Patent ID: 8322577

Claim:
A syringe, comprising: an elongate barrel having first and second ends and a bore therethrough; a cannula attached to said first end and extending into said bore, said cannula being in fluid communication with said bore; a plunger positioned within said bore, said plunger extending from said second end of said bore and being movable toward and away from said cannula within said bore, said plunger comprising: an elongate rod having a longitudinal axis and an end portion, wherein the end portion has a smaller diameter than a diameter of a remainder of the rod, thereby forming a first shoulder between the end portion and the remainder of the rod, and wherein the end portion comprises a head having a larger diameter than a diameter of a remainder of the end portion, thereby forming a second shoulder facing the first shoulder, wherein the first shoulder and the second shoulder are oriented perpendicularly to the longitudinal axis of said elongate rod; an end surface of the head being oriented transversely to said longitudinal axis of said rod; and a flexible sleeve in a shape of a cylinder surrounding said end portion, said sleeve contacting said bore and providing a seal between said plunger and said barrel, wherein the flexible sleeve has a first end surface defining an end of the cylinder, wherein the first end surface contacting and covering the first shoulder, and the flexible sleeve wraps around the second shoulder and the head in a snug fit such that a flexible layer of the flexible sleeve covers the end surface of the head, said flexible layer having a thickness less than or equal to about 0.78 times the diameter of said bore.