U.S. patent application number 15/398628 was filed with the patent office on 2018-07-05 for flexible media burnishing apparatus and method.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Robert G. Biskeborn, Gary M. Decad, Jason Liang, Calvin S. Lo.
Application Number | 20180190317 15/398628 |
Document ID | / |
Family ID | 62684325 |
Filed Date | 2018-07-05 |
United States Patent
Application |
20180190317 |
Kind Code |
A1 |
Biskeborn; Robert G. ; et
al. |
July 5, 2018 |
FLEXIBLE MEDIA BURNISHING APPARATUS AND METHOD
Abstract
An apparatus for burnishing media, according to one embodiment,
includes a first block with a media bearing surface having a
plurality of channels and lands. The channels and lands alternate
in a direction of media travel. Each of the lands has at least one
skiving edge along a width thereof. The width of each land extends
orthogonally to the direction of media travel. The apparatus also
includes a mechanism for inducing a wrap angle of the media
relative to media bearing surfaces of at least some of the lands.
Each induced wrap angle is greater than zero degrees. An apparatus
for burnishing media according to another embodiment includes
channels having widths that are less than a width of the media.
Inventors: |
Biskeborn; Robert G.;
(Hollister, CA) ; Decad; Gary M.; (Palo Alto,
CA) ; Liang; Jason; (Campbell, CA) ; Lo;
Calvin S.; (Saratoga, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
62684325 |
Appl. No.: |
15/398628 |
Filed: |
January 4, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G11B 15/60 20130101;
B24B 1/00 20130101; G11B 5/84 20130101; G11B 5/78 20130101 |
International
Class: |
G11B 5/78 20060101
G11B005/78 |
Claims
1. (canceled)
2. An apparatus for burnishing media, the apparatus comprising: a
first block with a media bearing surface having a plurality of
channels and lands, wherein the channels and lands alternate in a
direction of media travel, wherein each of the lands has at least
one skiving edge along a width thereof, the width of each land
extending orthogonally to the direction of media travel; and a
mechanism for inducing a wrap angle of the media relative to media
bearing surfaces of at least three of the lands, wherein each
induced wrap angle is greater than zero degrees, wherein at least
some of the channels of the first block have an opening that
connects to a vacuum source to urge the media toward media bearing
surfaces of the lands of the first block.
3. An apparatus for burnishing media, the apparatus comprising: a
first block with a media bearing surface having a plurality of
channels and lands, wherein the channels and lands alternate in a
direction of media travel, wherein each of the lands has at least
one skiving edge along a width thereof, the width of each land
extending orthogonally to the direction of media travel; and a
mechanism for inducing a wrap angle of the media relative to media
bearing surfaces of at least some of the lands, wherein each
induced wrap angle is greater than zero degrees, wherein the
mechanism for inducing the wrap angles includes a second block
positioned above the first block, the second block having lands
positioned relative to the first block to push the media into the
channels of the first block.
4. An apparatus as recited in claim 3, wherein the lands of the
second block are contoured.
5. An apparatus as recited in claim 3, wherein the lands of the
second block are aligned to the channels of the first block.
6. An apparatus as recited in claim 3, wherein the lands of the
second block have openings to allow pressurized air to flow against
the media to push the media toward the channels of the first
block.
7. An apparatus as recited in claim 6, wherein the openings are
configured to direct pressurized air from the openings to provide
an air film between the lands of the second block and the media for
reducing friction between the media and the second block.
8. An apparatus as recited in claim 2, wherein each induced wrap
angle is in a range of about 0.1 to about 3 degrees.
9. An apparatus as recited in claim 2, wherein a media bearing
surface of each of the lands is planar.
10. An apparatus as recited in claim 2, comprising a mechanism for
removing accumulated debris from the channels.
11. A method for using the apparatus as recited in claim 2,
comprising running the media over the first block in the direction
of media travel.
12. An apparatus as recited in claim 2, further comprising: a drive
mechanism for passing a magnetic medium over the first block; and a
controller electrically coupled to the drive mechanism.
13. An apparatus for burnishing media, the apparatus comprising: a
first block with a media bearing surface having a plurality of
channels and lands, wherein the channels and lands alternate in a
direction of media travel, wherein each of the lands has at least
one skiving edge along a width thereof, the width of each land
extending orthogonally to the direction of media travel, wherein a
width of at least some of the channels is less than a width of the
media, wherein the channels are configured to create a subambient
air pressure therein upon movement of the media relative thereto
for inducing wrap angles of the media relative to media bearing
surfaces of the lands.
14. An apparatus as recited in claim 13, wherein the induced wrap
angles being greater than zero degrees.
15. An apparatus as recited in claim 14, wherein the induced wrap
angles are in a range of about 0.1 to about 3 degrees.
16. An apparatus as recited in claim 13, wherein media bearing
surfaces of each of the lands is planar.
17. An apparatus as recited in claim 13, comprising a mechanism for
removing accumulated debris from the channels.
18. An apparatus as recited in claim 13, wherein the channels of
the first block have openings that connect to a vacuum source to
urge the media toward media bearing surfaces of the lands of the
first block.
19. A method for using the apparatus as recited in claim 13,
comprising running the media over the first block in the direction
of media travel.
20. An apparatus as recited in claim 13, further comprising: a
drive mechanism for passing a magnetic medium over the first block;
and a controller electrically coupled to the drive mechanism.
Description
BACKGROUND
[0001] The present invention relates to data storage systems, and
more particularly, this invention relates to an apparatus that may
be particularly useful for burnishing magnetic flexible media.
[0002] In magnetic storage systems, magnetic transducers read data
from and write data onto magnetic recording media. Data is written
on the magnetic recording media by moving a magnetic recording
transducer to a position over the media where the data is to be
stored. The magnetic recording transducer then generates a magnetic
field, which encodes the data into the magnetic media. Data is read
from the media by similarly positioning the magnetic read
transducer and then sensing the magnetic field of the magnetic
media. Read and write operations may be independently synchronized
with the movement of the media to ensure that the data can be read
from and written to the desired location on the media.
[0003] An important and continuing goal in the data storage
industry is that of increasing the density of data stored on a
medium. For tape storage systems, that goal has led to increasing
the track and linear bit density on recording tape, and decreasing
the thickness of the magnetic tape medium. However, the development
of small footprint, higher performance tape drive systems has
created various problems in the design of a tape head assembly for
use in such systems.
