| 摘要 |
A safety syringe includes a protective sheath disposed within the interior of the body portion of the syringe. A needle extends from the body portion of the syringe when the syringe is in an armed condition. A biasing mechanism, such as a stretched coiled spring, is connected to the upper end of the needle and tends to draw the needle into the protective sheath. A releasable retainer mechanism engages a detent formed on the upper end of the needle to retain the needle in its extended position against the biasing force of the spring. After use, the releasable retainer mechanism is actuated either by the user or in response to movement of the syringe plunger, to release the detent formed on the needle and to cause the needle to be withdrawn into the protective sheath to prevent accidental contact with the sharpened end of the needle. In another embodiment of the invention, a telescoping sheath is held in a retracted condition adjacent the hub of the needle by a releasable retainer mechanism against the force of a biasing mechanism, such as a compressed coil spring. After use of the needle, the releasable retainer mechanism is actuated to effect extension of the telescoping sheath and to thereby enclose the needle to prevent accidental contact therewith.
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