A first piece (1) that is adapted to be mounted in a stationary and rigid, removable and airtight manner, on a rigid annular collar (8) of a second piece (2) that has one end opening (3), the first piece comprising:
- a transverse wall (14) that can come into the opening (3);
- an annular wall that forms a skirt (15), having an interior surface (15a) that resists expansion under an external force in the direction of expansion;
- a hollow, toroidal holding chamber (45), adjacent to the interior surface (15a) of the skirt (15) and located toward the interior of the latter, deformable between a retracted state in which it is flattened on itself, and an expanded state in which it is broadened and filled with an inflation medium that is nearly incompressible;
- at least one entry/exit port (46) for the inflation medium in fluidic communication with the holding chamber (45) and accessible from the exterior of the skirt (15), able to allow the entry or exit of the inflation medium into or from the toroidal holding chamber (45);
- and
- a valve (52) that is located on the exterior of the skirt (15);
- wherein dimensions are selected, relative to those of the collar (8), in such a way as to be able, when the holding chamber (45) is in the retracted state, to be slipped onto or slipped off of the second piece (2) and when the holding chamber (45) is in the expanded state to be mounted in a stationary and rigid and airtight manner on the collar (8), with a mating part (47a) of an internal surface (47) of the holding chamber (45) being in airtight contact with a mating part (10b) of an exterior surface (10) of the collar (8);
- wherein:
- the transverse wall (14), with inherent sealing, is either continuous and solid or comprises at least one passage opening (23);
- the interior surface (15a) of the skirt (15) comprises:
- a cylindrical part (39a) of larger diameter adjacent to the transverse wall (14),
- a cylindrical part (39b) of smaller diameter that is separated axially from the transverse wall (14), between axial end parts (49, 50) from which an annular groove (48) is provided, with the toroidal holding chamber (45) being held by, and at least partially housed in, the annular groove (48), with the skirt (15) carrying the holding chamber (45), and
- an intermediate connecting part (39c) of tapered shape, adjacent to the part (39a) of larger diameter and to the part (39b) of smaller diameter;
- wherein the interior surface (15a) of the skirt (15) has a shape that is complementary with the exterior surface (10) of the collar (8), except for the annular groove (48), with the intermediate part (39c) coming into contact with the mating part (10c) of the exterior surface (10), the first piece (1) taken as a whole being able to be deformed by bending so that it can be slipped on and slipped off of the second piece (2);
- the first piece (1) being made of a material that is suited to the biopharmaceutical field, the first piece sealing with the second piece (2) when the transverse wall (14) is continuous and solid, or being connected with communication to the second piece (2) when the transverse wall (14) comprises a passage opening (23).