The present invention relates to end closures for two-piece beer and beverage metal containers having a non-detachable operating panel. More specifically, the present invention relates to improved forming techniques to produce a lightweight end closure.
Common end closures for beer and beverage containers have a central panel that has a frangible panel (sometimes called a “tear panel,” “opening panel,” or “pour panel”) defined by a score formed on the outer surface, the “consumer side,” of the end closure. Popular “ecology” can ends are designed to provide a way of opening the end by fracturing the scored metal of the panel, while not allowing separation of any parts of the end. For example, the most common such beverage container end has a tear panel that is retained to the end by a non-scored hinge region joining the tear panel to the reminder of the end, with a rivet to attach a leverage tab provided for opening the tear panel. This type of container end, typically called a “stay-on-tab” (“SOT”) end has a tear panel that is defined by an incomplete circular-shaped score, with the non-scored segment serving as the retaining fragment of metal at the hinge-line of the displacement of the tear panel.
The container is typically a drawn and ironed metal can, usually constructed from a thin plate of aluminum. End closures for such containers are also typically constructed from a cut-edge of thin plate of aluminum or steel, formed into a blank end, and manufactured into a finished end by a process often referred to as end conversion. These ends are formed in the process of first forming a cut-edge of thin metal, forming a blank end from the cut-edge, and converting the blank into an end closure which may be seamed onto a container. Although not presently a popular alternative, such containers and/or ends may be constructed of plastic material, with similar construction of non-detachable parts provided for openability.
These types of “stay-on-tab” ecology container ends have been used for many years, with a retained tab and a tear panel of various different shapes and sizes. Throughout the use of such ends, manufacturers have sought to save the expense of the metal by down-gauging the metal of the ends and the tabs. However, because ends are used for containers with pressurized contents and are sometimes subject to pasteurization, there are conditions causing great stresses to the components of the end during pasteurization, transit and during opening by a user. These conditions limit the available gauge reduction of the end metal, and make it difficult to alter design characteristics of the end, such as by reducing metal gauge or the thickness of the metal residual in the score defiling the tear panel.
The pressurized contents of the container often causes the end to buckle. The pressurized contents will also force the tabs upwardly. There is a maximum allowable distance that the tab can be displaced without the tab extending upwardly above the remainder of the container. This is called tab-over-chime. Tab-over-chime leads to ship abuse problems wherein the frangible panel prematurely fractures during distribution of filled beverage containers.
As manufacturers reduce the thickness of the metal used to make the ends, buckle and tab-over-chime become more and more of a problem. Therefore, a need for can end with improved ability to withstand buckle and tab-over-chime is needed.
It is an object of the present invention to provide an end closure for a container having a circumferential sidewall and a peripheral seaming edge adapted to be integrally connected to the sidewall. The end has a central panel wall with a deboss portion recessed therein. The deboss panel includes a means for opening a frangible panel segment of the panel wall and a rivet adapted to integrally attach a tab lever having a nose portion overlying at least a vent region of the frangible panel segment and a lift end opposite the nose. A score groove is formed in the central panel wall to define an outer perimeter of the frangible panel. The score groove has a first end adjacent the vent region and a second end joined to the first end by a curvilinear segment, whereby the first end and the second end are separated by a generally linear hinge segment of the central panel wall. The hinge segment is non-frangible to integrally connect the frangible panel segment to an adjacent area of the panel.
It is also an object of the present invention to provide such an end member wherein the central panel has a stepped profile along an outer peripheral portion.
It is another object of the present invention to provide an end member whereby the score groove is a generally v-shaped recess having a score depth into the thickness of the central panel, and the second groove is also a generally v-shaped recess having a groove depth into the thickness of the central panel less than that of the score groove. The score groove includes a check slot region for naturally slowing the fracture of the score to allow the container to vent safely.
It is further an object of the invention to provide an end member having a countersink with an inner wall, a curved segment, and an outer wall. The outer wall has a lower portion joined to an outer arcuate portion of the curved segment, a crease portion angled outwardly of the central panel, and an upper portion.
Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.
While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated.
The container end of the present invention is a stay-on-tab end member 10 with improved physical properties including strength. Essentially, the present invention provides a lightweight end member 10 which embodies the physical characteristics and properties required in the beverage container market, as explained below.
In the embodiment of
The outer peripheral edge 18 of the central panel 12 is typically coined to add strength to can end 10. Coining is the work hardening of metal between tools. The metal is typically compressed between a pair of tools, generally an upper and lower tool.
