KR20240159915A - Structure of the opening of a bottle-shaped can - Google Patents

Abstract

Provides a structure for the opening curl of a bottle-shaped can that is less likely to damage tamper evidence properties by maintaining its shape well against a load from above.
The curled portion (10) has an inner wall portion (16), an upper R portion (17), an outer wall portion (20), a lower R portion (21), a folded portion (22), and a leading edge portion (23), and an inclined wall portion (15) is formed that is connected downwardly from the inner wall portion (16) to a screw portion and whose outer diameter gradually increases downwardly, and in a portion connected from the inner wall portion (16) to the inclined wall portion (15), a folded portion (22) extends downwardly from the lowest portion (25) where it comes into contact, and a center of curvature (P2) is formed on the outer side of the bore portion, and a radius of curvature (R2) in the cross section when cut along a plane passing through the central axis (O) of the bore portion is larger than the radius of curvature (R1) of the lower R portion (21).

Description

Structure of the opening of a bottle-shaped can

The present invention relates to a metal bottle-type can capable of being resealed by a cap, and more particularly to the structure of a curled portion formed at an opening thereof.

An example of this type of curl or its manufacturing method is described in Japanese Patent No. 4293349 or Japanese Patent Application Laid-Open No. 2019-177932. Since a metal bottle-shaped can has a spout attached to an opening that is closed by a cap and the contents are sometimes drunk directly, a curl is formed at the opening. That is, the curl is a part in which the edge of the opening is rounded and the cut surface of the metal plate as the material is rolled inward to conceal it. The curl described in Japanese Patent No. 4293349 or Japanese Patent Application Laid-Open No. 2019-177932 is a so-called folded curl. The manufacturing method is as described in Japanese Patent No. 4293349, and the tip of the cylindrical neck portion is bent outward and folded in two so as to form a two-sheet cover. With the two-sheet folding part as the tip, fold it in two to make a three-sheet folding part by bending it outward. The three-layer folding curl part is formed by these two bends. The four-layer folding curl part is formed by performing the same bending again to make a four-sheet folding part.

The folding curl portion, as its name indicates, is not simply bent, but is pressed and crushed in the direction of the plate thickness so that the folded pieces that are overlapped each other come into close contact. Therefore, the upper part of the curl portion becomes round because the curl portion is made of three or four folds. In addition, since the cut edge of the material, the metal plate, is rolled into the inside of the curl portion, in the case of a steel can, it is possible to prevent rust from progressing from the edge, and in the case of a so-called aluminum can made of aluminum or an alloy thereof, even if the resin covering the surface peels off at the cut end, this can be concealed.

The curl portion has the function of maintaining sealing properties and tamper-evidence function (TE properties) in addition to ensuring the so-called safety and preserving the appearance as mentioned above. A cap is placed on the bore portion where the curl portion is formed at the upper end to seal the opening. In this case, a sealing material (liner), which is a molding resin installed on the inner surface of the top plate portion of the cap, elastically deforms and adheres to the upper end of the curl portion, and as a result, the opening is sealed in a liquid-tight or air-tight state. Therefore, there are cases where the precision of the curl portion affects the sealing properties.

In addition, TE property can be said to be the certainty of the change in shape indicating the fact of opening the stopper even once, and in the structure disclosed in Japanese Patent No. 4293349 or Japanese Patent Application Laid-Open No. 2019-177932, the TE property is determined by the relationship between the bead portion (convex portion) formed on the lower side of the screw portion and the curl portion. That is, the cap covered on the bore portion is formed by a female screw portion that screws into the bolt portion of the bore portion by so-called roll-on capping, and at the same time, the band portion on the lower side separated by the slit portion (cut line) is formed so as to fit while wrapping the bead portion from the outside. In this state, the cap is pushed up by the elastic force due to the elastic deformation of the above-mentioned sealing material (liner), and the cap is pushed up by the elastic force accompanying the elastic deformation acting between the bore portion and the cap in the screw portion or the inclined wall portion between the screw portion and the curl portion. As a result, a preload is applied between the bead portion and the band portion fitted thereto in the direction in which the bead portion pulls down the band portion (cap) and conversely, the band portion (cap) pulls up the bead portion. Accordingly, if the curl portion is formed as desired, when the cap is slightly rotated in the direction of opening the cap, the cap is pushed up against the bore portion, so that the band portion fitted to the bead portion is broken at the slit portion (cut line) connected to the cap, and the fact that the cap has been opened is clearly recorded as a change in this form.

