WO2000056613A1

WO2000056613A1 - Vented container end apparatus and method

Info

Publication number: WO2000056613A1
Application number: PCT/US1999/006352
Authority: WO
Inventors: Howard Curtis Chasteen
Original assignee: Ball Corporation
Priority date: 1999-03-23
Filing date: 1999-03-23
Publication date: 2000-09-28
Also published as: MXPA01009647A; IL145660A0; AU763533B2; AU3112299A; CA2365769A1; BR9917316A; EP1210273A4; WO2000056613A8; EP1210273A2

Abstract

A container end is provided so that upon opening, a generally triangular vent region (362) is formed with an apex pointing rearwardly toward the head space to vent the container during pouring. The container end achieves a fast and smooth pour with a relatively small increase in the opening area (322) without increased bursting, buckling or opening failures associated with relatively larger openings. The opening area is defined by a score line (318) having first (342) and second (346) rupture end points with a gate axis (348) therebetween along which the opening area (322) pivots after rupture of the score line (318).

Description

VENTED CONTAINER END APPARATUS AND METHOD

The present invention relates to a container end which provides venting during emptying of contents and, in particular, a container with an end having a score defining a vent area providing good pouring characteristics without undue increase in the opening's size.

BACKGROUND INFORMATION A number of containers are configured to achieve easy opening, such as without the need for a can opener or other tool and preferably which does not involve separation of any parts (so that there is no separate tab or cover piece to dispose of) . A number of features of such containers and container ends affect the level to which end users, as well as bottlers, manufacturers, distributors, shippers and retailers, are satisfied with the container. One factor believed to be of some importance to consumers is the pour characteristics of the container. In general, it is believed that consumers prefer to use containers capable of providing a relatively high pour rate, such as pouring about 350 ml in less than about 10 seconds, preferably less than about 8 seconds, and more preferably less than about 7 seconds (e.g., measured using pour rate testing as described below) . Additionally, it is believed consumers prefer containers that provide a smooth or substantially laminar pour, i.e. a pour which is not characterized by a series of surges (which can cause splashing and/or can affect a beverage head, fizz or other carbonation or pressurization-related characteristics of the contents, after pouring) . Certain previous containers have been configured in an attempt to address these concerns by providing relatively large openings, e.g. openings covering greater than about 0.5 square inches (about 3.2 cm²). Unfortunately, such larger openings tend to be associated with a higher rate of problems such as bursting, buckling, leakage, opening failures and the like, particularly when the contents are pressurized, such as being provided with an over-pressure of about 35 psi (about 250 kPa) or more. Furthermore, such larger openings are difficult or infeasible to provide in container ends which are relatively small, such as round container ends having a diameter of less than about 2 inches (about 5 cm) . Furthermore, certain previous approaches to improving pouring characteristics have involved major changes to the design of the container end, thus involving relatively high tooling or other equipment costs, design costs, testing costs and the like.

Accordingly, it would be useful to provide a container or container end with improved pouring characteristics while retaining a relatively small opening area, which is preferably compatible with relatively small-sized container ends, and which can be achieved with only modest changes in tooling, procedures and/or testing.

SUMMARY OF THE INVENTION The present invention relates to a container and container end of a type where an opening area is at least partially defined by a score line. First and second endpoints of the score line are spaced apart along the score line, and the opening area is bent inward, following rupture (e.g. via a tab pivoted about a rivet, along an opening axis) . The pivot point defined by the rivet is generally at about the center or centroid of the container end. The spaced-apart ends of the rupture define an opening or "gate" axis about which the bent-in region bends or pivots. The present invention involves configuring the score line so that the area which is bent-in provides an opening which defines not only a pouring region but also a vent region. In one embodiment the vent region is shaped

(substantially triangular) with an edge of the vent region defined by the gate region. The vent region has an apex pointing generally away from the pour area. The end points of the rupture score line (which define the gate axis therebetween) are both positioned on the same side of the tab's pivot point with one of the end points positioned farther away from the pour area than the other and thus defining the apex of the vent area. The end point which defines the apex is the end point which is farthest from the pivot point, and is also farthest from the opening axis and from a second axis (through the pivot point) perpendicular to the opening axis. The present invention provides a desirably fast, smooth pour while maintaining a relatively small total opening area (pour opening plus vent opening) and otherwise avoiding undesirable bursting, buckling and opening failures.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a top plan view of a container according to previous devices;

