JP4890333B2 - Thread shape inspection method and thread shape inspection device - Google Patents

Description

  The present invention relates to a method for inspecting the shape of a thread formed on a bottle can and the like, and more specifically, a method for inspecting the symmetry of the cross-sectional shape of the thread as the shape of the thread, and the inspection apparatus. The present invention relates to a bottle can manufacturing method and a bottle can manufacturing apparatus.

  As a product having a threaded portion, for example, a cap threaded male threaded portion is formed in a base portion of a beverage metal bottle can. Such a bottle can is generally manufactured using a DI can made of aluminum (including an alloy thereof) as a base. This DI can is formed with a bottomed cylinder by drawing and ironing with an aluminum plate as the starting material, and then necking, screwing, curling at the opening side end. A plurality of processes such as a process are performed to form a reduced-diameter base portion having a male screw portion.

  Thereafter, a predetermined inspection is performed on the thread shape of the base part, and the bottle can that has passed this inspection is filled with the contents, and then the base part is covered with a cap and sealed to obtain a bottle can with a cap.

As a method for inspecting the screw thread of the base part, for example, Japanese Patent Laid-Open No. 2003-254720 discloses a method for measuring and inspecting the height of the screw thread, the outer diameter of the screw thread, etc., and Japanese Patent Laid-Open No. 2003-262507. Japanese Patent Laid-Open No. 2003-262511 discloses a method for measuring and inspecting a screw start portion of a screw portion (see Patent Documents 1-3).
JP 2003-254720 A JP 2003-262507 A JP 2003-262511 A

  Thus, for the screw part of the cap part of the bottle can, even when the height of the thread, the outer diameter of the thread, and the screw start part are inspected, In some cases, cracks occurred and the contents leaked out.

  The present invention has been made in view of the above-described technical background, and an object of the present invention is to provide a thread shape inspection method and an inspection apparatus for discovering a shape of a thread part that is easily broken, a bottle can manufacturing method, and the same. It is to provide a manufacturing apparatus.

  The present inventors investigated the cause of the cracking of the screw part as described above. When forming the screw part in the base part, when the adjustment accuracy of the screw sesame is incomplete, the cross section of the screw thread It has been discovered that the screw part is cracked when or after the cap is attached because the shape is asymmetric with respect to the axis passing through the apex and the thickness of the screw becomes uneven. Based on this knowledge, the present inventors have completed the following invention.

[1] An imaging process for imaging the thread contour;
A contour calculating step for calculating a thread contour based on the imaging data obtained in the imaging step;
A temporary vertex position setting step of setting any one position on the contour calculated in the contour calculation step as a temporary vertex position of the thread;
A plurality of sets of positions on a pair of contour lines that are equidistant from the temporary vertex position on the contour line set in the provisional vertex position setting step on both sides in the width direction of the screw thread are determined, and each pair of positions on the pair of contour lines A height difference calculating step of calculating a difference in height of the contour line in
An evaluation value calculation step of calculating an evaluation value related to the degree of symmetry of the cross-sectional shape of the screw thread based on the calculation result of the height difference calculation step;
The temporary vertex position setting step, the height difference calculating step, and the evaluation value calculating step are changed by changing the temporary vertex position set in the temporary vertex position setting step to a different position each time and sequentially repeating a plurality of times. An iterative process for obtaining an evaluation value of
An evaluation value selection step of selecting the best evaluation value among a plurality of evaluation values obtained in the repetition step;
A thread shape inspection method comprising: a determination step of determining whether or not the cross-sectional shape of the thread is symmetrical based on the best evaluation value selected in the evaluation value selection step.

[2] The imaging step is to image the contours of a plurality of screw threads,
Further, for each imaging data obtained in the imaging step, the contour calculation step, the provisional vertex position setting step, the height difference calculation step, the evaluation value calculation step, the repetition step, and the evaluation value selection step are performed. By performing an evaluation value acquisition step for acquiring the best evaluation value for each imaging data,
2. The thread shape inspection according to claim 1, wherein the determination step determines whether or not the degree of symmetry of the cross-sectional shape of the screw thread is good based on the best evaluation value acquired for each imaging data in the evaluation value acquiring step. Method.

[3] In the evaluation value calculating step, the evaluation value A is calculated by the following equation (1):
3. The thread shape inspection method according to item 1 or 2, wherein the evaluation value selection step selects a minimum evaluation value as the best evaluation value among a plurality of evaluation values.

_{^{A = √ {Σ n i =}} 1 (ΔY i) 2} ... formula (1)
However,
n: number of groups ΔY _i : height difference of i-th group [4] The thread shape inspection method according to any one of the preceding items 1 to 3, wherein the thread is formed in a base portion of a bottle can.

