End panel for containers
United States Patent n91 Patarini et al.  
 [ END PANEL FOR CONTAINERS [75] Inventors: Leon M. Patarini, Palos Hills;  
 Joseph A. Bronec, Chicago; Arthur P. Zundel, Mount Prospect, all of II].  
 [73] Assignee: National Can Corporation, Chicago.  
 Ill.  
 [22] Filed: Mar. 28, 1974 [2l] Appl. No.: 455,525  
 Primary Examiner-George T. Hall Attorney. Agent, or Firm-Dressler, Goldsmith.  
 Clement &amp; Gordon, Ltd  
 [451 Apr. 1, 1975 [57] ABSTRACT An end panel for a container is disclosed herein. The end panel has a tear strip defined by a weakened area of material, which has a leading end adjacent the periphery of the panel and a base end permanently attached to the main body of the panel. The area of weakened material produces a minimum residual along a portion of the leading end and the residual increases in thickness from the leading end to a maximum thickness at the base end. The configuration of the elongated tear strip is generally U-shaped and has a maximum transverse dimension along the leading edge and progressively reduces in transverse dimension from the leading edge down to an intermediate portion. The tear strip also has an integral rivet formed adjacent the leading end and the rivet has a further surrounding weakened area which has its radius located on the center of the rivet and circumscribes an arc of more than l80 about the periphery of the rivet.  
 13 Claims, 10 Drawing Figures END PANEL FOR CONTAINERS BACKGROUND OF THE INVENTION The present invention relates to an improvement in container ends of the type that have a permanently attached tear strip capable of being severed by manipulation of a tab. such as disclosed in US. Pat. No. 3.738.526. issued June I2. 1973. The portions of the disclosure in this patent not inconsistent with the present disclosure. are incorporated herein by reference.  
  In the above mentioned patent. the end panel has a tear strip which is generally U-shapcd in plan view and has a leading or tear initiating end adjacent the periph cry of the main body of the panel. The opposite or base end of the tear strip is permanently attached to the main body of the end panel.  
  An elongated tab is permanently attached by a rivet to the elongated tear strip adjacent the tear initiating end. The tear strip and tab are designed so that initial pivotal movement ofthe free end ofthe tab away from the end panel will sever the leading edge of the tear strip and the tear strip will bend along a line that ex tends generally transversely of the tear strip through the center of the rivet. This will place the leading end or tear initiating end of the tab as well as the nose end of the tab inside the container to which the end panel is attached.  
  The tab is then pushed from the handle end into the container and. during this movement. the remainder of the weakened area defining the tear strip is severed while the tab is guided along a predetermined path by having opposite edges in engagement with severed edges of the main panel. When the tab is substantially completely located within the container. a pair of reeesses on the tab are aligned with the severed edges defined in the main body so that the lower edges of these recesses define abutments which engage the lower or inside surface ofthe panel to guide the tab to a final position wherein the handle end is located adjacent the base end of the tear strip and all of the tear strip as well as substantially all of the tab is located inside the container.  
  This type of container opener has found a remarkable degree ofcommercial success. However. some difficulties have been encountered in improper opening procedures that are utilized by the consumer. For example. it has been found that some consumers have a tendency to utilize the same opening process as the consumer has been using for previously known beverage cans where the entire tear strip is removed from the end of the container.  
  For example. it has been found that some consumers will pull on the tab rather than push after the weakened area has been initially ruptured by the pivotal movement of the tab. This can result in having the entire tab and tear strip located outside the container and produce a rough edge on the tear strip which extends towards the consumer and may cause bodily injury. Furthermore. once the tear strip is located outside the container. the tab can readily be removed from the tear strip by bending the tear strip along the initial bend line produced during initial rupture of the weakened area or the entire tab and tear strip can be removed by bending along the base line defining the connection between the tear strip and the panel.  
  Another problem that has been encountered in certain uses for the container end described in the above patent is the force or internal pressure that the end panel must withstand without rupture of the area or residual that defines the tear strip. In certain applications the container end must be capable of withstanding pressures greater than 90 psi. without failure. To meet this objective, the obvious solution would be to increase the residual in the weakened area and insure that the residual will not fracture below the maximum internal pressure described above. However. in doing so. the initial rupture of the weakened area and the subsequent complete rupture of the weakened area or residual requires a substantial amount of force.  
  If the residual is made thin enough to allow rupture with a minimum force on the tab. other difficulties are encountered in preventing the container end from buckling. bulging or rupturing at the pressures dis cussed above. The bulging of the container end results in what is known as a rocker where a portion of the tab and/or end panel extends beyond the upper edge of the rim ofthe container. Blow Out&#34; is the point of failure after the buckle point of the end has been reached. When the end buckles. the weakest point of the score area fractures and the entire score area and tab blows out to relieve the pressure inside the container.  
