Patent ID: 8573832

Claim:
A barrel for a self-winding timepiece including a drum of axis AA provided with an internal lateral wall having friction surfaces alternating with locking structures forming salient edges at the boundary of the friction surfaces and a mainspring forming a winding including an outer coil, which is friction coupled to said internal lateral wall and free to slip against said internal lateral wall in the event of overwinding of the mainspring, characterized in that said structures form notches including a flank at the inlet thereof that intersects the friction surfaces downstream relative to the direction in which said outer coil slips, forming a rounded salient edge, and in that said salient edge has a radius of curvature of more than 0.15 mm and in that said notches include a flank at the outlet thereof that intersects said friction surfaces upstream relative to the direction in which said outer coil slips, forming a salient edge whose radius of curvature is zero or comprised between 0.002 and 0.1 mm.