Disk and Hub Design for Improved Centering and Clamping
Original Publication Date: 2002-Jul-01
Included in the Prior Art Database: 2003-Jun-20
Disclosed is a design approach to rigidly mount a magnetic hard disk, either as a component for testing or as a permanent part of a hard disk drive assembly. This approach allows disks to be centered without adjustment. Further, it allows disks to be registered in angle with respect to the hub on which they are attached. Disks mounted on hubs inherently are not centered due to the required clearance between the disk ID hole and the hub. This leads to Repeatable Run-Out problems. This situation is compounded when a shock to the system causes the disks to slip in their clamp, introducing further off-center registration. Moreover, critical processes external to final drive assembly, such as servo pattern write, require precise centering, especially in magnetic imprinting or embossed servo pattern creation on plastic hard disk media. The invention is illustrated in cross section in the Figure below. The ID hole and clamping region on the disk are manufactured with a combination of a conical mating surface and an opposing flat mating surface. The hub includes a flat seat which mates with the flat portion of the disk, and a movable conical surface which is drawn into contact with the disk's conical surface during the clamping process. The flat region sets the plane in which the disk resides. The clamping process of drawing the 2 conical surfaces together, on the disk and hub, centers the disk and clamps it such that it cannot slip laterally. Although this could be applied to glass or metal substrates, it is most applicable to injection molded plastic substrates for hard disk manufacture, where the mating surfaces can be accurately introduced into the mold and produced without increased cost to the substrate. For such parts, the invention can be extended to other molded-in features, such as a key to set the azimuthal position of the disk. This could be important in cases of ex-situ servo writing and in schemes that use data or features on the disk to servo the spindle motor.