Abstract:
A shaped metal container comprising less metal than prior art shaped metal containers while still able to handle sufficient axial load and undergo shaping processes, including necking, without wrinkling, buckling, collapsing or other physical defect is disclosed. Processes for shaping a metal container having a sidewall of variable thickness, wherein a portion of the sidewall having a variable thickness is shaped using a die or dies are also disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/375,746, entitled “Shaped Aluminum Container and Method for Making Same,” filed on Aug. 20, 2010, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to metal containers and the methods for making metal containers. 
       BACKGROUND 
       [0003]    In the metal container industry, substantially identically shaped beverage containers are produced massively. Dies have been used to neck the tops of the containers. 
       SUMMARY 
       [0004]    In some embodiments, a shaped aluminum container has a sidewall comprising a top necked portion and a bottom necked portion. In some embodiments, the thickness of the sidewall in the bottom necked portions varies by at least 0.001 inches. In some embodiments, the thickness of the sidewall in the top necked portions varies by at least 0.001 inches. In other embodiments, the sidewall thickness in either the top or bottom portions, or both vary by at least 0.0015″ or 0.002″. In some embodiments, the sidewall thickness varies by no more than 0.0015″, 0.002″, 0.0025, 0.003″ or 0.004″. 
         [0005]    In some embodiments, the shaped aluminum container is manufactured by a process comprising: necking a lower portion of the sidewall with a first necking die so that a working surface of the first necking die contacts a first section of the sidewall and reduces a diameter of the first section of the sidewall by at least 3% in a single die stroke, wherein the thickness of the first section of the sidewall varies along the height of the sidewall by at least 0.001 inches; and necking an upper portion of the sidewall with a second necking die so that a working surface of the second necking die contacts a second section of the sidewall and reduces a diameter of the second section of the sidewall by at least 2% in a single stroke. In some embodiments, the thickness of the second section of the sidewall varies along the height of the sidewall by at least 0.001 inches. In other embodiments, the sidewall thickness in either the top or bottom portions, or both vary by at least 0.0015″ or 0.002″. In some embodiments, the sidewall thickness varies by no more than 0.0015″, 0.002″, 0.003″ or 0.004″. In some embodiments, the lower portion and/or the upper portion is necked with a series of necking dies. A series of necking dies may comprise two or more necking dies. In one embodiment, the lower portion is necked with two necking dies. In one embodiment the first die to neck the lower portion reduces the diameter of the container by about 6% and the second die to neck the lower portion of the container reduces the diameter of the container an additional 4% of the original diameter. In some embodiments, a single necking die may reduce the diameter of the container 2%, 3%, 4%, 5%, 9%, 12% or more. 
         [0006]    In some embodiments, the process further comprises expanding the diameter of a middle portion of the sidewall before necking the upper portion of the sidewall. In some embodiments, a thickness of the middle portion varies by at least 0.001 inches. In some embodiments, the thickest portion is at or near the top of the container. In some embodiments, the thinnest or a thin portion can be at or near the top of the container. 
         [0007]    In some embodiments, the first and the second necking dies are configured for use on metal bottle stock and comprise a necking surface and a relief. The necking surface comprises a land portion, a neck radius portion, and a shoulder radius portion, each having an inner diameter. The land portion is between the neck radius portion and the relief. The inner diameter of the land is a minimum diameter of the die. The inner diameters of the neck radius portion and the shoulder radius portion are greater than the inner diameter of the land. The relief comprises a relief surface, wherein an inner diameter of the relief surface is at least about 0.01 inches greater than the inner diameter of the land portion and an inner diameter of the relief surface is no greater than a maximum diameter so as to reduce but not eliminate frictional contact between the sidewall and the relief surface while maintaining necking performance when necking the sidewall. In some embodiments, the diameter of the relief surface is about 0.0075 to about 0.035 inches greater than the inner diameter of the land portion. In other embodiments, the diameter of the relief surface is about 0.01, 0.02 or 0.03 inches greater than the inner diameter of the land portion. In some embodiments, the length of the land portion is between about 0.02″ to about 0.08″. In other embodiments, the length of the land is about 0.03″ to about 0.07″. In yet other embodiments, the length of the land portion is between about 0.04″ to about 0.06″. In one embodiment, the length of the land portion is about 0.04″. In some embodiments, the necking die is dimensioned so that when necking the metal bottle stock, the entire land and the relief travel relative to the sidewall in an axial direction and at least a portion of the relief travels beyond a top of the sidewall. 
         [0008]    In some embodiments, the land has a surface finish Ra ranging from about 8 μin to about 32 μin. In some embodiments, the relief has a surface finish Ra ranging from about 8 μin to about 32 μin, from about 2 μin to about 6 μin or from about 2 μin to about 32 μin. In some embodiments, the neck radius portion and the shoulder radius portion have a surface finish Ra ranging from about 2 μin to about 6 μin. 
         [0009]    In some embodiments, an expansion die for manufacturing metal containers expands the diameter of the middle portion of the sidewall. The expansion die for manufacturing metal containers comprises a working surface and an undercut portion, wherein the working surface is configured to expand a diameter of a metal container having a closed bottom. The work surface comprises a progressively expanding portion and a land portion. The land portion is between the progressively expanding portion and the undercut portion. The outer diameter of the land portion is a maximum diameter of the die. In some embodiments, the length of the land portion is a minimum 0.12″. In some embodiments, the length of the land portion is between about 0.01″ to about 0.12″. In some embodiments, the length of the land portion is between about 0.02″ to about 0.08″. In other embodiments, the length of the land is about 0.03″ to about 0.07″. In yet other embodiments, the length of the land portion is between about 0.04″ to about 0.06″. In one embodiment, the length of the land portion is about 0.04″. The undercut portion comprises an undercut surface having an outer diameter. The outer diameter of the undercut surface is at least approximately 0.01 inches smaller than the outer diameter of the land portion and no less than a minimum diameter so as to reduce but not eliminate frictional contact between the undercut surface and the metal container. The outer diameter of the undercut surface is dimensioned to minimize collapse, fracture, wrinkle and all other physical defects, which may occur during expansion. The work surface is dimensioned so that when inserted into the aluminum container the entire land portion and at least a portion of the undercut portion enter the aluminum container causing the diameter of the middle portion of the sidewall to expand. 
         [0010]    In some embodiments, an initial portion of the work surface of the expansion die has a geometry for forming a transition in a container from an original diameter portion to an expanded diameter portion. In some embodiments, the transition is stepped or gradual. In some embodiments, the land portion of the expansion die has dimensions to provide an expanded diameter of a container stock worked by the work surface. 
         [0011]    In some embodiments, at least a portion of the work surface of the expansion die has a surface roughness average (Ra) of approximately 8 μin to 32 μin. In some embodiments, at least a portion of the undercut portion has surface roughness average (Ra) of approximately 8 μin to 32 μin. In some embodiments, the outer diameter of the land portion of the expansion die is substantially constant along the length of the land. 
         [0012]    In some embodiments, the diameter of the middle portion of the sidewall is expanded with a series of expansion dies. 
         [0013]    In some embodiments, the top of the container is dimensioned to accept a closure. In some embodiments, a closure covers an opening on top of the container. In some embodiments, the closure comprises one of: a lug, a crown, a roll-on pilfer proof closure or a threaded closure. 
         [0014]    In some embodiments, a can end having a severable pour spout encloses a top of the container. 
         [0015]    A process for forming a metal container comprises: providing a container having a sidewall, wherein the sidewall has a thickness and a height, and wherein the thickness varies along the height of the sidewall by at least 0.0010 inches; and necking the container with a necking die so that a working surface of the necking die contacts a section of the sidewall and reduces a diameter of the section of the sidewall by at least 2% in a single stroke, wherein the thickness of the section of the sidewall varies along the height of the sidewall by at least 0.0010 inches before and after necking. 