[5] Imaging means for imaging the thread contour;
Contour calculating means for calculating the thread contour based on the imaging data obtained by the imaging means;
A temporary vertex position setting means for setting an arbitrary one position on the contour calculated by the contour calculation means as a temporary vertex position of the thread;
A plurality of pairs of positions on a pair of contour lines that are equidistant and separated on both sides in the width direction of the thread from the temporary vertex position on the contour line set by the provisional vertex position setting means are determined, and each pair of positions on the pair of contour lines A height difference calculating means for calculating a difference in height of the contour line in
Evaluation value calculation means for calculating an evaluation value related to the degree of symmetry of the cross-sectional shape of the screw thread based on the calculation result of the height difference calculation means;
By repeating the process by the temporary vertex position setting means, the height difference calculating means, and the evaluation value calculating means by sequentially changing the temporary vertex position set by the temporary vertex position setting means to a different position each time and sequentially repeating a plurality of times. Repetitive means for obtaining a plurality of evaluation values;
Evaluation value selection means for selecting the best evaluation value among a plurality of evaluation values obtained by the repetition means;
A thread shape inspection apparatus comprising: determination means for determining whether or not the degree of symmetry of the cross-sectional shape of the thread is good based on the best evaluation value selected by the evaluation value selection means.

[6] The imaging means is for imaging the outline of a plurality of screw threads,
Further, for each imaging data obtained by the imaging unit, the contour calculation unit, the provisional vertex position setting unit, the height difference calculation unit, the evaluation value calculation unit, the repetition unit, and the evaluation value selection unit By performing the processing, comprising an evaluation value acquisition means for acquiring the best evaluation value for each imaging data,
The thread shape according to claim 5, wherein the determination means determines whether or not the symmetry of the cross-sectional shape of the thread is good based on the best evaluation value acquired for each imaging data by the evaluation value acquisition means. Inspection device.

[7] The evaluation value calculation means calculates the evaluation value A by the following equation (1):
The thread shape inspection device according to claim 5 or 6, wherein the evaluation value selection means selects a minimum evaluation value as the best evaluation value among a plurality of evaluation values.

_{^{A = √ {Σ n i =}} 1 (ΔY i) 2} ... formula (1)
However,
n: number of groups ΔY _i : height difference of i-th group [8] The thread shape inspection device according to any one of the preceding items 5 to 7, wherein the thread is formed in a cap portion of a bottle can.

[9] In a manufacturing method of a bottle can that obtains a bottle can through a screw thread inspection process for inspecting a screw thread formed on a cap portion of the bottle can.
In the screw thread inspection step, the method for manufacturing a bottle can characterized by inspecting the degree of symmetry of the cross-sectional shape of the thread as the thread inspection by the thread shape inspection method according to any one of 1 to 4 above. .

[10] In a bottle can manufacturing apparatus provided with a screw thread inspection device for inspecting a screw thread formed on a cap portion of a bottle can,
An apparatus for manufacturing a bottle can comprising the thread shape inspection apparatus according to any one of items 5 to 8 as the thread inspection apparatus.

  The present invention has the following effects.

  According to the invention of [1], various processes for inspecting the symmetry of the cross-sectional shape of the thread are performed based on the imaging data obtained by imaging the thread contour in the imaging process. Since this is done, the symmetry of the cross-sectional shape of the thread can be inspected without contact. Therefore, this inspection can be easily added to the conventional thread inspection line.

  Further, in the repetition process, a plurality of evaluation values are obtained by sequentially repeating the provisional vertex position setting process, the height difference calculation process, and the evaluation value calculation process a plurality of times, and then, in the evaluation value selection process, obtained in this repetition process. The best evaluation value is selected from the plurality of evaluation values. In the determination step, the quality of the cross-sectional shape of the thread is determined based on the best evaluation value selected in the evaluation value selection step. It can be performed. Therefore, for example, when a corresponding cap is attached to a thread portion having a thread that has been determined to be non-defective in this determination step, cracks in the screw portion that may occur during or after the cap is attached Can be prevented.

  According to the invention of [2], the contours of a plurality of screw threads are imaged in the imaging process, and the best evaluation value is acquired for each imaging data obtained in the imaging process in the evaluation value acquisition process. In the determination step, the quality of the cross-sectional shape of the thread is determined based on the best evaluation value acquired for each imaging data in the evaluation value acquiring step. More accurate pass / fail judgment can be made. Therefore, it is possible to reliably prevent cracking of the thread portion that may occur during or after the cap is attached.

