A sheath is provided with a stationary deflector disposed on the path of the slider so that contact between the slider and the deflector causes the slider to be inclined and consequently causes the needle to be inclined inside the sheath. A return mechanism is provided so as to push the inclined slider back in the opposite direction so that the point of the inclined need is prevented from moving. This disposition ensures that the needle cannot escape from the sheath after it has been used.
