WO2023166810A1 - Structure for opening curl part of bottle-type can - Google Patents

Abstract

Provided is a structure for an opening curl part of a bottle-type can with little loss of tamper-evidence due to excellent shape retention against loads from above.　A curl part 10 has an inner peripheral wall part 16, upper end rounded part 17, outer peripheral wall part 20, lower end rounded part 21, folding piece part 22, and tip edge part 23, is provided with an inclined wall part 15 that connects to a screw part downward from the inner peripheral wall part 16 and that has an outer diameter that gradually increases on the lower side, extends downward from a lowermost end portion 25 where the folding piece part 22 contacts a portion connecting the inner peripheral wall part 16 to the inclined wall part 15, and is provided with a retracting surface 24 that has a cross-sectional curvature radius R2 greater than the curvature radius R1 of the lower end rounded part 21 when cut by a plane that has a center of curvature P2 outside the mouth and neck part and that passes through the central axis line O of the mouth and neck part.

Description

Structure of opening curl of bottle-type can

The present invention relates to a metal bottle-type can that can be resealed with a cap, and particularly to the structure of the curled portion formed at the opening.

An example of this type of curled portion and its manufacturing method is described in Japanese Patent No. 4293349 or Japanese Patent Application Laid-Open No. 2019-177932. A metal bottle-type can has a curled portion because the opening closed by the cap may be put into the mouth and the contents may be directly drunk. That is, the curled portion is a portion in which the edge of the opening has a rounded shape, and the cut end of the metal plate, which is the material, is rolled inward and concealed, and is described in Japanese Patent No. 4293349 to Japanese Patent Application Laid-Open No. 2019-177932. The curled portion is a so-called seam-folded curled portion. The manufacturing method is as described in Japanese Patent No. 4293349, in which the tip of a cylindrical mouth and neck portion (mouth and neck portion) is bent outward and folded in two so as to form a double layer. Using the two-ply portion as the leading end, fold outward to form a three-ply ply. A triple seam-fold curled portion is formed by such two folds. The four-fold seam-folded curled portion is further folded in the same manner to form four layers.

As the name suggests, the seam-folded curled portion is not only simply folded, but also crushed in the plate thickness direction so that the overlapping folded pieces are in close contact with each other. Therefore, the upper end portion of the curled portion has a rounded shape due to the three or four curled portions. In addition, since the cut edge of the metal plate, which is the material, is caught inside the curled portion, in the case of a steel can, it is possible to prevent rust from progressing from the edge, and aluminum or its alloy is used as the material. In so-called aluminum cans, even if the resin coating the surface is peeled off at the cut ends, it can be concealed.

The curled part has the function of not only securing the so-called safety and preserving the appearance described above, but also maintaining sealing performance and tamper evidence (TE). A cap is placed on the mouth and neck portion where the curled portion is provided at the upper end to seal the opening. ) is elastically deformed and brought into close contact with the upper end of the curled portion, and as a result, the opening is sealed in a liquid-tight or air-tight state. Therefore, the accuracy of the curl may affect the tightness.

In addition, the TE property can be said to be the certainty of a change in form that indicates the fact of opening even once, and is shown in Japanese Patent No. 4293349 to Japanese Patent Application Laid-Open No. 2019-177932. In the structure, the TE property is affected by the mutual relationship between the bead portion (protruding portion) provided on the lower side of the screw portion and the curl portion. That is, the cap that covers the mouth and neck has a female thread that is screwed to the male thread of the mouth and neck by so-called roll-on capping, and at the same time, the band on the lower end that is separated by a slit (perforation) is , is shaped to wrap around and engage the bead from the outside. In this state, the cap is pushed up by the elastic force due to the elastic deformation of the sealing material (runner) described above. The cap is pushed up by an elastic force associated with elastic deformation acting between and. As a result, there is a preload between the bead and the band engaged therewith in the direction that the bead pulls down the band (cap) and conversely that the band (cap) pulls up the bead. ) will work. Therefore, if the curled portion is formed as desired, when the cap is slightly rotated in the opening direction, the cap is pushed up with respect to the mouth and neck portion. The fact that the slit (perforation) connecting to the bottle is broken, and the fact that the plug is opened will clearly remain as such a change in shape.

