An improved surgical instrument having an end effector mounted on the end of an elongate shaft extending from a handle. The end-effector has different operations, including grasping, cutting, and sealing and/or coagulating tissue, and one of the operations is controlled by a drive handle mechanism. The drive handle mechanism includes an actuator, a drive shaft and a spring assembly for transferring movement of the actuator to the drive shaft, which in turn controls the end effector. The drive handle mechanism limits the amount of force transferred from the drive handle mechanism to the end effector, preventing damage to the tissue. As the actuator is operated, the spring assembly transfers the movement of the actuator to the drive shaft and the end effector. At the same time, the spring assembly compresses to absorb some of the force applied. Such configuration prevents the tissue being unintentionally damaged by the end effector.
