ERASING HEAD DEVICE

摘要

PURPOSE:To eliminate an erasure current generating circuit section by rotating and driving a rotating shaft of a rotating plate with a rotating member connected to a drive shaft of a plunger to bring a permanent magnet erase head into press contact with or to detach from a magnetic tape face thereby eliminating the need for erasure current at video recording. CONSTITUTION:The torque required for press contact/detachment of the permanent magnet erasing head 20 to/from the tape face is given to a rotary shaft 22 of the rotating plate 21 via a wire rope 28 connected to the drive shaft 29 of a plunger 30. The permanent magnet erasing head 20 forms N and S poles of poly-pole alternating magnetic field with attenuation on a tape sliding face in the running direction 91 of a tape 90. Noise and distortion due to erasure are reduced by increasing the number of poles in a limited head length; the number of alternating poles is 11 in figures (a) and (b). The width (d) of the magnetic pole of the 1st N pole (90-1) and the first S pole (90-2) among the many alternating magnetic poles is taken broader in comparison with the other magnetic pole widths and this is because the rate of erasure is attained surely in response especially to a high coercive force recording medium.