The invention relates to a device for rotating at least one mandrel (4a, 4b) coupled to a secondary reduction gear (10) that can in turn be coupled to a primary reduction gear (8) and supplies a torque to the mandrel, wherein: the primary reduction gear is driven by at least one driving motor (7a, 7b), the primary and secondary reduction gears (10) are mechanically similar and can be coupled via at least one torque transmission means rotated by the primary reduction gear along a rotation axis (ax), the torque transmission means (9) includes at least one coupling tube with two section ends. Furthermore, in the assembled configuration, the primary and secondary reduction gears define a unitary assembly integrally encapsulating the torque transmission means that can be removed from the unitary assembly in the permanent assembled configuration through an opening (04) of the unitary assembly formed in at least one of the walls of the primary and secondary reduction gears opposite the section ends of the torque transmission means.