Multiple air chamber foam pump

A piston pump comprising:

• a piston chamber-forming member (20) extending longitudinally about an axis (23) from an inner end (24) to an outer end (25);
• the piston chamber-forming member (20) defining a central chamber (26) therein coaxially about the axis within an annular chamber wall (27);
• the piston chamber-forming member having a liquid inlet (28) at the inner end (24) in communication with a liquid (14) in a reservoir (13);
• a piston-forming element (22) coaxially slidably received within the chamber (26) in the piston chamber-forming member (20);
• the piston-forming element (22) comprising an elongate tubular stem (90) with a central passageway (63) longitudinally therethrough, the passageway (63) extending from an inner end (134) of the passageway (63) to an outer end of the passageway (63);
• the piston-forming element (22) coaxially slidable within the piston chamber-forming member (20) between an extended position and a retracted position in a cycle of operation comprising a withdrawal stroke and a retraction stroke to draw the liquid (14) from the reservoir (13) via the liquid inlet (28) and discharge the liquid mixed with air through the outer end of the passageway (63);
• a liquid pump (70) formed between the piston chamber-forming member (20) and the piston-forming element (22) proximate the inner end 134 (24) of the piston chamber-forming member 22 (20),
• the liquid pump (70) operative in the cycle of operation to draw the liquid from the reservoir (13) via the liquid inlet (28) and discharge the liquid into the passageway (63) proximate the inner end (134) of the passageway (63);
• an inner air pump (170) formed between the piston chamber-forming member (20) and the piston-forming element (22) axially outwardly of the liquid pump (70) operative in the cycle of operation in a the withdrawal stroke to draw air from the atmosphere and in a the retraction stroke to discharge air into the passageway (63) through an inner air port (142) which extends radially inwardly through the stem (90) into the passageway (63);
• a first outer air pump (270) formed between the piston chamber-forming member (20) and the piston-forming element (22) axially outwardly of the inner air pump (170),
• the first outer air pump (270) operative in the cycle of operation in the withdrawal stroke to draw air from the atmosphere and in the retraction stroke to discharge air into the passageway (63) through a first outer air port (162) which extends radially inwardly through the stem (90) into the passageway 91 (63) at an axial location on the stem (90) spaced axially outwardly of the inner air port (142);
• a first outer air sealing annular flange 203 (231) on the piston chamber-forming member (20) axially outwardly of the inner air pump (170),
• the first outer air sealing annular flange 203 (231) extending from the chamber wall (47) radially inwardly to an annular distal edge (232) in engagement with a radially outwardly directed first outer cylindrical wall (152) on the stem 91 (90) axially inwardly of the first outer air port (162);
• the annular distal edge (232) of the first outer air sealing annular flange 203 (231) engaging the first outer cylindrical wall (152) of the stem 91 (90) to prevent fluid flow axially inwardly therepast,
• a first outer air sealing disc (256) on the stem 91 (90) axially outwardly of the first outer air port (162) and axially outwardly of the first outer air sealing annular flange 203 (231) on the piston chamber-forming member (20);
• the first outer air sealing disc (256) extending radially outwardly from the stem 91 (90) to an annular distal edge (257) in engagement with a first cylindrical outer portion (210) of the chamber wall 47 (27) on the piston chamber-forming member 22 (20) axially outwardly of the first outer air sealing annular flange 203 (231);
• the annular distal edge (257) of the first outer air sealing disc (256) engaging the first cylindrical outer portion (210) of the chamber wall 47 (27) on the piston chamber-forming member (20) to prevent fluid flow axially upwardly outwardly therepast;
• the first outer air pump (270) having a first outer air compartment (271) open to the first outer air port (162) and defined (a) annularly between the stem (90) of the piston-forming element (22) and the first cylindrical outer portion (210) of the chamber wall 47 (27) of the piston chamber-forming member (20), and (b) axially between the first outer air sealing annular flange 203 (231) and the first outer air sealing disc (256);
• in a the cycle of operation in the withdrawal stroke, an axial distance between the first outer air sealing annular flange 203 (231) and the first outer air sealing disc (256) increases thereby increasing a volume of the first outer air compartment (271) and drawing air into the first outer air compartment (271) and, in the refraction retraction stroke, the axial distance between the first outer air sealing annular flange 203 (231) and the first outer air sealing disc (256) decreases thereby decreasing the volume of the first outer air compartment (271) and discharging air from the first outer air compartment (271) through the first outer air port (162) into the passageway (63).