The end effector comprises a pair of pivotally connected 104 jaw members (100, 102, fig 1) each having a flange 106, 108 with an elongate slot 110, 112 and a drive assembly having a drive pin 22 and a drive shaft 24. The drive pin is received in the slots such that movement of the drive shaft along the effector’s longitudinal axis causes the jaw members to move relative to each other. The drive pin is further moveable in a lateral direction A ensuring that the force is evenly distributed to both jaw members in the closed position. The effector may be controlled through one moveable jaw, but this has the same mechanical advantage of an end effector where both jaws are moveable. The drive shaft may have a slot 26 extending perpendicular to the longitudinal axis into which the drive pin is received, or the drive shaft may move in a perpendicular direction (Figs 5A & B), to allow the lateral movement of the drive pin.
