The device has locking element (10) and protective sheath (11) which is connected to main portion (12) and has hollow space with cannula receiving opening. The sheath is pivotable to closed position in which cannula arrangable in main portion is protected in hollow space, and sheath is locked by locking element, and to open position. The locking element is rotatable about rotation axis parallel to pivot axis from rest position to latched position relative to sheath. The locking element is actuated to generate rotational movement, by pivoting movement of sheath.
