Bottom holding structure for can forming machine

Abstract

This invention provides a bottom holding structure for a can forming machine that can stably hold the bottom of the can even when spin-flow necking is applied to the opening of a thin-walled can, thereby suppressing can wobbling and maintaining good processing accuracy. [Solution] The can bottom 102 is equipped with an elastically deformable annular elastic part 13 that contacts the outer circumference of the can bottom 102, a suction means 12 that sucks air from the can bottom 102 side in the can axis direction, and an outer support part 14 that faces the outer peripheral wall surface 107 of the can bottom 102 with a gap between them, extending radially outward from the nose part 105 that protrudes the most toward the can bottom 102 side in the can axis direction toward the opening side in the can axis direction. The can bottom 102 is pressed against the elastic part 13 by the suction force of the suction means 12, and when the elastic part 13 is elastically deformed, the outer support part 14 is able to contact the outer peripheral wall surface 107.

Description

Technical Field

[0001] The present invention relates to a bottom holding structure of a can forming device.

Background Art

[0002] Conventionally, a two-piece can including a bottomed cylindrical can having a can body (wall) and a can bottom (bottom), and a disc-shaped can lid wound and tightened around an opening of the can is known. Specifically, the can is a DI can, and "DI" is an abbreviation of Drawing&Ironing. Further, the can bottom has a dome portion recessed toward the opening side (upper side) in the can axis direction, and an annular convex portion (rim portion) connected to the outer peripheral portion of the dome portion and protruding toward the can bottom side (lower side) in the can axis direction. The protruding end on the can bottom side in the can axis direction of the annular convex portion is a nose portion.

[0003] Such a can (DI can) is formed into a bottomed cylindrical shape by subjecting a disc-shaped blank punched from a plate material such as an aluminum alloy to a capping process (drawing process) and a DI process (drawing and ironing process). In the can that has undergone the DI process, a neck portion and a flange portion are formed at the opening of the can body in a can forming device (necking processing device). Thereafter, the can is filled with a content such as a beverage, and the outer peripheral portion of the can lid is wound and tightened around the flange portion, whereby the two-piece can is sealed.

[0004] For example, in Patent Documents 1 and 2, the above-described neck portion and flange portion are formed by subjecting the opening of the can body to spin flow necking (SFN) processing. In the spin flow necking processing, with a bottom holding structure (base pad) sucking and holding the can bottom by air suction (vacuum adsorption), the can is rotated around the can axis, and the opening of the can body is sandwiched between a plurality of rolls (inner roll, slide roll, and outer roll) from the radial inner side and the outer side, and forming processing is performed.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] In recent years, this type of can has been made thinner to reduce the amount of material used, which has made it easier for defects such as bottom growth and buckling to occur (for bottom growth and buckling, see, for example, Japanese Patent Publication No. 2017-136605). To suppress the occurrence of such defects, measures have been taken to increase the strength of the can bottom by reducing the contact diameter of the can bottom. The above contact diameter refers to the diameter of the nose portion (contact portion) of the annular protrusion.

[0007] However, if the contact diameter of the can bottom becomes small, the can becomes more prone to wobbling, and the can bottom's holding state by the bottom holding structure becomes unstable. When the can bottom's holding state becomes unstable, it becomes difficult to maintain good molding accuracy (dimensional accuracy) during SFN processing. In particular, with SFN processing, the above problem is likely to occur because a force that pushes radially on the can opening is easily applied during processing.

[0008] The present invention aims to provide a bottom holding structure for a can forming apparatus that can stably hold the bottom of a can even when spin-flow necking is applied to the opening of a thin-walled can, thereby suppressing can wobbling and maintaining good processing accuracy. [Means for solving the problem]

[0009] To solve the above problems, the present invention provides the following means.

[0010] [Aspect 1 of the present invention] A bottom holding structure for a can forming apparatus that performs spin-flow necking on the opening of a bottomed cylindrical can having a can body and a can bottom, and which is provided in the can forming apparatus to hold the can bottom by suction, comprising: an elastically deformable annular elastic part that contacts the outer circumference of the can bottom; a suction means for sucking air from the can bottom side in the can axis direction to hold the can bottom; and an outer support part that faces the outer peripheral wall surface of the can bottom with a gap between it and the outer peripheral wall surface that extends radially outward from the nose part that protrudes the most toward the can bottom side in the can axis direction toward the opening side in the can axis direction, wherein the can bottom is pressed against the elastic part by the suction force of the suction means, and the outer support part is able to contact the outer peripheral wall surface when the elastic part is elastically deformed.

[0011] In the bottom holding structure of the can forming apparatus of the present invention, when a can that has been made thinner from the viewpoint of reducing the amount of material used and measures have been taken to increase the strength of the can bottom by reducing the contact diameter of the can bottom is subjected to spin flow necking, the following effects can be obtained.

