Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
2000-10-17
2004-03-02
Hudspeth, David (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
C360S077120
Reexamination Certificate
active
06700729
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a tape head including at least one alignment element for precision alignment of the tape head with a transport direction of a media that is transported across the tape head. More specifically, the present invention relates to a tape head including at least one alignment element that is cofabricated with a write element of the tape head and aligned with a magnetic axis of the tape head so that the write element can be precisely aligned with a transport direction of a media that is transported across the tape head.
BACKGROUND ART
Servo writer heads that write servo code in one or more discrete servo bands along the entire length of a tape in a single pass are well known. The servo code is written on the tape by write elements (magnetic transducers) that are formed on the servo writer head. The write elements have a predetermined pattern such as a chevron pattern, for example. The servo bands are space apart by a pitch and areas between adjacent servo bands are reserved for uses such as data storage, for example. Typically, the servo code in at least two of the discrete servo bands is used to generate servo signals that are used to align data elements on a read/write head to a correct position for reading and writing data to one or more discrete data bands along the length of the tape. Those data bands are positioned in the area between the servo bands. The servo code is prerecorded on the tape during the manufacturing of the tape and the discrete servo bands are positioned at predetermined locations across a width of the tape. Those predetermined locations can be defined by a format specification for the tape. For instance, the format specification will determine the number of servo bands, the number of data bands, and their positions relative to one another across the width of the tape.
As more data is stored in the same amount of physical space on a tape, better reference and position accuracy is necessary. To increase the amount of data that is stored, a feature size of the write and data elements must be reduced to micron and submicron dimensions, resulting in an increase in the number of data bands that can be accommodated across the width of the tape. Servo-writing the tape requires increasingly more precision as the feature size of the write and data elements is decreased. As the servo code is written to the tape, the servo code should be centered on the patten of the write element and must be as perpendicular to a direction of tape travel as possible, for linear tape scans.
Ideally, as the tape is transported across the servo writer head, the patten for the write element should be precisely oriented with the direction of tape travel across the head. Typically, that orientation is perpendicular to the direction of tape travel. In most applications, the servo writer head is mounted in a fixture or jig such as a field replaceable unit (FRU), for example. The FRU positions the servo writer head in fixed orientation with the tape. The FRU can be designed to allow the position of servo writer head, the FRU, or both to be adjusted relative to the tape so that the servo writer head can be aligned with respect to the tape and/or the direction of tape travel.
Prior attempts to align the servo writer head include placing a visual indicator on the servo writer head. Typically, the visual indicator is placed so that it approximates the location of a magnetic axis of the servo writer head. The servo writer head is aligned by adjusting its azimuth relative to the tape until the visual indicator appears to be perpendicular to the direction of tape travel or perpendicular to one or both of the tapes edge's. Methods for forming the visual indicator include marking the servo writer head with a tool to form the visual indicator. For instance, a scribed mark (an incised mark) can be used to form the visual indicator.
Referring to
FIGS. 1
a
and
1
b
, a prior art tape head
200
includes one or more write transducers
241
positioned along a magnetic axis
250
of the tape head
200
. A tape
220
having opposed edges
221
and
223
is in contact with the tape head
200
and is transported across the tape head
200
in a direction of transport D. A visual indicator
215
is formed on the tape head
200
and is operative to define a gross point of reference on the tape head
200
. Typically, the visual indicator
215
defines the approximate location of the magnetic axis
250
. The position of the tape head
200
is adjusted
251
relative to the tape
220
until the visual indicator
215
appears to be approximately perpendicular to the direction of transport D as shown by angle &agr;
1
which represents an angle that is approximately 90 degrees. One disadvantage of the visual indicator
215
is that its location on the tape head
220
is only an approximation of the gross point of reference i.e. the magnetic axis
250
. Because the visual indicator
215
is formed on the tape head
200
after the tape head
200
has been manufactured, it is extremely difficult if not impossible to precisely align the visual indicator
215
with the magnetic axis. Therefore, an axis
217
through the visual indicator
215
will not be colinear with the magnetic axis
250
thereby resulting in the magnetic axis
250
having an orientation angle &agr;
3
that is not perpendicular to the direction of transport D (i.e. &agr;
3
≠90 degrees). It is far more likely that the axis
217
will displaced from the magnetic axis
250
(see
FIG. 1
b
) and be anti-parallel to the magnetic axis
250
. Consequently, the visual indicator
215
is not an accurate indicator that can be used for precision alignment of the write transducers
241
with the direction of transport D. Moreover, if the write transducers
241
have feature sizes that are in the micron or submicron range, then even the slightest alignment error caused by the visual indicator
215
can result in a substantial misalignment of the write transducers
241
with the direction of transport D.
Prior attempts to align the servo writer head have also included using opposing sides of the servo writer head to align the servo writer head with the tape. This approach assumes that the opposing sides of the servo writer head were manufactured such that the opposing sides are parallel with each other and are parallel and/or perpendicular to the magnetic axis of the servo writer head. However, in reality, the servo writer head may be cut using a saw blade or the like. As a result, the opposing sides will not be exactly parallel to each other. For example, instead of having a rectangle shape, the servo writer head will have a parallelogram shape.
Referring to
FIGS. 2
a
and
2
b
, a prior art tape head
300
includes opposing sides
301
and
303
that are not parallel to each other and are not parallel to or perpendicular to a magnetic axis
350
of the tape head
300
(i.e. the tape head
300
has a non-rectangular shape). The tape head
300
includes one or more write transducers
341
positioned along the magnetic axis
350
. A tape
320
having opposed tape edges
321
and
323
is in contact with the tape head
300
and is transported across the tape head
300
in a direction of transport D. A side axis
305
on opposed edge
301
is adjusted
351
until it appears that either one or both of the opposed sides
301
are perpendicular with either one or both of the opposed tape edges (
321
and
323
) as indicated by an angle &agr;
2
in
FIG. 2
b
. However, because the opposed sides
301
are not parallel to each other, the magnetic axis
350
is not perpendicular to the direction of transport D when it appears that angle &agr;
2
is perpendicular to the tape edges (
321
and
323
). It should be noted that this is due in part by the side axis
305
not being parallel to the magnetic axis
350
. Consequently, the magnetic axis
350
makes an angle &agr;
4
that is not perpendicular to the direction of transport D (i.e. &agr;
4
≠90 degrees) when the side axis
305
is at the angle &agr;
2
Beck Patricia A.
Clifford, Jr. George M.
Denny III Trueman H
Hewlett-Packard Development Company
Hudspeth David
Olson Jason
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