         [0016]    In some embodiments, the necking die used in the process of forming a metal container comprises: a necking surface and a relief; wherein the necking surface comprises a land portion, a neck radius portion, and a shoulder radius portion, each having an inner diameter; wherein the land portion is between the neck radius portion and the relief and the inner diameter of the land is a minimum diameter of the die; wherein the inner diameters of the neck radius portion and the shoulder radius portion are greater than the inner diameter of the land; wherein the relief comprises: (a) a relief surface; (b) an inner diameter of the relief surface is at least about 0.01 inches greater than the inner diameter of the land portion; (c) an inner diameter of the relief surface is no greater than a maximum diameter so as to reduce but not eliminate frictional contact between the metal container and the relief surface while maintaining necking performance when necking the metal container; and wherein the necking die is dimensioned so that when necking the metal container, the entire land and the relief travel relative to the container in an axial direction and at least a portion of the relief travels beyond a top of the container. 
         [0017]    In some embodiments, the process of forming a metal container further comprises expanding the diameter of a portion of the sidewall. 
         [0018]    In some embodiments, the process of forming a metal container further comprises necking the container with a series of necking dies. 
         [0019]    In some embodiments, the process of forming a metal container further comprises expanding the diameter of the portion of the sidewall with a series of expansion dies. 
         [0020]    In some embodiments, at least one of the expansion dies comprises: a work surface comprising a progressively expanding portion and a land portion; and an undercut portion; wherein the land portion is between the progressively expanding portion and the undercut portion and an outer diameter of the land portion is a maximum diameter of the die; wherein the undercut portion comprises: (a) an undercut surface; and (b) an outer diameter of the undercut surface, wherein the outer diameter of the undercut surface is: (i) at least approximately 0.01 inches smaller than the outer diameter of the land portion; and (ii) no less than a minimum diameter so as to reduce but not eliminate frictional contact between the undercut surface and the aluminum container; and wherein the work surface is dimensioned so that when inserted into the metal container the entire land portion and at least a portion of the undercut portion enter the metal container causing the diameter of the at least a portion of the sidewall to expand. 
         [0021]    In some embodiments, a process for forming a metal container comprises: providing a container having a sidewall, wherein the sidewall has a thickness and a height, and wherein the thickness varies along the height of the sidewall by at least 0.001 inches; and expanding the diameter of the container with an expansion die so that a working surface of the expansion die contacts a section of the sidewall and expands a diameter of the section of the sidewall by at least 2% in a single stroke, wherein the thickness of the section of the sidewall varies along the height of the sidewall by at least 0.001 inches before and after expanding. In some embodiments, the process further comprises necking the container. In some embodiments, the process further comprises expanding the diameter of the container with a series of expansion dies. In some embodiments, the expansion die comprises: a work surface comprising a progressively expanding portion and a land portion; and an undercut portion; wherein the land portion is between the progressively expanding portion and the undercut portion and an outer diameter of the land portion is a maximum diameter of the die; wherein the undercut portion comprises: (a) an undercut surface; and (b) an outer diameter of the undercut surface, wherein the outer diameter of the undercut surface is: (i) at least approximately 0.01 inches smaller than the outer diameter of the land portion; and (ii) no less than a minimum diameter so as to reduce but not eliminate frictional contact between the undercut surface and the aluminum container; and wherein the work surface is dimensioned so that when inserted into the metal container the entire land portion and at least a portion of the undercut portion enter the metal container causing the diameter of the at least a portion of the sidewall to expand. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The following detailed description, given by way of example and not intended to limit the invention solely thereto, will best be appreciated in conjunction with the accompanying drawings, wherein like reference numerals denote like elements and parts, in which: 
           [0023]      FIG. 1  is a pictorial representation of a 14 stage die necking progression for a 53 mm diameter can body in accordance with the present invention. 
           [0024]      FIG. 2  represents a cross-sectional side view of one embodiment of an initial necking die in accordance with the present invention. 
           [0025]      FIG. 2   a  represents a magnified view of the contact angle depicted in  FIG. 2 , wherein the contact angle is measured from where the bottle stock contacts the necking surface. 
           [0026]      FIG. 3  represents a surface mapping of one embodiment of a polished necking surface, in accordance with the present invention. 
           [0027]      FIG. 4  represents a surface mapping of one embodiment of a non-polished necking surface, in accordance with the present invention. 
           [0028]      FIG. 5  shows a cross-sectional side view of one embodiment of an intermediate necking die in accordance with the present invention. 
           [0029]      FIG. 6  illustrates a cross-sectional side view of one embodiment of a final necking die in accordance with the present invention. 
           [0030]      FIG. 7  shows a cross-sectional side view for the shoulder necking surface of each necking die in a 14 stage necking system, in accordance with the present invention. 
           [0031]      FIG. 8  is a plot of the necking force required to neck an aluminum bottle into a partially non-polished necking die and the force required to neck a bottle into a polished necking die, wherein the y-axis represents force in pounds (lbs) and the x-axis represents the distance (inches) in which the bottle is inserted into the necking die; 
           [0032]      FIG. 9  is a perspective view of one embodiment of an expansion die used to expand a 2.087″ diameter container to a 2.247″ diameter container, in accordance with one embodiment of the present invention; 
           [0033]      FIG. 10  is a top view of the expansion die of  FIG. 9  showing line A-A; 
           [0034]      FIG. 11  is a cross-sectional view of the expansion die of  FIGS. 9 and 10  along line A-A; 
           [0035]      FIG. 12  is a cross-sectional view of an expansion die used to expand a 2.247″ diameter container to a 2.363″ diameter container according to one embodiment of the invention; 
           [0036]      FIG. 13  is a cross-sectional view of an expansion die which can be used to expand a 2.363″ diameter container to a 2.479″ diameter container; 
           [0037]      FIG. 14  is a cross-sectional view of an expansion die which can be used to expand a 2.479″ diameter container to a 2.595″ diameter container; 
           [0038]      FIG. 15  is a cross-sectional view of a die which can be used to set the shape of the lower profile; 
           [0039]      FIG. 16  is a side view of five containers, wherein each container represents one stage of expansion of a 2.087″ diameter container to a 2.595″ diameter container according to one embodiment of the invention; 
           [0040]      FIG. 17  is a top view of the five containers of  FIG. 16 ; 
           [0041]      FIG. 18  is a bottom view of the five containers of  FIG. 16 ; 
           [0042]      FIG. 19  is a cross-section view of a metal container having a sidewall of varying thickness; 
           [0043]      FIG. 20  is a cross-section view of a necking die necking a lower portion of the sidewall of the metal container shown in  FIG. 19 ; 
           [0044]      FIG. 21  shows a cross-section view of the necking die in  FIG. 20 ; 
           [0045]      FIG. 21   a  is a partial cross-section view of the nose of the necking die shown in  FIGS. 20 and 21 ; 
           [0046]      FIG. 22  shows a cross-section of a knockout used in conjunction with the necking die in  FIGS. 20 ,  21  and  21   a;    
           [0047]      FIG. 23  is a cross-section view of an expansion die expanding a middle portion of the sidewall of the metal container shown in  FIG. 19 ; 
           [0048]      FIG. 24  shows a cross-section view of the expansion die in  FIG. 23 ; 
           [0049]      FIG. 25  depicts a metal container after a lower portion has been necked and a middle portion has been expanded; 
           [0050]      FIG. 26  shows a cross-section view of a necking die, which may be used to neck an upper portion of the sidewall of the metal container shown in  FIG. 19 ; 
           [0051]      FIG. 27  shows a cross-section view of a necking die, which may be used to neck an upper portion of the sidewall of the metal container shown in  FIG. 19 ; and 
           [0052]      FIG. 28  shows a cross-section of a knockout used in conjunction with the necking die in  FIG. 27 . 
       
