Mixing device for blending a developer consisting of carrier particles and toner

摘要

In a developer station for an electrophotographic printing or copying machine, there is provided mixing apparatus for mixing fresh toner with developer mix particles and maintaining an adequate concentration of toner in the developer mix particles being picked up and carried for inking by the developer drum. The apparatus comprises a first mixing screw disposed along the floor of the developer station for conducting particles in a first direction along the length of the developer drum and a second mixing screw disposed in a partitioned off mixing chamber lying above the level of the first mixing screw which receives a portion of the developer particles carried by the developer drum off one end of the drum by means of a scraper plate. The second mixing screw is disposed in the mixing chamber for passing particles in a direction opposite to that of the conveying direction of the first mixing screw. The partition wall is formed with an opening such that the discharge end of the second mixing screw communicates with the lead end of the first mixing screw. In the mixing chamber, fresh toner particles are mixed with that portion of the used developer particles conducted by the scraper plate and this blend is mixed during transport along the second screw.