The seam-folded curled portion, which requires the above-mentioned functions, has a smaller diameter than the threaded portion. A slanted wall is formed, and a portion extending cylindrically upward from the slanted wall is folded outward as described above. In addition, since a load from above, that is, a capping pressure is applied to this curled portion during roll-on capping, conventionally, as described in Japanese Patent No. 4293349 or Japanese Patent Laid-Open No. 2019-177932, curling The lower bent portion (the downwardly convex bent portion) of the portion is brought into contact with the inclined wall whose outer diameter gradually increases toward the screw portion side. That is, the inclined wall serves as a so-called lower support for the curled portion.

Considering the structure of the conventional seam-folded curled portion described above, the so-called lower bent portion (hereinafter referred to as the lower end R portion) that is in contact with the inclined wall is a cross-sectional view when cut in the vertical direction. , it is a so-called free end. That is, the portion of the curled portion that is folded outwardly of the mouth/neck portion has a shape in which the lower end R portion is easily spread outward with the upper end portion connected to the mouth/neck portion serving as a fulcrum. On the other hand, the inclined wall with which the lower end R portion contacts or the inwardly curved surface portion connected from the inclined wall to the curled portion has a shape in which the outer diameter gradually increases on the lower side. Therefore, since the lower end R portion is in oblique contact with these slanted walls or curved surface portions, when the above-described plugging pressure or axial load due to collision acts on the curled portion, the lower end R portion exerts a component force that pushes it radially outward. That is, the curled portion of the conventional structure described above has a problem that the lower end R portion tends to spread outward due to the load acting in the axial direction, such as the plugging pressure. In addition, as a reaction force to the load that spreads the lower end R portion outward, a load that bends the innermost wall surface of the curled portion inward in the radial direction acts, and depending on the case, it is recessed. When such deformation occurs, the height of the curled portion or the position of its vertex is lowered in the direction away from the aforementioned runner.

If deformation such as an increase in the outer diameter at the lower end R portion occurs due to such an axial load such as plugging pressure, the TE properties described above may be impaired, and a quality problem may occur. . That is, the runner is pressed against the upper outer peripheral surface of the curled portion while the outer peripheral corner portion of the cap is squeezed during roll-on capping. Also, when the runner is compressed by the load from above, a portion of the runner is pushed outward in the radial direction and clings to the upper outer peripheral surface of the curled portion. On the other hand, when the lower end R portion of the curled portion is deformed to widen outward, the shape of the outer periphery of the curled portion itself becomes closer to a tapered shape with a smaller diameter on the upper side. That is, the outer circumference of the curled portion has a shape that pushes away the runner that is pressed or clinging to it. In addition, since the runner itself is also deformed into a shape with a large inner diameter on the lower side following the shape of the outer circumference of the curled portion, when the runner is slightly lifted together with the cap, the part with the large inner diameter is lifted toward the opening end. and the curled portion are easily released from each other. Therefore, when the cap is slightly turned in the opening direction, a gap is created between the curled portion and the runner without breaking at the perforations described above, allowing air to enter or the contents to leak out. there's a possibility that. That is, the tamper evidence function cannot be achieved.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a structure of an opening curl portion of a bottle-shaped can that is excellent in shape retention against a load from above and thus less likely to impair tamper evidence. It is intended for

In order to solve the above technical problems, the present invention has a cylindrical neck portion connected to the upper part of the can body via a shoulder portion whose diameter gradually decreases on the upper side, and the neck portion includes: A threaded portion for threading the cap, a protruding portion for engaging the tamper evidence band of the cap below the threaded portion, and a curled portion formed at the open end above the threaded portion. In the structure of the opening curled portion of the provided bottle-type can, the curled portion includes an inner peripheral wall portion connected upward from the threaded portion, and a radial direction from the upper end of the inner peripheral wall portion to the mouth and neck portion. an outwardly curved upper end R portion; an outer peripheral wall portion extending downward from the upper end R portion so as to be parallel to the inner peripheral wall portion; A lower end R portion curved inward in the radial direction, a folded piece portion extending upward from the lower end R portion in contact with the outer surface of the inner peripheral wall portion, and a portion on the tip side of the folded piece portion. an inclined wall confined between the inner peripheral wall portion and the outer peripheral wall portion, connected to the threaded portion downward from the inner peripheral wall portion, and having an outer diameter gradually increasing downwardly from the inner peripheral wall portion; is provided, extends downward from the lowermost end portion with which the folded piece contacts the portion connecting the inner peripheral wall portion to the inclined wall portion, and has a center of curvature on the outside of the mouth and neck portion and the It is characterized in that a retraction surface is provided which has a larger radius of curvature in a cross section taken along a plane passing through the central axis of the mouth and neck than the radius of curvature in the cross section of the lower end R portion.

