U.S. patent application number 10/834671 was filed with the patent office on 2004-10-14 for can end.
Invention is credited to Forrest, Randy G., Gopalaswamy, Rajesh, Turner, Timothy.
Application Number | 20040200838 10/834671 |
Document ID | / |
Family ID | 25460869 |
Filed Date | 2004-10-14 |
United States Patent
Application |
20040200838 |
Kind Code |
A1 |
Turner, Timothy ; et
al. |
October 14, 2004 |
Can end
Abstract
An end member for a container. The end member has a central
panel, a circumferential chuckwall, and a transition wall. The
central panel is centered about a longitudinal axis and has a
substantially planar peripheral edge. The curl defines an outer
perimeter of the end member. The circumferential chuckwall extends
downwardly from the curl to the transition wall. The transition
wall connects the chuckwall with the substantially planar
peripheral edge of the central panel. The transition wall has a
folded portion extending outwardly relative to the longitudinal
axis.
Inventors: |
Turner, Timothy;
(Pecatonica, IL) ; Gopalaswamy, Rajesh; (Lake
Zurich, IL) ; Forrest, Randy G.; (Park Ridge,
IL) |
Correspondence
Address: |
Peter M. Klobucher
Wallenstein Wagner & Rockey, Ltd.
311 South Wacker Drive, 53rd Floor
Chicago
IL
60606-6630
US
|
Family ID: |
25460869 |
Appl. No.: |
10/834671 |
Filed: |
April 29, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10834671 |
Apr 29, 2004 |
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09931497 |
Aug 16, 2001 |
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6772900 |
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Current U.S.
Class: |
220/269 ;
220/619 |
Current CPC
Class: |
B65D 2517/0082 20130101;
B65D 2517/0079 20130101; B65D 2517/0007 20130101; B65D 2517/0011
20130101; B65D 17/08 20130101; B65D 17/4012 20180101; B65D
2517/0061 20130101; B65D 2517/0076 20130101 |
Class at
Publication: |
220/269 ;
220/619 |
International
Class: |
B65D 017/34; B65D
008/04 |
Claims
We claim:
1. An easy open can end member comprising: a central panel centered
about a longitudinal axis having a peripheral edge and a tear panel
defined by fracturable score, the tear panel retained to the
central panel along a non-scored hinge region; a curl defining an
outer perimeter of the end member; a circumferential chuckwall
extending downwardly from the curl; and a transition wall
connecting the chuckwall with the peripheral edge of the central
panel, the transition wall comprising a fold having an annular
concave bend directing a portion of the fold outwardly relative to
the longitudinal axis, the portion of the fold including an upper
vertical extent located outwardly from the chuckwall.
2. The easy open can end member of claim 1 wherein the fold
comprises a first leg having first end directly connected to the
chuckwall and an opposing second end directly connected to the
annular concave bend.
3. The easy open can end member of claim 2 wherein the fold
comprises a second leg having a first end connect to the annular
concave bend and an opposing second connected to an annular convex
bend.
4. The easy open can end member of claim 3 wherein the upper
vertical extent is located along the annular convex bend.
5. The easy open can end member of claim 4 wherein the fold
comprises a third leg having a first end connected to the annular
convex bend and an opposing second end interconnected to the
central panel.
6. The easy open can end member of claim 5 wherein the fold has a
third bend joining the third leg to the central panel.
7. The easy open can end member of claim 6 wherein the third bend
has a radius of curvature substantially defined by a lower extent
of the annular concave bend.
8. The easy open can end member of claim 1 wherein the fold further
comprises a first end directly connected to the chuckwall and a
second end connected to the central panel, the first end located at
a greater vertical extent than the second end, and separated from
the second end by a first leg, a second leg, and a third leg.
9. The easy open can end member of claim 1 wherein the chuckwall
extends downwardly from the curl at an obtuse angle and the fold
has a thickness that is substantially less than a length of the
chuckwall.
10. The easy open can end member of claim 1 wherein the annular
concave bend engages the peripheral edge of the central panel.
11. The easy open can end member of claim 10 wherein the concave
annular bend includes an apex, the apex being in engagement with
the peripheral edge of the central panel.
