Foam pump

A foam pump comprising:

• a pump body (1) having a large air cavity (17), a small liquid cavity (14), a U-shape ring groove (8) formed on a bottom of the pump body (1) and a sucker;
• a large piston (2) located in the large air cavity (17);
• a large piston rod (3) having an air-liquid mixing cavity (15);
• a small piston rod (5) having a support ring (10) and a small piston base (11)
• a spring (9) equipped between the U-shape ring groove (8) and the supporting ring (10) to force the small piston rod (5) and large piston (2) against the large piston rod (3);
• a small piston 4 being slidably disposed on the small piston base (11);
• an over cap (6) having a nozzle, and being arranged for pumping actuation of the large piston rod (3);
• a first double-valve membrane arrangement including a first valve means being formed between the large piston (2) and the large piston rod (3) comprising an engagement of conical sealing surface (18) with conical opening (19) to open and close access of external air to and connecting hole 16, and a second valve means provided between the air-liquid mixing cavity (15) and the large air cavity (17), the second valve means having a sleeve-shape valve plate (21) having a conical sealing surface (24) made of elastic material for engagement with the large piston rod (3) to open and close access of air from the large air cavity (17) to the air-liquid mixing cavity (15) through a plurality of connecting holes (20);
• a second double-valve membrane arrangement including a third valve means being formed by the small between the liquid cavity (14) and the air-liquid mixing cavity (15), wherein a lower end of the small piston (4) engages with a ring groove (12) on the small piston base (11) to open and close access of liquid from the liquid cavity (14) to the air-liquid mixing cavity (15) through groove (13);
• a foam means located in the large piston rod (3) and the over cap (6) comprising a reticulated foam base (25) having a reticulated foam meshwork (26) vertically fixed therein between a lower inlet (27) and an upper outlet (28) of the reticulated foam base (25).