BOTTLE-SHAPED CAN WITH CAP AND MANUFACTURING APPARATUS THEREOF

Abstract

A bottle-shaped can includes a cap having an excellent sealing ability but easy to be opened. A top section includes a leading end section as an upper end of a neck portion, a diametrically-largest section formed beneath the leading end section, a diametrically-shrunk section extending downwardly from the diametrically-largest section, and an outer circumferential wall section extending downwardly from the diametrically-shrunk section. The leading end section, the diametrically-largest section, and diametrically-shrunk section form a smooth curved surface. A curvature of the diametrically-largest section in a cross-section is zero or negative value, given that a curvature of the diametrically-shrunk section is positive value. A flexion section is formed between the diametrically-shrunk section and the outer circumferential wall section. The outer diameter of the outer circumferential wall section in which the curvature is zero or negative value is larger than an outer diameter of the flexion section.

Claims

1. A bottle-shaped can with a cap, comprising: a neck portion on which a thread is formed, and on which the cap is mounted; and a curled portion formed on an upper end portion of the neck portion, to which a sealing member affixed to an inner surface of the cap is contacted tightly to seal the neck portion; wherein the curled portion includes a smooth top section formed by folding an end portion of metallic seat forming the neck portion radially outwardly, wherein: the top section includes a leading end section as an upper end of the neck portion, a diametrically-largest section formed beneath the leading end section in which an outer diameter is largest, a diametrically-shrunk section extending downwardly from the diametrically-largest section in which an outer diameter is reduced gradually, and an outer circumferential wall section extending downwardly from the diametrically-shrunk section, the leading end section, the diametrically-largest section, and the diametrically-shrunk section form a smooth curved surface, a curvature of the outer circumferential wall section in a cross-section along a plane passing through a center axis of the neck portion is zero or negative value, given that a curvature of the diametrically-shrunk section is positive value, a flexion section is formed between the diametrically-shrunk section and the outer circumferential wall section, and the outer diameter of the outer circumferential wall section in which the curvature is zero or negative value is larger than an outer diameter of the flexion section.

2. The bottle-shaped can with the cap as claimed in claim 1, wherein the sealing member is contacted closely to the surface of the curled portion from the leading end section to at least a portion below the flexion section of the outer circumferential wall section.

3. The bottle-shaped can with the cap as claimed in claim 1, wherein the outer circumferential wall section in which the curvature is zero or negative value is shaped into a tapered shape in which the outer diameter is gradually increased downwardly, or a curved shape expanding downwardly.

4. The bottle-shaped can with the cap as claimed in claim 3, wherein a taper angle of the outer circumferential wall section in which the curvature is zero or negative value, or an angle between a tangent line at a curve starting point where the outer circumferential wall section starts expanding and the center axis is equal to or larger than 1 degree but equal to or smaller than 15 degrees.

5. The bottle-shaped can with the cap as claimed in claim 3, wherein an outer diameter of a lower sealing end as a lowest portion, to which the sealing member is contacted in the outer circumferential wall section shaped into the tapered shape or the curved shape expanding downwardly, is equal to or larger than the outer diameter of the diametrically-largest section.

6. The bottle-shaped can with the cap as claimed in claim 1, wherein a lower end arcuate section is formed beneath the outer circumferential wall section, and a curvature of the lower end arcuate section is positive value so that the cross-section of the lower end arcuate section along the plane passing through the center axis of the neck portion expands radially outwardly.

7. The bottle-shaped can with the cap as claimed in claim 6, wherein the lower sealing end as the lowest portion to which the sealing member is contacted is situated at a predetermined site of a surface of the lower end arcuate section.

8. The bottle-shaped can with the cap as claimed in claim 7, wherein an outer diameter of the lower sealing end is equal to or larger than the outer diameter of the diametrically-largest section.