 SUMMARY OF THE INVENTION According to the present invention. the weakened area. producing a residual that defines the tear strip in a container end panel, is designed to insure that the end panel will not bulge. buckle or rupture when the container to which it is attached is internally pressurized to a pressure of at least 90 psi. In addition. the residual is so designed that a minimum force is required for ini tially severing the first portion of the residual.  
  More specifically. the end panel has a weakened area of material that is generally U-shaped in plan view and produces a residual. defined by the weakened line. between the tear strip and the remainder of the panel. The elongated generally U-shaped tear strip is permanently connected to the remainder of the panel generally adjacent the center of the panel and has an enlarged portion adjacent the periphery thereof. The residual has a minimum thickness along a small portion of the transversely extending leading end of the tear strip and a second area of thickness on opposite sides of the minimum area which is substantially greater than the thickness of the area of minimum thickness. The residual then has a progressively increasing thickness from the second area down to the base end of the tear strip.  
  The result is that the thickness of the residual at the selected locations described above, will provide sufficient rigidity to the entire end to prevent bulging of the end. buckling of the end or rupturing when internal pressure is applied to the container to which it is attached.  
  The tear strip also has a permanent connection for a tab and the permanent connection is in the form of a rivet that is deformed from the main body of the panel. The tear strip has a further weakened line which surrounds the substantially circular rivet or connecting means and the center of the arcuate weakened line is concentric with the center of the rivet and circumseribes an arc of more than I to prevent severance of the area between the adjacent weakened area during the opening process.  
  The generally U-shaped elongated tear strip also has a maximum transverse dimension adjacent the leading end or edge which is greater than the transverse dimen sion of the tear strip along the rivet or connecting means to prevent removal of the tear strip after initial rupture thereof.  
 BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF DRAWINGS FIG. I is a fragmentary plan view of the easy open end panel;  
  FIG. 2 is a perspective view of the end panel shown in FIG. 1 and attached to a container body.  
  FIG. 3 is a view similar to FIG. 2 after the tear strip in the panel has been initially ruptured;  
  FIG. 4 is a transverse sectional view as viewed along line 44 of FIG. 3;  
  FIG. 5 is a fragmentary bottom perspective view of the end panel shown in FIG. 3&#39;.  
  FIG. 6 is a perspective view showing the tear strip and tab in its finally opened position;  
  FIG. &#39;7 is a bottom end view of the end panel before the weakened line has been ruptured;  
  FIG. 8 is an enlarged fragmentary sectional view as viewed along line 8-8 of FIG. 7;  
  FIG. 9 is a sectional view. as viewed along line 9-9 of FIG. 7&#39;. and  
  FIG. 10 is an enlarged sectional view as viewed along line l0l0 of FIG. 7.  
 DETAILED DESCRIPTION While this invention is susceptible of embodiment in many different forms. there is shown in the drawings and will herein be described in detail a preferred embodiment 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 invention to the embodiment illustrated.  
  FIG. 1 of the drawings shows an easy open end panel. generally designated by reference numeral 10, having a peripheral seam I2, which is attached by the usual double seaming process to container body 14. The container body and end panel are preferably made of metal. such as aluminum or steel. End panel 10 consists of a main panel 16 that has a weakened area of material IS defined therein to produce a substantially U-shaped elongated strip 20 which may be severed therefrom. Tear strip 20 has a leading end or nose portion 22 and a base end 24. As more clearly shown in FIG. 7. the weakened area of material 18 terminates at spaced points in the container main panel 16 so that the base end 24 of the tear strip is permanently connected to end panel I6 as will be described later.  
  Tear strip 20 also has an integral rivet or connecting means 26 for permanently connecting an opening tab 30 thereto. Connecting means 26 consists of a circular rivet which is deformed from the main body of tear strip 20 adjacent leading end 22. Connecting means or rivet 26 extends through an opening in the tab and has an enlarged portion 32 overlying the upper surface of tab 30 to prevent removal of tab 30 from the tear strip.  
  Opening tab 30 has a leading end or nose portion 34, the forward edge of which is coincident with the weakened area of material 18 along the center of leading edge 22 and tab 30 has a handle portion 36 adjacent the opposite end thereof. Tab 30 further has a pair of recesses 38 adjacent handle 36 and the bases of the recesses have a spacing which is slightly less than the transverse dimension of weakened line portion 18 adjacent base end 24 of tear strip 20.  
