A safety shielded, reusable trocar consisting of a trocar cannula subassembly, a safety shield control mechanism, and a separate obturator subassembly. The trocar cannula subassembly includes an outer cannula attached to a main housing having a central bore in which a spring biased, inner cannula...http://www.google.fr/patents/US5697947?utm_source=gb-gplus-shareBrevet US5697947 - Trocar obturator including a removable knife
