Patent Publication Number: US-2010116374-A1

Title: Method of assembling an easy open container

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No. 61/113,490 filed Nov. 11, 2008, the contents of which are incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     In the field of metal packaging, “easy open” ends for metal cans are well known. Typically, an easy open can end includes a pull tab and an approximately planar panel having a score line defining an opening area. To open a can having an easy open can end, a user may lift a handle of the pull tab to initiate fracture of the score line, and a user may subsequently pull the tab to partially or fully remove a portion of the panel, thereby creating an opening through which a user may access the contents. 
     Typically, the gap between the pull tab handle and the can end panel is very small. This small gap may make it difficult for a user to grasp the pull tab, because there may not be enough clearance under the pull tab for a user to insert a finger. Therefore, typical easy open cans may be difficult for a user to open. 
     There is a need for a method of assembling a container including a can end that may allow a user to more easily insert a finger under the pull tab, thereby providing enhanced openability. 
     SUMMARY 
     A method of forming a container having enhanced openability is disclosed. Such a method may include the steps of: (i) providing a can body; (ii) providing a can end having an approximately planar panel, a pull tab affixed to the panel, and a moveable portion disposed beneath a handle of the tab, the moveable portion being in a first position extending upwardly toward the handle; (iii) filling a comestible product into the can body at an elevated temperature; (iv) seaming the can end to the can body; and (v) moving the moveable portion from the first position to a second position extending downwardly away from the handle, such that a gap is formed or enlarged between the moveable portion and the handle, enhancing accessibility to a user&#39;s finger, the moving being in response to internal negative pressure caused by cooling of the product within the can body. 
     These and various other advantages and features are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there are illustrated and described preferred embodiments of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a top perspective view of a container including a can end seamed onto a can body; 
         FIG. 1B  is a top perspective view of the can end depicted in  FIG. 1A  prior to a seaming operation; 
         FIG. 2A  is a side cross-sectional view in the direction of arrows A-A for the can end of  FIG. 1B , showing a moveable portion in an up (convex) position; 
         FIG. 2B  is a side cross-sectional view in the direction of arrows A-A for the can end of  FIG. 1B , showing a moveable portion in a down (concave) position; 
         FIG. 2C  is a detailed cross-sectional view of the moveable portion and annular step of the can end of  FIG. 1B , showing the moveable portion in both up (convex) and down (concave) positions; 
         FIG. 2D  is a side cross-sectional view of the container of  FIG. 1A , showing a moveable portion of the can end in an up (convex) position; 
         FIG. 3A  is a schematic illustrating an example hydrostat retort for controlling the temperature and pressure during assembly of a container; and 
         FIG. 3B  is graph showing the temperature and pressure inside and outside of two example containers during assembly in the hydrostat retort illustrated in  FIG. 3A . 
     
    
    