  Tear strip 30 also has a further weakened area 40 that is located adjacent rivet 26 on the side opposite leading end 22. The purpose of this weakened area 40 will be described later.  
  Therefore. as explained in more detail in the above mentioned Zundel et al. patent. which is incorporated herein by reference. the weakened area of material I8 is severed by initially turning the handle end 36 of tab 30 counterclockwise or away from the upper surface of main panel I6. This will rupture weakened line 18 along leading end 22 and at the same time sever weakened area 40 so that the tear strip and tab will assume a position generally shown in FIGS. 3. 4 and 5. A down ward movement or pushing force on handle end 36 of tab 30 will then sever the remainder of weakened line I8 to ultimately locate recesses 38 in alignment with the severed edges produced on main panel 16 by sever ing of the weakened line. The handle portion 36 of tab 30 is then moved generally parallel to the upper surface of main panel 16 and the recesses 38 receive opposite edges of opening 59 (FIG. 6). defined by severing weakened line 18. with side walls 42 of recesses 38 defining abutments for engaging the lower surface of main panel 16 to prevent the tab from moving upwardly out of the opening defined by tear strip 20.  
  While the end panel 10 described above and shown and claimed in the above mentioned Zundel et al. patent has met with the remarkable degree of commercial acceptance. and has been a major breakthrough in the container industry. several problems have developed in the market testing of these end panels.  
  One of the problems that has arisen is the fact that in certain uses, the end panel does not have sufficient strength to withstand the pressures developed internally of the container during packaging and shipment of products. particularly carbonated beverages. For example, it has been found that internal pressures within the container for carbonated beverages or the like may reach psi while the filled containers are being shipped and/or stored during warm summer temperatures. Thus, in some instances. the end panel may buckle due to the large internal pressures that are developed within the container. This will result in what is known as rockers which means that the tab and/or a portion of the main panel 16 extend beyond the peripheral edge of the rim defined by seam 12 so that the container will not be flat adjacent one end. In other instances. the pressure within the container may be sufficient to cause blow out&#34; which is a condition where a portion of the end panel is severed because of the internal pressures and the entire scored area and tab is severed from the remainder of the container.  
  It will be appreciated that the initial rupture of the end panel will in most instances occur somewhere along the score line 18 since this is the weakest area of container end panel 10. Of course. the obvious solution would be to increase the thickness of the residual that remains between the tear strip and main panel 16 and- }or increase the thickness of the metal that is used for end panel 10. However, such solutions are not feasible for several reasons. In the first instance. increasing the thickness of the residual in the weakened score line 18 will of necessity increase the force necessary to rupture the score line. Thus. increasing the overall residual thickness would be unacceptable because it would result in an end panel that would require forces greater than minimum standards in the industry to rupture the score line.  
  The other alternative of increasing the thickness of the metal container while structurally acceptable. would be economically unacceptable because it would increase the overall cost of the container.  
  According to the present invention. the weakened area of material defining the tear strip is designed so as to be capable of withstanding increased pressure and still have the panel formed of metal. such as aluminum. having minimum thickness. This is accomplished without increasing the forces required for severing the score line. when desired.  
  More specifically, the residual in the weakened area of material has a minimum thickness along a portion of the leading end of tear strip 20 and then is stepped to a substantially greater thickness along a second area thereof which terminates substantially along a plane that extends transversely of the tear strip through the center of the connecting means. The remainder of the residual. defined by weakened line 18, is then progressively increased in steps from adjacent the center of connecting means 26 to the base end of tear strip 20. The details of the residual defined by weakened area of material [8 will be described in connection with reference to FIGS. 7 through 10.  
  Residual R defined by weakened area of material l8 has a first thickness X or minimum thickness along a small portion of the weakened line on opposite sides of the center line CL of longitudinal tear strip 20. The elongated dimension L of the residual area of minimum thickness X is substantially less than the transverse dimension of the leading end 22 of tear strip 20. Preferably. the elongated dimension is less than 0.25 inches and is on the order of 20 percent of the transverse dimension of leading edge 22. Residual R then has second portions L located on opposite sides of first portion L. and the second portions have thicknesses Y that are substantially greater than the thickness X of residual R adjacent the leading edge of tear strip 20. The elongated dimension ofeach portion L of intermediate thickness Y of residual R extends from one end of the portion of minimum thickness L to a plane P running transversely through the center line of connecting means 26. The remainder of residual R, identified by reference numeral Z, has an elongated dimension L which extend from plane P to base end 24 of the container tear strip. The thickness of residual R progressively increases in steps from plane P to a maximum thickness adjacent base end 24 of tear strip 20.  
