Disc chucking mechanism

Details Disc chucking mechanism Disc chucking mechanism

1999-03-18

2001-04-24

Klimowicz, William (Department: 2652)

Dynamic information storage or retrieval

Dynamic mechanism subsystem

Specific detail of storage medium support or motion production

Reexamination Certificate

active

06222818

ABSTRACT:

BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to a disc chucking mechanism which rotates, together with a turn table, a recording medium disc, such an optical disc or a magneto-optical disc, to be disposed on the turn table, to write information into the recording medium disc and read it from the same. More particularly, the invention relates to a disc chucking mechanism for positioning a disc with a magnetic center hub and holding the same.
2. Related Art
In a disc drive which writes information signals into a recording medium disc, such an optical disc or a magneto-optical disc, or reproducing stored information from the same, while rotating the recording medium disc, the disc must be rotated in a state that an optical pickup device faces a recording track on the disc. Therefore, the disc drive is provided with a disc chucking mechanism including a turn table. A rotation/drive mechanism drives and rotates the turn table, together with a disc being put on the turn table at a predetermined location. Examples, of the conventional disc chucking mechanism is U.S. Pat. No. 5,303,098.
In order to reduce the size and thickness of the disc driver, the technique of the publication eliminates the use of a chucking plate, which presses the disc against the turn table from its reverse side by removing a movement of the disc in the directions of the revolution axis of the disc. To this end, the disclosed technique includes a turn table which is driven to rotate and on which a disc with a center hole in to be located thereon, a fitting member to be fit into the center hole of the disc, and a plurality of spherical members being retractably provided in the fitting member while being urged and protruded outwardly of the fitting member by an elastic member, the spherical members supporting the disc on the turn table by pressing the disc against the turn table. When the disc is put on the turn table, those spherical members, which are urged and protruded out of the fitting member, are brought into contact with the upper edge of the center hole of the disc. Accordingly, in this state, the disc in supported on the turn table while being pressed against the turn table, viz., the disc is attached to the turn table.
In the conventional chucking mechanism disclosed in the above publication, the disc never moves in the directions parallel to the axis of revolution of the disc when the disc is chucked, and it is not required to use the chucking plate which presses the disc against the turn table from its reverse side. Therefore, the aim of achieving the size reduction and the thinning of the disc driver is successfully achieved.
In the above-mentioned disc chucking mechanism, to attach the disc to the turn table, the plurality of spherical members are urged and brought into contact with the upper edge of the center hole of the disc, to thereby press a disc against the turn table. The disc is centered at a position where the urging forces of the spherical members are balanced. Therefore, if the balancing-state of those urging forces is lost, the centering position will be shifted from the correct one. Particularly when the spherical members are independently urged, the urging forces of those members are likely to be not uniform. In this case, the centering position will be greatly shifted.
The disc chucking mechanism uses a ring formed with an elastic member made of rubber, for example, for the urging means.
Therefore, the urging forces of the spherical members are relatively uniform. Those members for centering the disc are the spherical members protruded outwardly of the fitting member, and a fixed reference point for positioning them is not present. For this reason, the disc being chucked is movable in the directions parallel to the plane of the disc per se, resulting in a play of the disc. Many factors to decenter the disc exists variations of the composition and the size of the elastic ring, nonuniformity of the forces externally applied when the disc is attached, and others. In this respect, some improvement is required for the disc chucking mechanism.
Additionally, the conventional disc chucking mechanism is complicated in structure, and high in parts working and assembling cost.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a disc chucking mechanism which is substantially immovable in the directions parallel to the plane of the disc per se, and is free from a play of the disc and makes it difficult to decenter the disc. Another object of the present invention is to provide a disc chucking mechanism which is simple in construction, and low in parts working and assembling cost.
According to an aspect of the present invention, there is provided a disc chucking mechanism comprising:
a turn table, on which a disc with a center hole is disposed, driven by a rotation driving means, said turn table including:
a cylindrical portion to which the center hole of a disc is fit,
a first guide protrude radially outwardly of an outer circumferential surface of said cylindrical portion,
second and third guides retractably provided at positions angularly spaced approximately 120° from said first guide with respect to the center of rotation of said cylindrical portion, and
auxiliary guides provided at mid-positions between said second guide and said first guide and between said third guide and said first guide, a height of a peak point of each said auxiliary guide being smaller than a height of a peak point of said first guide when measured from the outer circumferential surface of said cylindrical portion,
wherein the distance of each said auxiliary guide measured from the outer circumference surface of said cylindrical portion in smaller than the distance of the peak point of said first guide from the outer.
As seen from the foregoing description, the turn table includes a cylindrical portion to which the center hole of a disc is fit, a first guide protrude radially outwardly of the outer circumferential surface of the cylindrical portion, and second and third guides retractably provided at positions angularly spaced approximately 120° from the first guide with respect to the center of rotation of the cylindrical portion. Therefore, the first guide constituting one of three points used for centering the disc is integral with the cylindrical portion of the turn table and fixed relative to the cylindrical portion
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per se. Thus, one of the centering points in fixed, and hence the centering reference is surely and definitely determined when comparing with the conventional case where all the disc centering points are retractable in the radial direction. In this respect, the disc chucking mechanism can center the disc with high precision.
Auxiliary guides are provided at lid-positions between the second guide-and the first guide and between the third guide and the first guide. When in a state of the disc being chucked, some cause or causes shifts the disc from its proper position on the cylindrical portion of the turn table, the auxiliary guides support the disc centering operation. Further, the distance of each auxiliary guide measured from the outer circumference surface of the cylindrical portion is smaller than the distance of the peak point of the first guide from the outer circumferential surface of the cylindrical portion. Therefore, when some cause shifts the disc from its correct position on the cylindrical surface of the turn table, the circumferential edge of the center hole immediately comes in contact with the auxiliary guide to be prohibited from its relative movement, and as a result, the position shift of the disc is limited within a small range.
The second and third guides are integrally formed-by use of a single metal sheet, and retractably movable in the radial direction of the turn table by the utilization of an elastic force of the metal sheet. With this technical feature, the urging forces of those guides may readily be uniformized, and the centering accuracy of the disc when it is chucked is improved. Further, there

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