Developing device for use on an electrostatic copying apparatus

Abstract

An electrostatic copying machine apparatus includes a developing device having a fixedly positioned permanent magnet and a hollow developing sleeve formed of a non-magnetic material mounted coaxially about the permanent magnet for rotation thereabout. Toner supplied to the periphery of the sleeve forms thereon a magnetic brush which is conveyed by rotation of the sleeve to a developing position whereat the toner is transferred to a photoreceptor as a visible toner image. A bristle cutting member is positioned upstream of the developing position to restrict the length of the magnetic brush. A blade member formed of a non-magnetizable material prevents solidification of the toner on the periphery of the sleeve and is positioned upstream of the bristle cutting member. The blade member slides in contact with the periphery of the sleeve at a scraping position. The permanent magnet has spaced therearound at equal circumferential intervals a plurality of magnetizing positions having magnetic poles. One pole is at a first magnetizing position confronting the bristle cutting member, and another pole is at a second magnetizing position confronting the scraping positions. These two poles are of opposite polarities and are adjacent to each other. At least one magnetizing position includes a pair of poles of the same polarity.