Pressurized dispenser having diaphragm enclosed skirted piston

Claim 1

A pressurized dispenser of the type wherein the interior of a cylindrical container is separated into an upper product containing compartment and a lower pressurized fluid propellant containing compartment, a flexible gas impermeable diaphragm having its outer periphery anchored fluid tight within the lower end of said container adapted for separating and isolating said compartments, a downwardly open cup-shaped piston that is stiff enough to be substantially shape retaining with respect to the pressures encountered in said container disposed within said propellant compartment, said piston having a transverse wall portion in full surface engagement with the central region of said diaphragm and a depending cylindrical side wall rigid with the outer periphery of said transverse portion in full surface engagement with a surrounding annular portion of said flexible diaphragm slidably disposed in lining relation against the internal cylindrical surface of said container whereby said piston side wall is spaced from the container internal surface substantially only by the thickness of the flexible diaphragm, the fluid pressure within said propellant compartment constantly urging said piston axially of said container in product discharge direction and acting radially outwardly on said side wall to insure optimum sliding and sealing engagement between the diaphragm and the container wall as the piston may move upwardly under propellant pressure during product dispensing, said diaphragm being of such size and characteristics as to be expansible from a collapsed condition when the product compartment is full to extend substantially The full length of the container for optimum product dispensing.