Fig. 2 is a top plan view of a score and tab rivet region according to previous devices;

Fig. 3 is a top plan view of a score and tab rivet region according to an embodiment of the present invention;

Fig. 4 is a top plan view similar to that of Fig. 3 but showing the opening region according to an embodiment of the present invention compared to that of previous devices;

Fig. 5 is a top plan view similar to the view of Fig. 3 but showing inclusion of a reinforcing bead; and

Fig. 6 is a cross-sectional view taken along line 6-6 of Fig. 5;

Fig. 7 is an elevational view, partly in cross- section, showing pouring contents of a container, according to an embodiment of the present invention; Fig. 8 is a top plan view similar to the view of Fig. 5, but showing an alternate reinforcing shape;

Fig. 9 is a cross-sectional view taken along line 9-9 of Fig 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although the present invention can be used in connection with a number of container configurations, one particular prior container configuration is shown, in top view, in Fig. 1. In the container of Fig. 1, a container body 112 is provided with a necked region 114 leading to a body end which is covered, in the depicted embodiment,- with a container end 116. Manners of forming container bodies and container ends and of attaching or coupling the two, to form the depicted device, are well known in the art. The container end 116 includes a score line 118

(described more thoroughly below) commonly formed by stamping with a die or "knife" to define an opening area 122. A tab 124 is coupled to the can end 116 e.g. by a rivet 126 whose center 128 defines a pivot point 132. Generally, pulling the upper edge 134 of the tab 124 up and towards the opening region 122, (defining an opening axis 132) results in the forward edge 136 of the tab 124 pressing downward on part of the opening area 122 with sufficient force to cause a rupture to form along the score line 118, permitting the opening area 122 to bend or pivot inward about a gate axis (described below) . Once the opening region 122 of the top 116 has been thus pivoted inward, the can end 116 has an opening whose perimeter is defined by the score line 118 and the gate axis. As seen in Fig. 2 (depicting a configuration without a tab 124 in place, for better illustration) , the score 118 along which the rupture occurs has first and second rupture end points 242, 246 and the imaginary line 248 connecting the rupture end points defines the gate axis about which the opening region 122 of the can end bends or pivots inward to form the opening. In the depicted configuration, a second inward score line 252 is positioned substantially parallel with the rupture score line 118. The interior score line 252 has been found useful in protecting the rupture score line 118, although no rupture occurs along the interior score line 252 in normal operation. In the configuration depicted in Fig. 2, a clearance element 254 is positioned between the outer and inner score lines in a region near the tab rivet 126.

Several characteristics of the previous configuration shown in Fig. 2 are useful to note in connection with explaining the present invention described below. The total open area after the opening region 122 is bent inward is defined by the score line 118 plus the gate axis 248 and, in at least some previous devices, this opening region had an area of 0.451 square inches (about 2.9 cm²) . In the configuration depicted in Fig. 2, the gate axis 248 is substantially parallel to a second or pivot axis 258 which is perpendicular to the opening axis 132 passing through the pivot point 128. The entire portion of the opening region 122 is forward of the pivot point 128, i.e. is spaced from, and all on one side of, the second axis 258.

For purposes of description, the portion of the can top lying on one side of the second axis 258 (which, in Fig. 2, contains the opening region 122) will be referred to, in the following, as the forward region 264, and the portion on the opposite side of the second axis 258 will be referred to as the rearward portion 266, thus defining a forward direction 268 and a rearward direction 272, both generally parallel to the opening axis 132.

Fig. 3 illustrates a configuration of a score line according to an embodiment of the present invention and depicts how it differs from the previous score line of Fig. 2 (shown in phantom lines in Fig. 3) . In the embodiment of Fig. 3, the score line 318 provides first and second rupture end points 342, 346 positioned to define a generally triangular vent region 362. The line 348 between the rupture end points 342, 346 defines the gate axis for the embodiment of Fig. 3, along which the opening region 322 bends or pivots following rupture along the rupture score line 318.

