U.S. patent application number 09/149769 was filed with the patent office on 2001-08-23 for floating tape head having side wings for longitudinal and azimuth play back with minimized tape wrap angle.
Invention is credited to SALIBA, GEORGE A..
Application Number | 20010015870 09/149769 |
Document ID | / |
Family ID | 22531725 |
Filed Date | 2001-08-23 |
United States Patent
Application |
20010015870 |
Kind Code |
A1 |
SALIBA, GEORGE A. |
August 23, 2001 |
FLOATING TAPE HEAD HAVING SIDE WINGS FOR LONGITUDINAL AND AZIMUTH
PLAY BACK WITH MINIMIZED TAPE WRAP ANGLE
Abstract
A floating head for magnetic tape includes a longitudinal raised
mesa and side wings and has a mesa major dimension less than a
width of the tape without outriggers and employs a minimized tape
wrap angle. The head may be rotated between operating positions for
longitudinal track patterns and azimuthal track patterns. In one
preferred form, the head is employed as a read-only head within a
secondary head positioning mechanism included for backward
compatibility within a high track density tape unit for reading
longitudinal and azimuth track patterns recorded in accordance with
earlier tape track standards.
Inventors: |
SALIBA, GEORGE A.;
(NORTHBORO, MA) |
Correspondence
Address: |
DEBRA A CHUN
QUANTUM CORPORATION
500 MCCARTHY BLVD
MILPITAS
CA
95035
|
Family ID: |
22531725 |
Appl. No.: |
09/149769 |
Filed: |
September 8, 1998 |
Current U.S.
Class: |
360/122 ;
G9B/15.077; G9B/15.082; G9B/5.034; G9B/5.052; G9B/5.203;
G9B/5.204 |
Current CPC
Class: |
G11B 5/10 20130101; G11B
15/62 20130101; G11B 15/602 20130101; G11B 5/1871 20130101; G11B
5/584 20130101; G11B 5/588 20130101 |
Class at
Publication: |
360/122 |
International
Class: |
G11B 005/187 |
Claims
What is claimed is:
1. A head assembly for a tape drive comprising at least one read
head element having a major dimension less than a width dimension
of a magnetic tape for engaging the magnetic tape traveling along a
tape at a tape wrap angle of no more than five degrees.
2. The head assembly set forth in claim 1 wherein the tape wrap
angle is no greater than approximately one degree.
3. The head assembly set forth in claim 1 wherein the head assembly
comprises a body defining a tape-confronting face having a raised
central mesa aligned with the major dimension, the mesa having a
plurality of spaced apart magnetic transducer elements and two side
wings including a left side wing on one side of the central mesa
and a right side wing on another side of the central mesa, the two
side wings having face surfaces recessed relative to the raised
central mesa.
4. The head assembly set forth in claim 3 wherein the side wings
are recessed relative to the raised central mesa by a dimension not
substantially greater than twenty micro-inches.
5. The head assembly set forth in claim 3 wherein the
tape-confronting face is generally ellipsoidal in outline.
6. The head assembly set forth in claim 5 wherein the tape
confronting face is octagonal, with lineal edge segments.
7. The head assembly set forth in claim 6 wherein the lineal edge
segments are chamfered in accordance with a predetermined chamfer
angle.
8. The head assembly set forth in claim 1 wherein the magnetic
transducer elements are magnetic read-only elements.
9. A head assembly for a tape drive comprising a body having a
major axial dimension generally transverse to a direction of travel
of a magnetic tape which is less than a width dimension of tape
traveling along the tape path and engages the tape at a tape wrap
angle of approximately one degree, or less.
10. The head assembly set forth in claim 9 for reading
longitudinally recorded data tracks and further being adapted to be
rotated for reading azimuthally recorded data tracks, wherein a
tape-confronting face of the head assembly comprises a raised
central mesa aligned with the major axial dimension having a
plurality of spaced apart magnetic read elements and two side wings
including a left side wing on one side of the central mesa and a
right side wing on another side of the central mesa, the two side
wings having face surfaces recessed relative to the raised central
mesa.
11. The head assembly set forth in claim 10 wherein the body
comprises a polyhedron and wherein the tape confronting face has a
generally ellipsoidal geometry having the raised central mesa
aligned with a major axis of the polyhedron.
12. The head assembly set forth in claim 11 wherein the generally
ellipsoidal geometry of the tape confronting face of the body
comprises a polygon having at least eight substantially lineal
edges.
13. The head assembly set forth in claim 12 wherein the lineal
edges define a chamfer having a predetermined chamfer radius.
