Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 022~2~04 1998-10-21
W O 97139848 PCTrUS97/05205
~Y ~ ANnD PRO CESS FO R rnECKI NG CONrr~ T~r~.R
B AC KGROlJNnD OF I~DE lN V~N'llO N
1. Field of the Invention
This invention relates broadly to the field of
metallic containers, such as the two-piece cans that are
used for packaging beverages such as soft drinks and juices.
More specifically, this invention relates to an improved
process and system for necking metallic containers that will
result in fewer defects and in more efficient manufacturing
than was heretofore thought possible.
2. Description of the Prior Art
Two piece metal containers such as those
manufactured by the assignee of this invention, Crown Cork &
Seal Company, are in common use throughout the world for
packing beverages and other goods. In forming a two-piece
container, a metal blank is impact extruded or deep drawn to
produce a cylindrical body and an integral bottom end wall.
The second piece of the two-piece container consists of an
end panel that is separately formed and attached to the
upper end of the cylindrical body by a double seaming
process.
Initially, containers manufactured according to
this process had a larger outside diameter along the upper
edge where the double seaming operation has been performed
than the diameter of the remainder of the container. When
cans such as these were placed in a multi-pack carrier, such
as a so-called six-pack carton which grips the upper double
seam, the package, when viewed from the end, would be
slightly trapezoidal in shape. To overcome this problem, as
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well as to reduce the diameter of the can ends being applied
in order to save material, most two-piece beverage
containers are now being manufactured with a reduced
diameter neck portion that is produced on the upper free
edge of the integral body and bottom wall so that when a
double seam is formed, the outer edges of the seam are
approximately parallel or flush with the outer peripheral
surface of the remainder of the can body. This provides a
more compact packing of cans which in turn lowers the total
shipping and storage costs. Because of the reduced cost and
the pleasing esthetics of these types of containers, the
demand for containers of this type is substantial and is
continually increasing.
Typically, the reduction or necking process is
performed incrementally by passing the open end of the can
body through a number of reduction dies, each successive
reduction die reforming the necked area to a slightly
smaller diameter. As discussed in U.S. Patent 5,355,710 to
Diekhoff, the reduction increment from one die to the next
was preferably kept constant throughout the entire process.
During the reduction or necking process, defects
called l'puckers" and other local failures can occur in the
neck area. Misblends can also cause wrinkles in the neck.
In the past, efforts to minimize such defects involved
lessening the reduction increment from die to die (which
required more operations to achieve the desired reduction),
changing the clearance between the die and the support tool,
and increasing the accuracy by which the can body is
positioned for each step. Although such efforts have proved
successful to some extent, better results are being sought.
In particular, there is an need for any improvements that
will decrease the number of operations that are necessary to
achieve the desired reduction and not increase defects, or
that will reduce the number of defects when compared to
systems and processes heretofore known.
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SUMM~RY OF THE lNv~WllON
Accordingly, it i.s an object of the invention to
provide an improved process and system for decreasing the
number of operations that are necessary to achieve the
desired reduction in a necking system and not increase
defects, or that will reduce the number of defects when
compared to systems and processes heretofore known.
In order to achieve the above and other objects of
the invention, a process of incrementally necking an upper
end of a metallic container that has a first radius
includes, according to a first aspect of the invention,
steps of die pressing the upper end of the metallic
container so the upper end is reformed to a second radius,
the second radius being less than the first radius by a
first distance; and then die pressing the upper end of the
metallic container so the upper end is reformed to a third
radius that is less than the second radius by a second
distance, and wherein the second distance is greater than
the first distance, whereby the process is performed in
steps that increase in the amount of radial reduction that
is applied, rather than in equal amounts of reduction as has
heretofore been conventional.
