A retractable syringe includes a resilient barrel, one end of which comprises a mounting collar. A needle carrier is releasably mounted within the collar, and releasably supports a needle cartridge. A hypodermic needle is mounted within the cartridge. A sheath attaches at one end to the cartridge, and...http://www.google.es/patents/US5112315?utm_source=gb-gplus-sharePatente US5112315 - Retractable syringe