12. An easy open can end member comprising: a central panel
centered about a longitudinal axis having a peripheral edge and a
tear panel defined by fracturable score, the tear panel retained to
the central panel along a non-scored hinge region; a curl defining
an outer perimeter of the end member; a circumferential chuckwall
extending downwardly from the curl; and a transition wall
connecting the chuckwall with the peripheral edge of the central
panel, the transition wall including a fold having a first end
directly connected to the chuckwall and a second end connected to
the central panel, the first end located at a greater vertical
extent than the second end, and separated from the second end by a
first leg, a second leg, and a third leg.
13. The easy open can member of claim 12 wherein the fold extends
outwardly relative to the longitudinal axis.
14. The easy open can member of claim 12 wherein the fold further
comprises an annular concave bend between the first leg and second
leg, the annular concave bend extending radially outwardly relative
to the longitudinal axis wherein the second leg extends outwardly
from the chuckwall.
15. The easy open can end member of claim 14 wherein the fold
further comprises an annular convex bend between the second leg and
the third leg, the annular convex extending inwardly realtive to
the longitudinal axis wherein the leg extends inwardly relative to
the longitudinal axis.
16. The easy open can end member of claim 15 wherein the fold
further comprises a third bend joining the third leg with the
central panel.
17. The easy open can end member of claim 16 wherein the third bend
has a radius of curvature substantially defined by a lower extent
of the annular concave bend.
18. The easy open can end member of claim 17 wherein the annular
concave bend is in engagement with the peripheral edge of the
central panel.
19. The easy open can end member of claim 18 wherein a portion of
the annular convex bend forms a highest vertical extent of the
fold.
20. An easy open can end member comprising: a central panel
centered about a longitudinal axis having a peripheral edge, a
public side and a product side; a curl defining an outer perimeter
of the end member; a circumferential chuckwall extending downwardly
from the curl; and a fold having a first end directly connected to
the chuckwall and a second end connected to the central panel, the
first end located at a greater vertical extent than the second end
and separated from the second end by a first leg, a second leg, and
a third leg, the fold further having an annular concave bend
located between the first leg and the second leg and directing the
second leg upwardly and outwardly relative to the longitudinal
axis.
Description
RELATED APPLICATION
[0001] This application is a continuation of co-pending U.S.
application Ser. No. 09/931,497, which was filed on Aug. 16, 2001,
and is now U.S. Pat. No. X,XXX,XXX.
TECHNICAL FIELD
[0002] The present invention relates to end closures for two-piece
beer and beverage metal containers having a non-detachable
operating panel. More specifically, the present invention relates
to a method of reducing the volume of metal in an end closure.
BACKGROUND OF THE INVENTION
[0003] Common easy open end closures for beer and beverage
containers have a central panel that has a frangible panel
(sometimes called a "tear panel," "opening panel," or "pour panel")
defined by a score formed on the outer surface, the "consumer
side," of the end closure. Popular "ecology" can ends are designed
to provide a way of opening the end by fracturing the scored metal
of the panel, while not allowing separation of any parts of the
end. For example, the most common such beverage container end has a
tear panel that is retained to the end by a non-scored hinge region
joining the tear panel to the reminder of the end, with a rivet to
attach a leverage tab provided for opening the tear panel. This
type of container end, typically called a "stay-on-tab" ("SOT") end
has a tear panel that is defined by an incomplete circular-shaped
score, with the non-scored segment serving as the retaining
fragment of metal at the hinge-line of the displacement of the tear
panel.
[0004] The container is typically a drawn and ironed metal can,
usually constructed from a thin sheet of aluminum or steel. End
closures for such containers are also typically constructed from a
cut-edge of thin sheet of aluminum or steel, formed into a blank
end, and manufactured into a finished end by a process often
referred to as end conversion. These ends are formed in the process
of first forming a cut-edge of thin metal, forming a blank end from
the cut-edge, and converting the blank into an end closure which
may be seamed onto a container. Although not presently a popular
alternative, such containers and/or ends may be constructed of
plastic material, with similar construction of non-detachable parts
provided for openability.
[0005] One goal of the can end manufacturers is to provide a buckle
resistant end. U.S. Pat. No. 3,525,455 (the '455 patent) describes
a method aimed at improving the buckle strength of a can end having
a seaming curl, a chuckwall, and a countersink along the peripheral
edge of a central panel. The method includes forming a fold along
at least substantially the entire length of the chuckwall. The fold
has a vertical length that is approximately the same length as the
seaming curl, and a thickness that is approximately equal to the
length of the remaining chuckwall wherein the fold is pressed
against the interior sidewall of the container when the end is
seamed to the container's open end.
