Dynamic magnetic information storage or retrieval – Head mounting – For shifting head between tracks
Reexamination Certificate
1999-12-15
2003-11-18
Renner, Craig A. (Department: 2652)
Dynamic magnetic information storage or retrieval
Head mounting
For shifting head between tracks
Reexamination Certificate
active
06650506
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to magnetic disk data storage systems, and more particularly to systems utilizing multiple disks and multiple read/write heads.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In
FIGS. 1A and 1B
, a magnetic disk data storage system of the art is illustrated which includes a sealed enclosure
12
and a plurality of magnetic disks
14
each of which has an upper surface
16
and a lower surface
18
. The disks are supported for rotation by a spindle
20
of a motor
22
.
An actuator
24
, includes an E-block
25
having at a distal end a plurality of actuator arms
26
. The actuator
24
also includes a bearing
27
which mounts the actuator
24
pivotally within the enclosure
12
and further includes a voice coil
28
at its proximal end. The voice coil
28
is disposed between a pair of magnets
30
which are fixedly connected with respect to the enclosure
12
. Generating an electrical current in the coil
28
induces a magnetic field about the coil. Interaction between the magnetic fields of the coil
28
and the magnets
30
provides a desired, controlled pivotal movement of the actuator about a pivot point
31
of the bearing.
The actuator arms
26
support a plurality of suspensions
32
, each of which supports at its distal end a magnetic head
34
. Each suspension
32
holds its corresponding magnetic head
34
in close proximity to a surface of one of the disks
14
to facilitate reading and recording data to and from the disk
14
.
With reference now also to
FIGS. 2A and 2B
, as well as to
FIGS. 1A and 1B
, the suspension
32
includes suspension trace circuitry
36
which conducts electrical signals from the head
34
to a set of contacts
38
along an edge of the suspension
32
. A bridge flex connector
40
, having trace circuitry
41
, electrically connects the suspension trace circuitry
36
with circuitry
42
(see
FIG. 1A
) attached to the E-block
25
. The heads
34
, suspensions
32
, bridge flex connectors
40
and E-block
25
with E-block circuitry
42
together form a Head Stack Assembly
44
(HSA).
The motor
22
and spindle
20
cause the disks
14
to rotate. As the disks
14
rotate, the air immediately adjacent the disks
14
moves with the disks
14
as a result of friction and the viscosity of the air. This moving air passes between each of the heads
34
and its adjacent disk surface
16
,
18
forming an air bearing. This air bearing causes the head to fly a very small distance from the disk surface
16
,
18
.
With reference to
FIGS. 2C and 2D
, as well as
FIGS. 1A and 1B
, each of the heads
34
includes a read element
46
and a write element
48
(FIG.
2
E). As the disk surface
16
or
18
moves past the head
34
the write element
48
generates a magnetic field leaving magnetic data on the passing disk
14
. Such write elements are generally in the form of an electrical coil
50
passing through a magnetic yoke
52
. As a current passes through the coil
50
it induces a magnetic field which in turn generates a magnetic flux in the yoke
52
. A gap (not shown) in the yoke causes the magnetic flux in the yoke to generate a magnetic field which fringes out from the gap. Since the gap is purposely located adjacent the disk, this magnetic fringing field imparts a magnetic data onto the passing magnetic disk
14
.
With continued reference to
FIGS. 2C and 2D
, to read data from a disk
14
, the read element
46
detects changes in surrounding magnetic fields caused by the disk
14
passing thereby. Several read elements have been used to read such data. A very effective read element currently in use is a GMR Spin Valve sensor. Such sensors take advantage of the changing electrical resistance exhibited by some materials when a passing magnetic field affects the magnetic orientation of adjacent magnetic layers. At its most basic level, a GMR spin valve includes a free magnetic layer and a pinned magnetic layer separated by a non-magnetic layer such as copper. The pinned layer has magnetization which is pinned in a pre-selected direction. The free layer, on the other hand, has a direction of magnetization which is perpendicular with the pinned layer, but is free to move under the influence of an external magnetic field such as that imparted by a passing magnetic recording medium. As the angle between the magnetic directions of the free and pinned layers changes, the electrical resistance through the sensor changes as well. By sensing this change in electrical resistance, the magnetic signal passing by the read element can be detected.
With continued reference to
FIGS. 2A and 2C
, in order to deliver an electrical signal to the write element or to receive an electrical signal from a read element, a set of electrical head contacts
54
are provided in the surface at the distal end of the head
34
. These contacts
54
connect with the suspension trace circuitry
36
at the distal end of the suspension
32
. The suspension
32
and the actuator arm
26
together form an arm assembly
33
.(see FIGS.
1
A and
1
B).
The process of manufacturing the heads
34
and assembling them onto an arm assembly
33
causes slight variations in the magnetic directions of free and pinned layers of the spin valve. These changes can have devastating effects on the performance of the read element. In order to ensure correct alignment of the magnetic layers, after all of the Head Stack Assemblies (HSAs)
44
have been assembled the assemblies are passed through a carefully controlled magnetic field which ensures proper alignment of the magnetization within the read element. This process is known as Head Stack Assembly Reinitialization (HSA Reinitialization).
Please note that as used in the following discussion, and throughout this specification, the term “configuration” will be used to refer to the sequence of read elements and write elements and their contacts in a given head, and this configuration shall not chance regardless of the direction that this head is facing. The term “orientation” will refer to the order or sequence of elements or contacts presented by a head as it faces in different directions, i.e. facing upwards or downwards.
Note also that there will be a distinction made between an “up head” of the prior art and an “upward facing head”, and likewise a distinction between a “down head” of the prior art and a “downward facing head”, so that an up head may be used as a downward facing head, or a down head as an upward facing head. In the prior art, up heads and down heads required usually mirror image configurations. For example, an up head
34
a
facing downward may have a configuration of R−, R+, W− and W+, as shown by the symbols in boxes in
FIG. 2D
, and a down head
34
B, also facing downward in the figure, would then have a configuration of W+, W−, R+ and R−, as also shown by the symbols in boxes in FIG.
2
C. The “configurations” of the up and down heads do not change when the up heads and down heads are turned to face downward. In terms of their “orientation”, however, the sequences do change, so that an up head now facing upward would now have an orientation of W+, W−, R+ and R−, shown by the symbols in parentheses in
FIG. 2D
, while a down head, now facing upward, would have an orientation of R−, R+, W− and W+, as shown by the symbols in parentheses in FIG.
2
C.
Simply put, for this discussion, “configuration” is fixed by manufacture and “orientation” is achieved by turning the head rightside-up or upside-down.
Also, please note that for the sake of clarity in this discussion, the term “matching” will be used in describing a configuration of head, especially in the prior art, which is used in the same orientation for which its configuration is named (i.e., an up head facing upward or a down head used facing downwards). The term “non-matching” shall be used for the opposite cases (i.e. an up head facing
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