Digital Equipment Corporation

Shyam C Parikh

Sigmund Hinlein

Charles M Riggle

Patrick L Hearn

Kenneth F Veseskis

A magnetic tachometer for generating a signal as a function of the velocity of a transducer positioning arm in a disk drive. The tachometer is formed by a pair of fixed parallel coils separated by a distance sufficient to allow a magnet, attached to a counterbalance portion of the rotary positioning arm, to move therebetween and thus to generate a voltage as a function of the velocity of the magnet. The coils are each wound over a thin armature member which is saturated by the magnet's magnetic field and they are differentially coupled to produce common mode rejection.

Magnetic tachometer for disk drives

A hub and spindle assembly for an interchangeable, removable disk of a disk drive. The spindle assembly includes means for driving the hub assembly, matingly attached and removably engaged thereto, so as to rotate the disk coupled to the hub. The hub assembly includes surfaces for engaging an accurately machined rotational surface of the spindle assembly and force engaging means for ensuring mating contact of the hub assembly surfaces with the spindle assembly and for ensuring removeable engagement. The hub and spindle assembly minimize runout such that the Read/Write heads track an essentially circular disk track, even if the disk is removed, reinserted or placed on a different spindle of the same type.

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Stow, MA, United States of America

Shyam C Parikh