JP2004074170A - Bottle can screw-forming device and bottle can - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly ensure sealability between a mouthpiece part of a bottle can body and a cap covered thereto even when the thread number of a threaded portion is increased. <P>SOLUTION: A swollen portion 23 is provided on an outer circumference of a core 11 in a direction opposite to the screw direction from a screw starting portion 21a of a screw formed portion 21. The swollen part 23 is provided on the outer circumference of the core 11 in a range α of 90° in the direction opposite to the screw direction from the screw starting portion 21a, and continuous to the screw starting portion 21a and gradually inclined inward of a bottle can body 1, and has a first arc 24, a second arc 25, and a third arc 26. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a screw forming apparatus for forming a screw portion for attaching a cap to a mouth portion of a bottle can, and a bottle can having the screw portion.
[0002]
[Prior art]
A so-called bottle can body obtained by drawing a metal can body is formed by forming a base portion at an opening of the bottle can body formed on a bottomed cylinder, and a cap is attached to an outer periphery of the base portion. Screw portion is formed.
[0003]
In order to manufacture a bottle can having such a threaded portion, when a bottomed cylindrical bottle can is formed in advance, the opening of the bottle can is opened as shown in FIG. The diameter is once reduced to form the base 2, and then the diameter is increased by a predetermined distance from the opening end of the base 2 to form the enlarged diameter 2 ′ as shown in FIG. A screw portion 3 is formed at a fixed distance from the opening end by a screw forming device as shown in FIG. In this case, when the screw portion 3 is formed in the base 2, the bulging portion 4 is formed by leaving an enlarged portion where the screw portion 3 is not formed.
[0004]
Although not shown, the conventional screw forming apparatus has a bottle can body with a core abutting on the inner peripheral surface of the base portion 2 and an outer core abutting on the outer peripheral surface of the base portion 2 while sandwiching the base portion 2 therebetween. The screw portion 3 is formed on the outer periphery of the base portion 2 by rotating about the axis of the shaft 1. In this case, the number of turns of the screw portion 3 formed on the base 2 is about 1.7 turns as shown in FIG.
[0005]
After that, the bottle can 1 having the threaded portion 3 formed thereon is subjected to various processes such as performing a curl caulking process of forming the curled portion 8 shown in FIG. After that, when the contents are put into the inside, the cap 5 is attached and closed.
[0006]
[Problems to be solved by the invention]
As described above, in the conventional screw forming apparatus, the core that contacts the inner peripheral surface of the base 2 of the bottle can 1 and the outer core that contacts the outer peripheral surface of the base 2 sandwich the bottle can with each other. By rotating around the axis, the screw part 3 having 1.7 turns is formed on the base part 2 whose diameter has been increased.
[0007]
However, when the number of turns of the screw portion is about 1.7 turns, as shown in FIG. 7, a portion having two screw portions 3 on the peripheral surface of the base portion 2 and a portion having only one screw portion 3. And there was a problem with the difference in the number. That is, if the number of turns is the above, when the cap 5 is attached to the bottle can 1 and the inside of the bottle can 1 is made to have a positive pressure, a pressure for pushing up the cap 5 is applied, and the cap 5 is displaced upward. . Therefore, since the cap 5 is biased with respect to the bottle can 1, the bridge 7 provided between the scores 6 and 6 on the opening end side of the cap 5 is pulled and broken, and so-called bridge breakage occurs. There was a malfunction that occurred.
[0008]
In order to solve the above problem, it has been attempted to increase the number of turns of the screw portion 3 to 2.2 as shown in FIG. When the screw part 3 of 2.2 turns is formed on the base part 2 of the bottle can body 1 in this way, the screw part 3 has three steps between the screw start part 3a and the screw end part 3b of the screw part 3. A thread region will be present.
[0009]
However, in the case where 2.2 thread portions 3 are formed in the bottle can 1, as compared with the case of 1.7 thread portions, as shown in FIG. Since it is located near the portion 8, it is necessary to change the inclined surface 2a between the curl portion 8 and the screw start portion 3a from the state of the dashed line to a gentle shape as shown by the solid line in the base 2. there were.
