Dynamic magnetic information storage or retrieval – Head – Head accessory
Reexamination Certificate
2000-08-21
2003-05-27
Heinz, A. J. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head
Head accessory
Reexamination Certificate
active
06570740
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to tape drives and, more particularly, to flanged tape guides having a wear resistant coating.
BACKGROUND
Information is recorded on and read from a moving magnetic tape with a magnetic read/write head positioned next to the tape. The magnetic “head” may be a single head or, as is common, a series of read/write head elements stacked individually and/or in pairs within the head unit. Data is recorded in tracks on the tape by moving the tape lengthwise past the head. The head elements are selectively activated by electric currents representing the information to be recorded on the tape. The information is read from the tape by moving the tape longitudinally past the head elements so that magnetic flux patterns on the tape create electric signals in the head elements. These signals represent the information stored on the tape.
Data is recorded on and read from each of the parallel tracks on the tape by positioning the head elements at different locations across the tape. That is, head elements are moved from track to track as necessary to either record or read the desired information. Movement of the magnetic head is controlled by an actuator operatively coupled to some type of servo control circuitry. Tape drive head positioning actuators often include a lead screw driven by a stepper motor, a voice coil motor, or a combination of both. The carriage that supports the head is driven by the actuator along a path perpendicular to the direction that the tape travels. The head elements are positioned as close to the center of a track as possible based upon the servo information recorded on the tape.
FIG. 1
illustrates generally the configuration of a tape drive
10
typical of those used with single spool tape cartridges. Referring to
FIG. 1
, a magnetic tape
12
is wound on a single supply spool
14
in tape cartridge
16
. Tape cartridge
16
is inserted into tape drive
10
for read and write operations. Tape
12
passes around a first tape guide
18
, over a magnetic read/write head
20
, around a second tape guide
22
to a take up spool
24
. Head
20
is mounted to a carriage and actuator assembly
26
that positions head
20
over the desired track or tracks on tape
12
. Head
20
engages tape
12
as tape
12
moves across the face of head
20
to record data on tape
12
and to read data from tape
12
. Tape guides
18
and
22
may be either roller guides or fixed guides. A conventional roller guide is shown in
FIGS. 2-5
. Referring to
FIGS. 2-5
, roller guide
28
includes disc shaped flanges
30
and an annular hub
32
. Flanges
30
and hub
32
may be machined as a single integral part or as three separate parts bonded together. In either case, flanges
30
function to keep tape
12
at the proper angle as it passes across head
20
. If the tape is presented to the head at too great an angle, then the read and write elements in the head may be misaligned to the data tracks. Flanges
30
are also needed to help keep tape
12
properly packed on take up spool
24
.
As shown in the detail of
FIG. 5
, conventional guides have a square corner
34
at the intersection of hub
32
and flange
30
. Corner
34
is usually formed at 90° or slightly greater than 90° (as indicated by angle &thgr; in FIG.
5
). If corner
34
is greater than 90°, then a small flat area
36
is often used to make it easier to measure the spacing between flanges
30
at corner
34
. Also, because it is difficult to make a perfectly square corner, a small undercut
35
is often machined into the corner of conventional guides to ensure a flat flange surface is presented to the tape at corner
34
.
As the tape is pulled over the guides, a film of air is created between the outside surface
33
of hub
32
and tape
12
. This film is often referred to as an air bearing. The air bearing allows the tape to move with low friction very rapidly between flanges
30
. Consequently, high frequency tape movement can occur when the edge of the tape bumps abruptly against the flanges
30
at corner
34
. The read/write head positioning systems have difficulty following such high frequency tape movement.
U.S. patent application Ser. No. 09/510,834 now abondoned discloses a tape guide in which the corner geometry between the flanges and the hub prevents the tape from abruptly bumping the flange. The tape guide of the '834 Application, which is incorporated herein by reference in its entirety, includes a hub, a pair of spaced apart parallel flanges extending out from the hub and a corner defining the intersection of the hub and each flange. The corners are configured to apply progressively more force to the edge of the tape as the tape moves around the corner from the hub toward the flange. For example, in one version of the tape guide of the '834 Application shown in
FIG. 9
, the corners are rounded. These corner configurations are designed to urge the tape more gently away from the flange at a much lower rate of acceleration. Guiding the tape in this manner allows for smoother movement of the tape which in turn allows the head positioning system to better follow the tape as it wanders back and forth between the guide flanges.
As shown in
FIG. 11
, the edge of the tape rides on the rounded corner of this new tape guide roller. Since the edge of the tape is somewhat abrasive, it may tend to wear the corners of the roller. This abrasive characteristic is more pronounced with unused tape because the slitting operation used to form the tape leaves the corner of the new tape relatively sharp.
As shown in FIG.
5
and described above, most conventional tape guide rollers have a small undercut or “relief” machined into the corner. Conventional rollers are usually made from aluminum with an electroless nickel coating. Aluminum is used because it is easily machined to a good surface finish and it is inexpensive.
Electroless nickel coating is much harder than aluminum and protects the surface against wear and corrosion. The nickel coating provides adequate protection for conventional rollers since the edge of the tape does not ride up on the corner. It has been observed, however, that nickel coating on the new rounded corner rollers of the '834 Application wears more quickly than is desirable. As the nickel coating wears the rounded corner, the tape may begin to bump more abruptly against an edge or edges worn into the corner.
SUMMARY
Accordingly, the present invention is directed to a tape guide like that described in the '834 Application in which the corner region is coated with a very hard material such as titanium aluminum nitride, tungsten carbide, silicon nitride, chromium nitride or diamond like carbon. Even thin coatings of such materials can be formed to exhibit a surface hardness greater than 10 gigaPascals (GPa). It is expected that coating materials applied to the roller that exhibit a hardness of at least 10 GPa will be sufficient to withstand tape wear in the corners of the roller for tape materials currently used in the manufacture of magnetic data storage tapes.
A tape guide constructed according to the present invention includes a hub, a pair of spaced apart parallel flanges extending out from the hub, and a corner defining the intersection of the hub and each flange. The corners are configured to apply progressively more force to the edge of the tape as the tape moves around the corner from the hub toward the flange. The corners are coated with a material that when applied to the roller exhibits a hardness of at least 10 Gpa. Suitable coating materials include titanium aluminum nitride, tungsten carbide, silicon nitride, chromium nitride or diamond like carbon.
REFERENCES:
patent: 4238088 (1980-12-01), Schoettle
patent: 4646177 (1987-02-01), Sanford
patent: 5542593 (1996-08-01), Skaar et al.
patent: 5638238 (1997-06-01), Kubota et al.
patent: 5-101316 (1993-04-01), None
patent: 50114202 (1993-05-01), None
patent: 5-151666 (1993-06-01), None
patent: 5-166113 (1993-07-01), None
patent: 6-139665 (1994-05-01), None
pate
Anderson James C.
Dinhobl Catherine
Haupt Martin
Hoerger Carl R.
Lindig Darin D.
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