Method for expanding a cylindrical metallic precursor in the manufacture of a three-piece can and shaping mandrel for expanding a cylindrical metallic precursor

Method according to any one of the preceding claims, wherein during the second step, the first subgroup expands from the first diameter to the second diameter.

Method according to any one of the preceding claims, wherein during the second step, all the segments are actuated to expand outwards at the same velocity.

Method according to any one of the preceding claims, wherein the second step comprises an initial stage where the arcuate surfaces of the second subgroup are engaged with the inner surface of the precursor and radially inwards of the arcuate surfaces of the first subgroup.

Method according to any one of the preceding claims, wherein the second step comprises an intermediate stage where the arcuate surfaces of the second subgroup are radially aligned with the arcuate surfaces of the first subgroup and edges of the arcuate surfaces of adjacent segments are initially engaging.

Method according to any one of the preceding claims, wherein the second step comprises a final stage where the arcuate surfaces of the second subgroup are radially outwards of the arcuate surfaces of the first subgroup.

Method according to any one of the preceding claims, wherein the first diameter is between 10% and 20% greater than the initial diameter of the precursor.

Method according to any one of the preceding claims, wherein, after the second step, a circumferential gap is formed between edges of the arcuate surfaces of adjacent segments and a width of the gap does not exceed 5 mm, preferably does not exceed 2 mm, more preferably does not exceed 1.5 mm.

Method according to any one of the preceding claims, wherein the second diameter is between 20% and 30% greater than the initial diameter of the precursor.

Method according to any one of the preceding claims, wherein the first and second steps are performed without rotation of the precursor with respect to the mandrel.

Method according to any one of the preceding claims, wherein the arcuate surface of one or more of the plurality of segments is profiled in the longitudinal direction such that after the second step, the expanded precursor body has a profiled outer surface.

Method according to any one of the preceding claims wherein, after the second step, the expanded precursor body has a profiled outer surface with portions of the outer surface having the second diameter and other portions of the outer surface being recessed with respect to the second diameter by at least 10%, 12% or 15% and preferably at least 20%.

A three-piece can having an outer diameter and a profiled outer surface, wherein a first portion of the outer surface is recessed by at least 10%, 12% or 15% and preferably by at least 20% with respect to a second portion of the outer surface having the outer diameter.

A three-piece can having an outer diameter and a profiled outer surface, wherein a first portion of the outer surface is recessed by at least 10% with respect to a second portion of the outer surface having the outer diameter and the first portion and the second portion are at a same longitudinal position of the outer surface but at different circumferential positions and a longitudinal profile length at all circumferential positions around the can is equal.

A three-piece can having a can body with a profiled outer surface comprising a groove extending around a circumference of the body and wherein a longitudinal position, cross-sectional shape and/or orientation of the groove varies around the circumference, subject to each longitudinal section around the circumference of the can body having an identical profile length.

A shaping mandrel for expanding a cylindrical metallic precursor in the manufacture of a three-piece can, the mandrel comprising:

• an actuator arm;
• and
• a plurality of longitudinally extending segments, arranged about the actuator arm, each of the segments having an inner cam surface and an arcuate outer surface for engaging an inner surface of a precursor positioned over the mandrel, the outer surfaces each having a longitudinal profile wherein, at least a first segment has a different longitudinal profile from a second segment, while all segments have the same longitudinal profile length.