The central panel wall 12 has a displaceable tear panel 20 defined by a curvilinear frangible score 22 with an adjacent anti-fracture score 24 on the tear panel 20, and a non-frangible hinge segment 26. The hinge segment 26 is defined by a generally straight line between a first end 28 and a second end 30 of the frangible score 22. The tear panel 20 of the central panel 12 may be opened, that is the frangible score 22 may be severed and the tear panel 20 displaced at an angular orientation relative to the remaining portion of the central panel 12, while the tear panel 20 remains hingedly connected to the central panel 12 through the hinge segment 26. In this opening operation, the tear panel 20 is displaced at an angular deflection, as it is opened by being displaced away from the plane of the panel 12.
The first and second ends 28, 30 of the frangible score 22 are joined by a curvilinear segment 32. The curvilinear segment 32 includes first and second curved segments 33a, 33b joined by an arcuate transition region 34 which lies adjacent the outer peripheral edge 18 of the center panel 12 and are defined by a radius of curvature R4. (See
As best shown in
The frangible score 22 and the second groove or anti-fracture score 24 are formed using conventional-type of scoring operation during the can end forming process, using tools including an upper (public side) die with a score knife and a lower (product side) die with an anvil surface.
The score residual differential is adapted to provide a tear panel 20 with a score 22 more readily frangible than the anti-fracture score 24, a significant factor for providing efficient opening of the end member 10. Having a double score of a frangible score 22 and an anti-fracture score 24 wherein there is a score residual differential is common in the industry.
As illustrated in
The rivet 46 is formed in the typical manner. It is the conventional practice to coin the metal on the central panel 12 proximate the base of the rivet 46 during formation thereof. When the rivet 46 is completely formed in the central panel 12, a coined region 58 having a generally circular periphery is also formed and is located about the rivet 46. This coined region 58 is typically called a button coin.
The user initiates opening of the end member 10 by lifting the lift end 48 of the tab 44. This lifts the rivet 46 which causes the score groove 22 to fracture in a vent region 60 which is located at least partially within the bounds of the coined region surrounding the rivet 46. As the nose portion 52 presses against the tear panel 20, the fracture of the score 22 propagates around the tear panel 20, preferably in progression from the first end 28 of the score 22 toward the second end 30 of the score 22.
The frangible score 22 includes a length defined by a thickened portion of the residual. This length is often referred to as a check slot region 62. As illustrated in
Typically, the check slot 62 is located within the bounds of the coined region 58. The check slot 62 of the present invention, however, is located beyond the boundary of the coined region 58. Thus, the check slot 62 is not located within the thinned metal of the coined region 58 surrounding the rivet 46. This is advantageous for reasons which will be discussed below.
Preferably, the check slot region 62 includes a duel step residual differential. (See
The end member 10 also includes a vent coin 65. The vent coin 65 is a small rectangularly shaped coin placed near the frangible score 22. The vent coin 65 has a leading end 66 placed adjacent the frangible score 22 and a trailing end 67 directed outwardly and at an angle from the frangible score 22. An intermediate section 68 of the vent coin 65 intersects the anti-fracture score 24.
One purpose of the vent coin 65 is to prevent the tear panel 20 from missiling during the opening of the container. Missiling is a jutting upward of the tear panel 20 upon venting. Missiling is caused when the frangible score 22 fracture propagates beyond the vent region 60, before the container pressure is fully relieved. The loose tear panel 20 is then forced upward due to the internal pressure of the container.
The end member 10 is opened by the lifting of the rivet and subsequently by the force of the tab 44 pushing down on the tear panel 20. Initially, the frangible score 22 should only be severed in the vent region 60. This allows a small portion of the tear panel 20 metal to be pushed below the central panel 12 to open and vent the pressure within the container.
The vent coin 65 functions by displacing metal near the juncture of the check slot 62 and the vent region 60. The displaced metal in the area causes an elastic, compressive state. As such, when the frangible score 22 is severed in the vent region 60, the metal of the tear panel 20 springs out to underlap the metal of the central panel 12 in that region. This underlapping portion of the tear panel 20 is believed to keep the remainder of the tear panel 20 in place so as to avoid premature fracture of the remainder of the frangible score 22 and thereby prevent the tear panel 20 from missiling.
