Importance

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Abstract

A recording disc for use with a disc recording and reproducing apparatus of the type having a disc chucking device which includes a spring biased, conically shaped centering member mounted coaxially on a drive spindle, wherein the disc includes a disc substrate contained in a cartridge and having a center hole which has a diameter smaller than a base diameter of the conically shaped centering member, an annular rib which depends from a lower surface of the disc substrate toward the disc chucking device for seating on a 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 so that the centering member can have a steeper slope compared to prior art centering members, and thereby provide more effective centering action, and yet 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 above its upper surface.

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First Claim