[0004] In a tape drive system, the drive moves the magnetic tape
over the surface of the tape head at high speed. Usually the tape
head is designed to minimize the spacing between the head and the
tape. The spacing between the magnetic head and the magnetic tape
is crucial and so goals in these systems are to have the recording
gaps of the transducers, which are the source of the magnetic
recording flux in near contact with the tape to effect writing
sharp transitions, and to have the read elements in near contact
with the tape to provide effective coupling of the magnetic field
from the tape to the read elements.
SUMMARY
[0005] An apparatus for burnishing media, according to one
embodiment, includes a first block with a media bearing surface
having a plurality of channels and lands. The channels and lands
alternate in a direction of media travel. Each of the lands has at
least one skiving edge along a width thereof. The width of each
land extends orthogonally to the direction of media travel. The
apparatus also includes a mechanism for inducing a wrap angle of
the media relative to media bearing surfaces of at least some of
the lands. Each induced wrap angle is greater than zero
degrees.
[0006] An apparatus for burnishing media according to another
embodiment includes a first block with a media bearing surface
having a plurality of channels and lands. The channels and lands
alternate in a direction of media travel. Each of the lands has at
least one skiving edge along a width thereof, the width of each
land extending orthogonally to the direction of media travel. A
width of at least some of the channels is less than a width of the
media.
[0007] Any of these embodiments may be implemented in a system such
as a tape drive system, which may include a magnetic head, a drive
mechanism for passing a magnetic medium (e.g., recording tape) over
the magnetic head, and a controller electrically coupled to the
magnetic head.
[0008] Other aspects and embodiments of the present invention will
become apparent from the following detailed description, which,
when taken in conjunction with the drawings, illustrate by way of
example the principles of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1A is a schematic diagram of a simplified tape drive
system according to one embodiment.
[0010] FIG. 1B is a schematic diagram of a tape cartridge according
to one embodiment.
[0011] FIG. 2 illustrates a side view of a flat-lapped,
bi-directional, two-module magnetic tape head according to one
embodiment.
[0012] FIG. 2A is a tape bearing surface view taken from Line 2A of
FIG. 2.
[0013] FIG. 2B is a detailed view taken from Circle 2B of FIG.
2A.
[0014] FIG. 2C is a detailed view of a partial tape bearing surface
of a pair of modules.
[0015] FIG. 3 is a partial tape bearing surface view of a magnetic
head having a write-read-write configuration.
[0016] FIG. 4 is a partial tape bearing surface view of a magnetic
head having a read-write-read configuration.
[0017] FIG. 5 is a side view of a magnetic tape head with three
modules according to one embodiment where the modules all generally
lie along about parallel planes.
[0018] FIG. 6 is a side view of a magnetic tape head with three
modules in a tangent (angled) configuration.
[0019] FIG. 7 is a side view of a magnetic tape head with three
modules in an overwrap configuration.
[0020] FIG. 8A is a top down view of a block for burnishing tape
media according to one embodiment.
[0021] FIG. 8B is a cross sectional side view taken along Line
8B-8B of FIG. 8A.
[0022] FIG. 8C is a perspective view of the block of FIG. 8A.
[0023] FIG. 8D is a top down view of a block for burnishing tape
media according to one embodiment.
[0024] FIG. 9 is a cross-sectional side view of a block for
burnishing tape media according to one embodiment.
[0025] FIG. 10 is a side view of a set of blocks for burnishing
tape media according to one embodiment.
[0026] FIG. 11 is a side view of a set of blocks for burnishing
tape media according to one embodiment.
DETAILED DESCRIPTION
[0027] The following description is made for the purpose of
illustrating the general principles of the present invention and is
not meant to limit the inventive concepts claimed herein. Further,
particular features described herein can be used in combination
with other described features in each of the various possible
combinations and permutations.
[0028] Unless otherwise specifically defined herein, all terms are
to be given their broadest possible interpretation including
meanings implied from the specification as well as meanings
understood by those skilled in the art and/or as defined in
dictionaries, treatises, etc.
[0029] It must also be noted that, as used in the specification and
the appended claims, the singular forms "a," "an" and "the" include
plural referents unless otherwise specified.
[0030] The following description discloses several preferred
embodiments of magnetic storage systems, as well as operation
and/or component parts thereof.
[0031] In one general embodiment, an apparatus for burnishing media
includes a first block with a media bearing surface having a
plurality of channels and lands. The channels and lands alternate
in a direction of media travel. Each of the lands has at least one
skiving edge along a width thereof. The width of each land extends
orthogonally to the direction of media travel. The apparatus also
includes a mechanism for inducing a wrap angle of the media
relative to media bearing surfaces of at least some of the lands.
Each induced wrap angle is greater than zero degrees.
[0032] In another general embodiment, an apparatus for burnishing
media includes a first block with a media bearing surface having a
plurality of channels and lands. The channels and lands alternate
in a direction of media travel. Each of the lands has at least one
skiving edge along a width thereof, the width of each land
extending orthogonally to the direction of media travel. A width of
at least some of the channels is less than a width of the
media.
[0033] FIG. 1A illustrates a simplified tape drive 100 of a
tape-based data storage system, which may be employed in the
context of the present invention. While one specific implementation
of a tape drive is shown in FIG. 1A, it should be noted that the
embodiments described herein may be implemented in the context of
any type of tape drive system.
[0034] As shown, a tape supply cartridge 120 and a take-up reel 121
are provided to support a tape 122. One or more of the reels may
form part of a removable cartridge and are not necessarily part of
the system 100. The tape drive, such as that illustrated in FIG.
1A, may further include drive motor(s) to drive the tape supply
cartridge 120 and the take-up reel 121 to move the tape 122 over a
tape head 126 of any type. Such head may include an array of
readers, writers, or both.
[0035] Guides 125 guide the tape 122 across the tape head 126. Such
tape head 126 is in turn coupled to a controller 128 via a cable
130. The controller 128, may be or include a processor and/or any
logic for controlling any subsystem of the drive 100. For example,
the controller 128 typically controls head functions such as servo
following, data writing, data reading, etc. The controller 128 may
include at least one servo channel and at least one data channel,
each of which include data flow processing logic configured to
process and/or store information to be written to and/or read from
the tape 122. The controller 128 may operate under logic known in
the art, as well as any logic disclosed herein, and thus may be
considered as a processor for any of the descriptions of tape
drives included herein, in various embodiments. The controller 128
may be coupled to a memory 136 of any known type, which may store
instructions executable by the controller 128. Moreover, the
controller 128 may be configured and/or programmable to perform or
control some or all of the methodology presented herein. Thus, the
controller 128 may be considered to be configured to perform
various operations by way of logic programmed into one or more
chips, modules, and/or blocks; software, firmware, and/or other
instructions being available to one or more processors; etc., and
combinations thereof.
