Container having flexible walls and two chambers which are kept separate until the container is opened

Claim 1

Container having flexible walls and a relatively narrow neck separated from the remainder of said container by a transverse wall provided with a central orifice, a plug in said orifice, and external means on said neck for attaching thereto a cap which closes the space within the neck above said separating wall, wherein the improvement comprises a collar along the edge of said orifice, said plug being frictionally retained in said collar and having the form of a cup, the bottom of which cup is directed toward the portion of the container having flexible walls, said plug forming with said wall and collar the sole fluid-tight barrier preventing the passage of liquid from the remainder of said container into said neck, said plug being made of a rubbery material and having an external shape mating with that of the collar, each radial dimension of the plug, when uncompressed, having a length between 1.01 and 1.07 times that of the corresponding radial dimension of the inner wall of the collar, said plug being coated on at least its external surface by a fine layer of lubricant permitting its expulsion from said collar when pressure is exerted on said flexible walls.