[0012] In other words, the suction means sucks air from the bottom of the can, pressing the bottom of the can against the annular elastic part, and while the elastic part elastically deforms and the bottom of the can is held in place by suction, the outer support part is made capable of contacting the outer circumferential wall surface of the bottom of the can.

[0013] Therefore, when the bottom holding structure holds the bottom of the can by suction, if the can axis of the can and the central axis of the bottom holding structure are misaligned (eccentric), the outer support part will come into contact with the outer peripheral wall surface. This causes the can to move radially, and the can axis of the can is aligned so that it is coaxial with the central axis of the bottom holding structure. In other words, when the can is held (transferred) to the bottom holding structure, the can axis of the can is aligned so that it is coaxial with the central axis of the bottom holding structure, thus ensuring the accuracy of the can's holding position.

[0014] Furthermore, during spin-flow necking, a force acts to push the opening of the can body radially, and when the can attempts to move radially, the outer support part comes into contact with the outer circumferential wall surface. This restricts the radial movement of the can, and ensures that the can axis and the central axis of the bottom holding structure are properly aligned coaxially. In addition, the contact of the outer support part with the outer circumferential wall surface stabilizes the holding state of the can bottom by the bottom holding structure, and the orientation of the can is also stabilized. As a result, the molding accuracy (dimensional accuracy) during SFN processing is consistently improved.

[0015] As described above, according to the present invention, even when spin-flow necking is applied to the opening of a can with a thinned wall, the bottom of the can can be held stably, wobbling of the can can be suppressed, and processing accuracy can be maintained well. As a result, the quality of the manufactured cans (product cans) can be stably improved.

[0016] [Aspect 2 of the present invention] The bottom holding structure for a can forming apparatus according to Embodiment 1, wherein the outer circumference of the dome portion recessed toward the opening in the can axial direction of the can bottom connects to the nose portion, and the inner circumferential wall surface facing radially inward is further provided with an inner support portion facing it with a gap between them.

[0017] In this case, when the bottom holding structure holds the bottom of the can by suction, if the can axis of the can and the central axis of the bottom holding structure are misaligned (eccentric), the inner support part will come into contact with the inner circumferential wall surface of the can bottom. This causes the can to move radially, and the can axis of the can is aligned so that it is coaxial with the central axis of the bottom holding structure. In other words, when the can is held (transferred) to the bottom holding structure, the can axis of the can is aligned so that it is coaxial with the central axis of the bottom holding structure, thus ensuring the accuracy of the can's holding position.

[0018] Furthermore, during spin-flow necking, a force acts to push the opening of the can body radially, and when the can attempts to move radially, the inner support part comes into contact with the inner circumferential wall surface. This restricts the radial movement of the can, and ensures that the can axis and the central axis of the bottom holding structure are well aligned coaxially. In addition, the contact of the inner support part with the inner circumferential wall surface stabilizes the holding state of the can bottom by the bottom holding structure, and the orientation of the can is also stabilized. As a result, the molding accuracy (dimensional accuracy) during SFN processing is consistently improved.

[0019] [Aspect 3 of the present invention] The bottom holding structure for a can forming apparatus according to embodiment 1 or 2, wherein the elastic portion has a cylindrical portion extending in the can axis direction and a tapered cylindrical portion connected to the end of the cylindrical portion on the opening side in the can axis direction, which widens in diameter toward the opening side in the can axis direction and contacts the outer circumference of the can bottom, and the outer support portion is arranged radially inward of the cylindrical portion and the tapered cylindrical portion and has a support surface that can contact the outer circumference wall surface, and at least a part of the support surface protrudes toward the opening side in the can axis direction than the cylindrical portion.

[0020] In this case, at least a portion of the support surface of the outer support is located radially inward of the cylindrical and tapered sections of the elastic part, and protrudes further toward the opening in the can axis direction than the cylindrical section. This makes it easier for the support surface to contact the outer wall surface. The function (effect) of the outer support described above is performed more stably.

[0021] [Aspect 4 of the present invention] The bottom holding structure for a can forming apparatus according to any one of embodiments 1 to 3, wherein the outer peripheral wall surface has a concave curved surface to be supported, the outer support portion has a convex curved surface to be in contact with the surface to be supported, and in a longitudinal cross-sectional view along the can axis, the radius of curvature of the convex curve formed by the support surface is smaller than the radius of curvature of the concave curve formed by the surface to be supported.

[0022] In this case, the supporting surface of the outer supporting portion is stably brought into contact with the supported surface of the outer peripheral wall surface. As a result, the supported surface is stably supported by the supporting surface. Therefore, the functions (effects) of the outer supporting portion described above are more stably achieved.

Effects of the Invention

[0023] According to the above aspect of the present invention, even when spin flow necking is performed on the opening of a can with a reduced wall thickness, a bottom holding structure of a can molding apparatus is provided that can stably hold the can bottom, suppress the wobbling of the can, and maintain good processing accuracy.

