Patent ID: 6986756

Claim:
A single use syringe assembly comprising: a barrel having an inside surface defining a chamber for retaining fluid, and open proximal end and a distal end having a passageway in communication with said chamber; a plunger rod assembly including an elongate body portion having a proximal end, a distal end, and a stopper on said elongate body portion proximate said distal end, said stopper being slidably positioned in substantially fluid-tight engagement with said inside surface of said barrel for drawing fluid into and out of said chamber by movement of said stopper relative to said barrel, said elongate body portion extending outwardly from said open proximal end of said barrel; and a generally trough-shaped locking element positioned within said barrel, said locking element defining a channel, said elongate body portion of said plunger rod assembly extending through said channel; one or more barbs extending from said locking element, said one or more barbs engaging said inside surface of said barrel for substantially preventing said locking element from moving proximally with respect to said barrel but allowing movement of said locking element towards said distal end; said locking element engaging said elongate body portion of said plunger rod assembly such that said locking element is movable towards said distal end of said barrel as said plunger rod assembly is advanced; a spring member attached to said locking element and urging said one or more barbs towards said inside surface of said barrel; and said proximal end and said distal end of said plunger rod being connected by a breakable connection, one of said proximal end and said distal end including an axial projection having at least one transverse protuberance projecting therefrom, said protuberance being connected to the other of said proximal portion and said distal portion, said breakable connection being on said protuberance, said breakable connection being strong enough to hold said proximal end and said distal end together during normal use of said syringe and breakable upon application of an additional force applied to said proximal portion along said longitudinal axis, said breakable connection being positioned proximally with respect to said locking element.