[0006] Another goal of the manufacturers of can ends is to reduce
the amount of metal in the blank end which is provided to form the
can end while at the same time maintaining the strength of the end.
One method aimed at achieving this goal is described in U.S. Pat.
No. 6,065,634 (the '634 patent). The '634 patent is directed to a
can end member having a seaming curl, a chuckwall extending
downwardly from the seaming curl to a countersink which is joined
to a central panel of the can end. The method of the '634 patent
reduces the amount of metal by reducing the cut edge of the blank.
This is accomplished by increasing the chuckwall angle from
approximately 11-13 degrees to an angle of 43 degrees.
[0007] The method of the '634 patent may decrease the diameter of
the central panel. This could reduce area on the central panel that
is needed for written instructions, such as opening instructions or
recycling information. It may also restrict the size of the tear
panel. Furthermore, because the angle of the chuckwall is
increased, the space between the perimeter of the can end and the
tear panel is increased. This could cause spillage during pouring
and/or drinking.
[0008] The method of the '634 patent also produces a countersink.
The '455 patent shares this aspect. The countersink is provided in
the can end to improve strength. However, because the countersink
is a narrow circumferential recess, dirt will often collect within
the countersink. Additionally, the dirt is often difficult to rinse
away due to the geometry of the countersink.
SUMMARY OF THE INVENTION
[0009] One object of the present invention is to provide an easy
open can end member comprising a central panel, a seaming curl, a
circumferential chuckwall, and a transition wall. The central panel
is centered about a longitudinal axis and has a substantially
planar peripheral edge. The seaming curl defines an outer perimeter
of the end member. The chuckwall extends downwardly from the
seaming curl. The transition wall connects the chuckwall with the
substantially planar peripheral edge of the central panel. The
transition wall comprises a folded portion extending outwardly
relative to the longitudinal axis.
[0010] Another object of the present invention is to provide an
easy open can end member comprising a central panel, a seaming
curl, a circumferential chuckwall, and a transition wall. The
central panel is centered about a longitudinal axis and has a
substantially planar peripheral edge, a public side and a product
side. The seaming curl defines an outer perimeter of the end
member. The chuckwall extends downwardly from the seaming curl. The
transition wall connects the chuckwall with the peripheral edge of
the central panel and comprises a fold including a concave annular
portion engaging the peripheral edge of the central panel.
[0011] Another object of the present invention is to provide an
easy open can end member comprising a central panel, a seaming
curl, a circumferential chuckwall, and a transition wall. The
central panel is centered about a longitudinal axis. The seaming
curl defines an outer perimeter of the end member. The
circumferential chuckwall extends downwardly from the seaming curl
at an obtuse angle. The transition wall connects the chuckwall with
the central panel, and the transition wall comprises a fold having
a portion extending outwardly relative to the longitudinal axis and
upwardly relative to the central panel wherein the fold has a
thickness which is substantially less than a length of the
chuckwall.
[0012] Another object of the present invention is to provide an
easy open can end member comprising a central panel, a seaming
curl, a circumferential chuckwall, and a transition wall. The
central panel is centered about a longitudinal axis and has a
peripheral edge. The seaming curl defines an outer perimeter of the
end member and is adapted for connecting the end member to a
container body. The chuckwall extends downwardly from the seaming
curl. The transition wall connects the chuckwall with the
peripheral edge of the central panel, and comprises a fold
extending outwardly relative to the longitudinal axis and upwardly
relative to the central panel. The transition wall has a vertical
length that is less than a length of the seaming curl.
[0013] Another object of the present invention is to provide an
easy open can end member comprising a central panel, a seaming
curl, a circumferential chuckwall, and a transition wall. The
central panel is centered about a longitudinal axis and has a
peripheral edge, a public side and a product side. The seaming curl
defines an outer perimeter of the end member. The chuckwall extends
downwardly from the seaming curl. The transition wall connects the
chuckwall with the peripheral edge of the central panel. The
transition wall comprises a fold including a concave annular
portion having an apex in engagement with the public side of the
peripheral edge of the central panel.
