Apparatus for pumping fluid

A pump head operable with a driving fluid, comprising:

• a pump housing including a moveable element that separates a driving fluid chamber from a pumping fluid chamber, an inlet check valve disposed to allow unidirectional fluid communication of a pumping fluid into the pumping fluid chamber, and an outlet check valve disposed to allow unidirectional fluid communication of the pumping fluid out of the pumping fluid chamber;
• first and second control valves in fluid communication with the driving fluid chamber and selectively operable to establish the driving fluid chamber in fluid communication with a driving fluid source or vacuum;
• wherein the moveable element is a rigid plate, the driving fluid chamber includes a first expandable bellows secured between a driving fluid chamber surface of the rigid plate and a first side of the pump housing, and the pumping fluid chamber includes a second expandable bellows secured between a pumping fluid chamber surface of the rigid plate and a second side of the pump housing;
• wherein the first and second expandable bellows define an axial direction of expansion and retraction;
• and
• wherein the first and second expandable bellows each have a cross-sectional area in a plane perpendicular to the axial direction, wherein a cross-sectional area inside the first expandable bellows is less than a cross-sectional area inside the second expandable bellows;
• wherein the pump housing is open to the atmosphere around the circumferential exterior surfaces of the first and second expandable bellows facing away from the interiors of the first and second expandable bellows and parallel to the axial direction of expansion and contraction, wherein an atmospheric pressure of the atmosphere acting on the larger cross-sectional area of the second expandable bellows assists in pressurizing and displacing the pumping fluid from the second expandable bellows and impedes drawing of the pumping fluid into the pump fluid chamber, thereby requiring a reduced vent or vacuum pressure to fully expand the second expandable bellows;
• and
• a spring disposed concentric to and outside of the first expandable bellows between the driving fluid chamber surface of the rigid plate and the first side of the pump housing, wherein the spring biases the first expandable bellows to expand in the axial direction.