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Syringe hypodermic needle

  • US 4,840,616 A
  • Filed: 02/29/1988
  • Issued: 06/20/1989
  • Est. Priority Date: 02/27/1987
  • Status: Expired
First Claim
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1. A single use disposable medical syringe comprising a syringe body adapted at one end to receive a hypodermic needle, a plunger located within said syringe body and passing through an end plate attached to other end of said syringe body and characterised in that:

  • said plunger includes a plunger head forming at any time a seal with an interior surface of said syringe body, and a plunger shaft including at least a first and second longitudinally extending spline, said first spline including teeth adapted to co-act with a first pawl and said second spline including teeth adapted to co-act with a second pawl, said splines further including circumjacent and corresponding first and second recesses;

    said end plate having an aperture to locate said plunger shaft, said aperture having three or more channels each adapted to receive one or other said splines and two of said channels being provided respectively with said first and second pawls;

    said recesses allowing free rotation of said plunger within said end plate aperture such that when said first pawl allows withdrawal only of said plunger whereupon predetermined free rotation of said plunger engages said second pawl which allows insertion only of said plunger.

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