[0010]
For this reason, when forming the bottle can 1, although the inclined surface 2 a is formed in advance as described above so that the screw start portion 3 a can be surely formed, the screw 2 is screwed onto the base 2 having such an inclined surface 2 a. When the screw part 3 is formed by the molding device, when the base part 2 is viewed from the opening end as shown in FIG. 10, the constituent material on the side opposite to the screw direction from the screw start part 3 a is recessed inside the base part 2. There is a problem that the extreme uneven portion 2b occurs.
[0011]
This is because the core of the conventional screw forming device is provided with a screw forming portion for forming the screw portion 3 in the base 2 together with the outer core, but the inner wall of the base 2 other than the screw forming portion is provided. This is because there is no portion in contact with, and therefore, when the screw portion 3 is formed in the base portion 2, the constituent material of the base portion 2 cannot be restrained.
Therefore, when the cap 5 shown in FIG. 7 is attached to the base 2 in the state where the concave and convex portions 2 b are formed, the gap between the cap 5 and the concave and convex portion 2 b of the base 2 can be sealed with the sealing material in the cap 5. As a result, a problem that the contents of the bottle can 1 leaked occurred.
[0012]
The present invention has been made in view of such circumstances, and an object thereof is to ensure the sealing performance between a base and a cap attached thereto even if the number of turns of a screw is increased. It is another object of the present invention to provide a bottle can body having a screw portion formed by the screw forming apparatus.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the present invention proposes the following means.
The invention according to claim 1 is a core having a screw forming portion for contacting an inner peripheral surface of a mouth portion of a bottle can body and providing a thread portion to be formed on the mouth portion on an outer periphery, and the mouth portion. An outer body having a threaded portion having a shape corresponding to the threaded portion of the core on the outer periphery and having an outer peripheral surface of the base with the core and the outer body. A screw forming device for forming a screw portion from a side toward a can body direction, wherein the core is provided with a screw starting portion in a predetermined range in a direction opposite to the screw direction from a screw starting portion of the screw forming portion. And a bulging portion that is gently inclined inward of the bottle can body.
[0014]
ADVANTAGE OF THE INVENTION According to the screw forming apparatus of the bottle can body which concerns on this invention, since the bulging part is provided, not only the part which suddenly dents from a screw start part like the prior art disappears, but also loose | gentle in the opposite direction from a screw start part. By bulging the cap, it is possible to prevent irregularities from being formed on the outer periphery of the cap, so that when the cap is attached to the cap with the threaded part, the sealing material inside the cap ensures the gap between the cap and the cap. And good sealing properties can be secured over the periphery of the base.
[0015]
According to a second aspect of the present invention, in the screw forming apparatus for a bottle can body according to the first aspect, the bulging portion is 90 degrees from the screw starting portion of the thread forming portion of the core in a direction opposite to the screw direction. Is provided in the range.
[0016]
According to the bottle can body screw forming device according to the present invention, since the bulging portion is provided in a range of 90 degrees in the opposite direction from the screw start portion on the outer periphery of the base portion, the bulge is extremely extreme in the opposite direction from the screw start portion. It is possible to prevent the occurrence of irregularities, and it is possible to further alleviate irregularities due to the screw start portion.
[0017]
The invention according to claim 3 is the bottle forming apparatus according to claim 1 or 2, wherein the bulging portion has an angle of 45 degrees from the screw start portion of the core in a direction opposite to the screw direction. At the position, it has a contour recessed inside the bottle can body with a dimension of 0.2 to 0.3 mm from the thread root of the thread forming portion.
[0018]
ADVANTAGE OF THE INVENTION According to the screw forming apparatus of the bottle can body which concerns on this invention, since it has the profile which is recessed inside by the dimension of 0.2-0.3 mm from the screw root of a screw formation part, a bulge part is a screw part Not only is there no danger of forming a valley, but also the unevenness due to the screw start portion can be further reduced.
[0019]
The invention according to claim 4 is the bottle forming apparatus according to any one of claims 1 to 3, wherein the bulging portion is connected to the screw start portion of the core, and the bottle can body is formed. A second arc centered on the outside of the bottle can body, a second arc centered on the outside of the bottle can body, and a second arc centered on the outside of the bottle can body; And a third arc centered on the inside of the body.
