| 摘要 |
A hollow needle projects from the "forward" end of a syringe barrel or an adjacent auxiliary retraction barrel. After use to inject or withdraw liquid from a patient, the needle is released from the end of the barrel and retracted into the barrel. The barrel has an aperture big enough for the needle but too small for fingertips. The needle rides in a carrier block that slides in the barrel. Initially a manually releasable latch secures the block in the barrel against the forward end, with the sharp end of the needle protruding out through the aperture. The latch includes mutually interfering stop elements on the exterior of the block and interior of the barrel. After the injection or withdrawal of liquid, the person using the device withdraws the needle from the patient and manually triggers the latch by manipulating the plunger. A coiled spring drives the block rearward to retract the needle into the barrel. At the rear end of the barrel a stop halts the carrier block and needle to safely confine them. If no auxiliary barrel is present, the plunger is relieved to allow retention of the needle in the syringe, while the plunger is fully forward, to minimize bulk after retraction. In another form of the invention the front end of the plunger engages the rear end of the needle or carrier; pulling the plunger rearward pulls the needle into the syringe.
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