The invention relates to a method for manufacturing a covering structure for a cardboard package comprising a tubular body made up a cardboard material. The covering structure comprises a flat assembly of three materials: (1) a cellulosic material covered with a reactivatable barrier material over the face thereof oriented towards a safety membrane, making up a lid cardboard, (2) a laminating part arranged between said lid cardboard and the safety membrane, with a shape conjugated to the shape of the opening of the tubular body, made from paper, or paper whereof the face oriented towards said lid cardboard is coated with a material having barrier and sealing properties, and (3) a safety membrane, made up of a paper coated with at least one reactivatable barrier material on the surface thereof not oriented towards the laminating part.

An extensible bearing element of a tool for sealing a bottom or a lid of a cardboard package on a body of said package has a generally polygonal shape and a cross-sectional profile. The bearing element is formed by two parallel extension sections extending along an extension direction, each connected, at one of their ends, to a bearing section. The extension sections and the bearing section define an inflation cavity. The extension sections are configured to extend along the extension direction when the bearing element is inflated. The bearing section comprises a substantially flat, free bearing surface that contacts the package body. The bearing surface extends along a plane substantially normal to the extension direction. The bearing section further comprises, at the junctions with the extension sections, beveled release portions. An inflation device comprising such an extensible bearing element is also described.

The invention relates to an extensible bearing element (28) intended to be arranged in a tool for sealing a bottom or a lid of a cardboard package on a body of said package, with a generally polygonal shape.

The extensible bearing element (28) has a cross-sectional profile comprising two parallel extension sections (36) extending along an extension direction (E), each connected, at one of their ends (36E), to a bearing section (38), such that the extension sections (36) and the bearing section (38) define an inflation cavity (30).

The extension sections (36) are configured so as to extend along the extension direction (E) during the inflation.

The bearing section (38) comprises a substantially flat free bearing surface (40), configured to come into contact with the package body, the bearing surface (40) extending along a plane substantially normal to the extension direction (E).

The bearing section (38) further comprises, at the junctions with the extension sections (36), beveled release portions (42).

The invention also relates to an inflation device (6) comprising such an extensible bearing element (28).