[0036] The cable 130 may include read/write circuits to transmit
data to the head 126 to be recorded on the tape 122 and to receive
data read by the head 126 from the tape 122. An actuator 132
controls position of the head 126 relative to the tape 122.
[0037] An interface 134 may also be provided for communication
between the tape drive 100 and a host (internal or external) to
send and receive the data and for controlling the operation of the
tape drive 100 and communicating the status of the tape drive 100
to the host, all as will be understood by those of skill in the
art.
[0038] FIG. 1B illustrates an exemplary tape cartridge 150
according to one embodiment. Such tape cartridge 150 may be used
with a system such as that shown in FIG. 1A. As shown, the tape
cartridge 150 includes a housing 152, a tape 122 in the housing
152, and a nonvolatile memory 156 coupled to the housing 152. In
some approaches, the nonvolatile memory 156 may be embedded inside
the housing 152, as shown in FIG. 1B. In more approaches, the
nonvolatile memory 156 may be attached to the inside or outside of
the housing 152 without modification of the housing 152. For
example, the nonvolatile memory may be embedded in a self-adhesive
label 154. In one preferred embodiment, the nonvolatile memory 156
may be a Flash memory device, ROM device, etc., embedded into or
coupled to the inside or outside of the tape cartridge 150. The
nonvolatile memory is accessible by the tape drive and the tape
operating software (the driver software), and/or another
device.
[0039] By way of example, FIG. 2 illustrates a side view of a
flat-lapped, bi-directional, two-module magnetic tape head 200
which may be implemented in the context of the present invention.
As shown, the head includes a pair of bases 202, each equipped with
a module 204, and fixed at a small angle .alpha. with respect to
each other. The bases may be "U-beams" that are adhesively coupled
together. Each module 204 includes a substrate 204A and a closure
204B with a thin film portion, commonly referred to as a "gap" in
which the readers and/or writers 206 are formed. In use, a tape 208
is moved over the modules 204 along a media (tape) bearing surface
209 in the manner shown for reading and writing data on the tape
208 using the readers and writers. The wrap angle .theta. of the
tape 208 at edges going onto and exiting the flat media support
surfaces 209 are usually between about 0.1 degree and about 3
degrees.
[0040] The substrates 204A are typically constructed of a wear
resistant material, such as a ceramic. The closures 204B may be
made of the same or similar ceramic as the substrates 204A.
[0041] The readers and writers may be arranged in a piggyback or
merged configuration. An illustrative piggybacked configuration
comprises a (magnetically inductive) writer transducer on top of
(or below) a (magnetically shielded) reader transducer (e.g., a
magnetoresistive reader, etc.), wherein the poles of the writer and
the shields of the reader are generally separated. An illustrative
merged configuration comprises one reader shield in the same
physical layer as one writer pole (hence, "merged"). The readers
and writers may also be arranged in an interleaved configuration.
Alternatively, each array of channels may be readers or writers
only. Any of these arrays may contain one or more servo track
readers for reading servo data on the medium.
[0042] FIG. 2A illustrates the tape bearing surface 209 of one of
the modules 204 taken from Line 2A of FIG. 2. A representative tape
208 is shown in dashed lines. The module 204 is preferably long
enough to be able to support the tape as the head steps between
data bands.
[0043] In this example, the tape 208 includes 4 to 32 data bands,
e.g., with 16 data bands and 17 servo tracks 210, as shown in FIG.
2A on a one-half inch wide tape 208. The data bands are defined
between servo tracks 210. Each data band may include a number of
data tracks, for example 1024 data tracks (not shown). During
read/write operations, the readers and/or writers 206 are
positioned to specific track positions within one of the data
bands. Outer readers, sometimes called servo readers, read the
servo tracks 210. The servo signals are in turn used to keep the
readers and/or writers 206 aligned with a particular set of tracks
during the read/write operations.
[0044] FIG. 2B depicts a plurality of readers and/or writers 206
formed in a gap 218 on the module 204 in Circle 2B of FIG. 2A. As
shown, the array of readers and writers 206 includes, for example,
16 writers 214, 16 readers 216 and two servo readers 212, though
the number of elements may vary. Illustrative embodiments include
8, 16, 32, 40, and 64 active readers and/or writers 206 per array,
and alternatively interleaved designs having odd numbers of reader
or writers such as 17, 25, 33, etc. An illustrative embodiment
includes 32 readers per array and/or 32 writers per array, where
the actual number of transducer elements could be greater, e.g.,
33, 34, etc. This allows the tape to travel more slowly, thereby
reducing speed-induced tracking and mechanical difficulties and/or
execute fewer "wraps" to fill or read the tape. While the readers
and writers may be arranged in a piggyback configuration as shown
in FIG. 2B, the readers 216 and writers 214 may also be arranged in
an interleaved configuration. Alternatively, each array of readers
and/or writers 206 may be readers or writers only, and the arrays
may contain one or more servo readers 212. As noted by considering
FIGS. 2 and 2A-B together, each module 204 may include a
complementary set of readers and/or writers 206 for such things as
bi-directional reading and writing, read-while-write capability,
backward compatibility, etc.
[0045] FIG. 2C shows a partial tape bearing surface view of
complementary modules of a magnetic tape head 200 according to one
embodiment. In this embodiment, each module has a plurality of
read/write (R/W) pairs in a piggyback configuration formed on a
common substrate 204A and an optional electrically insulative layer
236. The writers, exemplified by the write transducer 214 and the
readers, exemplified by the read transducer 216, are aligned
parallel to an intended direction of travel of a tape medium
thereacross to form an R/W pair, exemplified by the R/W pair 222.
Note that the intended direction of tape travel is sometimes
referred to herein as the direction of tape travel, and such terms
may be used interchangeably. Such direction of tape travel may be
inferred from the design of the system, e.g., by examining the
guides; observing the actual direction of tape travel relative to
the reference point; etc. Moreover, in a system operable for
bi-direction reading and/or writing, the direction of tape travel
in both directions is typically parallel and thus both directions
may be considered equivalent to each other.
