A CONSTANT DISPENSE TONER DISPENSER
Original Publication Date: 1984-Jun-30
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
Frequently, a toner dispenser does not provide a uniform dispense rate as a function of time. Generally, the toner dispenser employs a toner hopper in communication with an auger which discharges the toner particles therefrom. The auger comprises a helical member disposed interiorly of a tube having a plurality of apertures therein. As the helical member rotates, toner particles are fed from the hopper along the tube so as to be dispensed from the apertures therein. Ideally, when the toner density in the auger is constant, the toner mass dispense rate is determined solely by the angular velocity of the helical member. Alternatively, in another ideal case, if the toner particle density varies and toner dispensing is vertical, and there are no adhesion forces, only gravitational forces, the torque on the helical member is proportional to the density of the toner particles. In this latter case, it requires constant power to maintain a constant mass dispense rate. In actual toner dispensing, the situation is a function of many parameters including adhesion and bearing friction. To achieve a constant toner particle dispense rate, the angular velocity of the helical member must be a ComDlicated function of these parameters. This is not always feasible. It is proposed that for a specific toner dispenser, a constant toner dispense rate can be approximated by matching the angular velocity of the helical member to torque relation to the measured toner particle dispense to torque relationship. A simple way to provide a torque dependent drive is to utilize a small DC motor. The DC motor turns at an angular velocity such that the power delivered to the load and dissipated by friction is equal to the power consumed in the reactive portion of the motor impedance. 41-0, the current through the DC motor is proportional to the torque that it is producing. By inserting an external resistor in a series with the DC motor, the motor will operate at constant power, constant torque, or constant speed.