Surgical instrument driving mechanism
A robotic surgical instrument comprising a shaft, an articulation attached to the distal end of the shaft, and a driving mechanism at the proximal end of the shaft. The articulation comprises a plurality of joints for articulating an end effector, the plurality of joints driveable by at least first and second pairs of driving elements. The driving mechanism comprises a pulley arrangement and a pulley drive. The pulley arrangement comprises first and second pulleys attached together such that their separation is fixed, wherein the first pair of driving elements is constrained to move around the first pulley, and the second pair of driving elements is constrained to move around the second pulley. The pulley drive is configured to linearly displace the pulley arrangement, such that a linear displacement in one direction away from the distal end of the shaft causes the first pair of driving elements to be tensioned and the second pair of driving elements to be de-tensioned, and a linear displacement in an opposing direction towards the distal end of the shaft causes the second pair of driving elements to be tensioned and the first pair of driving elements to be de-tensioned.
1. A robotic surgical instrument comprising:
a shaft;
an articulation attached to the distal end of the shaft, the articulation comprising a plurality of joints configured to articulate an end effector, the plurality of joints driveable by at least first and second pairs of driving elements; and
a driving mechanism at the proximal end of the shaft, the driving mechanism comprising:
a pulley arrangement comprising first and second pulleys attached together such that their separation is fixed, wherein the first pair of driving elements is constrained to move around the first pulley, and the second pair of driving elements is constrained to move around the second pulley; and
a pulley drive configured to linearly displace the pulley arrangement, such that a linear displacement in a direction away from the distal end of the shaft causes the first pair of driving elements to be tensioned and the second pair of driving elements to be de-tensioned, and a linear displacement in an opposing direction towards the distal end of the shaft causes the second pair of driving elements to be tensioned and the first pair of driving elements to be de-tensioned.
2. A robotic surgical instrument as claimed in claim 1 , wherein the pulley drive is configured to linearly displace the pulley arrangement such that a linear displacement in the direction away from the distal end of the shaft causes the first pair of driving elements to be tensioned and the second pair of driving elements to be compressed, and a linear displacement in the opposing direction towards the distal end of the shaft causes the second pair of driving elements to be tensioned and the first pair of driving elements to be compressed.
3. A robotic surgical instrument as claimed in claim 1 , wherein the articulation is a wrist articulation and one of the plurality of joints is a pitch joint configured to pitch the wrist articulation, the first and second pairs of driving elements being connected to the wrist articulation such that when the pulley drive linearly displaces the pulley arrangement in the direction away from the distal end of the shaft the wrist articulation pitches in one direction about the pitch joint, and when the pulley drive linearly displaces the pulley arrangement in the opposing direction towards the distal end of the shaft the wrist articulation pitches in an opposing direction about the pitch joint.
4. A robotic surgical instrument as claimed in claim 1 , wherein the pulley drive is configured to linearly displace the pulley arrangement in a direction parallel to the longitudinal axis of the shaft.
5. A robotic surgical instrument as claimed in claim 1 , wherein at the proximal end of the shaft, the first pair of driving elements is constrained to move around the first pulley only with no further intervening pulleys, such that when the pulley drive linearly displaces the pulley arrangement away from the distal end of the shaft, the first pair of driving elements is tensioned.
6. A robotic surgical instrument as claimed in claim 1 , wherein the second pair of driving elements is further constrained to move around third and fourth pulleys, the third and fourth pulleys being located further from the articulation than the pulley arrangement, wherein the second pair of driving elements extends from the articulation through the shaft, around the third and fourth pulleys to the second pulley, such that when the pulley drive linearly displaces the pulley arrangement towards the distal end of the shaft, the second pair of driving elements is tensioned.
7. A robotic surgical instrument as claimed in claim 1 , the driving mechanism further comprising a first drive configured to drive the first pair of driving elements, such that a drive applied in one direction causes a first one of the first pair of driving elements to be tensioned and a second one of the first pair of driving elements to be compressed, and a drive applied in an opposing direction causes the first one of the first pair of driving elements to be compressed and the second one of the first pair of driving elements to be tensioned.
8. A robotic surgical instrument as claimed in claim 7 , wherein one of the plurality of joints is configured to actuate opposing first and second jaws of an end effector, the first pair of driving elements being connected to the articulation such that when the first drive applies a drive in one direction the first jaw rotates in one direction about that joint, and when the first drive applies a drive in an opposing direction the first jaw rotates in an opposing direction about that joint.
9. A robotic surgical instrument as claimed in claim 7 , wherein the first drive is a linear drive.
10. A robotic surgical instrument as claimed in claim 1 , the driving mechanism further comprising a second drive configured to drive the second pair of driving elements, such that a drive applied in one direction causes a first one of the second pair of driving elements to be tensioned and a second one of the second pair of driving elements to be compressed, and a drive applied in an opposing direction causes the first one of the second pair of driving elements to be compressed and the second one of the second pair of driving elements to be tensioned.
11. A robotic surgical instrument as claimed in claim 10 , wherein one of the plurality of joints is configured to actuate opposing first and second jaws of an end effector, the second pair of driving elements being connected to the articulation such that when the second drive applies a drive in one direction the second jaw rotates in one direction about that joint, and when the second drive applies a drive in an opposing direction the second jaw rotates in an opposing direction about that joint.
12. A robotic surgical instrument as claimed in claim 10 , wherein the second drive is a linear drive.
13. A robotic surgical instrument as claimed in claim 1 , wherein the driving elements are elongate and flexible.
14. A robotic surgical instrument as claimed in claim 1 , wherein the driving elements are cables.
15. A robotic surgical instrument as claimed in claim 1 , wherein the driving elements resist compression and tension forces.
16. A robotic surgical instrument as claimed in claim 1 , wherein each pair of driving elements is formed of opposed portions of a single elongate element secured to one of the plurality of joints of the articulation.
17. A robotic surgical instrument as claimed in claim 1 , wherein each driving element of the first pair of driving elements is formed of a distinct elongate element secured to one of the plurality of joints of the articulation and secured to the first pulley.
18. A robotic surgical instrument as claimed in claim 1 , wherein each driving element of the second pair of driving elements is formed of a distinct elongate element secured to one of the plurality of joints of the articulation and secured to the second pulley.