[0046] Several R/W pairs 222 may be present, such as 8, 16, 32
pairs, etc. The R/W pairs 222 as shown are linearly aligned in a
direction generally perpendicular to a direction of tape travel
thereacross. However, the pairs may also be aligned diagonally,
etc. Servo readers 212 are positioned on the outside of the array
of R/W pairs, the function of which is well known.
[0047] Generally, the magnetic tape medium moves in either a
forward or reverse direction as indicated by arrow 220. The
magnetic tape medium and head assembly 200 operate in a transducing
relationship in the manner well-known in the art. The piggybacked
MR head assembly 200 includes two thin-film modules 224 and 226 of
generally identical construction.
[0048] Modules 224 and 226 are joined together with a space present
between closures 204B thereof (partially shown) to form a single
physical unit to provide read-while-write capability by activating
the writer of the leading module and reader of the trailing module
aligned with the writer of the leading module parallel to the
direction of tape travel relative thereto. When a module 224, 226
of a piggyback head 200 is constructed, layers are formed in the
gap 218 created above an electrically conductive substrate 204A
(partially shown), e.g., of AlTiC, in generally the following order
for the R/W pairs 222: an insulating layer 236, a first shield 232
typically of an iron alloy such as NiFe(--), cobalt zirconium
tantalum (CZT) or Al--Fe--Si (Sendust), a sensor 234 for sensing a
data track on a magnetic medium, a second shield 238 typically of a
nickel-iron alloy (e.g., .about.80/20 at % NiFe, also known as
permalloy), first and second writer pole tips 228, 230, and a coil
(not shown). The sensor may be of any known type, including those
based on MR, GMR, AMR, tunneling magnetoresistance (TMR), etc.
[0049] The first and second writer poles 228, 230 may be fabricated
from high magnetic moment materials such as .about.45/55 NiFe. Note
that these materials are provided by way of example only, and other
materials may be used. Additional layers such as insulation between
the shields and/or pole tips and an insulation layer surrounding
the sensor may be present. Illustrative materials for the
insulation include alumina and other oxides, insulative polymers,
etc.
[0050] The configuration of the tape head 126 according to one
embodiment includes multiple modules, preferably three or more. In
a write-read-write (W-R-W) head, outer modules for writing flank
one or more inner modules for reading. Referring to FIG. 3,
depicting a W-R-W configuration, the outer modules 252, 256 each
include one or more arrays of writers 260. The inner module 254 of
FIG. 3 includes one or more arrays of readers 258 in a similar
configuration. Variations of a multi-module head include a R-W-R
head (FIG. 4), a R-R-W head, a W-W-R head, etc. In yet other
variations, one or more of the modules may have read/write pairs of
transducers. Moreover, more than three modules may be present. In
further approaches, two outer modules may flank two or more inner
modules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. For
simplicity, a W-R-W head is used primarily herein to exemplify
embodiments of the present invention. One skilled in the art
apprised with the teachings herein will appreciate how permutations
of the present invention would apply to configurations other than a
W-R-W configuration.
[0051] FIG. 5 illustrates a magnetic head 126 according to one
embodiment of the present invention that includes first, second and
third modules 302, 304, 306 each having a tape bearing surface 308,
310, 312 respectively, which may be flat, contoured, etc. Note that
while the term "tape bearing surface" appears to imply that the
surface facing the tape 315 is in physical contact with the tape
bearing surface, this is not necessarily the case. Rather, only a
portion of the tape may be in contact with the tape bearing
surface, constantly or intermittently, with other portions of the
tape riding (or "flying") above the tape bearing surface on a layer
of air, sometimes referred to as an "air bearing". The first module
302 will be referred to as the "leading" module as it is the first
module encountered by the tape in a three module design for tape
moving in the indicated direction. The third module 306 will be
referred to as the "trailing" module. The trailing module follows
the middle module and is the last module seen by the tape in a
three module design. The leading and trailing modules 302, 306 are
referred to collectively as outer modules. Also note that the outer
modules 302, 306 will alternate as leading modules, depending on
the direction of travel of the tape 315.
[0052] In one embodiment, the tape bearing surfaces 308, 310, 312
of the first, second and third modules 302, 304, 306 lie on about
parallel planes (which is meant to include parallel and nearly
parallel planes, e.g., between parallel and tangential as in FIG.
6), and the tape bearing surface 310 of the second module 304 is
above the tape bearing surfaces 308, 312 of the first and third
modules 302, 306. As described below, this has the effect of
creating the desired wrap angle .alpha..sub.2 of the tape relative
to the tape bearing surface 310 of the second module 304.
[0053] Where the tape bearing surfaces 308, 310, 312 lie along
parallel or nearly parallel yet offset planes, intuitively, the
tape should peel off of the tape bearing surface 308 of the leading
module 302. However, the vacuum created by the skiving edge 318 of
the leading module 302 has been found by experimentation to be
sufficient to keep the tape adhered to the tape bearing surface 308
of the leading module 302. The trailing edge 320 of the leading
module 302 (the end from which the tape leaves the leading module
302) is the approximate reference point which defines the wrap
angle .alpha..sub.2 over the tape bearing surface 310 of the second
module 304. The tape stays in close proximity to the tape bearing
surface until close to the trailing edge 320 of the leading module
302. Accordingly, read and/or write elements 322 may be located
near the trailing edges of the outer modules 302, 306. These
embodiments are particularly adapted for write-read-write
applications.
[0054] A benefit of this and other embodiments described herein is
that, because the outer modules 302, 306 are fixed at a determined
offset from the second module 304, the inner wrap angle
.alpha..sub.2 is fixed when the modules 302, 304, 306 are coupled
together or are otherwise fixed into a head. The inner wrap angle
.alpha..sub.2 is approximately tan.sup.-1(.delta./W) where .delta.
is the height difference between the planes of the tape bearing
surfaces 308, 310 and W is the width between the opposing ends of
the tape bearing surfaces 308, 310. An illustrative inner wrap
angle .alpha..sub.2 is in a range of about 0.3.degree. to about
1.1.degree., though can be any angle required by the design.