     BRIEF DESCRIPTION OF THE APPENDICES 
     Appendix A- 1  is a table showing the raw data collected from processing different food products in different types and sizes of containers through different retorts, and determining whether or not the moveable portions  40  toggled to the downward position P 2 . 
     Appendix A- 2  is a table showing the raw data collected from processing different food products in different types and sizes of containers through different retorts, and determining whether or not the moveable portions  40  toggled to the downward position P 2 . 
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     Preferred structures and methods for can end technology are described herein. An embodiment of a can end and can that employ this technology are also described. The present invention is not limited to any particular container configuration but rather encompasses use in any container application. Further, the present invention encompasses other can end designs not described herein. 
     Referring to  FIGS. 1A and 1B  to illustrate an example structure and function of the present invention, a container  10  includes a can end  12  attached to a can body  14  by a seam  16 . The can end  12  defines a diameter D 1  and includes an approximately planar panel  20 , a countersink  21  extending about the periphery of panel  20 , a chuck wall  22  extending radially outward from countersink  21 , and a seaming panel  23  extending radially outward from chuck wall  22 . As shown, panel  20  includes a score  24 , that defines an openable panel portion  25 , beading  26 , and a moveable portion  40 . A tab  30  is attached to panel  20  by rivet  32  proximate to score  24 . Tab  30  includes a handle  34 , and a nose  36 . Moveable portion  40  defines a diameter D 2  and optionally includes a downwardly inclined annular step  42 . 
     Container  10  may be made from any material, for example, steel, aluminum, or tin. Container  10  may contain or be configured to contain a comestible product (not shown), including ready meals, fruits, vegetables, fish, dairy, pet food, a beverage, or any other product that it is desirable to have stored in metal packaging such as container  10 . Container  10  may have any length, diameter, wall thickness, and volume. Preferably, container  10  has a standard-sized interior volume that is known in the art for containing a comestible product such as ready meals, fruits, vegetables, fish, dairy, pet food, or a beverage. 
     Can end  12  may be made from any material, for example, steel, aluminum, or tin. Can end  12  preferably is formed from 0.21 mm gauge DR550N double-reduced steel. In the embodiment shown, can end  12  defines a diameter D 1  of 73 mm, although in other embodiments (not shown), can end  12  may define a diameter D 1  of any size, including, for example, 83 mm and 99 mm. As shown in  FIG. 1B , can end  12  includes an approximately planar panel  20  that is formed, pressed, and/or stamped to take a shape that may include several features. 
     As shown in  FIGS. 1A and 1B , countersink  21  is near the periphery of panel  20 . As shown, countersink  21  extends upward into chuck wall  22 , and chuck wall  22  extends radially outward to form seaming panel  23 . Seaming panel  23  is configured to allow can end  12  to be attached to the top of can body  14  via seam  16 , which is formed by bending a portion of seaming panel  23  around the top of can body  14 . In a preferred embodiment, can end  12  is seamed to can body  14  via seaming means that are known in the art (e.g., double seaming). 
     When openable panel portion  25  is partially or completely detached from the remainder of panel  20 , score  24  and/or openable panel portion  25  define an opening (not shown), through which the comestible product (not shown) may be removed from can body  14 . As shown in  FIG. 1B , score  24  defines a continuous circle without having a break or gap, thereby allowing openable panel portion  25  to be completely detached from the remainder of panel  20 . However, in other embodiments (not shown), score  24  may define a partial loop, such that openable panel portion  25  can only be partially detached from the remainder of panel  20 . 
     As shown in  FIG. 1B , openable panel portion  25  extends over most of panel  20 , and moveable portion  40  is located within openable panel portion  25 . However, in other embodiments (not shown), openable panel portion  25  may extend over a small portion of panel  20  (e.g., openable panel portion  25  may create a small aperture through which a user drinks a beverage), and moveable portion  40  may be located outside of openable panel portion  25 . 
