Bulk eraser including at least three magnets configured for erasing recorded information

A bulk eraser for erasing recorded information on a magnetic-recording disk in a hard-disk drive, said bulk eraser comprising:

• a first magnet disposed opposite a second magnet across a first portion of a gap, said first magnet having a first end pole disposed proximate said first portion of said gap and a first pole-tip portion disposed proximate a second portion of said gap, and said second magnet having a second end pole disposed proximate said first portion of said gap and a second pole-tip portion disposed proximate said second portion of said gap, wherein said first and second end poles have a same polarity;
• a first magnetic shield disposed on said first end pole in proximity to said first portion of said gap;
• a second magnetic shield disposed on said second end pole in proximity to said first portion of said gap;
• a third magnet disposed proximate to a second portion of said gap, said third magnet having a third end pole disposed proximate said second portion of said gap, wherein said third end pole has a polarity opposite to said first and second end poles;
• and
• a pole piece disposed on said third end pole in proximity to said second portion of said gap, said pole piece having a third pole-tip portion;
• wherein said first pole-tip portion, said second pole-tip portion, and said third pole-tip portion define a second portion of said gap located between said first pole-tip portion, said second pole-tip portion, and said third pole-tip portion and are configured such that magnetic-flux density in said second portion of said gap lies substantially parallel to a plane of said magnetic-recording disk in a disk-stack of said hard-disk drive to erase recorded information from a portion on said magnetic-recording disk when said hard-disk drive is inserted into said second portion of said gap.

A bulk eraser for erasing recorded information on a magnetic-recording disk in a hard-disk drive, said bulk eraser comprising:

• a first magnet having a first end pole and a first pole-tip portion and a second magnet having a second end pole and a second pole-tip portion, said first and second magnets disposed on opposite sides of a first portion of a gap, wherein said first end pole and said second end pole have a same polarity;
• a third magnet having a third end pole of opposite polarity to said first end pole and said second end pole, and having a pole piece with a third pole-tip portion, wherein said first pole-tip portion, said second pole-tip portion, and said third pole-tip portion define a second portion of said gap located between said first pole-tip portion, said second pole-tip portion, and said third pole-tip portion;
• and
• a structure comprising:
• a yoke having a first yoke portion and a second yoke portion;
• said first yoke portion magnetically coupled with said first magnet, said third magnet and said pole piece wherein said first yoke portion further comprises:
• a first plurality of magnets disposed in and magnetically coupled with said first yoke portion with a polarity assisting magnetic-flux circulation in a first magnetic circuit comprising said first magnet, said third magnet, said pole piece, said second portion of said gap and said first yoke portion including said first plurality of magnets;
• and
• said second yoke portion magnetically coupled with said second magnet said third magnet and said pole piece wherein said second yoke portion further comprises:
• a second plurality of magnets disposed in and magnetically coupled with said second yoke portion with a polarity assisting magnetic-flux circulation in a second magnetic circuit comprising said second magnet, said third magnet, said pole piece, said second portion of said gap and said second yoke portion including said second plurality of magnets;
• wherein said structure is configured to suppress stray magnetic flux and to increase magnetic-flux density in said second portion of said gap for erasing recorded information from a portion on said magnetic-recording disk when said hard-disk drive is inserted intosaid second portion of said gap.