[0020]
According to the screw forming apparatus for a bottle can body according to the present invention, since the bulging portion has the first circular arc, the second circular arc, and the third circular arc, the outer peripheral surface of the base portion is screwed from the screw starting portion. The shape is surely gentle in the direction opposite to the portion, and the unevenness due to the screw start portion can be further reduced.
[0021]
The invention according to claim 5 is a bottle can body in which a screw portion is provided on the outer periphery of the mouth portion of the bottle can body from the tip side of the mouth portion toward the can body direction. In a predetermined range in the direction opposite to the thread direction from the thread start portion of the thread portion, a concavo-convex relief projection is formed which is connected to the thread start portion of the thread portion and which is gently inclined inside the bottle can body. It is characterized by having.
[0022]
ADVANTAGE OF THE INVENTION According to the bottle can body which concerns on this invention, the bulge part is formed in the outer periphery of the base part of a bottle can body in the opposite direction from the screw start part of a screw part, and the roundness of a base part outer periphery is promoted. Therefore, even if the cap is attached, there is no danger of the contents leaking, and high airtightness can be obtained between the cap and the periphery.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 to 5 are views showing a screw forming apparatus according to a first embodiment of the present invention, and FIG. 1 is an explanatory view showing a state where a bottle can is positioned at a position facing the screw forming apparatus. FIG. 2 is an explanatory view showing a state in which the screw forming device forms a screw portion in the base portion of the bottle can body, FIG. 3 is a front view showing a core of the screw forming device, and FIG. 4 is a main part of FIG. FIG. 5 is an enlarged view of the base of the bottle can body viewed from above.
Before explaining the screw forming apparatus 10 of the embodiment shown in FIGS. 1 and 2, the bottle can 1 handled by the screw forming apparatus 10 is for putting therein contents such as carbonated drinks and fruit juice drinks. Then, after being formed into a bottomed cylindrical shape by a thin metal plate made of aluminum or an aluminum alloy, a base 2 having a smaller diameter than the can body is formed at the opening of the bottle can body 1, and thereafter, the base 2 is formed. The threaded portion 3 is formed by the thread forming device 10 around the periphery (see FIG. 6).
[0024]
The screw forming device 10 includes a core 11 that is in contact with the inner peripheral surface of the base 2 of the bottle can 1 and an outer core 12 (outer body) that is in contact with the outer peripheral surface. The screw part 3 is formed around the base part 2 by rotating around the axis O of the bottle can body 1 while sandwiching the base part 2 with the outer core 12.
As shown in FIGS. 1 and 2, the core 11 and the outer core 12 have screw-forming portions 21, 22 having an uneven shape for forming the screw portion 3 on the outer peripheral surface thereof, and correspond to each other in a spiral shape. The bottle cans are formed between the concave and convex shapes by being moved in the radial direction by the cam rollers C1 and C2 which are formed in the respective shapes and move in the radial direction according to the position of the second housing 42 with respect to the first housing 41. The base 2 of the body 1 can be deformed so as to form the screw 3 by sandwiching the base 2.
[0025]
The core 11 and the outer core 12 are provided inside the second housing 42. The second housing 42 is biased and held to the distal end side with respect to the first housing 41 and fixes the third housing 44. A retaining ring 47 is attached to the third housing so as to be rotatable about an axis O. An elastic member 46 urged toward the distal end via a spring 45 is attached to the press ring 47. The elastic member 46 has a conical surface 46a along a tapered shoulder formed on the bottle can 1, and a cylindrical surface 46b along the can body. When pressed, it is pressed against the bottle can 1.
[0026]
In FIGS. 1 and 2, reference numeral 35 denotes a stopper member fixed to the work holding portion 30, and the pressing ring 47 abuts on the stopper member 35 to fix the third pressing member 47. The axially most advanced positions of the housing 44, the second housing 42, and the core 11 and the outer core 12 provided inside the second housing 42 with respect to the work holding portion 30 are determined.
Although not shown in detail, the work holding unit 30 includes a die ring 31 that holds the bottle can 1 by fitting the bottom of the bottle can 1, and a can body of the bottle can 1 that is expanded by air. And a ring-shaped hollow elastic member 32 for tightening and holding a chuck function.
