Controllable liquid dispensing device

A dispensing system for dispensing a quantity of material, the dispensing system comprising:

• an inlet port to receive material;
• an outlet port from which the material is dispensed from the dispensing system;
• a housing including an inner chamber having an adjustable volume, a first opening through which material enters into the inner chamber, and a second opening through which material exits the inner chamber;
• a first valve including a first spring having a spring force to bias the first valve, the first valve being operable in one of an open mode of operation and a closed mode of operation, the first valve being disposed between the inlet port and the first opening in such a manner that when the first valve is operating in the open mode, material may flow from the inlet port through the first opening into the inner chamber, and when the first valve is operating in the closed mode, material is prevented from flowing from the inlet port into the inner chamber, the first valve being controlled in part based on a difference in pressure of material being received in the inlet port and pressure of material in the inner chamber, wherein the first valve operates in the closed mode of operation unless the pressure of the material in the inlet port is greater than the sum of pressure provided by the spring force and the pressure of material in the inner chamber;
• and
• a second valve including a second spring having a spring force for biasing the second valve, the second valve being operable in one of an open mode of operation and a closed mode of operation, the second valve being disposed between the outlet port and the second opening in such a manner that when the second valve is operating in the open mode, material may flow from the inner chamber through the second opening to the outlet port, and when the second valve is operating in the closed position, material is prevented from flowing from the inner chamber to the outlet port, the second valve being controlled in part based on a difference in pressure of material in the inner chamber and ambient air pressure at the outlet port, wherein the second valve operates in the closed mode of operation unless the pressure of the material in the inner chamber is greater than the sum of pressure provided by the spring force of the second spring and the ambient air pressure at the outlet port.