A rotary actuator for an entry/exit device, in particular orientable and/or translatable door or ramp and the like in public transport vehicles, the actuator comprising a support and housing structure, an electric motor, a reduction unit connected to the motor, and a decoupler connected to the reduction unit, and comprising: - a first shaft having a tubular wall forming an inner cavity and one or more through holes, - a second shaft received in the inner cavity of the tubular wall rotatably about a rotational axis and forming one or more locking cavities in a position suitable to overlap with the through holes, - one or more locking members received in the through holes of the tubular wall and displaceable between a radially inner position in engagement with the through hole and with the locking cavity, preventing the relative rotation between the first shaft and the second shaft, and a radially outer position outside the locking cavities, allowing the relative rotation between the first shaft and the second shaft, - a control sleeve inserted on the tubular wall and axially slidable between a locking position and a release position, in which a control surface of the control sleeve faces the through holes and is shaped so that, when the control sleeve is in the locking position, the control surface locks the locking members in the radially inner position and, when the control sleeve is in the release position, the control surface allows displacing the locking members in the radially outer position, characterized in that the decoupler further comprises - a cam displaceable from a rest position to an operative position and at least one lever rotatable about a fulcrum and having a first end for engaging the control sleeve and a second end in contact with the cam so that the displacement of the cam from the rest position to the operative position pushes the lever second end in a direction transversal to the rotational axis and the lever first end pushes the control sleeve from the locking position along at least one initial stroke length towards the release position. - a first shaft having a tubular wall forming an inner cavity and one or more through holes, - a second shaft received in the inner cavity of the tubular wall rotatably about a rotational axis and forming one or more locking cavities in a position suitable to overlap with the through holes, - one or more locking members received in the through holes of the tubular wall and displaceable between a radially inner position in engagement with the through hole and with the locking cavity, preventing the relative rotation between the first shaft and the second shaft, and a radially outer position outside the locking cavities, allowing the relative rotation between the first shaft and the second shaft, - a control sleeve inserted on the tubular wall and axially slidable between a locking position and a release position, in which a control surface of the control sleeve faces the through holes and is shaped so that, when the control sleeve is in the locking position, the control surface locks the locking members in the radially inner position and, when the control sleeve is in the release position, the control surface allows displacing the locking members in the radially outer position, - a cam displaceable from a rest position to an operative position and at least one lever rotatable about a fulcrum and having a first end for engaging the control sleeve and a second end in contact with the cam so that the displacement of the cam from the rest position to the operative position pushes the lever second end in a direction transversal to the rotational axis and the lever first end pushes the control sleeve from the locking position along at least one initial stroke length towards the release position.