Check valve

A plunger for a check valve and a method for constructing such a plunger. The preferred plunger has a shell of P.T.F.E. sealingly secured to a rigid, metal disk. The cavity between the shell and the disk is filled with a silicone rubber material which, together with the shell, provides a resiliency that enables the shell to conform to irregularities in its mating valve seat even when the seating pressure is low. The shell preferably has an outwardly bowed, tapered sidewall for providing a circumferential line contact with a frustoconical valve seat. In accordance with the method, the shell begins as a sheet that is hot molded around the pre-formed rubber silicone, and the outer edge of the shell is inserted into a groove in the disk to envelope the filler material. The outer diameter of the disk is reduced to sealingly capture the shell edge, thereby forming a unitary structure.