Latent electrostatic image developing apparatus

Abstract

An apparatus for developing a latent electrostatic image comprises a developer receptacle containing a developer composed of carrier particles and toner particles, a developer applying mechanism for holding on its surface a part of the developer in the developer receptacle and applying it to a latent electrostatic image to be developed, a toner receptacle containing toner particles, and a toner supplying mechanism to be selectively operated to supply toner particles to the developer in the developer receptacle from the toner receptacle. A detector detects the electrical conductivity of the developer in the developer receptacle. The apparatus further includes at least one of (a) a toner exhaustion signal producing device which, when the electrical conductivity of the developer detected by the detector exceeds a predetermined toner exhaustion reference value, produces a signal showing that the toner particles contained in the toner receptacle have been exhausted, (b) a carrier degradation signal producing device which, when the electrical conductivity of the developer detected by the detector falls below a predetermined carrier degradation reference value, produces a signal showing that the carrier particles in the developer have been degraded, and (c) a toner supplying signal producing device which, when the electrical conductivity of the developer detected by the detector exceeds a predetermined toner supply reference value, produces a signal for operating the toner supplying mechanism and a carrier degradation signal producing means which, when the toner supplying signal producing device does not continue to produce the signal in spite of the fact that the latent electrostatic image has been developed a predetermined number of times, produces a signal showing that the carrier particles in the developer have been degraded.

Dependencies are inferred from the claim text.