Patent ID: 8499780

Claim:
A cassette assembly comprising: a first cassette, a second cassette and a third cassette, the second cassette interposed between the first cassette and the third cassette, and spaced apart from the first cassette and the third cassette; each cassette comprising a plurality of fluid flow paths and one or more valves, the second cassette being connected to the first and third cassettes by one or more fluid conduits; a reciprocating positive displacement membrane pump pod having an actuation chamber separated from a pumping chamber by a flexible membrane, the pump pod having an actuation port communicating with the actuation chamber and at least one fluid port communicating with the pumping chamber, the pump pod positioned between the first cassette and the second cassette, and the actuation port and the fluid port each communicating with a flow path in one of the first cassette and the second cassette; a fluid flow balancing pod having a first balance chamber separated from a second balance chamber by a flexible membrane, the balancing pod having a first fluid port communicating with the first balance chamber and a second fluid port communicating with the second balance chamber, the balancing pod positioned between the second cassette and the third cassette, each said fluid port communicating with a flow path in one of the second cassette and the third cassette; wherein the pump pod is configured to pump an amount of a first fluid from the pumping chamber into the first balance chamber via the fluid port of the first balance chamber, and the balancing pod is configured to displace a substantially equal amount of a second fluid out of the second balance chamber via the fluid port of the second balance chamber.