Patent ID: 7011507

Claim:
A pump comprising: an actuator which displaces a movable wall; a pumping chamber whose volume can be varied by the displacement of the movable wall; an inlet flow path through which a working fluid flows into the pumping chamber; and an outlet flow path through which the working fluid flows out of the pumping chamber, wherein the outlet flow path is in constant communication with the pumping chamber even when the pump is in operation, combined inertance value of the inlet flow path is smaller than combined inertance value of the outlet flow path, the inlet flow path is equipped with a fluid resistance element which makes the fluid resistance smaller when the working fluid flows into the pumping chamber than when the working fluid flows out, and a return inlet is installed where the cross-sectional area of the outlet flow path is at least twice the cross-sectional area of the narrowest part of the flow path leading out of the pumping chamber of the pump.