Browse Prior Art Database

Bulk Eraser

IP.com Disclosure Number: IPCOM000083507D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 71K

Publishing Venue

IBM

Related People

Bate, G: AUTHOR [+3]

Abstract

Permanent magnets erase magnetically recorded patterns on magnetic media uniformly without external power sources.

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Bulk Eraser

Permanent magnets erase magnetically recorded patterns on magnetic media uniformly without external power sources.

Plastic strip magnets consisting of small single-domain particles of barium ferrite in a rubbery binder are arranged to form a shallow wedge. In Fig. 1, the magnetization in one magnet opposes the magnetization in the other magnet, because of their relative pole orientations. The magnetic flux lines connect adjacent poles on the same strip magnets.

In Fig. 2, the poles are arranged so that the flux lines cross through the medium between the magnetic strips. When the magnetic medium passes between the magnets from the narrow to the wide side of the wedge, the medium is subject to a sequence of alternating and diminishing fields which leave the medium in a neutral magnetic state regardless of its original magnetization.

A practical bulk eraser is shown in Fig. 3. Magnetic tape enters the wedge under an incoming guide roll and leaves over an outgoing guide roll. Both the narrow and wide wedge dimensions are adjustable by turning appropriate take- up screws. For a six-inch web of on the order of 20 to 30 mils thick medium, the wedge entry is about 1/32 inch and exit is about 1/2 inch.

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