| 摘要 |
<p>A twin check valve pumping system for use with a syringe or other variable volume pumping device for the pumping of liquids. Along a flow path between the check valves, a porous, hydrophobic member is positioned, in communication with a portion of the flow path upstream of the first, inlet check valve. The second, downstream outlet check valve is biased so that pressure in the conduit between the check valves is required for expulsion of liquid. When gas enters the system, such pressure cannot be achieved, because, upon attempted pressurization of the area between the two check valves, the gas passes through the porous, hydrophobic member back to a position upstream of the first, inlet valve. However, aqueous liquids cannot pass through the porous member, and accordingly the device pumps such liquids normally in the absence of gas.</p> |
