Dynamic magnetic information storage or retrieval – Record medium – Disk
Reexamination Certificate
2002-01-22
2004-10-19
Ometz, David (Department: 2653)
Dynamic magnetic information storage or retrieval
Record medium
Disk
Reexamination Certificate
active
06807028
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a center core of a magnetic disc that is fixed to the central portion of a flexible magnetic recording media housed within a magnetic disc cartridge, particularly those of high capacity.
BACKGROUND ART
Conventionally, magnetic disc cartridges of a construction in which a magnetic disc, formed by magnetic layers being formed on both sides of a flexible polyester sheet or the like and having a metallic center core fixed to the central portion of said flexible magnetic recording media are being utilized mainly as recording media for computers. These so-called floppy disks are rotatively driven and magnetic recording is performed on the aforementioned magnetic layers by a magnetic head. These floppy disks have the advantages of being easy to handle, and low cost.
The aforementioned center core supports the magnetic recording media and defines its center of rotation. The center core also serves the function of transmitting the rotational driving force imparted thereon by a chucking portion provided on the tip of a rotation spindle of a drive side rotational drive means, by which it is held. Normally, the aforementioned center core comprises a discoid standardizing surface portion formed in the central portion thereof that abuts the tip portion of the aforementioned spindle to perform standardizing positioning, and a flanged collar portion formed parallel to the standardizing surface portion at the outer periphery thereof that is fixed to the central portion of the magnetic recording media.
The standardizing surface portion is provided with a central aperture into which the central pin of the spindle is inserted. At the same time, a drive pin of the spindle is engaged with a drive aperture which is provided towards the outside from the aforementioned central aperture, and the center core is to be rotationally driven thereby. Further, a magnet is provided at the tip of the spindle that provides a magnetic attraction force to magnetically attract the center core to supplement maintenance of the chucking state.
With regard to magnetic recording media such as that of the magnetic disc described above, as the recording capacity increases, it becomes necessary to rotate the magnetic disc at high speed in order to secure a transfer rate thereof. In addition, the expected recordation/reproduction performance is secured by the strict maintenance of appropriate relative positioning between the magnetic recording media that rotates at high speed and the magnetic head that performs recordation/reproduction.
It has been proposed to increase the magnetic attraction of the center core to the magnet of the aforementioned spindle in order to stably rotate the magnetic disc at high speed. However, it is difficult from a manufacturing standpoint to accurately form the surface of the magnet at a predetermined height. Also, the accuracy in height becomes unstable if the center core and the magnet are magnetically attached in a state of contact. Therefore, to approach the bottom surface of the center core towards the magnet with a predetermined distance therebetween and attracting the center core in this manner is being considered.
However, if the magnetic attraction force is strengthened towards conventional magnetic discs having a lower recording capacity as well, there is a fear that chucking malfunctions will occur. Therefore, for center cores magnetic discs that have high recording capacities, it has been proposed to form the portion of the bottom surface that faces the magnet of the spindle lower than the central standardizing surface portion thereof to approach the surface of the magnet.
That is, a center core formed in this manner comprises a central standardizing surface portion that abuts the tip surface of a spindle to perform standard positioning; an attraction surface portion formed parallel to and of a different height than the standardizing surface around the outer periphery thereof via a step portion that faces the magnet of the spindle; and a collar portion formed around the outer periphery thereof parallel to the aforementioned standardizing surface portion that is fixed to the magnetic recording media.
In addition, a center core formed in this manner comprises a collar portion of the outer periphery thereof, a standardizing surface portion towards the center thereof, an attraction surface portion around the outer periphery of the standardizing surface portion, and a connection portion that connects the attraction surface portion with the collar portion.
However, as a center core as described above is formed with an attraction surface between a standardizing surface portion and a collar portion of a different height therefrom, multiple drawing processes are required in the manufacture thereof. This causes difficulties in securing manufacturing accuracy with regard to the height positioning accuracy of the standardizing surface portion and the collar portion as well as the degree of parallelism therebetween. This in turn causes problems in securing positional accuracy between the magnetic recording media and the magnetic head.
Particularly in the case that the step between the aforementioned attraction surface and the standardizing surface is on the order of a board thickness, there is a propensity for the manufacturing accuracy to be difficult to obtain with regard to a drawing process. A higher degree of parallelism is required, as there is a fear that vertical movement of the magnetic recording media will be generated along with the rotation of the aforementioned magnetic disc.
The present invention has been developed in view of the circumstances described above, and it is a first object of the present invention to provide a center core for a magnetic disc that enables stable high speed rotation of a magnetic recording media, said center core being provided with a stepped formed portion between the standardizing surface portion and the attraction surface, formed by multiple drawing processes, wherein manufacturing accuracy is obtained, and parallelism between the standardizing surface portion and the collar portion, as well as dimensional accuracies thereof are secured.
It is a second object of the present invention to provide a center core for a magnetic disc that enables stable high speed rotation of a magnetic recording media, said center core having improved dimensional accuracies of the standardizing surface portion and the attraction surface, as well as securing parallelism between the standardizing surface portion and the collar portion, as well as dimensional accuracies thereof.
By the attraction surface being formed lower than the standardizing surface portion in a center core as described above, during a state in which a magnetic disc is housed within a case, the aforementioned attraction surface portion protrudes from the hub aperture of said case. This causes a fear that if said case is dropped or the like, the impact will act directly thereon and damage the magnetic recording media.
That is, when the magnetic disc cartridge is in a horizontal state, the standardizing surface portion as well as the attraction surface portion of the aforementioned center core protrudes from the bottom surface of the case. At a time when the disc is dropped or the like, the attraction surface portion of the center core collides with an external member such as a floor, the impact is transmitted directly to the magnetic recording media, and the magnetic recording media suffers damage by colliding with the internal surface of the case. Particularly in a case that the impact on the aforementioned attraction surface portion acts thereon in an oblique manner and the magnetic recording media collides with the internal surface of the case in an oblique manner, the magnetic recording media is more likely to be damaged.
The present invention has been developed in view of the above described circumstances, and it is a third object of the present invention to provide a center core for a magnetic disc that prevents damage to the magnetic recording media b
Ometz David
Sughrue & Mion, PLLC
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