Positive displacement flush syringe

Abstract

A positive displacement flush syringe includes a barrel having a chamber for retaining fluid and an elongate tip extending distally therefrom having a passageway therethrough in fluid communication with the chamber. A plunger having a stopper which is slidably positioned in said chamber for driving fluid out of the chamber by movement of the stopper relative to the barrel is provided. Further, structure is provided to move fluid distally in the passageway after fluid has been delivered from the chamber and the stopper is in contact with the distal wall of the chamber.

1 . A syringe assembly comprising: 
 a barrel including a cylindrical side wall 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 and a resilient stopper 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 stopper having a distal surface and a proximal end having a cavity therein defining an inside surface, said distal end of said plunger connected to said stopper by a complementary detent structure defining a first detent position and a second detent position, said detent structure being configured so that a distally directed force applied to said plunger after fluid has been delivered from said chamber causes said plunger to move distally with respect to said stopper from said first detent position to said second detent position so that a distal tip on said distal end of said plunger contacts said inside surface of said stopper forcing part of said distal end of said stopper into said passageway to move fluid distally in said passageway.    
   
   
       2 . The syringe assembly of  claim 1  further including a spring between said distal tip and said distal end of said plunger, said spring configured to compress when said plunger moves to said second detent position with respect to said stopper.  
   
   
       3 . The syringe assembly of  claim 1  further including said barrel and said plunger having complementary detent structures defining a primary detent position and a secondary detent position to hold the position of said plunger relative to said barrel, said primary detent position being positioned to engage when fluid has been delivered from said chamber and said stopper is in contact with said distal wall, said secondary detent position being engaged upon application of said distally directed force to said plunger.  
   
   
       4 . The syringe assembly of  claim 3  wherein said proximal end of said barrel includes a first discontinuity and a second discontinuity located distally from said first discontinuity and said proximal end of said plunger includes a discontinuity positioned so that when said plunger and said barrel are in said primary detent position said proximal plunger discontinuity engages said first barrel discontinuity and when said plunger and said barrel are in said secondary detent position said proximal plunger discontinuity engages said second barrel discontinuity.  
   
   
       5 . The syringe assembly of  claim 4  wherein said proximal plunger discontinuity is an outwardly directed projection.  
   
   
       6 . The syringe assembly of  claim 5  wherein said outwardly directed projection is an annular ring.  
   
   
       7 . The syringe assembly of  claim 5  wherein said second barrel discontinuity is a recess for containing said proximal plunger discontinuity.  
   
   
       8 . The syringe assembly of  claim 3  wherein said plunger includes a radial projection positioned so that when said plunger and said barrel are in said primary detent position said radial projection engages said inside surface of said barrel and when said plunger and said barrel are in said secondary detent positions, said radial projection engages said inside surface of said barrel at a position located distally from said primary detent position.  
   
   
       9 . A syringe assembly comprising: 
 a barrel including a cylindrical side wall 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;    a tip cap releasably connected to said elongate tip for sealing said passageway;    a plunger including an elongate body portion having a proximal end, a distal end and a resilient stopper, a quantity of flush solution in said chamber, said stopper 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 having a distal surface and a proximal end having a cavity therein defining an inside surface, said distal end of said plunger connected to said stopper by a complementary detent structure defining a first detent position and a second detent position, said detent structure being configured so that a distally directed force applied to said plunger after fluid has been delivered from said chamber causes said plunger to move distally with respect to said stopper from said first detent position to said second detent position so that a distal tip on said distal end of said plunger contacts said inside surface of said stopper forcing part of said distal end of said stopper into said passageway to move fluid distally in said passageway after fluid has been delivered from said chamber; and    a spring between said distal tip and said distal end of said plunger, said spring configured to compress when said plunger moves to said second detent position with respect to said stopper; and said barrel and said plunger having complementary detent structures defining a primary detent position and a secondary detent position to hold the position of said plunger relative to said barrel, said primary detent position being positioned to engage when fluid has been delivered from said chamber and said stopper is in contact with said distal wall, said secondary detent position being engaged upon application of said additional distally directed force to said plunger.    
   
   
       10 . The syringe assembly of  claim 9  further including a distally directed projection on said distal end of said stopper shaped to fit in said passageway when said plunger and said stopper are engaged in said second detent position.  
   
   
       11 . The syringe assembly of  claim 9  wherein said inside surface of said stopper includes a proximally directed protuberance configured to contact said distal tip of said plunger when said plunger and said stopper are engaged in said second detent position.