14. The head assembly set forth in claim 10 wherein the tape
comprises a one-half inch width tape, and wherein the major axial
dimension comprises approximately two-fifths of an inch, wherein
the mesa has a width lying in a range between twenty and fifty
thousandths of an inch, and wherein the two side wings have major
surfaces recessed relative to an apex of the central mesa by a
dimension lying in a range between five and 20 microinches.
15. A magnetic head assembly having at least one magnetic data
transducer head and including a body defining a raised central mesa
along a major axial dimension generally transverse to a direction
of tape travel which is less than a width dimension of tape
traveling along the tape path and including the data transducer
head, the mesa for engaging a magnetic recording tape at a
longitudinal tape confrotation angle for reading longitudinally
recorded data tracks and further being adapted to be rotated for
engaging a magnetic recording tape at an azimuth tape confrontation
angle for reading azimuthally recorded data tracks, wherein the
raised central mesa has two side wings including a left side wing
on one side of the central mesa and a right side wing on another
side of the central mesa, the two side wings having face surfaces
recessed relative to the raised central mesa.
16. The magnetic head assembly set forth in claim 15 wherein the
tape comprises a one-half inch width tape, and wherein the major
axial dimension comprises approximately two-fifths of an inch,
wherein the mesa has a width lying in a range between twenty and
fifty thousandths of an inch, and wherein the two side wings have
major surfaces recessed relative to an apex of the central mesa by
a dimension lying in a range between five and 20 microinches.
17. The magnetic head assembly set forth in claim 15 wherein the
raised central mesa is adapted to contact tape passing by at a tape
wrap angle of approximately one degree, or less.
18. The magnetic head assembly set forth in claim 15 further
comprising a shaft attached to the body perpendicular to the raised
central mesa for rotating the body between predetermined angular
positions for reading the longitudinally recorded tracks and for
reading the azimuthally recorded tracks.
Description
REFERENCE TO RELATED APPLICATION
[0001] This is related to a commonly assigned, copending U.S.
patent application Ser. No. ______, filed on the same date, and
entitled: "Backward Compatible Head and Head Positioning Assembly
for a Linear Digital Tape Drive". (Quantum Docket No.
Q99-1048-US1).
FIELD OF THE INVENTION
[0002] The present invention relates to tape drives, and more
particularly the present invention relates to a magnetic tape head
having a major dimension less than a width dimension of the
magnetic tape and having side wings enabling longitudinal and
azimuth orientation at a minimal wrap angle of the tape.
BACKGROUND OF THE INVENTION
[0003] Magnetic tape is widely used for recording digital
information. One extensive use of digital tape recording is to
provide backup and archival storage of vast quantities of digital
information, such as records comprising blocks of data. In some
applications archival records are recorded on tape in a particular
tape format which follows agreed standards at the time the
recording was made. The tape may then be placed into archival
storage and not retrieved until months or years have passed by. It
is not uncommon to specify the useful storage life of recorded
digital tapes and cartridges at thirty years, or longer. Whatever
may be the useful life of a particular magnetic tapes, a primary
assumption on the part of those who store such tapes away is that
the recorded information may be read at some date in the future, if
access to the archived data is required.
[0004] While a particular tape and cartridge may remain functional
over many years after being in archival storage, tape transport
mechanisms typically do not last nearly so long. Standardized tape
recording formats are also susceptible to evolutionary changes and
improvements. These changes are primarily driven by improvements in
magnetic tape and magnetic head technologies which enable much
larger data records and files to be stored on a given area of
magnetic tape. One recent development, first employed in the hard
disk drive industry, and more recently applied to tape recording,
has been the introduction of head assemblies formed of thin film
inductive, and magneto-resistive, and giant magneto-resistive (MR)
read elements. These elements are typically fabricated in processes
including photolithographic patterning steps of the type first
developed for use by the semiconductor industry. One desirable
aspect of these new thin film MR heads is that head gap widths may
be narrowed considerably. Narrower head gaps and finer grain
magnetic media coatings on tape mean that many more lineal data
tracks may be defined across a magnetic recording tape of a
standard given width (such as one-half inch tape). Also, the head
structure may be formed as a single small composite structure on a
common base or substrate and have as many as 12, or more, distinct
heads. By using a common substrate, the heads may be formed to be
in a predetermined precise alignment relative to nominal track
locations defined along the magnetic tape. With e.g. 12 write and
read head elements of the head structure in precise alignment with
the defined nominal track locations, and with large scale
integrated chips providing multiple data write/read channels, it
has now become practical to have e.g. 12 channels for
simultaneously writing user data to tape and for reading user data
back from tape. This increase in the number of write/read channels
effectively increases the overall data transfer rate between a host
computer and the tape drive, and enables the tape drive to be
characterized as having higher performance than previously
available.