  According to the invention of [3], it is possible to calculate an appropriate evaluation value regarding the degree of symmetry of the cross-sectional shape of the thread. Therefore, in the determination step, it is possible to perform a more accurate pass / fail determination regarding the degree of symmetry of the cross-sectional shape of the thread.

  According to the invention of [4], accurate pass / fail determination can be made with respect to the degree of symmetry of the cross-sectional shape of the thread formed on the cap portion of the bottle can. Therefore, it is possible to prevent cracking of the thread portion that may occur when the cap is attached to the cap portion of the bottle can or after the cap is attached.

  According to the inventions [5] to [8], it is possible to provide a thread shape inspection apparatus capable of performing the thread shape inspection method according to the inventions [1] to [4].

  According to the invention [9], it is possible to provide a method for manufacturing a bottle can having the same effects as any of the inventions [1] to [4].

  According to the invention [10], it is possible to provide a bottle can manufacturing apparatus that exhibits the same effects as those of any one of the inventions [1] to [4].

  Next, an embodiment of the present invention will be described below with reference to the drawings.

  In FIG. 1, (20) is a thread shape inspection apparatus according to an embodiment of the present invention. This inspection device (20) includes, as the shape of the thread (32) formed on the outer peripheral surface of the cylindrical mouthpiece (31) of the bottle can (30), the degree of symmetry of the cross-sectional shape of the thread (32), That is, it is an apparatus for examining the degree of symmetry with respect to the axial center passing through the apex in the cross-sectional shape of the screw thread (32).

  The bottle can (30) is made of metal, and more specifically, is mainly based on a DI can made of aluminum (including its alloy). For example, beverages (coffee, tea, carbonated beverages, beer, etc.) are accommodated in the bottle can (30). The number of turns of the thread (32) formed on the outer peripheral surface of the base (31) of the bottle can (30) is plural, for example, two to three.

  As shown in FIG. 1, the thread shape inspection apparatus (20) of this embodiment includes a rotation holding means (21), an imaging means (1), an illumination means (12), a calculation means (10), and a display means (11). ) As a basic component.

  The rotation holding means (21) holds the bottle can (30) so that the axis (P) thereof is horizontal and is rotatable about the axis (P).

  The imaging means (1) is a screw thread closest to the top surface of the base part (31) among the plurality of wound threads (32) formed on the outer peripheral surface of the base part (31) of the bottle can (30). The contour of (32) is imaged as a silhouette of the thread (32). The imaging means (1) is composed of, for example, an area camera, and more specifically, a CCD area camera having a predetermined number of pixels.

  The illuminating means (12) continuously illuminates the screw thread (32), so that the outline of the screw thread (32) can be easily understood when the image pick-up means (1) images the outline of the screw thread (32). belongs to. This illumination means (12) consists of LED illumination, for example.

  The imaging means (1) and the illuminating means (12) are sandwiched between the thread (32) to be imaged of the base (31) of the base (31) of the bottle can (30) held horizontally by the rotation holding means (21). Arranged on the opposite side, in this embodiment, the imaging means (1) and the illumination means (12) are arranged in a fixed state below and above the base part (31), respectively. Further, the image pickup means (1) has one direction (X direction) of the two directions in which pixels in the image pickup area are arranged orthogonally to each other (that is, the X direction and the Y direction) in the width direction of the thread (32). So that the other direction (Y direction) is along the height direction of the thread (32).

  And this imaging means (1) has the outline of the several places of the thread (32) of the nozzle | cap | die part (31) of the bottle can (30) rotated by predetermined rotation speed by the rotation holding means (21). It is supposed to be imaged. More specifically, in this embodiment, the bottle can (30) is rotated around the axis (P) by the rotation holding means (21), for example, at a rotation speed of about 1000 rpm, and the imaging means (1) The contour of the screw thread (32) is continuously imaged in time, and image data relating to the contour line of the screw thread (32) imaged by the imaging means (1) is, for example, about every 24 ms (ie, about 144 °). Every time), a predetermined process is performed by repeatedly taking it into the contour calculation means (2) of the calculation means (10) described later. Therefore, as shown in FIG. 2, in this embodiment, the imaging means (1) causes the outline of the thread (32) to be 72 in the direction in which the thread (32) extends (that is, the circumferential direction of the base part (31)). A total of eight locations are imaged at intervals of °, and each image data is taken into the contour calculation means (2) of the calculation means (10). In FIG. 2, the numbers with circles indicate the imaging order. However, among the eight imaging locations of the screw thread (32), the first and sixth locations, the second and seventh locations, the third location and the eighth location are substantially overlapped with each other, so in practice The image pickup means (1) has picked up the outlines of almost five places of the screw thread (32). Further, these imaging locations are random locations with respect to the position of the screw start portion of the screw thread (32).