     As shown in  FIG. 1B , panel  20  includes one or more beadings  26 , which preferably are substantially in the form of downwardly inclined annular or part-annular steps. In  FIG. 1B , three beadings  26  are shown, but in other embodiments, any number of beadings  26  may be defined by the shape of panel  20 . While not being bound by theory, it is believed that the beading may provide panel  20  with increased strength to resist buckling due to impact to container  10  or a pressure differential across can end  12 . 
     As shown in  FIG. 1B  pull tab  30  is located on the outer surface of can end  12  and may be coupled to panel  20  by rivet  32 . As shown, handle  34  of pull tab  30  is disposed towards the center of panel  20 , and nose  36  of pull tab  30  is disposed towards the periphery of panel  20 . Tab  30  may be actuated by a user to allow the user to remove some or all of the comestible product (not shown) from can body  14 . Tab  30  may be actuated by a user grasping or looping a finger under handle  34  and pulling handle  34  away from panel  20  in the direction of arrow A, thereby rotating tab  30  about rivet  32 . As handle  34  moves away from panel  20 , nose  32  of tab  30  is forced down towards panel  20 , pushing down on panel  20  approximately at or adjacent to score  24 , thereby rupturing a first portion of score  24 . Subsequently, the user pulls handle  34  in the direction of arrow B, thereby rupturing a second portion of score  24  and defining an opening (not shown) by removing all or part of openable panel portion  25  from the remainder of panel  20 . 
     As shown in  FIG. 1B , moveable portion  40  defines a diameter D 2  and is defined in panel  20 . In the embodiment shown in  FIG. 1B , moveable portion  40  is located towards the center of panel  20 , and moveable portion  40  is located within openable panel portion  25 . However, in other embodiments (not shown), such as beverage container embodiments, moveable portion  40  may be located anywhere on panel  20 , including, for example, a location outside openable panel portion  25 . In the embodiment shown in  FIG. 1B , moveable portion  40  is generally circular in plan. However, in other embodiments (not shown), moveable portion  40  may have other shapes in plan, e.g., an elliptical or an irregular shape. 
     Moveable portion  40  includes a downwardly inclined annular step  42 . As shown in  FIG. 1B , annular step  42  is located at the periphery of moveable portion  40 . However, in other embodiments (not shown), annular step  42  may be located further towards the center of moveable portion  40 , such that the diameter of annular step  42  is less than diameter D 2  of moveable portion  40 . Annular step  42  preferably is located between the periphery of moveable portion  40  and a location half-way towards the center of moveable portion  40  (i.e., having a diameter of 0.5*D 2 ). In the embodiment shown, annular step  42  defines a diameter ranging between 21.8 mm (inner diameter) and 24.1 mm (outer diameter). 
     As shown in  FIG. 1B , annular step  42  defines a continuous loop without having a break or gap. However, in other embodiments (not shown), annular step  42  may define two or more discontinuous annular step portions, each separated by a gap. As shown in  FIG. 1B , moveable portion  40  includes only a single annular step  42 . However, in other embodiments (not shown), moveable portion  40  may include any number of annular steps  42 . As shown in  FIG. 1B , annular step  42  is circular in plan. However, in other embodiments (not shown), annular step  42  may have other shapes in plan, e.g., an elliptical or an irregular shape. Annular step  42  preferably has a linear cross-section (this can be most easily viewed in  FIGS. 2A-2C ). However, in other embodiments (not shown), annular step  42  may have a curved cross-section. 
     Referring to  FIGS. 2A ,  2 B,  2 C, and  2 D, the bottom surface of handle  34  and the upper surface of moveable portion  40  define a first gap G 1  when moveable portion  40  is in an up position P 1 , and the bottom surface of handle  34  and the upper surface of moveable portion  40  define a second gap G 2  when moveable portion  40  is in a down position P 2 . The difference between first gap G 1  and second gap G 2  is best shown in  FIG. 2C  as gap difference ΔG. When moveable portion  40  is in the down position, annular step  42  is inclined downward at an angle α to the horizontal, which is preferably between eight and seventeen degrees to the horizontal. In the embodiment shown, angle α is 12.5 degrees to the horizontal. The space between can end  12  and a product  46  (after seaming of can end  12  onto can body  14 ) is shown in  FIG. 2D  as a headspace  48 . 
