Note: Descriptions are shown in the official language in which they were submitted.
CA 02933754 2016-06-14
WO 2015/090669 - 1 -
PCT/EP2014/071946
Can body
The invention relates to a can body, in particular for
beverage cans.
So-called two-part beverage cans, consisting of a can
body and a lid, wherein can body and lid are typically
connected to each other in a leak-tight manner by a
double seam, are known. The lid itself can for its part
again be multipart, and typically has at least one pull
tab or a resealable closure.
The can body itself is shaped in one piece and from an
originally flat sheet. The methods and tools for
shaping a can body from sheet metal by means of
stretch-forming are fundamentally known. It is also
known that typical can bodies for beverage cans have an
inwardly curved bottom in order to lend the bottom
compressive strength. In the region of the (prior to
filling) open end of the can body, the can body is
typically provided with a tapered "neck", i.e. is
somewhat necked-in.
The aim when designing a can body is typically to
obtain sufficiently high strength with least possible
material usage and production complexity.
This object also forms the basis of the present
invention.
According to the invention, a can body for a beverage
can is proposed, wherein the can body is shaped in one
piece from aluminum sheet and has a peripheral wall as
well as a can bottom, which latter has a central
portion, which is curved inward in the shape of a dome,
and a standing portion, which annularly surrounds the
CA 02933754 2016-06-14
WO 2015/090669 - 2 -
PCT/EP2014/071946
central portion and is curved outward. The outwardly
curved standing portion is connected to the peripheral
wall by an outer transition portion, extending
obliquely in cross section, and defines a standing
ring, along which the standing portion at least
approximately touches a plane surface when the can body
is placed on such a plane surface. The diameter of the
inwardly curved central portion measures more than 36
mm. According to the invention, the can body has a
diameter of less than 60 mm and preferably less than 56
mm, and the greatest sheet thickness of the shaped
aluminum sheet in the region of the central portion
curved inward in the shape of a dome is smaller than
0.25 mm. The central portion of the bottom, curved
inward in the shape of a dome, has this greatest sheet
thickness roughly between its middle and the rim, in
which the inwardly curved central portion into the
standing portion.
Viewed from the outside, the inwardly curved central
portion is completely concave and forms a dome which
extends as far as the standing portion. The external
diameter of the inwardly curved central portion is
therefore only a little, in particular less than 10%
smaller than the diameter of the standing portion, i.e.
the continuously inwardly curved central portion
practically directly adjoins the standing portion. The
diameter of the inwardly curved central portion is
typically greater than 36 mm and generally also greater
than 40 mm.
Within the framework of this text, the terms
"inward(ly)" and "outward(ly)" are related to the
interior of the can body and not to a longitudinal axis
of the can body, so that an inward facing curve, viewed
from outside, is a concave curve and an outward facing
curve, viewed from outside, is a convex curve.
CA 02933754 2016-06-14
WO 2015/090669 - 3 -
PCT/EP2014/071946
Preferably, the aluminum sheet from which the can body
is shaped has in the planar state, prior to being
shaped into the can body, a sheet thickness of less
than 0.25 mm. This has the result that the sheet
thickness of the finish-shaped can body is at no place
within the standing ring greater than 0.25 mm, because
the sheet is stretched during the shaping of the can
body and thus becomes thinner. However, a thickening
can arise between the can wall and the standing ring,
so that the sheet thickness of the finished can can
there be somewhat greater than the sheet thickness of
the flat aluminum sheet prior to the shaping of the can
body (for instance 0.245 mm).
Moreover, it is preferred if the inwardly curved
central portion of the can body is defined by at least
a central radius of curvature R1 a and a peripheral
_
radius of curvature R1 _b smoothly adjoining this same,
of which the central radius of curvature R1 _a measures
between 39 mm and 45 mm and the peripheral radius of
curvature R1 b measures between 25 mm and 35 mm. In
this way, the central portion curved inward in the
shape of a dome acquires sufficient strength.
Furthermore, it is preferred if the standing portion,
together with the curved central portion, defines a
bottom depth as the greatest distance of the curved
central portion from a plane defined by the standing
ring, which bottom depth measures between 9.5 mm and 11
mm. The central portion curved inward in the shape of a
dome has its greatest distance from a plane defined by
the standing ring usually in its middle, so that the
bottom depth can be determined in the middle of the
central portion curved inward in the shape of a dome.
