A trocar has an elongated body with a frustro-conical end which terminates in a blunt tip. A plurality of blades are radially attached to a blade housing connected to the trocar body. In one embodiment the blade housing moves toward the trocar body in response to a force causing the blades to extend...http://www.google.de/patents/US5372588?utm_source=gb-gplus-sharePatent US5372588 - Trocar having blunt tip
