Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specific detail of storage medium support or motion production
Reexamination Certificate
1995-05-03
2001-06-26
Ometz, David L. (Department: 2652)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specific detail of storage medium support or motion production
C369S291100
Reexamination Certificate
active
06252842
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a recording disc for information signals, such as an optical disc or a magneto-optical disc, and a disc chucking apparatus for chucking the recording disc to a disc recording and/or reproducing apparatus.
2. Description of Related Art
A recording disc for recording and/or reproducing information signals, such as an optical disc or a magneto-optical disc, has heretofore been known and put to practical use. Referring to
FIG. 1
, the recording disc includes a disc substrate
201
, formed of a light-transmitting material, such as polycarbonate resin, and a recording layer, such as a layer of a metal or a magnetic material, is deposited on a major surface of the disc substrate
201
. A light beam is irradiated on the other major surface of the substrate, that is the major surface thereof opposite to the surface on which the recording layer is deposited for recording or reproducing the information signals on or from the recording layer.
The disc substrate
201
is formed with a center hole
202
to permit the disc to be held by a recording and/or reproducing apparatus adapted for recording and/or reproducing the information signals on or from the recording disc. The center hole
202
is formed in the disc substrate
201
so that the center of the center hole
202
is in register with the center of curvature of recording track(s) formed concentrically or spirally on the recording layer.
The recording disc is set on a disc table
204
in the recording and/or reproducing apparatus. The disc table
204
is in the form of a disk larger in diameter than the center hole
202
and is mounted on the distal end of a shaft
203
of a spindle motor, not shown. A setting portion
204
a
, on which the disc substrate
201
of the recording disc is set, is formed on the upper peripheral surface of the disc table
204
, that is on the major surface of the disc table
204
situated in the direction of projection of the distal end of the driving shaft
203
.
A centering member
205
is reciprocably mounted at the center of the disc table
204
. The centering member
205
is in the form of a cone gradually tapered towards the distal end of the rotating shaft
203
and has an outside diameter substantially corresponding to the diameter of the center hole
202
. The centering member
205
is elastically biased in the direction of the distal end of the rotating shaft
203
by a compression coil spring, not shown.
When loaded in the recording and/or reproducing apparatus, the recording disc is set on the disc table
204
and is thrust, by a chucking unit, not shown, towards the disc table
204
, so that the mid part of the major surface of the disc is abutted against the setting portion
204
a.
That is, with the recording and/or reproducing apparatus, a so-called self alignment or centering operation is achieved by the inner periphery of the center hole
202
sliding on the outer peripheral surface of the centering member
205
.
The recording disc may be self-aligned in this manner even if it is offset with respect to the centering member
205
by a distance corresponding to the width of the outer peripheral surface
205
a
of the centering member
205
along the major surfaces of the disc substrate
201
, as indicated by dimension b in
FIGS. 1 and 2
, as disclosed for example in U.S. Pat. No. 4,340,955.
If, in the recording and/or reproducing apparatus, the recording disc is to be held more reliably and satisfactorily, the self-alignment or centering operation needs to be achieved even if the amount of offset of the recording disc with respect to the centering member
205
is increased when the recording disc is set on the disc table
204
. To this end, the width of the outer peripheral surface
205
a
of the centering member
205
along the major surface of the disc substrate
201
needs to be increased.
However, if the width of the outer peripheral surface
205
a
of the centering member
205
along the major surface of the disc substrate
201
is increased in this manner, the slant of the outer peripheral surface
205
a
with respect to the major surfaces of the disc substrate
201
becomes more gentle, so that the inner peripheral surface of the center hole
202
becomes more difficult to slide along the outer peripheral surface
205
a.
The result is that the amount of shifting of the disc for centering is insufficient so that a satisfactory self-alignment or centering is not achieved.
Thus, for achieving satisfactory self-alignment, it is necessary to increase the width of the outer peripheral surface
205
a
in a direction along the major surfaces of the disc substrate
201
, while maintaining the slant of the surface
205
a
with respect to the major surfaces of the disc substrate
201
. To this end, it is necessary to increase the height, shown by an arrow h in
FIG. 2
, of the surface
205
a
in a direction normal to the major surfaces of the disc substrate
201
.
If the height of the surface
205
a
in the direction normal to the major surfaces of the disc substrate
201
is increased, the centering member
205
is protruded on the major surface of the disc substrate
201
opposite to the disc table setting major surface via the disc substrate when the disc is set on the disc table
204
. If the centering member
205
is protruded in this manner on the major surface of the disc substrate opposite to the disc table setting major surface when the disc is held by the recording and/or reproducing apparatus, the disc rotating unit inclusive of the disc table is increased in height, so that the recording and/or reproducing apparatus is correspondingly increased in size.
On the other hand, when the recording disc is housed in a thin casing-like disc cartridge, there is a risk of the centering member
205
being abutted against the inner surface of a cartridge body of the disc cartridge when the recording disc is loaded on the disc table
204
. In order for the centering member
205
not to be protruded towards the major surface of the disc substrate
201
opposite to the disc table setting major surface to thereby avoid the contact of the centering member with the inner surface of the cartridge body, the cartridge body needs to be increased in size, thus leading to an increased size of the disc cartridge.
OBJECT AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a recording disc which may be loaded reliably and satisfactorily on the disc table without increasing the size of the recording and/or reproducing apparatus and without increasing the size of the disc cartridge when the disc is used in conjunction with the disc cartridge.
It is another object of the present invention to provide a chucking device which is conceived for assuring correct centering of the recording disc.
A recording disc according to the present invention for use with a disc recording and reproducing apparatus of the type having a disc chucking device which includes a spring biased, conically shaped centering member mounted coaxially on a drive spindle, comprises a disc substrate contained in a cartridge and having a recording surface, a center hole which has a diameter smaller than a base diameter of the conically shaped centering member, and an annular rib which depends from a lower surface of the disc substrate toward the disc chucking device for seating on a disc setting member and which enlarges the thickness of the disc substrate, in the direction of the axis of rotation of the spindle, around the periphery of the center hole. Because of this, the centering member can have a steeper slope compared to prior art centering members, and thereby provide more effective centering action, and yet when the disc substrate is supported by the annular rib on the disc setting member no part of the disc chucking device extends through the center hole of the disc substrate above its upper surface.
Another aspect of the invention is the combination of a recording disc and a disc recording and reproducing apparatus for recording
Chen Tianjie
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ometz David L.
Sony Corporation
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