| 摘要 |
A single use retractable syringe has three main parts which are coaxially arranged. An outer barrel is fitted with a slidable plunger and an elongated needle rod is carried within the plunger and biased for retraction. In the unretracted position of the needle rod, an injection needle is extended from the front of the barrel. The needle rod is held in the unretracted position by a resilient ring member frictionally mounted on one larger part of the needle rod just behind a reduced size front part of the needle rod. The needle communicates with a variable fluid chamber behind the resilient ring member below the front end of the plunger. After an injection, further depression of the plunger pushes the resilient ring member forward and off the larger diameter portion of the needle rod to release the needle rod which is biased to retract along with the needle into the plunger. The needle rod may be biased in the retraction direction by a spring or by a vacuum in the plunger behind the needle rod. The device is simple in operation and especially suited for mass production and robotic assembly. Retraction is reliable and permanent.
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