POWER SUPPLYING A BIPOLAR ELECTRIC

The invention relates to powering a bipolar electrocautery surgical instrument, in particular to a robotic surgical instrument comprising a shaft, an electrocautery end effector powered by an electrocautery element, and a hinge connecting the electrocautery end effector to the shaft. The hinge comprises: a first joint drivable by the first pair of drive elements, the first joint allowing rotation of the electrocautery end effector about a first axis perpendicular to the longitudinal axis of the shaft; and a second joint drivable by the second pair of drive elements, the second joint allowing rotation of the electrocautery end effector about a second axis perpendicular to the first axis. The electro-cautery element is defined to move about a first axis, and is defined to be wrapped around a second axis by at least one full turn. A path of the electro-cautery element between the shaft and the second joint is symmetrically opposed to a path of the first drive element of the second pair between the shaft and the