     When moveable portion  40  is in the up position P 1 , first gap G 1  between pull tab handle  34  and moveable portion  40  may be very small, for example, 2 mm. This relatively small first gap G 1  may make it difficult for a user to grasp pull tab handle  34 , because there may not be enough clearance under the pull tab for a user to insert a finger. When moveable position  40  is in the down position P 2 , second gap G 2  between pull tab handle  34  and moveable portion  40  may be substantially larger than first gap G 1 . This larger second gap G 2  preferably is large enough to make it easy for a user to grasp pull tab handle  34 , because there may be enough clearance under pull tab handle  34  for a user to insert at least part of a finger. 
     Moveable portion  40  preferably has two stable positions (bi-stable), i.e., the up position P 1  (shown in  FIG. 2A ) and the down position P 2  (shown in  FIG. 2B ). When can end  12  is manufactured, moveable portion  40  may be disposed in either the up or down position, depending on the particular forming method chosen. Before seaming can end  12  onto can body  14 , moveable portion  40  preferably is disposed in the up position P 1 , because can ends  12  may be more densely stacked when moveable portion  40  is disposed in the up position. When container  10  is sold to a user, moveable portion  40  is preferably disposed in the down position P 2 , in order to provide the larger second gap G 2  between handle  34  and moveable portion  40  to accommodate a user&#39;s finger. 
     In order to toggle moveable portion  40  from the up position P 1  to the down position P 2 , a force F may be applied, generally in a downward direction, to moveable portion  40  (as shown in  FIG. 2C ), thereby increasing the size of first gap G 1  by a gap difference ΔG to become second gap G 2 . The force F preferably arises from a pressure differential across can end  12 , where the pressure on the upper side of can end  12  (outside the container) is higher than the pressure on the lower side of can end  12  (inside the container). In other embodiments, the force F may arise from a mechanical force applied to the upper side of the moveable portion  40 . Under some processing conditions, the force F may be a pressure differential across can end  12  for a first set of containers  10  in a processing batch, while the force F may be a mechanical force applied to the upper side of moveable portion  40  for a second set of the containers  10  in the processing batch (e.g., those containers  10  that still have a moveable portion  40  in the up position P 1  after initial processing). 
     In some embodiments, it is desirable that can ends  12  be transported to the product-filling facility with moveable portion  40  in the up position P 1 . While can ends  12  may be formed with moveable portion  40  in either the up position P 2  or the down position P 2 , can ends  12  may be more easily stacked for transportation with moveable portions  40  in the up position P 1 . For example, in the embodiment shown in  FIG. 2D , during stacking of the can ends  12 , the tab  30  of a lower can end  12  (with the moveable portion  40  in the up position P 1 ) may nest into the bottom surface of the moveable portion  40  (in the up position P 1 ) of an upper can end. In some embodiments, it may be necessary for moveable portions  40  to be disposed in the up position P 1  to prevent damage to tabs  30  during processing, such as when using a reel and spiral retort. 
     As shown in TABLE 1 (page 8), the presence of annular step  42  in moveable portion  40  may allow moveable portion  40  to stay in the “down” position under a greater variety of post-filling pressure conditions than if annular step  42  was not included. To produce the data shown in TABLE 1, tests were performed using can end  12  designs (with and without annular step  42 ) having a diameter D 1  of 73 mm. Each can end  12  was made of 0.21 mm gauge, double-reduced (DR) tinplate to material specification DR550N. As shown, the presence of annular step  42  may allow container  10  to better withstand impacts and/or high-altitude transportation (at lower ambient pressure) without moveable portion  40  toggling back into the up position P 1 . If containers  10  are shipped to a high-altitude location, for example, the lower atmospheric pressure may lower the pressure differential across can ends  12 , increasing the chance that moveable portions  40  may toggle back into the up position P 1 . While not being bound by theory, the presence of annular step  42  may increase the pressure differential across the can end  12  that is required to toggle moveable portion  40  back into the up position P 1 . 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 Moveable Portion 
                 Pressure differential to 
                 Pressure differential to 
               
