A surgical stapling and severing instrument particularly suited to endoscopic procedures incorporates a handle that produces separate closing and firing motions to actuate an end effector. In particular, the handle produces multiple firing strokes in order to reduce the required amount of force required to fire (i.e., staple and sever) the end effector. A linked transmission reduces the required handle longitudinal length, yet achieves a rigid, strong configuration when straightened for firing. A spring-biased side pawl firing mechanism is enabled by activation of an Electroactive Polymer (EAP) block actuator that overcomes a disengagement spring bias and moves a linked rack into proximity with a side pawl firing mechanism. Thereby, various sensed or commanded inputs may be incorporated to prevent inadvertent firing.
