Liquid dispenser for dispensing foam

A pump for dispensing liquid from a reservoir comprising:

• a piston chamber-forming member having an inner chamber and an outer chamber each having a chamber wall, an inner end and an outer end;
• the cross sectional area of the inner chamber being less than the cross sectional area of the outer chamber,
• the inner chamber and outer chamber being coaxial with the outer end of the inner chamber opening into the outer chamber;
• an inner end of the inner chamber in fluid communication with the reservoir;
• a piston-forming element received in the piston chamber-forming member axially slidable inwardly and outwardly therein between an outward extended position and an inward retracted position;
• the piston-forming element having an axially extending hollow stem having a central passageway having an outlet proximate an outer end;
• an inner disk on the stem extending radially outwardly from the stem adapted to engage to the chamber wall of the inner chamber;
• an intermediate disk on the stem extending radially outwardly from the stem adapted to engage the chamber wall of the inner chamber, the intermediate disk spaced axially outwardly from the inner disk relative the inner end of the stem;
• an outer disk on the stem spaced axially outwardly from the intermediate disk and extending radially outwardly from the stem into engagement with the chamber wall of the outer chamber to prevent fluid flow outwardly therebetween;
• a first inlet located on the stem between the outer disk and the intermediate disk in communication with the passageway;
• in the retracted position, the intermediate disk is received in the inner chamber to prevent fluid flow from the outer end of the inner chamber outwardly therepast and the inner disk does not prevent fluid flow between the reservoir and the inner chamber therepast via the inner end of the inner chamber;
• in the extended position, the inner disk is received in the inner chamber to prevent fluid flow from the inner end of the inner chamber inwardly therepast and the intermediate disk does not prevent fluid flow between the inner chamber and the outer chamber via the outer end of the inner chamber.