Importance

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Abstract

An actuator, including an electric motor (14) having a stator (16) and a rotor (17), in which the rotor (17) defines a bearing surface (20) having a non-circular profile, and a radially flexible annular sleeve (24) defines a facing bearing surface. The flexible sleeve (24) adopts a non-circular shape complementary to the profile of the bearing surface (20). The flexible sleeve (24) is restrained against rotation and is in toothed meshing engagement with a circular drive ring (26) at least two contact regions which are equidistantly spaced apart. The drive ring (26) is rotationally engaged with a screw and threaded sleeve assembly, such that rotation of the drive ring (26) drives the screw and sleeve assembly and causes extension or withdrawal of an output portion (28) of the screw and sleeve assembly for actuation. The actuator is operable such that rotation of the rotor (17) causes the flexible sleeve (24) to flex radially at each of the contact regions to generate a rolling wave which causes rotation of the contact regions and of the drive ring (26), and the drive ring (26) rotates at a reduced rotational velocity as compared to the rotational velocity of the rotor (17).

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First Claim