[0055] Beneficially, the inner wrap angle .alpha..sub.2 on the side
of the module 304 receiving the tape (leading edge) will be larger
than the inner wrap angle .alpha..sub.3 on the trailing edge, as
the tape 315 rides above the trailing module 306. This difference
is generally beneficial as a smaller .alpha..sub.3 tends to oppose
what has heretofore been a steeper exiting effective wrap
angle.
[0056] Note that the tape bearing surfaces 308, 312 of the outer
modules 302, 306 are positioned to achieve a negative wrap angle at
the trailing edge 320 of the leading module 302. This is generally
beneficial in helping to reduce friction due to contact with the
trailing edge 320, provided that proper consideration is given to
the location of the crowbar region that forms in the tape where it
peels off the head. This negative wrap angle also reduces flutter
and scrubbing damage to the elements on the leading module 302.
Further, at the trailing module 306, the tape 315 flies over the
tape bearing surface 312 so there is virtually no wear on the
elements when tape is moving in this direction. Particularly, the
tape 315 entrains air and so will not significantly ride on the
tape bearing surface 312 of the third module 306 (some contact may
occur). This is permissible, because the leading module 302 is
writing while the trailing module 306 is idle.
[0057] Writing and reading functions are performed by different
modules at any given time. In one embodiment, the second module 304
includes a plurality of data and optional servo readers 331 and no
writers. The first and third modules 302, 306 include a plurality
of writers 322 and no data readers, with the exception that the
outer modules 302, 306 may include optional servo readers. The
servo readers may be used to position the head during reading
and/or writing operations. The servo reader(s) on each module are
typically located towards the end of the array of readers or
writers.
[0058] By having only readers or side by side writers and servo
readers in the gap between the substrate and closure, the gap
length can be substantially reduced. Typical heads have piggybacked
readers and writers, where the writer is formed above each reader.
A typical gap is 20-35 microns. However, irregularities on the tape
may tend to droop into the gap and create gap erosion. Thus, the
smaller the gap is the better. The smaller gap enabled herein
exhibits fewer wear related problems.
[0059] In some embodiments, the second module 304 has a closure,
while the first and third modules 302, 306 do not have a closure.
Where there is no closure, preferably a hard coating is added to
the module. One preferred coating is diamond-like carbon (DLC).
[0060] In the embodiment shown in FIG. 5, the first, second, and
third modules 302, 304, 306 each have a closure 332, 334, 336,
which extends the tape bearing surface of the associated module,
thereby effectively positioning the read/write elements away from
the edge of the tape bearing surface. The closure 332 on the second
module 304 can be a ceramic closure of a type typically found on
tape heads. The closures 334, 336 of the first and third modules
302, 306, however, may be shorter than the closure 332 of the
second module 304 as measured parallel to a direction of tape
travel over the respective module. This enables positioning the
modules closer together. One way to produce shorter closures 334,
336 is to lap the standard ceramic closures of the second module
304 an additional amount. Another way is to plate or deposit thin
film closures above the elements during thin film processing. For
example, a thin film closure of a hard material such as Sendust or
nickel-iron alloy (e.g., 45/55) can be formed on the module.
[0061] With reduced-thickness ceramic or thin film closures 334,
336 or no closures on the outer modules 302, 306, the write-to-read
gap spacing can be reduced to less than about 1 mm, e.g., about
0.75 mm, or 50% less than commonly-used LTO tape head spacing. The
open space between the modules 302, 304, 306 can still be set to
approximately 0.5 to 0.6 mm, which in some embodiments is ideal for
stabilizing tape motion over the second module 304.
[0062] Depending on tape tension and stiffness, it may be desirable
to angle the tape bearing surfaces of the outer modules relative to
the tape bearing surface of the second module. FIG. 6 illustrates
an embodiment where the modules 302, 304, 306 are in a tangent or
nearly tangent (angled) configuration. Particularly, the tape
bearing surfaces of the outer modules 302, 306 are about parallel
to the tape at the desired wrap angle .alpha..sub.2 of the second
module 304. In other words, the planes of the tape bearing surfaces
308, 312 of the outer modules 302, 306 are oriented at about the
desired wrap angle .alpha..sub.2 of the tape 315 relative to the
second module 304. The tape will also pop off of the trailing
module 306 in this embodiment, thereby reducing wear on the
elements in the trailing module 306. These embodiments are
particularly useful for write-read-write applications. Additional
aspects of these embodiments are similar to those given above.
[0063] Typically, the tape wrap angles may be set about midway
between the embodiments shown in FIGS. 5 and 6.
[0064] FIG. 7 illustrates an embodiment where the modules 302, 304,
306 are in an overwrap configuration. Particularly, the tape
bearing surfaces 308, 312 of the outer modules 302, 306 are angled
slightly more than the tape 315 when set at the desired wrap angle
.alpha..sub.2 relative to the second module 304. In this
embodiment, the tape does not pop off of the trailing module,
allowing it to be used for writing or reading. Accordingly, the
leading and middle modules can both perform reading and/or writing
functions while the trailing module can read any just-written data.
Thus, these embodiments are preferred for write-read-write,
read-write-read, and write-write-read applications. In the latter
embodiments, closures should be wider than the tape canopies for
ensuring read capability. The wider closures may require a wider
gap-to-gap separation. Therefore, a preferred embodiment has a
write-read-write configuration, which may use shortened closures
that thus allow closer gap-to-gap separation.
[0065] Additional aspects of the embodiments shown in FIGS. 6 and 7
are similar to those given above.
[0066] A 32 channel version of a multi-module head 126 may use
cables 350 having leads on the same or smaller pitch as current 16
channel piggyback LTO modules, or alternatively the connections on
the module may be organ-keyboarded for a 50% reduction in cable
span. Over-under, writing pair unshielded cables may be used for
the writers, which may have integrated servo readers.
[0067] The outer wrap angles .alpha..sub.1 may be set in the drive,
such as by guides of any type known in the art, such as adjustable
rollers, slides, etc. or alternatively by outriggers, which are
integral to the head. For example, rollers having an offset axis
may be used to set the wrap angles. The offset axis creates an
orbital arc of rotation, allowing precise alignment of the wrap
angle .alpha..sub.1.
[0068] To assemble any of the embodiments described above,
conventional u-beam assembly can be used. Accordingly, the mass of
the resultant head may be maintained or even reduced relative to
heads of previous generations. In other approaches, the modules may
be constructed as a unitary body. Those skilled in the art, armed
with the present teachings, will appreciate that other known
methods of manufacturing such heads may be adapted for use in
constructing such heads. Moreover, unless otherwise specified,
processes and materials of types known in the art may be adapted
for use in various embodiments in conformance with the teachings
herein, as would become apparent to one skilled in the art upon
reading the present disclosure.
