Surgical instrument with articulating tool assembly

1. A surgical instrument comprising:

a handle portion;

a body portion extending distally from the handle portion and defining a first longitudinal axis;

an articulating tool assembly defining a second longitudinal axis and having a proximal end, the articulating tool assembly disposed at a distal end of the body portion and being movable from a first position in which the second longitudinal axis is substantially aligned with the first longitudinal axis to at least a second position in which the second longitudinal axis is disposed at an angle with respect to the first longitudinal axis; and

an articulation mechanism including:

a housing block configured to receive an articulation spindle having an interface member, the articulation spindle rotatably housed within the housing block, wherein the articulation spindle defines a plurality of notches, the plurality of notches configured to mechanically interface with a plunger biased to engage the articulation spindle;

an articulation link for articulating the tool assembly, the articulation link having a slit at a proximal end operatively connected to the interface member; and

an articulation knob coupled to the articulation spindle for rotating the interface member, wherein rotational motion of the articulation knob is translated into axial motion of the articulation link thereby articulating the articulating tool assembly.

2. The surgical instrument according to claim 1 , wherein each of the plurality of notches indexes a rotational position of the articulation spindle with an articulation position of the articulating tool assembly.

3. The surgical instrument according to claim 2 , wherein at least one of the notches corresponds with a neutral axial plane position of the articulating tool assembly.

4. The surgical instrument according to claim 1 , wherein the housing block and the articulation spindle are is adapted to limit the a rotational range of the articulation spindle.

5. The surgical instrument according to claim 4 , wherein the housing block has a guide channel with a substantially arcuate shape, the guide channel receiving a member on the articulation spindle.

6. The surgical instrument according to claim 5 , wherein length of the guide channel corresponds to maximum desired articulation of the articulating tool tip.

7. The surgical instrument according to claim 1 , wherein the articulation spindle is configured to rotate in predetermined increments.

8. The surgical instrument according to claim 7 , wherein at least two of the plurality of notches correspond to maximum articulating positions of the articulating tool assembly.

9. The surgical instrument according to claim 1 wherein the articulating tool assembly is part of a disposable loading unit.

10. The surgical instrument according to claim 1 , wherein the articulating tool assembly includes a cartridge assembly and an anvil assembly.

11. The surgical instrument according to claim 1 , further comprising a sensing mechanism positioned within the body portion and operatively associated with the articulation mechanism, the sensing mechanism including a sensing cap for sensing the type of disposable loading unit engaged with the body portion.

12. The surgical instrument according to claim 11 , wherein the sensing cap is positioned within the elongated body and being movable to a first position in response to engagement of a non-articulating disposable loading unit with the body portion to a second position in response to engagement of an articulating disposable unit with the body portion.

13. The surgical instrument according to claim 12 , wherein in the first position, the sensing mechanism is operatively engaged with the articulating mechanism to prevent movement of the articulation knob.