Developing device

Claim 1

A developing device adapted to develop an electrostatic latent image on an electrostatic latent image-forming surface of an image carrier by jumping a nonmagnetic toner onto the image-forming surface, comprising: a casing containing a mixture of the nonmagnetic toner and a magnetic carrier; a hollow cylindrical body formed of a nonmagnetic material and rotatable in a position such that part of the hollow cylindrical body is buried in said mixture in said casing; magnet means, contained within said hollow cylindrical body, for forming a magnetic brush comprised of said mixture on an outer peripheral surface of said hollow cylindrical body by the magnetic force of the magnet means when said hollow cylindrical body is rotated; a rotatable developing roller positioned between said outer peripheral surface of the hollow cylindrical body and said electrostatic latent image-forming surface of the image carrier so as to be adjacent to but separated from the electrostatic latent image-forming surface and so as to be in contact with said formed magnetic brush; and voltage impressing means, electrically connected to the developing roller and the hollow cylindrical body, for generating an electric field between said roller and said body so as to transfer with a predetermined electrostatic charge the nonmagnetic toner portion of said mixture formed on the outer peripheral surface of the hollow cylindrical body onto an outer peripheral surface of the developing roller, whereby said nonmagnetic toner transferred onto the outer peripheral surface of the developing roller is jumped onto the electrostatic latent image-forming surface as the developing roller rotates by virtue of the electrostatic charge imparted to said transferred nonmagnetic toner by said voltage impressing means interacting with the electrostatic charge of said latent image to thereby develop said latent image.