Stirring device with a shaft, adapted to be mounted in a fluid-mixing bioreactor, and method for assembling a stirring device

A method for assembling a stirring device, the method comprising:

• providing a rotatable drive shaft extending along a longitudinal axis, including a rod having a mounting area on an outer cylindrical surface of the rod;
• providing a hub and an impeller assembly that define an agitating element, the agitating element extending around an inner space delimited by an annular side wall of the hub, the impeller assembly comprising a set of generally radially extending blades;
• mounting a sleeve of tubular shape on the rod to encircle the mounting area, so that the sleeve forms a coupling sleeve receiving the drive shaft therethrough and is directly rotationally coupled to the rod of the drive shaft;
• inserting and engaging the sleeve in the inner space through an axial insertion opening of the annular side wall, so that the hub is directly rotationally coupled to the sleeve, whereby the agitating element is indirectly rotationally coupled to the rod of the drive shaft via the sleeve in an assembled state of the sleeve, in which the sleeve is sandwiched between the mounting area of the rod and the agitating element;
• wherein engaging the sleeve in the inner space comprises:
• fastening the sleeve to the hub, by a fastening arrangement of the sleeve, which comprises one or more abutment members to prevent axial movement between the hub and the sleeve in a locked configuration in which the one or more abutment members are engaged with complementary abutment means formed on the annular side wall so that the sleeve is fixedly coupled to the hub, axially and rotatably, and
• guiding and maintaining a concentric arrangement of the hub and the sleeve, using a guiding surface formed either by an inner surface of the annular side wall, or an outer surface of the sleeve, the guiding surface being provided with a progressive reduction of cross section with increased distance, in the locked configuration, from the axial insertion opening.