Patent Publication Number: US-2007108208-A1

Title: Container end closure with pull tab

Description:
BACKGROUND OF THE INVENTION  
      1. Technical Field  
      The invention relates to containers and pull tab openers therefore. In particular, the invention relates to a pull tab opener formed with one or more protrusions in the central panel portion of the end closure approximate the rivet which reduce the force required to lift up the back end of the tab for subsequent breakage of the frangible panel from the end closure.  
      2. Background Information  
      Millions of aluminum containers are produced each year, usually for storing beverages. These containers have a pull tab for separating a tear panel from the central panel of the end closure to provide access to the contents of the container. These pull tabs are attached to the central panels of the end closures by rivets which are usually formed integral with the end closure. At one side of the rivet opposite the outer end of the pull tab, is a scored opening which is a push-in closure which seals the can and withstands the internal pressure. The push-in closure or tear panel is opened by lifting the outer end of the tab and pulling upward so as to pivot the tab about the rivet. This tends to deform the central panel of the end closure with the nose of the pull tab breaking the frangible panel away from the central panel. Free lift is referred to in the container art as the force required to lift up the back of the tab until the tab nose begins to press down on the frangible panel. This free lift is an ergonomic feature to allow one to get the end of ones finger under the tab end for leverage for lifting the tab and breaking the frangible panel. Experience shows that this free lift is not as easy as desired in the container industry, and that numerous attempts have been made to reduce this free lift force without weakening the end closure and components thereof. Furthermore, the tabs must sit tight to the lids during can manufacturing to prevent interference with the canning equipment and must stay properly aligned for subsequent breakage of the frangible panel.  
      The ability to lift up the rear of the tab with less force is a long time goal of the can industry. With up to 90 PSI inside some container cans and the varying thin walls, the container is very optimized. Numerous end closure modifications have been made for accomplishing this function with modified and articulate tabs. Examples of these prior art container end closures with pull tabs which attempt to reduce the free lift are shown in U.S. Pat. Nos. 6,050,440, 6,234,336, 6,405,889, 6,575,325, and 6,889,862. Although some of the can end closures of these prior art patents may be satisfactory in reducing the free lift, the present invention is believed to provide for an enhanced container end closure which reduces the free lift force in a simple and effective manner without materially changing the usual construction of the end closure, and which avoids any adverse effect during can end manufacture and subsequent attachment of the end closure to a filled container.  
     BRIEF SUMMARY OF THE INVENTION  
      One aspect of the present invention is to provide a container end closure primarily for beverage containers, in which one or two C-shaped or crescent-shaped protrusions are formed in the central panel of the end closure located closely adjacent about the rear of the rivet, which protrusions will lessen the free lift forces required to lift the rear end of the tab, enabling the tab end to more easily be raised up and then pivoted about the rivet, whereby the nose of the tab engages the frangible panel.  
      A further aspect of the present invention is to arrange the crescent-shaped protrusions concentrically with respect to each other and concentrically about the rivet, with each of the protrusions having an arcuate length of approximately 180°, and in which the ends of the protrusions lie on an imaginary line extending through the center of the tab rivet.  
      A still further feature of the present invention is to form the crescent-shaped protrusions whereby the top center of the first protrusion is approximately 0.20 inches from the center of the rivet with the top center of the second protrusion lying approximately 0.25 inches from the center of the rivet, which distances are closer than the heretofore prior art protrusions and indentations to facilitate the pulling up of the rivet from the central panel to lessen the free lift forces and allow the rear of the tab to be more easily raised up prior to the nose of the rivet engaging the frangible panel.  
      A further feature of the present invention is to provide the crescent-shaped protrusions with a height of approximately 0.010 inches when the thickness of the end panel metal, when formed of aluminum, is approximately 0.007 inches.  
      A further feature of the invention is that the location of a first and/or second protrusion is either within an opening of the pull tab or beneath the pull tab to prevent interference with the can manufacturing equipment and to permit the tab to lay relatively flat against the end panel.  
