Can manufacture

Abstract

A method and apparatus are disclosed which are suitable for use in the manufacture of two-piece metal containers. In particular, a way of making cups from metal sheet is disclosed using a combination of stretching and drawing operations. The resulting cups have the advantage of having a base thickness that is thinner relative to the ingoing gauge of the metal sheet.

Ws claimed: 
     
         1 . A method for manufacture of a metal cup for the production of a two-piece food container, the method comprising the following operations:
 i. a stretching operation performed on a metal sheet, the operation comprising clamping an annular region on the sheet to define an enclosed portion, and deforming and stretching all or part of the enclosed portion to thereby increase the surface area and reduce the thickness of the enclosed portion, the annular clamping adapted to restrict or prevent metal flow from the clamped region into the enclosed portion during the stretching operation;   ii. a drawing operation for drawing the metal sheet into a cup having a sidewall and an integral base, wherein the base comprises material from the stretched and thinned enclosed portion, the drawing operation adapted to pull and transfer outwardly material of the stretched and thinned enclosed portion whereby light-weighting of the cup is achievable in a cost-effective manner.   
     
     
         2 . The method as claimed in  claim 1 , wherein the drawing operation is adapted such that material of the stretched and thinned enclosed portion is pulled and transferred into the sidewall. 
     
     
         3 . The method as claimed in  claim 1 , wherein the stretching operation is performed on a plurality of enclosed portions separated from each other and disposed across the area of the metal sheet. 
     
     
         4 . The method as claimed in  claim 1 , wherein the annular clamping of the stretching operation comprises using one or more clamping elements having a clamping face, the clamping face provided with a textured surface. 
     
     
         5 . The method as claimed in  claim 1 , wherein the annular clamping of the stretching operation is performed by clamping opposing surfaces of the metal sheet between corresponding opposing first and second clamping elements, each of the first and second clamping elements having a clamping face provided with geometric discontinuities to thereby assist in disrupting the flow of the metal of the metal sheet between the first and second clamping elements as the stretching operation is performed. 
     
     
         6 . The method as claimed in  claim 5 , wherein the geometric discontinuities comprise any one of:
 the clamping face of the first clamping element being provided with one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features provided in the clamping face of the second clamping element; or   ii. the clamping face of the second clamping element instead provided with one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features instead provided in the clamping face of the first clamping element; or   iii. a combination of (i) and (ii).   
     
     
         7 . The method as claimed in  claim 6 , wherein the first and second clamping elements are adapted such that, in use, the one or more beads, ridges or steps provided in the clamping face of the first or second clamping element urge metal of the clamped annular region so as to be wholly enclosed by and within the corresponding one or more relief features provided in the corresponding clamping face of the second or first clamping element. 
     
     
         8 . The method as claimed in  claim 1 , wherein the stretching operation comprises providing a “stretch” punch and moving either or both of the “stretch” punch and the metal sheet toward each other so that the “stretch” punch deforms and stretches all or part of the enclosed portion. 
     
     
         9 . The method as claimed in  claim 8 , wherein the “stretch” punch comprises an end face having one or more relief features. 
     
     
         10 . The method as claimed in  claim 8 , wherein the “stretch” punch comprises a punch assembly, the assembly comprising a first group of one or more punches opposing one surface of the enclosed portion and a second group of one or more punches opposing the opposite surface of the enclosed portion, the stretching operation comprising moving either or both of the first and second groups towards each other to deform and stretch all or part of the enclosed portion. 
     
     
         11 . The method as claimed in  claim 1 , wherein the drawing operation comprises or is followed by an ironing operation. 
     
     
         12 . An apparatus for manufacture of a metal cup for a two-piece food container, the apparatus comprising:
 clamping means for clamping a metal sheet during a stretching operation, the clamping means adapted to clamp an annular region on the sheet to define an enclosed portion;   a stretch tool adapted to deform and stretch all or part of the enclosed portion in the stretching operation to thereby increase the surface area and reduce the thickness of the enclosed portion, the clamping means further adapted to restrict or prevent metal flow from the clamped region into the enclosed portion during the stretching operation; and   means for drawing the metal sheet into a cup having a sidewall and an integral base, the base comprising material from the stretched and thinned enclosed portion, the drawing means adapted to pull and transfer outwardly material of the stretched and thinned enclosed portion in a drawing operation, whereby lightweighting of the cup is achievable in a cost-effective manner.   
     
     
         13 . The apparatus as claimed in  claim 12 , wherein the drawing means is adapted to pull and transfer material of the stretched and thinned enclosed portion into the sidewall. 
     
     
         14 . The apparatus as claimed in  claim 12 , wherein the clamping means comprises a clamping element having a clamping face, the clamping face provided with a textured surface. 
     
     
         15 . The apparatus as claimed in  claim 12 , wherein the clamping means comprises a first clamping element and a second clamping element, the first and second clamping elements adapted to clamp opposing surfaces of the metal sheet, each of the first and second clamping elements having a clamping face provided with geometric discontinuities to thereby assist in disrupting the flow of the metal of the metal sheet between the first and second clamping elements as the stretching operation is performed. 
     
