Surgical instrument with safety mechanism

1. A surgical instrument comprising:

a handle assembly including a firing mechanism;

an elongated body portion extending distally from the handle assembly;

a head portion disposed adjacent a distal end of the elongated body portion, the head portion including an anvil assembly and a shell assembly that are moveable between spaced and approximated positions relative to one another, the shell assembly supporting a plurality of staples, the firing mechanism being actuatable to eject the plurality of staples from the shell assembly; and

a safety mechanism disposed in mechanical cooperation with the handle assembly, the safety mechanism including a lever moveable from a first position preventing actuation of the firing mechanism to a second position permitting actuation of the firing mechanism, the lever being biased towards the first position, the safety mechanism including a latch retainer for releasably retaining the lever in the second position, wherein the latch retainer releases the lever from the second position in response to movement of the anvil and shell assemblies from the approximated position towards the spaced position relative to one another.

2. The surgical instrument of claim 1 , wherein the lever includes a latch configured to be releasably retained by the latch retainer to retain the lever in the second position.

3. The surgical instrument of claim 1 , wherein the safety mechanism includes a plate slidably disposed within the handle assembly, the plate defining an opening which receives a portion of the latch retainer therein.

4. The surgical instrument of claim 3 , wherein the latch retainer is biased proximally relative to the plate.

5. The surgical instrument of claim 4 , wherein the lever includes a latch disposed thereon, the latch retainer configured to engage the latch to retain the lever in the second position.

6. The surgical instrument of claim 5 , wherein the latch moves the latch retainer distally as the lever is moved from the first position to the second position.

7. The surgical instrument of claim 3 , wherein the plate is biased distally relative to the handle assembly.

8. The surgical instrument of claim 7 , further comprising an approximation mechanism for moving the anvil and shell assemblies between the spaced and approximated positions relative to one another, the approximation mechanism being engagable with the plate to move the plate proximally as the anvil and shell assemblies move relative to one another towards the approximated position.

9. The surgical instrument of claim 1 , wherein the handle assembly includes a firing trigger, the lever being pivotal from the first position in engagement with the firing trigger to the second position out of engagement with the firing trigger.

10. A surgical instrument comprising:

a handle assembly including a firing mechanism;

an elongated body portion extending distally from the handle assembly;

a head portion disposed adjacent a distal end of the elongated body portion, the head portion including an anvil assembly and a shell assembly, the head portion having a spaced position in which the anvil assembly is spaced from the shell assembly and an approximated position in which the anvil assembly is approximated to the shell assembly, the shell assembly supporting a plurality of staples, the firing mechanism being actuatable to eject the plurality of staples from the shell assembly; and

a safety mechanism disposed in mechanical cooperation with the handle assembly, the safety mechanism including a lever moveable from a first position preventing actuation of the firing mechanism to a second position permitting actuation of the firing mechanism, the lever being biased towards the first position, the safety mechanism including a latch retainer for releasably retaining the lever in the second position, wherein the latch retainer releases the lever from the second position in response to movement of the head portion towards the spaced position.

11. The surgical instrument of claim 10 , wherein the lever includes a latch configured to be releasably retained by the latch retainer to retain the lever in the second position.

12. The surgical instrument of claim 10 , wherein the safety mechanism includes a plate slidably disposed within the handle assembly, the plate defining an opening which receives a portion of the latch retainer therein.

13. The surgical instrument of claim 12 , wherein the latch retainer is biased proximally relative to the plate.

14. The surgical instrument of claim 13 , wherein the lever includes a latch disposed thereon, the latch retainer configured to engage the latch to retain the lever in the second position.

15. The surgical instrument of claim 14 , wherein the latch moves the latch retainer distally as the lever is moved from the first position to the second position.

16. The surgical instrument of claim 12 , wherein the plate is biased distally relative to the handle assembly.

17. The surgical instrument of claim 16 , further comprising an approximation mechanism for transitioning the head portion between the spaced and approximated positions, the approximation mechanism being engagable with the plate to move the plate proximally as the head portion moves towards the approximated position.

18. The surgical instrument of claim 10 , wherein the handle assembly includes a firing trigger, the lever being pivotal from the first position in engagement with the firing trigger to the second position out of engagement with the firing trigger.