Brief Description of the Drawings

[0024] [Figure 1] FIG. 1 is a cross-sectional view (vertical cross-sectional view) showing the bottom holding structure of the can molding apparatus of the present embodiment.

Modes for Carrying Out the Invention

[0025] The bottom holding structure 10 of the can molding apparatus 1 according to an embodiment of the present invention will be described with reference to FIG. 1.

[0026] This can molding apparatus 1 is an apparatus for forming a neck portion and a flange portion (not shown) by performing spin flow necking (SFN) on an opening (not shown) of a bottomed cylindrical can 100 having a can body 101 and a can bottom 102. In the SFN process (SFN step), at least the neck portion may be formed, and the flange portion may be formed by a separate process (separate step). The can molding apparatus 1 of the present embodiment may be alternatively referred to as a necking apparatus or the like. The bottom holding structure 10 is provided in the can molding apparatus 1 and sucks and holds the can bottom 102 by air suction (vacuum suction).

[0027] Specifically, the can 100 is, for example, a DI can used for a two-piece can. A two-piece can is a can (wound can) composed of two members in which a disc-shaped can lid (not shown) is wound and tightened at the opening of a bottomed cylindrical can 100. In this can forming apparatus 1, after the neck portion and flange portion are formed at the opening of the can body 101, the can 100 is filled with contents such as a beverage, and the outer circumference of the can lid is wrapped around the flange portion to seal the two-piece can.

[0028] As shown in Figure 1, the can body 101 of the can 100 is cylindrical with respect to the can axis C, which is the central axis of the can 100. The can bottom 102 is roughly disc-shaped, extending in a direction perpendicular to the can axis C.

[0029] In this embodiment, the direction in which the can shaft C extends, that is, the direction parallel to the can shaft C, is called the can axis direction. The can bottom 102 is connected to the end of the can body 101 opposite to the opening in the can axis direction. Of the can axis directions, the direction from the can bottom 102 toward the opening of the can body 101 is called the opening side, and the direction from the opening of the can body 101 toward the can bottom 102 is called the can bottom 102 side.

[0030] Specifically, in Figure 1, the can axis direction corresponds to the Z axis direction, the opening side in the can axis direction corresponds to the +Z side, and the can bottom 102 side in the can axis direction corresponds to the -Z side. The can axis direction can also be rephrased as the vertical direction. In this case, the opening side in the can axis direction corresponds to the upper side, and the can bottom 102 side in the can axis direction corresponds to the lower side.

[0031] Furthermore, the direction perpendicular to the can shaft C is called the radial direction. Within the radial direction, the direction approaching the can shaft C is called the radially inward direction, and the direction moving away from the can shaft C is called the radially outward direction. Furthermore, the direction in which the flow of energy rotates around the can shaft C is called the circumferential direction.

[0032] The bottom holding structure 10 is a substantially cylindrical structure centered on a central axis O. The central axis O corresponds to the axis of rotation by which the bottom holding structure 10 rotates the can 100 during SFN processing. From the viewpoint of ensuring molding accuracy, it is ideal that during SFN processing, the opening of the can body 101 is molded with the central axis O of the bottom holding structure 10 and the can axis C of the can 100 arranged coaxially, as shown in Figure 1.

[0033] Although not specifically shown in the figures, the can forming apparatus 1 is equipped with multiple rolls that clamp the opening of the can body 101 from the radially inner and radially outer sides. As the multiple rolls, for example, internal rolls, slide rolls, and external rolls described in the above-mentioned Patent Documents 1 and 2 can be used. In the direction in which the central axis O of the bottom holding structure 10 extends (hereinafter sometimes referred to as the axial direction), the bottom holding structure 10 and the plurality of rolls are positioned at different locations from each other.

[0034] In this embodiment, the can axial direction corresponds to the axial direction in which the central axis O extends. The opening side (+Z side) in the can axial direction corresponds to the direction from the bottom holding structure 10 toward the plurality of rolls. For this reason, the opening side in the can axial direction may be rephrased as the roll side in the axial direction. The can bottom 102 side (-Z side) in the can axial direction corresponds to the direction from the plurality of rolls toward the bottom holding structure 10. For this reason, the can bottom 102 side in the can axial direction may be rephrased as the bottom side in the axial direction.

[0035] Furthermore, the direction perpendicular to the central axis O corresponds to the radial direction described above. The direction approaching the central axis O corresponds to the radially inward direction described above, and the direction moving away from the central axis O corresponds to the radially outward direction described above. Furthermore, the direction of rotation around the central axis O corresponds to the circumferential direction described above.

[0036] Let's explain the composition of Can 100 in more detail. A neck portion and a flange portion (not shown) are formed at the opening of the can body 101 by the multiple rolls of the can forming apparatus 1. The neck portion is formed with a decreasing diameter as it approaches the opening in the can axis direction. The flange portion is positioned closer to the opening in the can axis direction than the neck portion and is formed with a increasing diameter as it approaches the opening in the can axis direction.