[0069] Servo pattern and data read sensors may experience shorting
failures during normal data writing and/or reading operations.
Particularly, such shorting may be caused by protruding defects
(herein "surface defects") in the magnetic tape recording media
(also generically referred to as "tape"), such as agglomerations of
abrasive particles or other defects, e.g., hard particulates, that
protrude from the tape surface. Such surface defects may smear
and/or plow conductive material from the thin films of the reader
across the sensor, thereby creating an electrical short.
[0070] While this issue is relevant to
current-perpendicular-to-plane (CPP) readers in general, this
problem is particularly problematic with CPP TMR sensors. Because
the deposition thickness of the tunnel barrier the TMR sensor is
very thin, e.g., less than about 12 angstroms in some approaches.
TMR sensors may be particularly susceptible to such shorting.
[0071] Interactions between tape media surface defects and a sensor
surface may also lead to friction-related functionality issues. For
example, when a surface defect passes over a sensor, friction may
lead to plastic deformation of one or more delicate thin films of
the sensor. Plastic deformation of the delicate thin films may
alter the stress distribution inside the sensor, which in turn may
be presented as noise due to magnetic instability, e.g., switching
magnetic domains.
[0072] Narrower write heads may also be subject to degradation via
spacing loss resulting from gouges caused by tape surface defects.
Such problematic tape surface defects may protrude from the surface
of the tape, and may include one or more agglomerations of abrasive
particles. The surface defects may also include dense
agglomerations of binder materials, wear particles, isolated
particle defects, etc.
[0073] Such surface defects may result from, e.g., the milling of
particles used in the tape, e.g., where a larger particle is
inadvertently added to the tape media during manufacture.
[0074] Despite filtering systems and quality control used by tape
media manufacturers, including tape burnishing via lapping tape,
some tapes still contain defects that are capable of damaging
magnetic tape heads. As the defective media runs over the TMR
structure of the sensor, a conductive smear may develop leading to
a short of the head. As a result, the sensor shows a resistance
reduction with a loss of output. Thus, it would be desirable to
pre-condition the media by blunting and smoothing the defects
before running the media over the tape head.
[0075] Conventional methods of cleaning or running the newly
manufactured magnetic recording media over a blade are not
sufficient to pre-condition and remove particulate defects from the
media for running over a TMR sensor, because particulate defects
are often persistent and resistant to burnishing during operating a
drive. For example, a particulate defect that remains after the
manufacturing process and damages a track on a head may also have
the ability to damage the same track on a head in another drive. It
would be desirable for the burnishing method of pre-conditioning
defective tapes to involve an apparatus that is harder than the
particulates in the media in order to prevent the particulate
debris from damaging the TMR sensor.
[0076] Various embodiments described herein involve an apparatus
having a hard material that wraps the tape under tension on sharp
edges at different angles in a repetitive manner to blunt the
defects and ultimately smooth the tape surface.
[0077] FIGS. 8A-8C depict an apparatus 800 for burnishing tape
media, in accordance with one embodiment. As an option, the
apparatus 800 may be implemented in conjunction with features from
any other embodiment listed herein, such as those described with
reference to the other FIGS. Of course, however, such an apparatus
800 and others presented herein may be used in various applications
and/or in permutations which may or may not be specifically
described in the illustrative embodiments listed herein. Further,
the apparatus 800 presented herein may be used in any desired
environment.
[0078] According to one embodiment as shown in FIGS. 8A-8B, the
apparatus 800 for burnishing media includes a first block 820 with
a media bearing surface 805 having a plurality of channels 806 and
lands 804, where the channels 806 and lands 804 may alternate in a
direction of media travel 816. Looking to FIG. 8B, each of the
lands 804 may have at least one skiving edge 808 along a width w in
which the width w of each land 804 extending orthogonally to the
direction of media travel 816.
[0079] Preferably, at least some of the channels 806 may be
physically configured to reduce pressure 810 in the channel to
below ambient pressure, creating a subambient condition therein,
and thereby causing the media 814 to wrap an adjacent skiving edge
808 at a wrap angle .phi. as the media 814 travels in the direction
of media travel 816 (as shown in FIG. 8B).
[0080] In some embodiments, widths w.sub.c of one or more of the
channels may be less than a width w.sub.m of the media fir which
the apparatus is designed. See FIG. 8A and the perspective view of
FIG. 8C).
[0081] Looking to FIGS. 8A-8C, in some embodiments, because ends of
the channels are closed and the widths w.sub.c of the channels are
less than the width of the media, a subambient pressure 810 is
created under the media 814 when the media moves over the channels
and entrains air out of the channel. The resultant subambient
condition induces the media 814 to deflect into the channels 806
and wrap the edges 808 at a wrap angle .phi..
[0082] In preferred approaches, the induced wrap angle .phi. may be
greater than zero degrees as measured between a plane 812 of the
tape bearing surface and a straight line 813 tangent to the tape
adjacent the edge 808 and intersecting the edge 808. See the
detailed excerpt in FIG. 8B.
[0083] According to one embodiment, the first block 820 may include
at least one hard material, for example, silicon carbide, silicon
nitride, boron nitride, sapphire, and/or diamond. In another
embodiment, the first block 820 may include at least one composite
material, for example, composite materials used in tool
fabrication, such as silicon, zirconium nitride, AlTiC, silicon
carbide, sapphire, etc.
[0084] A guide mechanism such as guides in FIG. 1A may be
configured to set a wrap angle of a tape approaching the outermost
skiving edges of the block. The guide mechanism may include, e.g.,
tape guides such as guides 125 of FIG. 1A, pitch rollers, a tension
arm, etc.
[0085] The outermost wrap angle may be set, e.g., by the guide
mechanism, to any angle that promotes the burnishing of surface
defects off the tape media surface. According to one embodiment,
the wrap angle may be at least one degree. According to preferred
embodiments, the wrap angle may be in a range of about two to about
three degrees.
