| 摘要 |
A safety cover, which securably and reliably prevents the readvancement of the tip of a cannula once it has been retracted thereinto, is designed having an elongate body which includes an axial channel having elements which displace and block linear passage of the cannula once it has been retracted. In a first embodiment the displacing elements are inwardly and rearwardly extending bristles which provide for unidirectional motion of the cannula relative to the safety cover, thereby locking the cannula once it has been retracted. In a second embodiment, the displacing element is the axial channel itself which has a curvate bias and distorts into a non-linear path once the cannula is retracted. In a third embodiment, the displacing element is a spring plate which, when compressed permits the cannula to pass through, but once the cannula has been retracted, expands to prevent the tip from being readvanced.
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