In the present invention, in the vertical direction parallel to the central axis of the mouth and neck portion, the center of curvature of the retraction surface may be at the same height position or at a lower position than the center of curvature of the lower end R portion.

In the present invention, the upper end R portion has a curl top portion that is the most distal portion in the direction of the central axis of the mouth and neck portion, and the mouth and neck portion extends from the inner surface of the inner peripheral wall portion to the curl top portion. measured in the radial direction may be shorter than the length measured in the direction of the central axis of the mouth/neck portion from the start portion of the upper end R portion on the inner peripheral wall portion side to the curl top portion.

In the present invention, of the inclined wall portion between the inner peripheral wall portion of the curled portion and the screw portion, the retraction surface is formed in the portion immediately below the curled portion. This retraction surface is a portion extending downward from the lowest portion of the portion where the folding piece portion overlapping the outer surface of the inner peripheral wall surface is in contact with the outer surface of the inner peripheral wall surface, and its shape is as follows. It is a surface (including a straight surface with an infinite curvature radius) having a radius of curvature larger than the radius of curvature of the lower R portion of the curled portion that is connected to the lower side of the folded piece. Therefore, even if a load is applied to the curled portion from the upper side and the curled portion is deformed downward, there is no portion to which the so-called lower end R portion abuts. does not work. That is, since the outer peripheral surface of the curled portion does not deform into a tapered shape with a smaller diameter on the upper side, the sealing material provided on the inner surface of the cap and clinging to the outer peripheral surface of the upper end of the curled portion is pushed upward. As a result, it is possible to avoid or suppress the deterioration of the TE property by improving the sealing property.

Further, when a load is applied to the curled portion from above, interference between the lower end R portion and the inner peripheral wall portion or the inclined wall portion is avoided or suppressed, so that the inner peripheral wall portion or the inclined wall portion does not deform. , can improve the buckling strength.

Furthermore, in the present invention, the shape of the upper end R portion of the curled portion is made into a shape that is not conventional, and the length measured in the radial direction of the mouth and neck portion from the inner surface of the inner peripheral wall portion to the curl top portion is the upper end R portion. Since the length measured in the direction of the central axis of the mouth and neck portion from the start of the inner peripheral wall side of the curl to the curl top is shorter than the length, most of the load applied from the upper side of the curl is received by the inner peripheral wall, and the curl It is possible to avoid or suppress the moment that causes the portion to bend outward and the deformation that accompanies it. That is, the plastic deformation and the amount of plastic deformation of the curled portion are reduced to maintain the elasticity of the curled portion in the vertical direction, thereby maintaining the close contact state of the curled portion with the sealing material provided on the inner surface of the cap, and the bottle-shaped can. It is possible to improve the sealing property and TE property of the.

1 is a front view showing an example of a bottle-shaped can targeted by the present invention; FIG. Fig. 2 is a partially cross-sectional front view showing a can body without a bottom lid and a cap rough-formed member that is attached to the mouth and neck of the can body by roll-on capping to form a cap. It is sectional drawing which expands and shows a curl part. 1 is a table summarizing the results of Examples 1 and 2 and Comparative Examples. 2 is a table summarizing the results of Examples 3 to 5. FIG.

An example of implementing the present invention will be described below with reference to the drawings. The example described below is merely an example of the present invention, and does not limit the present invention.

