Knife lockout mechanisms for surgical instrument

1. A cartridge assembly for use with a surgical stapling instrument, the cartridge assembly comprising:

a channel including a protrusion thereon;

a cover configured for mechanical engagement with the channel, the cover including a blocking member and including a surface defining a plane, at least a portion of the blocking member being configured to move away from the plane upon contact with the protrusion;

a staple cartridge configured for mechanical engagement with the cover;

a knife configured for translation with respect to the cover; and

wherein the blocking member is configured to substantially prevent distal translation of the knife after the knife has been translated proximally past a predetermined position.

2. The cartridge assembly of claim 1 , further comprising a sled configured for translation with respect to the cover.

3. The cartridge assembly of claim 1 , wherein the blocking member includes a flexible finger.

4. The cartridge assembly of claim 1 , wherein the blocking member is configured to allow the knife to travel proximally therepast when the blocking member is displaced from the plane.

5. The cartridge assembly of claim 1 , wherein the blocking member is biased in a position where the blocking member is substantially parallel with the plane defined by the surface of the cover.

6. The cartridge assembly of claim 1 , wherein the blocking member is substantially parallel with the plane defined by the surface of the cover prior to engagement between the channel and the cover.

7. A surgical stapling instrument, comprising:

a frame;

an elongate portion extending distally from the frame and defining a longitudinal axis;

a cartridge assembly disposed in mechanical cooperation with the elongate portion, the cartridge assembly including:

a surface defining a plane;

a protrusion;

a blocking member, at least a portion of the blocking member being configured to move away from the plane upon engagement with the protrusion;

a knife configured for translation with respect to the surface; and

wherein the blocking member is configured to substantially prevent distal translation of the knife after the knife has been translated proximally past a predetermined position.

8. The surgical stapling instrument of claim 7 , further comprising a staple cartridge disposed in mechanical cooperation with the cartridge assembly, the staple cartridge including a plurality of spaced apart staples therein.

9. The surgical stapling instrument of claim 7 , further comprising a movable handle disposed in mechanical cooperation with the frame, wherein at least a partial actuation of the movable handle translates the knife.

10. The surgical stapling instrument of claim 9 , wherein at least a partial actuation of the movable handle in a first direction translates the knife distally and wherein at least a partial actuation of the movable handle in a second direction translates the knife proximally past the predetermined position.

11. The surgical stapling instrument of claim 7 , further comprising a sled configured for translation with respect to the cover.

12. The surgical stapling instrument of claim 7 , wherein the blocking member includes a flexible finger.

13. The surgical stapling instrument of claim 7 , wherein the blocking member is configured to allow the knife to travel proximally there past when the blocking member is displaced from the plane.

14. The surgical stapling instrument of claim 7 , wherein the blocking member is biased in a position where the blocking member is substantially parallel with the plane defined by the surface of the cover.

15. The surgical stapling instrument of claim 7 , wherein the blocking member is substantially parallel with the plane defined by the surface of the cover prior to engagement between the channel and the cover.

16. The surgical stapling instrument of claim 7 , further comprising a firing rod extending through the elongate portion.

17. The surgical stapling instrument of claim 16 , wherein the knife and the firing rod form a knife/firing rod connection.

18. The surgical stapling instrument of claim 17 , wherein the cartridge assembly is a replaceable cartridge assembly, the knife being removably connectable to the firing rod.