  The calculation means (10) performs various processes based on the imaging data related to the outline of the screw thread (32) imaged by the imaging means (1), thereby finally symmetric the cross-sectional shape of the screw thread (32). A pass / fail judgment is made on the degree (more specifically, the degree of symmetry of the profile of the cross section of the thread (32)). The computing means (10) is constituted by a computer having a CPU, a storage unit (ROM, RAM, hard disk, etc.) and the like. In the storage unit, programs and thresholds necessary for performing processing are stored in advance, and data necessary for processing is stored as needed during processing.

  The display means (11) displays the results processed by the computing means (10) (captured image, evaluation value, pass / fail judgment result of the cross-sectional shape of the thread (32), etc.), and a liquid crystal display , Organic EL display, plasma display, CRT, etc.

  The configuration of the calculation means (10) will be described in detail below.

  As shown in FIG. 3, the calculation means (10) includes contour calculation means (2), provisional vertex position setting means (3), height difference calculation means (4), evaluation value calculation means (5), and repetition means. (6) An evaluation value selection means (7), an evaluation value acquisition means (8), and a determination means (9) are provided.

  The contour line calculation means (2) is the imaging data obtained by the imaging means (1) (more specifically, imaging data relating to the contour of each imaging location of the screw thread (32) imaged by the imaging means (1)). Is captured and stored in an imaging data storage unit (not shown), and the outline of the screw thread (32) is calculated based on the stored imaging data.

  The temporary vertex position setting means (3) sets an arbitrary one position on the contour calculated by the contour calculation means (2) as the temporary vertex position of the screw thread (32).

  The height difference calculation means (4) is a position on a pair of contour lines that are equidistant from the temporary vertex position on the contour line set by the temporary vertex position setting means (3) on both sides in the width direction of the screw thread (32). Are determined within a predetermined range in the width direction of the screw thread (32), and the difference in height of the contour line at a position on the pair of contour lines of each pair is calculated.

  The evaluation value calculation means (5) calculates an evaluation value related to the degree of symmetry of the cross-sectional shape of the screw thread (32) based on the calculation result of the height difference calculation means (4).

  The iterative means (6) is a temporary vertex position set by the temporary vertex position setting means (3) by the temporary vertex position setting means (3), the height difference calculating means (4), and the evaluation value calculating means (5). A plurality of evaluation values are obtained by changing the position to a different position each time and sequentially repeating a plurality of times.

  The evaluation value selection means (7) selects the best evaluation value from among the plurality of evaluation values obtained by the repetition means (6).

  The evaluation value acquisition means (8) repeats the provisional vertex position setting means (3), the height difference calculation means (4), the evaluation value calculation means (5), for each piece of imaging data obtained by the imaging means (1). By performing the processing by means (6) and evaluation value selection means (7), the best evaluation value is obtained for each imaging data.

  The determination means (9) determines the quality of the symmetry of the cross-sectional shape of the screw thread (32) based on the best evaluation value acquired for each imaging data by the evaluation value acquisition means (8).

  Next, a thread shape inspection method using the thread shape inspection apparatus (20) of the present embodiment will be described below based on the flowchart shown in FIG.

  In step S1, the illumination means (12) illuminates the plurality of winding threads (32) of the mouthpiece (31) of the bottle can (30) that is held horizontally by the rotation holding means (21). In the state, the imaging means (1) captures the outline of the plurality of locations of the screw thread (32) closest to the top surface of the base (31) among the plurality of screw threads (32). This step S1 is called “imaging process”. Specifically, in this imaging step (S1), as described above, the contour of the screw thread (32) is extended by the imaging means (1) in the direction in which the screw thread (32) extends (that is, the circumferential direction of the base part (31)). A total of 8 images are taken at intervals of 72 °. Next, the process proceeds to step S2.

  4 is an enlarged image of the screw thread (32) imaged by the image pickup means (1) in the image pickup step (S1) (more specifically, the silhouette of the screw thread (32)). Displayed on the display means (11) via (10).

  In step S2, the contour calculation means (2) calculates the contour of the imaging location of the screw thread (32) based on one of the eight imaging data obtained in the imaging step (S1). . This step S2 is referred to as “contour line calculation step”. Specifically, in this contour calculation step (S2), the imaging data obtained in the imaging step (S1) is binarized, and the contour of the imaging location of the screw thread (32) based on this binarized data. Is calculated (extracted) by the contour calculating means (2). Next, the process proceeds to step S3.

