Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specific detail of storage medium support or motion production
Reexamination Certificate
1997-09-18
2001-03-20
Miller, Brian E. (Department: 2757)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specific detail of storage medium support or motion production
C360S099120
Reexamination Certificate
active
06205111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disk driving apparatus for driving a disk into rotation.
2. Description of the Prior Art
In the conventional disk driving apparatus for a disk having a circular-plate shape such as a compact disc (CD), a compact disc read-only memory (CD-ROM) or an optical magnetic disk (MO), in order to read out and write information from and to the circular-plate disk which is referred to hereafter simply as an optical disk, it is necessary to maintain the positional relationship between the optical disk and an optical pickup for implementing the operation to read out and write the information with a high degree of precision. If a positional shift occurs between the optical disk and the optical pickup, it becomes difficult to read out and write information with a high degree of accuracy. This causes problems in a playback operation, for example, the sound quality of a reproduced audio signal and the picture quality of a reproduced video signal deteriorate.
In particular, since the optical disk described above is generally made of compound resin, there are observed relatively big variations in the diameter of the hole provided at the center of the optical disk for facilitating the mounting of the optical disk on a turntable. Thus, a measure for countering these variations and, hence, for suppressing a positional shift, is absolutely required.
An example of such a countermeasure is a centering mechanism of an optical disk which is provided so as to always mount the optical disk at a correct position on the turntable.
An example of an optical-disk playback apparatus with a centering mechanism is shown in
FIGS. 5 and 6
.
FIG. 5
is a diagram roughly showing a side view of the principle components of a conventional optical-disk playback apparatus.
FIG. 6
is a diagram roughly showing a plane view of the conventional optical-disk playback apparatus shown in FIG.
5
.
As shown in
FIGS. 5 and 6
, the optical-disk apparatus
1
for playing back information from a CD comprises a spindle motor
2
, a turntable
3
and a clamp
4
.
The spindle motor
2
comprises a rotor
2
a
and a stator board
2
b
which is installed on a chassis
2
c
by screws
2
d.
The chassis
2
c
is mounted on a main-body frame of the optical-disk apparatus
1
through insulators
2
e
each made of rubber so as to prevent vibration from being propagated from the spindle motor
2
to the optical disk. It should be noted that the main-body frame itself is not shown in the figure.
The turntable
3
is fixed on the upper end of a rotational shaft
2
f
of the spindle motor
2
concentrically. An optical disk
5
can be mounted on and removed from the turntable
3
freely.
Formed at the center of the turntable
3
is a circular protrusion
3
a
used as a horizontal-direction reference for mounting the optical disk
5
with a circular-plate shape on the turntable
3
. The optical disk
5
has a circular hole
5
a
bored through the center thereof. The optical disk
5
is mounted on the turntable
3
with the protrusion
3
a
inserted through the hole
5
a.
The clamp
4
has a circular shape in the horizontal direction. At the center of the lower surface of the clamp
4
, a circular dent is formed for accommodating the protrusion
3
a
of the turntable
3
. The clamp
4
is placed above the turntable
3
and the optical disk
5
.
At the inner part of the dent of the clamp
4
described above, a magnet
4
a
is mounted. The magnet
4
a
is attracted by the upper surface of the protrusion
3
a
of the turntable
3
so that the lower surface of the circumference of the clamp
4
is pressed against a portion of the optical disk
5
facing the circumference. In this way, the optical disk
5
is sandwiched firmly between the clamp
4
and the turntable
3
, being fixed on the turntable
3
.
In addition, an optical pickup
6
for reading and writing information from and to the optical disk
5
is mounted slidably in the radial direction of the optical disk
5
along guide axes
7
a
installed on the chassis
2
c
as shown in FIG.
6
. The optical pickup is driven by a sled motor
7
b
through a sled gear
7
c
into sliding motion in the radial direction.
A centering mechanism for the optical disk
5
is provided on the protrusion
3
a
of the turntable
3
. The centering mechanism has a configuration shown in
FIGS. 7 and 8
.
FIG. 7
is a diagram showing, in an enlarged form, a cross section of the protrusion
3
a
at the center of the turntable
3
employed in the optical-disk playback apparatus shown in FIG.
5
.
FIG. 8
is a diagram showing partially, in an enlarged form, the centering mechanism of the optical disk
5
on the turntable
3
.
As shown in
FIGS. 7 and 8
, the protrusion
3
a
at the center of the turntable
3
includes a base
8
a,
a ring
8
b,
a coil spring
8
c
and a chalking yoke
8
d.
The base
8
a
is created at the center of the turntable
3
to enclose a bearing pressed against the rotational shaft
2
f
of the spindle motor
2
. The base
8
a
is engaged with and fixed to the bearing. The coil spring
8
c
is engaged with the base
8
a
and the ring
8
b
is engaged with the coil spring
8
c
from a position above the coil spring
8
c.
On the upper edge of the base
8
a,
the chalking yoke
8
d
having a ring-like shape is provided for attracting the magnet
4
a
of the clamp
4
. In the embodiment shown in the figures, the chalking yoke
8
d
is created to form a single body with the base
8
a.
The chalking yoke
8
d
has an inner diameter smaller than the outer diameter of the ring
8
b
and a circumferential edge bent downward along the entire circumference thereof.
The inner diameter of the ring
8
b
is made slightly larger than the outer diameter of the base
8
a
by such a difference that the ring
8
b
can be moved up and down relatively to the base
8
a
with the inner circumferential surface of the ring
8
b
sliding over the outer circumferential surface of the base
8
a
with no backlash with respect to the base
8
a.
The outer surface of the ring
8
b
is inclined downward on the outer side in the radial direction thereof. That is to say, the ring
8
b
has a conical shape which has a minimum outer diameter and a maximum outer diameter on the top and bottom surfaces thereof respectively.
In addition, the ring
8
b
is created so that the outer diameter at a middle position between the top and bottom surfaces thereof is about equal to the diameter of the circular hole
5
a
bored through the center of the optical disk
5
to be mounted.
On the lower surface of the ring
8
b,
a continuous groove having a ring shape is created in the circumferential direction. The upper end of the coil spring
8
c
is plugged into the groove.
Thus, by bringing the upper end of the coil spring
8
c
into contact with the inner part of the groove, the ring
8
b
is pressed by the coil spring
8
c
in the upward direction.
Here, the upper limit of the position of the ring
8
b
is determined when the upper surface of the ring
8
b
comes in contact with the lower edge of the bent circumference of the chalking yoke
8
d.
When no optical disk
5
is mounted, the ring
8
b
is held at the upper limit of the position by the tension of the coil spring
8
c.
When an optical disk
5
is mounted on the turntable
3
having a centering mechanism with such a configuration, first of all, the lower edge of the hole
5
a
of the optical disk
5
is brought into contact with a circumferential portion of the ring
8
b
in close proximity to the middle between the top and bottom circumferential surfaces of the ring
8
b
as shown in FIG.
8
. The ring
8
b
is pulled downward by the weight of the optical disk
5
, resisting the tension of the coil spring
8
c.
Later on, as the clamp
4
is engaged with the protrusion
3
a
of the turntable
3
as described above, the magnet
4
a
of the clamp
4
is attracted by the chalking yoke
8
d.
In this way, the optical disk
5
is further pulled by a pressure generated by the chalking yoke
8
Fields Kenneth W.
Kananen Ronald P.
Miller Brian E.
Rader Fishman & Grauer
Sony Corporation
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