Patent ID: 8254812

Claim:
A driving unit for a photo conductor drum cartridge having a housing, a shaft mounted in the housing and having a radius D and an annual groove portion with a radius d shorter then the radius D, and a photo conductor drum sleeved on the shaft, the driving unit comprising: a gear having a main body, an extending portion extending from the main body for inserting into the photo conductor drum, and an axial hole passing through the main body and the extending portion for penetration of the shaft; and a conducting plate having a plate body mounted on the extending portion of the gear for abutting against an inner periphery of the photo conductor drum, a through hole formed at the plate body for penetration of the shaft, and an elastic arm extending from the plate body for stopping against the shaft, and defining an imaginary axis aligned with a center of the plate body and parallel to the shaft; wherein when the elastic arm of the conducting plate is perpendicular to the imaginary axis, a perpendicular distance L is defined between a distal end of the elastic arm and the imaginary axis and the distance L is longer than or equal to the radius d and shorter than the radius D, so that when the elastic arm is perpendicular to the imaginary axis, the distal end extends into the annual groove portion and remains unbent in the annual groove portion.