First, a bottle-type can having a curled portion according to the present invention will be described. The bottle-type can in the present invention is made of metal such as steel can or aluminum can, and is a so-called two-piece can in which the can body and the bottom are integrally molded, or a so-called three-piece can in which the bottom lid is attached to the bottom of the can body by winding it. It can be a can. In any can, a cylindrical neck is formed on the upper part of the can body through a shoulder, the upper end of the neck is open, and the entire circumference of the opening is a curled part. , and a metal can having a cap screw-fitted to the mouth and neck of the can.

FIG. 1 shows an example of a wide-mouthed steel can 1. The neck is formed on the upper side of a cylindrical can body 2 through a shoulder 3 whose diameter gradually decreases on the upper side. A cap 4 is screw-fitted to the mouth-and-neck portion to seal the upper end opening of the mouth-and-neck portion. A bottom lid 5 is attached to the bottom of the can body 2 by winding it.

FIG. 2 shows a can body 2 without a bottom lid 5 attached, and a cap blank 7 attached to the neck portion 6 of the can by roll-on capping to form the cap 4 . A mouth-and-neck portion 6 extending upward from the shoulder portion 3 is formed with a protruding portion 8 and a threaded portion 9 in order from the bottom, and a curled portion 10 is formed at the opening at the upper end. The protruding portion 8 is a portion for the function of tamper evidence, and is formed on the upper end portion of the shoulder portion 3 over the entire circumference so as to protrude outward in the radial direction. Therefore, the portion between the protruding line portion 8 and the shoulder portion 3, that is, the portion below the protruding line portion 8 has a constricted shape. The threaded portion 9 is a portion made up of a helical convex portion, and is a male threaded portion with one or two threads. The threaded portion 9 and the ridge portion 8 are processed by roll-forming the cylindrical neck portion 6 from the inner and outer peripheral sides. The curled portion 10 is a portion for smoothing the opening end that serves as a spout or a drinking spout and concealing the sharp cut end of the metal material, and is formed by bending and winding the cut end outward. It is Its detailed structure will be described later.

On the other hand, the cap rough shape member 7 is made of an aluminum alloy and has a cylindrical shape having a top plate portion 11, and an intermediate portion in the axial direction (vertical direction) is a straight cylindrical shape. Form a thread. In addition, a band portion (tamper evidence band) 13 partitioned by intermittent slits (perforations) 12 along the circumferential direction is provided at the lower end portion. This band portion 13 is a portion that fulfills a tamper evidence function together with the above-described ridge portion 8. With the cap rough shape member 7 covering the mouth and neck portion 6, the band portion 13 is wrapped around the ridge portion 8 from below. By deforming the portion 13, the band portion 13 is engaged with the protruding portion 8 and integrated. Further, a sealing material (runner) 14 made of mold resin is adhered to the outer peripheral portion of the inner surface of the top plate portion 11 . By pressing the upper end of the curled portion 10 against the runner 14 and elastically deforming the runner 14, the two are in close contact with each other to seal the open end of the mouth/neck portion 6 in a liquid-tight or air-tight state. The pressing of the runner 14 against the curled portion 10, the forming of the female screw portion, and the engagement of the band portion 13 with the ridge portion 8 are carried out by placing the cap rough shape member 7 over the neck portion 6 and plugging it from above. A known roll-on capping method can be used in which pressure is applied and a forming load is applied from the outer peripheral side of the cap rough-shaped member 7 by appropriate forming rolls.

FIG. 3 shows an enlarged cross-sectional view of the curl portion 10 according to the embodiment of the present invention. The example shown here is an example of a quadruple-folded seam-folded curled portion, which extends upward from the threaded portion 9 described above and is formed by being connected to an inclined wall portion 15 that is constricted so as to have a smaller diameter at the upper side. there is The inclined wall portion 15 rises on its upper side so as to be parallel to the central axis O of the mouth and neck portion 6, and the cylindrical portion substantially parallel to the central axis O of the mouth and neck portion 6 is the inner peripheral wall portion 16. ing. The upper end portion of the inner peripheral wall portion 16 is bent outward in the radial direction of the mouth/neck portion 6 to form an upper end R portion 17 that smoothly protrudes upward. The boundary portion between the inner peripheral wall portion 16 shown by a straight line in FIG. The portion (i.e., the upper end on the bottle-type can 1) is the curled top 19. As shown in FIG.

