Retractable hypodermic syringe

Abstract

A hypodermic syringe includes a barrel with a plunger slidably extending therein. The barrel may include a barrel adapter at one end to define a luer hub socket and the outer walls of slots in the barrel. The plunger includes an outer plunger element and an inner plunger element telescoping together with a bungee resisting extension of the assembly. The inner and outer plunger elements may be locked in the extended position with the bungee in tension. A seal stop is located at the seal end of the plunger to define an annular pinch therewith to hold an annular seal in radial extension sealing against the internal sidewall of the barrel. A luer hub is fixed at the needle end of the barrel, A plunger cap may be advanced after injection to rotate the plunger. A resistance lock retains the cap and plunger indexed until actuation. The rotation actuates latches and locking fingers on the luer hub to engage a probe axially and rotationally on the seal end of the plunger and disengage the slots in the barrel, respectively. The rotation disengages the seal stop to release the annular seal and finally releases the engagement between the outer plunger element and inner plunger element. The foregoing provides for the retraction of the luer hub and associated needle into the barrel.

1 . A retractable syringe comprising
 a barrel including a bore, an entry portion at a first end of the barrel and a main body in axial juxtaposition with the entry portion, the entry portion and the main body including mating surfaces in mutual juxtaposition, the bore having a first inside diameter in the entry portion and a second, smaller inside diameter in the main body, the entry portion having a snap extending from the entry portion across the juxtaposed mating surfaces and the main body having a snap socket adjacent the juxtaposed mating surfaces receiving the snap;   a plunger slidably positioned within the barrel, the snap limiting with the stroke of the plunger.   
   
   
       2 . The retractable syringe of  claim 1 , the resilient latch having a cam follower, the forward end of the plunger further having a cam engageable with the cam follower with the probe positioned within the recess, the cam oriented to move the cam follower and the resilient latch toward the recess with rotation of the plunger. 
   
   
       3 . The retractable syringe of  claim 1  further comprising
 a seal stop mounted to the forward end of the plunger, releasable with rotation of the seal stop relative to the plunger and forming an annular pinch with the forward end of the plunger;   an annular plunger seal held in radial expansion within the pinch, the luer hub further including an engagement extending t the seal stop and positioned to prevent rotation of the seal stop relative to the luer hub with the plunger at substantially full extension toward the first end of the barrel.   
   
   
       4 . The retractable syringe of  claim 1  further comprising
 a cap at one end of the plunger, the plunger further including a hollow outer plunger element receiving the cap, the cap including a first attachment facing into the hollow outer plunger element, a hollow inner plunger element telescoping together with the hollow outer plunger element and having a second attachment facing the first attachment and located axially in the hollow inner plunger element near the end most distant from the cap, a resilient tension element fixed to the first attachment and the second attachment and being just substantially relaxed with the outer plunger element and the inner plunger element telescoped together and a releasable engagement between the hollow outer plunger element and the hollow inner plunger element engageable with the hollow outer plunger element and the hollow inner plunger element telescoped to an extended position and releaseable with rotation of the plunger.   
   
   
       5 . The retractable syringe of  claim 1 , the mating surfaces having a pin and socket engagement. 
   
   
       6 . The retractable syringe of  claim 5 , the resilient latch angularly and axially engaging the probe in the undercut. 
   
   
       7 . The retractable syringe of  claim 5 , the first end having a slot, the resilient latch further having a locking finger extending radially into the slot and movable from the slot with movement of the cam follower toward the recess. 
   
   
       8 . The retractable syringe of  claim 5 , the barrel including a radially extending flange defining a finger grip, the radially extending flange being split equatorially defining the juxtaposed mating surfaces. 
   
   
       9 . The retractable syringe of  claim 8  further comprising
 a cap at one end of the plunger, the plunger further including a hollow outer plunger element receiving the cap, the cap including a first attachment facing into the hollow outer plunger element, a hollow inner plunger element telescoping together with the hollow outer plunger element and having a second attachment facing the first attachment and located axially in the hollow inner plunger element near the end most distant from the cap, a resilient tension element fixed to the first attachment and the second attachment and being just substantially relaxed with the outer plunger element and the inner plunger element telescoped together and a releasable engagement between the hollow outer plunger element and the hollow inner plunger element engageable with the hollow outer plunger element and the hollow inner plunger element telescoped to an extended position and releaseable with rotation of the plunger.   
   
   
       10 . A retractable syringe comprising
 a barrel;   a plunger slidably positioned within the barrel and including into a hollow outer plunger element and an inner plunger element telescoping together with the hollow outer plunger element to define extended and retracted states, the hollow outer plunger element having a longitudinally extending indexing groove with a transversely extending extension socket at one end, the inner plunger element including a latch engaging the indexing groove to constrain the two plunger elements from relative rotation, the transversely extending extension socket being sized to releasably receive the latch for retention of the plunger in the extended state, the outer plunger element further having a longitudinally extending indexing slot and the barrel having an inwardly extending indexing element engaged with the indexing slot, the indexing slot including a circumferential section at one end, the indexing element being selectively extendible into the circumferential section to prevent retraction of the plunger from the barrel.   
   
   
       11 . The retractable syringe of  claim 10 , the longitudinally extending indexing groove further having a transversely extending retraction socket at the other end, both transversely extending sockets being sized to releasably receive the latch for retention of the plunger in either of the extended and retracted states, the indexing slot lying within the indexing groove. 
   
   
       12 . A retractable syringe comprising
 a barrel;   a plunger slidably positioned within the barrel and including into a hollow outer plunger element and an inner plunger element telescoping together with the hollow outer plunger element to define extended and retracted states;   a resilient tension element includes a T-head at one end and an eye at the other end;   a cap is located at one end of the hollow outer plunger element; the cap and the inner plunger element include attachments facing one another and receiving the resilient tension element, the attachment of the cap having a slot to receive the T-head and the inner plunger element having a hook opening away from the cap to receive the eye.