9. A manufacturing apparatus of a bottle-shaped can with a cap, comprising: a neck portion on which a thread is formed, and on which the cap is mounted; and a curled portion formed on an upper end portion of the neck portion, to which a sealing member affixed to an inner surface of the cap is contacted tightly to seal the neck portion, wherein the curled portion has a top section including a leading end section as an upper end of the neck portion, a diametrically-largest section formed beneath the leading end section in which an outer diameter is largest, a diametrically-shrunk section extending downwardly from the diametrically-largest section in which an outer diameter is reduced gradually, and an outer circumferential wall section extending downwardly from the diametrically-shrunk section, wherein: the manufacturing apparatus comprises a forming tool that pushes a cylindrical folded portion bent outwardly from the neck portion toward an outer circumferential surface of the neck portion to form the curled portion, the forming tool includes an inner tool that is inserted into the neck portion to maintain a shape of the neck portion from inside, and an outer tool that pushes the folded portion toward the neck portion from radially outer side, the inner tool includes a shaft portion which is inserted into the neck portion, and an annular flat portion to which a leading end of the folded portion formed on the neck portion is contacted, the outer tool includes a projection that is isolated from the annular flat portion at a distance wider than a length between the leading end section and the diametrically-largest section in a direction along a center axis of the neck portion, and that pushes the folded portion toward the neck portion from radially outer side, and the neck portion engaged with the inner tool is rotated along the outer tool to form the curled portion.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0019] FIG. 1 is a front view showing one example of a bottle-shaped can according to the present invention.

[0020] FIG. 2 is a schematic illustration showing a step of forming a can trunk in a manufacturing process.

[0021] FIG. 3 is a schematic illustration showing steps of forming a shoulder portion and a diametrically-smaller cylindrical portion in the manufacturing process.

[0022] FIG. 4 is a process chart showing a trimming step, a curling step, a threading step, and a bead forming step.

[0023] FIG. 5(a) is a partial cross-sectional view showing one example of the curled portion of the bottle-shaped can according to the present invention, and FIG. 5(b) is a partially enlarged cross-sectional view showing the curled portion shown in FIG. 5(a).

[0024] FIG. 6 is a partial schematic illustration showing an example in which a sealing linear is contacted tightly to the vicinity of a lower end of the curled portion.

[0025] FIG. 7 is a partial schematic illustration showing other examples of the curled portion.

[0026] FIG. 8 is a cross-sectional view showing an inner tool and an outer tool of the manufacturing apparatus according to the present invention.

DESCRIPTION OF EMBODIMENT(S)

[0027] A bottle-shaped can according to the present invention is made of metallic material such as a surface treatment steel sheet and an alloy-coated steel sheet. The surface treatment steel sheet includes an aluminum sheet, an aluminum alloy sheet, a tin free steel sheet and so on. The alloy-coated steel sheet includes a tin sheet, a chrome-coated steel sheet, an aluminum-coated steel sheet, a nickel-coated steel sheet and so on. At least one surface of the metallic material to be shaped into an inner surface of the bottle-shaped can is coated with a thermoplastic resin or a coating material. One example of the bottle-shaped can is shown in FIG. 1. A bottle-shaped can 1 shown therein comprises a diametrically-larger cylindrical trunk portion 2 as a main body, a shoulder portion 3 formed continuously from an upper end of the trunk portion 2, and a diametrically-smaller cylindrical neck portion 4 formed continuously from an upper end of the shoulder portion 3 to be situated on a center portion of the shoulder portion 3. A bottom lid 5 is seamed to a bottom of the bottle-shaped can 1. The neck portion 4 has an opening 6 on its leading end portion, and a cap 7 is mounted on the neck portion 4 to close the opening 6. In order to use the opening 6 of the neck portion 4 as a container mouth, a curled portion 8 having a round or an oval cross-section is formed on the opening 6 by folding an opening edge of the neck portion 4 outwardly into two or three layers in such manner as to confine the edge in the curled portion 8. A thread 9 as a male thread is formed on the neck portion 4 so that the cap 7 is mounted on the neck portion 4 in a resealable manner.

[0028] A material of the cap 7 mounted on the neck portion 4 comprises a top panel 7a and a cylindrical skirt portion 7b, and a liner 7c is affixed to an inner surface of the cap 7 (i.e., the top panel 7a). A circumferential corner of the top panel 7a is swaged, and a thread groove is formed on the skirt portion 7b by pressing the skirt portion 7b by a thread roller (not shown) along a thread 9 of the neck portion 4. The liner 7c is formed by applying elastic resin to the inner surface (and in the vicinity thereof). Therefore, the liner 7c is brought into close contact to the curled portion 8 by swaging the circumferential corner of the top panel 7a so that the opening 6 of the neck portion 4 is sealed tightly. An easily breakable portion 7e includes horizontal slits and bridges formed alternately in a circumferential direction on a lower portion of a skirt portion 7b of the cap 7, and a pilfer-proof band 7d is detached from the skirt portion 7b by rupturing the bridges.

