Pumping action is performed by a unitary, sealed, easily replaceable pumping element, comprising a housing with a longitudinal axis, a pumping chamber at one end of the housing, an outlet in a wall of the pumping chamber, an inlet in the housing, axially spaced from the pumping chamber, and a circulator...http://www.google.com/patents/US5411378?utm_source=gb-gplus-sharePatent US5411378 - Orbiting fluid pump
