| 摘要 |
A single use retractable medical device dispenses fluids from a separable carpule. A retraction mechanism having a spring loaded needle holder with a double ended needle is mounted the in front of a housing by means of a push ring slidingly mounted on a widened portion of the needle holder. An outer edge of the push ring grips or is restrained by the inner wall surface of the housing to hold the needle holder in place. A carpule positioned through an opening in back of the housing is progressively received by a plunger which drives a separable two-part piston to unload medicine from the carpule through the needle. At the end of an injection, the plunger is depressed further to remove the push ring in cooperation with the carpule thereby freeing the needle holder for retraction through the front opening of the carpule. As the needle is retracted into the housing from one end, the edge of the thumb cap of the plunger disappears into an opening at the opposite end of the housing. An alternative embodiment has a thumb ring instead of a thumb cap. The alternate version has a dish shaped push ring with forwardly angled edges which tend to bind against the housing when pushed from the center by the front of the carpule. The edge of the push ring is easily released by an outer wall portion of the plunger which unlocks the dished edges from a stop structure on the inner wall of the housing as the plunger is moved forward to retract after an injection is made. |