In the embodiment of Fig. 3, the second end point 346 defines an apex 372 of the triangular vent region 362. As shown, the apex 372 of the triangular region 362 points rearwardly 272 (with respect to the second axis 258) . The gate region 348 is non-parallel to the second axis 258 and forms an angle 382 therewith (measured in a direction from the second axis 258 toward the gate axis 348 and generally in a direction toward the pivot point 128) which is less than 90° preferably about 45°. The configuration with the gate axis (considered in a direction towards the apex) angled away from the opening axis 132 is believed to provide good pour characteristics without unduly affecting opening characteristics. The second end point 346 (and, preferably, the first end point 342, as well) is positioned on the opposite side of the second axis 258 from the major portion of the opening area 322, i.e. is positioned rearward 272 of the pivot point 128. Thus, during pouring, the triangular region 362 will generally point towards (and provide venting to) the headspace of the container (i.e. the portion above the contents being poured) . In the depicted embodiment both the first end point 342 and the second end point 346 lie on the same side (in the orientation and configuration depicted in Fig. 3, the right side) of the opening axis 132. The front-rear distance (i.e. a distance generally parallel to the opening axis 32) of the second end point 384 from the second axis 258 is greater than the front-rear distance 386 of the first end point 342 from the second axis 258. The second end point 346 is also farther from the pivot point 128 than the first rupture end point 342. Although positioning the apex 372 as far rearward as possible is believed to, in general, facilitate venting, it is believed that positioning significantly more rearwardly than described and depicted herein may lead to undesired upward displacement of the rivet region and/or opening failure. Preferably the distance 384 is between about 0.1 inches (about 2.5 mm) and about 0.5 inches (about 1.2 cm). In one embodiment, distance 384 is about 0.3 inches (about 8 mm) .

In one embodiment, the configuration depicted in Fig. 3 is provided in a container end with a generally circular perimeter as depicted in Fig. 1 and preferably attached to a container generally as depicted in Fig. 1. In this configuration, the second end point 372 is closer to the perimeter of the container end 137 (Fig. 1) than the first rupture end point 342.

Fig. 4 depicts the outline of the opening 412 resulting after the opening region 372 has been bent inward about the gate axis 348. The contour or perimeter of an opening according to previous devices (such as that depicted in Fig. 2) is shown, in Fig. 4, in phantom lines 414 illustrating how it differs from a score line contour 412 according to the present invention. The total area of the opening 416 in the embodiment depicted in Fig. 4 is only slightly larger than the area of the opening resulting from the configuration of Fig. 2 and is preferably less than 0.7 square inches (about 4.5 cm²), more preferably less than 0.6 square inches (3.8 cm²), even more preferably less than about 0.5 square inches (about 3.2 cm², such as being about 0.4892 square inches (about 3.156 cm²).

Fig. 5 shows an embodiment similar to the embodiment of Fig. 3 but with a stiffening or reinforcing bead 512 provided for adding stiffness to the hinge area, helping it to open completely and helping to prevent a tear across the vent area during opening. Although stiffening in this region can take a number of forms, in the depicted embodiment the generally elongated bead 512 extends from a first end 514 substantially adjacent the gate axis 348 and extending forward, across the second axis 258 to a second end 516. In the depicted embodiment, the bead 512 has a cross-sectional configuration as depicted in Fig. 6. As shown in Fig. 6, the bead 512 provides inner and outer ramped or sloped surfaces 612, 614 and a central flat region 616. The cross-sectional view of Fig. 6 also shows the location of score line 318 and inner score line 352.

Fig. 8 shows an embodiment similar to the embodiment of Fig. 5 but with a generally triangular-shaped stiffening or reinforcing region 812 provided for adding stiffness to the hinge area, helping it to open completely and helping to prevent a tear across the vent area during opening. In the embodiment depicted in Fig. 8, the reinforcing region 812 has less of a tendency to bend or tear, compared to the bead 512 of Fig. 5. The reinforcing area 812 extends from a first generally rounded apex 814 substantially adjacent the gate axis 348 and extending forward, across the second axis 258 to a second end 816 extending between second and third generally rounded apices 818a, b of the generally triangular region 812. In the depicted embodiment, the triangular region 812 has a cross-sectional configuration as depicted in Fig. 9. As shown in Fig. 9, the region 812 provides inner and outer ramped or sloped surfaces 922a,b and a central flat region 924. The cross-sectional view of Fig. 9 also shows the location of score line 318.

In practice, a can end is formed by providing a generally flat blank according to procedures well known in the art. A die is used to stamp the can end providing a score line configured as depicted in Figs. 3-6 and, preferably, other features such as reinforcing beads or other reinforcements and the like. A tab is coupled to the can end generally as provided in previous procedures well known to those of skill in the art. A can end thus formed is coupled to a container body, formed according to procedures known to those of skill in the art, to provide a completed and preferably filled container.

