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.

Abstract: In a document copier machine an almost completely enclosed optics module is provided to keep the optical components isolated from the remainder of the machine and thereby minimize contamination of the optical components. The described module has three large openings. One of these openings is an air inlet which opens to the exterior of the machine for bringing cooling air to a fan located inside the module. The second opening is an air outlet to allow the optics cooling air to exit. The third opening is critical to contamination and is an aperture which opens to the interior of the machine to allow illumination to pass from the optics module to a photoreceptive surface. In order to prevent air flow into the module through the aperture, louvers are situated at the fan to direct an airstream onto a first Coanda surface to move air toward the aperture.