Automatic needle-retracting syringe

A single use syringe for use with a liquid injectant comprising:

• a barrel having a needle end, a plunger end and defining a bore therein;
• a plunger slidably mounted within the bore at the plunger end, the plunger including a plunger gasket defining an injectant region between the plunger gasket and the needle end of the barrel;
• a hollow needle extending from the needle end of the barrel and having a point and a base, the base in fluid communication with the injectant region;
• a supplemental pathway fluidly coupling the injectant region and a supplemental region the supplemental region includes an axial bore within the plunger;
• and
• means for sealing the supplemental pathway until a period of time after the liquid injectant has been in contact with the sealing means, said sealing means being weakened by said contact with the liquid injectant so to permit flow of the liquid injectant from the injection region to the supplemental region after the period of time.

An automatic needle retracting syringe for use with a liquid injectant comprising:

• a barrel having a needle end, a plunger end and defining a bore therein;
• a plunger slidable mounted within the bore and extending out from the bore at the plunger end;
• a hollow needle having a base and a point and mounted to a needle gasket, the needle gasket slidably mounted within the bore to divide said bore into a near region towards the plunger end and a far region towards the needle end, the needle gasket having a main body, a tip extending towards the far region, a path fluidly coupling the point to the near region and a hole fluidly coupling the path to the far region;
• a spring disposed within the barrel between the needle gasket and the needle end, the spring biasing the needle gasket and needle therewith towards a retracted position wherein in the retracted position the needle is housed entirely within the barrel;
• the needle gasket being movable between the retracted position and an extended position at which the point of the needle extends from the needle end of the barrel;
• a dissolvable capsule secured in the barrel near the needle end and configured to receive and fictionally retain the tip of the needle gasket when the needle gasket is in the extended position, the dissolvable capsule constructed of material which dissolves upon contact with the liquid injectant over a period of time so as to compromise the frictional engagement between the tip and the capsule and thereby permit the spring to move the needle gasket and needle therewith to the retracted position;
• an axial bore within the plunger fluidly coupled to the near region;
• a dissolvable sealing means disposed within said axial bore which weakens during contact with the liquid injectant so to permit flow of the liquid injectant from the near region through axial bore and into a supplemental region.