In one embodiment, producing container ends in the manner and form described can be achieved using materials and apparatus generally similar to that used in previous procedures for forming container ends such as those depicted in Fig. 2, but using a die or other scoring device configured to provide the score (and, preferably, reinforcing or other features) as depicted in Figs. 3-6. In this way, it is possible to implement the present invention with few changes to previous procedures and apparatus thus minimizing or reducing costs associated with retooling, procedural changes, testing and the like. Of course, if desired, it is possible to use the present invention in connection with different container or container end designs.

In use, a user will gain access to the contents of a container formed according to the present invention in a manner somewhat similar to that used in connection with previous designs, namely by grasping the rear edge of a tab and pulling it forward pivoting along the opening axis causing rupture along the rupture score and bending the opening region inwardly about the gate axis to form an opening which includes both a pour area and a vent area. Preferably the forwardmost regions of the score line are the first to rupture, and the portions defining the vent region are the last to rupture. The user will then tip the container (Fig. 7) causing the container contents to exit through the pour area of the opening under the influence of gravity while air can enter through the vent region to achieve a smooth and rapid pour. In one embodiment of the present invention, a smooth pour will be achieved at a pour rate of 350 ml in less than about 10 seconds, more preferably in less than about 8 seconds and even more preferably less than about 7 seconds, such as in about 6.8 seconds.

According to one pour testing procedure, aluminum alloy 12-oz. cans with ends generally as depicted in the figures, (of the type similar to that currently commonly used for 12-oz. beverage containers, and available from Ball Corporation under the designation 202B-64) were filled with approximately 350 ml of tap water at approximately standard temperature and pressure. Samples were held by the bottom dome of the can with a vacuum chuck. Samples were pivoted about the can's center to a positive stop at 55° from vertical whereupon a timer was started. When the fluid flow diminished sufficiently that the smooth

(laminar) flow turned rough (non-laminar) the timer was stopped. Each sample was tested 10 times and an average was taken. Times for any sample were found to vary by less than about 3/10ths of a second. When the procedure was used for containers according to previous configurations (e.g. as depicted in Fig. 1) the average time according to the above-described procedure was 9.98 seconds (about 38 ml per second) . When the procedure was used in connection with a can formed according to the present invention (e.g. as depicted in Figs. 3 and 4) pour rates were greater than 40 ml per second, and even exceeded 50 ml per second, with the average time being 6.8 seconds (about 51.5 ml per second).

As shown in Fig. 7, when the container 712 is tipped in a tip direction 714 substantially along a tip axis parallel to the opening axis 132 (which lies in the plane of Fig. 7 or parallel thereto), contents of the container 716 pour through the pour opening 322 while the container head space 718 is vented through the vent opening 362 to achieve a smooth and rapid pour. In light of the above description, a number of advantages of the present invention can be seen. The present invention provides a container which produces a smooth pour and a relatively rapid pour while avoiding certain disadvantages associated with previous approaches, such as disadvantageous bursting, buckling, leaking or opening failure. The present invention is feasible in the context of relatively small-diameter tops such as tops with a diameter less than about 2 inches (about 5 cm) . The present invention thus achieves a relatively small, efficient opening that results in a quick and smooth pour without the ill effects associated with a large opening. The present invention provides a unitary pour-vent opening with the preferably triangular vent region having an apex pointing rearward toward the head space to allow smooth entry of air to vent the container. The present invention achieves venting without requiring the production of two separate openings, without requiring the user to rotate or otherwise move the tab away from the position used for forming the pour opening, or to re-flex the tab and in which the opening is configured to achieve a tipping pour direction which is essentially along the opening axis. The present invention configures a gate or hinge axis on an angle (e.g. with respect to the second axis 258) creating an apex or point 372 which allows air to easily enter the container during pouring. The present invention achieves these benefits while making only a small increase in the size of the opening (compared to previous devices) such as an increase of about 0.0382 square inches (about 0.246 cm²), compared to depicted previous configurations.