Note that the radius of curvature of the upper end R portion 17 is not uniform. The radius R4 at is larger. Therefore, the length L1 measured in the radial direction of the mouth/neck portion 6 from the inner surface of the inner peripheral wall portion 16 to the curl top portion 19 is equal to the height of the curl top portion 19 from the start portion 18 (the central axis O of the mouth/neck portion 6). is smaller than L2 (L2>L1).

The portion extending downward from the outer peripheral side of the curled portion 10 to the upper end R portion 17 is the outer peripheral wall portion 20. Since the curled portion 10 has a so-called seam fold structure, the outer peripheral wall portion 20 is the inner peripheral wall portion. 16 are almost parallel. A portion on the lower end side of the outer peripheral wall portion 20 is bent inward in the radial direction of the mouth/neck portion 6 to form a lower end R portion 21 . This lower end R portion 21 is a portion that is curved by approximately 180°, and the curvature radius R1 may be constant, or may is the average radius to the part of The center of curvature is indicated by the symbol "P1" in FIG.

A portion that is connected to the lower end R portion 21 and rises upward in FIG. is in contact with or in close contact with The upper end portion of the folded piece portion 22 is further bent outward, and the leading edge portion (cut end) 23 of the metal material constituting the bottle-shaped can 1 is folded into the outer peripheral wall portion 20. It is confined between the pieces 22 . The so-called seam folding of the curled portion 10 can be performed by the method and procedure described in the above-mentioned Japanese Patent No. 4293349 and Japanese Patent No. 4375706. Therefore, the order of folding is the same as described above. 2, bending of the tip edge portion 23 with respect to the folding piece portion 22, bending of the lower end R portion 21, and bending of the upper end R portion 17 are performed in this order.

Unlike the conventional structure, the curl portion 10 configured as described above is separated from the inclined wall portion 15 without being supported by the inclined wall portion 15, and the curl portion 10 and the inclined wall portion 15 are separated from each other. A retraction surface 24 is provided therebetween. In the embodiment of the present invention, the retraction surface 24 is the lower side or inclined surface of the inner peripheral wall portion 16 so as not to interfere with the lower end side portion, particularly the lower end R portion 21, when the curl portion 10 is loaded from above. This is a surface (portion) provided on the upper portion of the wall portion 15 .

Specifically, the folded piece portion 22 extends downward from the lowermost end portion (or a portion corresponding to the boundary between the lower end R portion 21 and the folded piece portion 22) 25 of the portion where the folded piece portion 22 contacts the inner peripheral wall portion 16. When viewed in the cross-sectional view shown in FIG. 3, it is a flat surface that is straight in the vertical direction or a curved surface that is convex toward the inside of the mouth/neck portion 6 . In other words, the retreat surface 24 has a center of curvature P2 outside the mouth/neck portion 6 when viewed in the cross-sectional view shown in FIG. It is a surface of radius R2.

The center of curvature P2 is located at a height below the center of curvature P1 of the lower end R portion 21 in the vertical direction along the central axis O of the mouth/neck portion 6. In the example shown in FIG. 3, the center of curvature P2 of the retraction surface 24 is positioned below the center of curvature P1 of the lower end R portion 21. In the example shown in FIG. Therefore, the retraction surface 24 is a cylindrical surface (flat surface in the cross-sectional view of FIG. 3) 24a linearly lowered from the lowermost end portion 25 of the outer peripheral surface of the inner peripheral wall portion 16 to the height position of the center of curvature P2 of the retraction surface 24. and a curved surface 24b that smoothly connects from the cylindrical surface 24a to the inclined wall portion 15. As shown in FIG. When the center of curvature P1 of the lower end R portion 21 and the center of curvature P2 of the retracting surface 24 are at the same height position, the cylindrical surface (flat surface in the sectional view of FIG. 3) 24a does not exist, and only the curved surface 24b is formed. The retraction surface 24 is configured by .

