GB1430008A - Unit for the magnetic brush development of latent electrostatic images - Google Patents

Abstract

1430008 Electrographic developing ING C OLIVETTI & C SpA 6 July 1973 [13 July 1972] 32287/73 Heading G2H A developer unit 1, of the kind in which a magnetic brush 12a is formed on the outer surface of a rotatable cylinder 6 of non-magnetic material enclosing a non-rotating magnet 7, is reciprocable towards and from the image surface 30a of a photo-conductive drum 30 in syncronism with the rotation of the drum 30, and includes means for adjusting the orientation of the magnet 7 about the axis of the cylinder 6 between first and second positions in which the arcuate extent of the part of the brush which is effective to transfer developer particles to the electrostatic image is different, and a third accessary position. The magnet 7, together with its associated flux diverting shunt 7a and pole shoe 7b, is normally positioned as shown in full lines but may be rotated about 15 degrees clockwise to the position indicated by broken lines to increase the length of arc over which the magnetic brush 12a wipes the drum 30 when a more intense developed image is required. The developer is replenished with concentrated developer (i.e. 50% toner 50% carrier) once in every eight operative cycles of the machine by a supply cylinder 16 of non-magnetic material which is rotated stepwise together with a magnet 17 housed within it. The concentrated developer is picked up by the cylinder 16 in two zones C, D, is levelled by a dosing flap 22 and scraped off into a developing container 3 of the unit 1 by a doctor blade 20. To empty spent developer from the container 3, a trap 4 is opened and the magnet 7 is rotated through 90 degrees to its accessory position where its flux diverting shunt 7a overlies the trap 4 and weakens the magnetic field in this region allowing the developer 12 to drop out. Rotation of the cylinder 6 by hand completes the discharge of the developer.