Image-forming apparatus comprising a process unit

An electrophotographic image forming apparatus comprising:

• an apparatus body;
• an electrostatic latent image carrying body;
• means for uniformly electrifying said carrying body;
• means for conducting an optical exposure on said carrying body to form an electrostatic latent image thereon;
• means for developing said electrostatic latent image to form a toner image on said carrying body;
• means for transferring said toner image from said carrying body onto a printing sheet;
• means for fixing said toner image to said printing sheet;
• means for cleaning to remove residual toner from said carrying body;
• means for returning said residual toner removed by said cleaning means to said developing means;
• a process unit detachably mounted on said apparatus body and accommodating therein at least said electrostatic latent image carrying body, said electrifying means, said exposure means, said cleansing means and said toner returning means;
• and
• a toner cartridge for supplying toner into said process unit, said toner cartridge being detachably mounted on said process unit, and wherein said toner cartridge can be moved, when said toner cartridge is mounted on said process unit, between a first position in which toner in said toner cartridge is allowed to be supplied to said process unit from said toner cartridge and a second position in which toner in said toner cartridge is prevented to be supplied therefrom, and a means is provided for automatically locking said toner cartridge within said process unit when said toner cartridge is in said first position and automatically releasing said lock when said toner cartridge is in said second position.

An electrophotographic image forming apparatus comprising:

• an apparatus body;
• an electrostatic latent image carrying body;
• means for uniformly electrifying said carrying body;
• means for conducting an optical exposure on said carrying body to form an electrostatic latent image thereon;
• means for developing said electrostatic latent image to form a toner image on said carrying body;
• means for transferring said toner image from said carrying body onto a printing sheet;
• means for fixing said toner image to said printing sheet;
• means for cleaning to remove residual toner from said carrying body;
• means for returning said residual toner removed by said cleaning means to said developing means;
• a process unit detachably mounted on said apparatus body and accommodating therein at least said electrostatic latent image carrying body, said electrifying means, said exposure means, said cleansing means and said toner returning means,
• wherein said process unit comprises a drum unit including at least said electrostatic latent image carrying body and said cleaning means, a developing unit including at least a developing roller, a toner mixing agitator and a toner chamber, and said drum unit and said developing unit are unitary combined together as a single process unit,
• wherein said drum unit comprises a first screw member for transporting the residual toner scraped and removed by said cleaning means and a second screw member connected to said first screw member and extending perpendicularly thereto, and said developing unit comprises a third screw member for returning the toner to said toner chamber, a toner recirculation passage is formed between said third screw member and said first and second screw members when said drum unit and said developing unit are combined together.

A process unit adapted to be used in an electrophotographic image forming apparatus, said process unit comprising:

• an electrostatic latent image carrying body;
• means for uniformly electrifying said carrying body;
• means for uniformly electrifying said carrying body;
• means for conducting an optical exposure on said carrying body to form an electrostatic latent image thereon;
• developing means for developing said electrostatic latent image to form a toner image on said carrying body;
• means for cleaning to remove residual toner from said carrying body;
• toner returning means for returning said residual toner removed by said cleaning means to said developing means;
• said developing means comprising:
• a housing in which a toner chamber is defined;
• a developing roller rotatably mounted in said housing;
• an agitator rotatably mounted in said housing so as to be positioned in said toner chamber;
• a partitioning member provided in said housing for defining a carrier chamber adjacent to said developing roller;
• said toner returning means comprising means for recirculating said residual toner removed from said carrying body to said toner chamber of the developing means;
• and
• a toner cartridge for supplying toner into said process unit, said toner cartridge being detachably mounted on said process unit,
• wherein said toner cartridge can be moved, when said toner cartridge is mounted on said process unit, between a first position in which toner in said toner cartridge is allowed to be supplied to said process unit from said toner cartridge and a second position in which toner in said toner cartridge is prevented to supplied therefrom, and a means is provided for automatically locking said toner cartridge within said process unit when said toner cartridge is in said first position and automatically releasing said lock when said toner cartridge is in said second position.