[0005] In order to take full advantage of the new thin film MR head
technology in tape drives, a track layout which differs from
previous standard track formats is required. This new track layout
employs tracks of much narrower track width and pitch. Since the
write/read heads are grouped together on a common fabrication
substrate, the data tracks are also grouped together. In one
arrangement, the data tracks are grouped into bands, or zones,
across the tape, such that e.g. ten lateral head positions relative
to the tape within a single zone would access 120 tracks. When a
zone boundary is reached, the head structure or assembly is then
displaced laterally relative to the tape travel path to the next
zone, and the tracks of that zone then become accessible. Because
track widths are very narrow, enabling track densities of e.g. 2000
tracks per inch, or higher, lateral tape motion must be followed in
order to keep the new head assemblies in alignment with the tracks
during tape travel past the head. Magnetic servo patterns written
onto the tape may be read by servo readers and used to generate
position error signals used by a closed loop positioner to correct
head position. Alternatively, optical servo patterns embossed or
otherwise formed on a back side of the tape may be used to provide
position error signals, as disclosed for example in commonly
assigned, copending U.S. patent application Ser. No. 09/046,723
filed on Mar. 24, 1998, and entitled: "Multi-Channel Magnetic Tape
System Having Optical Tracking Servo", the disclosure thereof being
incorporated herein by reference.
[0006] The later high-density track format differs from previous
standard formats. For example, FIG. 1 shows an existing standard
tape format employing longitudinal recording. In this example a
magnetic recording tape 10 has a series of parallel longitudinal
tracks. Three tracks 12A, 12B and 12C are shown in the FIG. 1
example, although more tracks, such as 24, 48, 96 or 128 tracks may
be employed in a one-half inch tape lineal format in accordance
with a particular standardized track layout plan. A head assembly
14 includes e.g. discrete inductive read or write head elements
14A, 14B and 14C which are aligned with the tracks 12A, 12B and
12C. Other tracks may be accessed by displacing the head assembly
14 laterally relative to the direction of the tape along a path
indicated by the vertical arrows axial aligned with the head 14 in
the FIG. 1 view.
[0007] Another preexisting standard tape format employs azimuth
recording of the data tracks, i.e. adjacent tracks are recorded
with magnetic gaps oblique to each other, creating what appears
generally as a "herringbone" pattern, shown in FIG. 2. Therein, one
track 16A has its magnetic flux reversal pattern aligned with a
first azimuth angle oblique to the tape travel direction, and an
adjacent track 16B has its magnetic flux reversal pattern aligned
with a second azimuth angle in an opposite sense of the first angle
relative to a travel path of the magnetic tape 10. One known
advantage derived from azimuth recording is that lineal guard bands
or regions between tracks may be reduced, and the tracks may be
placed closer together and read back without interference from
adjacent tracks. While azimuth recording technology increases track
density somewhat, complications arise in writing and reading the
slanted tracks. Multi-element tape heads, such as the tape head 100
shown in FIGS. 4-6 of U.S. Pat. No. 5,452,152, can be provided with
some of the write/read elements having magnetic gaps aligned with
one azimuth angle, and other write/read elements having magnetic
gaps aligned with the other azimuth angle. Such heads are then
positioned laterally relative to the direction of tape travel in
order to come into alignment with particular tracks. An alternative
approach, also shown in FIG. 2 and enabling compatibility with both
the longitudinal tracks 12A, 12B and 12C of the FIG. 1 example, and
the azimuth tracks 16A and 16B of the FIG. 2 example, calls for
rotating a head 19 having perpendicular (longitudinal) heads 19A
and 19B between the two azimuth track formats and the longitudinal
format position. One example of a multi-element head is given in
commonly assigned, copending U.S. patent application Ser. No.
08/760,794 filed on Dec. 4, 1996, and entitled: "Four Channel
Azimuth and Two Channel Non-Azimuth Read-After-Write Longitudinal
Magnetic Head", the disclosure thereof being incorporated herein by
reference. An example of an azimuth tape recording pattern and an
apparatus for writing the pattern in accordance with servo
information read back from an adjacent track is given in commonly
assigned U.S. Pat. No. 5,371,638, the disclosure thereof being
incorporated by reference.
[0008] FIG. 3 illustrates a newer track format plan employing a
tape 10A carrying high recording density magnetic media. According
to the FIG. 3 track plan, a multiplicity of data tracks 20n are
distributed across e.g. five zones 22A, 22B, 22C, 22D and 22E. A
monolithic thin film head element 24 within the head assembly
includes e.g. 12 write-read elements in relatively close proximity
enabling writing to and reading from tracks of a particular zone,
e.g. zone 22D in the FIG. 3 example. Other zones may be accessed by
displacing the head assembly laterally relative to the direction of
travel of tape 10A. Further details of a tape and tape drive in
accordance with this general approach may be found in the
above-referenced U.S. patent application Ser. No. 09/046,723.