The folding curl portion requiring the above function has a smaller diameter than the screw portion, and as described, for example, in Japanese Patent No. 4293349 or Japanese Patent No. 4375706, a portion extending upwardly from the screw portion is tightened to a small diameter to form an inclined wall, and a portion extending upwardly in a cylindrical shape from the inclined wall is folded outward as described above to form the curl portion. Then, since a load from above, that is, a capping pressure, is applied to the curl portion during roll-on and capping, conventionally, as described in Japanese Patent No. 4293349 or Japanese Patent Application Laid-Open No. 2019-177932, the lower bent portion of the curl portion (the bent portion that is convex downward) is brought into contact with the inclined wall whose outer diameter gradually increases toward the screw portion. That is, the inclined wall serves as the so-called support of the curl portion.

When examining the structure of the above-mentioned conventional folded curl portion, the so-called lower bent portion (hereinafter, referred to as the lower R portion) in contact with the above-mentioned inclined wall is cut in the cross-section in the vertical direction, and is thus the so-called free end. That is, the portion of the curl portion that is folded outward from the bore portion is formed in a shape in which the lower R portion is easily expanded outward, with the upper portion connected to the bore portion as a support point. In contrast, the inclined wall that the lower R portion is in contact with or the curved portion inwardly connected from the inclined wall to the curl portion is formed in a shape in which the outer diameter gradually increases from the lower side. Accordingly, since the lower R portion is in oblique contact with these inclined walls or curved portions, when the curl portion is subjected to the aforementioned capping pressure or an axial load due to a collision, a force that pushes it outward in the radial direction is applied to the lower R portion. That is, the curl portion of the above-mentioned conventional structure has a problem in which the lower R portion is easily expanded outward due to an axial load such as the capping pressure. In addition, as a reaction force of the load that expands the lower R portion outward, a load is applied that bends the innermost wall surface of the curl portion inward in the radial direction, and in some cases, causes it to sink. When such deformation occurs, the height of the curl portion or the position of its peak goes down in the direction away from the aforementioned liner.

If deformation occurs, such as an increase in the outer diameter at the lower R portion due to an axial load such as the capping pressure, the TE property described above may be damaged, which may result in quality problems. That is, the liner is pressed against the upper outer surface of the curl portion by tightening the outer peripheral corner of the cap during roll-on and capping. In addition, since the liner is compressed by a load from above, a part of it is pushed outward in the radial direction and adheres to the upper outer surface of the curl portion. In contrast, if deformation occurs such that the lower R portion of the curl portion expands outward, the outer peripheral shape of the curl portion itself approaches a tapered shape with a smaller diameter at the top. In other words, the outer peripheral shape of the curl portion becomes a shape that pushes the liner that is being pushed in or adhered to upward. In addition, since the liner itself is also deformed to a shape with a larger inner diameter at the bottom along the outer peripheral shape of the curl portion, if the liner is lifted up slightly together with the cap, the part with a larger inner diameter occurs at the opening end, so the close contact between the liner and the curl portion is easily relieved. Therefore, if the cap is slightly turned in the direction of opening, a gap may be created between the curl and the liner without causing a break at the aforementioned cutting line, allowing air to enter or the contents to leak out. In other words, the tamper evidence function cannot be achieved.

The present invention has been made in consideration of the above circumstances, and has as its object the provision of a structure for an opening curl portion of a bottle-shaped can that is excellent in maintaining its shape against a load from above, thereby reducing damage to tamper evidence properties.

