Methods of making metal can ends with plastics closures

A method of forming a tear-opening can end comprising steps of providing a sheet metal blank having inner and outer opposite surfaces with the inner surface having a coating of polymeric material thereon;

• forming the blank into a can end having a peripheral flange, a peripheral wall inboard of the peripheral flange and a central panel inboard of the peripheral wall;
• piercing the central panel to form an aperture by passing a punch through the central panel in conjunction with an associated die;
• forming a laterally projecting burr at a terminal edge of the aperture coincident with the performance of the piercing step;
• forming a wall portion of the central panel contiguous the aperture into an opening-defining flange by urging a punch against the outer surface of the contiguous wall portion and moving the punch in a direction from the outer surface toward the inner surface whereby the opening-defining flange projects in the outer-to-inner surface direction and generally transverse to the plane of the central panel., providing a mould cavity defined by cavity portions in opposing mould bodies with each cavity portion having a peripheral wall appreciably outboard of the opening-defining flange and an axial wall axially outboard of the outer surface and the terminal edge, respectively, of an associated can end located between the mould bodies, locating a can end between the mould bodies;
• closing the mould bodies such that the can end is positioned with the opening-defining flange thereof inboard of the mould bodies peripheral walls, the outer surface spaced from an axial wall of one of the mould bodies and the terminal edge closely spaced from the axial wall of the other mould body;
• injecting polymeric material into the cavity and upon the can end therein to form a polymeric closure including interior and exterior flanges upon the inner and outer surfaces and outboard of the opening-defining flange with a plug portion therebetween and a residual portion adjacent the opening-defining flange terminal edge;
• the polymeric material of the closure being chosen from a group including nylon or polypropylene and the polymeric material of the inner surface coating being similar thereto thereby effecting in situ bonding, fusion, and hermetic sealing engagement between the closure interior flange and the inner surface coating during the performance of the injecting step;
• and the thickness of the residue portion being in a range of 0.125 mm to 0.5 mm.