Patent ID: 6041207
Filing Date: 2000-03-21
Classification: B82Y,G03G

Abstract:
An electrostatic latent image developing apparatus comprising:a developer tank defining an interior adapted for containing toner particles and magnetized carrier particles, and for imparting an electrostatic charge to at least some of said toner particles;a hollow, cylindrical developing sleeve, said developing sleeve being rotatably drivable about its longitudinal axis in a first direction, and defining an outer surface in communication with said interior of said developer tank at, at least a first location;an electrostatic latent image bearing member defining a surface adapted to have an electrostatic latent image formed thereon, said surface being closely spaced to said outer surface of said developer sleeve at a second location substantially opposite to said first location;a stationary magnet fixedly disposed inside said rotatable developing sleeve, said magnet defining a number of magnetic poles circumferentially spaced about the longitudinal axis of said developing sleeve;said magnetic poles including:a developing magnetic pole having a first polarity located substantially adjacent to said second location;a developer separating magnetic pole and a developer sucking magnetic pole both having the same second polarity, opposite to said first polarity, located circumferentially adjacent to one another, with said developer sucking magnetic pole being located downstream in said first direction from said developer separating magnetic pole substantially adjacent to said first location;a first even number of intermediate magnetic poles of alternating polarities located in circumferentially spaced relation to one another between said developing magnetic pole and said separating magnetic pole such that the polarity of said first even number of intermediate magnetic poles alternates between said second polarity and said first polarity in said first direction between said developing magnetic pole and said developer separating magnetic pole, anda second even number of intermediate magnetic poles of alternating polarity located in circumferentially spaced relation to one another such that the polarity of said second even number of magnetic poles alternates between said first polarity and said second polarity in said first direction between said sucking magnetic pole and said developing magnetic pole; anda doctor element for limiting the thickness of said layer of developer layer carried by said sleeve, wherein said doctor element is adapted to interact with a of developer located on said developer sleeve approximately midway between a pair of said second even number of alternating polarity magnetic poles located between said developer sucking magnetic pole and said developing magnetic pole;wherein the speed of rotation of said developer sleeve, and the spacing, magnitude and direction of the magnetic force provided by said magnetic poles are selected such that (1) the rise of developer magnetically adhered to said surface of said developing sleeve is small between adjacent magnetic poles; (2) said developer undergoes a chain-like rotation on said surface of said developer sleeve upon passing each of said magnetic poles; (3) toner is transferred from said developer on the surface of said developer sleeve to said latent image bearing member at said second location when said latent image bearing member has an electrostatic image formed thereon; and (4) the area of said developer having the weakest charge abuts said developer sleeve surface in the vicinity of said developer separating magnetic pole.