Symmetrical coil actuator for a magnetic disk drive

Claim 1

A magnetic disk drive actuator for moving a magnetic head in an arcuate path in read/write relationship with a magnetic disk comprising: an actuator arm rotatable about a center of rotation: a read/write head mounted on said arm so that said head travels along said arcuate path as said arm is rotated; a planar coil having only two active sections connected in series and attached to said arm for rotating it about said center of rotation, said planar coil being symmetrical with respect to said center of rotation and having first and second substantially straight active sections extending from one side of said center of rotation and third and fourth substantially straight active sections extending in the same plane on the opposite side of said center of rotation, and symmetrical with said first and second sections having arcuate return traces joining said first and second straight active sections and arcuate return traces joining said third and fourth straight active sections, said active sections and said return traces being connected in series to two connections for supplying current to said coil; and magnetic means positioned adjacent to each of said active sections of said coil, so that current through said active sections on opposite sides of said center of rotation produces magnetic forces on said coil which act about said center of rotation whereby the rotational forces about the center of rotation are cumulative and the torsional forces cancelled one another avoiding vibration and reducing potential servo loop instability.