Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
1999-07-22
2001-10-23
Cao, Allen (Department: 2652)
Dynamic magnetic information storage or retrieval
Record medium
Disk
C360S133000
Reexamination Certificate
active
06307713
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to improvements in a center core installed to the center portion of a disc-shaped recording medium and used for the purpose of making a so-called magnetic chucking for the disc-shaped recording medium to a turn table of a disc drive device, and additionally to a production process for the center core.
2. Description of the Prior Art
Hitherto a variety of center cores for disc-shaped recording mediums have been proposed and put into practical use. Of these center cores, one shown in
FIG. 14
has been known, in which the center core
101
includes a flange section
102
for supporting a disc-shaped recording medium
201
. A generally cylindrical section
103
having a bottom wall
103
is formed radially inward of the flange section
102
. The cylindrical section
103
is formed at the central portion of the bottom wall with a supportable surface
104
through which the center core
101
is mounted on a turn table
401
of a disc drive device which will be shown in
FIGS. 22
to
27
. A projecting section
105
is formed radially outward of the supportable surface
104
. A spindle shaft insertion hole
106
is formed at the central portion of the above-mentioned supportable surface
104
. A drive pin engaging hole
107
is formed radially outward of the spindle shaft insertion hole
106
and located to extend throughout the supportable surface
104
and the projecting section
105
for adjusting the magnetic attraction force.
This conventional center core
101
is produced as follows:
At a first step shown in
FIGS. 15A and 15B
, a pilot through-hole
302
is formed at its central portion of a sheet
301
of a magnetic metal such as stainless steel or the like. Additionally, a plurality of arcuate cutouts
304
are formed along a circle (not shown) whose center corresponds to the center of the pilot through-hole
302
. Accordingly, the arcuate cutouts
304
are circularly arranged in which a non-cutout or flat wall portion
303
is formed between the adjacent arcuate cutouts
304
.
At a second step shown in
FIGS. 16A and 16B
, the flange section
102
and the cylindrical section
103
having the bottom wall are formed by making a press working on a radially inward side relative to the circularly arranged cutouts
304
. The cylindrical section
103
formed projecting toward a lower surface side of the center core
201
.
At a third step shown in
FIGS. 17A and 17B
, burring is applied to the pilot through-hole
302
thereby forming the spindle shaft insertion hole
106
.
At a fourth step shown in
FIGS. 18A and 18B
, a drive pin engaging hole
107
is formed to be located radially between the spindle shaft insertion hole
106
and a peripheral cylindrical wall of the cylindrical section
103
.
At a fifth step shown in
FIGS. 19A and 19B
, a press working is made on the bottom wall of the cylindrical section
103
in a direction from a lower surface side of the metal sheet
301
so as to cause a central portion of the cylindrical section
103
to project toward the upper surface side of the metal sheet
301
. Accordingly, a shallow dish-shaped generally cylindrical section
104
having a top wall is formed at the central portion of the cylindrical section
103
. Simultaneously, an annular projecting section
105
is formed along the outer periphery of the shallow dish-shaped cylindrical section
104
in a manner to surround the shallow dish-shaped cylindrical section
104
. The projecting section
105
functions to adjust a magnetic attraction force to be applied to the center core
101
.
At a sixth step shown in
FIGS. 20A and 20B
, the circularly arranged arcuate non-cutout portions
303
are cut out thereby separate the center core
101
from the metal sheet
301
. The above-mentioned top wall of the cylindrical section
104
serves as a supportable surface
104
a
through which the center core
101
is mounted on the turn table.
As shown in
FIGS. 21A and 21B
, the cylindrical section
103
of the center core
101
is inserted into a core installation hole
201
a
formed at the central portion of a disc-shaped recording medium
201
in a direction from the upper surface side of the disc-shaped recording medium
201
, so that the flange section
102
is placed on the upper surface of the disc-shaped recording medium
201
. At this time, the flange section
102
of the center core
101
is bonded to the upper surface of the disc-shaped recording medium with an adhesive
202
thereby maintaining the central portion of the disc-shaped recording medium
201
. In other words, the center core
101
is installed to the central portion of the disc-shaped recording medium
201
.
As shown in
FIGS. 22 and 23
, the projecting section
105
for adjusting the magnetic attraction force is attracted by a magnet
402
installed to the turn table
401
of a disc driving device, in which the supportable surface
104
a
is positioned on a core support surface
403
. At this time, a spindle shaft
404
located at the central portion of the core support surface
403
is inserted into the spindle shaft insertion hole
106
, while a drive pin
405
disposed radially outward of the core support surface
403
is brought into engagement with the drive pin engagement hole
107
. As a result, rotation of the turn table
401
is transmitted to the center core
101
.
FIG. 22
illustrates a case where the diameter of the core support surface
403
of the turn table
401
of the disc drive is formed relatively small or the minimum, while
FIG. 23
illustrates a case where the diameter of the core support surface
403
is formed relatively large or the maximum.
However, the following drawbacks have been encountered in the above conventional center core
101
:
(a) The supportable surface
104
a
is formed annular and around the spindle shaft insertion hole
106
. The supportable surface
104
a
is adapted to be in direct contact with the core support surface
403
, and therefore it is required that a whole area of the supportable surface
104
a
which area contacts with the core support surface
403
have a high surface precision. Accordingly, in this case, it is difficult to have the high surface precision throughout the whole area as compared with a case where only a part is required to have such a high surface precision.
(b) Although it is ideal that the supportable surface
104
a
is formed as a flat horizontal plane, the supportable surface
104
a
is in fact inclined to form an inclined generally frustoconical surface which rises in a direction of from the outer peripheral portion toward the central spindle shaft insertion hole
106
with a gentle slope, as shown in
FIGS. 24 and 25
. Such inclination of the supportable surface
104
a
is unavoidably formed under the phenomenon of springback of the metal sheet when a press working is made on the metal sheet during production of the center core
101
. When the supportable surface
104
a
of the above inclined shape is placed on the core support surface
403
of the minimum diameter as shown in
FIG. 24
, the projecting section
105
for adjusting magnetic attraction force, located radially outward of the supportable surface
104
a
is brought into contact with the upper surface of the magnet
402
of the turn table
401
. As a result, the center core
101
will float or separate upward from the core support surface
403
of the turn table
401
. Otherwise, in a case where the center core
101
is placed on the core support surface
304
having the maximum diameter as shown in
FIG. 25
, the projecting section
105
for adjusting magnetic attraction force may be prevented from contacting with the upper surface of the magnet
402
; however, a clearance &dgr; between the projecting section
105
and the magnet
402
becomes smaller so that the magnetic attraction force obtained by the magnet
402
will change.
Besides, as shown in
FIGS. 26 and 27
, the disc-shaped recording medium
201
is unavoidably lowered to a level lower than a standard level indicated by a dot-dash line. As
Meguro Hiroshi
Miyata Kiyoyuki
Cao Allen
Frommer William S.
Frommer & Lawrence & Haug LLP
Ryan Matthew K.
Sony Corporation
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