  Summarizing the configuration of residual R, the residual has a first segment L that extends in opposite directions from center line CL along leading end 22 of tear strip 20 and this residual is of minimum thickness. Residual R then has second segments L, which have a thickness substantially greater than the thickness of residual X or first segment L and segments L, terminate adjacent a plane that extends perpendicular to the longitudinal center line CL through the center of connecting means 26. Residual R also has third segments L, which extend from plane P to the base end of tear strip 20 and these segments have a residual of progressively increasing thicknesses from plane P to base end 24.  
  While not specifically limited to actual dimensions. the specific dimensions for weakened area material 18 will be described in connection with a container end panel 10 made from gauge [9 aluminum which has a metal thickness on the order of 0.0!35 inches. The thickness X of residual R along first segment L would be on the order of0.002 to 0.003 inches. The thickness Y of residual R along second segments L will be in the range of0.003 to 0.004 inches. Third segments L have a residual of progressively increasing thickness in steps and terminate at the base end 24 with a thickness in the range of 0.004 to 0.006 inches. Thus. for example. if the residual thickness X were 0.002 inches. and the length of segment L could be about 0.100 inches. the residual thickness Y in segments L, could be 0.0035 inches while the residual in segments L would increase in increments and have a thickness adjacent base end 24 of 0.004 inches.  
  It has been determined that with a residual of the configuration described above. the container end panel is capable of withstanding internal pressures greater than 90 psi. without having the end panel buckle or having the weakened area severed, resulting in blowout.&#34; In addition, by having a residual of minimum thickness along a small portion underlying the nose portion of opening tab 30. the initial rupture of the weakened area can be accomplished with minimum force being applied in a counterclockwise direction to handle end tab 36. Once this initial rupture has been accomplished. the remaining portions of residual R can readily be severed with a minimum amount of force.  
  Another problem encountered with container ends of the above type is that in certain instances. the tab may be separated from the remaining portion of tear strip 20 during the opening process. it has been found that in certain instances. when the tab 30 is pivoted to the position shown in FIGS. 3 and 4 a weakening of the tear strip material occurs generally along plane P because of the severing of arcuate score 40. Thus. according to another aspect of the present invention. arcuate score 40 is specifically configured to insure that any further tearing beyond the opposite end of arcuate score 40 will occur at location that will prevent separating of the tab from tear strip 20.  
  As clearly shown in FIG. 7, arcuate area 40 of reduced cross section has its center located concentrically with the center of connecting means 26 and cir cumscribes an arc of more than This means that should the tear strip be fractured beyond opposite ends of arcuate area 40 of reduced cross section. this severing will occur along a plane extending towards leading end 22 of container tear strip 20 to insure that the tear strip will not be severed generally along plane P and ultimately result in the tab being removed from the remainder of the tear strip.  
  As indicated above, another problem has been encountered in consumer acceptance of the end panel of the type described in the above mentioned Zundel et al.. patent. It has been found that consumers have become so conditioned in opening containers having beverages therein, that difficulties have been encountered. For example, it has been determined that a consumer is so conditioned that the recited steps in the opening of a container are ignored and the customary process is utilized. This customary process consists of initially manipulating the opening tab 30 to initiate rupture of the weakened line and then pull on the tab to sever the remainder of the weakened area of material.  
  If this procedure is followed in the end panel of the type under consideration. the nose portion or leading end of the tear strip can readily be pulled to a position above the main panel 16 and the remainder of weak ened area severed during this manipulation so that it is then impossible to properly position the tear strip and tab as originally intended.  
  Thus. according to the present invention, the tear strip is specifically configured so as to substantially eliminate the possibility of forcing the tear strip to a position above main body 16 after it has been initially ruplured.  
  Referring specifically to FlGS. 3, 4 and S. the leading end or tear initiating end 22 of tear strip 20 has a first transverse dimension identified by the reference nu meral B (FlG. 4) which is substantially greater than the transverse dimension, identified by reference numeral A. along plane P extending through the center line of connecting means 26. More specifically. the tear strip has a major transverse dimension adjacent the tear initiating end or nose portion 22 and is constantly reduced in transverse dimension along a taper which extends well beyond plane P and which ultimately merges with a base area of constant transverse dimension adjacent base end 24 of tear strip 20.  
  As was indicated above. during the initial ripening step in severing container tear strip 20 from main panel 16, tab 20 is pivoted away from main panel 16 and the pivot axis for this pivotal movement, due to the configuration of weakened area of material 18, will be generally along line plane P extending through the center of connecting means 26. Thus. after the initial pivotal movement from the position shown in FIG. 2 to that shown in FIG. 3, weakened area of material 18 will be ruptured to approximately the center of centering means 26 and will assume a position shown in FIGS. 4 and 5. in this position, the nose portion or leading end 22 of tear strip will be located inside the container and will have transverse area B which is greater than the transverse area A. of the opening 59 that is ultimately defined in main panel 16 as shown in FIG. 6. in this po sition. it is virtually impossible for the leading edge of tear strip 20 to be pulled through opening 59.  
