Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
2000-10-10
2003-07-15
Evans, Jefferson (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
Reexamination Certificate
active
06594118
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to magnetic recording devices in general and, more specifically, to an apparatus for positioning a magnetic head relative to the tracks of a tape.
2. Description of Related Art
High-density recording on multiple tracks of a magnetic tape is known. In certain arrangements, parallel tracks extend along a longitudinal direction of the magnetic tape. A magnetic tape is moved transversely across the tape so that a read and/or write gap of the magnetic head is moved in proximity to the desired track. During recording or playback, the head needs to stay in position as the tape moves in a longitudinal direction across the read/write gap.
There continues to be increasing demands for greater storage capacity, which has jumped from a few gigabytes to several hundred gigabytes. Magnetic tape systems are still among the most economical devices for storing data.
Existing tape storage systems with a few gigabytes of capacity have very limited track densities and bit densities. In those existing systems, during read and/or write functions, the head positioner locates the head at the track's centerline and the read/write process continues without any adjustment, even should the head gap become offset from the track's centerline. Some existing tape storage systems contain a mechanism that precisely allows the read/write head to be located precisely at the track's centerline as the tape at the beginning of the read/write process. Once the read/write process begins, there is no correction if an offset should arise between the head and the centerline of the track.
To increase storage capacities to meet increased demands, track density, which is the number of tracks per distance (e.g., inches), should be increased. As track density increases, the track pitch and width decrease. For proper read/write operation, the magnetic head must stay at, or very near, the centerline of the track.
Due to reduced track pitch, improvements to the head positioner are needed to minimize the offset between the head and the centerline of the track. One important feature of such a positioner is that it allows the drive to monitor the head-to-track relationship. If the drive determines that the head and track are offset, then the positioner corrects the relative position to maintain the relationship between the head and the centerline of the track.
There are two basic types of head positioners—open loop positioners and closed loop positioners. Conventional open loop positioners do not have a mechanism for ensuring that the head stays in a close relationship with the centerline of the track. An open loop positioner moves the magnetic head to a track location and does not move the magnetic head again, even if the head becomes offset with respect to the track centerline. Such open loop positioners, or coarse positioners, are often found in tape systems having relatively low track densities.
Closed loop positioners are often used in tape systems having higher track densities. In high density tape systems, the tape may wander in the lateral direction as it moves in the longitudinal direction, which results in an offset between the magnetic head and the track centerline. To avoid these types of problems, tape cartridges for high density tape drives are preformatted with information, often called servo information, that is used to maintain the correct lateral position of the tape with respect to the magnetic head. The servo information provides the system with feedback to communicate to the system the continuous position of the tape. The servo information can alert the system about the occurrence of an offset. Based on the information that an offset has occurred, the head is moved by a positioner to the centerline of the track so that the read/write operation can occur properly.
Closed loop positioners use “fine positioners” to move the head during the read/write operation. These fine positioners are used to maintain the position of the head at the centerline of the track under a closed loop servo control using the preformatted servo information on the tape. Fine positioners include a head-carriage assembly, which comprises a magnetic head, a top head carriage, a voice coil motor, and a bottom head carriage.
SUMMARY OF THE INVENTION
There is a need for an improved head positioner that allows for increased track densities.
There is a need a need for an improved head positioner that ensures that the magnetic read/write head is at the tape centerline throughout the read/write operation.
There is a also a need for a suspension system that contains a flexure that ensures that the natural frequencies of the mass-spring system are typically lower than 200 Hz.
There is a further need for an improved head positioner suspension system that contains a flexure that maintains a stiffness at a minimum level so that the current required to move the magnetic head assembly in a transverse direction is low.
These and other needs of the invention are met by an embodiment of the invention which provides a head positioning apparatus for positioning a magnetic head in a multi-track tape drive. The apparatus comprises a voice coil having an interior space. A movable carriage supports the magnetic head and the voice coil and a center magnetic pole is housed in the interior space of the voice coil. A pair of outer magnetic poles are positioned opposite each other about an exterior of the voice coil. First and second flexures are each attached at opposing ends to the outer magnetic poles and in a central portion to the movable carriage.
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patent: 2000-36111 (2000-02-01), None
Decot James M.
Nayak Ashok B.
Evans Jefferson
Seagate Removable Storage Solutions LLC
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