Xerox Corporation

Robert A Downing

Hadi K Mahabadi

Sheau V Kao

Gerald R Allison

Lorin K Hansen

Frank P Lee

Geroge Liebermann

Gopalan Vijayakumar

A method for making conductive toner particles includes (A) heat treating in fluidized bed processing equipment a mixture of non-conductive toner particles containing a thermoplastic resin and a colorant, and an effective amount of conductive powder blended with and coated on surfaces of the non-conductive toner particles, wherein the heat treatment is carried out at a temperature at or above the glass transition temperature of the resin for a period of time at least sufficient to fuse the conductive powder onto the surfaces of the non-conductive toner particles, and then (B) cooling the heated conductive toner particles to a temperature below the glass transition temperature of the resin. The final toner particles have a conductivity of at least about 10.sup.-8 ohm.sup.-1 -cm.sup.-1 and preferably from about 10.sup.-4 to about 10.sup.-8 ohm.sup.-1 -cm.sup.-1.

Preparation of conductive toners using fluidized bed processing equipment

A system is disclosed that monitors the concentration of material in a fluid carrier which includes means for circulating the fluid carrier within a substantially closed loop system and means for measuring the concentration of material carried in the fluid. The measuring means includes means to detect rapid changes in transmissivity of the fluid carrier, which are indicative of the presence of entrained air bubbles in the fluid carrier, so that measurements of material concentrate under such conditions may be ignored or rejected. Further, to ensure that an accurate measurement of concentrated material depletion is being observed, more than one consecutive measurement is made and validated before concentrate is finally added to the fluid carrier in the system. In the preferred embodiment, the determination of whether air bubbles may be entrained in the fluid carrier is accomplished by determining a disparity between two consecutively measured samples to have been greater than a predetermined value. If such a disparity exists, the measurement sampling rate is increased until the disparity between consecutively measured samples is again less than the predetermined value, at which time sampling is again performed at slower sampling rate. If a disparity exists between several consecutive samples and the disparity in each case remains below the predetermined value, the samples so observed are determined as valid and representative of continuous depletion of the concentrate material in the fluid carrier. When several of these consecutive and validated sample values exceeds a predetermined threshold and there has been no interruption in such sampling due to a disparity between samples greater than the predetermined value, an enablement will be provided to permit concentrate material to be added to the fluid carrier. The system of this invention has particular application to the monitoring the level of toner concentrate in a fluid carrier of fluid toner development system in an electrographic printer/plotter system or machine.

System and method for monitoring and maintaining concentrate material in

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San Jose, CA, United States of America

Robert A Downing