Surgical instrument steering input device

1. A surgical instrument comprising:

a distal movable component;

a proximal drive assembly comprising a drive shaft, a capstan, and a plurality of splines, the drive shaft comprising a rod, a tapered projection, and a support stem, the rod comprising a drive input end and a second end opposite the drive input end, the tapered projection and the support stem extending from the second end of the rod, the capstan comprising an opening, the tapered projection and the support stem of the drive shaft being received in the opening of the capstan, the opening of the capstan comprising a tapered bore, and the plurality of splines engaging the tapered projection of the drive shaft with the tapered bore of the capstan;

a first cable portion extending between the distal movable component and the drive shaft; and

a second cable portion extending between the distal movable component and the capstan.

2. The surgical instrument of claim 1 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan.

3. The surgical instrument of claim 1 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan;

the snap-fit element comprises an elastic portion and a lip on the elastic portion; and

the lip of the snap-fit element is beveled to facilitate engagement with the capstan, disengagement from the capstan, or both engagement with and disengagement from the capstan.

4. The surgical instrument of claim 1 , wherein:

the tapered bore of the capstan comprises the plurality of splines;

the tapered projection of the drive shaft comprises a conical surface; and

the plurality of splines engage the conical surface of the drive shaft.

5. The surgical instrument of claim 4 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan.

6. The surgical instrument of claim 4 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan;

the snap-fit element comprises an elastic portion and a lip on the elastic portion; and

the lip of the snap-fit element is beveled to facilitate engagement with the capstan, disengagement from the capstan, or both engagement with and disengagement from the capstan.

7. The surgical instrument of claim 1 , wherein:

the tapered projection of the drive shaft comprises the plurality of splines;

the tapered bore of the capstan comprises a conical surface; and

the plurality of splines engage the conical surface of the capstan.

8. The surgical instrument of claim 7 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan.

9. The surgical instrument of claim 7 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan;

the snap-fit element comprises an elastic portion and a lip on the elastic portion; and

the lip of the snap-fit element is beveled to facilitate engagement with the capstan, disengagement from the capstan, or both engagement with and disengagement from the capstan.

10. The surgical instrument of claim 1 , wherein:

the tapered projection of the drive shaft comprises a first portion of the plurality of splines;

the tapered bore of the capstan comprises a second portion of the plurality of splines; and

the first and second portions of the plurality of splines are meshed.

11. The surgical instrument of claim 10 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan.

12. The surgical instrument of claim 10 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan;

the snap-fit element comprises an elastic portion and a lip on the elastic portion; and

the lip of the snap-fit element is beveled to facilitate engagement with the capstan, disengagement from the capstan, or both engagement with and disengagement from the capstan.

13. The surgical instrument of claim 1 , wherein:

the tapered projection of the drive shaft comprises a first portion of the plurality of splines, and upper edges of the first portion of splines are chamfered;

the tapered bore of the capstan comprises a second portion of the plurality of splines, and lower edges of the second portion of the plurality of splines are chamfered; and

the first and second portions of the plurality of splines are meshed.

14. The surgical instrument of claim 13 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan.

15. The surgical instrument of claim 13 , wherein:

the drive shaft comprises a snap-fit element engaged with the capstan;

the snap-fit element comprises an elastic portion and a lip on the elastic portion; and

the lip of the snap-fit element is beveled to facilitate engagement with the capstan, disengagement from the capstan, or both engagement with and disengagement from the capstan.

16. A surgical instrument comprising:

a distal movable component, a proximal drive assembly, a first cable portion, and a second cable portion;

wherein the proximal drive assembly comprises a drive shaft, a capstan, and a snap-fit element coupling the drive shaft and the capstan together;

wherein the drive shaft comprises a rod, a tapered projection, and a support stem, and;

wherein the rod comprises a drive input end and a second end opposite the drive input end;

wherein the tapered projection and the support stem extend from the second end of the rod;

wherein the tapered projection comprises a first plurality of splines;

wherein the capstan comprises a tapered bore, and the tapered bore comprises a second plurality of splines;

wherein the second plurality of splines is engaged as a keyed interlocking mesh with the first plurality of splines;

wherein the snap-fit element comprises an elastic portion and a lip on the elastic portion, the lip being beveled to facilitate releasable engagement of the first and second pluralities of splines when engaged;

wherein the first cable portion extends between the distal movable component and the drive shaft; and

wherein the second cable portion extends between the distal movable component and the capstan.

17. The surgical instrument of claim 16 :

wherein the tapered projection comprises a proximal end, a distal end, an outer surface, and a length defined between the proximal and distal ends;

wherein the tapered bore comprises an inner surface;

wherein the first plurality of splines is diametrically spaced along the outer surface of the tapered projection;

wherein each spline of the first plurality of splines spans the length of the tapered projection; and

wherein the second plurality of splines is diametrically spaced along the inner surface of the tapered bore.

18. The surgical instrument of claim 17 :

wherein the elastic portion of the snap-fit element comprises a stem extending axially from a flange of the tapered projection; and

wherein the lip of the snap-fit element is at a distal end of the stem.

19. The surgical instrument of claim 17 :

wherein the lip comprises an engagement surface and a disengagement surface;

wherein the engagement surface of the lip is beveled to slide against an undercut ridge of the tapered bore in response to an axial force applied to move the drive shaft and capstan together; and

wherein the disengagement surface of the lip is beveled to slide against the undercut ridge of the tapered bore in response to an axial force applied to move the drive shaft and the capstan apart.

20. The surgical instrument of claim 16 :

wherein the tapered projection comprises a thermoplastic structure overmolded around the support stem.