     
         16 . The apparatus as claimed in  claim 15 , wherein the geometric discontinuities comprise any one of:
 i. the clamping face of the first clamping element being provided with one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features provided in the clamping face of the second clamping element; or   ii. the clamping face of the second clamping element instead provided with one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features instead provided in the clamping face of the first clamping element; or   iii. a combination of (i) and (ii).   
     
     
         17 . The apparatus as claimed in  claim 16 , wherein the first and second clamping elements are adapted such that, in use, the one or more beads, ridges or steps provided in the clamping face of the first or second clamping element urge metal of the clamped annular region so as to be wholly enclosed by and within the corresponding one or more relief features provided in the corresponding clamping face of the second or first clamping element. 
     
     
         18 . The apparatus as claimed in  claim 12 , wherein the stretch tool comprises a “stretch” punch, the apparatus adapted to move either or both of the “stretch” punch and the metal sheet toward each other so that, in use, the “ stretch” punch deforms and stretches all or part of the enclosed portion. 
     
     
         19 . The apparatus as claimed in  claim 18 , wherein the “stretch” punch has an end face provided with a non-planar profile, the apparatus adapted to move either or both of the “stretch” punch and the metal sheet toward each other so that, in use, the “stretch” punch deforms and stretches all or part of the enclosed portion into a corresponding non-planar profile. 
     
     
         20 . The apparatus as claimed in  claim 18 , wherein the “stretch” punch comprises an end face having one or more relief features. 
     
     
         21 . The apparatus as claimed in  claim 18 , wherein the “stretch” punch comprises a punch assembly, the assembly comprising a first group of one or more punches opposing one surface of the enclosed portion and a second group of one or more punches opposing the opposite surface of the enclosed portion, the first and second groups moveable towards each other to, in use, deform and stretch all or part of the enclosed portion. 
     
     
         22 . The apparatus as claimed in  claim 12 , wherein the drawing means is adapted to first initially draw the sheet into a cup profile and to then subsequently re-draw the cup in one or more stages. 
     
     
         23 . The apparatus as claimed in  claim 12 , further comprising means for performing an ironing operation on the cup. 
     
     
         24 . A container body comprising a cup as formed by the method of  claim 6 . 
     
     
         25 . A container body comprising:
 a cup having an access opening, the cup formed of metal sheet and having a sidewall and integral base, wherein the base is a stretched base such that the thickness of the base is less than the ingoing gauge of the metal sheet used to form the cup.   
     
     
         26 . A container comprising the container body of  claim 25 , further comprising a closure fastened to the access opening of the container body. 
     
     
         27 . A tooling for selectively forming a blank of material into a container, the container including a circumferential sidewall and a bottom portion enclosing an end of the circumferential sidewall, the tooling comprising:
 an upper tooling assembly; and   a lower tooling assembly,   wherein the blank of material is clamped between the upper tooling assembly and the lower tooling assembly, proximate to the circumferential sidewall, and   wherein the bottom portion is stretched relative to the circumferential sidewall to form a thinned preselected profile.   
     
     
         28 . The tooling of  claim 27 , wherein the upper tooling assembly comprises a forming punch; wherein the lower tooling assembly comprises a pad; and wherein the forming punch is configured to move the blank of material into contact with the pad. 
     
     
         29 . The tooling of  claim 28 , wherein the pad includes a step bead structured to crimp and lock the blank of material between the upper tooling assembly and the lower tooling assembly. 
     
     
         30 . The tooling of  claim 29 , wherein the lower tooling assembly further comprises a contour; wherein the contour is configured to engage and stretch the bottom portion to form the thinned preselected profile. 
     
     
         31 . The tooling of  claim 30 , wherein the thickness of the material at or about the dome is about 0.0003 inch to about 0.002 inch thinner than the base gauge. 
     
     
         32 . The tooling of  claim 27 , wherein the blank of material has a preformed dome portion. 
     
     
         33 . The tooling of  claim 27 , wherein the container is a can body. 
     
     
         34 . The tooling of  claim 27 , wherein the container is a cup. 
     
     
         35 . The tooling of  claim 27 , wherein the thinned preselected profile is a dome. 
     
     
         36 . The tooling of  claim 27 , wherein the material of the container at or about the dome has a substantially uniform thickness. 
     
     
         37 . The tooling of  claim 27 , wherein the blank of material has a base gauge prior to being formed; wherein, after being formed, the material of the container at or about the dome has a thickness; and wherein the thickness of the material at or about the dome is less than the base gauge. 
     
     
         38 . A method for selectively forming a container, the method comprising:
 introducing a blank of material to tooling;   forming the blank of material to include a circumferential sidewall and a bottom portion enclosing an end of the circumferential sidewall;   clamping the material between said tooling proximate to the circumferential sidewall to resist movement of the material; and   stretching the bottom portion to form a thinned preselected profile.   
     
     
         39 . The method of  claim 38 , wherein said thinned preselected profile is a dome. 
     
     
         40 . The method of  claim 38 , further comprising:
 providing as said blank, a blank having a preformed dome, and said forming step comprising stretching and thinning said preformed dome.