Stacked, symmetrical, flexure pivot bearing
Original Publication Date: 2000-Aug-01
Included in the Prior Art Database: 2003-Jun-19
This invention reveals a new pivot design that relies on flexures to provide rotational motion. Three of these flexure bearings are stacked to provide sufficient rotation range of motion for use in a hard disk drive actuator. Each flexure bearing is a one piece design. The design is symmetrical along three orthogonal axes to prevent the creation of actuator resonances arising from any asymmetric boundary condition. The rotary flexure is a monolithic device, machined from a solid metal rod. It is designed for high radial and axial stiffnesses, low rotational stiffness and a long fatigue life. The quad-foil rotary flexure has four radial, equally spaced thin plates that extend from and sleeve to the inner quad-lobed support, see figure. By minimizing the distance from the inner terminus of the flexures to the rotational axis the torsional stiffness is made as small as possible. The plates can be notched to increase torsional flexibility. A constrained layer damping material may be placed on the plate's surface to dampen vibrations. The device flexes to provide rotation about a single axis through a range of +/-12 degrees. The four lobes of the inner support are joined at the rotation axis to provide an extremely rigid attachment for the flexure elements, thus allowing high radial and axial stiffnesses. To reduce the concentration of stresses, generous fillet radii were incorporated at the inner and outer ends of the fins. The quad-lobed support rotates relative to the outer cylinder on the flexures to create the pivot motion. To prevent exceeding the material's fatigue limit and to prevent disk drive slider excursions beyond the data and load/unload zones the total rotational range is defined by polymeric crash stops placed in the pivot. To increase overall rotational range to 24 degrees, a plurality of flexures may be attached to each other in an end to end configuration. Circular coupling plates are adhesively bonded to the sleeve of the one pivot to the quad-lobed support of another bearing. Tapped holes in the quad-lobes receive threaded fasteners used to attach the pivot to the base casting and the top cover. The actuator E-block attaches to the sleeve of the inner pivot.