Patent Application
20050229192
This application claims the priority of Korean Patent Application No. 2004-21571, filed on Mar. 30, 2004, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to an optical disc drive, and, more particularly, to a disc clamping apparatus to clamp a disc onto a turntable rotated by a spindle motor, as well as an optical disc drive adopting a disc clamping apparatus to clamp a disc onto a turntable rotated by a spindle motor.
2. Description of the Related Art
In general, an optical disc drive irradiates a beam onto a a recording medium, such as a compact disc (CD) and a digital versatile disc (DVD), so as to write information to or read information from the recording medium. The optical disc drive includes a disc clamping apparatus that clamps a disc onto a turntable.
Referring to
The optical disc drive further includes a clamping apparatus that clamps the disc D onto the turntable 40 to prevent the disc D from slipping from the turntable 40 when the turntable 40 is rotated. The clamping apparatus includes a clamper 80 on the upper case 70, the clamper 80 allowing the disc D to fixedly contact the upper surface of the turntable 40. A hollow portion 71 is formed to pass through a center portion of the upper case 70, and a supporter 72 is installed to protrude downward from the upper case 70 along an edge of the hollow portion 71. The clamper 80 is inserted into the hollow portion 71 while being supported by the supporter 72. An upper part of the hollow portion 71 is covered with a cover plate 73. A friction pad 41 that gives a friction force to the disc D is attached to the outer surface of the turntable 40. A magnet 42 is installed in the turntable 40, and a metal plate 82 is installed in the clamper 81 to correspond to the magnet 42.
While being placed on the tray 60, the disc D is inserted into the optical disk drive and placed on the turntable 40. When the turntable 40 is elevated, the clamper 80 puts pressure on the disc D in the vertical direction so that the disc D is clamped onto the turntable 40, due to a magnetic force formed between the magnet 42 in the turntable 40 and the metal plate 81 in the clamper 80.
However, a conventional disc clamping apparatus such as that of
The present invention provides a disc clamping apparatus with a simple structure, in which a disc is clamped onto a turntable using a centrifugal force caused by rotation of the turntable, and an optical disc drive adopting a disc clamping apparatus with a simple structure, in which a disc is clamped onto a turntable using a centrifugal force caused by rotation of the turntable.
According to one aspect of the present invention, a disc clamping apparatus to clamp a disc onto a turntable rotated by a spindle motor in an optical disc drive comprises a plurality of grooves formed along an outer circumference of a hub provided on a center portion of the turntable; a plurality of balls inserted into the plurality of grooves to move toward outsides of the grooves due to a centrifugal force caused by rotation of turntable so as to pressurize the disc; and a cover member combined with an upper part of the hub to prevent the balls from being separated from the grooves.
In addition, the disc clamping apparatus may further comprise a friction pad attached to an outer upper surface of the turntable to provide a friction force to the disc. At least three grooves are formed along an outer circumference of the hub at equal intervals. The cover member may be configured to cover upper parts of the grooves so as to make that mouths of the grooves be smaller than diameters of the balls. Bottom surfaces of the grooves may be inclined downward toward a center portion of the hub or have flat planes. When the bottom surfaces have flat planes, an outer circumference of the cover member may be inclined downward. The cover member may be adhered to an upper part of the hub via an adhesive or combined with the upper part of the hub via a screw.
According to another aspect of the present invention, an optical disc drive includes a spindle motor that rotates a disc, a turntable combined with a rotation axis of the spindle motor, an optical pickup that irritates a beam on a recording surface of the disc to record information on or reproduce information from the disc, and a disc clamping apparatus that clamps the disc onto the turntable. According to this aspect of the invention, the disc clamping apparatus comprises a plurality of grooves formed in an outer circumference of a hub provided on a center portion of the turntable; a plurality of balls inserted into the plurality of grooves, to move toward outsides of the grooves due to a centrifugal force caused by rotation of the turntable so as to pressurize the disc; and a cover member combined with an upper part of the hub to prevent the balls from being separated from the grooves.
Additional and/or other aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
These and/or other aspects and advantages of the invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures.
Referring to
As illustrated in
The hub 142 protrudes to a predetermined height from a center portion of the turntable 140. The grooves 181 are formed in the hub 142 along the outer circumference of the hub 142. At least three grooves 181 are formed at substantially equal intervals. The grooves 181 are opened toward the upper surface and outer circumference surface of the hub 142. As shown in
When the turntable 140 is rotated, the balls 182 inserted into the respective grooves 181, are forced to move toward the outside of the grooves 181 due to a centrifugal force caused by the rotation of the turntable 140. The movement of the balls 182 applies pressure in a downward direction onto the disc D placed on the turntable 140 so that the disc D is clamped onto the turntable 140. An effect caused by the movement of the balls 182 will be later described in detail.
