Dynamic magnetic information storage or retrieval – Record medium – In container
Reexamination Certificate
1995-09-14
2001-04-10
Crane, Sara (Department: 2811)
Dynamic magnetic information storage or retrieval
Record medium
In container
C360S099010, C360S135000
Reexamination Certificate
active
06215620
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to data storage diskette technology and, more particularly, to a hub for supporting a circular sheet of magnetic media in a data storage diskette.
DISCUSSION OF RELATED ART
Existing two-megabyte, three and one-half inch (89 mm) form factor data storage diskettes generally include a diskette housing, a circular hub mounted within the housing, a circular sheet of magnetic media mounted about the hub, one or more media access windows, and a shutter mechanism for covering and uncovering the media access windows. The hub includes a central hub member and a flange extending radially outward from the central hub member. The sheet of magnetic media has a circular aperture defining an inner diameter.
A portion of the sheet of magnetic media at the inner diameter is mounted on the flange of the hub such that the sheet is substantially centered about the central hub member. In existing two-megabyte, three and one-half inch (89 mm) data storage diskettes using magnetic media, the hub is sized to have an overall diameter of approximately 29.0 mm. Specifically, the central hub member has a diameter of approximately 24.9 mm, and the flange contributes approximately 4.1 mm to the overall hub diameter.
A portion of the hub extends through a circular aperture in the diskette housing. During read and write operations, a motor in the diskette drive turns the hub to rotate the sheet of magnetic media. The rotating sheet of magnetic media is accessed by opposing magnetic heads within the data storage diskette drive via the media access windows. Each of the magnetic heads performs read and write operations relative to one side of the sheet of magnetic media. The magnetic heads are aligned parallel to one another to define a small gap. The sheet of magnetic media extends into the gap and is held between the magnetic heads. The magnetic heads are translated radially across the sheet of magnetic media to access different regions of the sheet at which data is stored.
SUMMARY OF THE INVENTION
The present invention is directed to a hub for supporting a circular sheet of magnetic media, and to a data storage diskette incorporating such a hub. A hub and data storage diskette, in accordance with the present invention, may be used with sheets of magnetic media having conventional data storage capacities on the order of two megabytes, but are particularly useful with sheets of magnetic media configured for higher data storage capacities on the order of, for example, one-hundred and twenty megabytes. The higher data storage capacities may be realized, for example, by the use of optical tracking between the diskette drive and the sheet of magnetic media. An example of a data storage diskette using optical tracking is disclosed in U.S. Pat. No. 4,961,123.
In accordance with the present invention, the data storage diskette may comprise, for example, a diskette housing, the diskette housing conforming to a three and one-half inch (89 mm) diskette form factor, a sheet of magnetic media contained in the diskette housing, the sheet of magnetic media having a circular aperture, and a hub mounted in the diskette housing, the hub receiving a portion of the sheet of magnetic media such that the circular aperture of the sheet of magnetic media is substantially centered about the hub, wherein the hub has a diameter of less than approximately 29.0 mm.
The hub and data storage diskette of the present invention have been conceived in view of the discovery of a problem with the use of existing hubs in data storage diskettes having higher data storage capacities. The hub and data storage diskette of the present invention also have been conceived in view of identification of the source of the problem and, ultimately, the discovery of a solution to the problem. A description of the problem, source, and solution follows.
In general terms, the problem is inconsistent read-out amplitude along the entire radius of the sheet of magnetic media. In data storage diskettes configured for higher density data storage, data is stored in regions of the sheet of magnetic media located more closely to the inner diameter of the sheet, relative to existing two-megabyte diskettes. Storage of data more closely to the inner diameter helps add to the data storage capacity of the diskette. When magnetic heads are used to access regions of the sheet of magnetic media located near the inner diameter, however, the amplitude of signals read from such regions can significantly decrease. The decreased amplitude decreases the signal-to-noise ratio of the signal, and can potentially result in bit errors in the data read from the diskette.
The source of the decreased amplitude is a misalignment that occurs near the inner diameter between the gap defined by the magnetic heads and the sheet of magnetic media. The magnetic heads define a read/write axis that ideally is oriented perpendicular to the sheet of media at the point of the read/write operation. This perpendicular relationship should remain substantially constant as the magnetic heads are translated radially inward and outward across the sheet of magnetic media. In other regions, the sheet of magnetic media is flexible enough to undergo slight bending sufficient to preserve the perpendicular relationship. When the magnetic heads are disposed near the inner diameter, however, they are situated more closely to the point at which the sheet is bonded to the hub flange. The region of the sheet radius extending from the bond point to the magnetic heads is shorter, and tends to be less flexible than other regions. As a result, the regions near the inner diameter are not flexible enough to adequately align with the gap, and the perpendicular relationship between the read/write axis and the sheet is not satisfied.
The solution, in accordance with the present invention, is a modified hub. Specifically, the hub can be modified to have a smaller diameter than existing hubs. The hub diameter can be reduced by, for example, reducing the size of the hub flange. With a smaller diameter hub, the inner regions accessed by the magnetic heads are disposed further from the bond point of the sheet to the hub flange. The added distance between the bond point and the read/write access point enables the inner regions to be more flexible. The added flexibility enables the sheet of magnetic media to more readily be bent to align with the gap defined by the magnetic heads. The enhanced alignment enables the read/write axis to be perpendicularly aligned with the sheet of magnetic media in the inner regions, thereby maintaining signal amplitude in such regions.
In addition to enabling signal amplitudes to be maintained, the reduced hub diameter produces other advantages. For example, the reduced hub diameter results in a shorter flange. The shorter flange is structurally strengthened, enabling it to be constructed with a reduced thickness, if desired. The reduced thickness contributes to savings in the amount of material required to form the hub, and thus the cost of the hub. The reduced amount of material reduces the mass of the hub, enabling the hub to be rotated with less torque. Less torque requires less power from the motor, conserving battery resources in mobile computers. The reduced hub diameter also spaces the innermost data storage regions of the sheet of magnetic media further from the bonding point. The increased spacing reduces the contamination of the innermost data storage regions with defects resulting from bonding the sheet to the flange. As a result, data integrity in the innermost regions can be maintained. Further, the enhanced flexibility of the sheet near the inner diameter reduces wear on the sheet during use, resulting in increased durability.
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patent: 4961123 (1990-10-01), Williams e
Dunbar William M.
Laanen Peter Van
Skelcher Wayne L.
Swanson Leonard R.
Crane Sara
Imation Corp.
Levinson Eric D.
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