End effector apparatus for a surgical instrument

A method for actuating an end effector for a surgical instrument, the end effector including a first jaw being mounted on a first revolute joint, the first jaw having a manipulating portion extending forwardly from the first revolute joint and a lever arm projecting rearwardly from the first revolute joint, a second jaw being mounted on a second revolute joint and having a manipulating portion generally opposing the manipulating portion of the first jaw, the method comprising:

• causing reciprocating movement of a coupler having an actuation end disposed overlapping the lever arm of the first jaw, the first revolute joint and the second revolute joint being laterally spaced apart to provide a clearance for the actuation end of the coupler such that the clearance is configured to receive a distalmost end of the actuation end,
• transmitting reciprocating movements of the coupler through a linkage extending rearwardly between the actuation end of the coupler and the lever arm of the first jaw, the movement of the linkage being operable to cause opening and closing movements of the first jaw about the first revolute joint, the first linkage being pivotally connected to the coupler by a first pivot pin and pivotally connected to the lever arm by a second pin, wherein a first linkage length is defined between the first pivot pin and the second pivot pin, and wherein a first arm length is defined between the first revolute joint and the second pivot pin,
• wherein the first arm length and the first linkage length are selected such that:
• the distalmost end of the actuation end is positioned distal to a proximal end of the first revolute joint and between the first revolute joint and the second revolute joint and is within the clearance when the end effector apparatus is in an open state;
• and
• the distalmost end of the actuation end is positioned rearwardly of the first revolute joint and the clearance when the end effector apparatus is in a closed state.