[0027]
As shown in FIG. 1, the screw forming device 10 first moves the bottle can 1 whose bottom is held by the die ring 31 of the work holding unit 30 to the opposing position as shown in FIG. When the cylindrical surface 46b is fitted into the can body from the shoulder of the bottle can body 1 by the advance of 30, the work holder 30 is further advanced and the holding ring 47 contacts the stopper member 35. Then, the advance of the third housing 44 is stopped, and the work holding portion 30 further advances, so that the axial distance between the first housing 41 and the second housing 42 is reduced.
[0028]
At this time, as the first housing 41 advances to a predetermined position as shown in FIG. 2, the first housing 41 moves with respect to the second housing 42, and the cam rollers C1 and C2 move on the slopes 41a and 41b of the first housing. Along, the core 11 moves along with it and comes into contact with the inner peripheral surface of the base 2 of the bottle can 1, and the outer core 12 moves and comes into contact with the outer peripheral surface of the base 2. Thereby, the base 2 is sandwiched between the core 11 and the outer core 12, and in this state, the entire device 10 further rotates around the axis O, so that the screw 3 is formed in the base 2. ing.
[0029]
In this case, the screw part 3 formed on the base part 2 of the bottle can 1 is formed as 2.2 turns in this example as shown in FIG. The uneven screw forming portion 21 provided on the outer periphery of the core 11 is formed in a shape corresponding to the screw portion 3.
In this embodiment, as shown by oblique lines in FIG. 3, on the outer periphery of the core 11, a bulging portion 23 is provided from the screw start portion 21 a of the screw forming portion 21 in a direction opposite to the screw direction. .
[0031]
That is, the bulging portion 23 is provided on the outer periphery of the core 11 in a range α of 90 degrees from the screw start portion 21a of the screw forming portion 21 in a direction opposite to the screw direction, and is continuous with the screw start portion 21a. And a shape that is gently inclined toward the inside of the bottle can. More specifically, the bulging portion 23 is formed to have a first arc 24, a second arc 25, and a third arc 26 as shown in FIG.
[0032]
The first arc 24 is an arc centered on the inside of the bottle can 1, and one end thereof is connected to the screw start portion 21 a of the core 11. The second arc 25 is an arc centered on the outside of the bottle can 1, and one end thereof is connected to the other end of the first arc 24. The third arc 26 is an arc centered on the inside of the bottle can 1, one end of which is connected to the other end of the second arc 25, and the other end of which is connected to the outer peripheral surface of the base 2. Have been.
In this example, in the case of the base 2 to which a cap having a diameter of 38 mm is attached, the radius r1 of the first arc 24 is about 9.6 mm, the radius r2 of the second arc 25 is 10.0 mm, and the radius r3 of the third arc 26. Has a size of about 14.6 mm.
[0033]
Further, the third arc 26 of the bulging portion 23 defines a region including the angle α1 of 45 degrees in the opposite direction from the screw start portion 21a, and further, at the 45 ° angle position, the thread root of the screw forming portion 21 27 has a contour recessed inside the bottle can 1 by a dimension L of 0.2 to 0.3 mm.
3 and 4, P is the axis of the core 11.
[0034]
Since the screw forming apparatus 10 of this embodiment has the above-described configuration, in order to provide the screw portion 3 in the bottle can body 1, first, as shown in FIG. 1, the screw forming apparatus 10 includes a die ring 31 and a ring-shaped hollow elastic member 32. The bottle can body 1 whose bottom is held by the work holding unit 30 is positioned at an opposing position, and the cylindrical surface 46b is fitted into the can body from the shoulder of the bottle can body 1 by the advance of the work holding unit 30, and then Then, the work holder 30 advances further, the holding ring 47 contacts the stopper member 35, the advance of the second housing 42 and the third housing 44 is stopped, and the work holder 30 further advances and the first housing 41 The axial distance from the second housing 42 is reduced.
[0035]
At this time, as the first housing 41 advances to a predetermined position as shown in FIG. 2, the first housing 41 moves with respect to the second housing 42, and the cam rollers C1 and C2 move to the slopes 41a of the first housing, 41b, the core 11 moves along with the inner peripheral part of the base 2 of the bottle can and comes into contact therewith, and the outer core 12 moves and contacts the outer peripheral of the base 2 The base 2 is sandwiched between the core 11 and the outer core 12, and in this state, the entire device further rotates around the axis O, so that the base 2 has a 2.2-turn screw portion as shown in FIG. 3 will be formed.