[0086] Similarly, the induced wrap angle .phi. adjacent each land
is preferably greater than 0 degrees. In general, a wrap angle
higher than one degree is greater than would be used for
conventional read/write operations because the high wrap angle
results in higher friction, which is beneficial for burnishing but
is not only unnecessary for read/write operations, but excessive
friction can lead to deleterious velocity variations of the tape
during read/write operations.
[0087] The optimal wrap angle to give the best burnishing effect
may be limited by the degree of running friction of the tape media
caused by the wrap angle. According to one embodiment, each induced
wrap angle .phi. is in a range of about 0.1 to about 3 degrees, but
may be higher or lower.
[0088] Looking to FIGS. 8B-8C, the media bearing surface 805 of
each of the lands 804 may be planar, ideally with sharp, non-cusped
edges 808. The height h of the lands 804 above a base of the
channels 806 may be any value, and may be selected to provide a
vacuum that provides the desired induced wrap angle .phi.. The
height h of the lands 804 above a base of the channels 806 may be
determined using datum structures or any other conventional
technique. Exemplary values of the height h may include 0.5 microns
to 10 microns, but could be higher or lower in various
embodiments.
[0089] The length of each land as measured parallel to the
direction of media travel 816 is preferably no longer than needed
for the particular application, e.g., to reduce friction. In some
embodiments, the lengths of the lands are preferably at least 100
microns in order to allow the wrap angles to form, but could be
longer or shorter.
[0090] The length of each channel as measured parallel to the
direction of media travel 816 may be any value, but is preferably
at least as long as the length of the lands.
[0091] The channels may be formed using any suitable process. For
closed-channel embodiments such as shown in FIG. 8A, etching may be
preferred. In other approaches, the channels may be formed by
machining e.g., by sawing or grinding.
[0092] In some embodiments, the media bearing surface 805 of the
lands 804 may not be smooth, but rather have a roughened or bumpy
texture. While conventional techniques for texturing a surface may
be used, an exemplary method of roughening the lands may include
employing an air-bearing spindle saw and/or an abrasive wheel. In
other approaches, the texture may be formed on the media bearing
surface, e.g., by molding during ceramic formation. In some
approaches, about 50 nm of RA of surface roughness on the lands, or
higher, may reduce friction of the tape media running over the
lands.
[0093] According to one embodiment of a method for using the
apparatus 800, the method may involve running the media 814 over
the first block 820 in the direction of media travel 816 and/or the
opposite direction one or more times.
[0094] In some approaches, the apparatus 800 may include a
mechanism 850 for removing accumulated debris from the channels
806. See FIG. 8C. In one approach, a brush may sweep through the
channels 806 at periodic intervals. In another approach, the
mechanism may use compressed air. Further approaches may use a
fabric, swab or the like to wipe away debris. In further
approaches, a rotating, vibrating or otherwise moving mechanism may
be used. The mechanism 850 may be automated, operate on demand,
etc.
[0095] One embodiment of apparatus 800 may include a drive
mechanism such as a motor or other known mechanism that is
configured to cause the tape to move over the first block and a
controller electrically coupled to the drive mechanism. For
example, the motor or other known mechanism may drive a tape supply
cartridge, e.g., tape supply cartridge 120 of FIG. 1A, and a
take-up reel, e.g., take-up reel 121 also of FIG. 1A, of a drive in
which the block is implemented in, to move the tape media over the
block and/or other components of the drive.
[0096] FIG. 8D depicts a variant of FIG. 8A, where the channels 806
are wider than the width w.sub.m of the media 814.
[0097] In one embodiment, the apparatus may include a mechanism for
inducing a wrap angle, of greater than zero degrees, of the media
relative to media bearing surfaces of at least some of the lands.
As will be described below with reference to FIGS. 9-11, such
mechanism may include such features as a vacuum source, a second
block, applied air pressure, and combinations thereof, in some
approaches.
[0098] FIG. 9 depicts an apparatus 900 for burnishing tape media,
in accordance with one embodiment. As an option, the apparatus 900
may be implemented in conjunction with features from any other
embodiment listed herein, such as those described with reference to
the other FIGS. Of course, however, such an apparatus 900 and
others presented herein may be used in various applications and/or
in permutations which may or may not be specifically described in
the illustrative embodiments listed herein. Further, the apparatus
900 presented herein may be used in any desired environment.
[0099] According to one embodiment as shown in FIG. 9, an apparatus
900 includes channels 906 of the first block 920 having an opening
922, e.g. cylindrical holes, slots, etc, that may connect to a
vacuum source 926. The vacuum source 926 may create a subambient
condition in one or more of the channels that urges the media
toward the media bearing surfaces of the lands in the direction 924
orthogonal to the plane 812 of the media bearing surface. Each of
the lands 904 may have at least one skiving edge 908 along a width
of each land 904 extending orthogonally to the direction of media
travel 816.
[0100] According to one embodiment, the subambient condition
created by the vacuum source may induce wrap angles of the media
relative to the tape bearing surface of each land. Moreover, the
induced wrap angles may be commonly and/or individually adjusted,
e.g., to a low or high wrap angle, by controlling the amount of
vacuum applied by the vacuum source 926, potentially on a channel
by channel basis.
[0101] According to another embodiment, an apparatus for burnishing
tape media may include two blocks made of different materials or
the same materials. The lands of the upper block may push the tape
media into the channels of the lower block by pushing downward
against the back of the tape media.
[0102] FIG. 10 depicts an apparatus 1000 for burnishing tape media,
in accordance with one embodiment. As an option, the apparatus 1000
may be implemented in conjunction with features from any other
embodiment listed herein, such as those described with reference to
the other FIGS. Of course, however, such an apparatus 1000 and
others presented herein may be used in various applications and/or
in permutations which may or may not be specifically described in
the illustrative embodiments listed herein. Further, the apparatus
1000 presented herein may be used in any desired environment.
[0103] According to one embodiment as shown in FIG. 10, an
apparatus 1000 for burnishing media includes a first block 1020
with a media bearing surface extending along a plane 812. The first
block 1020 has a plurality of channels 1006 and lands 1004. The
channels 1006 and lands 1004 may alternate in a direction of media
travel 816. Each of the lands 1004 may have at least one skiving
edge 1008 along a width thereof, the width of each land 1004
extending orthogonally (into the sheet of FIG. 10) to the direction
of media travel 816. The apparatus 1000 has a second block 1030
positioned above the media bearing surface of the first block 1020.
