Patent ID: 6053895
Filing Date: 2000-04-25
Classification: A61L,A61M

Abstract:
A syringe for injecting a fluid medium wherein the syringe has a selected shelf life, comprising:a hollow cylinder of plastic or glass adapted to contain the fluid medium, the cylinder having a smooth cylindrical inner wall surface, a distal end with an outlet and a proximal end for receiving a plunger shaft therethrough;a cylindrical plug having a body portion with an axis, the plug being disposed for sliding movement in an axial direction within the hollow cylinder toward the distal end, the plug being adapted to eject the fluid medium from the hollow cylinder by pushing the medium with a distal face of the plug which is adapted to engage the medium;the plug having a non-sealing substantially cylindrical portion disposed adjacent to the smooth cylindrical inner wall or surface;an annular lip obliquely ex ending in a radial and axial direction from the body portion of the plug, the obliquely extending annular lip having a first surface forming part of the distal face of the plug which is adapted to engage the fluid medium; a second surface which directly touches the smooth cylindrical inner wall surface of the hollow cylinder, and a third surface joining the plug body at a location axially spaced from the first surface to define a root of the lip where the first and third surfaces join the body of the plug; elastic forces in the lip when the plug is at rest with the cylinder having a tension zone in one surface and a compression zone in another surface;at least the annular lip being made of a material selected from the group consisting of polypropylene and polyethylene, wherein the hydrogen atoms of the polypropylene and polyethylene are at least partially replaced by fluorine atoms resulting in polyfluoropropylene and polyfluoroethylene;whereby the lip experiences insignificant cold flow during storage so that a selected plug remains sealed during the shelf life of the syringe and the plug does not have excessive frictional drag when used after storage during the shelf life.