GB1310444A - Electrostatic image development apparatus - Google Patents

Abstract

1310444 Electro-photographic development apparatus XEROX CORP 30 June 1970 [3 July 1969 (4)] 31614/70 Heading G2H A development electrode in an opposed flow, two component developer system is in close parallel relationship with a photo-conductive surface 10 and provides an increasing potential difference in the direction of travel of surface 10 being formed of three control members 70, 71, 72 each held at a different potential, the potentials being chosen to control the toner concentration gradient across the flow of developer. Two of the control members 70, 71 have indentations for redirecting the developer flow on to the surface 10. The first electrode member 70 (in the direction of travel of surface 10 through the development zone) is held at a potential lower than in the background areas of the charge image so that toner particles are forced upwards towards the surface 10 producing a high toner concentration adjacent the surface 10. Toner particles are dislodged from carrier particles by impaction on the drum surface 10 caused by a chamfer 74 on the edge of the electrode 70. The second electrode member 71 is held at a potential intermediate that in the image and non-image areas resulting in the removal of toner from background areas as well as development in image areas. "Lead edge effect" is reduced by providing a groove (85) Fig. 4, (not shown) in the inverted portion of electrode 71 so as to direct the developer flow into contact with the drum surface 10. The third electrode 72, acting as a clean-up electrode, is held at a potential 150-700 volts above the potential in image areas thereby attracting toner particles to the electrode side of the flow and allowing denuded carrier particles to remove weakly adhering particles from the surface 10.