Syringe with puncturable stem

Claim 1

A syringe comprising 1. a barrel for holding a fluid to be dispensed having a bore closed at one end and open at the other end, 2. a piston having a head slidably received in the open end of the bore and movable in one direction to expel fluid from the barrel and provided with an annular flange flaring outward in said one direction at an acute angle from the head of the piston to the inner barrel wall, the flange in its unstressed condition having its outermost edge thick and non-feathered and of outside diameter greater than the diameter of the bore so the flange is deflected by engagement with the inner barrel wall and the thickness of the flange being great enough, about 0.020 to 0.075 inch, so such mere deflection develops fluid tight sealing pressure under conditions of shock, vibration and temperature encountered during shipment and storage, said piston having a hollow stem of smaller diameter than the head extending from the head out the bore with the end of the stem adjacent the head within and continuously open to the fluid contents of the bore and with the end of the stem remote from the head closed by a puncturable section, the piston being of flexible synthetic thermoplastic resin indifferent to said fluid, 3. a needle holder having a hub, a double ended hollow needle fixed in and extending through the hub with one end presented to the puncturable section and the other end open for feeding an injection site, a sleeve integral with the hub slidably received on the end of said stem remote from the head permitting movement of the hub to puncture said section by said one end of the needle, the hub of thE needle holder and the end of the stem remote from the head having sealing means interengaging as the needle punctures said section to prevent leakage around the outside of the needle.