Abstract:
A non-precurled, non-curled shell is transferred to a reform station. The reform station contains a coin die and a coin punch. The coin die has the desired round finished blank diameter machined into its face. The die cavity has a round die wall which stops the outward flow of material during the coining process. The die wall produces the blank&#39;s final shape. During the coining process, the coining punch compresses the scalloped blank edge of the non-curled, non-precurled shell. The coined area causes material to flow outward, coming in contact with the die wall, forming the blanks outer perimeter.

Description:
The present invention relates to process for reforming the edge of a container opening cover and in particular to a method and apparatus for reforming the edge of a two piece or three piece shell before the shell is seamed to a container body to reduce scalloping or other irregularities in the shell perimeter. 
     BACKGROUND INFORMATION 
     A number of processes are used for closing or covering a container opening such as in the process of manufacturing and filling a two piece or three piece beverage or food container. Typically, a container body has a side wall which is substantially cylindrical with at least one substantially circular rim defining an open end of the container body. In a number of previous configurations, a container end shell which is substantially disk-shaped (although it may have various recesses, scores, indicia and the like) has a perimeter substantially the same shape as the container opening rim. The container may be closed by seaming the angular region of the shell perimeter to the rim region of the container body such as by a double seaming operation, as known to those of skill in the art. 
     In many situations, it is strongly preferred to maintain, at any circumferential position along the shell perimeter or the container body rim, a sufficient radial extent of the annular shell portion which is to be seamed, in proximity with the can body rim portion to which it is to be seamed, so as to assure that the seam will have structural integrity, form a desired, preferably hermetic, seal between the shell and the container body and will be able to withstand certain shocks or impacts such as those often encountered during transport, retailing, sale and normal end-user use. 
     A number of procedures often involved in providing or forming the shell  912  (FIGS. 9A and 9B) result in a shell whose perimeter departs from perfect regularity (typically, departs from perfect circularity) such as when portions of the shell periphery are somewhat indented or scalloped, as compared to a perfect circular form. These departures of the shell periphery from ideal regularity contribute to container configurations in which the amount of material provided to achieve the seaming operations exceed the materials that are, at least theoretically, minimally required. For example, when, to achieve the desired seaming integrity, an annular region with a radial extent of X is needed, if the shell edge is scalloped inwardly by radial extent equal to Y, the shell must be provided with an annular seaming region having a nominal or intended radial extent of about X+Y (so that, even in portions of the annular region where scalloping occurs, the radial extent will be at least equal to the nominal or intended extent of X+Y, less the maximum scalloping defect of Y, to provide a guaranteed minimum radial extent of X, as desired). 
     For this reason, some shell formation and/or seaming operations provide a double seam which is larger than that which would be theoretically minimally required, in order to maintain seam integrity even in the face of an amount of shell edge scalloping. Accordingly, it would be useful to provide a procedure which can reduce or eliminate the adverse effects of scalloping on seam sizes, so as to provide for containers with rugged and integral seams but with a reduced seam size. 
     In many container-forming procedures, it is desirable to provide seaming regions (or other regions) of the container end closure shell which has a degree of hardness, e.g. to assist in maintaining seam integrity, regardless of normal shocks or impacts on the container. To provide for proper seaming, the shell typically must have a diameter suited to the container body rim diameter, but which also has sufficient thickness to provide and maintain a reliable seam. Accordingly, it would be advantageous to provide a shell which provides for at least regions that are hardened, particularly in the annular seaming area. It would be advantageous to provide a process for forming shells that results in at least some increase in effective shell diameter, without thinning regions of the shell to the point that structural integrity may be compromised. 
     SUMMARY OF THE INVENTION 
     The present invention involves subjecting the shell or shell blank to the application of a forming operation such as coining, spinning or die-forming at least in the periphery or seaming area of the shell, prior to the seaming operation. Preferably, if coining is used, the coining operation involves use of a die having a wall which can define the desired (typically, regular) shape of the shell periphery, so that coining may reform a shell from a shape which may have scalloped or otherwise irregular edges to a shape which has substantially regular, substantially unscalloped edges. Preferably, the present invention allows the formation of containers having a seam size smaller than the seam size provided in correspondingly-shaped containers formed by previous procedures, substantially without sacrificing integrity or durability of the seam. The coining operation preferably provides an increase in the diameter of the shell (at least some locations around the circumference) all having relatively minor effects on the thickness of the coined region. Preferably, the coining achieves a degree of work-hardening of the coined area, which may help to offset the effects of any diminution of thickness caused by the coining operation. 
