheet and to determine whether the folding and joining has been done properly.

[0012] The applicant has been continuously exploring different means to solve the above-mentioned problems. This invention was made during that process. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Patent No. 6393286 [Overview of the project] [Problems that the invention aims to solve]

[0014] As described above, the object of the present invention is to provide a folding joint inspection method that can easily inspect whether the folding of corrugated cardboard sheets and the bonding of the joint pieces to form a tubular shape are properly performed, in parallel with the manufacturing of corrugated cardboard boxes on a box-making line. [Means for solving the problem]

[0015] To solve the above problems, the folding joint inspection method according to the present invention is "In a box-making line, a digital camera is positioned between a folding joint section where corrugated cardboard sheets, glued to the joint pieces, are gradually folded and joined into a cylindrical shape, and a discharge section where the folded corrugated cardboard sheets are discharged and stacked, at a location isolated from the corrugated cardboard sheet transport path in the direction in which the corrugated cardboard sheets are folded." When the side of the tubular corrugated cardboard sheet that is joined to the splice is designated as the fourth side, The digital camera acquires a two-dimensional image of the first region, which includes at least a portion of the area where the edge of the fourth surface and the splice overlap. By detecting whether or not the splice is inside or outside the fourth surface based on the presence or absence of edge detection in the image processing of the two-dimensional image of the first region, it is determined whether or not the folding and joining has been done properly. It is, The edge detection is performed by detecting linear edges where the grayscale values ​​of pixels constituting the two-dimensional image change discontinuously, and these edges are continuous for a predetermined length or longer. The edge detected in the first region is the edge of the fourth face. When an edge is detected in the first region, the splice is determined to be inside the fourth face. If no edge is detected in the first region, the splice is determined to be outside the fourth face. "That is the case."

[0016] "Folded joint" refers to "a joint in which corrugated cardboard sheets are folded and joined into a cylindrical shape by the adhesion of a splice." When an edge is detected by image processing of a two-dimensional image of a first region that includes at least a part of the area where the edge of the fourth surface and the splice overlap, this edge is the edge of the fourth surface. In other words, the splice is on the inside of the fourth surface. Therefore, if this condition is detected when the inner lining is being applied on the box-making line, it can be determined that the folded joint has been properly applied, and if this condition is detected when the outer lining is being applied on the box-making line, it can be determined that the folded joint has not been properly applied and the inner lining is not properly applied.

[0017] On the other hand, if no edge is detected when image processing is performed on the first region, the splice is located outside the fourth surface in the first region. Therefore, if this condition is detected when the outer layer is being attached on the box-making line, it can be determined that the folding and joining is done correctly. If this condition is detected when the inner layer is being attached on the box-making line, it can be determined that the folding and joining is not done correctly and the outer layer is not being attached correctly.

[0018] The "external bonding state" is a defective product B1d in which the product is folded as if it were externally bonded, but the splice piece 15 is not adhered to the designated part, as shown in the lower right of Figure 10, and is distinguished from a properly performed "external bonding". Similarly, the "internal bonding state" is a defective product B2d in which the product is folded as if it were internally bonded, but the splice piece 15 is not adhered to the designated part, as shown in the lower right of Figure 11, and is distinguished from a properly performed "internal bonding". In other words, the folding joint inspection method of the present invention detects the external bonding state during the internal bonding process, or the internal bonding state during the external bonding process, as an improper state of folding joint.

[0019] The folding joint inspection method according to the present invention replaces the above configuration with: In a box making line, between a folding joint where a corrugated cardboard sheet with glued lap pieces is gradually folded and joined into a cylindrical shape, and a discharge section where the folded corrugated cardboard sheet is discharged and stacked, a digital camera is arranged at a position separated from the conveying path of the corrugated cardboard sheet in the direction in which the corrugated cardboard sheet is folded, when the side surface joined to the lap piece of the cylindrical corrugated cardboard sheet is defined as a fourth surface, acquiring, by means of the digital camera, a two-dimensional image of a second region including at least a part of a portion where the edge of the lap piece overlaps the fourth surface, determining whether the folding joint is properly performed by detecting whether the edge of the lap piece is located inside or outside the fourth surface based on whether edge detection is performed in the image processing of the two-dimensional image of the second region It is, Edge detection is performed by detecting linear edges where the grayscale values ​​of pixels constituting a two-dimensional image change discontinuously, and these edges are continuous for a predetermined length or longer. The edge detected in the second region is the edge of the splice piece. When an edge is detected in the second region, the splice piece is determined to be outside the fourth surface. If no edge is detected in the second region, the splice piece is determined to be inside the fourth surface. The present invention can be configured as described above.

