Cassette-type head demagnetizer

Abstract

A cassette-type demagnetizer for magnetic heads of tape-recording and/or playback units has a housing provided with an open side which is juxtaposed with a magnetic head of a unit when the demagnetizer has placed onto the latter. A rotatable tape supply hub and a rotatable tape take-up hub are located in the housing and can be driven by drive spindles of the unit. A tape is convoluted onto the supply hub and is withdrawn from the same and convoluted onto the take-up hub when the latter is rotated. A circular permanent magnet is rotatably mounted in the housing adjacent the open side of the latter and the tape is trained about it in order to rotate the magnet as the tape travels, so that an alternating magnetic field is produced which demagnetizes the head of the unit. A shielding arm of soft iron is pivotably mounted in the housing and is urged into engagement with the periphery of the take-up hub by a biasing spring. The arm has an end portion which progressively moves between the circular permanent magnet and the open side of the housing, in order to progressively reduce the magnetic field to zero, as the amount of tape on the take-up hub increases and the diameter of the hub and tape package thereon therefore also increases and urges the arm in direction opposite to the biasing force of the spring.