GB1216690A - Sensing the developing capability of xerographic developer material - Google Patents

Abstract

1,216,690. Developing electrostatic images. RANK XEROX Ltd. Dec.31, 1968 [Jan. 2, 1968(2)], No.61834/68. Heading G2H. The density of electroscopic toner in developer material is sensed by positioning an electrode adjacent the flow of developer material through a sensing chamber 300 while alternating the polarity of the electrode to attract and repel toner to and from the electrode and passing a beam of light through the electrode towards a photo-cell which generates a signal applied through a control circuit to a toner dispenser 10. The toner dispenser 10 has a container 120 provided with a reciprocutory dispensing plate through which a metered quantity of toner can fall to the reservoir portion of the developer housing 20. The plate is reciprocated by an electric motor MOT-1. The chamber 300, Fig. 6 has photo-electric cells P-1 and P-2 positioned to receive light from a lamp LMP-1. Electrically conductive transparent electrodes 350 are positioned in the flow path of developer material from an earthed flow divider 303 to an aperture 304. Each electrode 350 has electrically isolated areas (350(A) and 350(B)) Fig. 8 (not shown) connected to terminals (10, 15) Fig. 4 (not shown) to provide the alternating polarity of these area Fig.5 (not shown). The alternating polarity causes alternate attraction and repulsion of the toner to the electrodes 350 Fig.6. The photo-electric cells P-1 and P-2 are included in a bridge circuit, Fig. 9. A high resistance of P-2 indicates a high toner concentration on the electrode 350. The bridge circuit feeds a fluctuating voltage Fig. 5 (not shown) through line 2, Fig. 9, to control circuit Fig. 4(b) (not shown). Should this voltage be insufficient to produce conduction of transistor (Q19), indicating a low toner concentration, the motor MOT-1, Fig. 2, will be energized to cause toner to be dispersed for a period e.g. 2“ seconds to increase the concentration. A manual override is provided to permit an operator to dispense toner into the developer apparatus for a period e.g. 10 seconds. The density of the image may be varied by a potentiometer R-24 to alter threshold voltage of transistor Q19. Reference has been directed by the Comptroller to Specification 1,135,743.