      These features and advantages are obtained by the easy opening end closure of the present invention, the general nature of which may be stated as comprising: a central panel having a product side and a public side and a tear panel defined by a score line wherein said tear panel is to be at least partially separated from the central panel to form an opening in said end closure; a rivet disposed on the central panel; a pull tab hingedly secured to the rivet, said pull tab having a nose at one end overlying the tear panel and a lift end on an opposing end, at least one opening formed in the opposing end of the pull tab; and a first crescent-shaped protrusion formed in the central panel proximate the rivet and disposed under either the lift end of the tab or within the opening formed therein.  
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      Preferred embodiments of the invention, illustrative of the best modes in which Applicant contemplates applying the principles, are set forth in the following description and are shown in the drawings and are particularly and distinctly pointed out and set forth in the appended claims.  
       FIG. 1  is a top perspective view of the container end closure with the pull tab secured thereon.  
       FIG. 2  is an exploded perspective view of  FIG. 1  showing the pull tab removed from the end panel.  
       FIG. 3  is an enlarged fragmentary top perspective view of the end panel with the pull tab removed.  
       FIG. 4  is an enlarged top plan view of the end panel and pull tab as shown in  FIG. 1 .  
       FIG. 5  is a sectional view taken on line  5 - 5 ,  FIG. 4 .  
       FIG. 5A  is a greatly enlarged fragmentary view of the encircled portion of  FIG. 5 .  
       FIG. 6  is a top perspective view of a second embodiment of the container end closure.  
       FIG. 7  is an exploded perspective view of  FIG. 6  with the pull tab removed from the end panel.  
       FIG. 8  is an enlarged fragmentary top perspective view of the second embodiment of  FIG. 6  with the pull tab removed from the end panel.  
       FIG. 9  is an enlarged top plan view of the end panel and pull tab as shown in  FIG. 6 .  
       FIG. 10  is a sectional view taken on line  10 - 10 ,  FIG. 9 .  
       FIG. 10A  is a greatly enlarged fragmentary view of the encircled portion of  FIG. 10 .  
       FIG. 11  is a top plan view of the first embodiment of  FIGS. 1-5  with the pull tab shown in dot dashed lines on the end panel.  
       FIG. 12  is a top plan view of the second embodiment of  FIGS. 6-10  with the pull tab shown in dot dashed lines on the end panel. 
    
    
      Similar numbers refer to similar parts throughout the drawings.  
     DETAILED DESCRIPTION OF THE INVENTION  
      A first embodiment of the improved container end closure of the present invention is indicated generally at  1 , and is shown in  FIGS. 1-7  and  11 . End closure  1  includes a central panel  3  having a generally circular shape which includes a circumferentially extending raised side wall  5  having an edge  7  for attaching end closure  1  to a suitable cylindrical container (not shown) in a manner well-known in the art.  
      In a preferred embodiment, end closure  1  will be formed of aluminum with central panel  3  having a thickness of approximately 0.007 inches. A usual tear panel  9  is formed in central panel  3  and defined by a frangible score line  11 . Tear panel  9  includes a usual curved D-shaped protrusion  13  having an inner curved portion  15  which closely aligns with the curved outer end  17  of tab nose  19  of a usual pull tab, indicated generally at  21 . Tab  21  is of a usual construction well-known in the beverage can art, having nose  17  and a rear curved lift end  23 . Lift end  23  is grasped by a user which positions their fingers under the end and partially into an adjacent circular opening  25 . The opposite end of the pull tab includes nose  19  which is used to drive the tear panel  9  downwardly when the pull tab lift end  23  is pulled upwardly and hingedly pivots tab  21  about a pull tab rivet  29 .  
      Rivet  29  is formed integrally in central panel  3  and is attached to tab  21  by usual metal staking operation as it extends through a circular hole  31  formed in a forward end of tab  21 . Hole  31  is formed in an arcuate-shaped hinge portion  33  which is partially circumscribed by an arcuate-shaped cutout  35  formed in tab  21 . Furthermore, arcuate cutout  35  is separated from tab opening  25  by a solid material cross member  37  of pull tab  21 . This pull tab attachment construction is well-known in the container end closure art and thus is not described in further detail.  
