Dual component developing material detecting device for electrostatic copying apparatus

Claim 1

An apparatus for use in an electrostatic copying apparatus for monitoring the concentration of toner in a developer having a mixture of toner and carrier particles, said apparatus comprising: a hopper for supplying toner; a stirring roller rotatable for stirring a carrier and the toner supplied from said hopper; detecting means for detecting the amount of the developer at a position adjacent said stirring roller, said detecting means comprising a fixed contact member and a movable contact member; discriminating means for discriminating an output signal from said detecting means for a predetermined interval during a period of rotation of said stirring roller, said discriminating means comprising a time constant circuit including a capacitor and a resistor connected in series, a switching element connected in parallel with said capacitor, a first comparison circuit for controlling said switching element when said fixed contact member and said movable contact member contact each other, a second comparison circuit for determining whether the level of an output from said time constant circuit is greater than a predetermined level, a timer for supplying an output signal after every said predetermined interval during a copying operation while said stirring roller is rotated, and a latch circuit operable in response to said output signal from said timer for storing a discriminated signal from said second comparison circuit; indicating means operable in response to an output signal from said discriminating means for indicating when the amount of said toner in the developer is less than a predetermined amount; and said discriminating means further comprising driving means, operable in response to the output signal from said latch circuit, for operating said indicating means during a time period when said latch circuit stores said discriminated signal from said second comparison circuit.

Claim 2

An apparatus for use in an electrostatic copying apparatus for monitoring the concentration of toner in a developer having a mixture of toner and carrier particles, said apparatus comprising: a hopper for supplying toner; a stirring roller rotatable for stirring a carrier and the toner supplied from said hopper; detecting means for detecting the amount of the developer at a position adjacent said stirring roller, said detecting means comprising a fixed contact member and a movable contact member; discriminating means for discriminating an output signal from said detecting means for a predetermined interval during a period of rotation of said stirring roller, said discriminating means comprising a time constant circuit including a capacitor and a resistor connected in series, a switching element connected in parallel with said capacitor, a first comparison circuit for controlling said switching element when said fixed contact member and said movable contact member contact each other, a second comparison circuit for determining whether the level of an output from said time constant circuit is greater than a predetermined level, a timer for supplying an output signal after every said predetermined interval during a copying operation while said stirring roller is rotated, and a latch circuit operable in response to said output signal from said timer for storing a discriminated signal from said second comparison circuit; indicating means operable in response to an output signal from said discriminating means for indicating when the amount of said toner in the developer is less than a predetermined amount; and said discriminating means further comprising driving means, operable in response to the output signal from said latch circuit, for operating said indicating means during a time period when said latch circuit stores said discriminated signal from said second comparison circuit.