Note: Descriptions are shown in the official language in which they were submitted.
1046859
This application is divided out of copending Canadian patent appli-
cation No. 190,525, filed January 21, 1974.
The present invention relates generally to a method of producing con-
tainer ends and more particularly an improved fully opening end.
Containers having easy open ends have become well-known in recent
years and now enjoy a considerable measure of consumer acceptability. One type
of easy open end is a full open end closure that normally includes an end panel
that is permanently secured to one end of a container body by a permanent seam
and has a weakened score line adjacent the permanent connection to define a
removable section. An opening tab is secured to a portion of the removable
section, normally through an integral rivet forming part of the removable sec-
tion. Containers having full open ends are used for packaging various types of
products, such as coffee, nuts, candy and foods containing liquid.
To separate the removable section from the permanently secured sec-
tion, the opening tab is moved along a path by initially pivoting the tab
towards the permanent seam to cause a downward movement of the portion of the
removable section between the rivet and the score line to initiate rupture of
the score line or weakened area. Subsequently, the tab is pulled in an opposite
direction along a path away from the initially ruptured section until the en-
tire score line has been ruptured and the removable section is detached from
the permanent section.
As is explained in the co-pending Canadian application 155,418 filed
November 2, 1972, one difficulty encountered in full open end closures is that
the severed edge of the removable section tends to become located under the
adjacent edge of the permanently secured section during initial rupture of a
portion of the weakened area of the score line, making it extremely difficult,
if not impossible, to remove the entire closure.
In the co-pending application, it is explained that this is believed
to be in part caused by loose metal in the removable section resulting from the
scoring operation which forms the score line or weakened area that defines the
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1~468S9
removable portion of the end. This problem has been at least partially solved
by providing a trough adjacent the rivet as well as a circumscribing bead
located adjacent the weakened area to take up excess metal that is produced in
the removable section during the formation of the finished end shown in the
above application. As explained therein, the trough and circumferential bead
also provides the advantage of preventing crowning between opposite edges of
the removable section while it is being separated from the permanent section.
A further problem is that the normal scoring operation results in
considerable stress concentration in the metal in the score line or frangible
connection and often produces a small crack in the weakened area which thereby
may result in fracture of the weakened area before it is desired.
In the normal scoring operation, the score line is produced by sup-
porting one surface of the panel on a flat support and forcing a truncated V-
shaped scoring member into the opposite surface of the panel. During the
scoring operation, the metal that is located below the flat portion of the
truncated V-shaped scoring member is displaced substantially normal to the panel
and results in the large stress concentration in the weakened area of the score
line. It has been found that such a scoring operation normally results in at
least a small crack adjacent either corner or edge of the reduced cross-section
or weakened area which will enhance the possibility of fracture of the weakened
area before desired. Stated another way, the portion of the metal directly
below the flat surface of the scoring element will act as a slug that initially
c~nsists of a section of metal in the panel that has a thickness equal to the
thickness of the panel and is reduced in thickness to that of the ultimate
thickness of the weakened area.
The problem of producing a small crack or fracture in the weakened
area of the removable end is particularly acute when utilizing a metal such as
tin plate for the end. Normally, such metals must be surface coated on both
surfaces of the panel to prevent the bare metal from being exposed to either
the contents of the container or the surrounding atmosphere. When utilizing
1~)4~59
a scoring operation of the type described above, one or both surface coat-
ings may be cracked or fractured during the scoring operation.
Another problem in the use of full open end closures has come
to light when using containers with these types of closures for packaging
certain products that are packaged at conditions other than atmospheric
pressure. It has been found that when certain products, such as coffee,
are packaged in containers of the type discussed above, the initial
rupture of the score line will result in an immediate equalization of the
pressure between the inside and outside of the container, which many times
results in the product being forced from the container through the initial-
ly ruptured area of the score line.
It is an object of the present invention to provide a method of
producing a container end which will obviate or mitigate at least one of
the above disadvantages.
