Image forming apparatus having spacing roller for maintaining uniform spacing between image bearing member and developing material supplying means

An image forming apparatus, comprising:

• an image bearing member for bearing an electrostatic latent image, said image bearing member being rotatable in a direction and an edge thereof being made of an electrically insulative material;
• a developing means for developing the electrostatic latent image in a reversing development process, said developing means including developing material and a developing roller;
• a positioning roller rotatably supported on a rotating shaft of the developing roller and making contact with the edge of said image bearing member so as to position the developing roller relative to the image bearing member;
• a housing for covering said positioning roller, said housing having an opening wherefrom said positioning roller protrudes on a surface of the housing that confronts said image bearing member;
• and
• a seal member provided around the opening so as to seal up a gap between said housing and said image bearing member.

A developing device, comprising:

• a developing material supplying roller rotatably provided in a neighborhood of a moving image bearing member bearing an electrostatic latent image;
• a spacer collar disposed on both ends of a rotating shaft of said developing material supplying roller and making contact with an edge of the image bearing member;
• a housing for covering said spacer collar, said housing having an opening wherefrom said spacer collar protrudes;
• and
• a seal member provides around the opening, a thickness of said seal member being not shorter than a length thereof whereby said spacer collar protrudes from said opening.