[0029] An annular bead (or emboss) 10 is formed below the thread 9, and an annular groove 11 is formed below the bead 10. The bead 10 and the groove 11 are also called the stepped portion 12.

[0030] Here will be explained a manufacturing process of the trunk portion 2 and the neck portion 4 of the bottle-shaped can 1. Turning to FIG. 2, there is shown a forming process of a can trunk 20 as an intermediate product. First of all, a blank 21 is punched out of a thin metallic sheet material, and the blank 21 is drawn into a shallow cup-shaped interim product 22. Thereafter, the interim product 22 is shaped into the can trunk 20 having an outer diameter corresponding to that of the aforementioned trunk portion 2 by further applying a drawing and ironing to the interim product 22. In this phase, as illustrated in FIG. 3, the can trunk 20 has a bottom 23. A center portion of the bottom 23 is drawn and ironed to be gradually stretched while reducing a diameter of a circumferential corner of the bottom 23. As a result, a shoulder portion 24 and a diametrically-smaller cylindrical portion 25 are formed.

[0031] The diametrically-smaller cylindrical portion 25 is to be shaped into the neck portion 4, and for this purpose, the diametrically-smaller cylindrical portion 25 is further processed to have a capping function and a tamper-evidence function. A forming process of the neck portion 4 is schematically shown in FIG. 4. First of all, in order to form a container mouth on a leading end portion 25b of the diametrically-smaller cylindrical portion 25, a bottom 25a is cut out (at a trimming step) to form an opening. In order to confine a sharp opening edge inside of the curled portion having a round cross-section, the opening edge of the diametrically-smaller cylindrical portion 25 is folded outwardly into e.g., three layers. According to the example shown in FIG. 4, the curled portion is formed by four curling steps. At the first curling step, the leading end portion 25b having the opening edge is bent outwardly to form a flange, and at the second curling step, the flange is further bent downwardly so that a folded portion 25c of two layers is formed. Then, at the third curling step, the two-layered folded portion 25c is bent outwardly so as to form a flange of two layers. Thereafter, at the fourth curling step, the two-layered folded portion 25c thus formed into the flange is further folded (or curled) downwardly outwardly so that the opening edge of the two-layered folded portion 25c is confined in the curled portion.

[0032] During the forming process of the curled portion, a threading is executed, and a bead forming is executed after the threading (e.g., after the final curling step) to provide the tamper evidence function. In other words, the curling process is completed after the threading step, and then the bead forming step is executed.

[0033] The curled portion 8 formed by the above-explained four steps will be explained in more detail. One example of the curled portion 8 according to the present invention is shown in FIG. 5, in which FIG. 5(a) shows the cap 7 is mounted on the neck portion 4, and FIG. 5(b) shows a portion of the curled portion 8 in an enlarged scale. As described, the curled portion 8 is formed by folding the opening edge of the diametrically-smaller cylindrical portion 25 outwardly so that a top section 8a of the curled portion 8 is curved smoothly at a predetermined curvature to have a predetermined width (i.e., thickness), and to form a leading end section 8b. A surface of the top section 8a bulges from the leading end section 8b toward radially outwardly and downwardly. Specifically, the top section 8a has an arcuate cross-section along a plane passing through a center axis Lc of the neck portion 4. The arcuate surface of the top section 8a extends downwardly from a diametrically-largest section 8c at which an outer diameter of the top section 8a is largest. That is, a portion of the outer surface of the top section 8a below the diametrically-largest section 8c is situated radially inner side of the diametrically-largest section 8c. The portion of the top section 8a situated radially inner side of the diametrically-largest section 8c will be called the diametrically-shrunk section 8d.

