Note: Descriptions are shown in the official language in which they were submitted.
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R~lNEQRGE~ T~h C N A ER
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~ld_of ~ e tion
This invention relates to a two-piece food can, the
body and the bottom of which are produced by a drawn and wall
ironing process which is provided with body profilings having
strong vaultings or archings for preventing buckling, due to
differences between th~ inner and outer pressure on the can
a~ter the can is filled with hot product, and cooled.
Production of food cans is known as well as cans
for carbon dioxide containing drinks, with a body and bottom
made of one piece by a drawn and wall ironing process. This
saves considerably on sheet material, since it is possible by
such means to reduce the wall thickness of the body to consider-
ably lesser thicknesses.
However, the material saving, due to the drawn and
wall ironing process, cannot be realized with the design of
the heretofore produced two-piece food cans to an extent
desired. The reason for this lies in the fact that food cans
must resist, not only considerable axial thrust loads, but
equally implosion pressures without deformation of the body
of the can. For this reason, food cans with a body profiling
in the form of ring beads are arranged one above the other
which extend over the middle height range of the cans, prefer-
ably over half of the height of the can. The body regions
that are remote from both, the bottom and the top, are thus
appropriately reinforced. This reinforcement by means of the
ring or beads, which is effective against bulging of the can
body, results, however, in a reduction in the axial loading
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capacity of the cans. Nevertheless, a high axial load resis-
tance (thrust load) due to increasing heights of stacking of
the canned goods is required. It follows that for the improve-
ment of the axial load resisting capacity, the cans provided
with ring (annular) beads must also have a relatively great
wall thickness, even if produced by drawn and wall ironing
process so that even by this process the desired material-
saving cannot be obtained in the production of food cans
since a good implosion resistance has to be equally provided.
The object of the present invention is to design a
two-piece food can of the initially described kind so that
the body profiling for obtaining stability of shape against
an occurring implosion pressure will not result in an axial
load reduction of the can and thus the reduction of the
thickness of the wall that is obtainable by the drawn and
wall ironing process may be fully exploited and a consider-
able saving of the sheet material might be realized.
The solution of the above task requires that the
mentioned food can is characteri2ed according to the
invention in that the can body is provided on its entire
circumference, at least on its midsection, that is, over at
least a quarter of its height, with profiles and beads
arranged in rows directly above and next to another which at
their greatest dimension measure up to 20 mm, preferably from
6 to 10 mm, and have a maximal depth from 0.1 to 0.7 mm,
preferably from 0.2 to 0.5 mm and are separated one from the
other by small webs.
By means of a new profiling of the can body that is
applied for the purpose of obtaining the highest possible
3Q loads appropriately over the entire height of the can and, as
indicated, over the whole circumference an increase of the
axial strength and resistance to implosions is obtained so
that the respective reduction of the thickness of the body of
the cans can be realized. Practical results have
demonstrated that the thickness of the wall of the body of
the food can designed according to the invention can be
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reduced with the above inclicated values for the axial stren~th
and the resistance against implosions by up to 20%. A consider-
able material saving can be obtained in this manner while
taking into consideration that food cans are typically mass
produced goods.
For manufacturing considerations, stamping marks of
a similar kind are appropriately arranged on the can body, so
that stamping marks of a waffer or a honeycomb pattern are
formed. This, however, does not preclude providing the can
bodies also with a combination of different stamping marks
and is considered within th~ scope of the invention. It is
thus possible to arrange stamping marks of a wider extension
or with stamping marks of smaller extensions circumferentially
or placed interchangeably one about the other.
It is especially advantageous when the stamping
marks are rhombic, rhomboidal or elliptical, that their
length to width radio be between 10 to 3 and 10 to 8. The
arrangement of these stamping marks may be realized so that
the longitudinal axes of the stamping marks proceed inclined
toward the longitudinal direction of the cans and adjacent
stamping marks show oppositely inclined longitudinal axes, so
that the longitudinal axes of each circumferential line (row)
of stamping marks forms a zig-zag configuration. It is
further possible to have the stamping marks arranged on the
circumference one next to the other, offset in the direction
of the hei~ht of the can arranged one against the other.
It proved to be especialy appropriate to form the
stamp marks as indentations from the ou-tside inward so as to
orient them with their longitudinal axes in the vertical
(axial) direction of the can.
The design of the stamp marks as indentations from
the outside inward is realized according to the carried out
experiments with a substantially higher axial loading capacity
of the can than the equally possible indentation applied from
the inside toward the outside. The orientation of the longi-
tudinal axes of the indentations in the direction of the
height (vertical) of the can leads also to higher values of
axial loading capacity of the can than the arrangement of the
impressions with longitudinal axes in the circumferential
direction.
Thus, for example, impressions were found on cans
with the same stamp marks but differently arranged, i.e.,
once in the direction of ~he height and another time in the
circumferential direction of the cans:
Thickness Depth of the Orientation of Axial strength
the sheet mm imprint Max.mm the sample N (kp)
vertically in- 8446 N (861 kp)
ward stamp mark
0.23 0.8-0.9 vertically 7220 N (736 kp)
horizontally, 6150 N (627 kp)
outward stamp
mark
In case of the above-mentioned values for axial
strengths, average values are given obtained each from 10
measurements.