[0009] While the standardized longitudinal recording patterns shown
in the FIG. 1 example, and the azimuth recording patterns shown in
the FIG. 2 example, have worked very well for a number of years,
newer higher density track layout patterns and plans, enabled by
multi-element thin film head as well as improvements in tape media
technologies are now proposed and will most likely become standard
approaches in the future for certain categories of longitudinal
digital tape recording methods and devices. Since extensive
cartridge handling equipment in use is capable of handling standard
cartridges containing tape having the newer format, no compelling
need has arisen to change the cartridge form factor or major
features in order to accommodate the new tape track formats enabled
by emerging new technologies. Yet, a hitherto unsolved need has
remained for backward compatibility within tape drive units having
monolithic multi-element heads by enabling reading back of older
preexisting tape formats recorded on tape carried in standard tape
cartridges, but based on discrete head elements, in order to
recover archival data recorded on the older tapes. In particular, a
hitherto unsolved need has remained for a tape head adapted for
reading back older preexisting longitudinal and azimuth tape
recording formats in a manner employing a minimized tape wrap
angle.
SUMMARY OF THE INVENTION WITH OBJECTS
[0010] A general object of the present invention is to provide a
magnetic tape head having a major dimension less than a width
dimension of a magnetic tape and having side wings enabling
longitudinal and azimuth orientation at a minimal wrap angle of the
tape in a manner overcoming limitations and drawbacks of prior
approaches.
[0011] Another object of the present invention is to provide a
"button-shaped" multi-element magnetic recording head which is
capable of contacting a magnetic tape at a very slight tape wrap
angle, and which may be rotated between positions aligning a
magnetic recording gap of an element of the head with both
longitudinal and azimuthal recording patterns of a lineal data
track recorded on the tape.
[0012] One more object of the present invention is to provide a
tape head having side wings and dimensions less than tape width
such that the tape head floats in close proximity to a tape with
minimized contact, ensuring effective operation with both
longitudinal and azimuthal recording patterns as well as minimal
wear and reliable long useful life.
[0013] Accordingly, a magnetic tape head includes a body having a
major axial dimension generally transverse to a direction of tape
travel which is less than a width dimension of tape traveling along
the tape path and engages the tape at a tape wrap angle of
approximately one degree, or less. The tape head enables at least
reading of longitudinally recorded data tracks and azimuthally
recorded data tracks. A tape-confronting face of the magnetic tape
head includes a raised central mesa aligned with the major axial
dimension and having multiple magnetic read elements. Two side
wings extend from the central mesa including a left side wing and a
right side wing, the two side wings having face surfaces recessed
relative to the raised central mesa. The tape head body preferably
is in the shape of a polyhedron such that the tape confronting face
has a generally ellipsoidal geometry having the raised central mesa
aligned with a major axis of the polyhedron.
[0014] These and other objects, advantages, aspects, and features
of the present invention will be more fully appreciated and
understood upon consideration of the following detailed description
of preferred embodiments presented in conjunction with the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] In the Drawings:
[0016] FIG. 1 is a highly diagrammatic elevational view of a
segment of magnetic data storage tape recorded with a series of
lineal tracks employing longitudinal recording in accordance with a
first preexisting industry standard tape format.
[0017] FIG. 2 is a highly diagrammatic elevational view of a
segment of magnetic data storage tape recorded with a series of
lineal tracks employing azimuth recording in accordance with a
second preexisting industry standard tape format.
[0018] FIG. 3 is a highly diagrammatic elevational view of a
segment of magnetic data storage tape recorded with a multiplicity
of high density lineal tracks in accordance with a new high-density
recording format.
[0019] FIG. 4 is simplified diagrammatic plan view of a tape drive
and data tape cartridge wherein the tape drive includes a
backward-compatible head and head positioning mechanism adapted to
read the first and second preexisting industry standard tape
formats as well as a high-density multi-channel head and head
positioning mechanism adapted to read and write the new
high-density recording format, in accordance with principles of the
present invention.
[0020] FIG. 5 is an enlarged isometric view of the
backward-compatible head and head positioning mechanism shown in
the FIG. 4 tape drive, in accordance with principles of the present
invention.
[0021] FIG. 6 is a top plan view of the FIG. 5 head and positioning
mechanism.
