Patent ID: 8882724

Claim:
An I.V. flush syringe assembly comprising: a barrel having an inside surface defining a chamber for retaining fluid, an open proximal end and a distal end including a distal wall with an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with said chamber; and a plunger including an elongate body portion having a proximal end, a distal end including a base extending axially therefrom in a distal direction having a first portion with a first outer diameter connected to the distal end of the elongate body portion and a second portion extending axially in a distal direction from the first portion, wherein the second portion includes threads, and a stopper releasably supported by said base and being slidably positioned in fluid-tight engagement with said inside surface of said barrel for drawing fluid into and driving fluid 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, said stopper having a distal end and a proximal end releasably disposed on the base by threaded engagement with the threads on the second portion of the base to have a relief at a distance D between the proximal end of the stopper and the distal end of the elongate body portion and having an annular groove concentrically surrounding said base, wherein the annular groove has a consistent inner diameter that is the same as the first outer diameter of the first portion of the base; said relief and annular groove creating a structure, wherein said structure allows the proximal end of the stopper to be more flexible at its proximal end than at its distal end in response to proximally directed force on said stopper and so that the proximal end of the stopper absorbs compressive force to minimize deflection of said stopper at its distal end when fluid has been delivered from said chamber and said stopper is in contact with said distal wall.