Developing device with magnetic pole having magnetic spacer members

Claim 1

In a magnet roll developing device including a magnet roll composed of a roll-shaped supporting member made stationary with respect to a surface to be developed, said supporting member including a developing main magnetic pole opposed to the surface to be developed and a plurality of transfer magnetic poles, a non-magnetic rotary sleeve rotatably mounted around the outer peripheral surface of the magnet roll and a doctor blade for controlling a thickness of a developing agent layer held on the non-magnetic rotary sleeve, the improvement in which the developing main magnetic pole is divided into a plurality of magnet portions each having the same magnetic pole opposite the surface to be developed, said magnet portions spaced from each other to provide at least one space into which is arranged a spacing member composed of a magnetic body or magnet having a weak magnetic force in a direction such that the surface of said weak magnet is opposite in polarity to the poles of said magnet portions, a portion of the magnetic lines of force starting from the magnet surface of each of said magnet portions being directed toward said spacing member for forming an area in which magnetic lines of force are low in density near said spacing member, and the thickness of the developing agent layer held on said non-magnetic rotary sleeve being suitably adjusted to form at the magnet surface of each of said magnet portions an independent brush fur-like portion of the developing agent, each of said fur-like portions independently acting on the surface to be developed.