Patent ID: 7364569

Claim:
A retractable safety syringe comprising: a hollow barrel having a first end and a second end opposite the first end, wherein an inner surface of the barrel has an end wall with an opening that allows medication to exit the barrel; a needle set, including a needle and a needle seat for attaching the needle at the first end of the barrel, wherein the needle seat has a first connecting structure; and a plunger slidably mounted within the barrel, wherein one end of the plunger is mounted with a piston, and the plunger terminates with a second connecting structure engageable with the first connecting structure; wherein at one end of a translation course of the piston within the barrel, the piston contacts the end wall around to the opening, and further movement of the plunger towards the first end while the front surface of the piston is in contact with end wall of the barrel causes the first connecting structure to engage with the second connecting structure to lock the plunger with the needle set; wherein the translation course of the plunger is impeded by the contact between the piston and the end wall without engaging the first and second connecting structures.