Surgical stapling device with firing lockout mechanism

A surgical stapling device comprising:

• an elongate body having a proximal portion and a distal portion;
• a tool assembly supported on the distal portion of the elongate body, the tool assembly including:
• a cartridge assembly including a channel member and a staple cartridge, the staple cartridge removably received within the channel member and including a cartridge body, staples, and an actuation sled assembly including an actuation sled, the actuation sled assembly movable through the cartridge body between retracted and advanced positions;
• an anvil including an anvil body having a staple forming surface defining staple forming pockets and a longitudinal slot, the anvil body coupled to the cartridge assembly such that the tool assembly is movable between open and clamped positions;
• and
• a lock mechanism supported on the anvil, the lock mechanism including a lock member that is rotatable about a pivot axis between a locked position and an unlocked position in response to movement of the tool assembly from the open position to the clamped position, the pivot axis extending through the cartridge assembly and the anvil when the tool assembly is in the clamped position;
• and
• a drive assembly including a clamp member, the clamp member movable in relation to the tool assembly between retracted and advanced positions, wherein the lock member is positioned to prevent movement of the clamp member from the retracted position to the advanced position in the locked position.