[0034] An outer circumferential wall section 8e is formed at a portion predetermined distance lower than the diametrically-largest section 8c. That is, the outer circumferential wall section 8e extends downwardly from the diametrically-shrunk section 8d. A curvature of the outer circumferential wall section 8e is different from a curvature of a portion in the vicinity of the diametrically-largest section 8c. Specifically, given that the curvature of the portion in the vicinity of the diametrically-largest section 8c (in the cross-section along the plane passing through the center axis Lc, same is applied in the following explanation) is positive value, the curvature of the outer circumferential wall section 8e is 0 or negative value. That is, the curvature is changed at a flexion section 8f. For example, given that a thickness of the curled portion 8 is approximately 0.3 mm, a curvature radius R0 of a portion from the leading end section 8b to the flexion section 8f via the diametrically-largest section 8c and the diametrically-shrunk section 8d is approximately 0.2 mm to 1 mm, and a length 1 from the leading end section 8b to the flexion section 8f along the center axis Lc is approximately 0.1 mm to 1.5 mm. The flexion section 8f may also be formed into an arcuate shape whose center of curvature is situated outside of the top section 8a. Instead, the flexion section 8f may also be formed into a complex arcuate shape including arcuate portions having different curvatures. In those cases, for example, a curvature radius of the flexion section 8f is approximately 0.5 mm to 5 mm.

[0035] The outer circumferential wall section 8e is a substantially straight portion extending along the center axis Lc whose curvature is 0 or substantially 0. Specifically, an angle between a generatrix of an upper end of the outer circumferential wall section 8e beneath the flexion section 8f (i.e., a vertical tangent line in the cross-section along the plane passing through the center axis Lc) and the center axis Lc is 0 to 15 degrees. That is, the outer circumferential wall section 8e is shaped into a cylindrical shape or a tapered shape in which an outer diameter thereof increases toward a lower portion. Preferably, a taper angle of the outer circumferential wall section 8e is set within a range from 1 degree to 30 degrees. More preferably, a taper angle of the outer circumferential wall section 8e is set within a range from 1 degree to 15 degrees. If the taper angle of the outer circumferential wall section 8e is wider than 30 degrees, the liner 7c may not be contacted tightly to the diametrically-shrunk section 8d.

[0036] The outer circumferential wall section 8e is not necessarily to be shaped accurately into the tapered shape. According to the present invention, the outer circumferential wall section 8e may also be shaped into a curved shape (expanding downwardly) similar to the tapered shape. In this case, an angle between the tangent line at a curve starting point of the present invention at which the outer circumferential wall section 8e starts expanding and the center axis Lc corresponds to the aforementioned taper angle. As the aforementioned taper angle, according to the present invention, the angle at the curve starting point is also set within a range from 1 degree to 30 degrees. Preferably, the angle at the curve starting point is set within a range from 1 degree to 15 degrees.

[0037] A corner portion of the cap 7 is swaged to the vicinity of an intermediate portion of the curled portion 8 of the neck portion 4 in the vertical direction so that the liner 7c is contacted closely to the outer circumferential wall section 8e over to a portion far below the flexion section 8f. A lower end of the portion of the outer circumferential wall section 8e to which the liner 7c is contacted will be called a lower sealing end 8g. Given that the outer circumferential wall section 8e is shaped into a cylindrical shape, an outer diameter of the lower sealing end 8g is identical to an outer diameter of the flexion section 8f. By contrast, given that the outer circumferential wall section 8e is shaped into a tapered shape or a curved shape expanding downwardly, the outer diameter of the lower sealing end 8g is increased to be larger than the outer diameter of the flexion section 8f, and to be identical to or greater than an outer diameter of the diametrically-largest section 8c, according to the taper angle or the angle at the curve starting point.

[0038] As illustrated in FIG. 5(a), in the bottle-shaped can 1 having the curled portion 8, the liner 7c affixed to the inner surface of the cap 7 is contacted closely to the outer surface of the curled portion 8 from a radially inner side of the leading end section 8b to the lower sealing end 8g. Specifically, since the flexion section 8f shrinks radially inwardly from the diametrically-largest section 8c, the liner 7c is deformed flexibly to be contacted tightly to the portion between the diametrically-largest section 8c and the diametrically-shrunk section 8d in such a manner as to hold (or fasten) the portion between the diametrically-largest section 8c and the diametrically-shrunk section 8d. When the cap 7 is deformed by a pressure rise in the bottle-shaped can 1, the liner 7c is brought into contact more tightly to those sections (especially to the diametrically-shrunk section 8d). Therefore, the sealing ability of the bottle-shaped can 1 can be improved by shaping the curled portion 8 into the above-explained shape.