[0037] The can bottom 102 comprises a dome portion 103 that is recessed toward the opening side (+Z side) in the can axis direction, and an annular projection (rim portion) 104 connected to the outer circumference of the dome portion 103 and projecting toward the can bottom 102 side (-Z side) in the can axis direction. The annular projection 104 forms a circular ring with the can axis C as the center. The outer circumference of the annular projection 104 is connected to the end (lower end) of the can body 101 on the can bottom 102 side in the can axis direction.

[0038] The portion of the can bottom 102 that protrudes most in the can axial direction is designated as the nose portion (contact portion) 105. The nose portion 105 is located at the tip of the annular projection 104 on the can bottom 102 side in the can axial direction. The nose portion 105 contacts the upper surface of a stand (not shown) when the can 100 is in an upright position with the opening of the can body 101 facing upward in the vertical direction.

[0039] The annular projection 104 has a nose portion 105 that forms a circular ring shape centered on the can axis C, an inner circumferential wall surface 106 that connects the outer circumference of the dome portion 103 and the nose portion 105 and faces radially inward, and an outer circumferential wall surface 107 that extends radially outward from the nose portion 105 toward the opening side in the can axis direction.

[0040] The inner circumferential wall surface 106 has a substantially cylindrical shape centered on the can axis C and extends in the direction of the can axis. As shown in Figure 1, in a longitudinal cross-sectional view along the can axis C, the portion of the inner circumferential wall surface 106 that connects to the outer circumference of the dome portion 103 (upper end) has a concave curve shape. Also in this longitudinal cross-sectional view, the portion of the inner circumferential wall surface 106 that connects to the nose portion 105 (lower end) has a convex curve shape. In this embodiment, in this longitudinal cross-sectional view, the intermediate portion of the inner circumferential wall surface 106 located between the upper end and the lower end has a linear shape that extends substantially in the direction of the can axis. Note that the inner circumferential wall surface 106 may be referred to as the countersink portion, etc.

[0041] The outer periphery wall surface 107 has a substantially tapered shape centered on the can axis C, and its diameter widens towards the opening side in the can axis direction. In the vertical cross-sectional view shown in Figure 1, the portion of the outer periphery wall surface 107 that connects to the nose portion 105 (lower end) has a convex curve shape. Also in this vertical cross-sectional view, the portion of the outer periphery wall surface 107 that connects to the end of the can body 101 on the can bottom 102 side in the can axis direction (upper end) has a convex curve shape. Also in this vertical cross-sectional view, the intermediate portion of the outer periphery wall surface 107 located between the upper and lower ends has a concave curve shape. Note that the outer periphery wall surface 107 may also be referred to as the chime portion or heel portion, etc.

[0042] Furthermore, the outer periphery wall surface 107 has a concave curved support surface 107a. The support surface 107a is located in the aforementioned intermediate portion of the outer periphery wall surface 107. Therefore, in the vertical cross-sectional view shown in Figure 1, the support surface 107a has a concave curved shape.

[0043] Here, the shape of the can bottom 202 shown by the dashed line in Figure 1 represents the can bottom shape of the conventional can 200. With the shape of the can bottom 202 of the conventional can 200, when the can wall is made thinner, there is a risk of problems such as bottom growth and buckling occurring. For this reason, in the can 100 of this embodiment, in order to increase the strength of the can bottom 102, the diameter dimension of the dome portion 103 (outer diameter dimension) and the diameter dimension of the nose portion 105 (ground diameter) are made smaller than those of the conventional can 200.

[0044] Next, the bottom holding structure 10 of the can forming apparatus 1 will be described in detail. Multiple bottom holding structures 10 are provided at intervals from each other on a turret or the like (not shown) of the can forming apparatus 1.

[0045] The bottom holding structure 10 comprises a multi-stage cylindrical base member 11 centered on a central axis O, a suction means 12 that draws air from the can bottom 102 side (bottom side) in the can axial direction through an air passage provided inside the base member 11, an elastically deformable annular elastic part 13 that contacts the outer circumference of the can bottom 102, an annular outer support part 14 that faces the outer peripheral wall surface 107 of the can bottom 102 with a gap between them, an annular nose support part 15 that contacts the nose part 105 from the can bottom 102 side in the can axial direction, and an annular inner support part 16 that faces the inner peripheral wall surface 106 of the can bottom 102 with a gap between them.

[0046] The base member 11 has a cylindrical base 11a extending in the axial direction of the central axis O, and a cylindrical base tube portion 11b connected to the upper end of the base 11a and protruding upward (towards the +Z side) from the upper end of the base 11a. The outer periphery of the upper surface of the base 11a is located below (towards the -Z side) the rest of the upper surface (the part located radially inward from the outer periphery). The base cylinder 11b extends upward from the outer periphery of the upper surface of the base 11a. The inner diameter of the base cylinder 11b is larger than the inner diameter of the base 11a.

