Abstract: A hypodermic syringe system for injecting a predetermined dosage of therapeutic fluid into body tissue of a living patient. A sealed capsule contains the fluid to be injected. A double ended hypodermic needle includes a first sharpened end for piercing engagement with the body tissue and a second sharpened end opposite therefrom for piercing engagement with the capsule. The capsule is disposed between the end of a plunger which is slidably engaged within a barrel member supporting the needle and the end wall of the barrel member. Advancement of the plunger moves the capsule into piercing engagement with the second sharpened end of the needle, collapsing the capsule and discharging the therapeutic fluid through the needle and into the body tissue. A safety syringe with a retractable needle is disclosed. The system is also provided with an aspirating capability to inform the user whether or not a blood vessel has been pierced by the needle.

Abstract: An improved hypodermic syringe includes a needle retraction feature permitting the needle to be fully retracted into the cylindrical cavity of the syringe barrel following the injection of medicine into a patient. The needle is held on the distal end of the barrel by means of an attachment hub, which includes an internal abutment surface to prevent outward movement of the needle. Inward movement of the needle is prevented by an expandable restriction of a distal barrel opening, extending between the cylindrical cavity and the distal end of the barrel. The needle is part of a subassembly including a flange held between this internal abutment surface and this expandable restriction. The distal end of the plunger is fitted with a needle extractor, which moves into the distal barrel opening as the plunger is pushed fully into the cylindrical cavity.