Disc player having self-actuated magnetic clamping device

Abstract

A magnetic clamping device for a disc player inherently moves to and is levitated in a resting position when the player housing and spindle are oriented for disc insertion, and moves to and is sustained in a clamping position when the player and housing are oriented for disc playing. The magnetic clamping device changes its position during a time when the centering hub of a spindle engages with the central aperture of the disc, so that the clamping device is always in its resting position when a disc is inserted or ejected, thereby eliminating scratching of the critical surfaces of the disc by the adjacent surface or edge of the magnetic clamping device. Preferably the magnetic clamping device has an annular permanent magnet with multiple pairs of poles disposed about the circumference of the annulus. A flux shorting washer of magnetically permeable material is secured to the top of the annulus so that the magnetic flux from the permanent magnet is emitted from the bottom of the annulus. The clamping device is levitated above the spindle and inserted disc by a levitating ring of permeable material affixed flush with the lower surface of the upper part of the disc player housing. Depending on the distance of the levitated clamping device from a disc driving plate of permeable material included in the spindle, the magnetic flux emitted from the bottom of the clamping magnet is preferably linked to the levitating ring for levitation or the disc driving plate for disc clamping. Thus the magnetic clamping device quickly switches between its resting position and its clamping position at the proper time in the disc insertion or ejection cycle.