Stopper capsules and method for production thereof

A method for manufacturing a stopper capsule by an assembly means, the capsule forming a screw stopper for a container typically designed to contain alcoholic drinks and comprising a bottle with which a neck is provided with an outer thread and a tamper-proof ring, the capsule formed of an insert made of plastic material fixed together and axially with a shell comprising an outer head and a metallic outer skirt with a height H, said outer skirt having at least a substantially cylindrical part with a first height H1, a first diameter D1 adapted to the neck of the said container, and at least a radially expanded part with a second height H2, inscribed in a circle with second diameter D2 greater than first diameter D1, the method comprising the steps of:

• forming a blank of said shell from a metallic strip material, said blank comprising a skirt with the diameter D1 and a third height H′ greater than the height H;
• transforming said blank into said shell by making said radially expanded part, wherein said skirt of said blank is locally radially expanded over said second height H2,
• wherein said transforming step comprises the sub-steps of
• a) placing said blank in a shaping die forming a radial cavity with a profile similar to a profile of said radially expanded part, and
• b) introducing an expandable punch in said blank, and
• c) axially compressing said expandable punch by an axial displacement of a slide such that said expandable punch radially expands and forces a part of said skirt radially into contact with an inner wall of said radial cavity, said expandable punch having a sloping wall such that the local radial expansion of the expandable punch progressively extends in an axial direction, an initial force of said expandable punch applied upon a bottom part of said blank closest to said outer head.