Patent ID: 7921438

Claim:
A chucking mechanism operable to detachably set thereon a discoid disk including a central opening portion, the chucking mechanism comprising: a center case arranged concentrically with a predetermined central axis, including a cylindrical portion which fits the central opening portion, a top plate covering an axially upper side of the cylindrical portion, and a plurality of openings arranged in a circumferential direction extending from the cylindrical portion to an outer circumferential side of the top plate portion; a claw member movable with respect to the opening, protruding in a radially outward direction from the cylindrical portion, and making contact with the central opening portion of the disk; a coil spring providing radial force to the claw member; and a turn table including a disk setting surface setting thereon the disk, wherein a tip portion arranged at a radially outmost portion of the claw member continues to move in an axially downward direction and a radially inward direction until the disk is set on the disk setting surface, wherein the claw member has a cross-section running through the central axis and a midpoint of a circumferential width of the tip portion, wherein the claw member has a protrusion extending radially inward, wherein the protrusion has a first surface which fits one end of the coil spring, the first surface having an upper protrusion inclined surface part and a lower protrusion inclined surface part, wherein a first line extended from the upper protrusion inclined surface part has a first angle with respect to the central axis in the cross-section, wherein a second line extended from the lower protrusion inclined surface part has a second angle with respect to the central axis in the cross-section, wherein the first angle is smaller than the second angle when the discoid disk is detached from the chucking mechanism, so as not to force the coil spring to be pressed in the axial direction when the tip portion moves in the axially downward direction.