Patent ID: 7300422

Claim:
A protective sheath for an injection cannula arranged on a cannula-holding support, the sheath being fittable on a syringe and comprising proximal and distal ends, the sheath forming: a retracted use position from which the cannula holder can be displaced, relative to the sheath, to an ejection position for exposing the cannula from the distal end of the sheath; a retracted post-use position into which the cannula holder may be displaced from the retracted use position, relative to the sheath, for permanently locking the cannula in a retracted state; a retracted pre-use position from which the cannula holder can be displaced to the retracted use position, relative to the sheath, the retracted pre-use position including first and second transversely spaced sections, the cannula holder being displaceable, to the retracted use position from a distal end of the second section, a distal end of the first section configured for locking the cannula holder against displacement to the second section in distal and lateral directions when the cannula holder is disposed adjacent the distal end of the first section, the first and second sections communicating with one another adjacent their proximal ends, requiring the cannula holder to be moved proximally relative to the sheath to become unlocked from the first section; primary transition means enabling the cannula holder to be brought into the retracted pre-use position RPU; secondary transition means enabling the cannula holder to be moved from the retracted pre-use position RPU to the retracted use position RU; and tertiary transition means enabling the cannula holder to be brought from the retracted use position RU to the retracted post-use position RAU; wherein at least one of the primary and secondary tertiary transition means is formed at least by a transition portion having, in longitudinal section, a recess made in the inner face of said sheath, said single or said plural transition means having, at each of its or of their ends, a hole and, between these holes, an inclined flat section progressively taking the depth p of said recess toward a zero, or even negative, value.