Abstract: In an electrostatic copying method and apparatus employing a two-component image-developer composition comprising magnetizable carrier particles and toner pigment particles, the removal of magnetizable carrier particles from the photoconductive surface is accomplished by means of an electromagnetic scavenger assembly comprising an electromagnet and a fixed nonmagnetizable shield mounted in close association between said electromagnet and the photoconductive surface. During the copying cycle, the electromagnet is energized to create a strong magnetic field around the shield and to cause magnetizable articles to be drawn against the shield from the photoconductive surface. After the copying cycle, the electromagnet is automatically de-energized to discontinue the strong magnetic field in the area of the shield, causing the magnetizable particles to fall from the shield into a collection tray by means of gravity.

Abstract: In an electrostatic copying method and apparatus employing a two-component image-developer composition comprising magnetizable carrier particles and toner pigment particles, the removal of magnetizable carrier particles from the photoconductive surface is accomplished by means of an electromechanical scavenger assembly comprising a movable magnet and a fixed non-magnetizable shield mounted in close association between said magnet and the photoconductive surface. During the copying cycle, the magnet is moved adjacent the fixed shield to create a strong magnetic field around the shield and to cause magnetizable articles to be drawn against the shield from the photoconductive surface. After the copying cycle, the magnet is moved away from the fixed shield to withdraw the strong magnetic field from the shield, causing the magnetizable particles to fall from the shield into a collection tray by means of gravity.

Abstract: A powder density control means is provided for use in a photocopier machine of the type in which a photoconductor is charged in accordance with an image to be recorded thereon and is developed by contact with a toner powder attracted thereto from a mixture of carrier particles and toner powder carried by a developer assembly including a replenishment means for periodically adding toner powder. A high value resistance and a bias supply are serially coupled to a magnetic brush of the developer assembly. The voltage across the magnetic brush provides an indication of how heavily the latent image on the photoconductor is being toned. The change in magnitude of the voltage on the brush is sensed and when a predetermined amount of voltage change is detected, an additional amount of toner powder is supplied by the replenisher to the developer unit for such change.