According to a second aspect of the invention, a
process of incrementally necking an upper end of a metallic
container includes steps of perfvnniny a first stage
operation to reduce a radius of the upper end by a first
distancei performing a first subsequent operation that is
subsequent to the first operation to reduce the radius of
the upper end by a second distance; performing a second
subsequent operation that is subsequent to the first
subsequent operation to reduce the radius of the upper end
by a third distance; and performing a third subsequent
operation that is subsequent to the second subsequent
operation to reduce the radius of the upper end by a fourth
distance, and wherein the third distance is larger than the
second distance and the fourth distance is larger than the
third distance, whereby the increments of reduction become
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larger as the radius of the can end becomes smaller and wall
thickness increases.
An improved process of necking an upper end of a
metallic container that will reduce the incidence of defects
such as wrinkles and puckers during the necking process,
according to a third aspect of the invention steps of
performing a first stage operation to reduce a radius of the
upper end by a first distance; and incrementally further
reducing the radius of the upper end by performing a
plurality of subsequent reduction operations on the upper
end, this second step being performed so that the amount of
radius reduction that is applied by earlier of the
subsequent reduction operations is less than the amount of
radius reduction that is applied by later of the subsequent
reduction operations, whereby increases of wall thickness
that occur during the subsequent reduction operations will
be utilized to permit greater radial reduction in the later
steps, and will ease the amount of radial reduction in the
earlier steps when compared to processes heretofore known or
practiced.
These and various other advantages and features of
novelty which characterize the invention are pointed out
with particularity in the claims annexed hereto and forming
a part hereof. However, for a better understanding of the
invention, its advantages, and the objects obtained by its
use, reference should be made to the drawings which form a
further part hereof, and to the accompanying descriptive
matter, in which there is illustrated and described a
preferred embodiment of the invention.
BRIEF DESCRIPTION OF 1~ DR~WINGS
FIGURE 1 is a diagrammatical depiction of a
necking process that is performed according to a first
embodiment of the invention;
FIGURE 2 is a diagrammatical depiction of the
necking process shown in FIGURE 1;
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FIGURE 3 is a diagrammatical depiction of a
necking process that is performed according to a second
embodiment of the invention;
FIGURE 4 is a diagrammatical depiction of the
necking process shown in FIGURE 3; and
FIGURE 5 is a diagrammatical view of a system for
performing the processes which are depicted in FIGURES 1-4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)
Referring now to the drawings, wherein like
reference numerals designate corresponding structure
throughout the views, and referring in particular to FIGURES
1 and 2, a preferred first embodiment of a process of
incrementally necking an upper end 10 of a metallic
container that has a first radius Rc will be performed by an
otherwise conventional necking die assembly 14 on a can body
16, as is diagrammatically depicted in FIGURE 5.
A process according to the invention which is
performed in accordance with the embodiments of FIGURES 1
and 2 will be a nine stage process, meaning that there are
nine separate stages of radial reduction that are applied to
the upper end 10 of the metallic container in order to reach
the desired final configuration. In the embodiment that is
depicted in FIGURES 3 and 4, an eleven stage process is
shown, meaniny that there are eleven separate stages of
reduction to achieve the desired final configuration.
Common to both embodiments is the step of performing a first
stage operation to reduce a radius Rc of the upper end 10 of
the metallic container by a first distance, in order to
begin the necking process. In the embodiment of FIGURES 1
and 2, this first stage operation reduces the radius Rc by a
distance that is approximately 0.0410 inches, which is about
18.39~ of the entire diametrical reduction that is to be
visited upon the can body during the entire process. In the
process that is depicted diagrammatical in FIGURES 3 and 4,
the first stage will effect a radial reduction of
approximately 0.0335 inches, which is about 14.89~ of the
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total reduction that will be applied to the upper end 12 of
the metallic container. As is known in the industry, the
first stage operation is larger because it must form both an
outer and an inner bend radius.