The centrifugal force operating on the balls 182 may be expressed with a formula mrw2. In this formula, m denotes the mass of an individual ball 182, r denotes the radius of gyration, i.e., the distance between the center of gyration and the center of mass of the ball 182, and w denotes an angular rate of rotation of the ball 182 that is rotated together with the turntable 140 and the hub 142. Accordingly, the centrifugal force operating on the ball 182 is proportional to the mass m, the radius r of gyration, and a square of the rotation angular rate w. In this embodiment, since the external diameter of the hub 142 has been determined, the radius r of gyration is limited. Also, the rotation angular rate w is determined by a speed factor of the disc drive.
Therefore, arbitrarily increasing the centrifugal force operating on the balls 182 is impossible without speeding up the rotation of the turntable. As a result, in order to increase the centrifugal force operating on the balls 182, the mass of the ball 182 is the relatively easiest factor to.
In an embodiment of the invention, one way to increase the mass of the ball 182 is to use a high-density metal material, such as steel, or, more preferably, stainless steel to form the ball 182. Stainless steel is advantageous because stainless steel has relatively excellent anticorrosive properties.
The cover member 183 is coupled to the upper portion of the hub 142. Specifically, the cover member 183 may be adhered to the upper portion of the hub 142 via a predetermined adhesive, e.g., a double faced tape 184. The cover member 183 allows the balls 182 from being separated from the grooves 181. In detail, the cover member 183 is configured to cover tops of the grooves 181 to cause the mouths of the grooves 181 to be smaller than the diameters of the balls 182.
Further, the grooves 181 may be inclined such that their bottom surfaces 181a become low toward a center portion of the hub 142. The shapes of the bottom surfaces 181a of the grooves 181 provide spaces in which the balls 182 may move without contacting the cover member 183. Accordingly, when a centrifugal force is caused by the rotation of the turntable 140, the balls 182 may be moved toward the outside of the grooves 181 without any interference.
In this embodiment, the disc clamping apparatus further includes a friction pad 141 that is attached to the exterior upper part of the turntable 140 to provide a friction force to the disc D. Installation of the friction pad 141 prevents the disc D from slipping from the turntable 140 when the turntable 140 is rotated at a low speed.
An operation of the disc clamping apparatus 180 of
Next, as shown in
While the balls 182 contact the disc D, the centrifugal force operating on the balls 182 is weak and a pressurization force given to the disc D by the balls 182 is also weak when the turntable is rotated at a low speed. In this case, the friction force given by the friction pad 141 is applied to the disc D. However, since the disc D is rotated at a low speed the friction force is able to prevent the disc D from slipping from the turntable 140.
If a rotation speed of the turntable 140 reaches a rated rotation speed, the centrifugal force operating on the balls 182 increases so as to increase the pressurization force applied to the disc D by the balls 182. Accordingly, the disc D is fast fixed onto the turntable 140. In general, a force of about 100 gw is known to be required to stably clamp the disc D with the turntable 140 when the disc D is rotated at a 1× speed. An experiment revealed that installation of a disc clamping apparatus according to the present invention into an optical disc drive applied a force of about 200 gw to the disc D. If the disc D is rotated at a high speed, e.g., at a 50× speed, a centrifugal force operating on the balls 182 is further increased and as a result, a force clamping the disc D onto the turntable 140 is intensified accordingly. Naturally, therefore stably clamping the disc D onto the turntable 140 even when the disc D is rotated at a high speed is possible as a result of this invention.
As is described above, the disc clamping apparatus according to this embodiment allows the disc D to be clamped onto the turntable 140 using a centrifugal force caused by the rotation of the turntable 140. Therefore, the disc clamping apparatus according to this embodiment includes a simpler structure than a conventional disc clamping apparatus. In particular, as shown in
Referring to
Alternatively, the cover member 183 may be combined with the hub 142 via a device, e.g., a hook, other than the screw 284 or the adhesive.
Referring to
The structure of the cover member 383 provides a space in which the ball 182 may move within the grooves 381 without contacting the cover member 383. Also, since the mouth of the grooves 381 are smaller than the diameter of the ball 182, preventing the ball 182 from being separated from the groove 381 is possible.
As is described above, a disc clamping apparatus according to the present invention is advantageous in that the disc clamping apparatus clamps a disc onto a turntable using a centrifugal force that is caused by rotation of the turntable. Thus, the disc clamping apparatus has a simpler structure than a conventional disc clamping apparatus. Further, manufacturing and management costs of the disc clamping apparatus may be reduced.
Also, an optical disc drive adopting the disc clamping apparatus according to the present invention does not require formation of a hollow portion and a supporter in an upper case. Thus, a process of manufacturing the upper case and maintaining the strength of the upper case is simplified.
Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-21571 | Mar 2004 | KR | national |