[0022] FIG. 7 is a back side view in elevation of the FIG. 5 head
and positioning mechanism.
[0023] FIG. 8 is a side view in elevation of the FIG. 5 head and
positioning mechanism.
[0024] FIG. 9A is a front view in elevation of the FIG. 5 head and
positioning mechanism in a perpendicular orientation relative to
tape travel for playback of longitudinally recorded data tracks in
accordance with the FIG. 1 format.
[0025] FIG. 9B is a front view in elevation of the FIG. 5 head and
positioning mechanism in a first azimuth orientation relative to
tape travel in e.g a forward direction for playback of one set of
azimuthally recorded data tracks in accordance with the FIG. 2
format.
[0026] FIG. 9C is a front view in elevation of the FIG. 5 head and
positioning mechanism in a second azimuth orientation relative to
tape travel in a reverse direction for playback of a second set of
azimuthally recorded data tracks in accordance with the FIG. 2
format.
[0027] FIG. 9D is a front view in elevation of the FIG. 5 head and
positioning mechanism in a third azimuthal orientation assumed by
the head at a head retract position.
[0028] FIG. 10 is an enlarged diagrammatic plan view of the retract
mechanism of the FIG. 5 head and positioning mechanism.
[0029] FIG. 11 is a diagrammatic view in elevation of the spur-gear
coupling arrangement between the lead screws of the main head
positioning mechanism and the backward-compatible positioning
mechanism of the FIG. 4 tape drive.
[0030] FIG. 12 is a simplified electrical block diagram of the FIG.
4 tape drive.
[0031] FIG. 13 is an enlarged isometric view of the
backward-compatible head of the FIG. 4 tape drive.
[0032] FIG. 14 is an enlarged front view in elevation of the FIG.
13 head.
[0033] FIG. 15 is an enlarged side view in elevation of the FIG. 13
head.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0034] In order to more fully understand and appreciate the present
invention, an example of use of the tape head within a modular
backward compatability secondary head positioning mechanism
included within a tape unit 100 is given. Referring to the
drawings, where like reference numerals designate like or
corresponding parts throughout the views, FIG. 4 presents a tape
unit 100 and single-reel tape cartridge 102. The cartridge 102
includes a supply reel 104 and a pancake 106 of spooled magnetic
recording tape 10A, capable of being written at a high track
density. Tape cartridge 102, while occupying the same physical
envelope or form factor as prior standards cartridges, has at least
one unique structural feature, such as a uniquely located
"beginning of tape" (BOT) hole in accordance e.g. with commonly
assigned U.S. Pat. No. 5,790,237 to Steinberg et al., and entitled:
"Tape Cartridge Qualified by Location, and Identified by Geometry,
of Type Aperture", the disclosure thereof being incorporated herein
by reference. Alternatively, the cartridge 102 may be provided with
a structural feature comprising a uniquely located notch 107, for
identifying the tape 10A as high density recording tape. A
tape-type sensor 109 associated with a cartridge receiver portion
of the tape unit 100 may be provided to sense the notch 107 and
thereby to inform electronics of the unit of the particular tape
type. Other physical features, such as an embossed optical servo
pattern formed on a back side of the tape may also provide a unique
structural feature for indicating a high track density tape. When a
unique BOT hole, or the notch 107, is not sensed at a particular
cartridge, the unit 100 is alerted that the tape format (if any) of
the particular cartridge is in accordance with a prior standards
track format, and calls for use of an auxiliary read-only
capability present within the unit 100. An outer end of the tape
pancake 106 is buckled by a suitable buckling mechanism to a leader
extending from a take-up reel 108 of the tape unit 100. A preferred
form of tape buckling mechanism is described in commonly assigned
U.S. patent application Ser. No. ______, entitled: "Positive
Engagement Buckle for a Tape Drive and Cartridge", filed on the
same date as the present application (Quantum Docket Number
Q99-1022-US1), the disclosure thereof being incorporated herein by
reference. Another form of buckling mechanism is described in
commonly assigned U.S. Pat. No. 5,769,346 to Daly, and entitled:
"Tape Buckling Mechanism for Single Reel Cartridge Tape Recording",
the disclosure thereof being incorporated herein by reference. A
tape supply reel motor 242 and a take-up reel motor 244 are
provided in the tape unit 100 (see FIG. 12) but are not shown in
the FIG. 4 diagrammatic plan view.