  In step S3, an arbitrary position on the contour calculated in the contour calculation step (S2) is set as a temporary vertex position of the screw thread (32) by the temporary vertex position setting means (3). This step S3 is referred to as a “provisional vertex position setting step”.

Here, in this embodiment, for convenience of explanation, as shown in FIG. 4, in the imaging area, the direction in which the pixels are arranged along the width direction of the thread (32) is the X direction, and the height of the thread (32). When the direction in which the pixels are arranged along the direction is the Y direction, the coordinates of the temporary vertex position among the pixel coordinates (X, Y) of the outline of the screw thread (32) are (0, Y ₀ ). Y _j is the value of Y when X = j (where j is an integer), that is, the height of the outline of the thread (32) at the position of X = j. Therefore, Y ₀ is the value of Y when X = 0, that is, the height of the contour line of the thread (32) at the temporary vertex position. The unit of X and Y is a pixel. If an example of the setting method of a temporary vertex position is shown concretely, the highest position in the outline of a thread (32) in an imaging area will be set to a temporary vertex position. Next, the process proceeds to step S4.

  In step S4, a pair of contours that are equidistant from the temporary vertex position on the contour line set in the temporary vertex position setting step (S3) on both sides in the width direction of the screw thread (32) (that is, the -X direction and the + X direction). A plurality of sets of positions on the line are determined within a predetermined range in the width direction of the screw thread (32), and the difference in height of the contour line at the position on the pair of contour lines of each pair is calculated by the height difference calculating means (4). calculate. This step S4 is referred to as a “height difference calculating step”. Here, in the present embodiment, a predetermined range in the width direction of the thread (32) is set to a range of X = −64 to +63. This range corresponds to about 1/2 to about 4/5 times the full width of the thread (32).

In the present embodiment, the number n of sets determined in the height difference calculating step (S4) is 64 sets. Specifically, the set is Y ₀ and Y ₋₁ , Y ₊₁ and Y _−2. , Y ₊₂ and Y ₋₃ ,..., Y ₊₆₃ and Y ₋₆₄ . Then, by the height difference calculation means (4), a value of Y ₀ −Y _−1, a value of Y ₊₁ −Y _−2, a value of Y ₊₂ −Y ₋₃ ,..., Y ₊₆₃ −Y ₋₆₄ Are respectively calculated. Next, the process proceeds to step S5.

  In step S5, based on the calculation result of the height difference calculation step (S4), the evaluation value A regarding the symmetry of the cross-sectional shape of the thread (32) is calculated by the evaluation value calculation means (5) according to the following equation (1). . This step S5 is referred to as an “evaluation value calculation step”.

However, in Formula (1), n is the number of groups and ΔY _i is the height difference of the i-th group. Note that 2 ≦ n.

  In this embodiment, since n = 64 as described above, in the evaluation value calculation step (S5), the evaluation value A is calculated by the evaluation value calculation means (5) by the following equation (2). . Next, the process proceeds to step S6.

  In step S6, the temporary vertex position setting step (S3), the height difference calculating step (S4), and the evaluation value calculating step (S5) are set by the repeating means (6) in the temporary vertex position setting step (S3). A plurality of evaluation values A are obtained by changing the temporary vertex position to a different position each time within a predetermined range in the width direction of the screw thread (32) and repeating the plurality of times sequentially. This step S6 is called “repetition process”.

  In the present embodiment, in this repeating step (S6), the temporary vertex position setting step (S3), the height difference calculating step (S4), and the evaluation value calculating step (S5) are set in the temporary vertex position setting step (S3). A total of 40 evaluation values are obtained by sequentially shifting the temporary vertex positions to be set one by one within the range of the initial temporary vertex positions X = 0 to X = -20 to +19. Therefore, the number of repetitions in this repetition step (S6) is 40 times. Here, the range of X = -20 to +19 corresponds to about 1/6 to about 1/4 times the entire width of the thread (32). In this repeating step (S6), these steps (S3 to S5) are repeated under the condition that the number of sets n is constant (that is, n = 64).

  Specifically, the evaluation value calculation process performed in this repeating step (S6) is as follows. However, in the following formula, for the convenience of explanation, the X coordinate of the first temporary vertex position set in the temporary vertex position setting step (S3) is set to zero.

For example, when the temporary vertex position X set in the temporary vertex position setting step (S3) is −20 (that is, when X = −20), the evaluation value A- ₂₀ is calculated by the following equation (3).

For example, when the temporary vertex position X set in the temporary vertex position setting step (S3) is −19 (that is, when X = −19), the evaluation value A- ₁₉ is calculated by the following equation (4).

