Method and device to protect syringes and similar medical instruments

A needle-stick safety syringe, comprising:

• an inner tubular body, plunger, and needle extending from a distal end of said inner tubular body;
• an outer tubular housing concentric with and sized to fit around at least a portion of said inner tubular body and to slide freely thereon;
• a spring disposed within said outer tubular housing to bias apart said inner tubular body and said outer tubular housing;
• a recess defining an annulus within an interior wall surface of said outer tubular housing adjacent a proximal end of said outer tubular housing;
• and
• a latch attached to a distal end of said inner tubular body, said latch including a ring-shaped collar permanently attached to said distal end of said inner tubular body and having an outer diameter sized to slide freely within said outer tubular housing and further including a cantilevered push-stop, said cantilevered push-stop including a portion sized to fit within said recess when said latch is sufficiently disposed within said outer tubular housing, said latch push-stop engaging against a distal edge of said outer tubular housing to oppose bias of said spring;
• wherein when said cantilevered push-stop is urged away from said outer tubular housing, said spring biases said outer tubular housing over said latch and said recess engages a portion of said push-stop.

A method of fabricating a needle stick safety syringe, comprising the following steps:

• (A) providing an inner tubular body, plunger, and needle extending from a distal end of said inner tubular body;
• (B) providing an outer tubular housing concentric with and sized to fit around at least a portion of said inner tubular body and to slide freely thereon;
• (C) disposing a spring within said outer tubular housing to bias apart said inner tubular body and said outer tubular housing;
• (D) defining an annulus-shaped recess within an interior wall surface of said outer tubular housing adjacent a proximal end of said outer tubular housing;
• and
• (E) attaching a latch to a distal end of said inner tubular body, said latch including a ring-shaped collar permanently attached to said distal end of said inner tubular body and having an outer diameter sized to slide freely within said outer tubular housing and further including a cantilevered push-stop, said cantilevered push-stop including a portion sized to fit within said recess when said latch is sufficiently disposed within said outer tubular housing, said latch push-stop engaging against a distal edge of said outer tubular housing to oppose bias of said spring;
• wherein when said cantilevered push-stop is urged away from said outer tubular housing, said spring biases said outer tubular housing over said latch and said recess engages a portion of said push-stop.

A method of preventing re-use of a needle stick safety syringe, comprising the following steps:

• (A) providing a syringe having an inner tubular body, plunger, and needle extending from a distal end of said inner tubular body;
• (B) disposing an outer tubular housing concentric with and sized to fit around at least a portion of said inner tubular body and to slide freely thereon, said outer tubular housing having an interior wall defining a recess and said outer tubular housing being biased away from a said needle when said syringe is to be used;
• (C) attaching a latch to a distal end of said inner tubular body, said latch including a ring-shaped collar permanently attached to said distal end of said inner tubular body and having an outer diameter sized to slide freely within said outer tubular housing and further including a cantilevered push-stop, said cantilevered push-stop including a portion sized to fit within said recess when said latch is sufficiently disposed within said outer tubular housing, said latch push-stop engaging against a distal edge of said outer tubular housing to oppose bias of said spring;
• wherein after said syringe has been used, said cantilevered push-stop is urged away from said outer tubular housing such that said outer tubular housing is biased to cover said latch and said recess engages a portion of said push-stop, wherein said needle is sheathed within a distal region of said outer tubular housing thereby preventing re-use of said syringe.