Embodiments of the present invention provide an improved surgical instrument having an end effector mounted on the end of an elongate shaft extending from a handle. The end-effector is capable of several different operations, including grasping, cutting, and sealing and/or coagulating tissue, and one of the operations is controlled by a drive handle mechanism as described herein. The drive handle mechanism comprises 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 is arranged so as to limit the amount of force transferred from the drive handle mechanism to the end effector, thus preventing damage to the tissue being operated on. Specifically, as the actuator is operated by the user, the spring assembly is arranged to transfer the movement of the actuator to the drive shaft and the end effector. At the same time, the spring assembly is arranged to compress in order to absorb some of the force applied by the user. Such a configuration thereby prevents the tissue being unintentionally damaged by the end effector. <；Figure 6>；