    
    
     DESCRIPTION 
       [0053]    For the purposes of this specification, terms such as top, bottom, below, above, under, over, etc. are relative to the position of a finished metal container resting on a flat surface, regardless of the orientation of the metal container during manufacturing or forming steps or processes. A finished metal container is a metal container that will not undergo additional forming steps before it is used by an end consumer. In some embodiments, the top of the container has an opening. 
         [0054]    The term “bottle stock” is used throughout this specification. However, all of the processes, products and apparatuses disclosed herein are applicable to all metal containers including beverage cans and cups, aerosol cans and food containers. A quotation mark or “in” designates inches. 
         [0055]      FIG. 1  depicts a bottle stock after each stage of necking by a necking system in accordance with the one embodiment present invention, in which the inventive necking system provides for a more aggressive necking reduction scheme than was previously available with prior necking systems and the ability to neck a container through thick wall and thin wall portions, i.e. containers having sidewalls that vary in thickness by at least 0.001 inches and the necking die travels past the thick wall portion and into the thin wall portion in a single stroke.  FIG. 1  depicts the progression of necking from an initial necking die to produce the first necked bottle stock  1  to a final necking die to produce the final necked bottle stock  14 . Although  FIG. 1  depicts a necking system including 14 stages, the following disclosure is not intended to be limited thereto, since the number of necking stages may vary depending on the material of the bottle stock, the bottle stock&#39;s sidewall thickness(es), the initial diameter of the bottle stock, the final diameter of the bottle, the required shape of the neck profile, and the necking force. Therefore, any number of necking dies has been contemplated and is within the scope of the present invention, so long as the progression provides for necking without collapse or other physical defect of the bottle stock. 
         [0056]      FIG. 2  depicts a cross sectional view of a necking die including at least a partially textured necking surface  10  and a textured relief  20  following the necking surface  10 . In one embodiment, the partially textured necking surface  10  includes a shoulder or body radius portion  11 , a neck radius portion  12 , and a land portion  13 . 
         [0057]    In some embodiments, a necking die includes a partially textured necking surface  10 , which reduces surface contact between the necking surface and the bottle stock being necked in a manner that reduces the force that is required to neck the bottle (hereafter referred to as “necking force”). It has unexpectedly been determined that a necking surface having a textured surface provides less resistance to a bottle stock being necked than a non-textured surface. As opposed to the prior expectation that a smooth, non-textured, highly polished surface would provide less resistance and hence require less necking force, it has been determined that a surface with a relatively low Ra value, i.e. &lt;˜6 micro inches has greater surface contact with the bottle being necked resulting in greater resistance and requiring greater necking force. In some embodiments of the present invention, the increased surface roughness (higher Ra value) reduces the surface contact between the necking surface and the bottle being necked, hence reducing the required necking force. 
         [0058]    Reducing the necking force required to neck the bottle stock allows for necking dies having a greater percent reduction than previously available in prior necking dies. It also helps to enable the die to neck through varying thicknesses of metal sidewall. 
         [0059]    In one embodiment, a textured surface has a surface roughness average (Ra) ranging from more than or equal to 8 μin to less than or equal to 32 μin, so long as the textured necking surface does not disadvantageously disrupt the aesthetic features of the bottle stock&#39;s surface (coating) finish in a significantly observable manner. In one embodiment, a non-textured surface has a surface roughness average (Ra) finish ranging from 2 μin to 6 μin.  FIG. 3  represents a surface mapping of one embodiment of a non-textured land portion  13  of the necking die generated by ADE/Phase Shift Analysis and MapVue EX-Surface Mapping Software. In this example, the surface roughness (Ra) value was approximately 4.89 μin. 
         [0060]      FIG. 4  represents a surface mapping of one embodiment of a textured land portion  13  of the necking die, in accordance with an embodiment of the present invention generated by ADE/Phase Shift Analysis and MapVue EX-Surface Mapping Software. In this example, the surface roughness (Ra) value was approximately 25.7 μin. 
         [0061]    Referring to  FIG. 2 , in one embodiment, the partially textured necking surface  10  includes a textured land portion  13 , a non-textured neck radius portion  12 , and a non-textured shoulder radius portion  11 . In another embodiment, the at least partially textured necking surface  10  may be entirely textured. Referring to  FIG. 2   a , the contact angle α of the bottle stock  50  to the necking surface  10  may be less than 32°, wherein the contact angle is the included angle between 54 (the ray extending perpendicular to the land) and  51  (the ray extending perpendicular from the plane tangent to the point of contact by the bottle stock with the necking surface). In some embodiments, the working surface and/or relief may be entirely non-textured. In some embodiments, the working surface and/or relief is hard turned and lightly polished to knock off rough edges to obtain a surface finish of about 8-10 micro inches, or about 8-16 micro inches or about 8 to 32 micro inches. 
         [0062]    The textured land portion  13  in  FIG. 2  in conjunction with the knockout (not shown) provide a working surface for forming an upper portion of the bottle stock into a bottle neck during necking. The knockout (not shown) fits inside the container or bottle stock during necking and helps the container to be removed from the die after necking. In one embodiment, the textured land  13  extends from tangent point of neck radius portion  12  of the die wall parallel to the center line of the necking die. The textured land portion  13  may extend along the necking direction (along the y-axis) by a distance Y 1  being less than 0.5″, or being on the order of approximately 0.0625″. In some embodiments, the length of the land portion is between about 0.02″ to about 0.08″. In some embodiments, the length of the land portion is between about 0.03″ to about 0.07″. In some embodiments, the length of the land portion is between about 0.04″ to about 0.06″. In some embodiments, the length of the land portion is approximately 0.04″. 