The present invention, in order to solve the above technical problem, provides a structure of an opening curl portion of a bottle-shaped can, in which a cylindrical bore portion is formed by connecting the upper portion of a can body to a shoulder portion whose diameter gradually decreases from the upper side, and the bore portion comprises a screw portion for screwing a cap into place, a steel portion for engaging a tamper evidence band of the cap from below the screw portion, and a curl portion formed at an opening end above the screw portion, wherein the curl portion comprises an inner wall portion extending upward from the screw portion, an upper R portion curved outward in a radial direction of the bore portion from an upper portion of the inner wall portion, an outer wall portion extending downward from the upper R portion to be parallel to the inner wall portion, a lower R portion curved inward in a radial direction of the bore portion from a lower portion of the outer wall portion, a folding portion extending upward in contact with an outer surface of the inner wall portion from the lower R portion, and a portion on the leading side of the folding portion, wherein It is characterized in that it has a leading edge portion trapped between an inner wall portion and the outer wall portion, an inclined wall portion that is connected downwardly from the inner wall portion to the screw portion and further has an outer diameter that gradually increases downwardly is formed, and in a portion connected from the inner wall portion to the inclined wall portion, a retreat surface is formed that extends downwardly from the lowest portion where the folding piece comes into contact, and has a center of curvature outside the neck portion, and further has a radius of curvature larger than the radius of curvature in the cross section when cut along a plane passing through the center axis of the neck portion in the cross section of the lower R portion.

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

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

In the present invention, among the inclined wall portions between the inner wall portion and the screw portion of the curl portion, a retreat surface is formed in a portion immediately below the curl portion. This retreat surface is a portion extending downward from the lowest portion of the location where the fold-in section overlapping the outer surface of the inner wall portion contacts the outer surface of the inner wall portion, and its shape is a surface having a radius of curvature larger than the radius of curvature of the lower R section that continues downward of the fold-in section of the curl portion (including a straight surface having an infinite radius of curvature). Accordingly, even if a load is applied from above to the curl portion to deform downward, since there is no portion that contacts the so-called lower R section, a load that pushes and expands the curl portion outward in the radial direction of the lower side does not act on the curl portion. That is, since the outer surface of the curl portion is not deformed into a tapered shape with a smaller diameter at the top, the sealing material formed on the inner surface of the cap and attached to the upper outer surface of the curl portion does not have an upward pushing effect, and as a result, the sealing property is improved, and the deterioration of the TE property can be avoided or suppressed.

In addition, when a load is applied from above to the curled portion, interference between the lower R portion and the inner wall portion or the inclined wall portion is avoided or suppressed, so that deformation of the inner wall portion or the inclined wall portion does not occur, thereby improving the buckling strength.

In addition, in the present invention, the shape of the upper R portion of the curl portion is made into an unprecedented shape, and the length measured in the radial direction of the bore portion from the inner surface of the inner wall portion to the curl top portion is made shorter than the length measured in the direction of the central axis of the bore portion from the start portion of the inner wall portion side of the upper R portion to the curl top portion, so that most of the load applied from the upper side of the curl portion is received by the inner wall portion, and a moment that bends the curl portion outward or deformation resulting therefrom can be avoided or suppressed. That is, by reducing the plastic deformation or the amount of plastic deformation of the curl portion, the elasticity of the curl portion in the vertical direction is maintained, and accordingly, a state of close contact with a sealing material installed on the inner surface of the cap of the curl portion is maintained, so that the sealing performance and TE performance of the bottle-shaped can can be improved.

Figure 1 is a front view showing an example of a bottle-shaped can targeted in the present invention.
Figure 2 is a partial cross-sectional front view showing a can body without a bottom cover attached and a cap forming material attached to the bore portion thereof by roll-on capping to form a cap.
Figure 3 is a cross-sectional view showing an enlarged view of the curl section.
Figure 4 is a diagram summarizing the results of Examples 1 and 2 and Comparative Examples.
Figure 5 is a diagram summarizing the results of Examples 3 to 5.

(Form for carrying out the invention)

Hereinafter, an example of implementing the present invention will be described with reference to the drawings. In addition, the example described below is only an example of the present invention and does not limit the present invention.

First, a bottle-shaped can having a curled portion according to the present invention will be described. The bottle-shaped can in the present invention is made of metal, such as a steel can or an aluminum can, and may be a so-called two-piece can in which the can body and the bottom portion are formed integrally, or a so-called three-piece can in which a bottom cover is seamed and attached to the bottom portion of the can body. In either case, the metal can has a structure in which a barrel-shaped neck portion is formed through a shoulder portion on the upper portion of the can body, the upper end of the neck portion is opened, and further, the entire circumference of the opening portion forms a curled portion, and further, a cap is screw-connected to the neck portion.