For example, when the temporary vertex position X set in the temporary vertex position setting step (S3) is +19 (that is, when X = + 19), the evaluation value A ₊₁₉ is calculated by the following equation (5).

That is, when the temporary vertex position X set in the temporary vertex position setting step (S3) is k (k: integer) (that is, when X = k), the evaluation value _Ak is calculated by the following equation (6). . However, in Equation (6), k = −20, −19, −18,.

  If the number of repetitions is less than 40, the process returns to step S3 (temporary vertex position setting step). On the other hand, if the number of repetitions is 40, the process proceeds to step S7.

  In step S7, the minimum evaluation value is selected by the evaluation value selection means (7) as the best evaluation value among the 40 evaluation values obtained in the repetition step (S6). This step S7 is referred to as “evaluation value selection step”. Next, the process proceeds to step S8.

  In step S8, an outline calculation step (S2), a provisional vertex position setting step (S3), a height difference calculation step (S4), and an evaluation value calculation step (S5) for each piece of imaging data obtained in the imaging step (S1). ), The repetitive step (S6) and the evaluation value selection step (S7) are sequentially performed, whereby the minimum evaluation value is acquired by the evaluation value acquisition means (8) as the best evaluation value for each imaging data. This step S8 is referred to as an “evaluation value acquisition process”.

  In the present embodiment, as described above, in the imaging step (S1), the eight contours of the screw thread (32) are imaged. Therefore, this evaluation value acquisition step (S8) is performed at eight locations of the screw thread (32). As for the imaging data related to the contour, the minimum evaluation value is acquired as the best evaluation value for each imaging data.

  And when the best evaluation value is not acquired for every imaging data, it returns to step S2 (contour calculation process). On the other hand, if the best evaluation value is acquired for each image data, the process proceeds to step S9.

  In step S9, whether or not the symmetry of the cross-sectional shape of the screw thread (32) is good is determined based on the minimum evaluation value acquired as the best evaluation value for each imaging data in the evaluation value acquisition step (S8). This step S9 is referred to as a “determination step”.

  In the present embodiment, in the determination step (S9), the maximum evaluation value or the minimum evaluation value among the total eight minimum evaluation values acquired as the best evaluation values for each imaging data in the evaluation value acquisition step (S8). An average evaluation value obtained by selecting or averaging these eight minimum evaluation values is calculated, and when the evaluation value is less than a predetermined threshold value, a non-defective product (passed) determination is made regarding the degree of symmetry of the cross-sectional shape of the screw thread (32). On the other hand, when the evaluation value is equal to or greater than a predetermined threshold value, a defective product (failed) is determined for the degree of symmetry of the cross-sectional shape of the thread (32).

  The thread shape inspection is completed through the above steps. Thereafter, the bottle can (30) determined to be non-defective by this inspection is transported to the bottle can production line and subjected to a predetermined process for manufacturing the bottle can (30).

  Thus, according to the thread shape inspection method of the present embodiment, the contour of the screw thread (32) is imaged in the imaging step (S1), and the screw thread is based on the imaging data obtained in the imaging step (S1). Since various processes for checking the degree of symmetry of the cross-sectional shape of the mountain (32) are performed, the degree of symmetry of the cross-sectional shape of the screw thread (32) can be inspected without contact. Therefore, this inspection can be easily added to the conventional thread inspection line.

  Furthermore, in the repetition step (S6), a plurality of evaluation values are obtained by sequentially repeating the temporary vertex position setting step (S3), the height difference calculation step (S4), and the evaluation value calculation step (S5), In the evaluation value selection step (S7), the best evaluation value is selected from the plurality of evaluation values obtained in the repetition step (S6). In the determination step (S9), the quality of the cross-sectional shape symmetry of the screw thread (32) is determined based on the best evaluation value selected in the evaluation value selection step (S7). It is possible to accurately determine whether the cross-sectional shape is symmetrical. Therefore, when a cap (not shown) is attached to the cap part (31) formed with the thread (32) determined to be non-defective in the determination step (S9), it occurs when or after the cap is attached. The crack of the thread part which may be prevented can be prevented.

  Further, according to this thread shape inspection method, the contours of a plurality of locations of the thread (32) are imaged in the imaging step (S1), and obtained in the imaging step (S1) in the evaluation value acquisition step (S8). The best evaluation value is acquired for each image data. In the determination step (S9), whether the symmetry of the cross-sectional shape of the screw thread (32) is good or bad is determined based on the best evaluation value acquired for each imaging data in the evaluation value acquisition step (S8). Further, it is possible to perform a more accurate pass / fail judgment on the degree of symmetry of the cross-sectional shape of the screw thread (32). Therefore, it is possible to reliably prevent cracking of the thread portion that may occur during or after the cap is attached.

