Safety syringe

Abstract

A hypodermic syringe provides a simple mechanism for manually retracting its needle into the syringe after injection has been completed. The syringe preferably has an elastomeric barrel to exert a radial bias to seal on a retractable needle carrier and the plunger. Attachment components on the plunger and needle carrier engage such that withdrawal of the plunger releases the needle carrier for withdrawal into the syringe barrel.

1 . A safety syringe comprising: 
 a hollow barrel having a forward and rear end, said barrel including proximate the forward end a first retention structure and a first coupling structure and proximate said rear end a second retention structure;    a needle carrier disposed at said forward end and including (i) a third retention structure engaging the first retention structure to releaseably retain the needle carrier at said forward end and to engage the second coupling structure to retain said needle carrier in the barrel, (ii) a second coupling structure to engage the first coupling structure to prevent rotation of the needle carrier at said forward end, (iii) a mounting for mounting a needle and (iv) a first attachment component disposed opposite said mounting; and    a plunger having a head to slideably seal within the barrel for aspiration of fluid into an out of the barrel and a second attachment component to engage the first attachment component of the needle carrier to attach the needle carrier to said head, withdrawal of the plunger disengaging the third retention structure from the first retention structure to release the needle carrier and needle to be withdrawn a position in the barrel where the third retention structure engages the second retention structure to retain the needle carrier and needle in the withdrawn position.    
   
   
       2 . The safety syringe of  claim 1  comprising said first and second retention structures include radial projections in said barrel and said third retention structure includes a cooperative radial depression in said needle carrier to receive said projections.  
   
   
       3 . The safety syringe of  claim 2  comprising said first and second retention structures include radially projecting ridges and said third retention structure includes a radial groove in said needle carrier.  
   
   
       4 . The safety syringe of  claim 1  comprising said first and second retention structures include grooves in said barrel and said third retention structure includes a radial protuberance to engage into said grooves.  
   
   
       5 . The safety syringe of  claim 1  comprising said barrel is constructed from an elastomeric material.  
   
   
       6 . The safety syringe of  claim 1  comprising said first and second attachment components includes a deformable tab snap-engaging a cooperative recess.  
   
   
       7 . The safety syringe of  claim 1  comprising said mounting is a luer lock mounting.  
   
   
       8 . The syringe of  claim 1  comprising said first and third retention structures cooperating to release the needle carrier at a first withdrawal force and said second and third retention structures cooperating to release the needle carrier at a greater, second withdrawal force.  
   
   
       9 . A safety syringe comprising: 
 a hollow cylindrical barrel having a forward and rear end, said barrel including proximate the forward end a first radial projection and a first coupling structure and proximate said rear end a second radial projection;    a needle carrier disposed at said forward end and including (i) a depression to receive the first projection to releaseably retain the needle carrier at said forward end and to receive the second projection to retain said needle carrier in the barrel, (ii) a second coupling structure to engage the first coupling structure to prevent rotation of the needle carrier at said forward end, (iii) a mounting for mounting a needle and (iv) a first attachment component disposed opposite said mounting; and    a plunger having a head to slideably seal within the barrel for aspiration of fluid into an out of the barrel and a second attachment component to engage the first attachment component of the needle carrier to attach the needle carrier to said head, withdrawal of the plunger disengaging the third retention structure from the first retention structure to release the needle carrier and needle to be withdrawn a position in the barrel where the third retention structure engages the second retention structure to retain the needle carrier and needle in the withdrawn position.    
   
   
       10 . A safety syringe comprising: 
 a hollow barrel having a forward and rear end, said barrel including proximate the forward end a first groove and a first coupling structure and proximate said rear end a second groove;    a needle carrier disposed at said forward end and including (i) a protuberance to engage into the first groove to releaseably retain the needle carrier at said forward end and to engage into the second groove to retain said needle carrier in the barrel, (ii) a second coupling structure to engage the first coupling structure to prevent rotation of the needle carrier at said forward end, (iii) a mounting for mounting a needle and (iv) a first attachment component disposed opposite said mounting; and    a plunger having a head to slideably seal within the barrel for aspiration of fluid into an out of the barrel and a second attachment component to engage the first attachment component of the needle carrier to attach the needle carrier to said head, withdrawal of the plunger disengaging the third retention structure from the first retention structure to release the needle carrier and needle to be withdrawn a position in the barrel where the third retention structure engages the second retention structure to retain the needle carrier and needle in the withdrawn position.