Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a container having a
portion of its wall weakened to serve as a tear strip
and having a tab attached to the tear strip to serve
as a lever for initiating the severing operation.
In general, the invention is directed to two
problems which have come to the fore with widespread
acceptance of this type of container. One problem is
to make it easier to lift the tab to initiate severance
of the tear strip. The second problem is to prevent
the unintentional fracturing of the opening score line
which may occur as the result of mishandling of the
container.
It is, therefore, one of the primary objects of
the present invention to provide an improved pull tab
mounting arrangement which will facilitate the opening
of a self-opening container. This is accomplished by
increasing the leverage afforded by the pull tab. More
specifically, the tab is mounted such that lifting of the
tab causes the fulcrum point to be displaced toward the
nose portion and away from the finger ring portion, thereby
providing the user an increase in mechanical advantage.
It is a further object of this invention to provide
an improved pull tab mounting arrangement which will reduce
the probability that mishandling of the container will
result in unintentional fracturing of the opening score
line. This is accomplished by mounting the tab such that
its nose portion is maintained in spaced relation with the
score line, thereby preventing minor displacements of the
tab from resulting in a score line fracture.
It is another object of this invention to provide
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an improved pull tab mounting arrangement which will permit
the use of thinner gauge metal in the fabrication of the
pull tab and end panel. This is accomplished by mounting
the pull tab so as to reduce the stress placed on these
memhers during opening. Specifically, the stress on the
end panel in the region immediately adjacent to the rivet
is reduced by the use of an expandable bellow which allows
controlled distortion of the metal in this area.
According to the present invention, there is pro-
vided an improved pull tab mounting arrangement for a self-
opening end closure for a can or similar container. The end
closure comprises an end panel, attachment means formed in
said end panel, a pull tab attached by said attachment
means to said end panel, and a score line formed in said ~
end panel and defining an opening flap therein. The improve- ~;
ment comprises unfoldable means for shiftably mounting said
attachment means in said end panel for relieving stresses
on said pull tab and said end panel during lifting move-
ments of said tab for opening of said container.
In drawings which illustrate one embodiment of the
present invention:
Figure 1 is a cross-sectional view of an end
closure with the improved tab mounting arrangement,
illustrating the unopened condition.
Figure 2 is a cross-sectional view similar to
Figure 1, illustrating the partially opened condition.
Figure 3 is a cross-sectional view of a conventional
end closure.
Figure 4 is a cross-sectional view similar to
Figure 3, illustrating distortion due to opening stresses.
In keeping with the present invention, there is
provided an easy-open end closure comprising a m0tal end
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panel 1, a rivet 2 integrally formed in said end panel and a
metal pull tab 3 fixedly attached to said end panel 1 by said
rivet 2. A score line 4 is formed in the end panel 1 and
defines an opening flap 5 therein.
In the standard easy-open closure (Figure 3), which
lacks a pleat 6, opening is accomplished by vertically
displacing the tab 3, thereby pivoting said tab 3 about said
rivet 1 and imposing a downward force on the tab nose portion
3a, said force resulting in the breaking of said end panel
1 along said score line 4 beneath said nose portion 3a.
Continued upward displacement of said tab 3 results in
controlled tearing of said end panel 1 along said score line
4, the opening flap 5 defined by said score 4 being bent
down and away from said end panel 1, thereby establishing
an opening in said end panel 1.
The fulcrum point 7 of the conventional easy-open
closure is located on the interface between the tab 3 and the
rivet head 2a at the point furthest between the tab 3 and the
3a. As the tab finger ring portion 3b is lifted, an upward
force is impressed on the rivet 2 and the end panel 1 in the
area immediately adjacent to the fulcrum point 7. This
stressing of the end panel 1 and the rivet 2 necessitates
the use of a thickness of metal with sufficient strength and
rigidity to resist deformation or tearing during opening of
the container. Further, this configuration minimizes the
length of the lever arm and maximizes the length of the load
arm and, consequently, places the maximum stress on the tab 3.
This necessitates the use of a thickness of metal for the
tab 3 which will resist bending during opening of the
container. The inefficient lever arrangement also results '~
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in the requirement o~ considerable ef-fort to lift the
tab 3 su~ficiently far to effect fracture of the score
line 4. ~ -
In the improved tab mounting arrangement of the
present invention (Figure 1) an expandable pleat 6 is formed
in the end panel 1 concentric with and immediately adjacent
to the rivet 2. The pleat 6 comprises two substantially .
parallel, concentric sidewalls 6a depending from the end
panel 1 and a connecting U-shaped bight portion 6b. The tab
nose portion 3a is held in spaced relation above and radially
inward of the score line 4, rather than in close contact with - ;
the score line as in the standard end closure. -
As the finger ring portion 3b is lifted, the pleat
6 unfolds everting outwardly with the unfolded sidewalls
6a projecting above the plane of the end panel 1 and causing -
displacement of the fulcrum point 7 radially outwardly
upwardly toward the score line 4 (Figure 2), thereby bringing
the nose portion 3a into close contact with the score line
4. After the pleat 6 has unfolded, the end closure is opened ;
in the conventional manner as described hereinabove. How- ;
ever, the fulcrum displacement has resulted in an increase
in the length of the load arm which in turn results in a
decrease in the stress loading on the tab 3 during opening
of the container. Further, the effort required to open
the container has been reduced.
The expansion of the pleat 6 also serves to
relieve the stresses on the rivet 2 and the end panel 1
by allowing controlled distortion thereof. These stress
reductions allow the fabrication of the tab 3 and the end
panel 1 from a thinner gauge metal.
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The improved pull tab mounting arrangement also
serves to reduce the probability that mishandling of the
container will result in an unintentional fracture of the
score line 4. In the conventional pull tab mounting
arrangement (Figure 3), the nose portion 3a rests in close
contact with the score line 4, such that an accidental
impact against the nose portion 3a may well result in an
unintended fracture of the score 4. In the improved pull
tab mounting (Figure 1), the nose portion 3a is held in
spaced relation above and radially inward of the score
line 4, such that an accidental impact against the nose
portion 3a will result in the nose portion 3a being forced ~.
downward into contact with the end panel 1, leaving the
score 4 unaffected. Further, such an accidental displacement
of the tab 3 will not interfere with the subsequent opening
of the container.
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