When the cap 4 is attached by roll-on capping, when the bottle-type can 1 is dropped upside down, or when some kind of falling object hits the curled portion 10, which is the embodiment of the present invention, the curl portion shown in FIG. A load is applied from the upper side of the When such a load is applied, elastic deformation occurs in the inner peripheral wall portion 16, the inclined wall portion 15, or portions therebetween, and the curled portion 10 may move downward in FIG.

In that case, in the structure of the curled portion 10 according to the present invention described above, the inclined wall portion 15 is not in contact with the lower side of the curled portion 10 (lower end R portion 21), and the retreat surface 24 is provided. Since the lower end R portion 21 and the inclined wall portion 15 are separated in the vertical direction, the curled portion 10 descends substantially straight. That is, even if the inclined wall portion 15 has a shape in which the outer diameter gradually increases on the lower side, the curl portion 10 is not pressed against the inclined wall portion 15. A load that pushes it outward does not act.

Thus, in the structure of the curled portion 10 according to the present invention, when a load is applied from above, the outer peripheral surface of the curled portion 10 is maintained in a substantially straight cylindrical shape, and the curled portion 10 is formed by roll-on capping. It is possible to maintain good adhesion of the runner 14 clinging to the upper peripheral surface. This is the same when the cap 4 attached to the mouth/neck portion 6 is turned in the opening direction. That is, when the cap 4 is slightly moved upward from the mouth/neck portion 6 by rotating it in the opening direction, the runner 14 clinging to the upper end outer peripheral surface of the curl portion 10 moves upward while clinging to the outer peripheral surface. Since it moves, the sealed state of the bottle-type can 1 is maintained. When the cap 4 has moved upward enough to create a gap between the runner 14 and the upper end surface of the curled portion 10, the slit (perforation) 12 that defines the band portion 13 provided in the cap 4 is formed. rupture occurs. That is, when the bottle-shaped can 1 is opened, the band portion 13 is always torn off, so that the bottle-shaped can 1 having good TE properties can be obtained.

On the other hand, the load applied to the curled portion 10 from above acts on the upper end portion of the curled portion 10 as a moment with the start portion 18 of the upper end R portion 17 as a fulcrum and the curl top portion 19 as a point of action. Since the length of the so-called "arm" of the moment is "L1", which is less than the length L2 from the start 18 to the top of the curl 19, the moment is small. In addition, the portion on the outer peripheral side (tip side) of the curl top portion 19 is supported by the portion from the start portion 18 to the curl top portion 19. Since the length L2 of that portion is increased as described above, It is possible to suppress deformation in which the portion on the tip side from the curled top portion 19 is sagging downward and deformation of the curled top portion 19 itself. As a result, the curled portion 10 and the runner 14 can be kept in close contact with each other, resulting in good sealing performance and TE performance.

Examples and comparative examples conducted to confirm the effects of the present invention are shown here. First, the bottle-shaped cans used in the examples and comparative examples will be described. was rolled to weld the edges, and then expanded to create a three-piece welded can body with a can body diameter of φ53 (53 mm). One open end of the can body was necked, a shoulder portion and a bead portion were formed, and the mouth cylinder was drawn to form a mouth and neck portion, where a screw portion and a curl portion were formed. In addition, after performing necking processing on the opening on the opposite side, flanging processing was performed on the tip edge so that the bottom cover could be attached. Its shape is shown in FIG. The curled portion was formed by the method described in the aforementioned Japanese Patent No. 4293349 to form a so-called quadruple seam-folded curled portion. By forming such a curled portion, rusting of the cut edge of steel, which is the material, is prevented, and an opening of the bottle-shaped can that is pleasant to the palate is created.

By using the bottle-shaped can configured in this way, the function and effect of providing the retraction surface 24 described above were confirmed.

[Example 1]
The curled portion 10 is formed such that the center of curvature P1 of the lower end R portion 21 and the center of curvature P2 of the retracting surface 24 are at the same height. A capping pressure was applied to this by roll-on capping, and the deformation state of the curled portion 10 was evaluated.

[Example 2]
The center of curvature P2 of the retracting surface 24 is set at a position lower than the center of curvature P1 of the lower end R portion 21, so that a so-called cylindrical surface (flat surface) 24a corresponding to the difference in height position is formed on the lower side of the inner peripheral wall portion 16. It was molded continuously, and then the curved surface 24b with a predetermined radius of curvature was formed. A capping pressure was applied to the curled portion 10 by roll-on capping, and the deformation state of the curled portion 10 was evaluated.