Fig. 1 illustrates an example of a wide-mouth bottle-shaped can (1) made of steel, wherein a neck portion is formed through a shoulder portion (3) extending upwardly from a cylindrical can body (2) and gradually becoming smaller in diameter from the upper side, and a cap (4) is screw-connected to the neck portion, so that the upper opening of the neck portion is sealed. In addition, a bottom cover (5) is seamed and attached to the bottom of the can body (2).

Fig. 2 illustrates a can body (2) without a bottom cover (5) attached, and a cap shaping member (7) attached to the neck portion (6) by roll-on capping to form a cap (4). In the neck portion (6) extending upward from the shoulder portion (3), a barbed wire portion (8) and a screw portion (9) are formed in order from the bottom, and a curled portion (10) is formed in the opening at the top. The barbed wire portion (8) is a portion for the function of tamper evidence, and is formed over the entire circumference so as to protrude outwardly in the radial direction at the upper portion of the shoulder portion (3). Therefore, the portion between the barbed wire portion (8) and the shoulder portion (3), i.e., the lower portion of the barbed wire portion (8), has a concave shape. The screw portion (9) is a portion formed by a spiral convex portion, and is formed by one or two rows of male screw portions. These screw parts (9) and wire parts (8) are processed by performing roll forming from the inner and outer sides of the cylindrical bore part (6). The curl part (10) is a part for making the opening end, which is the outlet or drinking port, smooth and concealing the sharp cutting end of the metal material, and is formed by bending and wrapping the cutting end outward. The detailed structure thereof will be described later.

On the other hand, the cap molding material (7) is made of aluminum alloy and has a cylindrical shape having a top plate (11), and the middle part in the axial direction (up-down direction) is in a straight cylindrical shape, and a female screw part is formed here. In addition, a band part (tamper evidence band) (13) is formed at the lower part and is partitioned by intermittent slits (cut lines) (12) running along the circumferential direction. This band part (13) is a part that performs a tamper evidence function together with the above-mentioned iron part (8), and when the cap molding material (7) is placed on the bore part (6), the band part (13) is deformed so as to wrap the iron part (8) from the lower side, and the band part (13) is fitted to the iron part (8) to be integrated. In addition, a sealing material (liner) (14) which is a molding resin is attached to the inner and outer periphery of the top plate part (11). By pushing the upper end of the above-mentioned curled portion (10) against the liner (14) and elastically deforming it, the two are brought into close contact and the opening end of the bore portion (6) is sealed in a liquid-tight or air-tight state. In addition, the pushing of the liner (14) against the curled portion (10), the forming of the above-mentioned female screw portion, and the fitting of the band portion (13) to the steel portion (8) can be performed by a known roll-on capping method in which a cap shaping material (7) is placed on the bore portion (6), a capping pressure is applied from above, and in that state, a forming load is applied from the outer peripheral side of the cap shaping material (7) by an appropriate forming roll.

FIG. 3 illustrates an enlarged cross-sectional view of a curl portion (10) in an embodiment of the present invention. The example shown here is an example of a four-fold folding curl portion, which is formed by extending upward from the screw portion (9) described above and connecting to an inclined wall portion (15) tightened to have a smaller diameter on the upper side. The inclined wall portion (15) is erected so as to be parallel to the central axis (O) of the bore portion (6) on its upper side, and a cylindrical portion that is almost parallel to the central axis (O) of the bore portion (6) forms an inner wall portion (16). A portion on the upper side of the inner wall portion (16) is bent outward in the radial direction of the bore portion (6) to form an upper R portion (17) that is smoothly convex toward the upper side. The boundary between the inner wall portion (16) indicated by a straight line in Fig. 3 and the upper R portion (17) curved outward is the starting portion (18) of the upper R portion (17), and the most forward portion of the upper R portion (17) (i.e., the upper portion in the bottle-shaped can (1)) is the curl top portion (19).