[0036]
In this case, when the 2.2 thread portion 3 is formed on the base portion 2, the screw start portion 3 a of the thread portion 3 is located near the curl portion 8 provided on the base portion 2. There is a possibility that an extreme uneven portion due to the start portion 3a may occur.
However, the outer periphery of the core 11 is provided with a bulging portion 23 which is gently inclined from the screw starting portion 21a of the screw forming portion 21 toward the inside of the bottle can 1 in a direction opposite to the screw direction. Therefore, when the screw portion 3 is formed, the bulging portion 23 constrains the material on the screw start portion 3a side in the base 2.
[0037]
That is, when the screw start portion 21a of the core 11 and the outer core 12 form the screw start portion 3a as shown in FIG. In addition to preventing the constituent material on the side of the screw start portion 3a from contacting and recessing, the constituent material is pressed in accordance with the shape of the bulging portion 23, whereby the screw start portion 3a of the base 2 has As shown in the figure, the concavo-convex mitigation projection 9 connected to this is formed corresponding to the shape of the bulging portion 23.
[0038]
As a result, when the screw portion 3 is formed on the base portion 2 of the bottle can body 1, the unevenness relief projection 9 is formed continuously with the screw start portion 3a of the screw portion 3, thereby forming the screw start portion 3a. Since the irregularities can be alleviated along the periphery, the bottle can 1 of this shape is then filled with the contents, and when the cap 5 shown in FIG. The space between the cap 5 and the base 2 can be reliably sealed around the periphery, and good sealing performance can be ensured.
[0039]
Further, as shown in FIGS. 3 and 4, the bulging portion 23 is provided in a range α of 90 degrees from the screw starting portion 21 a of the screw forming portion 21 in the core 11 in a direction opposite to the screw direction. Therefore, when the screw portion 3 is formed as shown in FIG. 5, unevenness due to the screw start portion 3a can be more reliably alleviated. As described above, when the bulging portion 23 is provided over the range α of 90 degrees, even if the diameter of the base 2 is slightly changed, it is possible to surely cope with it even if the diameter is slightly changed. It can be applied to the body 1.
[0040]
Moreover, since the bulging portion 23 has a contour indented inward with a dimension L of 0.2 to 0.3 mm from the thread root 27 of the thread forming portion 21 as shown in FIG. There is no danger of forming a thread root in the opposite direction from the part.
Further, the bulging portion 23 includes a first arc 24 connected to the screw start portion 21a, a second arc 25 connected to the first arc 24, and a third arc 26 connected to the second arc 25. As a result, the outer peripheral surface of the base 2 has a gentle shape from the screw start portion 3a in the direction opposite to the screw portion 3, and the unevenness due to the screw start portion 3a can be further reduced.
[0041]
In the illustrated embodiment, the values of the radii r1 to r3 of the first to third circular arcs 24 to 26 constituting the bulging portion 23 are appropriately selected according to the diameter of the base 2 of the bottle can 1. However, the present invention is not limited to the illustrated example.
Further, in the illustrated embodiment, an example is shown in which the screw forming apparatus 10 uses the outer core 12 that rotates around the axis O together with the core 11 while abutting on the outer periphery of the base 2. Alternatively, another outer body that can form the screw portion 3 together with the core 11 may be used, and is not limited to the illustrated example.
[0042]
【The invention's effect】
As described above, according to the first aspect of the present invention, the core has a bulge that is gently inclined toward the inside of the bottle can body in a direction opposite to the screw direction from the screw start portion of the screw forming portion. The bulging portion is configured to prevent the occurrence of extreme irregularities on the screw start portion side on the outer periphery of the base portion of the bottle can body. Therefore, even if the number of turns of the screw portion provided on the base portion is increased, an effect that the sealing performance between the base portion of the bottle can body and the cap attached to the base can be properly secured can be obtained.
[0043]
According to the second aspect of the invention, there is obtained an effect that no extreme unevenness is generated in the opposite direction from the screw start portion in the mouth portion of the bottle can body, and the unevenness due to the screw start portion can be further reduced.
