Disc player having self-actuated magnetic clamping device

US4570194A · kind A · utility

Assignee

• Staar S.A. · BE

Inventor

• Etienne A. M. Schatteman · Wemmel, BE

Key dates

• Filing date: Jan 12, 1983
• Grant date: Feb 11, 1986
• Expiry date: Jan 12, 2003

Classification

• Technology area (CPC G): Physics
• CPC primary: G11B17/0284
• WIPO field: Audio-visual technology
• WIPO sector: Electrical engineering

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. De…