The left and right sideblades are hinged to the mainblade about vertical axes, and can pivot each through 180°. The sideblades are rotated by means of left and right hydraulic rotary actuators. The actuator includes a piston formed with helical splines, which drive a rotor sleeve of the actuator to rotate in a single-plane-circle when the piston is driven axially. The journal bearings in the rotary actuator are supplemented by bearings provided in a coaxial lower hinge, which are of much greater journal capacity than the bearings in the rotary actuators. The lower hinge protects the hydraulic rotary actuator from shocks due to the sideblade impacting against a kerb.
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