As comparison for the above axial strengths the
measuring was made with a can of equal sheet metal thickness
having in the middle height area 15 beads densely one next to
the other, of a maximal depth of 0.45 mm and of an axial
strength of only 5837 N (595 kp). Were the depth of the beads
brought to values corresponding to the maximal depth of the
imprints of the samples, the axial strength would surely drop
considerably below these values.
The above values show clearly tha-t a vertical
orientation of stamp marks with lontigudianl axes proceeding
in heightwise directions and an impression directed inward
from the outside leads to the best results.
The application of the stamp marks into the body
walls does not cause any technological difficulties of the
device. It is thus possible, for example, to work with two
stamping rollers designed like matrices and patrices (male
molds), profiled according to the stamping marks, so that the
same pair of stamping rollers can produce stamping marks of
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different depth depending on the grade of adjustmen-t of the
stamping rollers. It is not even nec~ssary h~re to adjust
the patrix in its profile precisely to the matrix. Moreover,
it suffices to provide the patrix with naplike elevations
which penetrate into the middle area of the respective trough-
shaped impressions of the matrix. By adjustment of different
working depths it is thus possible to change simply the depth
of stamping with the same pair of rollers. Experience has
shown that also with a relatively smaller depth of pen~tration
of the elevations provided on the patrices, a sufficient
formation of stamp marks is made according to the outer
outline of the impressions (indentations) present in the
matrix.
These and other objects inherent in and encompassed
by the invention will become more apparent from the following
specifiations and drawings wherein:
Fig. 1 is a perspective view of a food can illustrat-
ing the invention with a portion of the side wall of the
container shown as an actual representation and the remainder
diagrametically;
Fig. 2 shows a section of the body wall of the can
according to Fig. l;
Fig. 2a shows a section along the line A-A of
Fig. 2;
Figs. 3 and ~ show schematic illustrations of
modifications of body imprints in an orientation that differs
from that of Figs. 1 and 2.
DESCRIPTION OF THE INVENTION
The food can according to the illustration in Fig.l
is of two parts. It consists of the body la which is produced
by a drawn and wall ironing process with the bottom in one
piece according to know methods. The open side of the can is
closed in a conventional manner by a seamed-on cover 3.
The bottom 2 may be provided with a ring or annular
bead that is not shown in the drawing and is spaced from the
outer edge of the bottom and extends into the interior of the
can.
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The can illustra-ted in Fig. 1 is provided over the
entire circumference and also over the entire height of the
body with stamping marks 4, vaul~ed outwardly, reproduced in
detail within the area surrounded by the dash-dotted line 5
and indicated elsewhere by ha-tched lines only. The imprints 4
are separated in comparison to their measured areas by narrow
webs or veins 10, as clearly shown in Fig. 2. The stamping
marks 4, represented in the example of embodiment, show
rhombic shapes, however, with rounded edges and are linearly
1~ arranged circumferentially, as well as in the direction of
height of the can next to each other so that a waffer- or
honeycomb-shaped sample is produced in its entirety that is
seen in Figs. 1 and 2.
In the illustrated example in which the actual size
of the stamp marks according to Fig. 2 are illustrated, the
size or the extent of the individual rhombi in longitudinal
direction as shown by the double arrow 6 in Fig. 2 amounts to
about 10 mm, which the width as defined by the double arrow
in Fig. 2 is about 8 mm. Thus a ratio of length to width of
,Q 10 to 8 exists in this case.
In the illustrated example, the maximal depth 8
according to the illustration in Fig. 2a is about 0.35 to
0.50 mm. In comparison with three-piece cans, there is thus
a reduced thickness of the metal sheet of the body wall,
since the three-piece cans must have a thickness of wall of
at least 0.15 based on the heretofore applicable economical
rolling technologies.
As is further illustrated in Figs. 1 and 2, the
rhombic stamping marks 4 are provided in this example of
embodiment so that the longitudinal axes 7 extend in the
direction of height of the can 1.
Differently from the embodiment represented in
Figs. 1 and 2, the stamping marks can also be rhomboidal or
elliptical and may be oriented relative to their longitudinal
axes differently, as is indicated in Figs. 3 and 4.
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In the embodiment according to Fig. 1, the linearly
in parallel arranged or adjacent stamping marks are inclined
in opposite sense to the dash-dotted indication of the line
in the direction of the height 10 of the can and ~orm stamping
marks around the circumference of the can proceeding in a
zig-zag arrangement.
In the arrangemen-t according to Fig. 4, the middle-
longitudinal lines 7a and 7b of the stamping marks, placed
one next to the other in a circumferential direction, are
also offset in their elevational heightwise direction.
By the selection of the shape of the stamping marks
as well as of the depth of the stamp marks and finally also
by the extension of the stamping marks on the circumference
of the can, for example over 1/4 to 1/2 of the hieight of the
can in its middle height range, it is possible to produce
cans of a different maximal axial load or thrust load in
order to satisfy the re~uirements of the users of these cans.
Nevertheless, it is possible to obtain by means of the described
profiling of the cans with said stamping marks, a considerable
increase of the maximal axial -thrust load in comparison with
cans with ring or annular beads, so that the reduction of the
wall thickness by means of a drawn and wall ironing process
may be applied to food cans and a considerable saving of
material can thus be obtained.
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