      In accordance with the main feature of the present invention, a generally C-shaped or crescent-shaped protrusion or depression, hereinafter referred to as protrusion  41 , is formed in central panel  3 , and in particular in the oval-shaped recessed portion  43  of central panel  3  in which the pull tab tear panel, score line and other components of the easy opening can end tab are located.  
      Protrusion  41  preferably has an arcuate length in the range of from 140° to 180° and partially circumscribes rivet  29 . Protrusion  41  preferably has an arcuate length of 180°. The ends of protrusion  41  as shown in  FIG. 11 , lie on an imaginary line  57  which extends through midpoint  55  of rivet  29 . In the preferred embodiment, protrusion  41  has a height  45  as shown in  FIG. 5A  which is approximately 0.010 inches when the thickness of central panel  3  is approximately 0.007 inches. Furthermore, in accordance with one of the unique features of the present invention, the top center midpoint of protrusion  41  lies a distance indicated at D 1 , from the top center midpoint  55  of rivet  29 , approximately 0.20 inches. It has been found that locating protrusion  41  closely adjacent and rearward of rivet  29  with respect to tab nose  19  this distance D 1  provides the desired results, that is, a lowering of the lift force required to lift rivet end  23  upwardly from its at rest position to begin the initial upward movement of rivet  29  closely followed by the downward movement of tab nose  19  to fracture score line  11 .  
      A modified enclosure is indicated generally at  51 , and is shown in particular in  FIGS. 6-10  and  12 . Enclosure  51  is similar in many respects to that of end closure  1 , and thus is not described in further detail except for the addition of a second protrusion  53 . Protrusion  53  has a similar C-shape or crescent-shape configuration as protrusion  41  and is located concentrically with respect to protrusion  41  as shown in  FIG. 8 . Protrusion  53  also extends throughout an arc of  1800  and the ends thereof lie on the same imaginary line  57  as do the ends of protrusion  41  as best shown in  FIG. 12 . As shown in  FIG. 10 , protrusion  53  has a height  55  which preferably is the same as height  45  of protrusion  41 , that is, 0.010 inches when central panel  3  has a thickness of approximately 0.007 inches. Furthermore, in accordance with the invention, the top center midpoint of protrusion  53  is located a distance D 2 , approximately 0.25 inches from the top midpoint of rivet  29 , as shown in  FIG. 10A .  
      In accordance with still another feature of the present invention, inner protrusion  41  lies completely within arcuate cutout  35  of tab  21 , as shown in  FIGS. 4 and 9 , with outer protrusion  53  lying beneath the solid material cross member  37  of pull tab  21  as shown in  FIGS. 9 and 12 . This prevents either of the protrusions from coming into contact with the various tab-staking equipment and transfer mechanisms used when forming end closures  1  and  51 , and the subsequent equipment used for seaming the end closures onto a filled container. It also enables the pull tab to remain relatively flat against the central panel as is required for use with existing can manufacturing equipment.  
      It has been found that the location of protrusion  41  and the pair of protrusions  41  and  53  at the relatively close locations rearwardly of tab  29 , that is, a distance of approximately 0.20 inches and 0.25 inches respectively, and their concealment and protection within arcuate cutout  35  and beneath tab cross member  37 , provides for reduction in the free lift force and prevents the protrusions from hampering the use of existing can-making equipment, enabling the tab to remain in its designed flat condition within recess  43  of the end closure. Thus, protrusion  41  and the pair of protrusions  41  and  53 , enables the rivet to lift upwardly more easily thereby lessening the free lift force on tab end  23 , allowing the rear of the tab to be more easily raised up followed by the subsequent engagement of the nose end of the tab against the tear panel than believed heretofore possible with existing pull tabs having various types of projections and protrusions formed in the end panel adjacent the rear of the rivet.  
      Furthermore, as shown in the drawings, protrusions  41  and  53  have substantially flat top outer surfaces and are separated by a substantially flat arcuate surface portion  59  of central panel  3 . Also, protrusions  41  and  53  are formed independently on central panel  3  and are free of any connecting members or portions therebetween, except for arcuate portion  59 .  
      In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.  
      Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.