Apparatus for Sensing Deterioration of Developing Substance Including Ferromagnetic Carrier and Non-Magnetic Toner Particles

Author:  Sakamoto, Miyakawa,Tatsumi
Source:  US Patent 4,195,260
Doc ID:  1980011
Year of Publication:  1980
Abstract:  
Deterioration of a dry developing substance causes toner particles to be so strongly adhered to carrier particles that they cannot be readily separated therefrom. The present apparatus comprises means for applying a predetermined electrostatic or air suction force to the developer to readily remove toner therefrom except for spent toner particles strongly adhered to the carrier particles. The toner density, or the ratio of toner to carrier particles, is then measured electromagnetically or optically and compared to a reference value. The developer deterioration determines what proportion of toner will be removed from the developer by said force and thereby the subsequently sensed toner density. The higher the sensed toner density, the greater the degree of deterioration.