초록 ▼

A method and apparatus are disclosed which are suitable for use in the manufacture of two-piece metal containers. In particular, the method and apparatus disclose a way of making cups from metal sheet using a combination of stretching and (re-)drawing operations. The resulting cups have the advantag

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

대표청구항 ▼

1. A method for manufacture of a metal cup, the method comprising the following steps: clamping an annular region on either or both of a sidewall and of a base of the cup to define an enclosed portion which includes all or part of the base, the base and sidewall of the cup being integral and formed

1. A method for manufacture of a metal cup, the method comprising the following steps: clamping an annular region on either or both of a sidewall and of a base of the cup to define an enclosed portion which includes all or part of the base, the base and sidewall of the cup being integral and formed of a metal sheet;deforming and stretching at least some of the enclosed portion to thereby increase the surface area and reduce the thickness of the base, the annular clamping restricting or preventing metal flow from the clamped region into the enclosed portion during this deforming and stretching step; andafter the deforming and stretching step, drawing the cup to pull and transfer outwardly material of the stretched and thinned base into the sidewall. 2. A method as claimed in claim 1: wherein the annular clamping of the deforming and stretching step comprises using one or more clamping elements having a clamping face, the clamping face having a textured surface. 3. A method as claimed in claim 1, wherein the annular clamping is performed by clamping opposing surfaces of either or both the sidewall and the base of the cup between corresponding opposing first and second clamping elements, each of the first and second clamping elements having a clamping face with geometric discontinuities to thereby assist in disrupting the flow of the metal of the cup between the first and second clamping elements as the deforming and stretching step is performed. 4. A method as claimed in claim 3, wherein the geometric discontinuities comprise any one of: i. the clamping face of the first clamping element having one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features in the clamping face of the second clamping element; orii. the clamping face of the second clamping element instead having 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 in the clamping face of the first clamping element; oriii. a combination of (i) and (ii). 5. A method as claimed in claim 4, wherein the first and second clamping elements are adapted such that, in use, the one or more beads, ridges or steps 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 in the corresponding clamping face of the second or first clamping element. 6. A method as claimed in claim 1: wherein the deforming and stretching step comprises moving either or both of a stretch punch and the cup toward each other so that the stretch punch deforms and stretches the at least some of the enclosed portion. 7. A method as claimed in claim 6, wherein the stretch punch comprises an end face having one or more relief features. 8. A method as claimed in claim 6, 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 deforming and stretching step comprising moving either or both of the first and second groups towards each other to deform and stretch the at least some of the enclosed portion. 9. A method as claimed in claim 1, further comprising an initial drawing step performed before the deforming and stretching step, the initial drawing step comprising drawing a metal sheet to form the cup. 10. A method as claimed in claim 1, wherein the drawing step comprises or is followed by a step of ironing the cup. 11. A method as claimed in claim 1 wherein the drawing step reduces a height of a dome formed during the deforming and stretching step by pulling and transferring material of the stretched and thinned base. 12. An apparatus for manufacture of a metal cup, the apparatus comprising: a clamping tooling adapted to clamp the cup formed of a metal sheet, the cup having a sidewall and an integral base, the clamping tooling adapted to clamp an annular region on either or both the sidewall and the base to define an enclosed portion which includes all or part of the base;a stretch tool adapted to deform and stretch at least some of the enclosed portion in a stretching operation to thereby increase the surface area and reduce the thickness of the base, the clamping tooling further adapted to restrict or prevent metal flow from the clamped region into the enclosed portion during this stretching operation; andtooling for drawing the cup, the drawing tooling adapted to pull and transfer outwardly material of the stretched and thinned base into the sidewall. 13. An apparatus as claimed in claim 12, wherein the clamping tooling is adapted to clamp an annular region on the base of the cup. 14. An apparatus as claimed in claim 12, wherein the clamping tooling comprises a clamping element having a clamping face, the clamping face having a textured surface. 15. An apparatus as claimed in claim 12, wherein the clamping tooling comprises a first clamping element and a second clamping element, the first and second clamping elements adapted to clamp opposing surfaces of either or both the sidewall and the base of the cup, each of the first and second clamping elements having a clamping face with geometric discontinuities to thereby assist in disrupting the flow of the metal of the cup between the first and second clamping elements as the stretching operation is performed. 16. An apparatus as claimed in claim 15, wherein the geometric discontinuities comprise any one of: i. the clamping face of the first clamping element having one or more beads, ridges or steps which, in use, urge metal of the clamped annular region within corresponding one or more relief features in the clamping face of the second clamping element; orii. the clamping face of the second clamping element instead having 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 in the clamping face of the first clamping element; oriii. a combination of (i) and (ii). 17. An 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 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 in the corresponding clamping face of the second or first clamping element. 18. An 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 cup toward each other so that, in use, the stretch punch deforms and stretches at least some of that part of the base which lies within the enclosed portion. 19. An apparatus as claimed in claim 18, wherein the stretch punch has an end face with a non-planar profile, the apparatus adapted to move either or both of the stretch punch and the cup toward each other so that, in use, the stretch punch deforms and stretches at least some of that part of the base which lies within the enclosed portion into a corresponding non-planar profile. 20. An apparatus as claimed in claim 18, wherein the stretch punch comprises an end face having one or more relief features. 21. An 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 at least some of that part of the base which lies within the enclosed portion. 22. An apparatus as claimed in claim 12, the apparatus further comprising tooling adapted to initially drawing a metal sheet to form the cup for the stretching operation. 23. An apparatus as claimed in claim 12, further comprising tooling for ironing the cup. 24. An apparatus as claimed in claim 12, wherein the drawing tooling is adapted to reduce a height of a dome formed by the stretch tool by pulling and transferring material of the stretched and thinned base.