In addition, the radius of curvature of the upper R portion (17) is not uniform, and the radius (R4) of the portions that continue thereto (the portion on the side of the starting portion (18) and the portion on the opposite side thereto) is larger than the radius (R3) of the portions on both sides centered on the curl top portion (19). Accordingly, the length (L1) measured in the radial direction of the bore portion (6) from the inner surface of the inner wall portion (16) to the curl top portion (19) is smaller (L2>L1) than the height (length measured in the direction of the central axis (O) of the bore portion (6)) (L2) of the curl top portion (19) from the above-mentioned starting portion (18).

The outer peripheral wall portion (20) is a portion that extends downward from the upper R portion (17) on the outer peripheral side of the curl portion (10), and since the curl portion (10) has a so-called folding structure, the outer peripheral wall portion (20) is almost parallel to the inner peripheral wall portion (16). The portion on the lower side of the outer peripheral wall portion (20) is bent inward in the radial direction of the bore portion (6) to become a lower R portion (21). This lower R portion (21) is a portion that is curved by almost 180°, and its radius of curvature (R1) may be constant, or it may be an average radius from the start portion on the outer peripheral wall portion (20) side to the end portion on the inner peripheral wall portion (16) side. The center of curvature is indicated by the symbol "P1" in Fig. 3.

The part that is connected to the lower R part (21) and stands upward in Fig. 3 is a folding part (22), and is almost parallel to the inner wall part (16) and the outer wall part (20) described above, so that it contacts or is in close contact with the outer surface of the inner wall part (16). In addition, the part on the upper side of this folding part (22) is also bent outward, so that the leading edge (cut end) (23) of the metal material that constitutes the bottle-shaped can (1) is trapped between the outer wall part (20) and the folding part (22). In addition, the so-called folding of the curled portion (10) in this way can be performed by the method and procedure described in the aforementioned Japanese Patent No. 4293349 and Japanese Patent No. 4375706, and therefore the order of the bending is the opposite of the order described above, and is performed in the following order: bending of the leading edge portion (23) for the folded portion (22), bending at the lower R portion (21), and bending at the upper R portion (17).

As described above, the curl portion (10) configured, unlike the conventional structure, is not supported by the inclined wall portion (15), but is spaced apart from the inclined wall portion (15), and a retreat surface (24) is provided between the curl portion (10) and the inclined wall portion (15). In the embodiment of the present invention, the retreat surface (24) is a surface (part) provided on the lower side of the inner wall portion (16) or the upper side of the inclined wall portion (15) so as not to interfere with the lower side portion, particularly the lower R portion (21), when a load is applied from above to the curl portion (10).

Specifically, it is a portion extending downward from the lowest portion (or a point corresponding to the boundary between the lower R portion (21) and the folded portion (22)) (25) of the portion where the aforementioned folding portion (22) contacts the inner wall portion (16), and when viewed in the cross-sectional view shown in Fig. 3, it is a plane extending straight in the up-and-down direction or a curved surface that is convex toward the inside of the bore portion (6). In other words, when viewed in the cross-sectional view shown in Fig. 3, the retreat surface (24) is a surface having a center of curvature (P2) on the outside of the bore portion (6) and having a radius of curvature (R2) that is larger (including infinity) than the radius of curvature (R1) of the lower R portion (21).

In addition, the center of curvature (P2) is at a height position lower than or equal to the center of curvature (P1) of the lower R portion (21) in the up-down direction along the central axis (O) of the bore portion (6). In the example illustrated in Fig. 3, the center of curvature (P2) of the retreat surface (24) is located lower than the center of curvature (P1) of the lower R portion (21). Therefore, the retreat surface (24) is composed of a cylindrical surface (plane in the cross-sectional view of Fig. 3) (24a) that extends straight down from the lowermost portion (25) of the outer peripheral surface of the inner wall portion (16) to the height position of the center of curvature (P2) of the retreat surface (24), and a curved surface (24b) that is smoothly connected from the cylindrical surface (24a) to the inclined wall portion (15). In addition, when the center of curvature (P1) of the lower R portion (21) and the center of curvature (P2) of the retreat surface (24) are at the same height, the cylindrical surface (plane in the cross-sectional view of Fig. 3) (24a) does not exist and the retreat surface (24) is formed only by the curved surface (24b).

