Retractable hypodermic syringe

摘要

A hypodermic syringe includes a barrel with a plunger slidably extending therein. The barrel may include a barrel adapter at one end to define a luer hub socket and the outer walls of slots in the barrel. The plunger includes an outer plunger element and an inner plunger element telescoping together with a bungee resisting extension of the assembly. The inner and outer plunger elements may be locked in the extended position with the bungee in tension. A seal stop is located at the seal end of the plunger to define an annular pinch therewith to hold an annular seal in radial extension sealing against the internal sidewall of the barrel. A luer hub is fixed at the needle end of the barrel. A plunger cap may be advanced after injection to rotate the plunger. A resistance lock retains the cap and plunger indexed until actuation. The rotation actuates latches and locking fingers on the luer hub to engage a probe axially and rotationally on the seal end of the plunger and disengage the slots in the barrel, respectively. The rotation disengages the seal stop to release the annular seal and finally releases the engagement between the outer plunger element and inner plunger element. The foregoing provides for the retraction of the luer hub and associated needle into the barrel.