[0035] Four tape guide rollers 110, 112, 114 and 116 guide the tape
10A from the supply reel 106 to the take-up reel 108. Two of the
rollers 110 and 112 are formed on a frame 118, and two of the
rollers are mounted to a frame 120. The frames 118 and 120 are
secured to a base 122 of the unit 110. A primary head positioning
mechanism 124 is secured to the base 122 at a location between
guide rollers 112 and 114. The primary positioning mechanism 124
includes a primary multi-channel write/read head assembly 126 for
writing and reading user data onto and from the tape 10A in
accordance with a standardized higher density track layout, e.g. of
the FIG. 3 type. The mechanism 124 also includes a frame 128
supporting a rotating primary lead screw 130. A stepper motor 132,
shown in FIG. 11, rotates the primary lead screw 130. A primary
head block 134 displaces the primary head 126 laterally across the
tape 10A as the primary lead screw 130 is rotated by the stepper
motor 132.
[0036] In this particular tape unit 100, the high density tape 10A
includes longitudinal servo patterns or tracks formed on the back
side thereof e.g. during manufacturing. An optical servo head 134
also mounted to the primary head block 134 adjacently faces a back
side of the tape 10A and optically senses the longitudinal servo
patterns in order to generate position error signals which are fed
into a fine position servo loop (FIG. 12) and result in voice coil
driving currents applied to operate a primary voice coil motor 136,
also a part of the primary head block 134. During data writing and
reading operations, the fine position servo loop keeps the primary
head 126 in alignment with the data track locations in the presence
of disturbances, such as lateral tape motions and vibrations
imparted to the tape 10A along the tape path.
[0037] Also present in the FIG. 4 plan view is a secondary head
positioning mechanism 140. As may be seen in greater structural
detail in FIGS. 5-9, the secondary mechanism 140 includes a frame
142 which may be secured to the base 122 of the tape unit 100.
Preferably, the mechanism 140 is formed as a unitary module which
may be attached to and removed from the base 122 as a single unit.
Suitable electrical plugs and cables enable the mechanism 140 to
make necessary electrical connections with the tape unit 100. The
mechanism 140 selectively positions a secondary read-only head
assembly 144 adjacent to the tape 10A along the tape path at a
location between the guide rollers 114 and 116. The secondary
mechanism 140 also includes a secondary lead screw 146 rotatably
mounted to the frame 142 and a secondary head block 148 having a
follower-nut portion engaging the secondary lead screw 146 such
that as the screw 146 rotates, the head block 148 is translated
elevationally relative to the frame 142. The secondary head block
148 rotatably mounts a lateral head shaft 150 which has one end
thereof secured to the secondary head assembly 144. A guide post
152 extending from the frame 142 is followed by a guide post
follower portion 154 of the secondary block 148 to prevent the
block from rotating relative to the frame 142 as the secondary lead
screw 146 is rotated.
[0038] The lateral head shaft 150 is rotated by e.g. a rotary voice
coil motor 156 comprising a voice coil 158 attached to the shaft
150 and a stator magnet assembly 160 attached to the secondary
block 148. Driving current applied to the voice coil 158 causes the
shaft 150 to rotate between e.g. four positions: retract, azimuth
forward, longitudinal, and azimuth reverse. An optical encoder 162
provides an optical feedback signal marking the angular location of
each shaft position. The encoder 162 comprises a rotating reticle
plate 164 mounted to the head shaft 150 and a photo detector unit
166 mounted to the stator magnet assembly 160. As shown in FIG. 10
a retract mechanism includes a pin 170 extending radially from the
shaft and a pin guide 172 mounted to the secondary block 148
adjacent the secondary head 144. The generally annular pin guide
172 includes an angled and stepped-in region 174. The stepped-in
region 174 is located such that when the shaft 150 is at the
retract angle, the angled portion of the stepped-in region 174
forces the shaft 150 to move axially away from the tape path and
thereby retracts the secondary head 144 from contact proximity with
the tape. The stepped-in region 174 may optionally include a detent
feature for positively maintaining the shaft 150 at the retract
position in the absence of any release rotational force applied by
the voice coil motor 156. A bias spring (not shown) preferably
applies an axial bias force to the shaft 150 to urge it axially
toward the tape confronting position and away from the stepped-in
retract position.
[0039] FIGS. 9A, 9B, 9C and 9D show the four nominal angular
positions capable of being assumed by the secondary head 144. A
normal or perpendicular to tape travel direction position L is
shown in FIG. 9A for use in reading longitudinally written data
tracks as per the FIG. 1 format, for example. An azimuth forward
angle position is shown in FIG. 9B, and an azimuth reverse angle
position is shown in FIG. 9C. These positions are used for reading
azimuth track patterns shown by way of example in FIG. 2. The
forward angle position is assumed in reading azimuth record tracks
while the tape moves in a forward direction from supply reel 104 to
take-up reel 108, while the reverse angle position is assumed in
reading azimuth record tracks while the tape moves in a reverse
direction from take-up reel 108 back onto supply reel 104. A
stepped-in retract position R is shown in FIG. 9D and represents
the angular position of the head 144 while retracted from operative
proximity to the tape 10A, as shown in the FIG. 4 plan view, for
example.
