US Patent 8021333 Syringe spring retainer

A spring retainer (60) for a syringe (10) that has a barrel (40), a plunger (20), a spring (90) and a retractable needle (50) that can couple with the plunger for spring-driven retraction of the coupled needle and plunger. The spring retainer has first (70) and second (80) body members that cooperate to releasably maintain the spring in a compressed state until the plunger is coupled to the retractable needle after depression of the plunger to deliver the fluid contents of the syringe. Depression of the plunger triggers rotational disengagement of the first and second body members to allow decompression of the spring which forces retraction of the needle into the barrel. Rotational disengagement of the first and second body members also assists rotation of the plunger into a final, inoperable position.