US Patent 7500962 Medical fluid machine with air purging pump

A medical fluid machine includes a housing providing a first wall and a second wall, the first and second walls at least partially defining a pump chamber. A fluid receptacle is located within the pump chamber, the fluid receptacle including first and second flexible membranes configured to be moved apart to accept a medical fluid and moved together to dispel the fluid. A medical fluid outlet is in communication with the fluid receptacle. A first valve arrangement is configured to enable medical fluid in a sufficiently air-free condition to be delivered from the receptacle through the medical fluid outlet to a patient. A second valve arrangement is configured to enable medical fluid with entrained air to be delivered instead from the receptacle through the medical fluid outlet to an entrained air destination.