| 摘要 |
An energy efficient means for selectively pre-magnetizing a magnetic recording medium of a thermoremanent magnetographic printer is disclosed. It consists of a pair of axially aligned, elongated two-pole, substantially cylindrical permanent magnets separated by a narrow gap and oriented so that like poles of adjacent magnets confront one another across the gap. The recording medium moves between the magnets in a direction perpendicular to the magnets. The elongated magnets produce magnetic field components that are additive in the surface of the recording medium and that cancel in the direction normal to the recording medium's surface. The magnetizing field of the magnets may be turned off for latent image retention by rotating the magnets about 90 degrees. An alternate embodiment houses the magnets in a pair of fixed high permeability pole pieces which confront each other across a gap and act as high permeance conduits for the magnetic flux to create a strong pre-magnetizing field in the surface of the recording medium as it passes therethrough. Rotation of the magnets shunts the flux effectively eliminating any magnetic field from the region of the recording medium.
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