Iron core assembly for magnetizing columnar permanent magnets for use in electrostatic developing apparatus

Claim 1

An iron core assembly for magnetizing a columnar permanent magnet for use in an electrostatic developing apparatus comprising: a plurality of axially extending and circumferentially spaced magnetizable projections defining, at their radially inner ends, a throughbore for receiving a columnar permanent magnet to be magnetized, said inner ends being located in close proximity to the outer cylindrical surface of said columnar permanent magnet received by said throughbore, coil windings for magnetizing said magnetizable projections so as to provide circumferentially alternate magnetic poles, said coil windings being wound around said magnetizable projections and received by grooves formed between adjacent magnetizable projections, and wherein the circumferential width of said magnetizable projections is relatively large with respect to that of said grooves so as to constitute means for imparting abrupt polarity inversions to the columnar permanent magnet along the circumference of the latter.