Foam dispenser

A foam dispenser comprising a dispensing container with a pressurized propellant gas, a pre-mixing valve with a downstream foaming chamber wherein the pre-mixing valve comprises a valve stem and a pre-mixing chamber with orifices for entry of the pressurized gas, and that a dip-tube is connected to the pre-mixing valve, and a push button for actuating the pre-mixing valve characterized in that a pressure control device for maintaining a constant predetermined excess pressure is arranged in the dispensing container, said pressure control device comprises a first cylinder having an open end and a closed end, and a pressure regulating piston movable within said first cylinder defining a first chamber filled with a gas exerting said predetermined excess pressure, second cylinder defining a second chamber, a passageway from the second chamber to the outside of the pressure control device leading to the container, a pressure regulating valve for opening and closing said passageway, wherein the second chamber being filled with a gas at a pressure higher than said predetermined excess pressure, and said pressure regulating piston having means for actuating said pressure regulating valve dependent from a pressure difference between the first chamber and the container, so that if fluid pressure in the container drops below the predetermined excess pressure, the gas flows from the second chamber to the container until container pressure approximately equals said predetermined pressure.