Dynamic magnetic information storage or retrieval – Head – Head accessory
Reexamination Certificate
1996-06-14
2001-09-25
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Head accessory
C226S196100
Reexamination Certificate
active
06295181
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a stationary tape guide with improved flight characteristics, and more particularly, to a tape bearing surface that reduces tape surface contact near the edge, while minimizing variation in cross-web tension, and a method of making the same.
BACKGROUND OF THE INVENTION
Tape surface damage near the edge of the tape is a leading cause of data loss and tape cartridge failure. Additionally, tape contact with tape guides can contribute to debris generation and to a malformed tape pack. Large radius stationary cylindrical tape guides have been frequently used to transport tape with minimal physical tape-to-guide contact, and in particular, to reduce tape surface contact near the edge with the tape guide.
The use of a flying tape guide helps to reduce the tape-to-guide friction and consequently tape wear. A flying tape guide causes the tape to fly (at specific tape speed and tension) over the bearing surface of the tape guide. When operated at the designed speed and tension, there is almost no physical contact between the moving tape and the stationary tape guide. At lower tape speeds or higher tape tension, however, tape lift is reduce and there is generally tape surface contact pressure along the tape edges.
Flying tape guides, however, do not necessarily prevent tape surface contact at the edges.
FIG. 1
is a schematic end view of a flat flying tape guide
300
. The cross-web tension is generally uniform over the length of the guide
304
. Under constant tape tension, however, the spacing between moving tape
302
and stationary tape guide
304
is not uniform across the width of the tape
302
. The spacing along edges
306
,
308
of the tape
302
is generally less then the spacing near the center
310
due to atmospheric pressure acting on the tape edge
306
,
308
, anti-clastic tape deformation and side leakage
312
of the air bearing surface. The problem of tape edge damage will become more severe as the magnetic tape industry moves to thinner media where the cross-web bending rigidity of the tape is significantly reduced.
In both belt-driven and hub-driven tape cartridges, the allowable tape speed and storage capacity (i.e., data density) increase with the accuracy at which the tape is coupled with the read/write heads. Therefore, any solution to the problem of tape edge damage that alters tape-to-head interface will likely have a direct impact on tape drive performance. For example, tape cartridges must meet minimum tape tension specifications while simultaneously maintaining minimum drive force specifications. The tape tension must not fall below a certain level as the tape passes from reel to reel. Otherwise, contact between the read/write head and the tape will be insufficient. The minimum achievable tape tension should be sufficiently high to ensure proper cartridge operation. Similarly, the maximum required frictional drive force should be as low as possible to enhance cartridge operation within the power limitations of the drive motor. Thus, there is a limitation on the frictional drive force. The frictional drive force is that portion of the drive force which affects power loss at the interface between the backside of the tape and the tape guide. Minimizing the frictional drive force and improving tape tracking can be accomplished by minimizing the friction at the interface between the tape and the tape guides, which accounts for approximately one-third of the drive force in a data cartridge.
SUMMARY OF THE INVENTION
The present invention is directed to a stationary tape bearing surface with reduced tape surface contact near the edge, while minimizing variation in cross-web tension. The present invention is also directed to a stationary tape guide and a tape cartridge containing the present tape bearing surface. The present invention is also directed to a method of making a tape guide with these characteristics.
The stationary tape bearing surface for a tape guides has a tape surface piece with a top surface. The top surface has a longitudinal axes defining a tape path and a lateral axis perpendicular to the longitudinal axis. In one embodiment, the top surface defines a convex shape extending along the lateral axis having at least two distinct radii.
The two distinct radii include a first radii proximate a center of the lateral axis and a second radii proximate edges of the lateral axis. The first radius is preferably greater then the second radius. The first radius preferably has a height in the range of 6.0 to 8.0 microns. The second radius preferably has a height in a range of about 19 to 21 microns. The tape surface piece may be cold rolled stainless steel or chrome plated brass. In an alternate embodiment, the top surface defines a convex shape with a single radius of curvature extending along the lateral axis having a height of between 12.7 to 25.4 microns (0.0005 and 0.001 inches), more preferably between 12.7 and 20.3 microns and most preferably between 17.8 and 20.3 microns. In the preferred embodiment, the top surface is configured so that a self-acting air bearing is formed at the interface between the tape and the bearing surface.
The present invention is also directed to a tape guide including a stationary, convex tape bearing surface. The present invention is also directed to a tape cartridge including the stationary, convex tape bearing surface.
The present invention is also directed to a method of forming a tape bearing surface for a tape. A tape surface piece having a top surface with a longitudinal axis defining a tape path and a lateral axis perpendicular to the longitudinal axis is provided. The top surface is formed into a convex shape extending along the lateral axis having at least two distinct radii. The at least two distinct radii include a first radii proximate a center of the lateral axis and a second radii proximate edges of the lateral axis The first radius is preferably greater then the second radius.
In an alternate embodiment, the tape bearing surface defines a single radius having a height of between 12.7 to 25.4 microns (0.0005 and 0.001 inches), more preferably between 12.7 and 20.3 microns and most preferably between 17.8 and 20.3 microns.
The method also includes the steps of stamping the tape surface piece from sheet stock. The stamping process typically forms a burr edge along a bottom surface of the tape surface piece. The bottom surface of the stamped tape surface piece is then cold rolling to form the tape bearing surface. The step of forming the top surface typically involves using a calendering roller.
As used herein:
Curved profile or crown refers to a cross-sectional profile perpendicular to the tape path.
Self-induced Air Bearing (also known as hydrodynamic lift) refers to a layer of air or air film carried by the tape into the interface between the tape and the tape guide, absent any external artificial source of air pressure.
REFERENCES:
patent: 3393849 (1968-07-01), Hass
patent: 4114751 (1978-09-01), Nordin
patent: 4736904 (1988-04-01), Schoettle et al.
patent: 5282105 (1994-01-01), Eaton et al.
patent: 5299756 (1994-04-01), Hu et al.
patent: 5358193 (1994-10-01), Madsen et al.
patent: 5377927 (1995-01-01), Erickson et al.
patent: 5490029 (1996-02-01), Madsen et al.
patent: 5513815 (1996-05-01), Erickson et al.
Erickson Leif O.
Fahimi Aboutorab S.
Richards Durkee B.
Imation Corp.
Klimowicz William
Levinson Eric D.
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