Typically, the vent coin 65 is located within the coined region 58. Similar to the check shot 62 of the present invention, the vent coin 65 is moved outside of the periphery of the coined region 58 surrounding the rivet 46. It is believed that by moving the vent coin 62 outside of the coined region 58 boundary, the compressive stress on the frangible score 22 is increased. Therefore, the depth of frangible score 22 in the vent region 60 may be increased, and the strength requirement of the tab 44 to begin fracture of the frangible score 22 can be decreased.
The vent coin 65 also interacts with the check slot 62 to slow the propagation of the fracture along the frangible score 22 during venting of the container.
According to another aspect of the present invention, a deboss panel 69 is formed in the public side 34a of the central panel 12. The deboss panel 69 is formed in the central panel 12 using conventional die-forming techniques. As shown in
The deboss profile 70 includes first and second opposing end portions 76, 78 joined by a pair of sidewalls 80a, 80b. The first end portion 76 includes an apex 82. The apex 82 is joined to the sidewalls 80a, 80b by first and second arcuate portions 84a, 84b. The apex 82 lies between the transition region 34 of the frangible score 22 and the outer peripheral edge 18 of the center panel 12. The first and second arcuate portions 84a, 84b extend outwardly equally from the apex 82 along a first angle such that a series of secant lengths 88a–88d arranged parallel to the Y—Y axis and opposite the apex 82 become progressively longer in length until the first and second arcuate portions 84a, 84b blend smoothly with the sidewalls 80a, 80b. (See
It should be noted that in the embodiment illustrated in
Typically, the deboss profile 70 and the frangible score 22 remain equidistant throughout the first end portion 76. The distance between the frangible score 22 and the first end portion 68 of the deboss profile 70 is generally on the order of 0.05 inches.
As illustrated in
Alternatively, as illustrated in
The relationship between the deboss panel 69 and the frangible score 22 is important. The deboss panel 69 takes up metal displaced during the scoring process and the coining of the peripheral edge 18. Also, by moving the deboss panel 69 outwardly from the frangible score 22, it is believed that the stresses created on the frangible score 22 during the forming of the deboss panel 69 are greatly reduced. This is believed to enhance score rupturing by taking up metal slack near the rivet 46 and also immediately adjacent to the frangible score 22 along its entire length from the 6 o'clock past the 9 o'clock position, the region where score rupture failure is most likely to occur. Thus, the widening of the deboss panel 69 also increases burst values by relieving the stresses on the frangible score 22. The end member 10 is also strengthened because the movement of the deboss panel 69 outwardly allows the panel to be recessed deeper, taking up even more loose metal.
Generally, the central panel 12 experiences stress gradients. As the distance from the rivet 46 (center of the central panel 12) becomes greater, the stress lessens. Thus, by moving the deboss panel 69 away from the frangible score 22, the component of stress supplied by the deboss panel 69 is reduced. Thus, the depth of frangible score 22 may be increased as much as 50% without incurring premature failure of the frangible score 22.
According to another aspect of the present invention and as illustrated in
The bead 89 provides the desirable stiffness of the central panel 12 in the region around the rivet 46, thereby reducing the amount of panel lift resulting from the force of the tab 44 on the tear panel 20 during opening. The stiffness of the tear panel 20 is primarily provided by the bead 89 being formed as drawn metal in the public side 34a of the central panel 12 immediately adjacent the coined region 58 and the rivet 46.
The bead 89 preferably has an arcuate portion and a substantially linear portion. The arcuate portion partially surrounds the coined region 58, extending a slightly longer distance on one side of the coined region 58 than on an opposing side of the coined region 58. This allows the first end 28 of the score 22 to extend upwardly so that it wraps slights around the rivet 46. The substantially linear portion is located on an opposite side of the coined region 58 as the frangible score 22.
Preferably, there is very little thinning of the metal during formation of the bead 89, and the bead 89 is instead created by forming or drawing the metal between two opposed dies to take up slack metal. The bead 89 formation thereby draws available loose metal in the region, such as loose metal caused by scoring, coining of the metal while forming the rivet 46, or coining of metal while staking the tab 44. The bead 89 also serves as a stiffening beam in the panel 12 wall immediately adjacent the rivet 46 and the coined region 58. By drawing loose metal and providing a stiffening beam, the bead 89 is adapted to provide stiffness in the panel wall 12 around the coined region 58 to decrease the panel lift and enhance the leverage by the tab 44 during opening of the end tear panel 20.
