Dynamic magnetic information storage or retrieval – Head mounting – For adjusting head position
Reexamination Certificate
1997-08-26
2001-10-23
Miller, Brian E. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
For adjusting head position
C360S241100
Reexamination Certificate
active
06307718
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the field of magnetic storage devices. More specifically, the present invention relates to an apparatus for azimuth recording and zenith adjusting of a magnetic tape head.
BACKGROUND OF THE INVENTION
Tape recording and reproducing systems for use as computer data storage devices are required to provide high data transfer rates and to perform a read check on all written data. To satisfy these requirements, conventional tape systems employ various methods of recording, including linear recording, in which the tracks of data lie parallel to each other and to the edge of the tape and helical scan recording, in which the tracks of data lie parallel to each other but at an angle to the edge of the tape. The linear recording method offers higher data transfer rates; however, it is desirable to obtain higher data densities while retaining the advantages of this method.
Tape track densities are limited by crosstalk, which occurs when reading is interfered with by data of adjacent tracks. Crosstalk is exacerbated by error in head gap alignments.
A method of recording known as azimuth recording has been shown to decrease the effects of crosstalk and thus increase the track density of tape recording systems. Azimuth recording results in a recorded track pattern in which the magnetization directions of adjacent data tracks lie at different azimuth angles relative to each other. This method greatly reduces intertrack crosstalk, enabling tracks to be placed closer together.
A typical recorded track pattern resulting from the use of a tape recording system utilizing azimuth recording is shown in FIG.
1
. The tracks
7
and
9
are recorded such that the direction of magnetization of the data is at a first angle−theta relative the lateral direction of the tape
50
. Tracks
6
and
8
are recorded at a second such angle+theta.
The azimuth recording shown in
FIG. 1
is achieved through utilization of a typical magnetic head like the one shown in
FIG. 1
a
. Referring to
FIG. 1
a
, the face
61
of the magnetic head
60
contains a first column
62
of write head gaps
72
and
73
, a second column
66
of write head gaps
76
and
77
, and a third column
64
of read head gaps
74
and
75
situated between the columns
62
and
66
. The head gaps of each column are arranged such that their lengths extend in a lengthwise or longitudinal direction generally parallel to the direction of arrow
71
, as shown in
FIG. 1
a
. The write head gaps
72
and
73
, the write head gaps
76
and
77
, and the read head gaps
74
and
75
are typically arranged such that there is an end-to-end space
63
between them. Further, the corresponding head gaps in columns
62
and
66
are positioned such that the write head gaps
72
and
76
are generally laterally aligned. The read head gaps
74
and
75
in the third column
64
are offset in a lengthwise direction and distance
65
from the corresponding write head gaps in the other two columns
62
and
66
. In this arrangement, magnetic head
60
enables azimuth recording of multiple tracks at once.
As shown in
FIG. 1
b
, magnetic head
60
is typically mounted on head assembly
100
, as shown in dashed lines in
FIG. 1
b
, for lateral and stepped rotatable movement relative to a tape such as that shown in FIG.
1
. As shown, the magnetic head
60
is mounted for movement about the output shaft of a rotary motor
106
. The rotary motor
106
, which receives input from a controller
200
, serves to rotatably step the angle of magnetic head
60
relative to the tape
50
. A stepper motor
108
, which also receives signals from the controller
200
, serves to engage an actuator
107
, shown as a linear actuator in
FIG. 1
b
, for moving the magnetic head
60
in a lateral or widthwise direction across the tape
50
.
Referring to
FIG. 1
c
, during operation of a typical azimuth recording system, the magnetic tape
50
moves in a direction indicated by the arrow
79
over the magnetic head
60
. As shown on the right side of
FIG. 1
c
, the magnetic head
60
is rotated in a positive angle relative to tape
50
, denoted by +theta, bringing the write and read head gap pairs
72
and
74
, and
73
and
75
, into general alignment with tracks
52
and
54
, respectively. Write head gaps
72
and
73
write tracks
54
and
52
, respectively, on tape
50
. These tracks extend generally parallel to the edge of tape
50
. In this way tracks are recorded in which the magnetization direction of the data is at a positive azimuth angle on the tape
50
.
Referring to
FIGS. 1
c
, when the end of the tape
50
is reached, the direction of travel of the tape
50
is reversed to advance the tape
50
in the direction indicated by the arrow
78
. Stepper motor
108
activates linear actuator
107
which moves the magnetic head
60
laterally over the tape
50
to the next track position to be written. The rotary motor
106
rotatably steps the magnetic head
60
to a negative angle, denoted by −theta as shown on the left side of
FIG. 1
b
. This brings the read and write head gap pairs
74
and
76
, and
75
and
77
, into general alignment with the tracks
55
and
53
, respectively. In this position, the write head gaps
76
and
77
write the tracks
55
and
53
, respectively, which extend parallel to the edge of the tape
50
. These tracks are written at a negative azimuth angle. And again, due to the azimuth position, −theta, of the magnetic head
60
, the read head gaps
74
and
75
are able to read check all data written by write head gaps
76
and
77
respectively.
Conventional tape recording systems have employed various azimuth adjustment mechanisms. One such mechanism is disclosed in U.S. Pat. No. 4,539,615 to Arai et al. entitled, “AZIMUTHAL MAGNETIC RECORDING AND REPRODUCING APPARATUS” which describes a stepping motor and a gear box to rotate the magnetic head into the desired azimuth angle. The disadvantages of this type of mechanism, are the physical size of the gear box and the number of gears required to achieve the high gear ratios necessary for high track density recording and reproducing. The gear box decreases the efficiency and lowers the bandwidth of the mechanism, which impedes the performance of the mechanism. Furthermore, the backlash from multiple sets of gears in the gear box will induce inaccuracies in the positioning of the tracks making high track densities difficult to achieve. Backlash is created by the loss of contact between gears during changes of rotational direction. During starting and reversing of gears, backlash creates inaccuracy, particularly in a gear box, wherein backlash has a cumulative effect from each gear. Bandwidth measures the speed with which gears can change directions of rotation. Generally, smaller gears and lesser number of gears perform at higher bandwidths and are thus more desired.
As tape recording systems become increasingly smaller and the track density becomes increasingly greater, the need to limit the physical size and backlash as well as the need to increase bandwidth of head actuation mechanisms becomes critical.
In any method of tape recording, it is highly essential to position the magnetic head such that the face of the head exhibits a zero zenith, i.e. the face of the head is substantially parallel relative to the plane of the tape path. Zero zenith enables the different read/write channels of the head to make uniform and consistent contact with the tape, which enables uniformly strong signals to be read and written. In addition, the different read/write channels of the head will remain in uniform contact with the tape as the head moves up and down along the transverse direction of the tape to read and write different tracks.
In the prior art, proper zenith of the head was achieved by tightly controlling all the mounting surfaces to very tight tolerances. For example,
FIG. 2
shows a tape guide system
3
and a vertically moveable platform
2
on which a read/write head
1
is mounted. The platform
2
Harrison David B.
Miller Brian E.
Quantum Corporation
Roeder Steven G.
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