Mechanism for attenuating torque pulsations between an engine and a rotorcraft rotor driven by the engine

A mechanism for attenuating torque pulsations between an engine and a rotorcraft rotor driven in rotation by the engine, the mechanism comprising torsion means interposed in coaxial engagement between a drive shaft and a driven shaft for driving the rotor, wherein said torsion means comprise:

• a torsion shaft provided with coaxial engagement means with the drive shaft and with the driven shaft;
• an inlet shaft and an outlet shaft provided with coaxial engagement means respectively with the drive shaft and with the driven shaft;
• at least one lever system comprising a rigid lever arm extending radially to the torsion shaft and having the inlet and outlet shafts hinged thereto at spaced-apart points;
• and
• at least one mass carried by said lever arm at its free end radially distant from the axis on which the torsion shaft extends and from said hinge points of the inlet and outlet shafts.