US Patent 7142795 Process unit

The process unit includes a drum unit configured to mount an image carrier which carries an electrostatic latent image, onto a casing, a holder cover configured to hold a side surface portion of the drum unit, a developer unit configured to mount a developer roller which develops the electrostatic latent image, onto the casing, a holder cover configured to hold a side surface portion of the developer unit, an aligning device having a recess portion formed in one of the holder covers of the drum unit and the developer unit, and a projecting portion formed on the other holder cover, which fit with the recess portion, and configured to align the drum unit with respect to the developer unit as the recess portion and the projecting portion are fit with each other, and a fixation tool configured to fix the engaged recess portion and projecting portion together.