A medical instrument has a cannula, a seal disposed in said cannula, said seal has an opening for guiding a shaft of another instrument through said seal in a sealed manner. An expansion device serves for expanding said opening in said seal. Said expansion device has an expansion cone comprising a plurality...http://www.google.com/patents/US8007471?utm_source=gb-gplus-sharePatent US8007471 - Medical instrument with laterally displaceable seal
