Hypodermic syringe having a selectively retractable needle

摘要

A syringe (10) includes an elongate barrel (12) having an open proximal end (18) and a distal end (20) that includes a fitting (22). It also has a plunger (24) having a proximal end (26) and a distal end (28), sized for slidable movement within the barrel (12) thereby defining a chamber (30) within the barrel. The plunger (24) also has an elongate cavity (32) therewithin that has a closed proximal end (34) and an open distal end (36). The open end (36) of the plunger (24) is closed by a selectively releasable closure (38). The syringe has a hub (42) that attaches to the barrel (12) with a fitting (44) conjugate to the fitting (22). The hub (42) includes an elongate needle (48) having a proximal end (50), a distal end (52) and a fluid path (54) therethrough. The needle (48) is positioned in the passageway (46) for slidable movement between a first position wherein the fluid path (54) of the needle (48) is in fluid communication with the chamber (30) and a second position. The needle (48) has a mount at its proximal end (50) forming a seal (60) with the chamber (30) when the needle (48) is in the first position. The syringe has a spring (62) disposed about the mount (56) biased to urge slidable movement of the needle (48) from the first position. The syringe (10) includes a latch (64) disposed in the hub (42) to engage the mount (56) and retain the mount in the first position. The latch (64) is releasable so that the spring (62) urges the needle (48) to move from the first into the second position within the cavity (32) in the plunger (24), once the latch (64) is released.