[0039] In addition, the corner portion of the cap 7 is swaged partially so that the curled portion 8 is fastened tightly by the liner 7c, and a fastening load is received mainly by the diametrically-largest section 8c. Given that the outer circumferential wall section 8e is shaped into the tapered shape or the curved shape expanding downwardly, the fastening load is also received by the lower sealing end 8g. That is, a fastening force of a portion of the liner 7c expanding toward the flexion section 8f is not as strong as a fastening force of the liner 7c covering the diametrically-largest section 8c. Therefore, when the cap 7 is rotated to be dismounted from the neck portion 4, a torque (or force) required to expand the portion of the liner 7c expanding toward the flexion section 8f to the outer diameter of the diametrically-largest section 8c will not be increased significantly.

[0040] Thus, according to the embodiment of the present invention, the liner 7c is brought into contact tightly to the diametrically-shrunk section 8d when the cap 7 is deformed by a pressure rise in the bottle-shaped can 1. To this end, the flexion section 8f is shrunk (or deformed) radially inwardly only slightly. For this reason, an adhesion area of the liner 7c to the diametrically-shrunk section 8d can be reduced when a static friction is generated in an initial phase of rotation of the cap 7, and an increase in an opening torque of the cap 7 can be prevented. In addition, in the curled portion 8 having the above-explained structure, the liner 7c is also contacted tightly to the outer circumferential wall section 8e extending below the flexion section 8f. For this reason, a contact area of the liner 7c to the curled portion 8 can be enlarged to enhance the sealing ability. Further, since the outer circumferential wall section 8e is shaped into the tapered shape or the curved shape expanding downwardly, an end section of the liner 7c is not situated radially inner side. For this reason, the opening torque of the cap 7 is not increased.

[0041] In the example shown in FIG. 5, the curled portion 8 is formed in such a manner that a folded leading edge of the two-layered folded portion 25c is brought into contact to a tapered portion (or a diametrically reduced portion) 13 extending from the curled portion 8 to the thread 9. Consequently, the outer circumferential wall section 8e is expanded outwardly due to spring back at a cylindrical portion of an inner circumferential side of the curled portion 8 and the tapered portion 13. According to the example shown in FIG. 5, therefore, the outer circumferential wall section 8e can be formed easily in such a manner as to increase the outer diameter thereof equal to or larger than the outer diameter of the flexion section 8f. In addition, a vertical load can be received by the tapered portion 13 on the occasion of mounting the cap 7 on the neck portion 4 by a so-called roll-on capping method. Therefore, a buckling strength of the curled portion 8 or the neck portion 4 can be enhanced.

[0042] As illustrated in FIG. 6, according to the present invention, the liner 7c may also be contacted tightly to a lower portion of the curled portion 8. According to the example shown in FIG. 6, the curled portion 8 is shaped such that a lower end arcuate section 8h is formed beneath the outer circumferential wall section 8e. The lower end arcuate section 8h is formed by pushing a vertically intermediate portion of the curled portion 8 from a radially outer side at the final curling step. Consequently, the lower end arcuate section 8h is slightly expanded radially outwardly from the outer circumferential wall section 8e so that a cross-sectional shape of the lower end arcuate section 8h along the plane passing through the center axis Lc of the neck portion 4 is expanded radially outwardly. Accordingly, a curvature center of an outer surface of the lower end arcuate section 8h is situated inside of the neck portion 4, and a curvature of the lower end arcuate section 8h is positive value.

[0043] The liner 7c extends to the lower end arcuate section 8h while being contacted tightly to the outer surface of the lower end arcuate section 8h at least partially. In the example shown in FIG. 6, the lower sealing end 8g is situated on the surface of the lower end arcuate section 8h. The lower sealing end 8g may also be situated on a diametrically-largest portion of the lower end arcuate section 8h or in the vicinity thereof, and an outer diameter D8h of the lower end arcuate section 8h may be equal to or larger than an outer diameter D8c of the diametrically-largest section 8c.

[0044] According to the example shown in FIG. 6, a contact area of the liner 7c to the curled portion 8 may be enlarged so that the neck portion is sealed certainly. In addition, since the diametrically-shrunk section 8d and the flexion section 8f are formed, the bottle-shaped can 1 may be maintained in a liquid-tight condition even if an internal pressure of the bottle-shaped can 1 is high. Further, since the diametrically-largest section 8c and the lower end arcuate section 8h protrude outwardly from the diametrically-shrunk section 8d to establish the fastening force of the liner 7c, a required load to expand the liner 7c radially outwardly when dismounting the cap 7 is rather small. For these reasons, the sealing ability of the cap 7 can be enhanced but the cap 7 can be dismounted easily.

