Receptacles – End wall structure – One-piece side and end wall
Reexamination Certificate
2000-06-08
2001-10-02
Tolan, Ed (Department: 3725)
Receptacles
End wall structure
One-piece side and end wall
C220S608000, C220S623000
Reexamination Certificate
active
06296139
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is related to and claims priority under 35 U.S.C. § 119 to Japanese Patent Application No. HEI 11-332045, filed on Nov. 22, 1999, entitled “CAN MANUFACTURING APPARATUS, CAN MANUFACTURING METHOD, AND CAN,” and incorporated by reference herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a can manufacturing apparatus, a can manufacturing method, and a can, wherein the apparatus for manufacturing the can has a dome section and an annular projection, the dome section being formed on a bottom of the can and is recessed inwardly of a body of the can, and the annular projection being formed around the peripheral edge of the dome section so as to project outwardly in a can axis direction.
2. Discussion of Background
Two-piece aluminum alloy cans composed of a cylindrical bottomed can body is well known. A can end is fixed to an opening in the can body. The can body of the two-piece can is made by, first, stamping and drawing an aluminum alloy blank sheet to form a cup member using a drawing apparatus. Then, the cup member is redrawn and ironed with a punch sleeve inserted therein, while the cup member is held. In this way, the peripheral edge of the bottom portion of the cup member is drawn, while it is clamped between the punch sleeve and a dome molding unit. The dome molding unit has a semi-spherical extreme end and is disposed in opposition to the punch sleeve so as to be coaxially therewith. Thus, a can body
101
, having the bottom shape shown in
FIG. 13
, is obtained.
The can bottom
103
of the can body
101
has a dome section
105
and an annular projection (rim)
107
formed thereon. The dome section
105
is spherically recessed inwardly of the can body
101
, and the annular projection (rim)
107
joins the peripheral edge of the dome section
105
and projects outwardly of the can body
101
in a direction of the can axis. The annular projection
107
acts as a leg, which is in contact with the ground, when the can body
101
stands upright. Thus, the standing stability and supporting strength of the can body
101
can be improved.
Today's trend toward reduced wall thickness of cans to save resources and costs has lead to various disadvantages due to the reduction of the strength of the cans. One disadvantages results from a phenomenon called bottom growth, wherein an annular projection
107
of a can bottom
103
is deformed outwardly in a radial direction, while projecting downwardly due to the action of internal pressure, after contents are packed into the can (see the double dot and dashed line of FIG.
14
). One of factors which causes bottom growth is the insufficient rigidity of an inner wall
107
a
, acting as the inner peripheral wall of the annular projection
107
. A first peripheral edge of the inner wall
107
a
is joined to the dome section
105
through a counter sink R-section
109
to form a concave surface. A second peripheral edge of the inner wall
107
a
is joined to a nose section
107
b
to form an extreme end of the annular projection
107
. When an internal pressure acts on the can bottom
103
, the thin inner wall
107
a
is stressed in the circumferential direction and in the direction of the can axis. In particular, when the stress (elongation) in the direction of the can axis is increased, the annular projection
107
is deformed downwardly and radially outwardly.
When bottom growth occurs, the total height of a can is increased. Thus, problems may arise due to the can's increased height, such as the cans may become caught on a conveyor as the can is transported to be packaged or the cans may be difficult to package.
Another problem is that as the thickness of the can is reduced, the falling strength of a can bottom becomes insufficient. In other words, when a can falls, the peripheral portion of the dome section
55
of the can bottom
53
, which is a particularly fragile portion when subjected to shock caused by a can's fall, swells and may be broken in the worst-case scenario.
In view of the above-described disadvantages, an object of the present invention is to provide a can, a can manufacturing apparatus and a can manufacturing method, wherein the apparatus and method are for manufacturing a can having a reduced wall thickness, particularly in the can bottom, yet retaining sufficient can strength so as to prevent deformation of the can bottom and suppress bottom growth.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, the can manufacturing apparatus is for forming a can body having a dome section and an annular projection, wherein the dome section is formed on the can bottom and is recessed inwardly, and wherein the annular projection is formed around the peripheral edge of the dome section and projects outwardly in the direction of the can axis. The annular projection has an inner peripheral wall with a plurality of inner recesses in a circumferential direction. The plurality of recesses are recessed inwardly. The can manufacturing apparatus includes: an apparatus main body; a can body support means, disposed on the apparatus main body for supporting the can body; and a can bottom processing means, disposed on the apparatus main body. The can bottom processing means moves relatively in the direction of the can axis with respect to the can bottom. The can processing means includes: a plurality of punch pawls disposed in the circumferential direction, wherein each punch pawl has an extreme end section, movable in a radial direction and projecting toward the can body support means; a punch pawl moving means for moving the extreme ends outwardly in the radial direction; and a dome support means, which abuts the dome section from the inside of the punch pawls, in the radial direction thereof, for supporting the dome section.
In the can manufacturing apparatus, the can bottom processing means expands the extreme ends of the punch pawls by moving relatively, with respect to the can bottom, in the direction of the can axis. In this way, the inner recesses are formed on the inner peripheral wall of the annual projection of the can bottom. Since the inner recesses can be formed while pressing the dome section with the dome support member, the dome section hangs down when the inner recesses are formed.
It is preferable that the can manufacturing apparatus, according to the first aspect of the present invention, is arranged such that the can and the can body support means are movable in the direction of the can axis, with respect to the apparatus main body. The can bottom forming means is unmovable in the direction of the can axis, with respect to the apparatus main body.
The can manufacturing apparatus has a relatively simple arrangement as a whole, even though the can bottom processing means has a relatively complex arrangement and is unmovable with respect to the apparatus main body and the can body support means. This is in part because the can body support means has a relatively simple arrangement and is movable with respect to the apparatus main body.
Preferably, the can manufacturing apparatus, according to the first aspect of the present invention, includes: an outer peripheral wall forming means for forming the outer peripheral wall of the annular projection.
In the can manufacturing apparatus, the inner and outer peripheral walls of the annular projection can be substantially simultaneously formed during the same step.
According to a second aspect of the present invention. A can manufacturing method for manufacturing a can having a dome section and an annular projection. The dome section is formed on the bottom of the can and is recessed inwardly of the body of the can. The annular projection is formed around the peripheral edge of the dome section and projects outwardly in the direction of the can axis. A plurality of inner recesses are formed on the inner peripheral wall of the annular projection in a circumferential direction so as to be recessed inwardly of the can body. The can manufacturin
Hanafusa Tatsuya
Hosoi Masahiro
Ikeda Aki
Mitsubishi Materials Corporation
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tolan Ed
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