In addition, it is preferred if the can body is
reformed in the region of the bottom, following the
stretch-forming, in a manner which is known per se. In
this reforming operation, a further reshaping, in
CA 02933754 2016-06-14
WO 2015/090669 - 4 -
PCT/EP2014/071946
particular of the standing portion, into the final
geometry of the can body takes place. Preferably, an
inwardly curved transition radius R2, in which the
curved central portion passes into the standing
portion, has a measure between 1.5 mm and 1.9 mm, to be
precise prior to the reforming. In the stretch-forming,
this measure is defined by the tools which are used. A
measure of the transition radius of approximately 1.7
mm is particularly preferred.
In addition, it is preferred if the standing portion
bordering the standing ring (as the lowest point when
the can is upright (if the cross section is viewed -
actually it is a circle) of the standing portion), at
least prior to the reforming, has mutually identical
radii of curvature R3 a and R3 b which pass one into
the other without change of radius.
Another preferred geometrical feature of the bottom of
the can body is that the standing portion in the outer
transition portion passes with an inwardly curved
radius R4 and a thereto adjoining outwardly curved
radius R5 into the peripheral wall, wherein the
inwardly curved radius R4, prior to the reforming,
measures between 2.7 mm and 3.1 mm (preferably in the
order of magnitude of 2.9 mm), and the outwardly curved
radius R5, prior to the reforming, measures between 3.0
mm and 3.5 mm, i.e. for instance between 3.2 mm and 3.3
mm.
Preferably, the standing ring has a diameter between 43
mm and 46.5 mm.
In addition, preference is for a can body whose bottom
is reformed in a manner which is known per se with a
reforming tool in the region of the transition from the
standing portion to the inwardly curved central
portion, so that ultimately an inwardly curved inner
transition portion having a diameter between 43 mm and
CA 02933754 2016-06-14
WO 2015/090669 - 5 -
PCT/EP2014/071946
45 mm and a radius of curvature measuring between 0.8
mm and 1.2 mm exists. In the reforming operation, an
inner peripheral wall of the standing portion is
machined with a disk-shaped tool, which rolls along the
inner peripheral wall and in this way produces a
circumferential recess which is open toward a central
longitudinal axis of the can body and which in profile
has a rounding having a radius of about 1 mm,
corresponding to a cross-sectional radius on the
periphery of the disk-shaped tool for the reforming.
The reforming is preferably realized with a tool whose
smallest radius engaging with the can body to be
reformed measures between 0.8 mm and 1.2 mm, i.e., for
example, the aforementioned 1 mm.
With regard to the greatest sheet thickness of the
shaped aluminum sheet in a central region of the
peripheral wall (for instance at half the height of the
can body), it is preferred if this greatest sheet
thickness is smaller than 0.1 mm, and preferably
smaller than 0.09 mm. All in all, a very thin-walled
can body, which typically has the expected gripping
resistance only after filling and closure, by virtue of
an internal pressure, is obtained.
The peripheral wall of the can body is preferably
almost cylinder-jacket-shaped and preferably encloses a
diameter of less than 55 mm, and preferably at least
approximately 53 mm. Moreover, the can body is
preferably dimensioned such that it has a filling
volume between 150 ml and 250 ml and accordingly
preferably has a height between 85 mm and 140 mm.
An example of a can body of this type is explained in
greater detail with reference to the figures, of which:
CA 02933754 2016-06-14
WO 2015/090669 - 6 -
PCT/EP2014/071946
figure 1: shows a side view of a can body having
a filling volume of 250 ml and a bottom
geometry according to the invention;
figure 2: shows a side view of a can body having
a filling volume of 200 ml and a bottom
geometry according to the invention;
figure 3: shows a side view of a can body with
150 ml filling volume and a bottom
geometry according to the invention;
figure 4: shows a bottom geometry according to
the invention prior to the reforming,
in detail; and
figure 5: shows a bottom geometry according to
the invention after the reforming.
As is evident from figure 1, a can body 10 possesses a
substantially cylinder-jacket-shaped peripheral wall 12
and a bottom 14 having an inwardly curved central
portion 16, as well as a standing portion 18 which
surrounds said central portion and is connected to the
peripheral wall. The standing portion 18 is connected
to the peripheral wall 12 by a transition portion 24,
extending obliquely in cross section. Moreover, the
standing portion 18 has an inner peripheral wall 26
facing toward the central longitudinal axis Z.
At its in cross section lowest point (see figures 4 and
5), the standing portion touches a plane surface if the
can body 10 is placed upright on such a surface. These
lowest points are part of a circular standing ring,
along which the standing portion touches the plane
surface.