Referring to
The outer peripheral edge 18 of the central panel 12 includes a stepped profile. The stepped profile includes a first panel radius 114 interconnected to a second panel radius 116 by the previously coined portion of the outer peripheral edge 18. The first panel radius 114 has a height H2 which is approximately 0.108 inches above the annular base 100. The second panel radius 116 is joined to the inner wall 90 of the countersink 16 and has a height H3 which is approximately 0.093 inches above the annular base 100.
The dimensions of the first panel radius 114, the second panel radius 116, and the crease portion 108 were selected to optimize resistance to burst and tab-over-chime. Burst is the ability of the pour panel 20 to withstand internal pressure. Tab-over-chime is also the ability of the end member 10 to withstand internal pressure. Tab-over-chime occurs when the internal pressure forces the tab 44 upwardly. When the tab 44 is displaced upward, it can lead to ship abuse during distribution of filled containers which can cause premature failure of the pour panel 20. Thus, tab-over-chime is the internal pressure at which the tab is displaced an undesirable amount.
As the height H3 of the second panel radius 116 increases, buckle values increase; however, the tab-over-chime value decreases as the height H3 of the second panel radius 116 increases. Thus, the height H1 of the crease portion 108 can be 0.060–0.075 inches or any height or range of heights therein, and the height H3 of the second panel radius 116 can be 0.080–0.095 inches or any height or range of heights therein. It should be noted that for forming reasons, the height H1 of the crease 108 is preferably lower than the height H3 of the second panel radius 116.
According to another aspect of the invention, a method for reforming a can end shell to produce the end member 10 described herein is disclosed. The method is used to produce a lightweight end member 10, for example from an 0.0080 inch thick aluminum stock for attachment to a container necked to a 202 (2.125 inches) open end. End members 10 of the present invention are generally manufactured using a multi-stage reforming method.
In an the initial stage, the outer peripheral edge 18 of the central panel 12 is coined and reformed in the conventional manner. The coining operation creates slack metal produced by the compression of the peripheral edge 18 between the coining tools. This coining operation forces metal in the outer peripheral edge to flow both radially inwardly and radially outwardly from the peripheral edge 18.
The slack metal is removed as the countersink 16 is reformed. In this operation, the countersink 16 is reformed so that metal in the countersink 16 is moved downwardly with respect to the central panel 12. This decreases the countersink 16 depth which causes the central panel 12 height to increase. To further improve end member 10 rock and buckle performance, the outer wall of the countersink 16 may also be creased or kinked radially outwardly, as illustrated in
Next, the deboss panel 69 is formed within the central panel 12. The forming of the deboss panel 69 places the central panel 12 into the desirable tension state. The deboss panel 69 also takes up any slack metal created during the coining of the peripheral edge 18 and the scoring of the central panel 12 when the frangible score 22 and the anti-fracture score 24 are formed.
Once the tab 44 has been staked to the rivet 46, the step portion is formed at the outer peripheral portion 18. The step portion increases the height of the central panel 12 above that of the initial reform increase. The forming of the step portion increases the end member's 10 buckle resistance even higher. Also, since no slack metal is remaining from the coining and scoring operations, it has been found that the deboss panel 69 will roll up or the recess will become shallower subsequent to the step portion being formed.
In an initial trial, can ends 10 were produced with a check slot region 62 having a single step of residual thickness of 0.0016 ins., a vent coin 65 positioned below the anti-fracture score 24, and a 6:00–12:00 score residual differential of only 0.0002–0.0004 ins. This trial resulted in improved openability.
A second trial was carried out on can ends 10 as illustrated in
Since the can ends 10 successfully passed the missilng test, a complete evaluation was performed. Further tests on a total of eight sets of can ends 10, as illustrated in
The can ends 10 were also tested for pressurized openability (for beer). No failures were found until test group H.
The can ends 10 were further tested for score burst. None of the can ends 10 burst open before the maximum pressure of the test was reached. It is believed that the excellent results of this test are directly attributable to the greater distance from the deboss panel 69 to the frangible score 22.
While the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the broader aspects of the invention. Also, it is intended that broad claims not specifying details of the particular embodiments disclosed herein as the best mode contemplated for carrying out the invention should not be limited to such details.
This application is a continuation of U.S. application Ser. No. 09/748,927, which was filed on Dec. 27, 2000 now abandoned.
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Number | Date | Country | |
---|---|---|---|
Parent | 09748927 | Dec 2000 | US |
Child | 10317636 | US |