Head carriage moving mechanism of disk recording reproducing device

Claim 1

A head carriage moving mechanism for a disk recording/reproducing device of the type having a read/write magnetic head mounted on a carriage which is movable along an axial direction, an engaging element fixed to the carriage, a screw shaft having a spiral groove in which the engaging element is engaged for incrementally moving the carriage in the axial direction upon rotation of the screw shaft by a stepping motor, wherein the improvement comprises: said spiral groove of said screw shaft being formed with successive linear groove portions which are offset circumferentially at equal angular spacings around the outer periphery of said screw shaft, which have a zero degree angle of lead, and which are offset incrementally in the axial direction; said screw shaft being rotated in unison with a rotor of said stepping motor composed of a permanent magnet having a plurality of magnetic poles which are arranged corresponding to the circumferential angular spacings of said groove portions; and said screw shaft having formed thereon a portion having a polygonal prism shape wherein the planar faces thereof are distributed circumferentially around said screw shaft in correspondence to the angular spacings of said groove portions and said magnetic poles.