Basically, the invention resides in a method of producing a
container end with a removable section comprising the steps of: forming
a weakened area in a panel circumscribing the removable section; and
expanding the panel in a direction generally parallel to the plane of
the removable section to remove any compressive forces developed in the
panel during the formation of the weakened area.
Preferably, the weakened area is produced by engaging opposed
surfaces of the panel with elements having opposed arcuate surfaces.
An embodiment of the invention will now be described, by way of
example, with reference to the accompanying drawings, in which:
Figure 1 is a plan view of an easy open end of the type shown
in the above mentioned application;
Figure 2 is an enlarged section as viewed along line 2~2 of
Figure l;
Figure 3 is an enlarged fragmentary sectional view showing the
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~046859
die elements and the step of producing the weakened area;
Figure 4 is a view similar to Figure 3 showing another step
in forming the container end shown in Figure l; - -
Figure S is an enlarged fragmentary sectional view similar to
Figure 3;
Figure 6 is an enlarged fragmentarr sectional view similar to
Figure 4, showing a relationship of the die elements and the panel adjacent
the weakened area;
Figure 7 is an enlarged sectional view of the weakened area
and the panel sections on opposite sides of the weakened area;
Figures 8 and 9 are views similar to Figures 3 and 4 respec-
tively showing the panel in its initially deformed condition and finally
deformed condition;
Figure lO is an enlarged fragmentary sectional view of the die
elements and the panel as viewed along line 2-2 of Figure l showing the
formation of the rivet and the area of reduced cross-section adjacent the
rivet;
Figure ll is a view similar to Figure 10 showing the final
configuration of the panel in the area of the rivet; and
Figure 12 is a fragmentary enlarged plan view of the panel
showing the rivet and the adjacent area of reduced cross-section.
Figures 1 and 2 of the drawings generally show the container
end lO that is formed in accordance with the teachings of the present
invention. The container end or fully open end 10 is generally shown and
described in the above mentioned co-pending application and consists of
panel 12 that is divided into a removable section 14 and a permanent or ad-
jacent section 16 interconnected along a weakened area or frangible con-
nection 18. The permanent section or rim 16 is adapted to be connected to
the end of a container body by the usual double seam ~not shown).
As explained in the above reference application, the removable sec-
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10468S9
tion 14 of the easy open end has a substantially continuous bead 20 that cir-
cumscribes the entire periphery of the removable section and is located in
close proximity a substantially constant dimension from the weakened area 18.
The bead 20 is interrupted at selected locations 22,24 and 26 that define
opposed pairs of interrupted portions to allow the removable section of the
panel to be bent during the removal process.
The removable panel has an integral rivet 28 located adjacent one of
the bead portions for connecting a tab thereto shown in phantom in Figure 1.
The removable section 14 of panel 12 also has a trough 32 located adjacent the
rivet 28 and further bead 34 between the trough and the rivet. In addition,
the removable section 14 has a downwardly dished portion 36 that is deformed
from the planar main body portion of the removable section to provide a small
space between the upper surface of the removable section and the lower surface
of the opening tab 30.
As explained in the above mentioned application, the beads 20 and 34
as well as the trough 32 and the dished portion 36 take up excess metal that is
developed during the formation of the weakened area 18 in panel 12. Further-
more, the beads and trough cooperate to act as means for preventing crowning o~ - -
bulging oP the removable section during the opening process and the interrup-
tions 22, 24 and 26 in the substantially continuous b~ead 20 will accommodate ;
- bending of the removable section during the opening process.
As was indicated above, the normal scoring operation to produce a
weakened area that defines a frangible connection between the removable section
and the permanently attached section of the panel results in an extreme concen-
tration of stresses in the frangible connection between the two sections. To
reiterate, the use of either of a sharp cutting tool or a trucated V-shaped
cutting tool to produce the weakened area results in atremendous concentration ~-
of stresses in the frangible connection or residual left between the panel sec-
tions which invariably results in small cracks developed in the frangible con-
3Q nection that weaken the connection.
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1046~59
According to the present invention, the frangible connection or
weakened area between the two sections of the panel is produced in a manner
that the material that must be displaced will flow into the main body of the
panel without the compression of the material in a direction generally normal
to the plane of the panel.