[0045] Other examples of the curled portion 8 is shown in FIG. 7. In the example shown in FIG. 7(a), the leading edge of the two-layered folded portion 25c is isolated slightly from the cylindrical portion of the inner circumferential side of the curled portion 8 and the tapered portion 13. In this case, the two-layered folded portion 25c is elastically expanded radially outwardly at around the flexion section 8f, therefore, the outer circumferential wall section 8e having an outer diameter equal to or larger than that of the flexion section 8f can be formed easily.

[0046] In the example shown in FIG. 7(b), the curled portion 8 is shaped into a hollow ring shape in which the leading edge of the leading end portion 25b is brought into contact to the tapered portion 13. The diametrically-largest section 8c is formed in the top section 8a by bending the leading end portion 25b outwardly, and the outer circumferential wall section 8e having a cylindrical shape, a tapered shape, or a curved shape expanding downwardly is formed beneath the diametrically-largest section 8c by applying a forming load thereto from the radially outer side. The diametrically-shrunk section 8d extends downwardly from the diametrically-largest section 8c, and the flexion section 8f is formed at a boundary between the diametrically-shrunk section 8d and the outer circumferential wall section 8e. Specifically, the outer circumferential wall section 8e is shaped such that the lower sealing end 8g is situated at an intermediate portion in the vertical direction. In the bottle-shaped can 1 according to the example shown in FIG. 7(b), therefore, the sealing ability of the cap 7 can be enhanced but the cap 7 can be dismounted easily, as the foregoing examples shown in FIGS. 5 and 7(a).

[0047] In the example shown in FIG. 7(c), the hollow portion of the curled portion 8 is shaped into a substantially round shape. In this case, the leading end of the portion bent outwardly is situated radially inner side of the neck portion 4, and a forming load is applied to an upper portion of the leading end from radially outer side to form the outer circumferential wall section 8e having a cylindrical shape, a tapered shape, or a curved shape expanding downwardly. Consequently, the diametrically-shrunk section 8d and the flexion section 8f are formed from top down between the diametrically-largest section 8c and the outer circumferential wall section 8e. In the bottle-shaped can 1 according to the example shown in FIG. 7(c), therefore, the sealing ability of the cap 7 can be enhanced but the cap 7 can be dismounted easily, as the foregoing examples shown in FIGS. 5, 7(a), and 7(b).

[0048] Next, here will be explained a manufacturing apparatus for manufacturing the bottle-shaped can 1 having the curled portion 8. According to the present invention, the curled portion 8 is formed by folding or rounding the leading end portion 25b having the opening edge. At the final forming step, the flange portion expanded radially outwardly is pushed radially inwardly while restricting a position of a leading end of the flange portion in the direction along the center axis Lc. In order to execute the final forming step, the manufacturing apparatus according to the present invention is provided with an inner tool 30 and an outer tool 31 as forming tools. One example of the manufacturing apparatus for executing the final forming step of the curled portion 8 is shown in FIG. 8.

[0049] The inner tool 30 comprises a shaft portion 30a that is inserted into the neck portion 4 on its leading end section, and an annular flat portion 30b that is expanded radially outwardly on its base portion (i.e., a base end section). For example, the folded portion 25c formed by folding the opening end portion of the diametrically-smaller cylindrical portion 25 radially outwardly into two layers (corresponding to a cylindrical replicated portion of the present invention) comes into contact to the annular flat portion 30b. On the other hand, the outer tool 31 is a ring-shaped tool whose inner diameter is larger than the curled portion 8, and is supported by a bearing 32 in a rotatable manner. In addition, the inner tool 30 and the outer tool 31 are allowed to move relatively to each other between a position at which the inner tool 30 and the outer tool 31 are aligned coaxially to each other, and a position at which the inner tool 30 and the outer tool 31 are positioned eccentrically to each other. The outer tool 31 is adapted to push the folded portion 25c toward the outer circumferential surface of the neck portion, and to this end, the outer tool 31 comprises a projection 31a formed on an inner circumferential surface at a leading end portion. A length of the outer tool 31 in the direction along the center axis Lc is substantially identical to that of the folded portion 25c. A predetermined clearance C is maintained between the projection 31a and the annular flat portion 30b of the inner tool 30 in the direction along the center axis Lc. Specifically, the clearance C is set wider than a length between the leading end section 8b and the diametrically-largest section 8c in the direction along the center axis Lc. That is, the manufacturing apparatus is adapted to apply a forming load to the portion of the neck portion 4 at a distance corresponding to the clearance C away from (i.e., below) the leading end portion from radially outer side.

