| 摘要 |
A syringe comprises a generally-cylindrical, hollow barrel with a hollow nozzle at a distal end thereof. A plunger with an open channel is slidably mounted in the barrel. A needle holder with a needle mounted at one end thereof is arranged in the plunger channel, and movable between an advanced position, whereat the needle projects from a distal end of the nozzle for injection, and a retracted position, whereat the needle is enclosed within the barrel when the injection is complete. A spring retainer is arranged in the barrel. A spring is positioned within the spring retainer, urging the needle holder toward the retracted position. A latch latches the needle holder to the spring retainer thereby maintaining the spring in compression. The latch is releasable in response to the plunger moving to its fully advanced position, whereby the needle holder is released, allowing the spring to expand and thereby move the needle holder to the retracted position.
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