AUTO-RETRACTABLE SAFETY (ARS) SYRINGE FOR SINGLE USE

Patent Pending The present invention relates to a safety syringe having an auto retractable needle for use in the medical or dental profession or in personal drug administration so that the physicians, surgeons or other needle operators may be protected from the needle-stick injury during its use. The invention, in particular, relates to an assembly of the safety syringe which is simple and easy in handling, in which the hypodermic needle retracts itself automatically by virtue of self generated vacuum and encapsulate within the barrel as soon as the last drop is injected in the body of patient. The syringe thereafter becomes finally locked to become non-reusable. The handling of syringe does not require any special training to the operators. It is simple in manufacture. The Auto-Retractable Safety Syringe for single use comprises a plunger assembly to slidably and axially move inside the outermost barrel, holding a needle carrier assembly in conical jacket at proximal end. The plunger assembly comprises a needle retraction assembly, which further comprises a retraction shaft, housing inside the retraction hub along with a compressed spring. The shaft is provided with a piston seal at distal end and an axially furrowed nipple at proximal end. The shaft is also provided with an outer circumferential conical groove at proximal end, which facilitates the shaft to get held firmly along with a compressed spring inside the retraction hub with engagement of conical notch T-1 of outwardly protruded finger lock provided in the retraction hub. The proximal portion of the finger lock is customised into a flange to remains in contact of distal surface of ring plate. At proximal end the retraction assembly is provided with a combination of two parallel ring plates, wherein the distal ring plate is diametrically provided with oppositely positioned two axial pins P-1 and P-2 which slidably protrude out at proximal ends, passing through the respective holes H-1 and H-2 provided in proximal ring plate The needle carrier assembly comprises a hypodermic needle having an axial cavity opening at distal end, housed in axial passage of needle carrier hub and engages therein with the inner conical teeth T-3 of finger lock through outer circumferential groove. The needle carrier assembly is housed inside the conical jacket provided at proximal end of outermost barrel through a combination of an O-ring and a ring plate. During the completion of injection process the nipple inserts in distal cavity to engage needle. The respective finger locks of needle retraction assembly and needle carrier assembly are open simultaneously due to the pressure exerted on their respective flanges and of finger locks and by movement of plunger assembly in forward direction. This action facilitates to retract the shaft along with needle to dislodge and gently move in backward direction and finally encapsulate needle in plunger barrel. The outwardly protruded finger lock provided at distal end of the plunger barrel also clicks lock the plunger barrel inside the outermost barrel by seating conveniently in the inner circumferential conical groove provided at the distal end of the outermost barrel to completely lock the syringe and render it useless for any further use.