Compound screw knife drive for electrosurgical shears

1. A surgical instrument comprising:

(a) an end effector, wherein the end effector comprises:

(i) a first jaw,

(ii) a second jaw pivotably coupled with the first jaw, wherein the second jaw is operable to move between an open position and a closed position,

(iii) a knife configured to actuate between a pre-fired position and a fired position, and

(iv) an electrode assembly configured to apply RF energy to tissue;

(b) a handle assembly, wherein the handle assembly comprises:

(i) a housing associated with the first jaw,

(ii) an arm associated with the second jaw, wherein the arm is configured to pivot the second jaw between the open position and the closed position; and

(c) a knife drive assembly comprising:

(i) an input assembly,

(ii) an output assembly coupled with the knife, and

(iii) a threaded member rotatably disposed within the housing, wherein the threaded member comprises:

(A) a first threaded portion associated with the input assembly, wherein the first threaded portion comprises a first pitch extending in a first pitch orientation, and

(B) a second threaded portion associated with the output assembly, wherein the second threaded portion comprises a second pitch extending in a second pitch orientation, wherein the second pitch orientation is opposite to the first pitch orientation,

wherein the input assembly is configured to travel a first proximal distance to in order to rotate the threaded member, wherein the threaded member is configured to rotate to drive the output assembly a first distal distance to actuate the knife from the pre-fired position toward the fired position.

2. The surgical instrument of claim 1 , wherein the input assembly comprises an input projection housed within the first threaded portion, wherein the input projection is configured to drive rotation of the threaded member in response to linear translation of the input projection.

3. The surgical instrument of claim 2 , wherein the output assembly comprises an output projection housed within the second threaded portion, wherein the threaded member is configured to drive linear translation of the output projection in response to rotation of the threaded member.

4. The surgical instrument of claim 3 , wherein the first threaded portion extends into a longitudinally extending dwell.

5. The surgical instrument of claim 4 , wherein the input projection is configured to translate within the longitudinally extending dwell without rotating the threaded member.

6. The surgical instrument of claim 1 , wherein the arm comprises a resilient member configured to transition between a relaxed position and a flexed position when the jaws are in the closed configuration.

7. The surgical instrument of claim 6 , further comprising a lockout member configured to actuate between a locked configuration and an unlocked configuration.

8. The surgical instrument of claim 7 , wherein the lockout arm is configured to drive the lockout member from the locked configuration into the unlocked configuration in response to the arm transitioning from the relaxed position to the flexed position.

9. The surgical instrument of claim 8 , wherein the threaded member comprises an angular locking body.

10. The surgical instrument of claim 9 , wherein the angular locking body is configured to abut against the lockout member while in the locked configuration to prevent actuation of the knife from the pre-fired position to the fired position.

11. The surgical instrument of claim 1 , wherein the output assembly defines a cutout, wherein the knife further comprises a proximal body housed within the cutout of the output assembly.

12. The surgical instrument of claim 1 , wherein the first distal distance is greater than the first proximal distance.

13. The surgical instrument of claim 1 , wherein the input assembly comprises a first sliding member associated with a trigger and a second sliding member associated with the threaded member, where the second sliding member is distally biased.

14. The surgical instrument of claim 13 , wherein the first sliding member is configured to proximally drive the second sliding member to a pre-determined proximal position.

15. The surgical instrument of claim 14 , wherein the first sliding member and the second sliding member are configured to be disassociated from each other when the second sliding member reaches the pre-determined proximal position.

16. A surgical instrument comprising:

(a) an end effector, wherein the end effector comprises:

(i) a first jaw,

(ii) a second jaw pivotably coupled with the first jaw, wherein the second jaw is operable to move between an open position and a closed position,

(iii) a knife configured to actuate between a pre-fired position and a fired position, and

(iv) an electrode assembly configured to apply RF energy to tissue;

(b) a handle assembly, wherein the handle assembly comprises:

(i) a housing associated with the first jaw,

(ii) an arm associated with the second jaw, wherein the arm is pivotably coupled with the housing, wherein the arm is configured to pivot the second jaw between the open configuration and the closed configuration, wherein the arm is configured to transition between a relaxed position and a flexed position while the second jaw is in the closed configuration; and

(c) a knife drive assembly comprising:

(i) an input assembly,

(ii) an output assembly coupled with the knife, and

(iii) a threaded member rotatably disposed within the housing, wherein the threaded member comprises:

(A) a first threaded portion associated with the input assembly, wherein the first threaded portion extends in a first helical orientation, and

(B) a second threaded portion associated with the output assembly, wherein the second threaded portion extends in a second helical orientation, wherein the second helical orientation is opposite to the first helical orientation,

wherein the input assembly is configured to travel a first proximal distance to in order to rotate the threaded member, wherein the threaded member is configured to configured rotate to drive the output assembly a first distal distance to actuate the knife from the pre-fired position toward the fired position.

17. The surgical instrument of claim 16 , wherein the arm further comprises a resilient member configured to transition between a relaxed position and a flexed position while the second jaw is in the closed configuration.

18. The surgical instrument of claim 17 , further comprising a lockout assembly configured to transition between an unlocked position and a locked position in response to the resilient arm transition between the relaxed position and the flexed position.

19. A surgical instrument comprising:

(a) a housing extending distally into a first jaw;

(b) an arm pivotably coupled with the housing, wherein the arm extends distally into a second jaw, wherein arm is operable to drive the second jaw between an open position and a closed position;

(c) an electrode assembly associated with the first jaw and the second jaw, wherein the electrode assembly is configured to apply RF energy to tissue;

(d) a knife configured to actuate within the first jaw and the second jaw between a pre-fired position and a fired position;

(e) a trigger assembly movably coupled with the housing, and

(f) a knife actuation assembly configured to actuate the knife between the pre-fired position and the fired position, wherein the knife actuation assembly comprises:

(i) a threaded body rotatably disposed within the housing, wherein the threaded body defines an input threading, and an output threading,

(ii) an output member slidably coupled with the threaded body, wherein the output member comprises an output projection housed within the output threading, and

(iii) an input member slidably coupled with the threaded body, wherein the input member comprises an input projection associated with the input threading, wherein the trigger assembly is configured to drive the input projection between a first position, and a second position relative to the threaded body, wherein the input projection is housed within the input threading between the first position and the second position such that the knife actuation assembly is configured to drive the knife between the pre-fired position and the fired position.

20. The surgical instrument of claim 19 , wherein the threaded body further defines a longitudinal dwell extending into the input threading, wherein the trigger is configured to drive the input projection between the second position and a third position relative to the threaded body, wherein the input projection is housed within the longitudinal dwell between the second position and the third position such that the knife actuation assembly does not drive the knife in response to movement of the trigger assembly, wherein the input member is configured to decouple from the trigger assembly upon reaching the third position.