SELF-RETRACTABLE SAFETY (SRS) 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 present subject matter relates to self-retractable safety syringe for single use comprising a plunger assembly including a plunger barrel and a plunger plug, a needle carrier assembly, and an outermost barrel. The plunger plug holding a centrally positioned furrowed axial knob housed in plunger barrel at the proximal end and firmly held by the inner teeth T-2 & T-4 of finger locks and respectively. A needle carrier assembly is housed in conical jacket of outermost barrel holding a needle along with a compressed spring. The needle is locked inside the needle carrier assembly with the help of finger lock provided with outwardly protruded flange .The flange is placed in contact with a slidable elastic O-ring holding the needle carrier assembly inside the conical jacket. At the completion of injection process, the furrowed knob inserts into the distal cavity of needle to lock the needle with plug. When the elastic O-ring slides in forward direction due to the axial movement of plunger barrel in forward direction, the O-ring pushes the flange of finger lock, to unlock the lock. At the same time, the teeth outer T-1 & T-3 of the finger locks & respectively become in alignment of inner circumferential conical groove of outermost barrel and restore their normal state by expanding in outward direction to occupy the outer space provided by the groove. This result the respective inner teeth T-2 & T-4 of the finger locks & to retract and release the plunger plug due to expansion of locks in outward direction. Consequently, the plunger plug holding the needle moves smoothly in backward direction due to the pressure exerted by expansion of spring in backward direction. Simultaneously, the finger lock provided at the distal end of plunger barrel slips into the inner circumferential conical groove and click locks the plunger barrel inside the outermost barrel to render the syringe assembly completely locked with the needle encapsulated within the plunger barrel. The distally directing, outwardly protruded finger locks and provided at the proximal end of plunger barrel prevent the removal of plunger barrel from the outermost barrel.