         [0063]    Another aspect of some embodiments of the present invention is a relief  20  positioned in the necking die wall following the necking surface  10 . The dimensions of the relief  20  are provided to reduce, but not eliminate, frictional contact with the bottle stock and the necking die, once the bottle stock has been necked through the land  13  and knockout. Therefore, in some embodiments, the relief  20 , in conjunction with the partially textured necking surface  10 , contributes to the reduction of frictional contact between the necking die wall and the bottle stock being necked, wherein the reduced frictional contact maintains necking performance while reducing the incidence of collapse, buckling, rupturing, wrinkling and other physical defects, and improving stripping of the bottle stock. 
         [0064]    In one embodiment, the relief  20  extends into the necking die wall by a dimension X 2  of at least 0.005 inches measured from the base  13   a  of the land  13 , in other embodiments, at least 0.010 inches or 0.015 inches. In some embodiments, the relief extends into the die wall no more than 0.025″. The relief  20  may extend along the necking direction (along the y-axis) the entire length of the top portion of the bottle stock that enters the necking die to reduce, but not eliminate, the frictional engagement between the bottle stock and the necking die wall to reduce the incidence of collapse, buckling, rupturing, wrinkling and other physical defects, yet maintain necking performance. In one embodiment, the relief  20  is a textured surface. The transition from the land to the relief is blended, with no sharp corners, so that the metal bottle stock can travel over the land in either direction without being damaged. 
         [0065]    In some embodiments of the present invention, a necking system is provided in which at least one of the necking dies of the systems may provide an aggressive reduction in the bottle stock diameter. Although  FIG. 2  represents an introductory die, the above discussion regarding the shoulder radius  11 , neck radius  12 , land  13  and relief  20  is equally applicable and may be present in each necking die of the necking system. The geometry of the necking surface of at least one of the successive dies provides for increasing reduction, wherein the term “reduction” corresponds to decreasing the bottle stock diameter from the bottle stock&#39;s initial diameter to a final diameter. 
         [0066]    In one embodiment, the introductory die reduced the diameter of the container being necked by more than 5% in a single necking stroke, or more than 9% in a single necking stroke. The level of reduction that is achievable by the dies of the necking system is partially dependent on the surface finish of the necking surface, necking force, bottle stock material, required neck profile, and sidewall thickness(es). In one embodiment, an introductory necking die provides a reduction of greater than 9%, wherein the initial necking die is configured for producing an aluminum bottle necked package from an aluminum sheet composed of an Aluminum Association 3104 alloy, having an upper sidewall thickness of about 0.0085 inch or less and a post bake yield strength ranging from about 34 to 37 ksi. In some embodiments, the upper sidewall thickness may be 0.0085, 0.0080, 0.0075, 0.0070, 0.0060, 0.0050 inches, just to name a few examples. In some embodiments, the thickness of the sidewall in the bottom necked portions varies by at least 0.0010 inches. In some embodiments, the thickness of the sidewall in the top necked portions varies by at least 0.0010 inches. In other embodiments, the sidewall thickness in either the top or bottom portions, or both vary by at least 0.0015″ or 0.002″ In some embodiments, the sidewall thickness varies by no more than 0.0015″, 0.002″, 0.0025, 0.003″ or 0.004″. 
         [0067]      FIG. 5  depicts one embodiment of an intermediate die in accordance with the present invention, in which the intermediate necking die may be employed once the bottle stock has been necked with an initial necking die. In comparison to the introductory necking die depicted in  FIG. 2 , the intermediate necking die depicted in  FIG. 5  provides a less aggressive reduction. In one embodiment, a plurality of intermediate necking dies each provide a reduction ranging from 4% to 7%. The number of intermediate necking dies depends on the bottle stock initial diameter, required final diameter, neck profile, sidewall thickness and variability of the thickness of the sidewall. 
         [0068]      FIG. 6  depicts one embodiment of a final necking die in accordance with the present invention. The final necking die is utilized once the bottle stock has been necked by the intermediate necking dies. The final necking die has a necking surface that results in the neck dimension of the finished product. In one embodiment, the final necking die provides a reduction of less than 4%. In one embodiment, the final necking die may have a reduction of 1.9%. 
         [0069]    In one embodiment, a necking system is provided in which the plurality of necking dies include an introductory necking die having a reduction greater than 9%, 12 intermediate dies having a reduction ranging from 4.1 to 6.1%, and a final necking die having a reduction of 1.9%. 
         [0070]    In one embodiment of the present invention, a method of necking metal containers, utilizing a necking system as described above, is provided including the steps of providing an aluminum blank, such as a disc or a slug; shaping the blank into an aluminum bottle stock; and necking the aluminum bottle stock, wherein necking comprises at least one necking die having an at least partially textured necking surface. 
         [0071]    Some embodiments of the present invention provide a necking system including a reduced number of dies and knockouts, therefore advantageously reducing the machine cost associated with tooling for necking operations in bottle manufacturing. 
         [0072]    By reducing the number of necking die stages, the present invention advantageously reduces the time associated with necking in bottle manufacturing. 
         [0073]    Although the invention has been described generally above, the following examples are provided to further illustrate the present invention and demonstrate some advantages that arise therefrom. It is not intended that the invention be limited to the specific examples disclosed. 
       Example 
       [0074]    Table 1 below shows the reduction provided by a 14 stage die necking schedule, in which the necking die geometry was configured to form an aluminum bottle necked package from an aluminum bottle stock having a upper sidewall sheet thickness of approximately 0.0085 inch and a post bake yield strength ranging from about 34 to 37 Ksi. The aluminum composition is Aluminum Association (AA) 3104. As indicated by Table 1, the bottle stock is necked from an initial diameter of approximately 2,0870″ to a final diameter of 1.025″ without failure, such as wall collapse. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 53 mm Diameter Bottle Stock 
               