[0020] When an edge is detected through image processing of the two-dimensional image of the second region including at least a part of the portion where the edge of the lap piece overlaps the fourth surface, the detected edge is the edge of the lap piece. That is, the lap piece is located outside the fourth surface. Therefore, if this state is detected when outer bonding is performed in the box making line, it can be determined that the folding joint is properly performed; if this state is detected when inner bonding is performed in the box making line, it can be determined that the folding joint is not properly performed and is in an outer bonding state.

[0021] On the other hand, when no edge is detected during image processing of the second region, the lap piece is located inside the fourth surface in the second region. Therefore, if this state is detected when inner bonding is performed in the box making line, it can be determined that the folding joint is properly performed; if this state is detected when outer bonding is performed in the box making line, it can be determined that the folding joint is not properly performed and is in an inner bonding state.

[0022] The folding joint inspection method according to the present invention, in addition to the above configuration, The timing of the digital camera's capture can be determined based on the detection of the front edge of the corrugated cardboard sheet by the arrival detection sensor and a signal transmitted from an encoder provided on a rotating part synchronized with the drive unit that drives the transport of the corrugated cardboard sheet.

[0023] If the conveying speed of the corrugated cardboard sheets in the box-making line, the length of the corrugated cardboard sheets in the conveying direction, and the spacing between adjacent corrugated cardboard sheets in the conveying direction are constant, then a two-dimensional image of the first or second region can be obtained by taking photographs with a digital camera at predetermined time intervals. However, in box-making lines, it is common to continuously manufacture corrugated cardboard sheets (corrugated cardboard boxes) while changing the size of the sheets being manufactured, and the conveying speed of the corrugated cardboard sheets may also be changed.

[0024] In this configuration, the leading edge of the transported corrugated cardboard sheet is detected by a arrival detection sensor, and a signal transmitted from an encoder is used. Since the encoder is installed on a rotating part synchronized with the drive unit that drives the transport of the corrugated cardboard sheet, the transport speed of the corrugated cardboard sheet, the distance the corrugated cardboard sheet travels in a predetermined time, and the time required for the corrugated cardboard sheet to travel the predetermined distance can be determined from the signal from the encoder. Therefore, by combining the detection by the arrival detection sensor and the signal from the encoder, the timing for capturing a two-dimensional image can be determined for a first or second region set within a predetermined length range in the transport direction, and the capture timing can be quickly changed accordingly even if the size of the corrugated cardboard sheet or the size of the first or second region is changed. [Effects of the Invention]

[0025] As described above, the present invention provides a folding joint inspection method that allows for easy inspection of whether or not the folding joint has been properly performed, in parallel with the manufacturing of corrugated cardboard boxes on a box-making line. [Brief explanation of the drawing]

[0026] [Figure 1] This diagram shows the arrangement of a digital camera and the like in a folding joint inspection method, which is one embodiment of the present invention. [Figure 2] This is a diagram showing the configuration of a folding joint inspection device used in a folding joint inspection method, which is one embodiment of the present invention. [Figure 3] This figure illustrates the determination based on the presence or absence of edge detection in the first region, for (a) when the folded joint is attached on the inside, and (b) when the folded joint is attached on the outside. [Figure 4] This figure illustrates the determination based on the presence or absence of edge detection in the second region, for (a) when the folded joint is attached on the inside, and (b) when the folded joint is attached on the outside. [Figure 5] This figure illustrates the determination based on the presence or absence of edge detection in both the first and second regions, for (a) when the folded joint is attached on the inside, and (b) when the folded joint is attached on the outside. [Figure 6] This diagram illustrates the positioning of the first and second regions in the width direction based on the size of the corrugated cardboard sheet. [Figure 7] This figure illustrates the positioning of a corrugated cardboard sheet of a different size than that shown in Figure 6, in the width direction of the first and second regions. [Figure 8] This diagram illustrates the timing of photography during the transportation of cardboard sheets. [Figure 9] This diagram illustrates how the widthwise displacement of the corrugated cardboard sheet is suppressed in the folding section. [Figure 10] This diagram illustrates the folding and joining process and the occurrence of defective products due to the use of inner lining. [Figure 11] This diagram illustrates the folding and joining process using external adhesive, and the occurrence of defective products. [Modes for carrying out the invention]

