Surgical stapling instrument with a variable staple forming system

1. A surgical instrument, comprising:

a handle assembly; and

an elongated shaft assembly operably coupled to said handle assembly, said elongated shaft assembly having a distal end couplable to an end effector that supports a staple cartridge that has a plurality of unformed staples therein and an anvil that is movable from an open position wherein a staple forming surface of the anvil is spaced from the staple cartridge into compressive engagement with the staple cartridge and into forming engagement with the staples therein, wherein a distance that the staple forming surface of the anvil travels into forming contact with the staples in the staple cartridge is dependent upon a magnitude of firing force applied thereto by a firing system that is at least partially supported in said elongated shaft assembly and said handle assembly and operated by a firing trigger movably supported on the handle assembly such that said magnitude of firing force applied to said movable anvil is dependent upon a degree in which the firing trigger has been actuated on the handle assembly;

wherein said elongated shaft assembly further comprises an elongated spine member operably attached to said handle assembly and protruding therefrom, said elongated spine member having a distal end that is removably couplable to the end effector and wherein said firing system comprises a firing tube movably supported on said spine member and interfacing with said firing trigger such that said actuation of said firing trigger causes said firing tube to move distally on said spine member;

wherein a distal end of said firing tube is configured to engage the anvil such that said magnitude of said firing force is increased as said distal end of said firing tube moves distally into engagement with said anvil;

wherein the anvil has an anvil ramp portion and wherein said magnitude of firing force increases as the distal end of the firing tube advances distally in compressing engagement with said anvil ramp portion; and

wherein said anvil ramp portion has a proximal ramp surface and a clamping ramp surface that is oriented at a clamping angle relative to said proximal ramp surface such that as said distal end of said firing tube engages said clamping ramp surface, said anvil is driven into a clamping orientation wherein tissue may be clamped between the anvil and the staple cartridge without forming any of the staples in the staple cartridge.

2. A surgical instrument comprising:

a handle assembly; and

an elongated shaft assembly operably coupled to said handle assembly, said elongated shaft assembly having a distal end couplable to an end effector that supports a staple cartridge that has a plurality of unformed staples therein and an anvil that is movable from an open position wherein a staple forming surface of the anvil is spaced from the staple cartridge into compressive engagement with the staple cartridge and into forming engagement with the staples therein, wherein a distance that the staple forming surface of the anvil travels into forming contact with the staples in the staple cartridge is dependent upon a magnitude of firing force applied thereto by a firing system that is at least partially supported in said elongated shaft assembly and said handle assembly and operated by a firing trigger movably supported on the handle assembly such that said magnitude of firing force applied to said movable anvil is dependent upon a degree in which the firing trigger has been actuated on the handle assembly;

wherein said elongated shaft assembly further comprises an elongated spine member operably attached to said handle assembly and protruding therefrom, said elongated spine member having a distal end that is removably couplable to the end effector and wherein said firing system comprises a firing tube movably supported on said spine member and interfacing with said firing trigger such that said actuation of said firing trigger causes said firing tube to move distally on said spine member;

wherein a distal end of said firing tube is configured to engage the anvil such that said magnitude of said firing force is increased as said distal end of said firing tube moves distally into engagement with said anvil;

wherein the anvil has an anvil ramp portion and wherein said magnitude of firing force increases as the distal end of the firing tube advances distally in compressing engagement with said anvil ramp portion; and

wherein said anvil ramp portion further has a staple forming ramp surface thereon that is at a forming angle that differs from said clamping angle and wherein when said distal end of said firing tube engages said staple forming ramp surface, said staple forming portion of said anvil is driven into forming contact with the staples in the staple cartridge.

3. The surgical instrument of claim 1 wherein said firing trigger is pivotally supported by said handle assembly and is selectively pivotable relative to a pistol grip portion thereof.

4. The surgical instrument of claim 1 wherein the anvil is biased to the open position prior to activation of said firing trigger.

5. The surgical instrument of claim 1 wherein said elongated shaft assembly operably supports a cutting member therein that is independently actuatable from said firing system.

6. The surgical instrument of claim 1 wherein a degree of staple formation attained by each staple in the staple cartridge is dependent upon the magnitude of firing force applied to the anvil by said firing system.