     In one embodiment, a non-precurled, non-curled shell is transferred to a reform station. This station contains a coin die and coin punch. The coin die has the desired round finished blank diameter machined into the die face. The die cavity has a round die wall which stops the outward flow of material during the coining process. The die wall produces the blank&#39;s final shape. During the coining process, the coining punch compresses the scalloped blank edge of the non-curled, non-precurled shell. Coining of the coined area causes the material to flow outward until it comes in contact with the die wall, forming the blanks outer diameter. This corrects the scalloped edge of the blanks and additionally work hardens the edge and increases the blank diameter. This configuration can also eliminate the need for (expensive) non-round cut edge tooling. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top plan view of an unreformed shell positioned in a coining die according to an embodiment of the present invention; 
     FIG. 2 is a cross sectional view of the shell and die taken along line  2 — 2  of FIG. 1, also showing a coining punch, according to an embodiment of the present invention; 
     FIG. 3 is an enlarged detail of region  3  of FIG. 2; 
     FIG. 4 is a top plan view corresponding to the view of FIG. 1 but after a coining operation has been performed; 
     FIG. 5 is a cross sectional view taken along line  5 — 5  of FIG. 4; 
     FIG. 6 is a enlarged detail view of region  6  of FIG. 5; 
     FIG. 7 is a flow chart showing selected steps in a shell forming and seaming operation according to previous procedures; and 
     FIG. 8 is a flow chart showing selected steps of a shell formation and seaming procedure, including coining according to embodiments of the present invention. 
     FIGS. 9A and 9B are flow charts of processes according to embodiments of the present invention. 
    
    
     DETAILED DESCRIPTION 
     In typical situations, a container end shell  112  is formed of a metal, such as an aluminum alloy. As depicted in FIG. 2, the container end shell  112 , while roughly circular in shape, may have departures from strict circularity such as having one or more inwardly indented or scalloped regions  114   a,b,c,d  defining earring gaps. The departures from regularity can arise from a number of sources including imperfections in the original cutting or stamping of the planar or disk-shaped blank, shaping procedures such as stamping or other procedures for forming the annular recess  116  and/or the raised  118  periphery of the shell and may have contributions from the metallurgy of the shell and/or imperfections in tooling concentricity. In any case, it is common for a shell such as that depicted in FIGS. 1 and 2 to have at least one and often plurality of scallops or earring gaps  114   a-d . The radial extent  312  (FIG. 3) of the gap will, as shown, typically vary along the circumference of the shell. In a typical shell intended for use in forming a typical  12  ounce beverage container, the gap  312  is commonly no greater than about 0.0050 inches although there can be substantial variation in this value. The resultant variations in uncurled lip height lead to a double seam size which is greater than desired, thus increasing the material cost of the container. 
     According to one embodiment, the shell  112  may be reformed by coining some or, preferably all, peripheral areas of the shell. As best seen in FIGS. 2 and 3, in one embodiment the shell  112  is positioned  914  (FIGS. 9A and 9B) over or within the cavity  121  of a die  122 . The die  122  has an annular surface  124  for receiving and supporting at least the annular periphery of the shell  112 . Adjacent the outer edge of the support  124  is an upstanding wall region  126  of the die. The wall  126  defines the desired shape (such as circular) and diameter of the shell. 
     As depicted in FIGS. 2,  3 ,  5  and  6 , a punch  212  is configured to cooperate with the die  122 , to perform coining as described more thoroughly below. The punch  212  includes an outer cylindrical wall  214  with a shape and diameter to match (preferably with close tolerance) the shape and diameter of the die wall  126 . The coining surface defines a generally annular flat region  216  extending radially inward a distance  612  (FIG.  6 ). In one embodiment, when the coining includes contacting an annular region of said shell blank with a contact surface of a punch, the contact surface of the punch has a shape corresponding to the annular region. 
     In practice, a shell  112  is positioned in the cavity of the die  122  as depicted in FIGS. 1 and 2. The punch  212  is brought downward  218  with sufficient force to achieve coining as described below. At the maximum downward stroke of the punch  212 , as depicted in FIGS. 5 and 6, the punch  212  causes plastic deformation of the metallic peripheral region of the shell. The coining process causes the coined area  412  (FIG.  4 ), to be reduced  616  in thickness, compared to the thickness  314  of the area prior to coining. The coining also results in shell material being displaced into the scalloped or gap regions  114   a,b,c,d  so that the coin material flows, generally in a net radially outward direction until it meets the die wall  126 , as depicted in FIG. 6, thus achieving a shell periphery which has the regularity (and diameter) of the die wall  126 . 
