Patent ID: 6432087
Filing Date: 2002-08-13
Classification: A61M

Abstract:
A hypodermic syringe with a selectively retractable needle comprises:an elongate barrel having an open proximal end and a distal end defining a receiver with an inwardly projecting shoulder, said barrel having a hollow bore therethrough with an inside surface extending from said proximal end to said distal end; a hollow elongate plunger having a open proximal end and a closed distal end, said plunger having an elongate plug extending distally into said hollow plunger from said open proximal end thereby to form an enclosed cavity within said plunger, said distal end of said plunger forming a slidable seal with said inside surface of said barrel to define a chamber for drawing and expelling fluid; an elongate hub having a passageway therethrough, said hub having a distally extending stem, a proximal flange with an engagement for engaging said barrel, said stem being disposed within and sized for slidable movement within said receiver at said distal end of said barrel, said flange having a distal surface having a groove therein and a proximal surface defining said chamber in said barrel; an elongate needle having a fluid path therethrough, said needle having a sharpened distal end and a proximal end, said proximal end of said needle being mounted in said passageway in said hub so that said sharpened distal end projects distally outwardly and said fluid path is fluidly communicative with said chamber in said barrel; an elongate spring disposed about said stem of said hub, said spring being compressed to provide a bias between said flange and said inwardly projecting shoulder of said receiver; a hollow sleeve sized to fit within said receiver over said elongate spring, said sleeve having a distal end disposed at said shoulder and a proximal end having a sharpened edge disposed in said groove in said distal surface of said flange so that when a user applies a sufficient force, greater than a force necessary to expel fluid from said chamber, to said plunger, said hub is sufficiently moved distally in said receiver for said cutting edge of said sleeve to cut through said flange and said closed distal end of said plunger to expose said cavity therein, thereby to allow said bias of said spring to urge a sufficient proximal movement of a cut portion of said hub having said needle mounted therein, a cut portion of said distal end of said plunger and said sleeve into said cavity in said plunger to a position wherein an inadvertent exposure of said sharpened distal point is substantially prevented.