[0027] Hereinafter, a folding joint inspection method and a folding joint inspection apparatus 1 used in this folding joint inspection method, which are embodiments of one embodiment of the present invention, will be described with reference to Figures 1 to 9.

[0028] The folding joint inspection device 1 mainly consists of a digital camera 21 that photographs a predetermined area (details described later) at the joint of the joint piece in the box-making line, and a computer 40 that performs a determination process to determine whether or not the folding joint has been properly performed based on the two-dimensional image acquired by the digital camera 21.

[0029] The box-making line is a box-making line in a box-making machine (folder gluer) (see Figure 1). The corrugated cardboard sheet 10 (blank) is formed by laminating a corrugated core paper with front and back liners, then creating horizontal lines, vertical lines, and notches, forming seam allowances 15, and cutting the sheet. As the sheet is transported, glue is applied to the seam allowances 15. A folding section 91 gradually folds the corrugated cardboard sheet 10 and joins the seam allowances 15 to form a cylindrical shape. A counter-ejector section 92 counts and discharges the folded corrugated cardboard sheets 10. Note that the box-making machine may be a flexographic folder gluer, which is a combined machine with a flexographic printing press. Here, the folding section 91 corresponds to the "folding and joining section" of the present invention, and the counter-ejector section 92 corresponds to the "discharge section" of the present invention. Also, in Figure 1, the transport direction of the corrugated cardboard sheet 10 in the box-making line is indicated by arrow F, and this is the same in other figures.

[0030] The corrugated cardboard sheet is of the "Type A" (JIS Z1507 "Type 0201"), and the four sides that make up the sides of the corrugated cardboard box are designated as the first side 11, second side 12, third side 13, and fourth side 14, in order from the side adjacent to the seam strip 15. In the corrugated cardboard sheet 10 that has become cylindrical after passing through the folding section 91, the fourth side 14 is joined to the seam strip 15. When the seam strip 15 is joined (adhered) to the inner surface of the fourth side 14, it is called "internal bonding," and when the seam strip 15 is joined (adhered) to the outer surface of the fourth side 14, it is called "external bonding." In the Type A corrugated cardboard sheet 10, the widthwise length L1 of the first side 11 and the widthwise length L3 of the third side 13 are equal, and the widthwise length L2 of the second side 12 and the widthwise length L4 of the fourth side 14 are equal.

[0031] As shown in Figure 1, the digital camera 21 is positioned in the box-making line between the folding section 91 and the counter-ejector section 92, at a position away from the corrugated cardboard sheet 10 transport path 90 in the direction in which the corrugated cardboard sheet 10 is folded. In the folding section 91 of this embodiment, the corrugated cardboard sheet 10 is folded downwards, so the digital camera 21 is positioned below the transport path 90 of the corrugated cardboard sheet 10.

[0032] As the digital camera 21, a two-dimensional camera (area camera) or a line sensor camera can be used. In the case of a line sensor camera that acquires one-dimensional images, the scanning period (the time it takes to store the signal for one line) is generally much shorter than that of a two-dimensional camera. Therefore, one-dimensional images can be continuously acquired as the corrugated cardboard sheet 10 moves at high speed, and a two-dimensional image can be formed (combined) at high speed by arranging the one-dimensional images acquired within a predetermined time.