               
                 14-Stage Die Necking Schedule 
               
             
          
           
               
                   
                 Necking Die 
                 Starting 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                   
                 Entry 
                 Bottle 
                   
                 Final Can 
                 Percent 
                 Body 
                 Neck 
                 Neck 
                 Knockout 
                 Contact 
               
               
                 Station 
                 Diameter 
                 Stock 
                 Reduction 
                 Diameter 
                 Reduction 
                 Radius 
                 Radius 
                 Angle 
                 Diameter 
                 Angle 
               
               
                 Number 
                 (in) 
                 Diam (in) 
                 (in) 
                 (in) 
                 (in) 
                 (in) 
                 (in) 
                 (degrees) 
                 (in) 
                 (degrees) 
               
               
                   
               
             
          
           
               
                 1 
                 2.0900 
                 2.0870 
                 0.187 
                 1.9000 
                 8.960 
                 1.500 
                 0.590 
                 72.659 
                 1.8798 
                 0.000 
               
               
                 2 
                 2.0900 
                 1.9000 
                 0.080 
                 1.8200 
                 4.211 
                 1.500 
                 0.500 
                 68.828 
                 1.8000 
                 23.074 
               
               
                 3 
                 2.0900 
                 1.8200 
                 0.075 
                 1.7450 
                 4.121 
                 1.500 
                 0.450 
                 65.719 
                 1.7243 
                 23.556 
               