[0014] Another object of the present invention is to provide an
easy open can end member comprising a central panel, a seaming
curl, a circumferential chuckwall, and a transition wall. The
central panel is centered about a longitudinal axis and has a
substantially planar peripheral edge, a public side and a product
side. The seaming curl defines an outer perimeter of the end
member. The chuckwall extends downwardly from the seaming curl. The
transition wall connects the chuckwall with the peripheral edge of
the central panel. The transition wall comprises a fold including a
first leg extending downwardly from the chuckwall to a concave
annular portion having a first apex in engagement with the public
side of the peripheral edge of the central panel, a second leg
extending upwardly from the convex annular portion to a convex
annular portion, and a third leg extending downwardly from the
convex annular portion to a radial bend portion joined to the
peripheral edge of the central panel.
[0015] Another object of the present invention is to provide a
method for forming an easy open can end member comprising a central
panel, a seaming curl, a circumferential chuckwall, and a
transition wall. The method includes the step of providing a can
end shell including a central panel centered about a longitudinal
axis having a peripheral edge, a public side and a product side, a
seaming curl defining an outer perimeter of the can end shell, and
a circumferential chuckwall extending downwardly from the seaming
curl joined to a transition wall. The method also includes the step
of reforming the transition wall to form a fold having a portion
extending outwardly relative to the longitudinal axis.
[0016] Other features and advantages of the invention will be
apparent from the following specification taken in conjunction with
the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of a can end of the present
invention having a cutaway view of a portion of the perimeter;
[0018] FIG. 2 is a partial cross-sectional view of a can end member
of the present invention;
[0019] FIG. 3-8 are partial cross-sectional views of a can end
member of the present invention shown in forming stages;
[0020] FIG. 9-13 are partial cross-sectional views of a can end
member and tooling of the present invention shown in forming
stages;
[0021] FIG. 14 is a partial cross-sectional view of a can end of
the present invention; and
[0022] FIG. 15 is a partial cross-sectional view of a can end of
the present invention.
DETAILED DESCRIPTION
[0023] While this invention is susceptible of embodiment in many
different forms, there are shown in the drawings and will herein be
described in detail preferred embodiments of the invention with the
understanding that the present disclosure is to be considered as an
exemplification of the principles of the invention and is not
intended to limit the broad aspect of the invention to the
embodiments illustrated.
[0024] The container end of the present invention is a stay-on-tab
end member 10 with improved physical properties including strength.
Essentially, the present invention provides a lightweight end
member 10 which embodies the physical characteristics and
properties required in the beverage container market, as explained
below.
[0025] Referring to FIG. 1, the end member 10 for a container (not
shown) has a seaming curl 12, a chuckwall 14, a transition wall 16,
and central panel wall 18. The container is typically a drawn and
ironed metal can such as the common beer and beverage containers,
usually constructed from a thin sheet of aluminum or steel that is
delivered from a large roll called coil stock of roll stock. End
closures for such containers are also typically constructed from a
cut edge of thin sheet of aluminum or steel delivered from coil
stock, formed into blank end, and manufactured into a finished end
by a process often referred to as end conversion. In the embodiment
shown in the Figures, the end member 10 is joined to a container by
a seaming curl 12 which is joined to a mating curl of the
container. The seaming curl 12 of the end closure 10 is integral
with the chuckwall 14 which is joined to an outer peripheral edge
portion 20 of the central panel 18 by the transition wall 16. This
type of means for joining the end member 10 to a container is
presently the typical means for joining used in the industry, and
the structure described above is formed in the process of forming
the blank end from a cut edge of metal sheet, prior to the end
conversion process. However, other means for joining the end member
10 to a container may be employed with the present invention.
[0026] The central panel 18 has a displaceable tear panel 22
defined by a curvilinear frangible score 24 and a non-frangible
hinge segment 26. The hinge segment 26 is defined by a generally
straight line between a first end 28 and a second end 30 of the
frangible score 24. The tear panel 22 of the central panel 18 may
be opened, that is the frangible score 24 may be severed and the
tear panel 22 displaced at an angular orientation relative to the
remaining portion of the central panel 18, while the tear panel 22
remains hingedly connected to the central panel 18 through the
hinge segment 26. In this opening operation, the tear panel 22 is
displaced at an angular deflection, as it is opened by being
displaced away from the plane of the panel 18.