  The present invention provides a simple expedient for greatly increasing the amount of pressure that can be developed internally of the container without buckle, rupture or bulging. Furthermore, all of this is accomplished with metal of minimum thickness that maintains the cost of the end panel at a competitive price with respect to other containers.  
  The tear strip is designed to substantially eliminate the possibility of having the tear strip pulled from the container end panel during the severing of the weakened line.  
 What is claimed is:  
  1. An easy open end panel having a weakened area defining a generally U-shaped. elongated tear strip in said end panel, said tear strip having a leading end and an opposite base end, said leading end being located adjacent the periphery of said end panel and said base end defining a permanent connection between said tear strip and said end panel. said weakened area producing a residual between said tear strip and said end panel, said residual having an area of minimum thickness on at least a portion of said leading end and an area of maximum thickness adjacent said base, said residual having an increasing thickness between said residual area of minimum thickness and said residual area of maximum thickness.  
  2. An easy open end panel as defined in claim 1. in which said residual area of maximum thickness is approximately twice the thickness of said residual area of minimum thickness.  
  3. An easy open end panel as defined in claim 1, in which said tear strip has a substantially circular connecting means adjacent said leading end for connection of an elongated tab thereto, and in which said residual has a progressively increasing thickness from a plane extending transversely of said elongated tear strip substantially at the center of said connecting means to said base end.  
  4. An easy open end panel as defined in claim 3, in which said residual area of minimum thickness defines a first segment extending on opposite sides of a longitudinal center line through said elongated tear strip.  
  5. An easy open end panel as defined in claim 4, in which said residual area of minimum thickness has an elongated dimension of less than 0.25 inches.  
  6. An easy open end panel as defined in claim 3, in which said residual area of minimum thickness is in the range of 0.002 to 0.003 inches and said residual area of maximum thickness is in the range of 0.004 to 0.006 inches.  
  7. An easy open end panel as defined in claim 3, in which said tear strip has an arcuate weakened line surrounding said substantially circular connecting means. said arcuate weakened line having its center concentric with the center of said connection portion and circumscribing an arc of more than 8. An easy open end panel as defined in claim 3, in which the transverse dimension at said leading end is greater than the transverse dimension along said plane so that pivotal movement of said leading end about said plane will prevent movement of said leading end from one side to an opposite side said end panel.  
  9. An easy open end panel as defined in claim 1, in which said tear strip has an enlarged transverse dimension at said leading end and has a constantly reducing taper from said leading end to an intermediate portion of said tear strip and in which said tear strip has a substantially constant transverse dimension from adjacent said intermediate portion to said base end.  
  10. An easy open end panel consisting of a generally circular main panel having a peripheral edge; a weakened area within said main panel defining an elongated tear strip extending generally radially from the periph cry of said main panel. said elongated tear strip having a tear initiating end adjacent the periphery of said main panel and a base end located a substantial distance from the periphery of said main panel. and connecting means in said tear strip adjacent said tear initiating end for connecting a tab thereto, said connecting means being generally circular. said weakened area having a transverse dimension at said tear initiating end which is greater than the transverse dimension along a plane extending transversely of said tear strip through the center of said connecting means so that pivotal movement of a tab connected to said connecting means in a direction away from a main body of said main panel will rupture said weakened end along said tear initiating end and prevent movement of said tear initiating end to the opposite side of said panel.  
  11. An easy open end panel as defined in claim 10, in which said generally circular connecting means has a generally arcuate area of reduced cross-section in said tear strip surrounding said connecting means, said arcuate area circumscribing an arc of greater than 180 and having its center concentric with said connecting means.  
  12. An easy open end panel as defined in claim 10, in which said tear strip has a major transverse dimension adjacent said tear initiating end and has a constantly reducing taper, in plane view, from said tear initiating end toward said base end, said tear strip having a constant transverse dimension from said base end toward said connecting means and merging with said reducing taper between said connecting means and said base end.  
  13. An easy open end panel as defined in claim 10, in which said weakened area defines a residual between said tear strip and said main panel, said residual having (1) a first segment of minimum thickness along a portion of said tear initiating end (2) second segments on opposite ends of said first segment, said second segments having a thickness substantially greater than said first segment. and (3) third segments between said second segments and said base end, said third segments each having a progressively increasing thickness from said second segments to said base end.