Supporting body of a surgical instrument articulation

1. A robotic surgical instrument comprising:

a shaft;

an end effector element; and

an articulation connecting the end effector element to the shaft, the articulation comprising:

joints permitting the end effector element to adopt a range of orientations relative to a longitudinal axis of the shaft;

pairs of driving elements configured to drive the joints;

a supporting body having a bevelled surface and a groove adjacent to the bevelled surface; and

a redirecting pulley mounted on the bevelled surface such that the redirecting pulley rotates about a redirecting pulley axis transverse to the bevelled surface so as to redirect a driving element between two joints, that driving element being seated in the groove, and being constrained to move around the redirecting pulley.

2. The robotic surgical instrument as claimed in claim 1 , wherein the redirecting pulley comprises:

a mounting surface which faces the bevelled surface and is flush with the bevelled surface; and

an opposing surface which opposes the mounting surface.

3. The robotic surgical instrument as claimed in claim 1 , wherein the redirecting pulley is retained to the bevelled surface by a spindle, and wherein the spindle body is retained in a bore of the supporting body which loosely fits the spindle body.

4. The robotic surgical instrument as claimed in claim 1 , wherein the bevelled surface is not parallel to a longitudinal axis of the supporting body.

5. The robotic surgical instrument as claimed in claim 1 , wherein the supporting body is a rigid structure which couples a first joint and a second joint of the articulation.

6. The robotic surgical instrument as claimed in claim 5 , wherein the first joint is drivable by a first pair of driving elements, the first joint permitting the end effector element to rotate about a first axis transverse to a longitudinal axis of the shaft, and the second joint is driveable by a second pair of driving elements, one of the second pair of driving elements being constrained to move around the redirecting pulley.

7. The robotic surgical instrument as claimed in claim 6 , further comprising a first set of pulleys rotatable about the first axis, the second pair of driving elements being constrained to move around the first set of pulleys and the redirecting pulley, the redirecting pulley axis at an angle to the first axis so as to cause the redirecting pulley to redirect a first one of the second pair of driving elements from a take-off point of a first pulley of the first set of pulleys to a pick-up point of the second joint.

8. The robotic surgical instrument as claimed in claim 7 , wherein the bevelled surface is located in a plane parallel to a redirecting pulley plane defined by the take-off point of the first pulley of the first set of pulleys, the pick-up point of the second joint, and a point on the external profile of the articulation, the point on the external profile of the articulation being such that the redirecting pulley is encapsulated within the articulation when located in the redirecting pulley plane.

9. The robotic surgical instrument as claimed in claim 1 , further comprising:

a further end effector element;

the supporting body further comprising a further bevelled surface; and

a further redirecting pulley configured to redirect one of a pair of driving elements through the articulation, the further redirecting pulley mounted on the further bevelled surface such that the further redirecting pulley rotates about a further redirecting pulley axis transverse to the further bevelled surface.

10. The robotic surgical instrument as claimed in claim 9 , wherein the further bevelled surface is not parallel to the bevelled surface.

11. The robotic surgical instrument as claimed in claim 9 , wherein the redirecting pulley comprises:

a further mounting surface which faces the further bevelled surface and is flush with the further bevelled surface; and

a further opposing surface which opposes the further mounting surface.

12. The robotic surgical instrument as claimed in claim 9 , wherein the further redirecting pulley is retained to the further bevelled surface by a further spindle,

wherein the further spindle body is retained in a further bore of the supporting body which loosely fits the further spindle body.

13. The robotic surgical instrument as claimed in claim 9 , wherein the further bevelled surface is not parallel to a longitudinal axis of the supporting body.

14. The robotic surgical instrument as claimed in claim 9 , wherein the supporting body further couples a third joint to the first and second joints of the articulation.

15. The robotic surgical instrument as claimed in claim 14 , wherein the third joint is driveable by a third pair of driving elements, one of the third pair of driving elements being constrained to move around the further redirecting pulley.

16. The robotic surgical instrument as claimed in claim 15 , the third pair of driving elements being constrained to move around the first set of pulleys and the further redirecting pulley, the further redirecting pulley axis at an angle to the first axis so as to cause the further redirecting pulley to redirect a first one of the third pair of driving elements from a take-off point of a second pulley of the first set of pulleys to a pick-up point of the third joint.

17. The robotic surgical instrument as claimed in claim 16 , wherein the further bevelled surface is located in a plane parallel to a further redirecting pulley plane defined by the take-off point of the second pulley of the first set of pulleys, the pick-up point of the third joint, and a point on the external profile of the articulation, the point on the external profile of the articulation being such that the further redirecting pulley is encapsulated within the articulation when located in the further redirecting pulley plane.

18. The robotic surgical instrument as claimed in claim 15 the groove seating a second one of the third pair of driving elements, the groove being located such that the seated second one of the third pair of driving elements is partially enclosed in the redirecting pulley.

19. The robotic surgical instrument as claimed in claim 15 , wherein the supporting body comprises a further groove adjacent to the further bevelled surface, the further groove seating a second one of the second pair of driving elements, the further groove being located such that the seated second one of the second pair of driving elements is partially enclosed in the further redirecting pulley.

20. The robotic surgical instrument as claimed in claim 9 , wherein the bevelled surface and the further bevelled surface are symmetrical about a longitudinal axis of the supporting body.