GB1499773A - Assembly comprising a head suitable for magnetic reading or magnetic writing - Google Patents

Abstract

1499773 Magnetic heads XEROX CORP 19 March 1975 [22 March 1974] 11401/75 Heading G5R An assembly for magnetically reading or writing information comprises a movable magnetic record medium 14 and a magnetic head with a transducing gap 24 defined between two pole pieces 16, 18, the gap width (distance between the pole pieces) being substantially perpendicular to the direction of movement of the medium 14 with the leading edges 20, 22 of the gap being gradually rounded and the trailing edges 26, 28 of the gap being sharp. The required gap shape may be provided by rounding leading corners of the pole pieces 16, 18, Fig. 2 (not shown), or by shaping as in Fig. 3 or by a pole piece shape intermediate Figs. 2 and 3. The pole pieces may be of metallic ferromagnetic material or ferrite, and the gap may be filled with glass, metal or oxide. Only the trailing edge parts 26, 28 of the pole pieces are effective during reading and writing, the tapering front gap portion acting during writing as a pre-erase gap to erase prior recorded data and guard bands on each side of the track, the width of which is defined by the gap width at the trailing edge, e.g. 30 Î 10<SP>-6</SP> inch. Thus although the gap length (i.e. polepiece width parallel to the track length) may be 0À002 to 0À006 inch, the head can record several thousand, e.g. 4000, bits per inch of track length, with up to more than 20,000 tracks per inch of record width. The gap 24 may be formed by rough grinding one side of a head initially having a parallel-sided gap.