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Disposable safety syringe

  • US 5,112,316 A
  • Filed: 06/23/1989
  • Issued: 05/12/1992
  • Est. Priority Date: 06/23/1988
  • Status: Expired due to Fees
First Claim
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1. A disposable safety syringe, containing a tubular syringe body with a needle-holder head integral to one of its axial end zones, wherefrom there axially extends an empty needle communicating, by means of a mounting bushing integral with said needle, with the cavity of the syringe body for the purpose of injecting liquids contained in said cavity, and further comprising a plunger, housed in said syringe body in a tight and axially-slidable fashion, and which can be slide-driven by means of a shaft, extending with one of its end zones outside the syringe body through an aperture in said body provided at its axial end zone opposite to the needle holder head, and also means for inseparable coupling between the empty needle and the above-mentioned plunger, by means of the said mounting bushing, achieving said coupling at the end of the stage for injecting the liquid contained in the syringe body, and means for automatically returning the plunger to a position retracted in an axial direction inside the syringe body, which means consist of a spring which is loaded by depression of the plunger during the stage for injecting the liquid contained in the syringe body and acts upon cessation of the manual action exerted on the plunger upon completion of the injection of liquid contained in the syringe body, as well as means for retaining the empty needle in the use position, which means are separate from and disengageably bind the bushing to the needle-holder head, in which the bushing is itself inserted in such a way that it can be retracted in an axial direction, and means of disengaging these retaining means, which disengaging means are integral with the plunger and are led thereby to contact the retaining means at the end of the stage for injecting the liquid contained in the syringe body, and disengage the bushing for mounting the empty needle to retaining means, characterized in that the above-mentioned means for automatically returning the plunger to a retracted position are separate from and independent of the empty needle and its mounting bushing before and during the stage for injecting the liquid contained in the syringe body and are connected with the empty needle and its mounting bushing, through the plunger and the means for inseparable coupling between the empty needle and the plunger, upon completion the stage for injecting the liquid contained in the syringe body,thereby ensuring that the bushing for mounting the empty needle can be retracted, in an axial direction, from the needle-holder head upon completion of the stage for injecting the liquid contained in the syringe body, substantially in step with the action for inseparable coupling between the plunger and the bushing for mounting the empty needle, in such a way that, upon completion of the stage for injecting the liquid, the plunger is automatically retracted, by the said automatic plunger return means, into the syringe body and, in a manner integral to and inseparable from the plunger, the empty needle and its mounting bushing are also automatically retracted into a safety position inside the syringe body, irrespective of the operator'"'"'s intention.

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