[0033] Furthermore, in this embodiment, an arrival detection sensor 22 for detecting the arrival of the corrugated cardboard sheet 10 is placed between the folding unit 91 and the counter-ejector unit 92. As the arrival detection sensor 22, a photoelectric sensor can be used to detect the presence or absence of the corrugated cardboard sheet 10 by projecting light onto the transport path 90 of the corrugated cardboard sheet 10 and receiving reflected or transmitted light, or an ultrasonic sensor can be used to detect the presence or absence of the corrugated cardboard sheet 10 by irradiating ultrasonic waves onto the transport path 90 of the corrugated cardboard sheet 10 and receiving reflected or transmitted waves. Figure 1 illustrates a case where the arrival detection sensor 22 is placed in the opposite direction to the direction in which the corrugated cardboard sheet is folded and at a position away from the transport path 90 of the corrugated cardboard sheet 10. However, the arrival detection sensor 22 may be installed on the same side of the transport path 90 as the digital camera 21, as long as it does not interfere with the digital camera 21 or other components.

[0034] Furthermore, in the mechanical configuration of the box-making line, an encoder 23 is attached to a rotating part that is synchronized with the drive unit that drives the transport of the corrugated cardboard sheets 10. Here, an example is given in which the encoder 23 is attached to a roller 80b that rotates with the transport belt 80 that transports the corrugated cardboard sheets 10 while folding them in the folding unit 91, but the attachment location is not limited to this place as long as it is a part that is synchronized for the transport of the corrugated cardboard sheets 10. The signal from the encoder 23 is sent to the computer 40. Based on the signal sent from the encoder 23, the transport speed of the corrugated cardboard sheets 10, the distance traveled by the corrugated cardboard sheets 10 in a predetermined time, and the time required for the corrugated cardboard sheets 10 to travel the predetermined distance can be determined.

[0035] The computer 40 comprises a storage device consisting of a main memory and an auxiliary storage device, and a central processing unit (CPU) that performs processing according to programs stored in the storage device. The storage device stores a determination processing program that causes the computer 40 to function as a determination means 42 that determines whether or not the folding and joining is performed correctly based on a two-dimensional image acquired by the digital camera 21. Furthermore, if the digital camera 21 is a line sensor camera, the storage device also stores an image synthesis processing program that causes the computer 40 to function as an image synthesis means that forms a two-dimensional image from a one-dimensional image captured by the line sensor camera.

[0036] The storage device can store information such as whether the corrugated cardboard sheets 10 folded and joined on the box-making line are lined on the inside or outside, corrugated cardboard information including size information regarding the widthwise lengths L1, L2, L3, L4, and L5 of the first surface 11, second surface 12, third surface 13, fourth surface 14, and the joint pieces 15, and the results of the determination process to determine whether the folding and joining is done properly. The storage device can also store two-dimensional images acquired based on images taken from the digital camera 21, and if the digital camera 21 is a line sensor camera, it can store the one-dimensional image data transmitted from the digital camera 21 together with the combined two-dimensional image data.

[0037] Furthermore, the folding joint inspection device 1 is equipped with output devices 25 such as a monitor or printer to display the processing process and results by the computer 40, and input devices 24 such as a keyboard or pointing device to input various commands and cardboard information to the computer 40. In addition, the folding joint inspection device 1 is equipped with an alarm device 26 that notifies the occurrence of an abnormality with an alarm light or alarm sound if it is determined that the folding joint has not been performed properly.

[0038] Furthermore, the computer 40 in this embodiment is connected to the production management device 27 of the box-making line and the manufacturer's office computer 28 via wired or wireless communication. The office computer 28 can input corrugated cardboard information and judgment criteria values ​​to the computer 40, and the computer 40 can transmit the processing process and results of the processing to the office computer 28. Alternatively, the corrugated cardboard information and judgment criteria values ​​can be transmitted from the office computer 28 to the production management device 27, where they are stored and then transmitted from the production management device 27 to the computer 40.

[0039] Next, a folding joint inspection method performed using the folding joint inspection device 1 with the above configuration will be described. In this embodiment, the folding joint inspection method acquires a two-dimensional image of a predetermined area at the joint between the splice piece 15 and the fourth surface 14 of the corrugated cardboard sheet 10 after folding and joining, and performs image processing to detect whether the splice piece 15 is inside or outside the fourth surface 14 based on at least one of whether the edge 14e of the fourth surface 14 is detected as an edge, and whether the edge 15e of the splice piece 15 is detected as an edge, and determines whether the folding joint has been properly performed based on this.

