Electricity: measuring and testing – Magnetic – Magnetic information storage element testing
Reexamination Certificate
1999-08-06
2001-05-08
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Magnetic information storage element testing
C360S097030
Reexamination Certificate
active
06229304
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to spinstands, in particular, to an apparatus for stabilizing the airflow near and around the disks mounted on and spun by the spindle of a spinstand.
BACKGROUND OF THE INVENTION
A magnetic head and disk tester is an instrument that is used for testing the characteristics of magnetic heads and disks such as a signal-to-noise ratio, track profile, etc. The tester should simulate those motions of the head with respect to the disk and the same rotational speeds of the disks that occur in an actual hard disk drive during operation. Each tester consists of two components, i.e., a mechanical component, commonly referred to as a spinstand, that performs movements of the head with respect to the disk, and an electronic component that is responsible for measurement, calculation, and analysis of the measured signal. The spinstand is also a mechanical component of a servo-writer, an instrument that is used for writing servo information on a magnetic disk, as well as a component of a flying height tester; an instrument used for measuring the flying height of a head over the disk.
A typical prior art spinstand for a head and disk tester is illustrated in
FIG. 1
(front view) and
FIG. 2
(top view). The spinstand includes a stationary base plate
10
that supports walls
12
a
,
12
b
,
12
c
. The walls
12
a
,
12
b
,
12
c
in turn support a spindle
13
for carrying one or more magnetic disks
14
. The spindle
13
and disks
14
are rotated by a spindle motor
15
.
The base plate
10
further supports first and second slide motors (not shown). The first slide motor moves a slide
16
along rails
17
a
,
17
b
in the Y direction (see FIG.
2
). Two additional rails,
18
a
,
18
b
, are mounted on top of slide
16
. The second slide motor controls movement of a second slide
19
along rails
18
a
,
18
b
in the X direction. The first and second motors cooperate to position a rotary positioner
20
mounted on slide
19
to a specified location with respect to the center of spindle
13
. Rotary positioner
20
carries and positions magnetic head(s)
22
relative to disk(s)
14
.
As the density of magnetic recording increases, additional information tracks are compressed into a given disk area. The decrease in track size heightens the demand for improved accuracy in head positioning. Likewise, the rotational speeds of the magnetic disks increase in order to achieve shorter access times. In addition, more disks are added to the disk stack to provide additional storage.
As the disk(s) rotate they cause the air around them to circulate, which creates a region of low pressure surrounding the disk(s). Due to this low pressure, air is drawn in from the top and bottom surfaces of the disk(s) and is moved outward from the spindle center. The air flow generates vortexes that induce vibrations in both the disks and the magnetic heads. These vibrations increase track misregistration. As the rotational speeds increase, vortexes generated by the rotating disk(s) increase significantly, and the vibrations and track misregistration reach unacceptable levels. Track misregistration is further exacerbated due to the change of the ambient temperature, which results in the expansion, or contraction of the magnetic disk. Furthermore, with more disks in the stack, the stack has a higher propensity to vibrate, causing further track misregistration. In some cases, track misregistration reaches unacceptable levels at which spinstand operation becomes unreliable.
Electromagnetic shielding is a further important consideration because electromagnetic radiation in the air tends to increase the noise level and degrade the quality of the signal read from the magnetic disk.
In spinstands, there is a danger of the magnetic disk(s) breaking or becoming detached from the spindle, due to mechanical defects in the material of the disk(s) and/or a failure of the clamping mechanism that is used to hold the magnetic disk(s) on the spindle. With increasing rotational speeds of the magnetic disks, this danger and the risk of injury to the operator of the spinstand increases.
Spinstands are usually operated in clean room environments as it is necessary to protect the magnetic disks and the heads from contamination. The contamination can occur due to dust particles in the air, or by accidental contact of the operator with the heads and disks.
SUMMARY OF THE INVENTION
The present invention is directed to an apparatus and method which mitigates the aforementioned prior art limitations.
It is an object of the present invention to provide a spinstand that significantly decreases the track misregistration due to vibrations caused by vortexes generated by the rotating disks, by stabilizing the airflow around the disk(s) and the spindle, and by reducing the heat exchange between the ambient air and the magnetic disk(s).
Another object of the invention is to provide the aforementioned spinstand that increases the quality of the signal read from the magnetic disk(s) by providing electromagnetic shielding for the disk(s) and head(s) installed on the spinstand.
Another object of the invention is to provide the aforementioned spinstand that substantially reduces the risk of operator injury due to the magnetic disk(s) breaking or becoming detached from the spindle.
Still another object of the invention is to provide the aforementioned spinstand that reduces the risk of accidental contact of the operator with the heads and disks, thus decreasing the chance of contamination.
More specifically, the invention employs a shroud which substantially encompasses the spindle and the disk(s) of the spinstand. This shroud reduces and/or eliminates the air flow drawn toward the top and the bottom surfaces of the disk(s), and limits the total air volume that is moved by the rotating disk(s). Air flow is directed in a circular path around the spindle center. As a result, vortexes in the air surrounding the disks are significantly reduced, thereby decreasing the vibrations of the disk(s) and heads, and decreasing track misregistration. The shroud further reduces the heat exchange between the ambient air and the magnetic disk(s), which reduces thermal expansion of the disk(s) and thus further decreases track misregistration.
The shroud also provides electromagnetic shielding for the disk(s) and head(s) installed on the spinstand and thus increases the quality of the signal read from the magnetic disk(s).
Since the shroud covers the rotating disk(s), it further offers the advantage of a reduction of the risk of operator injury due to the magnetic disk(s) breaking or becoming detached from the spindle, and further reduces the risk of accidental contact of the operator with the heads and disks, thus decreasing the chance of contamination.
REFERENCES:
patent: 4660110 (1987-04-01), Iida et al.
Guzik Technical Enterprises
McDermott & Will & Emery
Patidar Jay
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