Dynamic magnetic information storage or retrieval – Record transport with head stationary during transducing – Disk record
Reexamination Certificate
1999-03-08
2001-04-10
Miller, Brian E. (Department: 2754)
Dynamic magnetic information storage or retrieval
Record transport with head stationary during transducing
Disk record
C360S098080
Reexamination Certificate
active
06215617
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a magnetic disk unit used as an external storage of computers and a support member for magnetic disk substrate used for this.
2. Description of the Prior Art
Hitherto, as shown in
FIG. 5
, the magnetic disk unit is fixed by inserting multiple pieces of magnetic disk substrate
12
and spacer
20
alternately into a hub
11
fixed to a rotary shaft
10
, and lastly pressing with a shim
30
and a clamp
40
and tightening with a screw
13
. And by allowing the magnetic head
14
to move on the surface of the magnetic disk substrate
12
free from contact while the magnetic disk substrate
12
is being rotated by rotation of the above rotary shaft
10
, the information is designed to be written to or read from the specified position of the magnetic disk substrate
12
.
In recent years, these magnetic disk units
50
are required to achieve an extremely small levitation rate for the distance between the magnetic head
14
and the magnetic disk substrate
12
as the densification of information increases, and for this purpose, the magnetic disk substrate
12
was formed with ceramics or glass which is highly rigid and is difficult to generate deformation, and the support member such as spacers
20
for fixing the magnetic disk substrate
12
, shims
30
, and clamps
40
were formed with ceramics or glass same as those in the case of magnetic disk substrate
12
in order to prevent deformation of the magnetic disk
12
caused by a thermal expansion difference and to reduce weight (Japanese Patent Publication No. Hei 5-80745 and Japanese Paten Application Laid Open No. Sho 61-148667).
For example, the spacer
20
for holding the magnetic disk substrate
12
to given intervals is made of alumina ceramics as shown in FIG.
8
and formed into a ring shape
21
.
On the other hand, in Japanese Patent Laid Open No. Sho 51-118408, support members such as spacers and shims are disclosed, which are designed to have a plurality of air grooves cut radially on the contact surface with the magnetic disk substrate
12
and form an air layer in the air groove in order to relieve stresses applied to the magnetic disk substrate
12
during clamping.
However, because ceramics or glass which comprises support members such as the spacer
20
, shim
30
, clamp
40
, etc. are fragile, there was a fear of generating chipping at the edge due to the stress at the time of clamping. This broken piece may damage the magnetic disk substrate
12
or break the magnetic head
14
, if it enters the clearance between the magnetic disk substrate
12
and the magnetic head
14
levitating on it.
On the other hand, with the support member designed to have air grooves cut on the contact surface and form air grooves in them, the greater the ratio of the air grooves accounting for the contact surface, the smaller is the contact surface with the magnetic disk substrate
12
, possibly resulting in strain in the magnetic disk substrate
12
. Consequently, it was unable to decrease the flatness of the magnetic disk substrate
12
at the time of clamping and it was unable to minimize the levitation rate of the magnetic head
14
. In particular, when the magnetic disk substrate
12
deforms in the shape of a letter V, the magnetic head
14
collides against the magnetic disk substrate
12
to result in breakage.
In recent years, it has been known that static electricity is charged in the magnetic disk substrate
12
when the information is read or written and noise is generated to destroy the recording contents, but charging of the magnetic disk substrate
12
was unable to be prevented because ceramics and glass are, in general, insulating materials.
Under these circumstances, in this invention, the support members such as shims, clamps, and spacers are formed with ceramics or glass and at the same time the ratio of the actual contact surface is designed to be 50-95% as well as the flatness of this contact surface is made to be 3 &mgr;m or less.
It is an object of this invention to provide a magnetic disk unit comprising one or a plurality of magnetic disk substrate arranged on a nearly cylindrical hub to be fixed to a rotating shaft via ring-form spacers and shims and held by clamps, the said magnetic disk substrate being made from ceramics or glass and held by spacers and shims whose actual contact area ratio with the magnetic disk substrate is designed to be 50-95%, wherein the flatness of the contact surface is designed to be 3 &mgr;m or less.
It is another object of this invention to provide a magnetic disk unit in which a through hole perpendicular to the contact surface of support member such as shims or clamps is drilled to dispose springs in the through hole or to fill the through hole with conductive materials or cover the surface with conductive materials in order to achieve conductivity between the top and the bottom of the contact surfaces and prevent charging of the magnetic disk.
This invention relates to a support member for magnetic disk substrate for holding the magnetic disk substrate to a specified position and a magnetic disk unit comprising one or a plurality magnetic disk substrate held to a hub by means of this.
Hitherto, as shown in
FIG. 12
, the magnetic disk unit was fixed by alternately inserting a plurality of magnetic disk substrate
115
and spacer
111
into a hub
114
fixed to a rotary shaft
113
and lastly pressing them with shims
110
and clamps
112
and tightening with screws
116
. And with the magnetic disk substrate
115
being rotated by the rotation of the rotary shaft
113
, the magnetic head
117
was allowed to move on the surface of the magnetic disk substrate
115
free from contact so that the information is written or read at a specified position of the magnetic disk substrate
115
.
In recent years, as the information density and the storage capacity increase, the magnetic disk unit
150
is required to further minimize the distance between the magnetic head
117
and the magnetic disk
115
, increase flatness of the magnetic disk substrate
115
, and improve smoothness of its surface, and, therefore, there is disclosed a magnetic disk substrate
115
using ceramics or glass, in which increased surface strength and improved surface smoothness are highly effectively achieved, and the support members such as spacers
111
, shims
110
, and clamps
112
for fixing and supporting the magnetic disk substrate
115
are formed with ceramics or glass for preventing deformation of the magnetic disk substrate
115
caused by thermal expansion difference as well as for reducing weight (Japanese Patent Publication No. Hei 5-80745, Japanese Non-examined Patent Publication No. Sho 61-148667).
However, because ceramics or glass composing the support member are, in general, insulating materials, it has recently been known that supporting the magnetic disk
115
with these support members charges the magnetic disk substrate
115
, generates noises in writing or reading the information, and possibly destroys the recording contents, and therefore, there is disclosed a method for preventing charging of the magnetic disk
115
by using the support member with the contact surface with the magnetic disk substrate
115
coated with metallic film such as aluminum, zinc, etc. (Japanese Non-examined Patent Publication No. Hei 2-226566).
However, because the support member with the contact surface coated with metallic film causes a large thermal expansion difference between the ceramics or glass constituting the substrate and the metallic film, there is a problem in which the flatness of the contact surface is impaired by the heat resulting from high-speed rotation. In addition, there is a problem of burr specific to metal. Consequently, because forming a magnetic disk unit
150
using this support member causes strain in the magnetic disk substrate
115
and impairs the parallelism between magnetic disk substrates
115
, it is unable to reduce the levitation rate of the magnetic head
117
, possibly causing the magnetic
Hino Shozi
Okumura Masahiro
Yamaguchi Shin-ichi
Hogan & Hartson LLP.
Kyocera Corporation
Miller Brian E.
LandOfFree
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