Patent ID: 6224577
Filing Date: 2001-05-01
Classification: A61M

Abstract:
A plunger for use in a syringe, the plunger comprising:a first, relatively high-pressure member extending around the circumference of the plunger in substantially sealing contact therewith, the first pressure member comprising a forwardmost sealing edge and being sufficiently flexible to be forced radially outwardly to exert force upon an inner wall syringe in response increasing fluid pressure within the syringe during forward movement of the plunger and to compensate for an expansion of the inner wall of the syringe caused by the increasing fluid pressure, the first pressure member thereby forming a substantially sealing engagement with the inner wall of the syringe;a second, relatively low-pressure member extending radially outward from the plunger at a position rearward from the first pressure member and in substantially sealing engagement with the inner wall of the syringe, the second member being operable to form a relatively low-pressure seal between the plunger and the inner wall of the syringe and to stabilize the plunger within the syringe; anda third pressure member extending radially outward from the plunger to contact and form a seal with the inner wall of the syringe, the third pressure member comprising a rearwardmost sealing edge and being positioned rearward from the position of the second pressure member, wherein the axial distance between the forwardmost sealing edge of the first pressure member and the rearwardmost sealing edge of the third pressure member is at least 30% of the diameter of the inner wall of the syringe.