Single-use syringe

Abstract

A single use syringe ( 10 ) includes a needle ( 18 ), barrel ( 16 ), plunger assembly ( 20 ) and shield ( 12 ). The barrel ( 16 ) bears a locking member ( 26 ) which encircles the front end of the barrel ( 16 ) and is carried forward by the barrel ( 16 ) to a position where it engages the shield ( 12 ) and is retained by the shield ( 12 ) such that the locking member ( 26 ) is separated from the barrel ( 16 ) as the barrel ( 16 ) is withdrawn rearwardly after use. The locking member ( 26 ) is resilient and, after it is removed from the barrel ( 16 ), assumes a configuration which prevents subsequent forward movement of the barrel ( 16 ) within the shield ( 12 ). The barrel includes a frangible seal ( 30 ) which is broken by rearward movement of needle mount ( 32 ). The shield ( 12 ) includes a shield extender ( 14 ) for controlling the depth of penetration of the needle. The syringe can also be used to inject medicament into a IV bag via a male port as shown in FIG. 7.

What is claimed is:  
     
         1 . A single-use syringe, comprising: 
 a shield;    a barrel adapted to contain a medicament and mounted for axial reciprocation within the shield; and    a locking member initially mounted on the barrel, wherein the locking member engages the shield during expression of medicament from the barrel, and subsequent to said engagement is dismounted from the barrel, the dismounted locking member thereafter preventing reciprocation of the barrel within the shield.    
     
     
         2 . A single-use syringe as claimed in  claim 1 , wherein the locking member initially encircles a forward end of the barrel, and is dismounted from the forward end of the barrel during rearward reciprocation of the barrel within the shield.  
     
     
         3 . A single-use syringe as claimed in  claim 1 , wherein the shield includes a slot, and wherein the locking member engages, and is retained by, the slot.  
     
     
         4 . A single-use syringe, comprising: 
 a shield;    a barrel adapted to contain medicament and mounted for axial reciprocation within the shield; and    a locking member initially mounted relative to the barrel for reciprocation therewith, wherein the locking member engages and is retained by the shield during expression of medicament from the barrel, and as a result of said engagement and retention the locking member is translated relative to the barrel during rearward reciprocation of the barrel within the shield, the locking member then preventing subsequent reciprocation of the barrel within the shield.    
     
     
         5 . A single-use syringe comprising: 
 a shield with a forward end and a rearward end;    a barrel with a forward end and a rearward end, the barrel mounted for axial reciprocation within the shield between a rearward position and a forward position;    a needle mounted on the forward end of the barrel such that when the barrel is in the forward position the needle is exposed;    a locking member adapted to prevent exposure of the needle by forward reciprocation of the barrel when the locking member is dismounted from the barrel, the locking member being removably mounted to the forward end of the barrel and adapted to engage the forward end of the shield when the needle is exposed by forward reciprocation of the barrel, the engagement being sufficient to dismount the locking member from the forward end of the barrel during rearward reciprocation of the barrel, the locking member thereafter preventing further exposure of the needle by forward reciprocation of the barrel.