| 摘要 |
The barrel (10) of a hypodermic syringe has an open end connectable to a retractable injection needle unit via a mounting portion (28) of the needle unit which screws into a collar (26) at the open end of the barrel. Located internally within the barrel, adjacent its open end, is a restrictor (14) in the form of a resiliently deformable disc having a central opening (16). The disc is flat and has a diameter which is slightly greater than the internal diameter of the barrel so that, when the disc is pressed into the barrel, it takes up a slightly conical set. This facilitates securing the washer in position in the barrel. The opening (16) is sufficiently small so as ordinarily to retain liquid within the barrel by virtue of surface tension effects. This prevents liquid drawn into the barrel by means of a filling needle unit from "glugging" out of the barrel while the filling needle unit is being replaced by the injection needle unit. The opening (16) is also adapted to allow passage of the needle (30) and its mounting hub (32) into the barrel and hollow plunger upon actuation of the retractable needle unit at the completion of an injection stroke of the plunger.
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