[0044]
According to the third aspect of the invention, not only there is no possibility that the bulging portion forms a valley of the screw portion, but also the effect that the unevenness due to the screw start portion can be further reduced can be obtained.
[0045]
According to the invention according to claim 4, since the bulging portion has the first circular arc, the second circular arc, and the third circular arc, the outer peripheral surface of the base portion is in a direction opposite to the screw portion from the screw start portion. The shape becomes surely gentle, and the effect that the unevenness due to the screw start portion can be further reduced can be obtained.
[0046]
According to the invention according to claim 5, the roundness of the outer periphery of the base portion is promoted by forming the bulging portion on the outer periphery of the base portion of the bottle can body in the opposite direction from the screw start portion of the screw portion. Therefore, even when the cap is attached, there is no danger of the contents leaking, and there is an effect that high airtightness can be obtained between the cap and the periphery.
[Brief description of the drawings]
FIG. 1 is a view showing a screw forming apparatus according to a first embodiment of the present invention, and is an explanatory view showing a state where a bottle can is positioned at a position facing the screw forming apparatus.
FIG. 2 is an explanatory view showing a state in which a screw forming device forms a screw portion on a mouth portion of a bottle can body.
FIG. 3 is a front view showing a core of the screw forming apparatus.
FIG. 4 is an enlarged view of a main part of FIG. 3;
FIG. 5 is an explanatory view of the base of the bottle can as viewed from above.
FIG. 6 is an explanatory view showing a process until a screw portion is formed on the bottle can body.
FIG. 7 is an explanatory view of attaching a cap to a bottle can having a screw portion.
FIG. 8 is an explanatory view when a three-stage screw portion is provided on a bottle can body.
FIG. 9 is a schematic enlarged view showing a relationship between a screw start portion and a curl portion of a screw portion provided on a base portion of a bottle can body by a conventional screw forming device.
FIG. 10 is a view of the base of the bottle can as viewed from the opening end.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Bottle can body 2 Base part 3 Screw part 3a Screw start part of screw part 5 Cap 8 Curl part 9 Unevenness relief projection 10 Screw forming device 11 Core 12 Outer (outer body)
21 Screw forming part 21a of core Core screw starting part 23 of screw forming part Swelling part 24 First circular arc 25 Second circular arc 26 Third circular arc

Claims (5)

A core having a screw forming portion for providing a screw portion to be formed on the base portion on the outer periphery, abutting against the inner peripheral surface of the base portion of the bottle can body, and abutting on the outer peripheral surface of the base portion, and An outer body having a screw forming portion having a shape corresponding to the screw forming portion of the core on the outer periphery,
A screw forming device that forms a screw portion from the opening end side toward the can body direction with respect to the outer periphery of the die portion by the core and the outer body,
The core is connected to the screw start portion in a predetermined range opposite to the screw direction from the screw start portion of the screw forming portion, and the bulge gently slopes inward of the bottle can body. A screw forming apparatus for a bottle can body, comprising a part. The screw forming apparatus for a bottle can body according to claim 1,
The said bulge part is provided in the range of 90 degrees from the said screw start part of the screw formation part in a core in the direction opposite to the screw direction, The bottle can body screw forming apparatus characterized by the above-mentioned. The screw forming apparatus for a bottle can body according to claim 1 or 2,
The bulging portion is a bottle can having a dimension of 0.2 to 0.3 mm from the thread root of the thread forming portion at an angle of 45 degrees from the thread starting portion of the core in a direction opposite to the thread direction. An apparatus for screw-forming a bottle can, characterized in that the apparatus has a contour depressed inside the body. The screw forming apparatus for a bottle can according to any one of claims 1 to 3,
The bulging portion is connected to the screw starting portion of the core, and a first arc centered on the inside of the bottle can, and connected to the first arc, centered on the outside of the bottle can. And a third arc connected to the second arc and the base portion and centered on the inside of the bottle can body. . In a bottle can body provided with a screw portion on the outer periphery of the mouth portion of the bottle can body toward the can body from the tip side of the mouth portion,
On the outer periphery of the base, from the screw start part of the screw part, in a predetermined range opposite to the screw part direction, the screw part of the screw part is connected to the screw start part, and gently sloped inward of the bottle can body. A bottle can body characterized by forming a projection for reducing unevenness.

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