Rotary actuator assembly for disk drive head positioner

Abstract

A rotary actuator assembly for positioning read/write heads in disk drive mass storage systems. The actuator assembly includes an actuator motor and one or more actuator arms secured thereto. The motor provides rotary motion of the arms, to move the heads. The stator magnet of the motor is an electromagnet wound on an arcuate core; a pair of elongate permanent magnets are attached to the rotor member, for coaction with the stator magnet. The rotor member has a U-shaped cross sectional area in a plane perpendicular to its axis of rotation; the permanent magnets are fixed to the outside, bottom corners of the U and the actuator arms are mounted across the open end of the U. The rotor is of a very small radius, to minimize inertia. The permanent magnets have a flat face facing the stator, with a channel running longitudinally down the middle, to minimize flux density variations in the permanent magnet-coil gap. The rotor balances the arm relative to the rotor's axis. The arms are of a substantially symmetrical tapered truss design, presenting low inertia; each is cantilevered to the rotor by one bolt which is passed through and pulls the arm against the rotors. Additionally, a spirol-type cylindrical spiral spring, received in a slot in the arm, prevents lateral slippage of the arm relative to the rotor. A pair of cantilevered leaf spring crash stops fixed to the stator decelerate the rotor at the ends of its range of travel.