Patent ID: 8267284

Claim:
A two-stroke foam pump comprising: (a) a piston housing including a base wall and at least one sidewall extending from said base wall; (b) a piston assembly including: (i) a piston having a base end, said piston being selectively movable in said piston housing from a rest position wherein said base end lies proximate said base wall of said housing to a charged position wherein said base end lies farther away from said base wall of said housing, with movement of said base end away from said base wall serving to define a compressible mixing chamber that expands in volume as said base end is moved away from said base wall, and decreases in volume as said base end is moved toward said base wall, (ii) an outlet passage extending through said piston from said base end to an outlet, said outlet passage fluidly communicating with said compressible mixing chamber, (c) a liquid inlet in said housing communicating with said compressible mixing chamber; (d) a liquid inlet valve regulating fluid flow into said compressible mixing chamber through said liquid inlet, (e) an air inlet separate from the liquid inlet communicating with said compressible mixing chamber; wherein movement of said base end away from said base wall increases the volume of said compressible mixing chamber thus drawing air into said compressible mixing chamber through said air inlet and drawing liquid into said compressible liquid chamber through said liquid inlet, thereby creating a premix of liquid and air in said compressible mixing chamber, and wherein, thereafter, movement of said base end toward said base wall forces at least a portion of said premix of liquid and air through said outlet passage of said piston.