GB769727A - Magnetic tape erasing apparatus - Google Patents

Abstract

769,727. Magnetic recording erasing apparatus. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 23, 1954 [Dec. 31, 1953], No. 37168/54. Class 40 (2). Apparatus for establishing a uniform unsaturated magnetic condition on a magnetic tape 3, e.g. for use in a binary recording system, includes an erasing head 7 comprising a threebranch single magnetic core assembly having two non-magnetic gaps 11, 12 of unequal length, and means for moving the tape 3 past the gaps in such direction that any given portion bridges first the shorter gap 11 and then the longer gap 12, so that by energization of a coil 13 carried by the central core branch 8 the tape is subjected first to a saturating flux of one polarity which causes its magnetization to pass from 19 to 17 in Fig. 2, and subsequently to a non- saturating flux of opposite polarity which reduces its magnetization from 17 to 16. On leaving the head the tapes magnetization falls further to a point 20. The central core branch 8, of inverted T-shape, is disposed between a pair of inverted somewhat L-shaped side branches 9, 10 to form two parallel magnetic circuits interrupted by the gaps 11, 12, and each core is embraced by a frame 14 against one leg 14a of which it is clamped by a clamp member 15 engaged by a screw 16 in the other frame leg 14a. In addition to the head described there may be provided one or more further heads, each successive head being designed to carry the tape through a hysteresis loop which is smaller than that effected by the preceding head, thereby resulting in a more complete demagnetization of the tape. Specification 678,341 is referred to.