Power loss actuated magnetic latch system for head-arm assembly

A system for latching and unlatching a head-arm of a disk drive comprising:

• a locking arm assembly including an elongated arm member, a first latching element and a first component of a magnetic latch actuator, said first latching element and said first component being mounted on said arm member at spaced apart first and second locations, said arm assembly having a center of gravity positioned essentially at a third location on said arm member spaced from and located between said first and second locations;
• a pivot support pivotally mounting said arm assembly for swinging about an axis extending through said third location to move the first latching element between spaced apart latching and unlatching positions;
• a head-arm mounted second latching element, said latching elements being cooperable to prevent movement of a head-arm from a safe parked position when the first latching element is in its latching position;
• a second component of a magnetic latch actuator, the components of said actuator being cooperable to swing said arm assembly on said pivot support about said axis to thereby move the first latching element between its said positions;
• one of said first and second components comprising a coil electrically connected so as to have selectable alternative first and second energized states,
• another of said first and second components comprising a permanent magnet,
• said coil and said permanent magnet being positioned and arranged so as to impose a substantially pure torque couple on said locking arm assembly at a location thereon remote from said axis,
• said torque couple being imposed in a first direction to torque said first latching element to its latching position when said coil is in its first energized state, and in an opposite direction to torque said first latching element to its unlatching position when said coil is in its second energized state;
• a latch controller operable to selectively energize said coil in either said first state or said second state;
• a power sensor for sensing an absence of power supply to a disk drive;
• and
• a power storage and supply source coupled to said power sensor to supply an electrical energization current to said coil via said latch controller to energize the coil in said first energized state when the power sensor senses said absence of power supply.