Hypodermic syringe with retractable needle

摘要

A hypodermic syringe including a barrel having a closed end, an open end, and an interior surface. A plunger is reciprocally received in the barrel through the open end and in sealing engagement with the interior surface of the barrel and forming a chamber. A hollow needle is detachably attached to the barrel at the closed end of the barrel. The plunger has a hole leading to a cavity. A spring is located within the cavity and is connected to the plunger at one end and a first mating member at the other end. The first mating member is detachably attached to the plunger end. A second mating member is attached to the needle. In operation, liquid is injected in a normal fashion by pushing the plunger toward the closed end of the barrel. When the plunger approaches the barrel closed end, the first and second mating members attach to one another. Further forward movement of the plunger first detaches the needle from the barrel and, thereafter, detaches the second mating member from the plunger and, thus, the spring draws the needle through the hole to within the cavity.