In the region of its upper open end 20, the diameter 10
possesses a short tapered portion 22.
CA 02933754 2016-06-14
WO 2015/090669 - 7 -
PCT/EP2014/071946
The height H and the diameter D of the can body are
marked and a central longitudinal axis Z is indicated.
The diameter of the can body depicted in figures 1 to 3
measures 53 mm.
Figure 1 shows the side view of a can body with 250 ml
filling volume, figure 2 shows correspondingly the side
view of a can body with 200 ml filling volume, and
figure 3 shows the side view of a can body with 150 ml
filling volume. The height H depends on the filling
volume and measures for the can body with 250 ml
filling volume in figure 1 just under 135 mm, for the
can body with 200 ml filling volume in figure 2 just
under about 111 mm, and for the can body with 150 ml
filling volume in figure 3 just under about 90 mm.
Figure 4 shows in detail the geometry of the can bottom
prior to the reforming. It is evident that the standing
ring defined by the depicted geometry, prior to the
reforming, possesses a diameter of somewhat more than
46 mm. In addition, it is evident that the central
portion 16 curved inward in the shape of a dome has a
central radius of curvature Rl_a, which preferably
measures between 39 mm and 45 mm, i.e. 42 mm for
instance. This radius of curvature passes into a
peripheral radius of curvature R1 b, which preferably
measures between 25 mm and 35 mm, i.e. 30 mm for
instance. The inwardly curved central portion 16 is
adjoined by the standing portion 18. A transition
radius between the inwardly curved central portion 16
and the standing portion 18 measures, prior to the
reforming, preferably between 1.5 mm and 1.9 mm, i.e.
1.7 mm for instance. In addition, the standing portion
18 is defined by an outwardly curved part in the
environment of the standing ring, wherein the outwardly
directed radii of curvature, bordering the standing
ring, respectively measure prior to the reforming
between 1.3 mm and 1.5 mm, i.e. 1.4 mm for instance.
CA 02933754 2016-06-14
WO 2015/090669 - 8 -
PCT/EP2014/071946
These curvatures around the standing ring pass into a,
viewed from outside, concave curvature in the region of
the obliquely running outer transition portion between
standing portion 18 and peripheral wall 12, wherein
this, viewed from outside, concave curvature preferably
has a radius between 2.8 mm and 3 mm, i.e. 2.9 mm for
instance. Finally, the obliquely running outer
transition portion passes into a, viewed from outside,
convex radius of 3.0 mm to 3.4 mm into the peripheral
wall 12.
The inwardly curved central portion of the bottom
possesses the greatest thickness roughly at the place
where, in figure 4, a "thickness" marking is indicated.
At this place, the inwardly curved central portion of
the bottom has roughly a sheet thickness which
corresponds to the sheet thickness of the sheet prior
to deformation into the can body, i.e. is smaller than
0.25 mm. If the can body is produced from an originally
flat aluminum sheet having an original sheet thickness
of 0.24 mm, the thickness marked in figure 4, in the
region of the inwardly curved central portion of the
bottom, likewise measures approximately 0.24 mm for
instance. By contrast, the peripheral wall 12 has after
the shaping a sheet thickness of about 0.09 mm.
Finally, figure 5 shows the final geometry of the
bottom after the reforming. It is evident that the
bottom depth, as a result of the reforming, has reduced
from initially somewhat more than 10 mm (compare figure
4, the measure DD FE) to finally somewhat less than 10
mm, namely 9.7 mm for instance (see figure 5, the
measure DD BE). The reforming is here realized with a
disk-shaped tool having a smallest radius, engaging
with the can body, of about 1 mm. In the reforming, the
center point of this radius is located roughly at a
distance of 2 mm to 3 mm from a plane defined by the
standing ring. In the reforming, the disk-shaped tool
rolls in machining operation on the inner peripheral
CA 02933754 2016-06-14
WO 2015/090669 - 9 -
PCT/EP2014/071946
wall of the standing portion, and in this way produces
a circumferential recess which is open toward the
central longitudinal axis of the can body and which in
profile has a rounding with a radius of about 1 mm,
corresponding to a cross-sectional radius on the
periphery of the disk-shaped tool for the reforming.
The recess which is produced by the reforming tool and
is open toward the central longitudinal axis of the can
body has a diameter (reforming dia) between 44 mm and
45 mm. These measures are likewise evident from figure
5.
In the illustrative embodiment, the material of the can
body is aluminum of alloy No. 3104 with a hardness
level H19 and a nominal sheet thickness of 0.245 mm.