  Further, the evaluation value calculation step (S5) calculates the evaluation value A by the above formula (1), and the evaluation value selection step (S7) selects the minimum evaluation value as the best evaluation value among a plurality of evaluation values. Therefore, an appropriate evaluation value regarding the degree of symmetry of the cross-sectional shape of the screw thread (32) can be calculated. Therefore, in the determination step (S9), it is possible to perform an even more accurate pass / fail determination regarding the degree of symmetry of the cross-sectional shape of the thread (32).

  Moreover, according to the thread shape inspection apparatus (20) of this embodiment, the thread shape inspection method of this embodiment can be reliably performed.

  Moreover, the manufacturing method of the bottle can which concerns on one Embodiment of this invention is a bottle can (30) through the thread inspection process which test | inspects the thread (32) formed in the nozzle | cap | die part (31) of a bottle can (30). In the thread inspection step, the thread shape (32) is inspected for the degree of symmetry of the cross-sectional shape of the thread (32) by the thread shape inspection method of the present embodiment. is there. Therefore, the manufacturing method of the bottle can of this embodiment has the same effect as the thread shape inspection method of this embodiment.

  A bottle can manufacturing apparatus according to an embodiment of the present invention is an apparatus including a screw thread inspection device that inspects a screw thread (32) formed on a base (31) of a bottle can (30). As a thread inspection apparatus, the thread shape inspection apparatus (20) of this embodiment is provided. Therefore, the bottle can manufacturing apparatus of the present embodiment has the same effects as the thread shape inspection apparatus (20) of the present embodiment.

  Although one embodiment of the present invention has been described above, the present invention is not limited to that shown in the above embodiment, and various modifications can be made.

  For example, in the above-described embodiment, the number of imaging locations of the contour of the screw thread (32) imaged in the imaging step (S1) is 8, but the present invention is not limited to this. Or two or more locations.

  Moreover, in the said embodiment, although the number n of groups determined in a height difference calculation process (S4) is 64 groups, in this invention, it is not limited to this, For example, 8 groups or more, 16 groups It may be more than or 32 sets, or other number of sets.

  Moreover, in the said embodiment, although the repetition frequency repeated at a repetition process (S6) is 40 times, in this invention, it is not limited to this, For example, it may be 10 times or more, or 20 times or more. However, other times may be used.

  Moreover, in the said embodiment, although a thread shape inspection method and an inspection apparatus (20) test | inspect the shape of the thread (32) formed in the nozzle | cap | die part (31) of a bottle can (30), In this invention, it is not limited to this, You may test | inspect the shape of a screw thread (32) about the product in which the screw thread was formed other than a bottle can.

  INDUSTRIAL APPLICABILITY The present invention can be used for a method for inspecting the shape of a screw thread formed on a bottle can or the like and an inspection apparatus therefor.

FIG. 1 is a schematic view showing a thread shape inspection apparatus according to an embodiment of the present invention. FIG. 2 is a view showing an imaging location of a screw thread of a cap portion of a bottle can imaged by an imaging means of the inspection apparatus. FIG. 3 is a block diagram showing the configuration of the inspection apparatus. FIG. 4 is a view for explaining the height difference of the thread contour calculated by the height difference calculating means of the inspection apparatus. FIG. 5 is a flowchart showing steps performed by the inspection apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Imaging means 2 ... Contour line calculation means 3 ... Temporary vertex position setting means 4 ... Height difference calculation means 5 ... Evaluation value calculation means 6 ... Repetition means 7 ... Evaluation value selection means 8 ... Evaluation value acquisition means 9 ... Determination means DESCRIPTION OF SYMBOLS 10 ... Calculation means 11 ... Display means 12 ... Illumination means 20 ... Thread shape inspection apparatus 30 ... Bottle can 31 ... Base part 32 ... Thread

Claims (10)

