Dynamic information storage or retrieval – Storage medium structure – Specified center hole or locating structure
Reexamination Certificate
2000-03-01
2001-04-03
Klimowicz, William (Department: 2754)
Dynamic information storage or retrieval
Storage medium structure
Specified center hole or locating structure
C369S286000
Reexamination Certificate
active
06212159
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a laminated disc such as a DVD (Digital Video Disc) and a turntable on which laminated disc Is placed for reproduction of information.
2. Description of Prior Art
FIG. 20
is a cross-sectional view of a prior art turntable which is disclosed in Japanese Patent Preliminary Publication No. 8-7425. A turntable
102
has a hub
105
into which a motor shaft
104
is press-fitted or securely bonded to drive the turntable
102
in rotation. A disc
101
is placed on the turntable
102
and clamped by a clamper
103
so that the disc
101
is firmly held between the turntable
102
and the clamper
103
in a sandwiched relation. The hub
105
fits into a center hole
106
in the disc
101
with a very small clearance, thereby concentrically positioning the disc
101
with respect to the rotational axis of the motor shaft
104
. The disc
101
is rotated by a driving force of a spindle motor
100
.
FIG. 21
is a perspective view of a conventional disc
101
on which information is recorded. The disc
101
has a center hole
106
in its center and placed on the turntable
102
.
A DVD is a laminated disc which includes two discs bonded together back-to-back. When the two discs are bonded together, they are placed one over the other slightly eccentric due to alignment error. This alignment error varies within a predetermined tolerance and results in a small step in the wall of the center hole of the discs.
When a DVD is loaded onto the aforementioned conventional turntable, the stepped wall of the center hole of the disc may be caught by the hub
105
so that the disc
101
will not descend to the supporting surface of the turntable.
A DVD is usually loaded onto the positioning hub of the turntable so that the hub extends through the center hole with a very small clearance between the DVD. Burrs projecting from the the bonded interface of the disc into the center hole also cause a problem similar to that caused by the stepped wall or may present a problem that the disc is not concentric with the positioning hub. A further problem with the conventional disc is that the bonding agent spreads from between the two discs into the center hole during the manufacture of the disc or during operation of the turntable at elevated temperatures.
SUMMARY OF THE INVENTION
The present invention was made in view of the aforementioned problems.
An object of the invention is to provide a turntable which allows a disc to be smoothly loaded without burrs or a step in the wall of the center hole caught by the positioning hub.
Another object of the invention is to provide a laminated disc which can be loaded onto a turntable without the step and burrs of the wall of the center hole of the disc caught by the hub and can be adjusted to be concentric with the positioning hub upon loading.
Still another object of the invention is to provide a laminated disc which prevents the bonding agent from spreading into the center hole from the bonded interface when the disc is manufactured or operated at elevated temperatures.
A turntable is a table which is mounted to a shaft of a spindle motor and supports a laminated disc thereon so as to drive the disc in rotation. The laminated disc includes a lower disc and an upper disc bonded on the lower disc, and is supported on a disc-supporting surface of the turntable. When the disc is loaded on the turntable, a fitting member of the turntable fits into the center hole of the laminated disc for centering the laminated disc with respect to the shaft. The fitting member fits the center hole of the lower disc when the laminated disc is supported on the disc-supporting surface.
The turntable may include a tapered member in the form of a truncated circular cone which is continuous with the fitting member and guides a laminated disc to the disc-supporting surface. The tapered member has a surface at an angle (&thgr;) with the shaft of the spindle motor. The surface meets three conditions expressed by,
Condition I: tan &thgr;>
d
1/(
m
1−
m
2)
which defines a maximum center-to-center distance d1 between the disc and the shaft;
Condition II: tan &thgr;≧{(
n
1
−n
2)/
n
3}
which defines a lower limit of &thgr; so that the tapered member is prevented from interfering the laminated disc when the laminated disc is loaded onto the turntable; and
Condition III: tan &thgr;<1/&mgr;
which defines an upper limit of the angle (&thgr;) of the tapered member;
where
&thgr; is the angle (&thgr;) which the tapered surface of the tapered member makes with the shaft;
d1 is a center-to-center distance between the disc and the shaft;
m1 is a distance between the disc-supporting surface and an upper end of the tapered surface of the tapered member;
m2 is the distance between the disc-supporting surface and a lower end of the tapered surface of the tapered member;
n1 is a center-to-center distance between the upper and lower discs of the laminated disc;
n2 is a clearance between the laminated disc and the fitting member;
n3 is a difference between the distance m2 and a thickness of the lower disc; and
&mgr; is a coefficient of friction between the laminated disc
11
and a surface
15
a
of the tapered member.
The laminated disc includes lower and upper discs, each having an inner edge which defines the center hole of the disc. The corners of the edges are cut away along the circumference of the center hole. The upper and lower discs are placed together in such a way that the cut-away corners of the upper and lower discs face each other.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
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patent: 5728250 (1998-03-01), Kakinuma
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Ishida Yoshinobu
Kime Kenjiro
Mori Kazuo
Nagami Tetsuro
Nakatsu Kimihide
Klimowicz William
Mitsubishi Denki & Kabushiki Kaisha
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