Patent ID: 8532528

Claim:
An image forming apparatus comprising: a main assembly; a rotatable first coupling provided in said main assembly, said first coupling being rotatable by a driving source; and a transfer unit detachably mountable to said main assembly, said transfer unit being movable in a first direction when said transfer unit is dismounted from said main assembly, said transfer unit including a movable belt and a rotatable second coupling capable of receiving a driving force from said first coupling, wherein the first direction is parallel with a traveling direction of said belt, wherein one of said first coupling and said second coupling is movable in a second direction which is perpendicular to the first direction, and wherein when said transfer unit is dismounted from said main assembly, one of said first coupling and said second coupling is moved in the second direction to retract from the other of said first and second couplings by said transfer unit being moved in the first direction with said first coupling and said second coupling kept in contact with each other.