Arrangement for balancing of a body rotatable about an axis

Arrangement for balancing of a main mass (14) having an imbalance and rotating about an axis (18), said balancing being made by means of balancing masses (23;24) which are relatively freely moveable with respect to the main mass (14) and disposed in at least one closed path (22) symmetrically positioned around said axis (18), said main mass (14) being adapted to be rotated at speeds both below and above a critical speed and the path (22) being connected with the main mass (14) so as to rotate in synchronism therewith, locking means (34,36;42,43) being provided for locking the balancing masses (23;24) relative to the path (22) at rotating speeds below the critical speed and for releasing the balancing masses (23;24) for movement relative to the path (22) at rotating speeds above the critical speed, wherein the locking means (34,36;42,43) are operable to cause the balancing masses (23;24) to automatically take a locking position (A', B', C') provided for each balancing mass (23;24) when the main mass (14) is rotated at speeds below the critical speed, said locking positions (A', B', C') being evenly interspaced along the periphery of the path (22).