Medical devices with retractable needle

Abstract

A hypodermic injection system with a retractable needle wherein the needle retracts within an interior cavity of a syringe plunger, such that the needle is confined within the plunger. A spring biases the needle rearwardly into the plunger, and a needle retainer releasably retains the needle against the bias of the spring. The plunger has a frangible end, which dissociates when the plunger engages the needle retainer, allowing the coiled spring to eject the needle into the interior cavity of the plunger. A body fluid sampling embodiment employs the same functional elements except the plunger is shorter and contains a linking that communicates with a vacuum container. The container allows fluid sampling and provides the structure to release the spring retracting the needle. The retractable needle embodiment is also employed with an insertion needle that guides a catheter tube below the skin of a patient and into the vein, and allows retraction of the insertion needle thereby avoiding accidental pricking of the health care worker by the insertion needle.

1 . A medical device, comprising: 
 a barrel having a recess formed adjacent a rearward end of the barrel;    a needle;    a spring biasing the needle rearwardly    a plunger axially displaceable within the housing and operable to expel fluid from the barrel, wherein the plunger comprises: 
 a cavity for receiving the needle after use;  
 a flange on the rearward end of the plunger operable to displace the plunger within the barrel;  
   wherein the recess is configured to receive the flange after use so that substantially the entire plunger is disposed within the barrel after use so that the plunger cannot be readily removed from the barrel after use; and    wherein after use the spring retracts the needle into the cavity in the plunger.    
     
     
         2 . The device of  claim 1  wherein the recess is integrally formed with the barrel.  
     
     
         3 . The device of  claim 1  wherein the device comprises a needle holder holding the needle in a projecting position during use.  
     
     
         4 . The device of  claim 3  wherein the needle holder comprises a breakable connection, and pushing forwardly on the plunger operates to fracture the breakable connection to release the needle.