In the above-described curl portion (10) of the embodiment of the present invention, when a cap (4) is attached by roll-on capping, when a bottle-shaped can (1) is dropped upside down, or when it is hit by any falling object, a load from the upper side as shown in Fig. 3 is applied. When such a load is applied, elastic deformation occurs in the inner wall portion (16) or the inclined wall portion (15) or the portion therebetween, and the curl portion (10) may go down as shown in Fig. 3.

In that case, in the structure of the curl portion (10) according to the present invention described above, since the inclined wall portion (15) is not in contact with the lower side of the curl portion (10) (lower R portion (21)), the lower R portion (21) and the inclined wall portion (15) are spaced apart in the upper and lower directions to the extent that the above-mentioned retreat surface (24) is formed, so the curl portion (10) goes down almost straight away. That is, even if the inclined wall portion (15) is shaped such that the outer diameter gradually increases from the lower side, the curl portion (10) is not pushed against the inclined wall portion (15), and therefore, no load is applied to push outward in the radial direction with respect to the lower R portion (21).

In this way, in the structure of the curl portion (10) according to the present invention, when a load is applied from above, the curl portion (10) is maintained in a cylindrical shape with its outer surface extended almost straight, so that the sealing of the liner (14) attached to the upper outer surface of the curl portion (10) by roll-on capping can be maintained in a good state. This also applies when the cap (4) attached to the neck portion (6) is turned in the direction of opening the cap. That is, when the cap (4) is slightly moved upward from the neck portion (6) by being rotated in the direction of opening the cap, the liner (14) attached to the upper outer surface of the curl portion (10) moves upward while remaining attached to the outer surface, so that the sealed state of the bottle-shaped can (1) is maintained. And, when the cap (4) moves upwards to the extent that a gap is created between the liner (14) and the upper surface of the curl portion (10), a break occurs in the slit (cut line) (12) that divides the band portion (13) formed in the cap (4). That is, when the bottle-shaped can (1) is opened, the band portion (13) is inevitably torn, so that a bottle-shaped can (1) having good TE properties can be obtained.

Meanwhile, the load applied from above to the curl portion (10) acts as a moment with the starting portion (18) of the upper R portion (17) as the support point and the curl top portion (19) as the point of action on the upper end of the curl portion (10). The length of the so-called "arm" of the moment is the aforementioned "L1", and is shorter than the aforementioned length (L2) from the starting portion (18) to the curl top portion (19), so the moment is small. In addition, although the portion on the outer side (the tip side) of the curl top portion (19) is supported by the portion from the starting portion (18) to the curl top portion (19), since the length (L2) of that portion is made long as described above, it is possible to suppress deformation in which the portion on the tip side from the curl top portion (19) sags downward or deformation of the curl top portion (19) itself. Therefore, the close contact state between the curl portion (10) and the liner (14) can be maintained, so that the sealing performance and TE performance are good.

Here, examples and comparative examples performed to confirm the effects of the present invention are presented. First, regarding the bottle-shaped cans provided in the examples and comparative examples, a large plate blank was cut from a coil of printed resin-coated metal plate (steel having a thickness of 0.15 mm), and further, a blank of one can was made, and this was rounded, the edge part was welded, and then expanded to create a body part of a three-piece welded can having a can body diameter of φ53 (53 mm). One opening end of the can body was necked, and a shoulder part and a bead part were formed, and drawing processing was performed on the spout cylinder to create a neck part, and a screw part and a curl part were formed here. In addition, necking processing was performed on the opening part on the opposite side, and flanging processing was performed on the leading edge part so that a bottom cover was attached. The shape is shown in Fig. 2. In addition, the curl portion was formed by the method described in the aforementioned Japanese Patent No. 4293349, thereby forming a so-called four-layer folding curl portion. By forming such a curl portion, rust at the cut end of the material, steel, was prevented, and an opening for a bottle-shaped can with a pleasant touch was created.

Using the bottle-shaped can configured in this manner, the function and effect of forming the aforementioned retreat surface (24) were confirmed.

[Example 1]

A curled portion (10) was formed with the center of curvature (P1) of the lower R portion (21) and the center of curvature (P2) of the retreating surface (24) 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 retreat surface (24) was set at a lower position than the center of curvature (P1) of the lower R portion (21), and thus a so-called cylindrical surface (flat surface) (24a) corresponding to the difference in height was continuously formed on the lower side of the inner wall portion (16), and subsequently a curved surface (24b) having a predetermined radius of curvature was formed. A capping pressure was applied to the curl portion (10) by roll-on capping, and the deformation state of the curl portion (10) was evaluated.