[0047] The suction means 12 is, for example, an intake pump such as a vacuum pump. The suction means 12 communicates with the air passage in the base member 11 via a piping member (not shown) connected to the base 11a. This air passage also opens toward the bottom 102 of the can 100 held by the bottom holding structure 10.

[0048] The elastic portion 13 is annular in shape with a central axis O, and in this embodiment, it is specifically roughly cylindrical. The elastic portion 13 is made of elastically deformable rubber or the like. The elastic portion 13 is detachably fixed to the upper end of the base member 11.

[0049] The elastic portion 13 has a cylindrical portion 13a, a tapered cylindrical portion 13b, and a bottom wall portion 13c. The cylindrical portion 13a, the tapered cylindrical portion 13b, and the bottom wall portion 13c are integrally formed from a single member.

[0050] The cylindrical portion 13a extends in the direction of the can axis (corresponding to the direction of the central axis O). The cylindrical portion 13a is located on the opening side (upper side) of the base 11a in the direction of the can axis and is positioned radially inward of the base cylindrical portion 11b. In this embodiment, a gap is provided between the outer circumferential surface of the cylindrical portion 13a and the inner circumferential surface of the base cylindrical portion 11b.

[0051] The tapered cylindrical portion 13b is connected to the end (upper end) of the cylindrical portion 13a on the opening side in the can axis direction, and its diameter widens towards the opening side (upper side) in the can axis direction. The tapered cylindrical portion 13b contacts the outer circumference of the can bottom 102. Specifically, the upper end of the inner circumferential surface of the tapered cylindrical portion 13b contacts the upper end of the outer circumferential wall surface 107 of the can bottom 102 over its entire circumference. When the can bottom 102 is sucked with air by the suction means 12, the tapered cylindrical portion 13b and the outer circumferential wall surface 107 come into close contact over their entire circumference.

[0052] The upper end of the tapered cylinder portion 13b is located on the opening side (upper side) in the can axis direction compared to the base cylinder portion 11b. The upper end of the tapered cylinder portion 13b overlaps with the base cylinder portion 11b when viewed from the can axis direction. The upper end of the tapered cylinder portion 13b is located radially outward and upward among the components of the elastic portion 13. A gap is provided between the tapered cylinder portion 13b and the base cylinder portion 11b in the can axis direction. Therefore, the tapered cylinder portion 13b can be elastically deformed toward the base cylinder portion 11b (i.e., downward).

[0053] Furthermore, the wall thickness of the tapered cylindrical portion 13b is thinner than the wall thicknesses of the cylindrical portion 13a and the bottom wall portion 13c. The tapered cylindrical portion 13b is the most elastically deformable component of the elastic portion 13.

[0054] The bottom wall portion 13c is an annular plate shape centered on the can axis C (central axis O) and extends in a direction perpendicular to the can axis C. The outer circumference of the bottom wall portion 13c is connected to the end (lower end) of the cylindrical portion 13a on the can bottom 102 side in the can axis direction. The bottom wall portion 13c is positioned radially inward of the base cylindrical portion 11b. The lower surface of the bottom wall portion 13c is in contact with the outer circumference of the upper surface of the base 11a. The wall thickness of the bottom wall portion 13c is the thickest among the components of the elastic portion 13.

[0055] The outer support portion 14 is annular in shape with respect to the central axis O, and in this embodiment, it is specifically substantially cylindrical. The outer support portion 14 is made of metal, such as steel. The outer support portion 14 is located within the elastic portion 13. The outer support portion 14 has a peripheral wall 14a, a support surface 14b, and a projection 14c.

[0056] The peripheral wall 14a is cylindrical in shape with respect to the can axis C (central axis O) and extends in the direction of the can axis (the direction of the central axis O). The peripheral wall 14a is located radially inward of the cylindrical portion 13a and is positioned on the opening side (upper side) of the bottom wall portion 13c in the direction of the can axis. Specifically, the outer circumferential surface of the peripheral wall 14a is in contact with the inner circumferential surface of the cylindrical portion 13a, and the lower end surface of the peripheral wall 14a is in contact with the upper surface of the bottom wall portion 13c.

[0057] The support surface 14b is positioned at the upper end opening of the peripheral wall 14a, extending around the entire circumference. The support surface 14b forms a circular annular shape centered on the can shaft C (central axis O). Specifically, the support surface 14b is formed from the inner circumferential surface to the upper end surface of the peripheral wall 14a, and has a curved shape that is convex radially inward and upward. The support surface 14b is also positioned radially inward of the cylindrical portion 13a and the tapered cylindrical portion 13b. The support surface 14b faces the supported surface 107a of the outer peripheral wall surface 107 with a gap between them.