The configuration of the weakened area or frangible connection 18 is
shown in enlarged detail in Figure 7. As will be seen from an inspection of
Figure 7, the opposed surfaces of panel 12 are concave in the weakened area and
are indicated by the reference numerals 40 and 42. The concave surfaces 40
and 42 have radii that are located on opposite sides of the panel. While not
all points of the respective surfaces are located at the same point, because
of the expansion of the panel, when severing the radii of the surface segments,
they may be considered to have a common center.
The radii of curvature of the respective concave surfaces 40 and 42 -
are greater than the thickness of the panel and the centers of the two concave
surfaces 40 and 42 are located so that the width of the weakened area 18 is
greater than the thickness of the panel and the center or residual of the weak-
ened area or frangible connection has a thickness substantially less than the
thickness of the panel.
Also, it will be noted that the area between the removable panel sec- -
tion 14 and the adjacent section 16 is of cpnstantly reducing cross-section
towards the center of the reduced cross-section.
The weakened area 18 is produced in such a manner that the removable
section is devoid of any excess metal that would result in compressive forces
being developed which would cause the severed edge of the removable section to
expand under the adjacent severed edge of the permanent section during initial
rupture of the weakened area 18. The arcuate configuration of the opposed sur-
faces of the weakened area allows the metal to be displaced generally along the
plane of the panel while the weakened area is being formed to substantially
reduce the stress concentration in the weakened area at that time. However,
--6--
104~859
because a large amount of metal is displaced into the removable section of the
panel, the excess metal develops compressive forces in the rem~vable panel that
will tend to cause the panel to expand when the weakened area is ruptured.
The method of the present invention contemplates initially forming a
weakened area in the metal panel circumscribing the removable section and there-
after, expanding the panel in a direction generally parallel to the plane of
the removable section to remove any excess metal that would develop compressive
forces in the removable section. The two steps of deforming a flat panel to
the final configuration shown in cross-section in Figure 7 are generally shown
in Figures 3 and 4, while the details of the formation of the weakened area are
shown in the enlarged views of Figures 5 and 6. Prior to the formation of the
frangible connection, the panel 12 has been deformed to a cup shaped configura-
tion having a base portion 37 and a rim 38 and the base portion has rivet 28
formed therein. The rim 38 has a flange portion 39 that merges with the base
portion through an arcuate segment ( a portion of which is shown in Figures 3
and 5). Flange portion 39 defines an acute angle (a) with respect to a plane
extending normal to base portion 37.
Referring to Figure 3, a cup shaped panel, such as tin plate having
protective coatings on opposite surfaces thereof, is initially supported on a
female die 50 that has an upwardly directed opening 52 which has an arcuate
surface at the upper end thereof. The area of the female die element outside
of the opening 52 is configured to conform to the peripheral edge of the rim,
as shown in Figure 3.
The opposite surface of panel 12 is engaged with a male die element
54 that has an outside diameter which is smaller than the diameter of opening
52 and the lower end of the side wall of the male die element 54 has a first
arcuate surface 56 that merges with a second arcuate surface 58 which in turn
merges with the flat bottom surface 60 of the male die element.
The female die element also has an arcuate surface 62 that is in-
wardly spaced from the opening and is generally aligned with arcuate surface 58.
1046~59
The area of the female die element 50 inside the arcuate surface 58 has a flat
bottom wall 64 that is displaced downwardly with respect to the wall portion or
ledge 66 between the wall of opening 52 and arcuate surface 58.
When the die elements are moved towards each other, the cup shaped
panel will be deformed in the area of the base portion 37 and rim 38 to produce
weakened area 18. During this relative movement, the specific location of the
centers of the two surfaces 58 and 62, and the fact that the surfaces engage
the panel in the arcuate connections between base portion 37 and flange 39,
will allow the metal to flow along the arcuate surfaces 58 and 62 rather than
be compressed and produce the undesirable stress concentration in weakened area
18. At the same time the removable section 14 will be displaced downwardly
relative to the rim or permanent section of panel 12. In the specific embodi
ment illustrated, the removable section is displaced by a dimension substan-
tially equal to the thickness of the panel.