               
                 Type 
                 “Pop-down” (mbar) 
                 “Pop-up” (mbar) 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 No Annular Step 
                 &gt;1000 
                 350 
               
               
                 Annular Step 
                 830 
                 790 
               
               
                   
               
            
           
         
       
     
       FIG. 3A  is an example of a hydrostat retort that may be used to control the temperature and pressure during assembly of the container of  FIG. 1A . Referring to  FIG. 3A , a hydrostat retort system  50  includes a preheat leg  51 , a steam leg  52 , and a cooling leg  53 . Preheat leg  51  includes a first water column  54 . Cooling leg  53  includes a second water column  55 . As shown in  FIG. 3A , hydrostat retort system  50  may be used to control the temperature and pressure of container  10  during the filling process. However, in other embodiments, any retort system may be used, including a batch retort, a reel and spiral retort, and a hydrolock retort. 
       FIG. 3B  is a graph showing temperature and pressure inside and outside two example containers of during assembly in the hydrostat retort of  FIG. 3A . Referring to  FIG. 3B , the temperature and pressure graph includes a retort temperature curve  61 , a retort pressure curve  62 , a first can pressure curve  63 , and a second can pressure curve  64 . The retort temperature curve  61  includes a cool-down period  65 . The retort pressure curve  62  includes an over-pressure period  66 . The first can pressure curve  63  and the second can pressure curve  64  include a seaming time  67  (during which the containers  10  are seamed) and a low-pressure period  68 . The second can pressure curve  64  includes a pressure jump  69 . 
     As shown in  FIG. 3B , the temperature and pressure graph shows data for two containers  10  (a first can and a second can), each filled with product  46  having different process parameters, such as different amounts of headspace  48  and different product temperatures. 
     The retort temperature curve  61  shows the retort starting out at ambient temperature (for example, 25° C.), increasing and being held at a high temperature (which may kill any bacteria in the product  46 ), and then entering a cool-down period  65 , during which the retort drops back down to the ambient temperature. The retort pressure curve  62  shows the retort starting at ambient pressure, increasing and being held at a high pressure (which may allow the product  46  to be heated to a higher temperature without the included water boiling), and then entering an over-pressure period, after which the retort drops back down to the ambient pressure. 
     The first can pressure curve  63  shows the output of a pressure sensor placed inside of a first container  10 . The first can pressure  63  shows the can pressure starting out at ambient pressure (for example, atmospheric pressure), the pressure dropping slightly after the seaming time  67 , the pressure increasing while the retort pressure curve  62  is increasing, and the pressure dropping during a low-pressure period  68  that coincides with the cool-down period  65  and the over-pressure period  66 . 
     The second can pressure curve  64  shows the output of a pressure sensor placed inside of a second container  10 . The second can pressure  64  shows the can pressure starting out at ambient pressure, the pressure dropping slightly after the seaming time  67 , the pressure increasing while the retort pressure curve  62  is increasing (to a lower maximum pressure than the first can pressure curve  63 , which may be due to a different amount of headspace  48  or a different initial product  46  temperature), and the pressure dropping during a low-pressure period  68  that coincides with the cool-down period  65  and the over-pressure period  66 . The second can pressure curve  64  includes a pressure jump  69 , which represents the point where moveable portion  40  toggles from the up position P 1  (shown in  FIG. 2A ) to the down position P 2  (shown in  FIG. 2B ), momentarily slightly increasing the pressure in the second container  10 . 
     As shown in  FIG. 3B , the low-pressure period  68  of the first can pressure curve  63  and the second can pressure curve  64  may create a pressure differential across can ends  12  that results in a force F acting downward on moveable portion  40  (as shown in  FIG. 2C ). The low-pressure period  68  is created by the cooling of the steam that has collected in the headspace  48 . If the pressure differential across can ends  12  is high enough, for example, 500 or 800 mbar, then the force F acting downward on moveable portion  40  may be sufficient to toggle moveable portion  40  from the up position P 1  to the down position P 2 , thereby allowing increased finger access under tab  30  for a user. 
