Contamination prevention system

Abstract

A system for minimizing contamination of an electrophotographic copier machine wherein toner particles and/or carrier beads are the contaminating agents. The leading edge of corona housings is positioned a substantial distance from the surface of a rotating drum so as to not affect the rotating boundary layer near the drum surface. In that manner, vortex formation within the corona housings may be prevented. The trailing edge of corona housings is given a curved shape and is at least as far removed from the drum surface as the leading edge. The system includes a vacuum scavenging chamber to remove toner particles entrained in the boundary layer. The leading edge of the scavenging chamber is given a curved shape to create a venturi in order to draw the boundary layer into the vacuum. Carrier beads are removed in the scavenging chamber since the broad curved leading edge interferes with fringe fields holding carrier beads to the surface. A positive preclean corona may be located within the scavenging chamber for further removal of carrier beads therein by neutralizing the photoreceptive charge and eliminating fringe fields. The trailing edge of the chamber is shaped as a knife edge.