dispensing apparatus for use in a pressurized dispensing container comprises a valve mounted in a cup member and an elastomeric vessel forming a collapsible chamber . the vessel is attached to the mounting and depends from the cup cylindrically surrounding the valve body . the vessel is attached to the cup member by having a flange which is thermally bonded to the thermoplastic layer covering the internal surface of the cup member . the flange includes grooves which prevent contamination from sputtering during thermal bonding . the apparatus has application for medical products including edible foam dispensed from containers having an internal fill pressure .