Browse Prior Art Database

Original Publication Date: 1983-Apr-30
Included in the Prior Art Database: 2004-Apr-04

Publishing Venue

Xerox Disclosure Journal


An electrophotographic printing machine frequently employs a developer mixture comprising carrier granules having toner particles adhering triboelectrically there-to. As the toner particles are depleted, i.e., during the formation of copies, additional toner particles are added to the developer material. These newly dispensed toner particles may produce excessive background on the copy sheets if they are not sufficiently charged during the first few cycles of machine operation. This problem becomes worse if slow charging toner particles are employed. For effective triboelectric charging, relative motion and friction between the toner particles and carrier granules should be maintained. To insure effective charging, close contact between the carrier granules and toner particles, as well as sheering motion should be provided. As shown in Figure 1, a pair of inclined plates 10 and 12 form a channel for the passage of developer material. The upper plate 10 provides a boundary for the powder flow and for promoting contact. However, the channel width is designed to match the anticipated dispense rate so that no normal pressure will be on the developer material. This insures that impaction is not aggrevated. In order to further add to flow shearing, the lower plate 12 is oscillated in the flow direction, i.e., in the direction of arrow 14. Plates 10 and 12 are substantially identical. Figure 2 shows the details of plate 10. As depicted thereat, plate 10 includes a plurality of protuberances 16. Each of these protuberances is preferably spherical. Protuberances 16 produce branching of the developer material flow as shown by arrows 18. In this way, further mixing of the developer material is promoted. Plates 10 and 12 are arranged such that the flow is a converging-diverging type. This is shown more clearly in Figure 3. Thus, the protuberances of plate 10 are positioned over the regions of plate 12 not having protuberances.