     In general, the total reduction in volume (the reduction in thickness) 616 times the area of the coined region  412  will not be substantially greater than the total volume of the pre-coining scalloped regions or gaps  114   a,b,c,d . Thus, it is anticipated that, for most situations, the coining will provide a reduction in thickness 616 of the periphery region of the shell which is small enough so as to not seriously affect the strength or integrity of the shell. However, to the extent that there might otherwise be some reduction in strength or integrity, there is an offsetting factor of an increase in hardness resulting from the work-hardening effect of the coining process in the coined area  412 . 
     As shown in FIG. 7, previous procedures typically involved receiving a planar blank  712 , forming  716  an annular recess  116  or otherwise shaping the blank. As described above, in previous procedures the shell was curled and seamed to join the can body  722 , often after a pre-curl operation  720 . 
     As depicted in FIG. 8, the present invention preferably adds a process of coining to achieve edge reform  818 , prior to the curling step  722  (and preferably prior to a pre-curl  720  end, and in the depicted embodiment, after other forming steps such as forming the annular recess  716 . 
     In view of the above description, a number of advantages the present invention can be seen. The present invention reduces or eliminates the effects of nonregularity or scalloping of blank or shell edges. Containers with smaller seam sizes can be achieved without compromising seam integrity or durability. Seam areas are provided which have been work-hardened and the increase in diameter arising form the coining operation results in savings of material. 
     A number of variations and modifications of the invention can be used. It is possible to use some features of the invention without using others. For example, it is possible to use the present invention for providing work hardening of the peripheral area of the shell without necessarily fully eliminating earring gaps. Although the present invention has been illustrated with examples of shells with circular ideal peripheries, the present invention could be used for shells (and containers) with noncircular shape such as ellipses, ovals, polygonal cross sections and the like. Although one example of a radial extent  612  of a coining area has been provided, the present invention can be used with larger or smaller coining areas. Although the present invention has been illustrated by examples in which the coining operation is performed as a separate operation, it is possible to design processes in which the coining operation as described herein is performed simultaneously when one or more other operations such as a scoring operation, a recess or rib-forming operation, and the like. Although the depicted embodiment provides for a annular coining area which lies in a plane substantially parallel to the plane of the major web region of the shell, the coining area can be differently oriented. Although in the depicted embodiment, the inner wall  222  of the punch is conically shaped, (to assist in punch withdrawal) while the outer wall  214  is cylindrical, it is possible to provide a (preferably slight) bevel or angle to the outer wall (preferably with a corresponding angle to the die wall) to assist in punch withdrawal and/or guidance or alignment. Although the illustrated embodiments provide a punch coining surface  216  substantially parallel to the plane of the shell, it is possible to provide for the bottom surface of the punch (and thus of the resultant coining area) with a (preferably slight) inward or outward bevel. Although the disclosure herein has included a description of coining as a forming operation, other forming operations can also be used and can reduce or eliminate irregularities in the blank periphery, e.g. to permit smaller seams. Examples of other forming operations include spinning  916  (FIG. 9A) or die-forming ( 918  FIG.  9 B). Those of skill in the art will understand how to use spinning or die-forming to reduce or eliminate irregularities, after understanding the present disclosure. 
     The present invention, in various embodiments, includes components, methods, processes, systems and/or apparatus substantially as depicted and described herein, including various embodiments, subcombinations, and subsets thereof. Those of skill in the art will understand how to make and use the present invention after understanding the present disclosure. The present invention, in various embodiments, includes providing devices and processes in the absence of items not depicted and/or described herein or in various embodiments hereof, including in the absence of such items as may have been used in previous devices or processes, e.g. for improving performance, achieving ease and/or reducing cost of implementation. 
     The foregoing discussion of the invention has been presented for purposes of illustration and description. The foregoing is not intended to limit the invention to the form or forms disclosed herein. Although the description of the invention has included description of one or more embodiments and certain variations and modifications, other variations and modifications are within the scope of the invention, e.g. as may be within the skill and knowledge of those in the art, after understanding the present disclosure. It is intended to obtain rights which include alternative embodiments to the extent permitted, including alternate, interchangeable and/or equivalent structures, functions, ranges or steps to those claimed, whether or not such alternate, interchangeable and/or equivalent structures , functions, ranges or steps are disclosed herein, and without intending to publicly dedicate any patentable subject matter.