[0040] In accordance with principles of the present invention, the
secondary read-only head assembly 144 most preferably comprises
four read elements 310, 312, 314 and 316 (shown in FIGS. 13 and
14). A preamplifier IC including a preamplifier for each of the
read elements is included on a flex circuit forming a part of the
modular secondary head positioning mechanism 140. Suitable
electrical connectors (not shown) are provided to connect the
circuitry of the secondary head positioning mechanism to circuit
board electronics of the tape unit 100.
[0041] FIG. 11 illustrates one preferred form of mechanical
coupling between the primary lead screw 130 and the secondary lead
screw 146. In this example, a spur gearing arrangement includes a
driver gear 180 attached to the primary lead screw 130. An idler
gear 182 engages the driver gear 180 and transfers rotational force
to a follower gear 184 secured to the secondary lead screw 146. The
idler gear 182 rotates about a shaft 186 mounted to the base 122 of
tape unit 100 at a location e.g. equidistant from axes of rotation
of the primary lead screw 130 and the secondary lead screw 146
thereby transferring rotational force imparted by stepper motor 132
to both lead screws 130 and 146.
[0042] FIG. 12 sets forth a simplified block diagram of the
electronics of the tape unit 100. In pertinent part, the unit 100
includes a user data handling section and a mechanisms section. In
FIG. 12, the user data handling functional blocks are drawn the
left side of a diagrammatic tape path, while the servo mechanisms
functional blocks are drawn on the right side of the tape path. The
user data handling blocks include a user interface 202 which
interfaces the unit 100 to a host computing environment via a
standard bus signaling convention, such as a low voltage
differential SCSI bus 204. The interface block 202 connects to an
internal user and control data bus 206. Also attached to the
internal bus are a programmed data controller 208 and a block
buffer memory 210. The data controller 208 regulates and controls
block formatting and performs error correction coding and decoding
upon blocks written to and read back from the tape 10 (or 10A).
Blocks are assembled and deconstructed in the buffer memory 210
under direct control of the data controller 208. Four-channel data
write/read ICs 212, 214 and 216 support the multi-channel primary
head assembly 126 and one of the ICs 212 selectively supports
read-only elements of the secondary read head assembly 144. A
switch 220 switches read paths of the IC 212 from the primary head
126 to the secondary head 144 whenever a lower density standard
format tape is sensed within the unit 100.
[0043] The unit 100 also includes a programmed servo controller
230. The servo controller 230 has a bus 232 enabling the data
controller 208 to pass commands to the servo controller 230, and
enabling the servo controller to pass status information back to
the data controller 208. In some embodiments where servo
information embedded in magnetic data tracks is present, a
connection may also exist between the servo controller 230 and the
channels 212, 214 and 216 via the data/control bus 206.
[0044] The servo controller 230 supervises a coarse position loop
234 which controls coarse head position established by the stepper
motor 134 of the primary head positioner mechanism 124 in
accordance with track selection values received from the data
controller 208. As already mentioned, the stepper motor 132
simultaneously actuates lead screws 130 and 146 of the primary and
secondary head positioner mechanisms. Since the data controller 208
will learn that a particular cartridge 102 has tape recorded in
accordance with a standard track format via sensor 109, coarse
position will be established either with respect to primary head
126 for a high density track pattern (FIG. 3) or with respect to
secondary head 146 with respect to a particular low density pattern
(FIGS. 1 or 2).
[0045] The servo controller 230 also supervises a tape reel motors
servo loop 240 which controls operation of a supply reel motor 242
and a take-up reel motor 244 in order to establish desired tape
velocity and maintain desired tape tension during tape travel
operations of unit 100.
[0046] The servo controller 230 also supervises a servo fine
position loop 250 which includes an amplifier 252 for controlling
the voice coil motor 136 of the primary head position mechanism in
accordance with servo information provided by optical sensor 134
during high density track format operations with tape 10A. When a
low density tape 10 is sensed by sensor 109, the servo fine
position loop amplifier output is switched from the primary voice
coil motor 136 to the secondary voice coil motor 156 via a switch
254, and the servo fine position loop 250 then employs position
information fed back from the optical sensor 166 of the secondary
head positioning mechanism in order to determine and control the
angle of shaft 150.
[0047] By providing switches 220 and 254, duplication of
electronics circuits needed to support both the primary write/read
head 126 and the secondary read-only head 144 is minimized.