[Comparative example]

The part extending downward from the lowest part (or the point corresponding to the boundary between the lower R part (21) and the folded part (22)) (25) of the part where the aforementioned folding part (22) comes into contact with the inner wall part (16) was made into a cross-sectional arc surface centered on the center of curvature (P20) which is higher than the center of curvature (P1) of the lower R part (21). A capping pressure was applied to the curl part (10) by roll-on capping, and the deformation state of the curl part (10) was evaluated.

(Evaluation Results)

Fig. 4 shows the relationship between the height positions (upper and lower positions) (P1y, P2y, P20y) of the centers of curvature in Examples 1 and 2 and the comparative example, the curl shape before the capping pressure, the curl shape after the capping pressure, and the evaluation. In addition, symbol "14" in Fig. 4 indicates a liner. In Example 1, there was no particular change in the curl shape after the capping pressure was applied, and therefore the evaluation was "○", indicating that there were no particular problems as a product. Also, in Example 2, a slight warping occurred in the inner wall portion (16), and a misalignment of the position of the curl portion (10) occurred due to this. However, considering that a concave portion can be formed on the outer surface of the curl portion (10) (the outer surface of the outer wall portion (20)) to accommodate a part of the liner (14), such a misalignment of the position of the curl portion (10) does not particularly affect the adhesion of the liner (14), and therefore the evaluation was given as “○”, which does not present any particular problem as a product. In contrast, in the comparative example, as the curl portion (10) was pushed down, it slid over the inclined wall portion (15), and a deformation occurred in which the outer diameter increased on the lower R portion (21) side. This is a deformation that is the subject of the present invention, and therefore the evaluation was given as “×”, which means that it cannot be made into a product.

Next, the relationship between the length (L1) measured in the radial direction of the bore portion (6) from the inner surface of the inner wall portion (16) to the curl top portion (19) and the height (length measured in the direction of the central axis (O) of the bore portion (6)) (L2) of the curl top portion (19) from the aforementioned starting portion (18) was evaluated.

[Example 3]

In the bottle-shaped can described above, the center of curvature (P2) of the retreating surface (24) was made lower than the center of curvature (P1) of the lower R portion (21), and also each length (L1, L2) was set to “L1>L2”. In other words, the position of the curl top (19) was made farther from the inner wall portion (16). A capping pressure was applied to the curl portion (10) by roll-on capping, and the deformation state of the curl portion (10) was evaluated.

[Example 4]

In the bottle-shaped can described above, the center of curvature (P2) of the retreating surface (24) was made lower than the center of curvature (P1) of the lower R portion (21), and each of the above lengths (L1, L2) was set to “L1 = L2.” In other words, the length between the position of the curl top portion (19) and the inner wall portion (16) was set to an intermediate length. Capping pressure was applied to the curl portion (10) by roll-on capping, and the deformation state of the curl portion (10) was evaluated.

[Example 5]

In the bottle-shaped can described above, the center of curvature (P2) of the retreating surface (24) was made lower than the center of curvature (P1) of the lower R portion (21), and each of the above lengths (L1, L2) was set to “L1<L2”. In other words, the length between the position of the curl top portion (19) and the inner wall portion (16) was made short. Capping pressure was applied to the curl portion (10) by roll-on capping, and the deformation state of the curl portion (10) was evaluated.

(Evaluation Results)

Fig. 5 shows the relative relationship between each length (L1, L2) in Examples 3 to 5, the curl shape before capping pressure, the curl shape after capping pressure, and the evaluation of the curl position. In addition, symbol “14” in Fig. 5 indicates a liner.

In Example 3, a so-called waist bend occurred in the inner wall (16) side of the upper R portion (17), and the lower R portion (21) lowered to that extent. Therefore, it was confirmed that it was necessary to secure a certain degree of dimension in the height direction (direction of the central axis (O) of the diameter portion (6)) of the retreat surface (24) in the present invention. In that sense, the evaluation was given as "acceptable."