The second block 1030 has lands 1034 positioned relative to the
first block 1020 to push the media into the channels 1006 of the
first block 1020 to cause the media to wrap the skiving edges 1008
at induced wrap angles as the media travels in the direction of
media travel 816. In some approaches, the induced wrap angles may
be set by adjusting the extent of protrusion of the lands 1034 of
the second block 1030 into the channels 1006 of the first block
1020, e.g., by using positioners with nanometer precision so that,
conversely, the second block 1030 may have channels 1036 that fit
the lands 1004 of the first block 1020. Preferably, each induced
wrap angle may be greater than zero degrees, and ideally greater
than 1 degree.
[0104] In one approach, the widths of the lands 1034 of the second
block 1030, as measured in the direction orthogonal (into the sheet
of FIG. 10) to the direction of media travel 816, may be less than
the width of the media, but the widths may be wider than the media
in other approaches.
[0105] As shown, the lands 1034 of the second block 1030 are
contoured in order to reduce interaction of the lands 1034 of the
second block 1030 with the tape media.
[0106] The height h.sub.2 of the lands 1034 of the second block
1030 may be at least as long as the height h.sub.1 of the lands
1004 of the first block 1020.
[0107] In one approach, the lands 1034 of the second block 1030 may
be aligned to the channels 1006 of the first block 1020 with guide
pins (not shown) of conventional type and arrangement.
[0108] The second block 1030 may be formed of any desired material.
In some approaches of apparatus 1000, the second block 1030 may
include composite materials used in tool fabrication, such as
silicon, zirconium nitride, AlTiC, silicon carbide, sapphire, etc.;
a ceramic material, such as, calcium titanate; etc.
[0109] FIG. 11 depicts an apparatus 1100 for burnishing tape media,
in accordance with one embodiment. As an option, the apparatus 1100
may be implemented in conjunction with features from any other
embodiment listed herein, such as those described with reference to
the other FIGS. Of course, however, such an apparatus 1100 and
others presented herein may be used in various applications and/or
in permutations which may or may not be specifically described in
the illustrative embodiments listed herein. Further, the apparatus
1100 presented herein may be used in any desired environment.
[0110] The apparatus 1100 may have similar features to the
apparatus 1000 of FIG. 10, except as provided below, and
accordingly has common numbering with FIG. 10.
[0111] The apparatus 1100 includes lands 1034 of the second block
1030 having openings 1022. e.g. cylindrical holes, slots, etc. to
allow pressurized air 1024 to flow against the media to push the
media toward the channels 1006 of the first block 1020. In some
approaches of apparatus 1000, the openings 1022 may be configured
to direct the pressurized air 1024 from the openings 1022 to
provide an air film between the lands 1034 of the second block 1030
and the media for reducing friction between the media and the
second block.
[0112] According to the embodiment shown on FIG. 11, the induced
wrap angle may be set, at least in part, by adjusting the extent of
protrusion of the lands 1034 of the second block 1030 into the
channels 1006 of the first block 1020. The induced wrap angle
formed at skiving edges 1008 of the lands 1004 of the first block
1020 as the media travels in the direction of media travel 816 may
be greater than zero degrees, and more preferably in a range of
about 0.1 to about 3 degrees.
[0113] In some embodiments, the lands 1034 of the second block 1030
are contoured without sharp edges in order to reduce interaction of
the lands 1034 of the second block 1030 with the tape media.
[0114] In the embodiment of apparatus 1100, the media bearing
surface of each of the lands 1004 of the first block 1020 may be
planar, ideally with sharp, non-cusped edges.
[0115] According to one embodiment of a method for using the
apparatus 1100, the method may involve running the media over the
first block 1020 in the direction of media travel 816 one or more
times.
[0116] One embodiment of apparatus 1100 may include a drive
mechanism such as a motor or other known mechanism that is
configured to cause the tape to move over the first block and a
controller electrically coupled to the drive mechanism. For
example, the motor or other known mechanism may drive a tape supply
cartridge, e.g., tape supply cartridge 120 of FIG. 1A, and a
take-up reel, e.g., take-up reel 121 also of FIG. 1A, of a drive in
which the block is implemented in, to move the tape media over the
block and/or other components of the drive.
[0117] In some approaches, the apparatus 1100 may include a
mechanism 1050 for removing accumulated debris from the channels
1006. In one approach, a brush may sweep through the channels 1006
at periodic intervals. In another approach, the mechanism may use
compressed air. Further approaches may use a fabric, swab or the
like to wipe away debris. In further approaches, a rotating,
vibrating or otherwise moving mechanism may be used. The mechanism
1050 may be automated, operate on demand, etc.
[0118] In another embodiment (not shown, but see FIG. 9 for
reference) the apparatus 1100 may include channels of the first
block having openings that connect to a vacuum source to urge the
media toward the media bearing surface of the lands of the first
block. Wrap angles of the media tape may be adjusted, e.g., to a
low or high wrap angle, in response to the vacuum urging the
magnetic recording tape downward.
[0119] In use, the embodiments described herein, of apparatus 800,
900, 1000, and 1100, may be employed in a media formatter, where
the servo pattern is written to the tape, or before the tape media
is used for writing, or after data has been written to the tape
media. Multiple blocks may be used. Moreover, each block may have
two or more lands, for example, 4, 16, 32, or more pairs of lands
and channels. Media may be passed in only one or in both directions
over the block(s).
[0120] It will be clear that the various features of the foregoing
systems and/or methodologies may be combined in any way, creating a
plurality of combinations from the descriptions presented
above.
[0121] It will be further appreciated that embodiments of the
present invention may be provided in the form of a service deployed
on behalf of a customer.
[0122] The inventive concepts disclosed herein have been presented
by way of example to illustrate the myriad features thereof in a
plurality of illustrative scenarios, embodiments, and/or
implementations. It should be appreciated that the concepts
generally disclosed are to be considered as modular, and may be
implemented in any combination, permutation, or synthesis thereof.
In addition, any modification, alteration, or equivalent of the
presently disclosed features, functions, and concepts that would be
appreciated by a person having ordinary skill in the art upon
reading the instant descriptions should also be considered within
the scope of this disclosure.
[0123] While various embodiments have been described above, it
should be understood that they have been presented by way of
example only, and not limitation. Thus, the breadth and scope of an
embodiment of the present invention should not be limited by any of
the above-described exemplary embodiments, but should be defined
only in accordance with the following claims and their
equivalents.
* * * * *