               
                 4 
                 2.0900 
                 1.7450 
                 0.075 
                 1.6700 
                 4.298 
                 1.500 
                 0.400 
                 62.807 
                 1.6495 
                 25.008 
               
               
                 5 
                 2.0900 
                 1.6700 
                 0.075 
                 1.5950 
                 4.491 
                 1.500 
                 0.350 
                 60.022 
                 1.5735 
                 26.766 
               
               
                 6 
                 2.0900 
                 1.5950 
                 0.075 
                 1.5200 
                 4.702 
                 1.500 
                 0.300 
                 67.317 
                 1.4980 
                 28.955 
               
               
                 7 
                 2.0900 
                 1.5200 
                 0.075 
                 1.4450 
                 4.934 
                 1.500 
                 0.250 
                 54.658 
                 1.4223 
                 31.788 
               
               
                 8 
                 2.0900 
                 1.4450 
                 0.075 
                 1.3700 
                 5.190 
                 1.500 
                 0.250 
                 52.588 
                 1.3464 
                 31.788 
               
               
                 9 
                 2.0900 
                 1.3700 
                 0.075 
                 1.2950 
                 5.474 
                 1.500 
                 0.250 
                 50.611 
                 1.2706 
                 31.788 
               
               
                 10 
                 2.0900 
                 1.2950 
                 0.075 
                 1.2200 
                 5.792 
                 1.500 
                 0.250 
                 48.714 
                 1.1944 
                 31.788 
               
               
                 11 
                 2.0900 
                 1.2200 
                 0.075 
                 1.1450 
                 6.148 
                 1.500 
                 0.250 
                 46.886 
                 1.1185 
                 31.788 
               
               
                 12 
                 2.0900 
                 1.1450 
                 0.050 
                 1.0950 
                 4.367 
                 1.500 
                 0.200 
                 45.020 
                 1.0675 
                 28.955 
               
               
                 13 
                 2.0900 
                 1.0950 
                 0.050 
                 1.0450 
                 4.566 
                 1.500 
                 0.175 
                 43.477 
                 1.0164 
                 31.003 
               
               
                 14 
                 2.0900 
                 1.0450 
                 0.020 
                 1.0250 
                 1.914 
                 1.500 
                 0.070 
                 41.363 
                 0.9955 
                 31.003 
               
               
                   
                   
                 1.0250 
               
               
                   
               
             
          
         
       
     
