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AssigneeBunnington Corporation
InventorsBen W. Fagen, Jr., Dale B. Parks
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A magnetic brush developing system for electrostatic duplication uses a developer having a magnetic carrier and non-magnetic toner which is transferred by the brush to an electrostatic image. A analog signal is derived using a Hall sensor in contact with the brush and adjacent to a magnet of the brush. The location of the sensor after and downstream of the transfer point provides information in the signal both as to the absolute value of the concentration (ratio of toner to carrier by weight) as well as the rate of transfer of the toner to the electrostatic image. These signals are used to control the supplying of replenishment toner to the developer only when the concentration of toner drops below a predetermined desired value and then at a rate commensurate with the rate of transfer of toner to the electrostatic image.
The method for controlling the ratio of the non-magnetic toner to the magnetic carrier of the developer used in electrostatic reproduction of images which comprises the steps of deriving a signal which represents both the absolute value of said ratio and the amount of toner used for each of said images, and replenishing the amount of toner in said developer in response to said signal whenever said absolute value decreases below a predetermined value and at a rate corresponding to said amount.
A system for controlling toner concentration in a developer having a magnetic carrier and a non-magnetic toner which is carried in the form of a magnetic brush and transferred onto an electrostatic image bearing surface which comprises means for deriving a first signal having a magnitude which corresponds to said concentration and which varies in accordance with the amount of said toner transferred to said electrostatic image, and means for supplying toner to said developer when said first signal reaches a magnitude corresponding to said concentration being below a predetermined concentration and at a rate which varies with the magnitude of said signal.
Dependencies are inferred from the claim text.