Dynamic magnetic information storage or retrieval – Fluid bearing head support – Disk record
Reexamination Certificate
1999-09-30
2002-03-12
Klimowicz, William (Department: 2652)
Dynamic magnetic information storage or retrieval
Fluid bearing head support
Disk record
C360S236600
Reexamination Certificate
active
06356412
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to air bearing sliders for use in magnetic head assemblies and in particular to air bearing slider geometry.
2. Background of the Invention
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 systems
10
of the prior art includes a sealed enclosure
12
, a disk drive motor
14
, a magnetic disk
16
, supported for rotation by a drive spindle S
1
of motor
14
, an actuator
18
and an arm
20
attached to an actuator spindle S
2
of actuator
18
. A suspension
22
is coupled at one end to the arm
20
, and at its other end to a read/write head or transducer
24
. The transducer
24
(which will be described in greater detail with reference to
FIG. 2A
) typically includes an inductive write element with a sensor read element. As the motor
14
rotates the magnetic disk
16
, as indicated by the arrow R, an air bearing is formed under the transducer
24
causing it to lift slightly off of the surface of the magnetic disk
16
, or, as it is termed in the art, to “fly” above the magnetic disk
16
. Alternatively, some transducers, known as “contact heads,” ride on the disk surface. Various magnetic “tacks” of information can be written to and/or read from the magnetic disk
16
as the actuator
18
causes the transducer
24
to pivot in a short arc as indicated by the arrows P. The design and manufacture of magnetic disk data storage systems is well known to those skilled in the art.
FIG. 2
depicts a magnetic read/write head
24
including a substrate
25
above which a read element
26
and a write element
28
are disposed. Edges of the read element
26
and write element
28
also define an air bearing surface ABS, in a plane
29
, which can be aligned to face the surface of the magnetic disk
16
(see FIGS.
1
A and
1
B). The read element
26
includes a first shield
30
, an intermediate layer
32
, which functions as a second shield, and a read sensor
34
that is located within a dielectric medium
35
between the first shield
30
and the second shield
32
. The most common type of read sensor
34
used in the read/write head
24
is the magnetoresistive (AMR or GMR) sensor which is used to detect magnetic field signals from a magnetic medium through changing resistance in the read sensor.
In magnetic disk technologies, it is generally desired to achieve higher data recording densities. In the context of the air bearing slider, one way of achieving increased recording densities is by maintaining a low flying height. Maintaining a low flying height requires that, pitch angle and roll angle be held constant over the whole disk surface.
On the one hand, the read/write head
24
must fly at a sufficient height to avoid frictionally related problems caused by physical contact during data communication between the head
24
and the rapidly rotating disk
16
. On the other hand, the head
24
should be made to fly as low as possible to obtain the highest possible recording densities. Accordingly, it is preferred that the slider fly as close as possible to the disk surface without actually contacting the disk surface. A constant flying height is preferably maintained, regardless of variations in tangential velocity of the disk
16
during flying, cross movements of the head
24
during data search operations, and changes in skew angle in the case of rotary type actuators.
FIG. 3A
is a schematic perspective view of a conventional tapered flat slider
300
. Two rails
302
are formed in parallel at a predetermined height on a surface of a slim hexahedron body
304
to thus form lengthwise extending air bearing surface rails (ABS rails)
305
. A tapered or sloped portion
306
is formed at each leading edge portion of the ABS rails
305
. In such a structure, air within a very thin boundary layer rotates together with the rotation of the disk due to surface friction. When passing between the rotating disk and the slider, the air is compressed by the sloped portion
306
on the leading edge of the ABS rails
305
. This pressure creates a hydrodynamic lifting force at the ramp section which is sustained through the trailing edge of the ABS, thus allowing the slider to fly without contacting the disk surface.
The conventional slider of this type suffers a drawback in that the flying height, pitch angle and roll angle vary considerably according to the skew angle of the rotary type actuator, i.e. according to the radial position of the slider over the disk surface. In addition, rapid movement of the actuator arm
20
can cause variations in slider pitch. With reference to
FIG. 3B
, In order to overcome these variations in slider pitch and to ensure a stable and low level fly height, prior art ABSs have been provided with a cross rail
308
, oriented perpendicular to the direction of airflow and located toward the leading edge of the slider. Such a cross rail serves to create a negative or sub-ambient pressure there behind which forces the slider downward. Ideally the downward pressure from the cross bar balances with the upward forces under the rails and a stable fly height is achieved.
When the time comes to terminate use of the data storage system
10
the head
24
must be stored. One prior method referred to in
FIG. 3C
is known to those skilled in the art as contact start stop (CSS). With the CSS system, upon powering down the system
10
, the head
24
lands upon the disk
16
. The disk of this system is provided with a landing zone
310
. The surface of the landing zone has small bumps, formed with a laser, which prevent the head from sticking to the surface of the disk. The remainder of the disk provides a data zone
312
on which data can be recorded or read. Since any area consumed by the landing zone detracts from available data zone area, in order to increase the total amount of data which can be stored on the disk
16
it is desirable to reduce or eliminate the landing zone
310
in order to increase the data zone.
With reference to
FIG. 3D
, one method for eliminating the need for a landing zone
310
, is called a load/unload system. A landing ramp
314
is provided on which the suspension arm
22
can rest allowing the head
24
to suspend in mid air during non-use. This method advantageously protects the head
24
and recording medium
16
by eliminating the need to contact the head with the medium. However, this method creates other problems in that during unload of the head
24
from the recording medium
16
the sub-ambient pressure tends to resist unloading of the head.
As the head
24
is lifted from the recording medium
16
, the high pressure and sub-ambient pressure under the air bearing surface both decrease. However, prior art air bearing designs exhibit an unequal reduction of the pressures as the head
24
is unloaded. The sub-ambient pressures tend to decrease at a significantly lower rate than the high pressures as the distance between the head
24
and the recording medium
16
increases. This creates a net sub-ambient force during unload. In some cases the sub ambient force can be sufficient to cause plastic deformation of the head suspension
22
, permanently damaging the system
10
, and can cause dimpling of the recording medium
16
. Furthermore, the excessive sub-ambient pressure can cause a spring back effect when the sub-ambient pressure is finally overcome, causing the head
24
to severely impact the recording medium
16
damaging both the recording medium and the head.
Thus there remains a need for an ABS having exceptional flight profile characteristics which also exhibit good load and unload characteristics. Such a head would not experience excessive sub-ambient pressures during unload and would preferably be useable in either CSS or load/unload systems.
SUMMARY OF THE INVENTION
The present invention provides an air bearing surface (ABS) for use with a magnetic read/write head. The air bearing surface includes a pair of side rails def
Anaya-Dufresne Manuel
Dong Jesse Jianxian
Gan Wuxing
Levi Pablo G.
Carr & Ferrell LLP
Hayden Robert D.
Klimowicz William
Read-Rite Corporation
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