         [0075]    As depicted in Table 1 the necking system includes a first necking die that provides a reduction of approximately 9%, 12 intermediate dies having a reduction ranging from approximately 4.1 to 6.1%, and a final necking die having a reduction of 1.9%.  FIG. 7  represents a cross-sectional side view for the shoulder necking surface of each necking die of the 14 stage necking system represented in Table 1. In this example, the portion of the bottle stock being necked has a substantially uniform thickness. 
         [0076]      FIG. 8  depicts the force required to neck a bottle into a necking die having a textured land in accordance with the invention, as indicated by reference line  100 , and the force required to neck an aluminum container into a non-textured necking die, as indicated by reference line  105 , wherein the non-textured necking die represents a comparative example. The geometry of the necking die having the textured land and the control die is similar to the necking die depicted in  FIG. 2 . The bottle being necked had an upper sidewall sheet thickness of approximately 0.0085 inch, a post bake yield strength of approximately 34 to 37 ksi, and an aluminum composition being Aluminum Association 3104. 
         [0077]    Referring to  FIG. 8 , a significant decrease in the necking force is realized beginning at the point in which the bottle being necked contacts the textured land, as illustrated by data point  110  on the reference line  100 , as compared to a non-textured necking surface, depicted by reference line  105 . 
         [0078]    Now turning to the expansion die, a gradual expansion of a container comprised of a hard temper alloy using multiple expansion dies of increasing diameters, as opposed to using one expansion die, allows the diameter of the container to be expanded up to about 40% without fracturing, wrinkling, buckling or otherwise damaging the metal comprising the container. When expanding a container constructed of a softer alloy, it may be possible to expand the container 25% using one expansion die. The number of expansion dies used to expand a container to a desired diameter without significantly damaging the container is dependent on the degree of expansion desired, the material of the container, the hardness of the material of the container, and the sidewall thickness of the container. For example, the higher the degree of expansion desired, the larger the number of expansion dies required. Similarly, if the metal comprising the container has a hard temper, a larger number of expansion dies will be required as compared to expanding a container comprised of a softer metal the same degree. Also, the thinner the sidewall, the greater number of expansion dies will be required. Progressive expansion using a series of expansion dies may provide increases in the container&#39;s diameter on the order of 25%, wherein greater expansions have been contemplated, so long as the metal is not significantly damaged during expansion. In some embodiments, the diameter of the container is expanded more than 8%. In other embodiments the diameter of the container is expanded less than 8%, greater than 10%, greater than 15%, greater than 20%, greater than 25%, or greater than 40%. Other percentages of expansion are contemplated and are within the scope of some embodiments of the invention. 
         [0079]    Further, when expanding a coated container, a gradual expansion will help to maintain the integrity of the coating. Alternatively, a container may be expanded before coating. 
         [0080]    Necking an expanded container formed in accordance with some embodiments of the invention to a diameter greater than or equal to the container&#39;s original diameter X does not require the use of a knockout because the container&#39;s sidewall is in a state of circumferential tension following expansion. In some embodiments of the invention, a knockout can be used when necking the container. 
         [0081]    Referring to  FIGS. 9-16 , in some embodiments, the expansion die is comprised of A2 tool steel, 58-60 Rc harden, 32 finish, although any suitable container shaping die material may be used. In some embodiments, the expansion die  500  includes a work surface  100 , having a progressively expanding portion  150 , a land portion  200 , and an undercut portion  350 . An initial portion  300  of the work surface  100  in the depicted embodiment has a geometry for gradually transitioning the diameter of the container  700  sidewall  800 . The progressively expanding portion  150  has dimensions and a geometry that when inserted into the open end of a container  700  works the container&#39;s sidewall  800  to radially expand the container&#39;s diameter in a progressive manner as the container travels along the work surface  100 . In some embodiments, the expansion die  500  provides the appropriate expansion and forming operations without the need of a knockout or like structure. In some embodiments, a knockout may be used. 
         [0082]    The land portion  200  has dimensions and a geometry for setting the final diameter of the container being formed by that expansion die  500 . In one embodiment, the land portion  200  may extend a distance of 0.12″ or more. In other embodiments, the land may extend 0.010″, 0.020″, 0.04″, 0.05, 0.08 or 0.10 or more or less. An undercut portion  350  follows the land portion  200 . The transition from the land portion  200  to the undercut portion  350  is blended. The undercut portion  350  extends at least beyond the opening of the container when the die is at the bottom of the expansion stroke to enable the die to maintain control of the metal as it expands and to minimize the container becoming out-of-round. 
         [0083]    The work surface  100  may be a non-textured surface or a textured surface. In one embodiment, a non-textured surface has a surface roughness average (Ra) finish ranging from 2 μin to 6 μin. In one embodiment, the work surface  100  may be a textured surface having a surface roughness average (Ra) ranging from more than or equal to 8 μin to less than or equal to 32 μin, so long as the textured work surface  100  does not significantly degrade the product side coating disposed along the container&#39;s inner surface. 
         [0084]    In some embodiments, immediately following the land portion  200  the surface of the expansion die transitions smoothly to an undercut portion  350  in order to reduce, but not eliminate, the frictional contact between the container  700  and the expansion die  500  as the container is worked through the progressively expanding portion  150  and land portion  200  of the work surface  100 . The reduced frictional contact minimizes the incidence of collapse, buckling, rupturing, wrinkling and other physical defects, and improves stripping of the container  700  during the expansion process. In some embodiments, the undercut portion  350  is a textured surface having a surface roughness average (Ra) ranging from more than or equal to 8 μin to less than or equal to 32 μin. In some embodiments, the undercut portion  350  may extend into the expansion die wall by a dimension L of at least 0.005 inches, in other embodiments, at least 0.015 inches or 0.025″. In some embodiments, the undercut portion extends into the die wall no more than 0.025″. 
         [0085]    A die system for producing containers is provided including the expansion die  500 . The die system includes at least a first expansion die  500  having a work surface  100  configured to increase a container&#39;s diameter, and at least one progressive expansion die, wherein each successive die in the series of progressive expansion dies has a work surface configured to provide an increasing degree of expansion in the container&#39;s diameter from the previous expansion die. In one embodiment, the die system may also include one or more necking dies. 
         [0086]    Although the invention has been described generally above, the following example is provided to further illustrate the present invention and demonstrate some advantages that may arise therefrom. It is not intended that the invention be limited to the specific example disclosed. 
         [0087]    In one example, the four expansion dies depicted in  FIGS. 11-14  are utilized to increase the internal diameter of the container  700  from about 2.087″ to a diameter of about 2.595″, as depicted in  FIGS. 16-18 . The expansion die  500  depicted in  FIGS. 9-11  can be used to expand the 2.087″ diameter container to a 2.247″ diameter container. The expansion die shown in  FIG. 12  can be used to expand the 2.247″ diameter container to a 2.363″ diameter container. The expansion die shown in  FIG. 13  can be used to expand the 2.363″ diameter container to a 2.479″ diameter container. The expansion die shown in  FIG. 14  can be used to expand the 2.479″ diameter container to a 2.595″ diameter container. It should be noted that as the diameter of the container expands, it also becomes shorter. 
         [0088]    In one embodiment, the containers of  FIGS. 16-18  are comprised of 3104 aluminum alloy having a H19 temper. The sidewall thickness is about 0.0088″. It should be noted that using some embodiments of the invention, it is possible to expand thin walled (equal to or less than about 0.0041″), hard-temper (H19, H39) drawn and ironed aluminum cans varying amounts including expanding these containers greater than 8% in diameter, greater than 10%, greater than, 15%, and greater than 20%. 
         [0089]    In one example  FIG. 19 , shows a container  190  having a sidewall  192  with a thickness that varies between about 0.006″ and about 0.008″. The container  190  is aluminum in this example but may be comprised of any metal, such as steel, for example. 
         [0090]      FIG. 20  shows a necking die  196  necking a lower portion  194  of the sidewall  192 . A bottom necked portion  198  is also illustrated as well as a knockout  220 . 
         [0091]      FIGS. 21 and 21   a  show a necking die  196 , shown in  FIG. 20 , representing a series of two necking dies used to create the bottom necked portion  198  of the container  190 . The table shown next to  FIGS. 21 and 21   a  show the dimensions that vary between the first and second dies, which comprise the series of two dies used to form the bottom necked portion  198  (shown in  FIGS. 20 and 25 ) of the container  190 . Part of the working surface  197  of the necking die  196 , including the land  199  has a textured surface with an Ra value of about 12 micro inches. The Ra value of the working surface  197  that was not textured had a Ra value of about 8-10 micro inches. 
         [0092]      FIG. 22  shows a knockout  220  representative of the two knockouts used in conjunction with the necking dies  196  shown in  FIGS. 20 ,  21  and  21   a . The table shown next to  FIG. 22  shows the dimensions that vary between the first and second knockouts  220 , which were used with the series of two dies to form the bottom necked portion  198  of the container  190 . 
         [0093]    The table below shows the dimensions of the container  190  before and after each necking step in necking the lower portion  194  of the sidewall  192 . 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 sta- 
                 start 
                 reduc- 
                 final 
                 knockout 
                   
                 estimated 
                 % re- 
               
               
                 tion 
                 dia. 
                 tion 
                 dia. 
                 diameter 
                 gap 
                 metal thk 
                 duction 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 bottom 
                   
