Retractable hypodermic syringe

摘要

A hypodermic syringe includes a barrel with a plunger assembly slidably extending therein. The plunger assembly includes an outer plunger and an inner plunger telescoping together with a bungee resisting extension of the assembly. The inner and outer plungers may be locked in the extended position with the bungee in tension. A seal stop is located at the seal end of the plunger assembly and holds an annular seal in radial extension sealing against the internal sidewall of the barrel. A luer hub assembly is fixed at the needle end of the barrel. A plunger cap may be advanced after injection to rotate the plunger assembly. Such rotation engages a probe on the end of the plunger assembly with the luer hub, disengages the seal stop to release the annular seal, engages the seal stop with the luer plunger assembly causing release of the luer hub assembly from the barrel and releases the engagement between the outer plunger and inner plunger. The foregoing provides for the retraction of the luer hub and associated needle into the barrel.