An imaging process for imaging the thread contour;
A contour calculating step for calculating a thread contour based on the imaging data obtained in the imaging step;
A temporary vertex position setting step of setting any one position on the contour calculated in the contour calculation step as a temporary vertex position of the thread;
A plurality of sets of positions on a pair of contour lines that are equidistant from the temporary vertex position on the contour line set in the provisional vertex position setting step on both sides in the width direction of the screw thread are determined. A height difference calculating step of calculating a difference in height of the contour line in
An evaluation value calculation step of calculating an evaluation value related to the degree of symmetry of the cross-sectional shape of the screw thread based on the calculation result of the height difference calculation step;
The temporary vertex position setting step, the height difference calculating step, and the evaluation value calculating step are changed by changing the temporary vertex position set in the temporary vertex position setting step to a different position each time and sequentially repeating a plurality of times. An iterative process for obtaining an evaluation value of
An evaluation value selection step of selecting the best evaluation value among a plurality of evaluation values obtained in the repetition step;
A thread shape inspection method, comprising: a determination step of determining whether or not the degree of symmetry of the cross-sectional shape of the thread is good based on the best evaluation value selected in the evaluation value selection step. The imaging step is to image the contours of a plurality of screw threads,
Further, for each imaging data obtained in the imaging step, the contour calculation step, the provisional vertex position setting step, the height difference calculation step, the evaluation value calculation step, the repetition step, and the evaluation value selection step are performed. By performing an evaluation value acquisition step for acquiring the best evaluation value for each imaging data,
2. The thread shape according to claim 1, wherein the determination step determines whether or not the symmetry of the cross-sectional shape of the thread is good based on the best evaluation value acquired for each imaging data in the evaluation value acquisition step. Inspection method. The evaluation value calculating step calculates the evaluation value A by the following equation (1):
The thread shape inspection method according to claim 1, wherein the evaluation value selection step selects a minimum evaluation value as the best evaluation value among a plurality of evaluation values.
_{^{A = √ {Σ n i =}} 1 (ΔY i) 2} ... formula (1)
However,
n: number of sets ΔY _i : height difference of i-th set   The thread shape inspection method according to any one of claims 1 to 3, wherein the thread is formed in a cap portion of a bottle can. Imaging means for imaging the thread contour;
Contour calculating means for calculating the thread contour based on the imaging data obtained by the imaging means;
A temporary vertex position setting means for setting an arbitrary one position on the contour calculated by the contour calculation means as a temporary vertex position of the thread;
A plurality of pairs of positions on a pair of contour lines that are equidistant and separated on both sides in the width direction of the thread from the temporary vertex position on the contour line set by the provisional vertex position setting means are determined, and each pair of positions on the pair of contour lines A height difference calculating means for calculating a difference in height of the contour line in
Evaluation value calculation means for calculating an evaluation value related to the degree of symmetry of the cross-sectional shape of the screw thread based on the calculation result of the height difference calculation means;
By repeating the process by the temporary vertex position setting means, the height difference calculating means, and the evaluation value calculating means by sequentially changing the temporary vertex position set by the temporary vertex position setting means to a different position each time and sequentially repeating a plurality of times. Repetitive means for obtaining a plurality of evaluation values;
Evaluation value selection means for selecting the best evaluation value among a plurality of evaluation values obtained by the repetition means;
A thread shape inspection apparatus, comprising: determination means for determining the quality of the cross-sectional shape of the thread based on the best evaluation value selected by the evaluation value selection means. The imaging means is for imaging the contours of a plurality of screw threads,
Further, for each imaging data obtained by the imaging unit, the contour calculation unit, the provisional vertex position setting unit, the height difference calculation unit, the evaluation value calculation unit, the repetition unit, and the evaluation value selection unit By performing the processing, comprising an evaluation value acquisition means for acquiring the best evaluation value for each imaging data,
The thread shape according to claim 5, wherein the determination means determines whether or not the symmetry of the cross-sectional shape of the thread is good based on the best evaluation value acquired for each imaging data by the evaluation value acquisition means. Inspection device. The evaluation value calculation means calculates an evaluation value A by the following equation (1):
The thread shape inspection device according to claim 5 or 6, wherein the evaluation value selection means selects a minimum evaluation value as a best evaluation value among a plurality of evaluation values.
_{^{A = √ {Σ n i =}} 1 (ΔY i) 2} ... formula (1)
However,
n: number of sets ΔY _i : height difference of i-th set   The thread shape inspection device according to claim 5, wherein the thread is formed in a cap portion of a bottle can. In the manufacturing method of a bottle can that obtains a bottle can through a screw thread inspection process that inspects a screw thread formed on a base portion of the bottle can,
In the said thread inspection process, the symmetry degree of the cross-sectional shape of a thread is test | inspected as a thread inspection by the thread shape inspection method in any one of Claims 1-4. Method. In a bottle can manufacturing apparatus equipped with a screw thread inspection device for inspecting a screw thread formed on a base part of a bottle can,
An apparatus for manufacturing a bottle can comprising the thread shape inspection apparatus according to any one of claims 5 to 8 as the thread inspection apparatus.

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