A control valve includes a wall defining a chamber having an inlet end, a middle portion and an outlet end in axial alignment. A valve seat and a valve plug are proportioned to fit the valve seat arranged in axial alignment within the chamber. At least one of the valve seat and valve plug is configured for axial movement towards the other. Relative movement between the valve plug and valve seat is enabled by a cam mechanism including a first shaft assembly extending axially along the chamber and fixed to one of the valve plug and valve seat. A cam is operable with the first shaft assembly to separate or draw together the valve seat and valve plug along the axis of the chamber. A second shaft assembly is coupled to the cam and extends through the middle portion of the chamber wall terminating in a free end attachable to a rotary actuator.