[0048] Referring now to FIGS. 13, 14 and 15, a secondary tape head
assembly 144 in accordance with principles of the present invention
is shown in greater structural detail. The head 144 includes a
generally elliptically shaped body 302 having a tape confronting
front face, a back face secured to shaft 150 and eight sides. The
body 302 is formed of a suitable material such as non-magnetic
ceramic, e.g. calcium titanate. Other materials may also be used to
form the body 302.
[0049] A tape-confronting face of the body 302 includes a raised
longitudinal plateau or mesa 304 and two recessed major side
surfaces or wings, a left wing 306 and a right wing 308. The wings
306 and 308, in combination with the mesa 304 enable the body to
approach the tape at a very slight tape wrap angle (e.g. one degree
or less) and to be rotated between positions to read back
longitudinally recorded information (e.g. the FIG. 1 format) and
azimuthally recorded information (e.g. the FIG. 2 format) without
distorting or warping the tape. In the present example of use
within a backward-compatibility read-only mechanism, four discrete
magnetic read-only elements 310, 312, 314 and 316 are present at
elongated wear regulated regions 318 of the longitudinal mesa 304.
These elements may be formed in accordance with techniques
described in commonly assigned U.S. Pat. No. 5,426,551 entitled:
"Magnetic Contact Head Having a Composite Wear Surface, and
commonly assigned U.S. Pat. No. 5,475,553 entitled: "Tape Head with
Self-Regulating Wear Regions", the disclosures of these patents
being incorporated herein by reference. The magnetic read-only
elements 310, 312, 314 and 316 may further be in accordance with
the teachings of U.S. patent application Ser. No. 09/006,280 filed
on Jan. 13, 1998, and entitled: "Metal Thin-Film Head Core for Tape
Head", and/or U.S. patent application Ser. No. 09/006,281 filed on
Jan. 13, 1998, and entitled: "Self-Aligned Metal Film Core
Multi-Channel Recording Head for Tape Drives", the disclosures of
these applications being incorporated herein by reference.
[0050] As shown in FIG. 14, the read-only elements 310, 312, 314
and 316 are spaced apart such that desired alignment is achieved
with tracks following the longitudinal format (FIG. 1) as well as
tracks following the azimuth format (FIG. 2). A plus or minus 9.1
degree rotation is employed for azimuth read out in accordance with
the FIG. 2 standard track pattern. Most preferably, a distance of
0.056 inch separates the read-only elements 310 and 312 and the
read-only elements 314 and 316. A distance of 0.210 inch separates
element 310 from element 314, and separates element 312 from
element 316. The mesa 304 is approximately 0.02 inch across and
follows a radius of curvature of approximately 0.25 inch.
[0051] The preferred longitudinal dimension (h1) of the head body
302 along the mesa 304 is 0.407 inch which is less than the nominal
width (tw, e.g. 0.5 inch) of the tape 10. The body 302 has a
transverse dimension (tw) of 0.300 inch as measured generally along
the direction of tape travel. The wings 306 and 308 are recessed
below the mesa 304 by a recess dimension (mh) most preferably lying
in a range between five and 20 microinches. A chamfer 320 is formed
along the tape facing edges of the body 302 and follows a radius of
curvature of approximately 0.5 inch.
[0052] When the secondary head 144 is rotated to a tape
confrontation position (FIGS. 9A, 9B or 9C) only a minimal tape
wrap angle is required for operation, most preferably about one
degree of tape wrap, or less. This ever-so-slight wrap angle
suggests that the read-only head 144 floats in close proximity to
the tape with minimized contact, ensuring minimal wear and reliable
long useful life as well as effective operation with both
longitudinal and azimuthal recording patterns. The minimized wrap
angle also enables the head 144 to have a dimension less than the
tape width without need for outriggers or other structure extending
the major dimension of the head to be in excess of the tape width
(tw) and aids realization of a truly compact secondary module
140.
[0053] Although the present invention has been described in terms
of the presently preferred embodiment, i.e., a backward compatible
read-only head assembly for a one-half inch tape linear digital
tape drive system, it should be clear to those skilled in the art
that the present invention may also be utilized in conjunction
with, for example, other tape drives employing different standard
tape sizes and formats. Also, the head assembly may include write
elements in addition to, or in lieu of, read elements. Thus, it
should be understood that the instant disclosure is not to be
interpreted as limiting. Various alterations and modifications will
no doubt become apparent to those skilled in the art after having
read the above disclosure. Accordingly, it is intended that the
appended claims should be interpreted as covering all alterations
and modifications as fall within the true spirit and scope of the
invention.
* * * * *