[0040] As shown in Figures 3(a) and 3(b), a two-dimensional image is acquired of the first region 32a of the folded and joined corrugated cardboard sheet 10, which includes at least a portion of the area where the edge 14e of the fourth surface 14 overlaps with the splice piece 15. Here, the case where the area 30 including the first region 32a is photographed and a two-dimensional image 31 is acquired is illustrated.

[0041] When an edge E1 is detected by image processing of the first region 32a, as shown in the enlarged view of the two-dimensional image in Figure 3(a), this edge E1 is the edge 14e of the fourth surface 14. In other words, in the first region 32a, the splice piece 15 is inside the fourth surface 14. Therefore, if this condition is detected when the inner lining is being applied on the box-making line, it can be determined that the folding and joining is done correctly, and if this condition is detected when the outer lining is being applied on the box-making line, it can be determined that the folding and joining is not done correctly in the inner lining state.

[0042] On the other hand, when image processing is performed on the first region 32a, if no edge is detected as shown in the enlarged view of the two-dimensional image in Figure 3(b), then the splice piece 15 is outside the fourth surface 14 in the first region 32a. Therefore, if this condition is detected when the outer layer is being attached on the box-making line, it can be determined that the folding and joining is done correctly, and if this condition is detected when the inner layer is being attached on the box-making line, it can be determined that the folding and joining is not done correctly in the outer layer state.

[0043] Edge detection can be performed by determining whether the areas where the grayscale values ​​of pixels constituting a two-dimensional image change discontinuously are continuous in a linear fashion of a predetermined length or longer. A reference value (threshold) can be set for the difference in grayscale values ​​that constitutes a discontinuous difference, and for the length used to determine whether or not it is linear.

[0044] The region for edge detection is defined as a first region 32a, which includes at least a portion of the area where the edge 14e of the fourth surface 14 overlaps with the splice piece 15, as described above. Alternatively, as shown in Figures 4(a) and 4(b), it can be defined as a second region 32b, which includes at least a portion of the area where the edge 15e of the splice piece 15 overlaps with the fourth surface 14. Here, the figure shows the case where a range 30 including the second region 32b is photographed and a two-dimensional image 31 is obtained, similar to the above.

[0045] If, after image processing of the second region 32b, no edge is detected as shown in the enlarged view of the two-dimensional image in Figure 4(a), then the splice piece 15 is located inside the fourth surface 14 in the second region 32b. Therefore, if this condition is detected when the inner lining is being applied on the box-making line, it can be determined that the folding and joining is done correctly. If this condition is detected when the outer lining is being applied on the box-making line, it can be determined that the folding and joining is not done correctly in the inner lining state.

[0046] On the other hand, when image processing is performed on the second region 32b, if an edge E2 is detected as shown in the enlarged view of the two-dimensional image in Figure 4(b), this edge E2 is the edge 15e of the splice piece 15 that has been detected. In other words, in the second region 32b, the splice piece 15 is outside the fourth surface 14. Therefore, if this condition is detected when the outer layer is being attached on the box-making line, it can be determined that the folding and joining is done correctly, and if this condition is detected when the inner layer is being attached on the box-making line, it can be determined that the folding and joining is not done correctly and the outer layer is being attached incorrectly.

[0047] As described above, whether or not the folding and joining is done properly can be determined by either edge detection in the first region 32a or edge detection in the second region 32b. However, as shown in Figures 5(a) and (b), it is also possible to determine whether or not the folding and joining is done properly by edge detection in both the first region 32a and the second region 32b. As shown in Figure 5(a), when the inner lining is done properly, as shown in the enlarged view of the two-dimensional image, when the image is processed, edge E1 is detected in the first region 32a and no edge is detected in the second region 32b. Therefore, when the inner lining is done on the box-making line, and no edge is detected in the first region 32a but edge E2 is detected in the second region 32b, it can be determined that the outer lining is not properly folded and joined.

