<p>The barrel (1) has a spring (7) accommodated between a drum (6) and a cover (8) and attached between the drum at its outer end and a shaft (3) at its inner end. The shaft is secured to pivot with a ratchet (2) around a pivot axis. A single-piece subset (10) is coaxial to the shaft and regroups the ratchet or/and a core (4). The core is provided with a flange (17) for limiting an axial clearance of the drum. The flange carries a driving unit (42) for freely and pivotingly driving the ratchet in axial manner according to the direction of the pivot axis. An independent claim is also included for a clockwork movement.</p>
