Patent ID: 8764398
Filing Date: 2014-07-01
Classification: B64C,F16F

Abstract:
1. A concentrated-mass device for reducing vibration generated by a rotorcraft lift rotor having a hub, the concentrated-mass device comprising: a main oscillating mass held radially in a horizontal plane by main springs within a casing suitable for being secured to the hub, the main oscillating mass being fastened to a top end of a rod, the rod being suitable for extending longitudinally along an axis of rotation of the lift rotor and of the hub so that a bottom end of the rod is hinged to a rotor mast of the lift rotor; a secondary oscillating mass suspended by secondary springs inside a recess in the main oscillating mass to oscillate along a vertical axis perpendicular to the horizontal plane, the secondary oscillating mass being constrained to move in translation together with the main oscillating mass in the horizontal plane; and a guide member to guide movement of the secondary oscillating mass inside the main oscillating mass wherein the main oscillating mass includes a bottom portion forming a box suitable for receiving the secondary oscillating mass and a top portion closing the bottom portion, the top and bottom portions being connected together by at least one fastener pin, and the guide member includes at least the fastener pin, and wherein the guide member includes at least one ball bushing formed in a guide orifice of the secondary oscillating mass about the fastener pin.