TONER SUPPLY SYSTEM FOR COPYING MACHINE

摘要

A system for continuously monitoring the concentration of toner in an electrostatic copying machine. The need for additional toner concentrate is detected by a photocell which receives varying amounts of light transmitted through a transparent monitoring tube positioned in the toner solution circulation path. If the toner solution has become too dilute, the photocell's resistance lowers to permit a periodically generated enabling pulse from the electronic control circuit to furnish an operating path for a positive-acting solenoid valve. Short timed bursts of toner concentrate are then added to the toner solution at spaced time intervals unitl the concentration exceeds a predetermined value; the concentrate is injected into the solution by an immersed venturi tube arrangement. A manual operating mode is also included for providing an instantaneous burst of toner concentrate independent of the detection circuitry.