[0058] Then, the can bottom 102 is pressed against the elastic part 13 by the suction force of the suction means 12, and in the state in which the elastic part 13 is elastically deformed, the outer support part 14 is made capable of contacting the outer peripheral wall surface 107 of the can bottom 102.

[0059] In more detail, when the bottom 102 of the can is attracted to the elastic part 13 by the air suction (vacuum adsorption) of the suction means 12, if the can axis C of the can 100 is coaxially positioned with respect to the central axis O of the bottom holding structure 10, a gap is provided between the outer support part 14 and the outer peripheral wall surface 107, so the outer support part 14 and the outer peripheral wall surface 107 do not come into contact. On the other hand, if the can axis C of the can 100 is offset radially by a predetermined dimension or more with respect to the central axis O of the bottom holding structure 10 (eccentric state), the outer support portion 14 and the outer peripheral wall surface 107 can come into contact. In this case, the outer support portion 14 contacts the outer peripheral wall surface 107 from the radially outer side.

[0060] Specifically, in this embodiment, the convex curved support surface 14b of the outer support portion 14 is capable of contacting the concave curved supported surface 107a of the outer peripheral wall surface 107 from the radially outer side. Furthermore, as shown in Figure 1, in a longitudinal cross-sectional view along the can shaft C, the radius of curvature of the convex curve formed by the support surface 14b is smaller than the radius of curvature of the concave curve formed by the supported surface 107a. Therefore, in this longitudinal cross-sectional view, the support surface 14b contacts the supported surface 107a at a single point (however, this contact is actually a line contact extending in the circumferential direction).

[0061] Furthermore, at least a portion of the support surface 14b protrudes further than the cylindrical portion 13a toward the opening side (upward) in the can axis direction. In this embodiment, the upper end of the support surface 14b protrudes upward above the cylindrical portion 13a. Also, the upper end of the support surface 14b overlaps with the lower end of the tapered cylindrical portion 13b when viewed from the radial direction.

[0062] The projection 14c is connected to the lower end of the peripheral wall 14a and protrudes radially inward from this lower end. The outer support portion 14 has multiple projections 14c. The multiple projections 14c are spaced apart from each other in the circumferential direction. In this embodiment, three projections 14c are provided at equal pitches in the circumferential direction. Each projection 14c is plate-shaped, extending in a direction perpendicular to the can shaft C (central axis O), and specifically, it is an arc-shaped plate extending in the circumferential direction. The lower surface of each projection 14c is in contact with the upper surface of the base 11a.

[0063] The nose support portion 15 is an annular plate shape that extends in a direction perpendicular to the can axis C (central axis O). The nose support portion 15 is positioned radially inward of the peripheral wall 14a. The lower surface of the nose support portion 15 contacts the upper surface of the base 11a and the upper surfaces of the multiple projections 14c. The upper surface of the nose support portion 15 is located below the support surface 14b. The nose portion 105 of the can bottom 102 contacts the outer circumference of the upper surface of the nose support portion 15.

[0064] The inner support portion 16 is an annular plate shape that expands in a direction perpendicular to the can shaft C (central axis O). The outer diameter of the inner support portion 16 is smaller than the outer diameter of the nose support portion 15. The inner support portion 16 is placed on the upper surface of the nose support portion 15. The inner support portion 16 is fixed to the base 11a together with the nose support portion 15 by fastening members such as multiple bolts.

[0065] The outer circumferential surface 16a of the inner support portion 16 has a tapered shape, decreasing in diameter towards the opening side (upper side) in the can axial direction. The outer circumferential surface 16a is a circular annular shape centered on the central axis O. The outer circumferential surface 16a faces the inner circumferential wall surface 106 of the can bottom 102 with a gap between them. The upper surface of the inner support portion 16 is positioned below the dome portion 103.

[0066] The suction force of the suction means 12 presses the bottom of the can 102 against the elastic part 13, and in the state where the elastic part 13 is elastically deformed, the inner support part 16 is able to contact the inner circumferential wall surface 106 of the bottom of the can 102.

[0067] In more detail, when the bottom 102 of the can is attracted to the elastic part 13 by the air suction (vacuum adsorption) of the suction means 12, if the can axis C of the can 100 is coaxially positioned with respect to the central axis O of the bottom holding structure 10, a gap is provided between the inner support part 16 and the inner circumferential wall surface 106, so the inner support part 16 and the inner circumferential wall surface 106 do not come into contact. On the other hand, if the can axis C of the can 100 is offset radially by a predetermined dimension or more with respect to the central axis O of the bottom holding structure 10 (eccentric state), the inner support portion 16 and the inner circumferential wall surface 106 can come into contact. In this case, the inner support portion 16 comes into contact with the inner circumferential wall surface 106 from the radially inner side. Specifically, in this embodiment, the outer circumferential surface 16a of the inner support portion 16 is made capable of coming into contact with the lower end of the inner circumferential wall surface 106 from the radially inner side.

