Patent ID: 6252842
Filing Date: 2001-06-26
Classification: G11B

Abstract:
In combination, a recording disc and a disc recording and reproducing apparatus for recording signals on the disc and reproducing signals from the disc, comprising:a disc chucking device which includes a motor driven spindle, a disc setting member mounted for rotation with the spindle for supporting the disc when the disc is chucked by the disc chucking device, and a resiliently biased, conically shaped centering member mounted coaxially on the spindle with the disc setting member for reciprocal movement along the length of the spindle;a disc substrate having a recording surface and a center hole which has a diameter smaller than a base diameter of the conically shaped centering member;a magnetic member positioned in register with the center hole in a recessed portion in the upper surface of the disc substrate so that the magnetic member substantially closes the center hole and an upper surface of the magnetic member is substantially flush with the upper surface of the disc substrate;a cartridge for containing the disc substrate, the cartridge having access holes for one or more recording heads and the disc chucking device; andwherein the disc further includes an annular rib which depends from a lower surface of the disc substrate toward the disc chucking device for seating on the disc setting member and which enlarges the thickness of the disc substrate, in the direction of the axis of rotation of the spindle, around the periphery of the center hole, and wherein the thickness of the annular rib, in the direction of the axis of rotation of the spindle, is sufficient that when the disc substrate is supported by the annular rib on the disc setting member no part of the disc chucking device extends through the center hole of the disc substrate to project above an upper surface of the disc substrate which is parallel to the lower surface of the disc substrate; andwherein the disc chucking device further comprises a magnet mounted on the spindle, radially inwardly of the centering member for magnetically attracting the magnetic member.