[0027] The frangible score 24 is preferably a generally V-shaped
groove formed into the public side 32 of the central panel 18. A
residual is formed between the V-shaped groove and the product side
34 of the end member 10.
[0028] The end member 10 has a tab 36 secured to the central panel
18 adjacent the tear panel 22 by a rivet 38. The rivet 38 is formed
in the typical manner.
[0029] During opening of the end member 10 by the user, the user
lifts a lift end 40 of the tab 36 to displace a nose portion 42
downward against the tear panel 22. The force of the nose portion
42 against the tear panel 22 causes the score 24 to fracture. As
the tab 36 displacement is continued, the fracture of the score 24
propagates around the tear panel 22, preferably in progression from
the first end 28 of the score 24 toward the second end 30 of the
score 24.
[0030] Now referring to FIG. 2, the central panel 18 is centered
about a longitudinal axis 50. The seaming curl 12 defines an outer
perimeter of the end member 10 and is integral with the chuckwall
14. The chuckwall 14 extends downwardly from the seaming curl 12 at
an obtuse angle. A chuckwall angle .alpha. measured from a planar
or substantially planar peripheral edge portion 52 of the central
panel 18 is generally between 10 and 70 degrees, more preferably
between 15 and 45 degrees, and most preferably 19 to 27 degrees, or
any range or combination of ranges therein. The chuckwall 14 may be
provided with a radius of curvature as shown in the drawings to
improve performance within the forming tools used to form the end
member 10. The radius of curvature helps prevent buckling within
the tools as force is applied to the unfinished end member 10.
[0031] The transition wall 16 is integral with the chuckwall 14 and
connects the chuckwall 14 the to the peripheral edge portion 52 of
the central panel 18. The end member 10 differs from contemporary
beverage can end members that typically include a countersink
formed in the outer peripheral edge of the central panel. The
planar peripheral edge portion 52 allows the tear panel 24 to be
place closer to the outer perimeter of the end member 10. It also
provides additional central panel 18 area for printing and/or a
larger tear panel opening.
[0032] The transition wall 16 includes a fold 54 extending
outwardly relative to the longitudinal axis 50. The drawings show
the fold 54 formed along an exterior portion of the chuckwall 14;
however, it should be understood that the fold 54 transition wall
16 can be located in other locations such as along the product side
34 of the central panel 18.
[0033] The fold 54 has a first leg 56 connecting the chuckwall 14
to an annular concave bend or portion 58. The annular concave
portion 58 includes and apex 60 which engages the outer peripheral
edge 52 of the central panel 18. This contact between the apex 60
and the outer peripheral edge 52 helps to prevent dirt from
accumulating along the peripheral edge 52 of the central panel 18.
It also allows the central panel 18 to be easily cleaned when dirt
or other residue is present on the central panel 18.
[0034] A second leg 62 extends upwardly from the annular concave
portion 58 to an annular convex bend or portion 64. The second leg
62 can be vertical, substantially vertical, or up to .+-.25 degrees
to the longitudinal axis 50 and can be pressed against an outer
portion of the first leg 56.
[0035] The annular convex portion 64 includes an apex 66 which
defines a vertical extent of the fold 54. A length of the fold 54
is substantially less than a length of the seaming curl 12. In
combination with, inter alia, the angled chuckwall 14, this fold 54
structure and length allows the buckling strength of the end member
10 to be meet customer requirements while decreasing the size of
the cut edge blank and maintaining the diameter of the finished
end. In other words, a smaller cut edge blank can be provided to
produce the same sized diameter end member as a larger cut edge
blank formed in the conventional manner with a countersink.
[0036] A third leg 68 extends downwardly from the annular convex
portion 64 to a third bend 70 which joins the transition wall 16 to
the outer peripheral edge 52 of the central panel 18. The third
bend 70 has a radius of curvature which is suitable for connecting
the third leg 68 to the planar outer peripheral edge of the central
panel 18.
[0037] The third leg 68 can be pressed against an outer portion of
the second leg 62. This gives the fold 54 a transverse thickness
which is substantially equal to three times the thickness of the
thickness of the chuckwall 14, and is the transverse thickness of
the fold 54 is substantially less than the length of the chuckwall
14. Again, this structure results in a metal savings by allowing
the cut edge blank to be smaller than conventional cut edge blanks
used to make the same diameter end member. For example, the average
diameter of a cut edge blank used to form a standard 202 can end is
approximately 2.84 inches while the average diameter of a cut edge
blank used to form a 202 can end of the present invention is
approximately 2.70 inches.