[0048] On the other hand, as shown in Figure 5(b), when the outer covering is properly applied, as shown in the enlarged view of the two-dimensional image, no edge is detected in the first region 32a when the image is processed, but edge E2 is detected in the second region 32b. Therefore, when the outer covering is applied on the box-making line, and edge E1 is detected in the first region 32a but no edge is detected in the second region 32b, it can be determined that the inner covering is not properly folded and joined.

[0049] When making a determination using both the first region 32a and the second region 32b, if the area 30 captured by the digital camera 21 is defined to encompass these two regions 32a and 32b, then a determination based on the presence or absence of two edge detections can be made in a single two-dimensional image 31.

[0050] In the width direction of the corrugated cardboard sheet 10, the positions where the first region 32a and the second region 32b are set differ depending on the size of the corrugated cardboard sheet. Therefore, a method for setting the positions of the first region 32a and the second region 32b in the width direction based on the size information included in the corrugated cardboard information (information regarding the width directions of the first surface 11, second surface 12, third surface 13, fourth surface 14, and the seam allowance pieces 15, respectively) will be explained.

[0051] Regardless of size, the Type A corrugated cardboard sheet 10 is transported with the position of the notch groove (slot) between the second side 12 and the third side 13 aligned with the machine center C of the box-making line. Here, with respect to the machine center C, the side with the second side 12 is described as the right direction, and the side with the third side 3 is described as the left direction.

[0052] As shown in Figure 6, if the widthwise length L3 of the third surface 13 is longer than the widthwise length L4 of the fourth surface 14, the widthwise center position in the first region 32a is set to a position "L3-L4" away to the left from the machine center C (see the middle diagram in Figure 6). If length L4 is equal to length L3, the widthwise center position in the first region 32a coincides with the machine center C.

[0053] On the other hand, the center position in the width direction of the second region 32b is set to a position "L1-L2+L5" away to the left of the machine center C, or to a position "L3-L4+L5" away to the left of the machine center C (see the lower diagram in Figure 6).

[0054] Furthermore, as shown in Figure 7, if the widthwise length L3 of the third surface 13 is shorter than the widthwise length L4 of the fourth surface 14, the widthwise center position in the first region 32a is set to a position "L4-L3" away to the right from the machine center C (see the middle diagram in Figure 7). On the other hand, the widthwise center position in the second region 32b is set to a position "L2-L1-L5" away to the right from the machine center C, or to a position "L4-L3-L5" away to the right from the machine center C (see the bottom diagram in Figure 7).

[0055] In the settings based on the size of the corrugated cardboard sheet 10 as described above, if the first region 32a or the second region 32b is the shooting range of the two-dimensional camera, the optical axis of the two-dimensional camera is set at the center position in the width direction of the first region 32a and the second region 32b, respectively, as set in this manner. If the first region 32a or the second region 32b is the shooting range of the line sensor camera, the centers of the image sensors arranged in the width direction of the corrugated cardboard sheet 10 are aligned with the center position in the width direction of the first region 32a and the second region 32b, respectively. Alternatively, a line sensor camera with image sensors arranged along the entire width direction is used, and the settings are made to acquire images from the line sensor camera over a predetermined length range on both the left and right sides from the center position in the width direction of the first region 32a and the second region 32b, respectively, or to make the images of that range the target of edge detection. If the shooting range is wider than the first region 32a or the second region 32b, the shooting range is set based on the positional and size relationship between the first region 32a or the second region 32b and the range 30. Although Figures 6 and 7 illustrate the case of interior lining, the positional settings in the width direction of the first region 32a, the second region 32b, and the range 30 are the same even in the case of exterior lining.

[0056] Thus, when the size of the corrugated cardboard sheet 10 differs, the center position in the width direction in the first region 32a and the second region 32b shifts, making it necessary to change the installation position of the digital camera 21 in the width direction. Therefore, the folding and joining inspection device 1 is equipped with a mechanism to shift the position of the digital camera 21 in the width direction of the corrugated cardboard sheet 10 (in the direction perpendicular to the transport path 90), and moves the digital camera 21 in the width direction when the size of the corrugated cardboard box to be manufactured is changed. Examples of mechanisms for shifting the position of the digital camera 21 in the width direction include a mechanism using a ball screw, a mechanism using a rack and pinion, and a mechanism using a cylinder rod.

