Sequenced adjustable volume pumps, refill units and dispensers

A method of dispensing a foam product comprising:

• moving a valve stem to a first position to open a liquid inlet and allow liquid to flow from a container into a chamber;
• moving the valve stem to a second position to close the liquid inlet;
• forcing air under pressure into the chamber to mix with the liquid while the valve stem is in the second position;
• and
• forcing the mixture to travel through a mix media and be dispensed out of an outlet as a foam.

A gravity fed foam pump comprising:

• a housing;
• a liquid inlet into the housing;
• an air inlet into the housing;
• a valve stem movable within the housing;
• the valve stem movable between a first position that seals off the liquid inlet and a second position that opens the liquid inlet;
• a sealing member for sealing between the valve stem and the housing;
• wherein when the valve stem is in the second position, liquid flows into the housing through the liquid inlet;
• wherein when the valve stem is in a first position the liquid inlet is sealed off;
• and
• air is forced into the housing when the valve stem is in the second position and the air and liquid mixture is forced into a hollow center of the valve stem and is dispensed as a foam.

A self-venting refill unit comprising:

• a container for holding a liquid;
• a pump connected to the container;
• the pump having a housing;
• a chamber located within the housing
• a liquid inlet;
• an air inlet;
• a valve stem movable within the chamber;
• the valve stem moving from a first position that closes off the liquid inlet and a second position that opens the liquid inlet;
• wherein air from the air inlet passes into the chamber and mixes with the liquid and the air and liquid are expelled from the pump as a foam;
• and
• wherein when the valve stem moves to the second position and opens the liquid inlet, air from the chamber flows into the container.