Safety Medical Syringe with Retractable Needle and Including a Plunger that is Received within a Barrel

A syringe comprising:

• a hollow barrel including an opening at a proximal end of the barrel, an opening at a distal end of the barrel and a fluid chamber disposed within the barrel;
• a hollow plunger extending into the barrel via the proximal end opening and axially movable within the barrel toward and away from the distal end opening, wherein the plunger includes an end wall that is releasably secured to the plunger at an opening disposed at a distal end of the plunger and is movable from the plunger distal end opening during use of the syringe to facilitate access to a retraction cavity disposed within the plunger;
• and
• a needle assembly secured within and at a distal end of the barrel, the needle assembly including a needle holder, a resilient member biasing the needle holder toward the proximal end opening of the barrel, and a retaining member releasably secured to the needle holder via a reduced material section, wherein the needle holder includes a connector to secure a needle to the needle holder so as to permit the needle to extend through the distal end opening of the barrel;
• wherein the plunger, retaining member and needle holder are configured such that the retaining member maintains the needle holder at the distal end of the barrel against the bias of the resilient member and, when the plunger is fully depressed within the barrel, the plunger engages the needle holder to force the end wall of the plunger within the plunger and to force the retaining member to break away and separate from the needle holder along the reduced material section so as to facilitate retraction into the retraction cavity of the end wall, the needle holder and a needle secured to the needle holder;
• and
• wherein the plunger includes a thumb pad disposed at a proximal end of the plunger, the thumb pad including a flange that extends transversely from a longitudinal orientation of the plunger and includes a dimension that is greater than the proximal end opening of the barrel, and an annular edge portion of the flange is resiliently flexible and bendable to permit insertion of the flange within the plunger so as to lock the plunger within the barrel after a single use of the syringe.

A method of utilizing a syringe of the type including a hollow barrel including a proximal end with an opening, a distal end and a fluid cavity disposed within the barrel, and a plunger extending into the barrel via the proximal end opening and axially movable within the barrel toward and away from the barrel distal end, the plunger including a proximal end and a distal end that extends within the barrel and is movable toward and away from the barrel distal end to facilitate drawing fluid into and forcing fluid from the fluid cavity within the barrel, the plunger further including a thumb pad comprising a flange that extends transversely from a longitudinal orientation of the plunger and includes a dimension that is greater than the proximal end opening of the barrel, the method comprising:

• facilitating receipt of fluid into a fluid cavity within the barrel by moving the distal end of the plunger toward the proximal end of the barrel;
• facilitating withdrawal of fluid from the fluid cavity within the barrel by moving the distal end of the plunger toward the distal end of the barrel;
• and
• forcing the plunger with thumb pad into the barrel via the proximal end opening in the barrel such that the thumb pad flange flexes and bends and is at least partially received in the barrel so as to substantially prevent or frustrate efforts by a user to remove the plunger from the barrel.

A method of utilizing a syringe of the type including a hollow barrel with an opening at a proximal end of the barrel, an opening at a distal end of the barrel and a fluid chamber disposed within the barrel, a hollow plunger extending into the barrel via the proximal end opening and axially movable within the barrel toward and away from the distal end opening, the plunger including an end wall that is releasably secured to the plunger at an opening disposed at a distal end of the plunger, and a needle assembly secured within and at a distal end of the barrel, the plunger further including a thumb pad comprising a flange that extends transversely from a longitudinal orientation of the plunger and includes a dimension that is greater than the proximal end opening of the barrel, the needle assembly including a needle holder, a resilient member biasing the needle holder toward the proximal end opening of the barrel, a retaining member releasably secured to the needle holder via a reduced material section and a needle secured to the needle holder, the method comprising:

• facilitating aspiration of fluid through the needle and into a fluid cavity within the barrel by moving the distal end of the plunger toward the proximal end of the barrel;
• facilitating withdrawal of the aspirated fluid from the fluid cavity within the barrel by moving the distal end of the plunger toward the distal end of the barrel;
• facilitating retraction of the needle holder within a retraction cavity defined within the plunger upon complete movement of the plunger into the barrel, wherein the plunger is configured to engage the needle holder upon complete movement of the plunger into the barrel such that the end wall of the plunger is forced within the plunger and the retaining member is forced to break away and separate from the needle holder along the reduced material section to facilitate retraction into the retraction cavity of the end wall, the needle holder and the needle secured to the needle holder into the retraction cavity;
• and
• after retraction of the needle holder within the retraction cavity, forcing the plunger with thumb pad into the barrel via the proximal end opening in the barrel such that the thumb pad flange flexes and bends and is at least partially received in the barrel so as to substantially prevent or frustrate efforts by a user to remove the plunger from the barrel.