Surgical instrument comprising a firing drive including a selectable leverage mechanism

1. A surgical stapling instrument, comprising:

a handle comprising a frame;

a shaft extending from said handle;

an end effector extending from said shaft, comprising:

a first jaw;

a second jaw rotatable from an open position to a closed position; and

a staple cartridge comprising staples removably stored therein;

a firing drive, comprising:

a longitudinal rack comprising a longitudinal array of teeth;

a firing member coupled to said longitudinal rack, wherein said firing member comprises a first cam configured to engage said first jaw and a second cam configured to engage said second jaw during a closure stroke to move said second jaw into said closed position;

an electric motor comprising a rotatable output;

a controller in communication with said electric motor;

a reciprocatable pawl operably coupled with said rotatable output;

a pawl spring configured to bias said reciprocatable pawl into engagement with said longitudinal rack such that said reciprocatable pawl drives said longitudinal rack distally when said reciprocatable pawl is advanced distally, wherein said reciprocatable pawl slides relative to said longitudinal rack when said reciprocatable pawl is retracted proximally, wherein said controller is configured to advance said reciprocatable pawl distally through said closure stroke during a first actuation, wherein said controller is configured to advance said reciprocatable pawl distally through a first staple firing stroke during a second actuation, and wherein said controller is configured to advance said reciprocatable pawl distally through a second staple firing stroke during a third actuation;

a drive crank operably connecting said rotatable output and said pawl, wherein said drive crank is connected to said pawl at a pawl pin, and wherein said drive crank is selectively rotatably connected to said frame about one of:

a first pivot, wherein said drive crank defines a first lever arm having a first lever length between said first pivot and said pawl pin; and

a second pivot, wherein said drive crank defines a second lever arm having a second lever length between said second pivot and said pawl pin, wherein said second lever length is longer than said first lever length; and

an actuator in communication with said controller, wherein said actuator comprises a first pivot pin and a second pivot pin, wherein said actuator pivotably connects said drive crank to said frame with said first pivot pin when said actuator is in a first state, wherein said second pivot pin does not pivotably connect said drive crank to said frame when said actuator is in said first state, wherein said actuator pivotably connects said drive crank to said frame with said second pivot pin when said actuator is in a second state, wherein said first pivot pin does not pivotably connect said drive crank to said frame when said actuator is in said second state, and wherein said controller is configured to switch said actuator between said first state and said second state.

2. The surgical stapling instrument of claim 1 , wherein said firing drive further comprises a current sensor configured to detect the magnitude of the current through said electric motor, wherein said current sensor is in communication with said controller, and wherein said controller is configured to switch said actuator from said first state to said second state in-between said first staple firing stroke and said second staple firing stroke when the current through said electric motor exceeds a current threshold during said first staple firing stroke.

3. The surgical stapling instrument of claim 2 , wherein said controller is configured to not switch said actuator from said first state to said second state when the current through said electric motor does not exceed said current threshold during said first staple firing stroke.

4. The surgical stapling instrument of claim 1 , wherein said controller is configured to switch said actuator from said first state to said second state in-between said closure stroke and said first staple firing stroke.

5. The surgical stapling instrument of claim 1 , wherein said controller is configured to switch said actuator from said first state to said second state after said second staple firing stroke.

6. A surgical stapling instrument, comprising:

a handle comprising a frame;

a shaft extending from said handle;

an end effector extending from said shaft, comprising:

a first jaw;

a second jaw rotatable from an open position to a closed position; and

a staple cartridge comprising staples removably stored therein;

a firing drive, comprising:

a firing rack comprising a longitudinal array of teeth;

a firing member coupled to said firing rack, wherein said firing member comprises a first cam configured to engage said first jaw and a second cam configured to engage said second jaw during a closure stroke to move said second jaw into said closed position;

an electric motor comprising a rotatable output;

a controller in communication with said electric motor;

a reciprocatable pawl operably coupled with said rotatable output;

a pawl spring configured to bias said reciprocatable pawl into engagement with said firing rack such that said reciprocatable pawl drives said firing rack distally when said reciprocatable pawl is advanced distally by said electric motor, wherein said reciprocatable pawl slides relative to said firing rack when said reciprocatable pawl is retracted proximally by said electric motor, wherein said controller is configured to advance said reciprocatable pawl distally through said closure stroke during a first actuation, and wherein said controller is configured to advance said reciprocatable pawl distally through a staple firing stroke during a second actuation;

a drive crank operably connecting said rotatable output and said pawl, wherein said drive crank is connected to said pawl at a pawl pin, and wherein said drive crank is selectively rotatably connected to said frame about:

a first pivot, wherein said drive crank defines a first lever arm having a first lever length between said first pivot and said pawl pin; and

a second pivot, wherein said drive crank defines a second lever arm having a second lever length between said second pivot and said pawl pin, wherein said second lever length is longer than said first lever length; and

an actuator in communication with said controller, wherein said actuator comprises a first pivot connection and a second pivot connection, wherein said actuator pivotably connects said drive crank to said frame with said first pivot connection when said actuator is in a first state, wherein said second pivot connection does not pivotably connect said drive crank to said frame when said actuator is in said first state, wherein said actuator pivotably connects said drive crank to said frame with said second pivot connection when said actuator is in a second state, wherein said first pivot connection does not pivotably connect said drive crank to said frame when said actuator is in said second state, and wherein said controller is configured to switch said actuator between said first state and said second state.

7. The surgical stapling instrument of claim 6 , wherein said firing drive further comprises a current sensor configured to detect the magnitude of the current through said electric motor, wherein said current sensor is in communication with said controller, and wherein said controller is configured to switch said actuator from said first state to said second state after said staple firing stroke when the current through said electric motor exceeds a current threshold during said staple firing stroke.

8. The surgical stapling instrument of claim 7 , wherein said controller is configured to not switch said actuator from said first state to said second state when the current through said electric motor does not exceed said current threshold during said staple firing stroke.

9. The surgical stapling instrument of claim 6 , wherein said controller is configured to switch said actuator from said first state to said second state in-between said closure stroke and said staple firing stroke.

10. The surgical stapling instrument of claim 6 , wherein said controller is configured to switch said actuator from said first state to said second state after said staple firing stroke.