| 摘要 |
In a syringe with a hollow cylindrical barrel with one closed end, a plunger having a length longer than the barrel mounted in the barrel for reciprocation, a handle on the distal end of the plunger extending from the barrel and a piston mounted on the opposite end of the plunger in the barrel and a hypodermic needle mounted in the closed end of the barrel being in communication with the interior of the barrel, the improvement of including a hollow tapered section in the barrel adjacent to its closed end, which tapered section in cooperation with the piston end of the plunger is operable to disable the syringe as the piston commences traversing this tapered portion of the barrel. A desired embodiment has the tapered section or portion formed by a separate sleeve slidably mounted in the barrel with the hypodermic needle mounted in this sleeve with means to engage the sleeve whereby withdrawing the plunger from the barrel after its piston end has entered this tapered section will pull the sleeve and the attached needle into the barrel thereby preventing persons from thereafter being "pricked" by the sharp end of the "used" needle.
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