Linear stepper motor drive with a read/write head in a floppy disc system

Claim 1

A drive for a magnetic data storage disc comprising: a rotary drive means for rotating a magnetic data storage disc; a read/write head for reading or writing data on the disc; and linear drive means for linearly moving said head along a radial path across said disc, said linear drive means comprising a linear stepper motor of the variable reluctance type including: a stationary magnetic structure; a sliding magnetic structure; and bearing means for supporting said sliding structure on said stationary structure; said stationary structure including a plurality of pole positions having windings associated therewith and adapted to be energized in various phases so as to produce linear motion of said slider through a plurality of magnetically inherent step positions; said sliding structure comprising magnetic material having a plurality of magnetic discontinuities therein, the overall length of said plurality of discontinuities along said structure being longer than said stationary magnetic structure; said sliding structure and said stationary structure further forming a pair of bearing raceways, each of said raceways having closed ends and being centrally located on a pair of opposite sides of said sliding structure; said bearing means being confined in said pair of raceways, each of said pair of raceways being formed by juxtaposed grooves on adjoining faces of said sliding structure and said stationary structure, each of said grooves including a pair of raised surfaces extending in the direction of linear motion of said sliding member, wherein said bearing means comprises balls riding on the two pairs of raised surfaces in each of said raceways; said stationary structure including means for adjusting the friction on said ball bearings in said raceways.