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Self-aspirating hypodermic syringe and self-aspirating assembly therefor

  • US 4,333,456 A
  • Filed: 02/09/1981
  • Issued: 06/08/1982
  • Est. Priority Date: 02/09/1981
  • Status: Expired due to Fees
First Claim
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1. A self-aspirating hypodermic syringe of the type used in combination with a cartridge ampoule which is sealed at its upper end by a slidable piston and at its lower end by a pierceable membrane and which contains an injectable fluid therein, the syringe having a double ended needle attached thereto for communication with the cartridge ampoule contents via the pierceable membrane, said syringe comprising in combination:

  • (A) a syringe holder comprising a head, a barrel attached thereto for receiving said cartridge ampoule and provided at its lower end with a double ended needle, and a generally cylindrical holding means within said head which is adapted to securely hold said cartridge ampoule within said barrel; and

    (B) a self-aspirating assembly slidable within the bore of said holding means comprising a pair of plungers, one slidable within the other, said plungers being biased one against the other, the inner plunger being adapted for positive interengagement with said slidable piston of said cartridge ampoule and the outer plunger being adapted for positive, selective and reversible locking with said holding means thereby to immobilize said outer plunger against axial movement relative to said syringe holder and cartridge ampoule,whereby upon alternate exertion of downward pressure upon said inner plunger while said outer plunger is locked and release of said downward pressure, the said bias of said inner plunger against said outer plunger creates aspirating conditions within said cartridge ampoule and whereby upon exertion of downward pressure upon said inner plunger while said outer plunger is unlocked, said inner and outer plungers are freely slidable within the bore of said holding means.

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