Patent ID: 8454324

Claim:
A membrane pump including: i. an elongate cavity with opposing surfaces and having a length greater than its width and a ratio of width to depth in the range 10:1 to 16:1, where the depth is measured from one opposing surface to a mid-point of the cavity; ii. inlet and outlet passages communicating with the cavity; iii. a pressure port connected to the cavity wherein the pressure port is offset along the length of the cavity; and wherein an exhaust passage is directly connected to the cavity to feed fluid directly from the cavity to the outlet passage, wherein the exhaust passage is formed at the same end of the cavity as the pressure port iv. a pre-deformed non-elastomeric membrane located within the cavity, and substantially coextensive with the cavity; wherein the pre-deformed non-elastomeric membrane: a) has a first stable state in contact with one of the opposing surfaces, the first stable state corresponding to completion of an inlet stage of a pumping cycle; b) has a second stable state in contact with the other opposing surface, the second stable state corresponding to completion of an exhaust stage of the pumping cycle; and c) can be caused to invert from one stable state to the other stable state by application of positive or negative pressure to the cavity via the pressure port.