During the formation of the weakened area or frangible connection 18,
it is desirable to have the rim 38 remain in a static condition. This is accom-
plishet by making the radius of curvature of arcuate surface 56 equal to the
radius of curvature of the arcuate connection between flange 39 and base por- -
tion 37. This will cause all of the metal that must be displaced from the
weakened area to flow into the removable portion 14 of panel 12.
To eliminate the undesirable results of having excess metal in the
removable section 14, the portion of the panel outwardly of the flange 39 is
supported on a second female die element 80 having an opening 82 that is the
same diameter as the opening 52 in the first female die element 50. However,
opening 82 has sufficient depth so that the removable section remains unsup-
ported and the upper end of die element 80 has a configuration similar to die
element 50.
The opposite surface of panel 12 is then engaged with male die element
84, shown in Figure 4, that has an outer surface or side wall 86 which has a
diameter greater than that of die element 54 but less than the diameter of
1046859
opening 82. Also, die element 84 has its side wall 86 merging with a flat
bottom surface 88 along an arcuate surface 90 that has a radius of curvature
greater than that of surface 56.
Moving die elements 80 and 84 towards each other while rim or per-
manent section 16 is supported on die element 80 will cause the male die element84 to engage the surface of flange portion 39 and expand the panel 12 along a
plane extending generally through the body of the panel. During this expansion
of panel 12, the si~e of the acute angle defined between flange portion 39 and
a plane extending generally normal to the plane of the removable section 14
will be reduced and the removable section 14 will be displaced upwardly to the
position shown in Figure 4. This expansion will increase the size of the base
portion or flat portion 37 of panel 12 and locate frangible connection 18 in
the flat portion 37 while the outer edge of rim 39 remains in a static condi- -
tion
The advantages of the two step process of forming the weakened area
will now be briefly summarized. During the first step, which may be called
"cold swedging", all of the metal that is displaced from the weakened area
flows into the removable section or base portion 14 of the panel and will re- ~ -
sult in excessive metal being located in the removable section which develops
compressive forces that tend to expand the removable section. Thus, if the
panel were to retain this configuration, during initial rupture of the score
line, the compressive forces developed in the removable section would tend to
expand the panel during the initial rupture of the weakened area or frangible
connection and cause the severed edge of the removable section to be displaced
under the adjacent severed edge of the permanent section 16. However, by sub-
sequently expanding or sizing the area of the panel outside of the weakened
area or frangible connection 18 that is shown in Figure 6, sufficient expansion
of the removable section will result to remove any compressiYe forces developed
in the removable section and, in fact, in most instances, place the removable
section in tension~ If the removable section is placed in tension, the severing
~046859
of the weakened area or residual 18 will allow the removable section to assume
the non-stressed condition and thereby contract, which will result in having
the severed edges of the weakened area move away from each other. This arrange-
ment insures that there is no possibility of overlapping the adjacent severed
edges that would prevent removal of the panel.
It should be noted that during the expansion of the panel, the re-
movable section is displaced in a general direction normal to the plane of the
removable section and in a direction opposite or towards the male die element.
Also, since the panel is engaged outside the weakened area or frangible con-
nection, this frangible connection is placed in what may be termed the flatportion of the panel,i.e., inside the radius portion of the rim, as is clearly
shown in Figures 6 and 7.
While the relative dimensions of the various radii and diameters are
critical when considered with respect to each other, the specific dimensions
that will now be described are for purposes of illustration only. ~ -
For example, when deforming a metal panel having a thickness of 0.008
inches, the radius f in Figure 5 would be on the order of 0.025 inches while
the radius g would be on the order of 0.020 inches and the radius h of the fe-
male die element would be on the order of 0.014 inches. In addition, the
radius j would be on the order of 0.032 inches.