[0057] The timing of the digital camera 21's shooting can be set to take pictures at predetermined time intervals based on the transport speed of the corrugated cardboard sheets 10, the length of the corrugated cardboard sheets 10 in the transport direction F, and the spacing between the corrugated cardboard sheets 10 in the transport direction F. In addition, since the folding joint inspection device 1 is equipped with an arrival detection sensor 22, the timing of the digital camera 21's shooting can be determined based on the detection by the arrival detection sensor 22.

[0058] Specifically, as shown in Figure 8, if La is the length (height) of the front flap of the corrugated cardboard sheet 10 and Lb is the depth of the corrugated cardboard box formed by the corrugated cardboard sheet 10, then the center position in the transport direction F of each of the first region 32a, the second region 32b, or range 30 is a distance of "La + (Lb / 2)" from the front edge 10f of the corrugated cardboard sheet 10. Therefore, if the first region 32a, the second region 32b, or range 30 is the shooting range of the two-dimensional camera, then shooting is performed when the corrugated cardboard sheet 10 has advanced a distance of "La + (Lb / 2)" from the moment the arrival detection sensor 22 detects the front edge 10f of the corrugated cardboard sheet 10 in the transport direction F.

[0059] On the other hand, if the first region 32a, the second region 32b, or range 30 is the shooting range of the line sensor camera, and the length of that shooting range in the transport direction F is N, then the acquisition of a one-dimensional image starts from the point when the arrival detection sensor 22 detects the front edge 10f of the corrugated cardboard sheet 10, and then from the point when the corrugated cardboard sheet 10 has advanced by a length "La + (Lb / 2)", and then from the point when the time it takes for the corrugated cardboard sheet 10 to move by a length of N is reversed. Subsequently, the one-dimensional images acquired during the time it takes for the corrugated cardboard sheet 10 to move by a length of N are combined to form a two-dimensional image.

[0060] In this way, by determining the timing of the digital camera 21 to take pictures based on the detection of the front edge 10f by the arrival detection sensor 22 and the signal from the encoder 23, the timing of the digital camera 21 to take pictures can be set appropriately and quickly even if the length and spacing of the corrugated cardboard sheets 10 in the transport direction F changes due to a change in the size of the corrugated cardboard box being manufactured, or if the transport speed of the corrugated cardboard sheets 10 in the box-making line changes.

[0061] As described above, according to this embodiment, for the corrugated cardboard sheet 10 after it has been joined into a cylindrical shape, a two-dimensional image of at least one of the following is obtained: a first region 32a, which is at least a part of the portion where the edge 14e of the fourth surface 14 and the splice piece 10 overlap; and a second region 32b, which is at least a part of the portion where the edge 15e of the splice piece 15 and the fourth surface 14 overlap; or a two-dimensional image of the range 30 including the first region 32a or the second region 32b. By detecting whether or not an edge is detected in the image processing of at least one of the first region 32a or the second region 32b, it is possible to detect whether or not the splice piece 15 is inside or outside the fourth surface 14, and to easily determine whether or not the splice piece 15 has been properly joined to the fourth surface 14 by adhesion.

[0062] In the folding section 91, where the corrugated cardboard sheet 10 is transported and folded, as shown in Figure 9, the corrugated cardboard sheet 10 is transported while being held between the transport belt 80 from above and below. Furthermore, folding guides 81 are placed between the second surface 12 and the first surface 11, and between the third surface 13 and the fourth surface 14, which are the folding points. The folding transport belt 82 transports and pushes down the first surface 11 and the fourth surface 14, gradually folding the corrugated cardboard sheet 10 along the folding guides 81. Moreover, even after folding, the corrugated cardboard sheet 10 is transported while being held between the transport belt 80 and the folding transport belt 82 from above and below. Therefore, in the folding section 91, the corrugated cardboard sheet 10 hardly shifts in the width direction. Consequently, there is no risk of misidentifying whether the edge detected in the first region 32a or the second region 32b is the edge 14e of the fourth surface 14 or the edge 15e of the splice piece 15.

