1. Field of the Invention
The present invention generally relates to the winding of tape around reels in a tape drive and, more particularly, to an integrated reel hub and motor shaft assembly and fabrication method therefore that reduce radial and axial run-out of the tape relative to the reel hub to limit position errors and head-to-tape spacing complications.
2. Relevant Background
Tape drives have been widely employed in industry for over thirty years due to their ability to store large amounts of data on a relatively small and inexpensive removable format. Typically, tape drives use a storage tape having a thin film of magnetic material which is wound between a pair of tape reels as data is transferred to or from the tape media via a read/write tape head assembly. In one arrangement, one of the reels (e.g., the “take-up” reel) is part of the tape drive while the other reel (e.g., the “cartridge” reel) is part of a removable cartridge. Upon insertion of the cartridge into the tape drive, the storage tape on the cartridge reel must be coupled to the take-up reel of the tape drive (e.g., via respective leaders). After coupling, the tape is unwound from the cartridge reel, moved past the tape head assembly and wound onto the take-up reel via a drive motor. Next, the tape is unwound from the take-up reel, moved past the tape head assembly and wound onto the cartridge. Subsequently, the storage tape must be uncoupled from the take-up reel, prior to removing the cartridge from the tape drive. In another arrangement, both reels are part of a cassette which is inserted into a tape drive and driven by a drive motor.
More recently, a popular trend is towards multi head, multi-channel fixed head structures with narrowed recording gaps and data track widths so that many linear data tracks may be achieved on a tape medium of a predetermined width, such as one-half inch width tape. To increase the storage density and reduce access time of magnetic tapes, data tracks on the tape are arranged with greater density and the tape is streamed by a tape head at increasingly faster rates.
However, increased storage density and linear speed can lead to higher error rates when reading and/or writing on the tape due to both “axial” and “radial” run-out. Axial run-out refers to lateral or transverse motion of the tape on the reel assembly relative to a head assembly in a tape drive as the tape streams by the head assembly, and is generally defined as the peak-to-peak distance of the undesirable movement (in-plane) of the tape perpendicular to its prescribed longitudinal direction of motion past the head assembly. Radial run-out refers to tension variations in the tape in a direction perpendicular to the axis of rotation of the reel assembly.
Often, axial and radial run-out are caused by various fabrication and assembly tolerances in the engagement between a reel assembly and a corresponding drive assembly (e.g., reel driver, drive shaft). If the engagement is imprecise because of an offset (e.g., in the axial and/or radial directions), the tape path may vary resulting in excess lateral tape motion and/or tension variations in the tape. Both axial and radial run-out can cause errors in the reading and/or writing process by limiting the degree to which a head assembly can locate a particular data track. As a result, axial and radial run-out and the ability to compensate for the same are major limiting factors in determining the minimum width of a track and the minimum spacing between tracks on the tape. As run-out is reduced, tracks may be stored more densely on the storage tape and storage tape capacity can be increased.
The common approach to limiting axial and radial run-out is by way of improving the fabrication and/or assembly tolerances of and/or between the reel and motor assemblies to allow for a more precise engagement between the same. In some arrangements, the reel and drive assemblies have corresponding apertures through which fasteners can be inserted and/or threaded to limit relative movement. In other arrangements, corresponding interlock components (e.g., teeth, splines, and the like) may be disposed on the reel and drive assemblies and which may respectively interlock to limit relative movement between the reel and drive assemblies. However, even relatively small mismatches in the matched features or teeth can cause run-out control and axial location difficulties. Furthermore, less than full engagement between the reel and drive assemblies can cause various types of tape loading or tension errors to occur and possibly lead to increased lateral tape motion. In this regard, the tolerance “stack-up” between the reel assembly, the drive assembly, and the like can cause various types of errors in reading and/or writing processes and hinder the pursuit of increased magnetic tape data density.