Articulation capstan tension retainment using clutch mechanism

1. A surgical tool, comprising:

a drive housing with an elongate shaft extending therefrom and an end effector arranged at a distal end of the elongate shaft;

a drive input rotatably mounted to the drive housing and an input shaft extending from the drive input, the input shaft defining a rotational axis;

upper and lower capstans mounted to the input shaft;

first and second drive cables coupled to the upper and lower capstans, respectively, and extending to the end effector; and

a clutch feature including a plurality of ratchet teeth on at least a first one of the upper and lower capstans, each of the ratchet teeth being radially asymmetrically shaped about the rotational axis and arranged to selectively mate with at least one tooth on a second one of the upper and lower capstans to permit the upper capstan and the lower capstan to rotate with respect to one another in at least one angular direction about the rotational axis, the clutch feature movable between an engaged position, where rotation of the input shaft in either angular direction rotates the upper and lower capstans in the same angular direction, and a disengaged position, where the upper and lower capstans are rotatable independent of each other in the at least one angular direction.

2. The surgical tool of claim 1 , further comprising a setting feature that locks the clutch feature in the engaged position and thereby prevents axial separation of the upper and lower capstans.

3. The surgical tool of claim 2 , wherein the setting feature comprises a pin extendable through an aperture defined in the upper capstan and engageable with a recess defined in the input shaft.

4. The surgical tool of claim 1 , wherein the at least one tooth comprises a plurality of ratchet teeth such that the clutch feature comprises a plurality of ratchet teeth defined on both capstans.

5. The surgical tool of claim 4 , wherein the plurality of ratchet teeth allow the upper and lower capstans to rotate relative to each other in opposite angular directions when the clutch feature is in the disengaged position, and

wherein the plurality of ratchet teeth are interlocked and couple the upper and lower capstans for simultaneous rotation in the either angular direction when the clutch feature is in the engaged position.

6. The surgical tool of claim 1 , wherein the clutch feature comprises matable geometric features defined on both capstans.

7. The surgical tool of claim 6 , wherein the matable geometric features comprise a drive protrusion defined on one of the upper or lower capstans, and a drive pocket defined on the other of the upper and lower capstans and sized to receive the drive protrusion.

8. The surgical tool of claim 1 , wherein rotating one of the upper or lower capstans relative to the other of the upper and lower capstans applies tension in one or both of the first and second drive cables.

9. The surgical tool of claim 1 , wherein rotating the upper and lower capstans in opposite angular directions applies tension in the first and second drive cables.

10. A drive assembly for a surgical tool, comprising:

an input shaft extending from a drive input rotatably mounted to a drive housing of the surgical tool;

upper and lower capstans mounted to the input shaft, the input shaft defining a rotational axis;

first and second drive cables coupled to the upper and lower capstans, respectively, and extendable to an end effector of the surgical tool; and

a clutch feature including a plurality of ratchet teeth on at least a first one of the upper and lower capstans, each of the ratchet teeth radially asymmetrically shaped about the rotational axis and arranged to selectively mate with at least one tooth on a second one of the upper and lower capstans to permit the upper and lower capstans to rotate with respect to one another in at least one angular direction about the rotational axis, the clutch feature movable between an engaged position, where rotation of the input shaft in either angular direction correspondingly rotates the upper and lower capstans in the same angular direction, and a disengaged position, where the upper and lower capstans are rotatable independent of each other in the at least one angular direction.

11. The drive assembly of claim 10 , further comprising a setting feature that locks the clutch feature in the engaged position and thereby prevents axial separation of the upper and lower capstans.

12. The drive assembly of claim 10 wherein the clutch feature comprises a plurality of ratchet teeth defined on both capstans.

13. The drive assembly of claim 10 , wherein the clutch feature comprises matable geometric features defined on both capstans.