     Before container  10  is seamed at the seaming time  67 , a hot product  46  (at an initial equilibrium temperature, for example, of 50-70° C., that is higher than the ambient temperature), which may include a food product and juice or water, is inserted into can body  14 . At the seaming time  67 , can end  12  is seamed onto can body  14 , trapping the hot product  46  (that may contain some steam) into container  10 . If the hot product  46  is not sufficiently hot (at an initial equilibrium temperature, for example, of 25-35° C.) to result in a high enough force F acting downward on moveable portion  40  during the cool-down period  65 , steam flow closing may be used during the seaming of container  10  to allow sufficient steam to be trapped into container  10  at the seaming time  67 . 
     During the cool-down period  65 , container  10  is cooled down, gradually approaching ambient temperature. During the cool-down period  65 , the steam that was trapped inside container  10  at the seaming time  67  may be at a lower temperature than the initial temperature at seaming of container  10 . This lower temperature and resulting condensation of the steam trapped inside container  10  may result in the low-pressure period  68  being below the initial pressure inside container  10  at the seaming time  67 . 
     In some embodiments, the presence of an over-pressure period  66  may not be required to produce a sufficient pressure differential across can ends  12  to toggle moveable portion  40  to the down position P 2 . During the cool-down period  65 , the steam that may be present in headspace  48  may condense, which may reduce the pressure inside of container  10 , as shown in  FIG. 3B . This reduced pressure inside of container  10  may produce a downward force F acting on moveable portion  40 , as long as the pressure inside container  10  is less than the pressure outside of container  10 . In some embodiments, this lower internal pressure inside container  10  due to the condensation of the steam in headspace  48  may be sufficient to toggle moveable portion  40  into the down position P 2 . 
     In some embodiments, during the low-pressure period  68 , the combination of the temperature drop during the cool-down period  65  and the high retort pressure during the over-pressure period  66  may both contribute to creating a pressure differential across can ends  12  that results in a force F acting downward on moveable portion  40 . In such embodiments, it may be beneficial for toggling of moveable portion  40  to have a over-pressure period  66  during the cool-down period  65 . The amount of external pressure in the retort may be correlated to whether or not moveable portion  40  toggles to the down position P 2  during cool-down. For example, as shown in  FIG. 3B , the retort pressure reaches a maximum pressure of approximately 3000 mbar, which may contribute to the force F acting downward on moveable portion  40 , combining with the reduction of pressure inside container  10  that also may contribute to the force F acting downward on moveable portion  40 . If the combination of over-pressure in the retort and partial vacuum inside of container  10  produces a high enough force F acting downward on moveable portion  40 , moveable portion  40  may toggle into the desired downward position P 2  during processing. 
     As shown in TABLE 2, data has suggested that when processing a batch of containers  10  of a design that does not include the optional annular step  42 , a pressure differential across the can end  12  of at least 500 mbar may result in 100% of the containers  10  having their moveable portions  40  toggled to the down position P 2 . Data has suggested that when processing a batch of containers  10  of a design that include an annular step  42 , a pressure differential across the can end  12  of at least 800 mbar may result in 100% of the containers  10  having their moveable portions  40  toggled to the down position P 2 . However, as will be discussed below, there are several process variables that may contribute to whether or not a particular set of containers  10  complete processing with their moveable portions  40  toggled to the down position P 2 , including, but not limited to, the diameter D 1  of the can end  12 , the type of product  46  contained in container  10 , the temperature of product  46  contained in container  10 , the length of time during which container  10  is cooled, the external pressure in the retort acting on the outside of can end  12 , and headspace  48  (shown in  FIG. 2D ) between product  46  and can end  12  during processing. The effect of several process variables on whether or not moveable portion  40  toggles to the down position P 2  may be gleaned from a careful analysis of the data shown in Appendices A- 1  and A- 2 . 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Moveable Portion 
                 Can End 
                 Pressure differential to 
               