In Example 4, since the capping pressure was mainly applied to the inner wall portion (16) and the upper R portion (17) on the inner wall portion (16) side, bending occurred in these portions, and the lower R portion (21) went down accordingly. Accordingly, it was confirmed that it was necessary to secure a certain degree of dimension in the height direction (direction of the central axis line (O) of the diameter portion (6)) of the retreat surface (24) in the present invention. In that sense, the evaluation was given as “A”.

In Example 5, since most of the capping pressure is received by the inner wall portion (16), the inner wall portion (16) was pressed in the vertical direction and bent, but the bending was slight, and the curl portion (10) (lower R portion (21)) did not go down significantly. Therefore, the evaluation was given as “good.”

As shown in the evaluation results of the above-described Examples 1 to 5 and Comparative Examples, in the embodiment of the present invention, it is preferable to make the radius of curvature of the retreat surface (24) larger than the radius of curvature of the lower R portion (21), and further, to set the center of curvature (P2) of the retreat surface (24) below the position of the center of curvature (P1) of the lower R portion (21) in the vertical direction along the central axis (O) of the bore portion (6). In addition, it is preferable to set the relationship between the length (L1) measured in the radial direction of the bore portion (6) from the inner surface of the inner wall portion (16) to the curl top (19) and the height (length measured in the direction of the central axis (O) of the bore portion (6)) (L2) of the curl top (19) from the aforementioned start portion (18) as “L1<L2”.

1 bottle can
2 can body
3 Shoulder
4 caps
5 floor covering
6th floor
7 Cap Sculpture
8 iron fence
9 screw part
10 curls
11th floor
12 slits (cut lines)
13 band section
14 liner
15 Sloping wall section
16 Inner wall
17 Top R section
18 Start
19 Curl Top
20 Outer wall
21 Lower R section
22 Folding side
23 Fleet Edge
24 Retreat
24a cylindrical surface
24b curved surface
25 Bottom
O central axis
P1, P2, P20 center of curvature
R1, R2, R3, R4 radius of curvature

Claims (3)

In the structure of the opening curl portion of a bottle-shaped can, in which a cylindrical bore portion is formed by connecting the upper portion of the can body with a shoulder portion whose diameter gradually becomes smaller from the upper side, and the bore portion includes a screw portion for screw-fitting a cap, a steel portion for fitting a tamper evidence band of the cap below the screw portion, and a curl portion formed at the end of the opening above the screw portion,
The above curl
An inner wall portion extending upward from the screw portion, an upper R portion that is curved outward in the radial direction of the bore portion from the upper end of the inner wall portion, an outer wall portion that extends downward from the upper R portion to be parallel to the inner wall portion, a lower R portion that is curved inward in the radial direction of the bore portion from the lower end of the outer wall portion, a fold-in portion that extends upward from the lower R portion and contacts the outer surface of the inner wall portion, and a front edge portion that is a portion closer to the front end than the fold-in portion and is confined between the inner wall portion and the outer wall portion.
From the inner wall portion above, a slanted wall portion is formed that is connected to the screw portion downward and whose outer diameter gradually increases from the lower portion.
A structure of an opening curl portion of a bottle-shaped can, characterized in that a retreat surface is formed in a portion connecting the inner wall portion to the inclined wall portion, extending downward from the lowest portion where the folding portion comes into contact, and having a center of curvature on the outside of the neck portion, and having a radius of curvature in a cross-section when cut along a plane passing through the center axis of the neck portion, which is larger than the radius of curvature in the cross-section of the lower R portion. In the first paragraph,
A structure of an opening curl portion of a bottle-shaped can, characterized in that, in a vertical direction parallel to the central axis of the above-mentioned opening portion, the center of curvature of the retreating surface is at the same height or a lower position than the center of curvature of the lower R portion. In paragraph 1 or 2,
The upper R portion above has a curl top portion which is the most forward portion in the direction of the central axis of the above-mentioned aperture portion,
A structure of an opening curl portion of a bottle-shaped can, characterized in that a length measured in the radial direction of the bore portion from the inner surface of the inner wall portion to the top of the curl is shorter than a length measured in the direction of the central axis of the bore portion from the beginning of the inner wall portion side of the upper R portion to the top of the curl.