| 摘要 |
A trocar having a cuttíng shaft with a cutting surface at a distal end. The cutting shaft<SUP>-</SUP>moves longitudinally with respect to an obturator such that in one position the cutting surface is in an exposed position suitable for application of a piercing force. Upon interruption of the piercing force to the cutting surface, the cutting surface- moves longitudinally with respect to the obturator such that the cutting surface is in a retracted position within the obturator. The trocar may include a first spring urging the cutting surface to an exposed position and a second spring urging the cutting. surface to a retracted position. The second spring has a slightly stronger biasing force than the first spring to bias the cutting surface to the retracted position. |