With a panel initially deformed to a cup shaped configuration, where- ~ -
in a flange 39 merges with the flat bottom wall or base portion 14 along a
radius f, the panel would be deformed to produce the weakened area 18 located
within the radius portion between the flange 39 and the base portion 14. At
the same time, the base portion or removable section 14 would be displaced in a
direction generally normal to the plane of the base portion 14 to the position
shown generally in Figure 5.
With the die elements as described, the minimum thickness of the
weakened area will be about 0.0025 inches.
It has been found that the utilization of the die assemblies, as des-
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~046859
cribed above, will allow an accurate control of the displacement of the main
section of the panel and reduce the thickness of the smallest area of the resi-
dual in the weakened area to a point that has heretofore not b~en possible.
For example, the removable section can be displaced to a point where the resi-
dual is on the order of 0.001 inches and still have a rigid connection between
the removable section and the permanent section. This is believed to be a
result of the particular configuration of the die elements which readily allows
the metal that is being displaced to flow from the weakened area rather than
be compressed and result in the stressed conditions heretofore known.
It should be noted that the final position of the removable section
relative to the permanent section, i.e., the offset, will be determined by the -~
diameter-of female die element 84 and the radius of curvature of surface 90.
It will be appreciated that the removable section will seek its own level since ~ -
it is free to move.
While the removable section has been shown to be displaced downwardly
in the "cold swedging" operation in certain instances it may be desired to dis-
place the removable section 14 upwardly during the formation of the frangible
connection. By changing the figuration of the respective die elements, the
removable section can be displaced upwardly by the same amount as is shown in ~
Figure 5, and then the panel could be expanded by engaging the radiused por- --
tion of the flange portion of the rim outwardly to expand or stretch the panel
and result in the same final configuration of the panel that is shown in Figure
6J except that the removable section would be displaced upwardly by the pre-
determined amount shown in Figure 6. This arrangement would have the advantage
of completely eliminating any possibility of overlap between the severed edges
of the weakened area during the pulling phase of removal of the removable sec- -
tion.
It should be noted that when the end panel 10 is attached to the main
body of the container by the double seam process, the panel, more particularly,
the base portion thereof, ~ill be further expanded to increase the tension of
1046859
the metal in the removable section.
In the final configuration, a plane p extending through the minimum
cross-section area or residual of the frangible connection 18 will define an
angle of substantially 90 with respect to the plane that extends through the
main body of panel portion 14. This further insures that the severed edge of
the residual in the removable section will be able to move above the adjacent
severed edge on the permanent section 16 during the rupture of the weakened
area.
All of the excess metal in the removable section can be removed in
the sizing operation to eliminate any compressive forces in removable section
14 by proper selection of angles (a) and (b) in Figures 3 and 4, so that the
removable section assumes the position shown in solid line in Figure 9. How-
ever, in forming end 10, shown in Figure 1, only a portion of the excess metal
in the removable section is removed during the sizing operation. For example,
flange 39 initially defines an angle ~a) of approximately 15 and the final
angle (b) in Figure 4 is approximately 4. This will take up some excess metal
in removable section 14 and change the dished configuration of removable section
14 from the position shown in Figure 8 to the dotted line position of Figure 9.
The remainder of the excess metal will be removed during the profiling step
that will now be described.
After the panel 12 has been reshaped as described above, further die
elements are utilized to deform the removable section 14 and produce the por-
tions of beads 20 and 34 as well as a trough 32 and the dished portion 36.
Beads 20 and trough 32 produce means for preventing crowning of the
removable section of the panel between opposite points during the severing of
frangible connection or weakened area 18. The formation of bead 20 and trough
32 as well as bead 34 and dished portion 36 will take up the remainder of the
excess metal in the removable section during the deforming of the panel into the
final configuration shown in Figure 2.
According to a further aspect of the present invention, a hinge is
1046859
formed in the removable section of the panel for allowing the tab connected
to the rivet to be pivoted and cause the nose portion of the tab to initiate
the rupture of the weakened area between the rivet and the adjacent rim. It
has been found that some type of hinge connection adjacent the rivet is neces-
sary to allow the handle or lever to be pivoted during the initial rupture of
the weakened area to produce the initial rupture in the frangible connection.
