Retractable syringe

Abstract

A retractable syringe includes a barrel [12, 212], one end of which comprises a mounting collar [14, 214]. A needle carrier [16, 216] is releasably mounted within the collar [14, 214], and releasably supports a needle cartridge [18, 218]. A hypodermic needle [20] is mounted within the cartridge [18, 218]. A sheath [22, 222, 418, 420, 422] attaches at one end to the cartridge, and at the other end to the collar. A plunger [36, 236] is telescoped into the barrel [12, 218], and includes a relatively hard piston sealingly engaging the barrel [12, 218]. The piston includes a latch [38, 238] for engaging the carrier [16, 216] and releasing it from the collar [14, 214]. A pocket [76, 476] in the carrier has a support member [54] in its center, and a pair of helical ribs [64] for threadingly engaging a pair of tabs on the cartridge [18, 218]. The cartridge [18, 218] sealingly receives the support member [54]. The collar [14, 214] has slots [82] and inclined threads [84, 256] in its bore wall for engaging lugs [48, 248] on the carrier. The inclined threads [84, 256] have a friction bump [86, 270] near their blind ends. A retaining pin [92, 94] prevents relative rotation between the carrier [16, 216] and collar [14, 214] prior to desired retraction of the needle [20] into the barrel [12, 212]. Alternative embodiments include a barrel which may be resilient or non-resilient and a hard or soft resilient piston, respectively, having a plunger head secured therewithin and attached to the plunger. A latch is attached to the plunger head, and is received in a recess in the carrier to engage latch stops for rotating the carrier to release it from the collar. Alternative embodiments may include means for securing the plunger in the barrel after retraction.