[0050] In the manufacturing apparatus shown in FIG. 8, the shaft portion 30a of the inner tool 30 is inserted into the diametrically-smaller cylindrical portion 25 from the leading end side so that the folded portion 25c is brought into contact to the annular flat portion 30b. In this situation, the inner tool 30 and the outer tool 31 are situated coaxially to each other while being isolated away from each other. Thereafter, the inner tool 30 is rotated together with the neck portion 4 fitted thereon while moving relatively and in parallel to the outer tool 31. Consequently, the folded portion 25c is partially clamped between a portion of the projection 31a of the outer tool 31 and the shaft portion 30a of the inner tool 30.

[0051] Since the outer tool 31 is supported by the bearing 32 in a rotatable manner and the inner tool 30 is being rotated, the outer tool 31 is rotated together with the neck portion 4. That is, the neck portion 4 or the folded portion 25c is rotated relatively along the projection 31a of the outer tool 31. In this situation, the lading end portion of the neck portion 4 (or the curled portion 8) is brought into contact to the annular flat portion 30b of the inner tool 30, therefore, the neck portion 4 does not slide on the annular flat portion 30b. By contrast, if a portion corresponding to the annular flat portion 30b is formed on the outer tool 31, the neck portion 4 would be rotated relatively to the outer tool 31 while sliding thereon. In this case, therefore, the leading end portion of the neck portion 4 or the curled portion 8 would be damaged. According to the present invention, therefore, such damage of the neck portion 4 or the curled portion 8 can be reduced or suppressed.

[0052] The folded portion 25c is entirely bent radially inwardly by rotating the neck portion 4 360 degrees or more, and consequently the curled portion 8 is formed. In this situation, since the clearance C is maintained between the annular flat portion 30b of the inner tool 30 and the projection 31a of the outer tool 31, the leading end potion of the curled portion 8 will not be pressed completely and a portion bulging radially outwardly remains on the leading end potion of the curled portion 8. That is, the diametrically-largest section 8c is formed. In addition, the outer circumferential wall section 8e is formed in the portion pressed by the projection 31a of the outer tool 31, and consequently the diametrically-shrunk section 8d and the flexion section 8f are formed between the diametrically-largest section 8c and the outer circumferential wall section 8e.

[0053] Thus, according to the present invention, the curled portion 8 comprises: the portion extending from the leading end section 8b to the flexion section 8f via the diametrically-largest section 8c and the diametrically-shrunk section 8d while smoothly bulging radially outwardly; and the tapered or curved expanding portion as the outer circumferential wall section 8e extending downwardly from the flexion section 8f. According to the present invention, the curled portion 8 having such a specific configuration may be manufactured by less steps using the simple apparatus.

[0054] Thus, the apparatus shown in FIG. 8 is adapted to form the curled portion 8 by folding the neck portion 4. However, the present invention should not be limited to the apparatus shown in FIG. 8. For example, the curled portion 8 shown in FIG. 8 may also be formed by an apparatus in which forming portions of the inner tool and the outer tool are adapted to configurations of portions (or surfaces) of a forming object to be contacted thereto. Instead, the curled portion 8 shown in FIG. 8 may also be formed by conventional rollers in which forming portions thereof are adapted to configurations of portions (or surfaces) of a forming object to be contacted thereto.

REFERENCE SIGNS LIST

[0055] 1: bottle-shaped can; 2: trunk portion: 3; shoulder portion; 4: neck portion; 7: cap; 7a: top panel; 7b: skirt portion; 8: curled portion; 8a: top section; 8b: leading end section; 8c: diametrically-largest section; 8d: diametrically-shrunk section; 8e: outer circumferential wall section; 8f: flexion section; 8g: lower sealing end; 9: thread; 13: tapered portion; 25: diametrically-smaller cylindrical portion; 25a: bottom; 25b: leading end portion; 25c: folded portion; 30: inner tool; 30a: shaft portion; 30b: annular flat portion; 31: outer tool; 31a: projection; C: clearance ; Lc: center axis.