Sheet metal container making – Apparatus to form container closure – Having means to apply seal or liner
Reexamination Certificate
2002-04-26
2004-02-03
Hong, William (Department: 3725)
Sheet metal container making
Apparatus to form container closure
Having means to apply seal or liner
C413S014000, C413S017000, C413S066000, C413S067000, C413S068000
Reexamination Certificate
active
06685417
ABSTRACT:
FIELD OF THE INVENTION
The current invention is directed to a safe ended type end for a container. More specifically, the current invention is directed to an end for a container having improved opening characteristics.
BACKGROUND OF THE INVENTION
Many products, such as food stuffs, including potato chips, as well as other articles, such as tennis balls, are packaged in containers having an easy open end
2
, such as that shown in
FIGS. 1-3
. Conventionally, such ends are formed from metal plate, such as aluminum, having a thickness t of about 0.0095 inch (0.24 mm). Such ends have a circular score line formed between the central panel
8
and the rim
10
. The rim
10
has a curl
17
formed thereon for attachment to the side wall of the container. A tab
4
, attached by a rivet
5
to the central panel
8
, is employed to effect opening. By pulling up on the end
7
of the tab
4
, the nose
6
of the tab presses against the rim and causes the score line
12
to shear, thereby separating the central panel
8
, which is discarded, from the rim
10
. The minimum pulling force exerted on end of the tab
4
that is required to cause the initial shearing of the score line
12
is referred to as the “pop value.” After initial shearing, continued manipulation of the tab allows the user to completely sever the central panel from the rim portion by shearing the score line along its entire circumference. The force necessary to continue the shearing of the score line after the initial severing is referred to as the tear force. The lower the pop value and the tear force, the easier it is for the user to open the container.
The opening operation described above can result in a sharp edge being formed on the rim
8
, which can result in a cutting hazard to the user. This rim edge can be made safe by folding under a portion of the rim
10
adjacent the score line
12
inwardly and then outwardly so as to form an upper fold
16
and a lower fold
14
, with the bend
18
of the lower fold projecting radially inward beyond the score line
12
so as to protect the user from the sharp edge formed on the rim when it is severed along the score line, as shown in
FIGS. 1-3
.
The opening process also results in a sharp edge on the central panel. This central panel edge can be made safe by folding under a portion of the cental panel adjacent the score line
112
outwardly and then inwardly so as to form an upper fold
121
and a lower fold
117
, with the bend of the lower fold projecting radially outward beyond the score line
112
so as to protect the user from the sharp edge formed on the central panel when it is severed along the score line, as shown in FIG.
4
. In this type of can end, folds
115
and
123
are also formed in the rim portion
110
, as discussed above. However, in this case, the rim folds are located above the score line, rather than below it. A can end having a folds in both the rim and the central panel is more fully disclosed in U.S. Pat. No. 3,986,632 (Morrison et al.), hereby incorporated by reference in its entirety.
Conventionally, the folds are tightly formed. For example, an easy open end made by the assignee of the current invention is made from metal plate having a thickness t of about 0.0095 inch (0.24 mm). As shown in
FIG. 3
, the vertical gap G
1
, by which the upper surface of the bend
18
of the lower fold
14
is displaced below the lower surface of the rim
10
, has a width W
1
in the vicinity of the score line
12
that is typically less than the thickness t of the plate and may often be less than one-half the thickness t of the plate and is sometimes even zero, so that the upper surface of the bend
18
contacts the lower surface of the rim portion
20
. The width W
2
of the vertical gap G
2
, by which the lower surface of the bend
19
in the upper fold
16
is displaced above the upper surface of the lower portion of the rim
10
, is typically approximately equal to one or two times the thickness t of the plate. The overall height H of the folds
14
and
16
is typically no more than about six times the thickness t of the plate.
Unfortunately, the tightness of the folds can undesirably increase the difficulty of initially shearing the score line
12
—that is, increase the pop value. As shown in
FIG. 3
the width W
1
of the gap G
1
is minimal. Consequently, in order for the nose
6
of the tab
4
to create sufficient downward deflection in the upper portion
20
of the rim
10
to shear the score line
12
, it must apply sufficient force F to also downwardly deflect the underlying bend
18
in the lower fold
14
. This situation, which is sometimes referred to as “lockout”, increases the pop value.
The tightness of the folds can also increase the tear force, especially in ends that have folds on both the central panel and the rim panel. In such ends, further manipulation of the tab
5
and tearing of the score around its circumference after the initial pop causes the central panel
8
to bend along line A—A shown in FIG.
1
. As shown in
FIG. 4
, this deformation causes the periphery of the central panel to locally bow at locations B, which are typically at approximately the 10:30 o'clock and 1:30 o'clock locations. This bowing causes the severed edge
109
of the central panel
108
to contact the bend in the rim fold
115
above it so that additional force must be applied to the tab
104
in order to effect continued shearing of the score line
112
, thereby increasing the required tearing force.
Although easy open ends can be made, and have been made, with uniformly large gaps around the entire circumference of the fold, such as that disclosed in U.S. Pat. No. 5,105,977 (Taniuchi), such an arrangement can compromise the safety afforded by the fold if the upper portion
20
of the rim
10
does not spring completely down against the underlying fold after the central panel
8
has been removed.
Consequently, it would be desirable to create a easy open container end that is safe and yet is also easy to open.
SUMMARY OF THE INVENTION
It is an object of the current invention to provide an easy open safety container end with improved opening characteristics. This and other objects is accomplished in an easy open safety container end comprising (i) a central portion, (ii) a rim portion surrounding the central portion, the rim and central portions having a thickness and separated by a score line, (iii) means for applying a force to a portion of the end proximate the score line, and (iv) first and second circumferentially extending folds formed in the end adjacent the score line. The first fold is displaced from a portion of the end proximate the score line by a circumferentially extending gap, with a first circumferentially extending portion of the gap being less than the thickness and a second circumferentially extending portion of the gap being greater than the thickness. In a preferred embodiment of the invention, the second portion of the gap is greater than twice the thickness and encompasses an angle between about 2° and 45°. The first portion of the gap is less than one half the thickness.
The current invention also encompasses an apparatus for forming an easy open container end, comprising upper and lower forming tools having opposing forming surfaces for forming a circumferentially extending fold in the container end, a first recess formed in at least one of the opposing forming surfaces, at least one of the forming tools movable toward the other of the forming tools whereby the recessed portion of the forming surface forms a first circumferentially extending portion of the fold and the remaining portion of the forming surface forms a second circumferentially extending portion of the fold, the first portion of the fold being looser than the second portion of the fold.
REFERENCES:
patent: 3838788 (1974-10-01), Stargell
patent: 3891117 (1975-06-01), Dragomier et al.
patent: 3939787 (1976-02-01), Morrison
patent: 3941277 (1976-03-01), McKinney et al.
patent: 3945334 (1976-03-01), Ostrem et al.
patent: 3980201 (1976-09-01), Keiji
paten
Heinicke Paul R.
Kirk William A.
Crown Cork & Seal Technologies Corporation
Hong William
Woodcock & Washburn LLP
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