Patent ID: 7428396

Claim:
A power transmitting device for a developing device of an image forming apparatus, comprising: a driving section comprising at least one rotational member which is rotated by power supplied from an external source, the at least one rotational member moving between a coupled position where it is coupled with a developing roller and an uncoupled position where the at least one rotational member is uncoupled from the developing roller; a rotational shaft comprising at least one cam, the cam engaging the at least one rotational member to move the at least one rotational member between the coupled position and the uncoupled position; and a shaft driving section for rotating the rotational shaft in one direction, wherein the cam is provided with a cam surface with a first section, the first section having a normal line at each point where it contacts the at least one rotational member, the normal lines being oriented so that they do not intersect a line connecting a rotational axis of the cam and a maximum stroke point MP of the cam except at the rotational axis of the cam.