It has been found to be advantageous to utilize a "cold swedging" technique
similar to the "cold swedging" technique in producing the frangible connection
18 in an area adjacent the rivet but on a side opposite that of the weakened
area. This will cause the metal to be displaced or flow into the panel
adjacent the rivet and the excess metal will allow the lever or pull tab to
be pivoted sufficiently during the first phase of removing the removable
section and produce the initial rupture of the wea~ened area. A further
advantage of the area of reduced cross-section adjacent the rivet is that
reducing the residual left in the area of reduced cross-section will insure `~
that the reduced area is severed during the initial pivotal movement of the
lever so that this area acts as a vent to equalize the pressures between the
inside of the container and the surrounding atmosphere before the weakened
area 18 is initially ruptured. The details of this aspect of the invention
are shown in Figures 10 to 12.
Before the "cold swedging" operation described above in connection
with Figure 5, the rivet 28 has previously been formed in the removable
section of the panel through a multiple stage process that is well-known in
the art. In order to produce the area of reduced cross-section or "smile"
in a selected area surrounding the rivet 28, the wall defining an opening 100
in female die element 50 has an arcuate surface 102 that interconnects the
wall of opening 100 with the upper surface 64 of die element 50, while the
remainder of the upper surface of the die element has a cutout portion 106
in the area of rivet 28. The male die element 54 has an annular member 100
that has an inner diameter opening equal to the outer diameter of the rivet
t
- 13 -
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.' .' '' ',' ' ' ~ ',,.:.' .. , , '
1046859
28 with the portion of the annular member 110 that is opposed to arcuate sur-
face 102 also having an arcuate surface 112.
Thus, during relative movement of die elements 50 and 54, towards
each other, the metal in the panel located between the opposed arcuate sur-
faces 102, 112 is "cold swedged" to produce an area of reduced cross-section
120 shown in Figure 11. The metal that is displaced to produce the area of
reduced cross-section flows into the adjacent portion of the removable section
14 to result in excess metal being located adjacent the reduced cross-section
area. This excess metal will allow the rivet having the tab connected thereto
to be pivoted with respect to removable section 14. The excess metal that is
developed during the "cold swedging" operation to produce the area of reduced
cross-section 120 will allow sufficient pivotal movement of the tab to produce
the initial rupture of the weakened area or frangible connection 18 at a
location adjacent the rivet.
If desired, the area of reduced cross-section can perform the
additional function of providing a vent that will allow equalization of the
pressures on opposite sides of removable section 14 before weakened area 18
is ruptured. This can be accomplished by reducing the residual in the
area of reduced cross-section 120 to a point where the reduced area or resid-
ual 120 will be ruptured before the weakened area 18 is initially ruptured.
According to another aspect of the invention, the particular
dimension of the area of reduced cross-section has been found to be critical.
It has been found that if the area of reduced cross-section, in plan view as
viewed in Figure 12, is arcuate and defines an arc of less than 90, suffi-
cient metal will be deformed from the area of reduced cross-section into the
adjacent portion of the panel to allow the rivet to be pivoted relative to
the panel sufficiently to produce the initial fracture of the weakened area
and, if the area of reduced cross-section is made thin enough, this area will
also rupture for this pivotal movement to provide pivot action.
As most clearly shown in ~igure 12, the area of reduced cross-
10468S9
section 120 circumscribes an arc of approximately 75 and the arc has its
radius coincident with the center of rivet 28. Stated in another way, the
linear dimension between opposite ends of the area of reduced cross-section ~ :
is substantially equal to the diameter of the rivet 28. -
In the above description, the die elements utilized for the "cold
swedging" step and the sizing step were considered to be two separate sets of
die elements. However, it will be appreciated that a single set of die
elements having relatively movable parts could readily be used. For example,
female die elements 50 and 80 could be one die element in which a portion
having arcuate surface 62 could be lowered after the panel is deformed to the
configuration of Figure 5.
15 ~
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