[0068] In the bottom holding structure 10 of the can forming apparatus 1 of this embodiment described above, when a can 100 that has been made thinner from the viewpoint of reducing the amount of material used and measures have been taken to increase the strength of the can bottom 102 by reducing the contact diameter of the can bottom 102 is subjected to spin flow necking, the following effects can be obtained.

[0069] In other words, the suction means 12 sucks air from the bottom of the can 102, pressing the bottom of the can 102 against the annular elastic part 13, and while the elastic part 13 elastically deforms and the bottom of the can 102 is held in place by suction, the outer support part 14 is made able to contact the outer peripheral wall surface 107 of the bottom of the can 102.

[0070] Therefore, when the bottom holding structure 10 holds the bottom 102 of the can by suction, if the can axis C of the can 100 and the central axis O of the bottom holding structure 10 are misaligned (eccentric), the outer support portion 14 will come into contact with the outer peripheral wall surface 107, causing the can 100 to move radially and be aligned so that the can axis C of the can 100 becomes coaxial with the central axis O of the bottom holding structure 10. In other words, when the can 100 is held (transferred) to the bottom holding structure 10, the can axis C of the can 100 is aligned to become coaxial with the central axis O of the bottom holding structure 10, thereby ensuring accuracy in the holding position of the can 100.

[0071] Furthermore, during spin-flow necking, a force acts to push the opening of the can body 101 radially, and when the can 100 attempts to move radially, the outer support portion 14 contacts the outer peripheral wall surface 107. This restricts the radial movement of the can 100, and the can axis C of the can 100 and the central axis O of the bottom holding structure 10 are well aligned coaxially. In addition, the contact of the outer support portion 14 with the outer peripheral wall surface 107 stabilizes the holding state of the can bottom 102 by the bottom holding structure 10, and the posture of the can 100 is also stabilized. As a result, the molding accuracy (dimensional accuracy) during SFN processing is stably improved.

[0072] As described above, according to this embodiment, even when spin-flow necking is applied to the opening of a thin-walled can 100, the can bottom 102 can be held stably, wobbling of the can 100 can be suppressed and processing accuracy can be maintained well. As a result, the quality of the manufactured cans (product cans) can be stably improved.

[0073] Furthermore, the bottom holding structure 10 of the can forming apparatus 1 of this embodiment connects the outer circumference of the dome portion 103, which is recessed toward the opening in the can axial direction, and the nose portion 105 of the can bottom 102, and further includes an inner support portion 16 facing the inner circumferential wall surface 106, which faces radially inward, with a gap between them.

[0074] In this case, when the bottom holding structure 10 holds the can bottom 102 by suction, if the can axis C of the can 100 and the central axis O of the bottom holding structure 10 are misaligned (eccentric), the inner support portion 16 will come into contact with the inner circumferential wall surface 106 of the can bottom 102. This causes the can 100 to move radially, and the can axis C of the can 100 will be aligned with the central axis O of the bottom holding structure 10. In other words, when the can 100 is held (transferred) to the bottom holding structure 10, the can axis C of the can 100 is aligned with the central axis O of the bottom holding structure 10, thus ensuring accuracy in the holding position of the can 100.

[0075] Furthermore, during spin-flow necking, a force acts to push the opening of the can body 101 radially, and when the can 100 attempts to move radially, the inner support portion 16 contacts the inner circumferential wall surface 106. This restricts the radial movement of the can 100, and the can axis C of the can 100 and the central axis O of the bottom holding structure 10 are well aligned coaxially. In addition, the contact of the inner support portion 16 with the inner circumferential wall surface 106 stabilizes the holding state of the can bottom 102 by the bottom holding structure 10, and the posture of the can 100 is also stabilized. As a result, the molding accuracy (dimensional accuracy) during SFN processing is stably improved.

[0076] In this embodiment, the elastic portion 13 has a cylindrical portion 13a extending in the can axis direction, and a tapered cylindrical portion 13b connected to the end of the cylindrical portion 13a on the opening side in the can axis direction, which widens in diameter toward the opening side in the can axis direction and contacts the outer circumference of the can bottom 102. The outer support portion 14 is positioned radially inward of the cylindrical portion 13a and the tapered cylindrical portion 13b and has a support surface 14b that can contact the outer peripheral wall surface 107, with at least a portion of the support surface 14b protruding toward the opening side in the can axis direction more than the cylindrical portion 13a.

[0077] In this case, at least a portion of the support surface 14b of the outer support portion 14 is located radially inward of the cylindrical portion 13a and the tapered cylindrical portion 13b of the elastic portion 13, and protrudes further toward the opening in the can axis direction than the cylindrical portion 13a. This makes it easier for the support surface 14b to contact the outer peripheral wall surface 107. The function (effect) of the outer support portion 14 described above is performed more stably.