After the first stage operation is performed, a
number of incremental subsequent operations must be
performed to reform the upper end 10 of the metallic
container to its desired final configuration. In the
embodiment that is performed as shown in FIGURES 1 and 2,
this is achieved by incrementally reducing the radius of the
upper end 10 by eight different operations that are given
the appellations "STAGE TWO" to "STAGE NINE". In the
embodiment shown in FIGURES 3 and 4, the subsequent
operations, of which there ten, are labeled "STAGE TWO"
through "STAGE ELEVEN".
According to one very important aspect of the
invention, these subsequent reduction operations that are
performed on the upper end 10 of the metallic container are
categorized such that the amount of radius reduction that is
applied by earlier of the subse~uent reduction operations is
less than the amount of radius reduction that is applied by
later of the reduction operations. As a result, increases
in wall thickness that occur during the initial reduction
operations will be utilized to permit greater radial
reduction in the later steps, which will ease the arnount of
radial reduction that is necessary in the earlier steps to
achieve a desired final configuration. This easing of the
magitude of reduction in the earlier operations reduces the
likelihood of wrinkling and pucking that might otherwise
occur in earlier reduction steps.
In the embodiment shown in FIGURES 1 and 2, the
STAGE TWO and STAGE THREE reductions are approximately
0.0210 inches, which constitute approximately 9.42% of the
total desired radial reduction. STAGE FOUR and STAGE FIVE
operations in this embodiment result in a radial reduction
that is, for each operation, approximately 0.0225 inches, or
about 10.09% of the final desired radial reduction. The
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STAGE SIX and STAGE SEVEN are greater, approximately 0.0235
inches or about 10.54% of the total desired reduction. The
final two stages, which are STAGES EIGHT and NINE, are given
in this embodiment radial reduction values of approximately
0.0240 inches, or about 10.76~ of the total radial
reduction.
In the embodiment of the invention that is shown
in FIGURES 3 and 4, STAGES TWO and THREE constitute a radial
reduction of approximately 0.0175 inches, or about 7.78~ of
the total desired reduction. The THIRD and FOURTH STAGES
give a radial reduction of approximately 0.0185 inches, or
about 8.22~ of the final desired reduction. The SIXTH and
SEVENTH reduction are approximately 0.0190 inches, which is
approximately 8.44~ of the desired overall reduction, while
the STAGE SEVEN reduction is approximately 0.0195 inches,
or about 8.76~ of the total desired reduction. The EIGHTH
STAGE reduction is approximately 0.0200 inches, or about
8.89% of the final desired reduction, while the TENTH and
ELEVENTH STAGES are each of about approximately 0.0210
inches, or about 9.33~ of the total desired reduction.
Conceptually, than, it may be said that one way to
express one aspect of the invention is that, after the FIRST
STAGE operation is performed, a first subsequent operation
is performed to reduce the radius of the upper end by a
second distance, and then a second subsequent operation is
performed to reduce the radius of the upper end by a third
distance. A third subsequent operation is than performed
subsequent to the second subsequent operation to reduce the
radius of the upper end by a fourth distance, and the third
distance is larger than the second distance, and the fourth
distance is larger than the third distance, so that the
increments of reduction become larger as the radius of the
can end become smaller and wall thickness increases.
An aspect of the invention that occurs within the
subsequent operation steps may be expressed as pressing the
upper end of the metallic container 10 so that the upper end
is preformed to a second radius that is less than an initial
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radius Rc of the can body. This characterization of the
invention would further include a step of, after the first
step, by pressing the upper end of the metallic container so
that the upper end is reformed to a third radius that is
less than the second radius by a second distance, wherein
the second distance is greater than the first distance so
that the process is performed in steps that increase in the
amount of radial reduction that is applied, rather than in
equal amounts of reduction as as heretofore been
lC conventional.
It is to be understood, however, that even though
numerous characteristics and advantages of the present
invention have been set forth in the foregoing description,
together with details of the structure and function of the
invention, the disclosure is illustrative only, and changes
may be made in detail, especially in matters of shape, size
and arrangement of parts within the principles of the
invention to the full extent indicated by the broad general
meaning of the terms in which the appended claims are
expressed.
