US Patent 9005059 Rear derailleur

A rear derailleur includes a base member, a movable member, a linkage and an electric motor unit. The base member includes a bicycle mounting portion for attaching to a bicycle. The movable member includes a chain guide having a first pulley that rotates around a first pulley axis in a center pulley plane that bisects the first pulley. The linkage movably supports the movable member relative to the base member. The electric motor unit is stationary with respect to at least a part of the base member and operatively coupled to the linkage to move the movable member relative to the base member between an outermost lateral position and an innermost lateral position. The electric motor unit is at least partially disposed inward of the center pulley plane while the movable member is disposed in the outermost lateral position.