[0078] In this embodiment, the outer peripheral wall surface 107 has a concave curved surface to be supported 107a, and the outer support portion 14 has a convex curved support surface 14b that can contact the supported surface 107a. In a longitudinal cross-sectional view along the can shaft C, the radius of curvature of the convex curve formed by the support surface 14b is smaller than the radius of curvature of the concave curve formed by the supported surface 107a.

[0079] In this case, the support surface 14b of the outer support portion 14 is stably in contact with the supported surface 107a of the outer peripheral wall surface 107. As a result, the supported surface 107a is stably supported by the support surface 14b. Therefore, the function (effect) of the outer support portion 14 described above is more stably achieved.

[0080] It should be noted that the present invention is not limited to the embodiments described above, and modifications to the configuration, etc., are possible without departing from the spirit of the invention, as described below, for example.

[0081] In the above-described embodiment, an example was given in which the support surface 14b of the outer support portion 14 is formed in a convex curved shape, but the embodiment is not limited to this. Although not shown in particular, the support surface 14b may be formed in a straight line that extends radially outward towards the opening side (upper side) in the direction of the can axis when viewed in a longitudinal cross-section along the can axis C. In this case, the support surface 14b is formed in a tapered shape that widens in diameter towards the opening side in the direction of the can axis.

[0082] Furthermore, in the above-described embodiment, an example was given in which the outer peripheral surface 16a of the inner support portion 16 is tapered in diameter as it approaches the opening side (upper side) in the can axial direction, but the embodiment is not limited to this. Although not specifically shown, the outer peripheral surface 16a may be a convex curved surface that is convex radially outward and upward.

[0083] The present invention may be combined in any way that does not depart from the spirit of the invention, as described in the above embodiments and modifications, and the configurations may be added, omitted, substituted, or otherwise modified. Furthermore, the present invention is not limited by the above embodiments, but is limited only by the claims. [Industrial applicability]

[0084] According to the bottom holding structure of the can forming apparatus of the present invention, even when spin-flow necking is performed on the opening of a thin-walled can, the bottom of the can can be held stably, suppressing can wobbling and maintaining good processing accuracy. As a result, the quality of the manufactured cans (product cans) can be stably improved. Therefore, it has industrial applicability. [Explanation of symbols]

[0085] 1...Can forming apparatus, 10...Bottom holding structure, 12...Suction means, 13...Elastic part, 13a...Cylindrical part, 13b...Tapered cylinder part, 14...Outer support part, 14b...Support surface, 16...Inner support part, 100,200...Can, 101...Can body, 102,202...Can bottom, 103...Dome part, 105...Nose part, 106...Inner circumferential wall surface, 107...Outer circumferential wall surface, 107a...Supported surface, C...Can shaft

Claims

1. A bottom holding structure for a can forming apparatus that performs spin-flow necking on the opening of a bottomed cylindrical can having a can body and a can bottom, which is provided in the can forming apparatus and holds the can bottom by suction, An elastically deformable annular elastic portion that contacts the outer circumference of the bottom of the can, A suction means for drawing air from the bottom of the can in the direction of the can axis, The can bottom comprises an outer support portion that faces the outer peripheral wall surface extending radially outward from the nose portion that protrudes most towards the can bottom in the can axis direction, toward the opening in the can axis direction, with a gap between them. The bottom of the can is pressed against the elastic portion by the suction force of the suction means, and in a state where the elastic portion is elastically deformed, the outer support portion is made capable of contacting the outer peripheral wall surface. Bottom holding structure for a can forming machine.

2. The can bottom is provided with an inner support portion that is positioned opposite to the can axial opening, with a gap between them, connecting the outer circumference of the dome portion that is recessed toward the opening in the can axial direction and the nose portion, and facing radially inward on the inner circumferential wall surface. The bottom holding structure for a can molding apparatus according to claim 1.

3. The elastic portion is A cylindrical section extending in the direction of the can axis, It has a tapered cylindrical portion connected to the end of the cylindrical portion on the opening side in the can axis direction, which widens in diameter toward the opening side in the can axis direction, and which contacts the outer circumference of the can bottom, The outer support portion is positioned radially inward of the cylindrical portion and the tapered cylindrical portion, and has a support surface that can contact the outer peripheral wall surface. At least a portion of the support surface protrudes further toward the opening in the can axis direction than the cylindrical portion. The bottom holding structure for a can molding apparatus according to claim 1 or 2.

4. The outer peripheral wall surface has a concave curved surface to be supported, The outer support portion has a convex curved support surface that can contact the supported surface, In a longitudinal cross-sectional view along the can shaft, the radius of curvature of the convex curve formed by the support surface is smaller than the radius of curvature of the concave curve formed by the supported surface. The bottom holding structure for a can molding apparatus according to claim 1 or 2.

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