Rotary actuator assembly for disk drive head positioner

In a magnetic disk storage device which includes a magnetic disk medium, spindle means for rotating the disk medium about a spindle axis that is perpendicular to the plane of rotation of the disk medium, a base for supporting the spindle means, and at least one actuator arm having a pivotal end at one extremity and a head supporting end at the other extremity for supporting at least one transducer means mounted thereon, said arm being pivotally movable through a limited angle of rotation about a pivotal axis that is parallel to said spindle axis, a motor for connection to said actuator arm comprising:

• a stator mountable on said base and including a stator core that is arcuately shaped to substantially embrace a rotor axis that is coincident with said pivotal axis, said stator including opposed shaft receptors aligned with said rotor axis;
• a rotor having opposed shaft members supported by said shaft receptors and being rotatable about said rotor axis through a limited angle corresponding to the pivotal movement of the actuator arm;
• at least one permanent magnet fixed to the rotor, the area of travel of the permanent magnet being embraced by said stator core during rotational movement of the rotor throughout the angle of rotation;
• at least one electromagnetic coil fixed to the stator core;
• said permanent magnet and said stator core being formed to produce a substantially constant electromagnetic force throughout the angle of rotation of said rotor;
• the rotor including coupling means disposed intermediate said opposed shaft members for coupling to said actuator arm thereby to effect motion of said arm to position said transducer means over said magnetic disk medium upon movement of said rotor.

An assembly for moving a read/write recording head over the surface of a magnetic data storage medium, the assembly including spindle means for rotating said recording medium about a spindle axis that is perpendicular to the plane of rotation of the recording medium, the spindle means having opposed axial ends, and medium enclosure means having opposed mating members, each member being a unitary rigid structure for encasing said recording medium and for supporting each of the opposed ends of the spindle means on respective opposed members thereof to allow rotation of the spindle means but to prevent radial displacement thereof, the assembly further comprising:

• an actuator arm having a pivotal end at one extremity and a head supporting end at the other extremity for supporting the head;
• an actuator motor comprising a rotor for pivotally moving the arm about a rotor axis through a predefined limited angular range and a cooperating stationary stator, the rotor including a pair of permanent magnets, the stator having opposed shaft receptors for supporting the rotor wherein each of the opposed shaft receptors is secured to a respective member of said medium enclosure means, thereby to constrain the rotor axis in fixed parallel relation to the spindle axis, said stator including at least one electromagnetic coil for energization to produce an electromagnetic force between the stator and the rotor, to produce movement of the rotor about said rotor axis;
• the rotor including
• an elongated member having a substantially U-shaped cross-sectional area in the plane normal to the rotor axis;
• a pair of aligned stub shaft members located on said rotor axis, one disposed at each end of and connected to the elongated U-shaped member, for use as a shaft for rotation and support of the U-shaped member within the shaft receptors of said stator;
• the end surfaces of the open side of the U-shaped member providing mounting surfaces located intermediate said stub shaft members for securing the arm thereagainst;
• the actuator arm having a mounting surface at the pivotal end thereof adapted to be secured to the U-shaped member of the rotor;
• the permanent magnets of the rotor being of elongated configuration, disposed parallel to the motor axis and being fixed to the outside of the U-shaped member;
• the stator including a stator core that is arcuately shaped to substantially embrace said rotor axis and the area of travel of said permanent magnets and a stator coil wound about the stator core, and said permanent magnets being formed for producing a substantially constant magnetic flux density between said permanent magnets and said stator core over the rotational range of the rotor.