A number of variations and modifications of the present invention can be used. Although the invention has been described in the context of an opening for a container end coupled to a conventionally formed and shaped container, the present invention can also be used in connection with a wide variety of other containers or container ends by providing an opening with a triangular vent region pointing rearwardly and generally away from the tab pivot point. The present invention has been described in connection with a container for a pressurized liquid but can be used in connection with containers containing other items such as non-pressurized liquid. Although the present invention has been described in the context of a container formed of conventional materials (such as an aluminum container) , a container according to the present invention can be formed of other materials including other metals or metal alloys, plastics, cardboard, paper, fiber reinforced materials, and the like. It is possible to use some features of the invention without using other features, such as providing a score line configured to produce a rearwardly pointing vent area without using the described and depicted reinforcing bead. Although a generally convex and stadium-shaped bead region has been depicted, other shapes and types of reinforcing can be provided such as relatively thickened or corrugated regions or regions with other materials included or added such as with a reinforcing plate coupled thereto. It is possible to provide a mirror image configuration, if desired.

Although the invention has been described by way of a preferred embodiment and certain variations and modifications, other variations and modifications can also be used, the invention being defined by the following claims:

Claims

What is claimed is:

1. A vented container end comprising: a generally flat cover region with a score defining first and second rupture endpoints, wherein at least a portion of said score extending between said first and second rupture endpoints together with a gate axis between said first and second rupture endpoints defines an opening area of said cover region; a tab coupled to said cover region so as to permit said tab to be moved about a pivot point to press against a contact region of said opening area, the pivot point and contact region generally lying along an opening axis, said pivot point defining a second axis passing through said pivot point and perpendicular to said opening axis; wherein said first and second rupture endpoints lie on the same side of said opening axis; wherein said second rupture endpoint is farther from said pivot point than said first rupture endpoint; wherein said second rupture endpoint is farther from said second axis than said first rupture endpoint so that said gate axis is at an angle with respect to said second axis .

2. A container end as claimed in claim 1 wherein said cover region has a generally circular perimeter and wherein said gate axis defines an edge of a generally triangular vent region, at least a portion of which is located on an opposite side of said second axis from said contact region, said second rupture endpoint defining an apex of said generally triangular vent region.

3. A container, as claimed in claim 2 wherein said apex is closer to said perimeter than said first rupture endpoint.

4. A container, as claimed in claim 2 wherein said apex is farther from said perimeter than said first rupture endpoint .

5. A container end as claimed in claim 1 wherein said container end has a surface area of less than about 3 in².

6. A container end as claimed in claim 2 wherein said apex is positioned at least about 0.3 inches from said second axis.

7. A container end, as claimed in claim 2 further comprising a reinforcing member formed in said vent region.

8. A container end, as claimed in claim 7, wherein said reinforcing member has a first end substantially adjacent said gate axis.

9. A container end, as claimed in claim 7, wherein said reinforcing member extends across said second axis.

10. A container end, as claimed in claim 7, wherein said reinforcing member is generally elongated in shape.

11. A container end, as claimed in claim 7, wherein said reinforcing member is generally triangular in shape.

12. A container end comprising: a generally flat cover region with a score defining first and second rupture endpoints, wherein at least a portion of said score extending between said first and second rupture endpoints, together with a gate axis between said first and second rupture endpoints defines an opening area of said cover region spaced from a pivot point for coupling an opening tab; wherein said second rupture endpoint is farther from said pivot point than said first rupture endpoint and defines an apex of a generally triangular vent region; wherein said opening area is greater than 0.451 square inches and less than about 0.5 square inches.

13. A container end, as claimed in claim 12, wherein said vent region is sufficiently large to provide a standard pour rate of at least about 40 ml per second.

14. A container end, as claimed in claim 12, wherein, when said container end is coupled to a container, said container end is capable of maintaining integrity when contents of said container are pressurized to at least about 35 psi.

15. A container comprising: a container body; a container end having a generally flat cover region with a score defining first and second rupture endpoints, wherein at least a portion of said score extending between said first and second rupture endpoints together with a gate axis between said first and second rupture endpoints defines an opening area of said cover region; a tab coupled to said cover region so as to permit said tab to be moved about a pivot point to press against a contact region of said opening area, the pivot point and contact region generally lying along an opening axis, said pivot point defining a second axis passing through said pivot point and perpendicular to said opening axis; wherein said first and second rupture endpoints lie on the same side of said opening axis; wherein said second rupture endpoint is farther from said pivot point than said first rupture endpoint; wherein said second rupture endpoint is farther from said second axis than said first rupture endpoint so that said gate axis is at an angle with respect to said second axis.