[Comparative example]
Of the portion where the folded piece 22 contacts the inner peripheral wall portion 16, the portion extending downward from the lowermost end (or the portion corresponding to the boundary between the lower end R portion 21 and the folded piece 22) 25 is The cross-sectional arc surface is formed around the center of curvature P20, which is higher than the center of curvature P1 of the lower end R portion 21. As shown in FIG. A capping pressure was applied to the curled portion 10 by roll-on capping, and the deformation state of the curled portion 10 was evaluated.

(Evaluation results)
Fig. 4 shows the relationship between the height positions (vertical positions) P1y, P2y, and P20y of the centers of curvature in Example 1, Example 2, and Comparative Example, curl shape before plugging pressure, and curl posture after plugging pressure. and evaluation are shown. In addition, in FIG. 4, the code|symbol "14" shows a runner. In Example 1, there was no particular change in the curling posture after the capping pressure was applied, and therefore the evaluation was "Good" as there was no particular problem as a product. In addition, in Example 2, the inner peripheral wall portion 16 was slightly bent, and the position of the curled portion 10 was shifted accordingly. Considering that it is possible to form a recess into which a part of the runner 14 is inserted, such a positional deviation of the curled portion 10 does not particularly affect the adhesion of the runner 14. The evaluation was made as "○", which indicates that there is no particular problem as a product. On the other hand, in the comparative example, as the curled portion 10 was pushed down, it slipped on the inclined wall portion 15 and deformed so that the outer diameter expanded on the lower end R portion 21 side. This is a modification that is the subject of the present invention, and therefore the evaluation was "X", which cannot be regarded as a product.

Next, the length L1 measured in the radial direction of the mouth/neck portion 6 from the inner surface of the inner peripheral wall portion 16 to the curl top portion 19, and the height of the curl top portion 19 from the start portion 18 (the central axis of the mouth/neck portion 6 The relationship with the length measured in the direction of O) L2 was evaluated.

[Example 3]
In the bottle-shaped can described above, the center of curvature P2 of the retracting surface 24 is set lower than the center of curvature P1 of the lower end R portion 21, and the lengths L1 and L2 are set to "L1>L2". That is, the position of the curled top portion 19 is made far from the inner peripheral wall portion 16 . A capping pressure was applied to the curled portion 10 by roll-on capping, and the deformation state of the curled portion 10 was evaluated.

[Example 4]
In the bottle-type can described above, the center of curvature P2 of the retracting surface 24 is set lower than the center of curvature P1 of the lower end R portion 21, and the lengths L1 and L2 are set to "L1=L2". That is, the length between the position of the curl top portion 19 and the inner peripheral wall portion 16 is set to be medium. A capping pressure was applied to the curled portion 10 by roll-on capping, and the deformation state of the curled portion 10 was evaluated.

[Example 5]
In the bottle-shaped can described above, the center of curvature P2 of the retracting surface 24 is set lower than the center of curvature P1 of the lower end R portion 21, and the lengths L1 and L2 are set to "L1 <L2". That is, the length between the position of the curl top portion 19 and the inner peripheral wall portion 16 is shortened. A capping pressure was applied to the curled portion 10 by roll-on capping, and the deformation state of the curled portion 10 was evaluated.

(Evaluation results)
FIG. 5 shows the relationship between the lengths L1 and L2, the curled shape before the capping pressure, the curled posture after the capping pressure, and the position of the curled portion in Examples 3-5. Incidentally, in FIG. 5, reference numeral "14" indicates a runner.

In Example 3, a portion of the upper end R portion 17 on the inner peripheral wall portion 16 side bent downward, so-called a waist bend, and the lower end R portion 21 was lowered accordingly. Therefore, it was recognized that it is necessary to secure the dimension in the height direction (the direction of the central axis O of the mouth/neck portion 6) of the retraction surface 24 in the present invention to some extent. In that sense, the evaluation was set to "OK".

