CA2933754A1

CA2933754A1 - Can body

Info

Publication number: CA2933754A1
Application number: CA2933754A
Authority: CA
Inventors: Ralf WERSUHN
Original assignee: Ball Europe GmbH
Current assignee: Ardagh Metal Packaging Europe GmbH
Priority date: 2013-12-16
Filing date: 2014-10-14
Publication date: 2015-06-25
Also published as: US20160318645A1; CN105899433A; WO2015090669A1; MX2016007739A; EP3083420A1

Abstract

The invention relates to a can body (10) for a beverage can, which can body is formed from aluminum sheet metal as a single piece and has a circumferential wall (12) and a can bottom (14), which can bottom has a cup-like central section (16) curved inward and a standing section (18) that annularly surrounds the central section and is curved outward. The standing section curved outward is connected to the circumferential wall by means of an outer transition section extending aslant in the cross-section and defines a standing ring, along which the standing section at least approximately touches a flat surface when the can body is placed on such a flat surface. According to the invention, the can body has a diameter of less than 56 mm and the greatest sheet metal thickness of the formed aluminum sheet metal in the region of the cup-like central section curved inward is less than 0.25 mm.

Description

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

- 2 -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.

- 3 -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

- 4 -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

- 5 -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:

- 6 -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.

- 7 -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.

- 8 -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

- 9 -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.

Claims

1. A can body (10) for a beverage can, wherein the can body (10) is shaped in one piece from aluminum sheet and has a peripheral wall (12) as well as a can bottom (14), which latter has a central portion (16), which is curved inward in the shape of a dome, and a standing portion (18), which annularly surrounds the central portion and is curved outward and which is connected to the peripheral wall (12) by an outer transition portion (24), extending obliquely in cross section, wherein the annularly outwardly curved standing portion (18) defines a standing ring, along which the standing portion (18) at least approximately touches a plane surface when the can body is placed on such a plane surface, wherein the central portion (16) curved inward in the shape of a dome has a diameter of more than 36 mm, characterized in that the can body has a diameter (D) of less than 58 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.

2. The can body as claimed in claim 1, characterized in that the inwardly curved central portion 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.

3. The can body as claimed in claim 1 or 2, characterized in that 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.

4. The can body as claimed in at least one of claims 1 to 3, the bottom of which is firstly shaped and subsequently reformed in order to obtain a final geometry, characterized in that the curved central portion passes into an inwardly curved transition radius R2 into the standing portion, wherein the transition radius R2, at least prior to the reforming, measures between 1.5 mm and 1.9 mm.

5. The can body as claimed in at least one of claims 1 to 4, characterized in that the standing ring has a diameter between 43 mm and 46.5 mm.

6. The can body as claimed in at least one of claims 1 to 5, the bottom of which is firstly shaped and subsequently reformed in order to obtain a final geometry, characterized in that the standing portion bordering the standing ring, at least prior to the reforming, has mutually identical radii of curvature R3 a and R3 b which pass into each other.

7. The can body as claimed in at least one of claims 1 to 6, the bottom of which is firstly shaped and subsequently reformed in order to obtain a final geometry, characterized in 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, and the outwardly curved radius R5, prior to the reforming, measures between 3.0 mm and 3.5 mm.

8. The can body as claimed in at least one of claims 1 to 7, the bottom of which is firstly shaped and subsequently reformed in order to obtain a final geometry, characterized in that the 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 45 mm and a radius of curvature measuring between 0.8 mm and 1.2 mm exists.

9. The can body as claimed in at least one of claims 1 to 8, characterized in that this greatest sheet thickness of the shaped aluminum sheet is smaller than 0.1 mm, and preferably smaller than 0.09 mm.

10. The can body as claimed in at least one of claims 1 to 9, characterized in that the aluminum sheet has in the planar state, prior to being shaped into the can body, a sheet thickness of less than 0.25 mm.

11. The can body as claimed in at least one of claims 1 to 10, characterized in that the peripheral wall is at least almost cylinder-jacket-shaped and encloses a diameter of at least approximately 53 mm.

12. The can body as claimed in at least one of claims 1 to 11, characterized in that the can body has a filling volume between 150 ml and 250 ml.

13. The can body as claimed in at least one of claims 1 to 12, characterized in that the can body has a height between 85 mm and 145 mm.