A cable-pull actuation system (4) for a parking brake, comprising - a body (8) which houses electric motor means (12), a rod (16), adapted to operate along an actuation direction (X-X), at a first end (20) thereof, an actuation member (24) of a drum brake (28) and/or of a parking brake, - transmission means (44) which operatively connect the electric motor means (12) to a second end (48) of the rod (16) which is translationally integral with a screw (52), having a thread (56), - wherein said screw (52) is engaged, by means of the thread (56), with a nut screw (60) rotationally actuated by said transmission means (44), - wherein pre-loading means (64) are provided, acting in contrast on the screw (52), said pre-loading means (64) being compressively pre-loaded by a pusher (68) so as to exert a pre-load traction on the rod (16) to offset variations of load on the rod (16), - wherein the pre-loading means (64) are configured to exert a thrust action on the rod (16) following the annulment of axial clearances, along the actuation direction (X-X), between the nut screw (60) and said body (8), so as to allow an incremental compression of the pre-loading means (64) with respect to the pre-load value.
展开▼