                   
                   
                   
                 0.0080 
                   
               
               
                 necking 
               
             
          
           
               
                 1 
                 2.088 
                 0.125 
                 1.963 
                 1.9450 
                 0.0090 
                 0.0083 
                 5.99 
               
               
                 2 
                 1.963 
                 0.079 
                 1.884 
                 1.8660 
                 0.0090 
                 0.0085 
                 4.02 
               
               
                   
               
             
          
         
       
     
         [0094]    The dimensions are in inches. The “gap” is the radial distance between the inner diameter of the land  199  of the necking dies  196  and the outer diameter of knockouts  220 . The “estimated metal thk” is the maximum thickness of the metal being formed by the necking die. As mentioned earlier, the metal thickness of the sidewall  192  of the containers formed in this example varies by about 0.002″ in the portion of the sidewall  192  being formed, i.e. the necking dies  196  travel over metal that varies in thickness by about 0.002″. The necking dies  196  and the accompanying knockouts  220  are designed to accommodate the thickest metal, as well as the thinnest metal they pass over in the necking process. The thickest metal in the sidewall  192 , in this example, is near the top of the container  190 . This information also applies to tables appearing later in this specification. 
         [0095]      FIGS. 23 and 24  show an expansion die  230  used to expand the diameter of a middle portion  236  of the sidewall  192  of the container  190  after the two necking steps. In this example, two expansion steps followed the two necking steps. The table shown under  FIG. 24  shows the dimensions that vary between the first and second expansion dies  230 , which comprise a series of two expansion dies. None of the expansion dies  230  were textured in this example. 
         [0096]    In the table below, “body rad.” and “neck rad.” refer to radii of the expansion dies. 
         [0000]    
       
         
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                 start 
                   
                   
                   
                   
                   
                 % 
               
               
                 station 
                 dia. 
                   
                   
                   
                   
                   
                 expansion 
               
             
          
           
               
                 bottom 
                 expan- 
                 final 
                 body 
                 neck 
                 estimated 
                 % 
               
               
                 expansion 
                 sion 
                 dia. 
                 rad. 
                 rad. 
                 metal thk 
                 expansion 
               
               
                   
               
             
          
           
               
                 1 
                 1.884 
                 0.158 
                 2.042 
                 14.000 
                 0.500 
                 0.0081 
                 8.39 
               
               
                 2 
                 2.042 
                 0.040 
                 2.082 
                 14.000 
                 0.500 
                 0.0080 
                 1.96 
               
               
                   
               
             
          
         
       
     
         [0097]      FIG. 25  shows the container after necking with the two necking dies shown in  FIGS. 20 ,  21  and  21   a  and expanding with the two expansion dies shown in  FIGS. 23 and 24 . The thin wall portion  234  and thick wall portion  232  are shown. The transition between the thin wall and the thick wall can be short or long and gradual. The necking steps followed by expansion steps form a pinch  242  in the container  190 . 
         [0098]      FIG. 26  shows a necking die  260  forming the top necked portion  262  in an upper portion  240  of the container  190 . Because of the scale of the drawing, the land and relief in the necking die is not shown. The top necked portion  262  was necked in multiple necking stations with a series of multiple different necking dies. Additional necking stations and dies may be used to obtain a bottle or other desired shape. A die representative of the five dies used in stations 1-5 is shown in  FIG. 27 . The dimensions that vary between each of the five dies used to produce the top necked portion are shown in the table labeled “Profile ‘I’” under  FIG. 27 . None of the dies in this series of five were textured.  FIG. 28  shows a knockout  280  representing the knockouts used in conjunction with the five necking dies represented in  FIG. 27 . The table next to  FIG. 28  lists the dimensions that vary between the five knockouts  280 . In this example, the outer diameter of the top of the container before necking was about 53 mm (2.087 inches). 
         [0000]    
       
         
               
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 station 
                 start dia. 
                   
                   
                 body 
                   
                 knockout 
                   
                 estimated 
                 % 
               
             
          
           
               
                 top necking 
                 reduction 
                 final dia. 
                 rad. 
                 neck rad. 
                 diameter 
                 gap 
                 metal thk 
                 reduction 
               
               
                   
               
             
          
           
               
                 1 
                 2.087 
                 0.082 
                 2.005 
                 2.950 
                 1.000 
                 1.9884 
                 0.0083 
                 0.0082 
                 3.93 
               
               
                 2 
                 2.005 
                 0.050 
                 1.955 
                 3.000 
                 1.000 
                 1.9382 
                 0.0084 
                 0.0083 
                 2.49 
               
               
                 3 
                 1.955 
                 0.045 
                 1.910 
                 3.050 
                 1.000 
                 1.8930 
                 0.0085 
                 0.0084 
                 2.30 
               
               
                 4 
                 1.910 
                 0.045 
                 1.865 
                 3.100 
                 1.000 
                 1.8480 
                 0.0085 
                 0.0085 
                 2.36 
               
               
                 5 
                 1.865 
                 0.045 
                 1.820 
                 3.150 
                 1.000 
                 1.8022 
                 0.0089 
                 0.0087 
                 2.41 
               
               
                   
               
             
          
         
       
     
         [0099]    Having described the presently preferred embodiments, it is to be understood that the invention may be otherwise embodied within the scope of the appended claims. 
         [0100]    While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.