[0038] FIGS. 3-8 and FIGS. 9-13, illustrate one method for forming
an end member 10 of the present invention. FIGS. 3-8 show the
progression of the end member 10 from a shell to the finished end
10 without the tooling. FIGS. 9-13 show the tooling contemplated
for forming the end member 10. The method shows the fold 54 formed
from a lower segment of the chuckwall 14 called referred to as the
transition wall 16 herein. However, it should be understood that
the transition wall 16 can be formed from a portion of the
peripheral edge 52 of the central panel 18 without departing from
the spirit of the invention.
[0039] Referring to FIGS. 3 and 9, the method includes the step of
providing an end shell 80. The end shell 80 includes a hinge point
82 formed at the junction between the chuckwall 14 and the
transition wall 16. In FIG. 4, the hinge point 82 is a coined
portion on an interior of the end shell 80. In FIG. 9, the hinge
point 82 is a coin on the exterior of the end shell 80. The hinge
point 82 may also be provided along the peripheral edge 52 of
central panel 18. The hinge point 82 is provided to initiate
bending at a predetermined point along the chuckwall 14/transition
wall 16. In this example, the hinge point 82 defines the boundary
between the chuckwall 14 and the transition wall 16.
[0040] The end shell 80 also includes an angled portion 84 along
the peripheral edge 52 of the central panel 18. This angled portion
is formed to promote stacking of the end shells 80 as they are
transported from a shell press to a conversion press. The angled
portion 84 also promotes metal flow outwardly relative to the
longitudinal axis 50 to promote formation of the fold 54 in the
conversion press.
[0041] FIGS. 4-8 and 10-13 show a process of converting the end
shell 80 to the finished end member 10 in a four stage operation
carried out in a conversion press. In the first stage (FIGS. 4, 5
and 10), relative movement between the tooling members causes an
outward bulge (the beginning of the annular convex portion 64) to
form in the transition wall 16. The bending of the transition wall
16 is initiated at the hinge point 82 (the beginning of the annular
concave portion 58). At the same time, the angled portion 84 of the
peripheral edge 52 is flattened to form the peripheral edge 52 into
a planar structure. The relative movement of the tooling also
causes the hinge point 82 to move towards the flattened peripheral
edge 52 of the central panel 18.
[0042] FIGS. 6 and 11 illustrate the second stage of the conversion
press. In the second stage, relative movement by the tooling forces
the hinge point 82 towards the peripheral edge portion 52. The
annular convex portion 64 is fully formed and extends outwardly
substantially perpendicular to the longitudinal axis 50. A portion
of the hinge point 82 is engaging or very nearly engaging the
peripheral edge 52 of the central panel 18.
[0043] FIGS. 7 and 12 illustrate the third stage of the conversion
press. In the third stage, relative movement by the tooling forces
the fold 54 upwardly relative to the central panel 18. This forms
the third bend 70 and shortens a radius of curvature of the annular
concave portion 58.
[0044] FIGS. 8 and 13 illustrate the fourth stage of the conversion
press. In the fourth stage, relative movement by the tooling forces
the fold 54 farther upwardly relative to the central panel 18 until
the fold 54 is substantially vertical, parallel with the
longitudinal axis 50. The annular concave portion 58 is fully
formed and is in engagement or very nearly in engagement with the
peripheral edge portion 52.
[0045] FIG. 14 illustrates an alternative embodiment of the can end
10 of the present invention. In this embodiment, the fold 54
extends inwardly relative to the longitudinal axis 50. The annular
concave portion 58 does not contact the peripheral edge 52.
[0046] FIG. 15 illustrates yet another embodiment of the can end 10
of the present invention. In this embodiment, the chuckwall 14
includes an outwardly extending step 90 for increased strength. The
step 90 bends outwardly against the annular convex portion 64. In
this embodiment, the outer portion of the step engages vertical
extent of the annular convex portion 64.
[0047] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the broader
aspects of the invention. Also, it is intended that broad claims
not specifying details of a particular embodiment disclosed herein
as the best mode contemplated for carrying out the invention should
not be limited to such details.
* * * * *