Articulation mechanism for surgical instrument

An articulating elongate surgical instrument comprising:

• a handle assembly;
• an elongated body portion extending distally from the handle assembly and defining a first longitudinal axis;
• a tool assembly pivotally supported on the distal end of the elongated body portion about a pivot axis substantially orthogonal to the first longitudinal axis;
• an articulation mechanism to effect the movement of the tool assembly;
• at least one articulation drive member having at least one retaining surface, the at least one articulation drive member being actuated by the articulation mechanism;
• a firing rod disposed adjacent the at least one articulation drive member, the firing rod for effecting the firing of surgical staples from the tool assembly, an actuating surface disposed upon the firing rod;
• an articulation locking assembly configured to selectively engage and disengage the actuating surface on the firing rod and to selectively engage and disengage from the at least one retaining surface of the at least one articulation drive member.