In the fourth embodiment, the plugging pressure is mainly received by the portion of the inner peripheral wall portion 16 and the upper end R portion 17 on the inner peripheral wall portion 16 side. 21 dropped. Therefore, it was recognized that it is necessary to secure the dimension in the height direction (the direction of the central axis O of the mouth/neck portion 6) of the retraction surface 24 in the present invention to some extent. In that sense, the evaluation was set to "OK".

In Example 5, since most of the plugging pressure is received by the inner peripheral wall portion 16, the inner peripheral wall portion 16 was pressed vertically and flexed. The R portion 21) did not drop significantly. Therefore, evaluation was made into "good."

As shown by the evaluation results of Examples 1 to 5 and the comparative example described above, in the embodiment of the present invention, the radius of curvature of the retreat surface 24 is larger than the radius of curvature of the lower end R portion 21, and the center of the mouth/neck portion 6 It is preferable to set the center of curvature P2 of the retraction surface 24 below the position of the center of curvature P1 of the lower end R portion 21 in the vertical direction along the axis O. Also, the length L1 measured in the radial direction of the mouth/neck portion 6 from the inner surface of the inner peripheral wall portion 16 to the curl top portion 19, and the height of the curl top portion 19 from the start portion 18 described above (the central axis O of the mouth/neck portion 6 It is preferable that the relationship between the length measured in the direction of ) and L2 be "L1<L2".

1 bottle-shaped can 2 can body 3 shoulder 4 cap 5 bottom lid 6 mouth/neck 7 cap rough shape member 8 ridge 9 screw 10 curl 11 top plate 12 slit (perforation)
13 band portion 14 runner 15 inclined wall portion 16 inner peripheral wall portion 17 upper end R portion 18 start portion 19 curl top portion 20 outer peripheral wall portion 21 lower end R portion 22 folding piece portion 23 tip edge portion 24 retraction surface 24a cylindrical surface 24b curved surface 25 lowest end Part O Center axis P1, P2, P20 Curvature center R1, R2, R3, R4 Curvature radius

Claims (3)

A cylindrical neck portion is formed on the upper part of the can body by being connected to the can body through a shoulder portion whose diameter gradually decreases on the upper side. In the structure of the opening curl portion of a bottle-type can, wherein a protruding portion for engaging the tamper evidence band of the cap below and a curl portion formed at the opening end above the screw portion are provided,
The curl portion is
an inner peripheral wall portion that extends upward from the threaded portion; an upper end R portion that curves outward in the radial direction of the mouth and neck portion from an upper end portion of the inner peripheral wall portion; a lower end R portion that curves inward in the radial direction of the mouth and neck portion from the lower end portion of the outer peripheral wall portion, and an upper end from the lower end R portion and a tip edge part confined between the inner peripheral wall part and the outer peripheral wall part on the leading end side of the folded strip part. and
An inclined wall portion is provided downwardly from the inner peripheral wall portion to connect to the threaded portion and whose outer diameter gradually increases on the lower side,
A portion connecting the inner peripheral wall portion to the inclined wall portion extends downward from a lowermost portion with which the folded piece portion contacts, and has a center of curvature on the outside of the mouth and neck portion and a center of the mouth and neck portion. A structure of an opening curl portion of a bottle-type can, characterized in that a retraction surface is provided which has a radius of curvature larger than that of the lower end R portion in the cross section when cut along a plane passing through the axis. In the structure of the opening curl portion of the bottle-type can according to claim 1,
A bottle-shaped can characterized in that, in the vertical direction parallel to the central axis of the mouth/neck portion, the center of curvature of the retracting surface is at the same height position or at a position lower than the center of curvature of the lower end R portion. The structure of the opening curl part. In the structure of the opening curl portion of the bottle-type can according to claim 1 or 2,
The upper end R portion has a curl top portion that is the most distal portion in the direction of the central axis of the mouth and neck portion,
The length measured in the radial direction of the mouth and neck portion from the inner surface of the inner peripheral wall portion to the curl top portion is the length of the mouth and neck portion from the start of the upper end R portion on the inner peripheral wall side to the curl top portion. A structure of an opening curl portion of a bottle-type can characterized by being shorter than the length measured in the direction of the central axis.