16. A container as claimed in claim 15 wherein said cover region has a generally circular perimeter and wherein said gate axis defines an edge of a generally triangular vent region, at least a portion of which is located on an opposite side of said second axis from said contact region, said second rupture endpoint defining an apex of said generally triangular vent region which is closer to said perimeter than said first rupture endpoint.

17. A container as claimed in claim 15 wherein said container end has a surface area of less than about 3 in².

18. A container as claimed in claim 15 wherein said apex is positioned about 0.3 inches from said second axis.

19. A container, as claimed in claim 15 further comprising a reinforcing bead formed in said vent region.

20. A container, as claimed in claim 19, wherein said bead has a first end substantially adjacent said gate axis.

21. A container, as claimed in claim 19 wherein said bead extends across said second axis.

22. A container comprising: a container body; a container end, coupled to said container body, having a generally flat cover region with a score defining first and second rupture endpoints, wherein at least a portion of said score extending between said first and second rupture endpoints, together with a gate axis between said first and second rupture endpoints defines an opening area of said cover region spaced from a pivot point for coupling an opening tab; wherein said second rupture endpoint is farther from said pivot point than said first rupture endpoint and defines an apex of a generally triangular vent region; wherein said opening area is greater than 0.451 square inches and less than about 0.5 square inches.

23. A container, as claimed in claim 22, wherein, said container end, when coupled to a container, provides a vent region sufficiently large to provide a standard pour rate of at least about 40 ml per second.

24. A container, as claimed in claim 22, wherein said container end, when coupled to a container, is capable of retaining integrity when contents of said container are pressurized to at least about 35 psi.

25. A container end comprising: generally flat cover region with score means defining first and second rupture endpoints, wherein at least a portion of said score means extending between said first and second rupture endpoints for defining, together with a gate axis between said first and second rupture endpoints, an opening area of said cover region; tab means coupled to said cover region so as to permit said tab means to be moved about a pivot point, said tab means for pressing against a contact region of said opening area, the pivot point and contact region generally lying along an opening axis, said pivot point defining a second axis passing through said pivot point and perpendicular to said opening axis; wherein said first and second rupture endpoints lie on the same side of said opening axis; wherein said second rupture endpoint is farther from said pivot point than said first rupture endpoint; wherein said second rupture endpoint is farther from said second axis than said first rupture endpoint so that said gate axis is at an angle with respect to said second axis .

26. A container end comprising: a generally flat cover region with score defining first and second rupture endpoints, wherein at least a portion of said score extending between said first and second rupture endpoints, said score means, together with a gate axis between said first and second rupture endpoints, for defining an opening area of said cover region, spaced from a pivot point for coupling an opening tab; wherein said second rupture endpoint is farther from said pivot point than said first rupture endpoint and defines an apex of a generally triangular vent region; wherein said opening area is greater than 0.451 square inches and less than about 0.5 square inches.

27. A method for forming a container end comprising: providing a generally flat cover region; forming a score on said generally flat cover region, defining first and second rupture endpoints, wherein at least a portion of said score means extending between said first and second rupture endpoints, together with a gate axis between said first and second rupture endpoints, define an opening area of said cover region; coupling a tab to said cover region so as to permit said tab means to be moved about a pivot point to press against a contact region of said opening area, the pivot point and contact region generally lying along an opening axis, said pivot point defining a second axis passing through said pivot point and perpendicular to said opening axis; wherein said first and second rupture endpoints lie on the same side of said opening axis; wherein said second rupture endpoint is farther from said pivot point than said first rupture endpoint; wherein said second rupture endpoint is farther from said second axis than said first rupture endpoint so that said gate axis is at an angle with respect to said second axis.

28. A method for forming a container comprising: providing a generally flat cover region; forming a score on said generally flat cover region defining first and second rupture endpoints, wherein at least a portion of said score extending between said first and second rupture endpoints, together with a gate axis between said first and second rupture endpoints, define an opening area of said cover region spaced from a pivot point for coupling an opening tab, wherein said opening area is greater than 0.451 square inches and less than about 0.5 square inches; wherein said second rupture endpoint is farther from said pivot point than said first rupture endpoint and defines an apex of a generally triangular vent region; and coupling said cover region to an open end of a container body.