               
                   
                 Type 
                 Diameter 
                 “Pop-down” (mbar) 
               
               
                   
                   
               
             
            
               
                   
                 No Annular Step 
                 73 mm 
                 &gt;500 
               
               
                   
                 Annular Step 
                 73 mm 
                 &gt;800 
               
               
                   
                   
               
            
           
         
       
     
     As shown in TABLE 3, data has suggested that the diameter D 1  of can end  12  may be correlated to whether or not moveable portion  40  toggles down to the down position P 2  during cool-down following seaming and processing in a retort. TABLE 3 shows data of approximate pressure differentials across can end  12  during hydrostat retort processing that have resulted in enough downward force acting on moveable portion  40  to toggle moveable portion  40  to the down position P 2 . While not being bound by theory, it is believed that it may take a higher force to toggle moveable portion  40  in the particular designs of can end  12  that have a larger diameter D 1 , such as 99 mm, compared to a smaller force required to toggle moveable portion  40  to the down position in the designs of can end  12  that have a smaller diameter D 1 , such as 73 mm. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Can End 
                 Pressure differential to 
               
               
                   
                 Diameter 
                 “Pop-down” (mbar) 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 73 mm 
                 &gt;300 
               
               
                   
                 83 mm 
                 &gt;600 
               
               
                   
                 99 mm 
                 &gt;1000 
               
               
                   
                   
               
            
           
         
       
     
     The degree of cooling while containers  10  are in the over-pressure state in a retort may also be correlated to whether or not moveable portion  40  toggles to the down position P 2  during cool-down. While not being bound by theory, it is believed that containers  10  having a can end  12  with a larger diameter D 1 , such as 99 mm, may retain more heat for a longer period of time than containers  10  having a can end  12  with a smaller diameter D 1 , such as 73 mm. Therefore, in some designs of can ends  12  having larger diameters D 1 , the larger diameter containers  10  may not reach a temperature that is close enough to ambient temperature (prior to removal of the over-pressure) to allow enough condensation of steam in the headspace  48  to create a sufficient pressure differential across the can end  12  to toggle moveable portion  40  to the down position P 2 . For example, if the temperature in container  10  remains relatively high (e.g., 40° C.) before the over-pressure is removed, then there may not be a low enough pressure inside container  10  to toggle the moveable portion. In some embodiments, even if container  10  continues to cool down towards ambient temperature after the over-pressure is removed, the partial vacuum might not be great enough (without the over-pressure) to toggle moveable portion  40  to the down position. 
     The type of product  46  contained in container  10  and the temperature of the product and juice included in the product  46  may affect whether or not there will be sufficient force during processing to toggle moveable portion  40  from the up position P 1  to the down position P 2 . While not being bound by theory, it is believed that a juice temperature of at least 70° C. may allow sufficient steam to become trapped in container  10  at the time of seaming to allow a sufficient vacuum to develop inside container  10  after container  10  begins to approach ambient temperature (for example, 25° C.). A partial vacuum (i.e., less than atmospheric pressure inside of container  10 ) may develop in container  10  due to cooling of the steam that was trapped in container  10  at the time of seaming. When the steam at least partially condenses, it takes up less room in container  10  and may create a partial vacuum. 
     The amount of headspace  48  contained in container  10  between product  46  and can end  12  may affect whether or not there will be sufficient force during processing to toggle moveable portion  40  from the up position P 1  to the down position P 2 . While not being bound by theory, it is believed that a headspace of approximately 5-10 mm may be sufficient to allow moveable portion  40  to toggle to the down position P 2  (see Appendices A- 1  and A- 2  for detailed headspace data and corresponding results). If headspace  48  contained in container  10  at the time of seaming is higher, this may allow a greater amount of steam to be trapped inside container  10  at the time of seaming, which may result in a lower pressure inside container  10  after cooling and condensation of the steam inside container  10 . This lower pressure inside container  10  may increase the likelihood that moveable portion  40  will toggle to the down position P 2 . 
     In some embodiments, a portion of containers  10  may complete retort processing with moveable portions  40  in the up position P 1 . In such embodiments, it may be desirable to add a mechanical push-down processing step to mechanically toggle moveable portions  40  that are still in the up position P 1  so that moveable portions  40  can be shipped to consumers in the down position P 2 . For example, in one embodiment, there is a post-retort panel pusher comprising a driven wheel mounted over a slat conveyor (the wheel is driven to match the conveyor speed) that is arranged to push moveable panels  40  down as containers  10  pass under the wheel. 
     The foregoing description is provided for the purpose of explanation and is not to be construed as limiting the invention. While the invention has been described with reference to preferred embodiments or preferred methods, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Furthermore, although the invention has been described herein with reference to particular structure, methods, and embodiments, the invention is not intended to be limited to the particulars disclosed herein, as the invention extends to all structures, methods and uses that are within the scope of the appended claims. Those skilled in the relevant art, having the benefit of the teachings of this specification, may effect numerous modifications to the invention as described herein, and changes can be made without departing from the scope and spirit of the invention as defined by the appended claims. Furthermore, any features of one described embodiment can be applicable to the other embodiments described herein.