[0063] Then, based on edge detection, if an outer-lining state is detected in the box-making line despite inner lining being performed, or if an inner-lining state is detected despite outer lining being performed, the determination means 42, which has determined that the folding and joining is not done properly, sends a defect detection signal to the alarm device 26, and the alarm device 26 makes an announcement. At the same time, information identifying the defective corrugated cardboard sheet 10, for example, information indicating which number the defective item is among the multiple corrugated cardboard sheets 10 stacked on the counter-ejector unit 92, is output to the output device 25, and the defective item is removed based on this output.

[0064] Although preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various improvements and design changes are possible without departing from the spirit of the present invention, as shown below.

[0065] For example, although the corrugated cardboard sheet to be judged in this invention is of type A, the present invention can also be applied to corrugated cardboard sheets that are formed through a die-cutting process, as long as they have the same shape as type A corrugated cardboard sheets. [Explanation of symbols]

[0066] 1. Folding joint inspection device 10 cardboard sheets 14 Fourth side 14e Edge (Edge of the fourth face) 15 splice pieces 15e Edge (edge ​​of the splice piece) 21 Digital Cameras 22 Arrival detection sensor 23 encoders 30 range 31 Two-dimensional images 32a First area 32b Second area 90 Conveyor paths 91 Folding section (folding joint) 92 Counter Ejector Section (Discharge Section) E1, E2 Edge

Claims

1. In a box-making line, a digital camera is positioned between a folding and joining section where corrugated cardboard sheets, glued to the joint pieces, are gradually folded and joined into a cylindrical shape, and a discharge section where the folded corrugated cardboard sheets are discharged and stacked, at a location isolated from the corrugated cardboard sheet transport path in the direction in which the corrugated cardboard sheets are folded. When the side of the tubular corrugated cardboard sheet that is joined to the splice is designated as the fourth side, The digital camera acquires a two-dimensional image of the first region, which includes at least a portion of the area where the edge of the fourth surface and the splice overlap. The presence or absence of edge detection in the image processing of the two-dimensional image of the first region determines whether the splice is inside or outside the fourth surface, thereby determining whether the folding and joining is performed correctly. The edge detection is performed by detecting linear edges where the grayscale values ​​of pixels constituting the two-dimensional image change discontinuously, and these edges are continuous for a predetermined length or longer. The edge detected in the first region is the edge of the fourth face. When an edge is detected in the first region, the splice is determined to be inside the fourth face. If no edge is detected in the first region, the splice is determined to be outside the fourth face. A folding joint inspection method characterized by the following.

2. In a box-making line, a digital camera is positioned between a folding and joining section where corrugated cardboard sheets, glued to the joint pieces, are gradually folded and joined into a cylindrical shape, and a discharge section where the folded corrugated cardboard sheets are discharged and stacked, at a location isolated from the corrugated cardboard sheet transport path in the direction in which the corrugated cardboard sheets are folded. When the side of the tubular corrugated cardboard sheet that is joined to the splice is designated as the fourth side, The digital camera acquires a two-dimensional image of the second region, which includes at least a portion of the area where the edge of the splice piece and the fourth surface overlap. The presence or absence of edge detection in the image processing of the two-dimensional image of the second region determines whether the splice is inside or outside the fourth surface, thereby determining whether the folding and joining is performed correctly. Edge detection is performed by detecting linear edges where the grayscale values ​​of pixels constituting a two-dimensional image change discontinuously, and these edges are continuous for a predetermined length or longer. The edge detected in the second region is the edge of the splice piece. When an edge is detected in the second region, the splice piece is determined to be outside the fourth surface. If no edge is detected in the second region, the splice piece is determined to be inside the fourth surface. A folding joint inspection method characterized by the following.

3. The timing for taking a picture with the digital camera is determined based on the detection of the front edge of the corrugated cardboard sheet by the arrival detection sensor and a signal transmitted from an encoder provided on a rotating part synchronized with the drive unit that drives the transport of the corrugated cardboard sheet. A folding joint inspection method according to claim 1 or 2.

Images