A medical stapler adapted to bend a staple closed around an anvil into a generally loop-like shape. The stapler includes a mechanism for retracting the anvil from within the closed staple as a ram that closed the staple moves away from the anvil....http://www.google.co.uk/patents/US4527725?utm_source=gb-gplus-sharePatent US4527725 - Stapler with retractable anvil
