US Patent 8197459 Self-sealing medical fluid transfer device

Embodiments of the invention relate to a transfer device for a container whose interior is under negative pressure and which is closed by means of an elastic stopper. The device has a receiving cap and a piercing mandril for piercing the stopper. Relative to its direction of piercing, the piercing mandril is provided with a front piercing portion and with a rear sealing portion which is of greater diameter. In the position in which a bead of the container is inserted into the receiving cap, the sealing portion contacts the stopper. In this way, a tear in the stopper, which tear has been formed by eccentric application of the device onto the container, can be sealed off.