POSITIVE DISPLACEMENT PUMP HAVING PISTON AND/OR LINER WITH VAPOR DEPOSITED POLYMER SURFACE

摘要

A metering pump for providing relatively small, precise volumes of fluid is provided. The pump piston and/or the interior of the cylinder has a surface finish exhibiting a roughness average within selected limits and a vapor deposited polymer such as polytetrafluoroethylene. A drive mechanism is provided for simultaneously rotating and reciprocating the piston within a cylindrical chamber. Fluid is thereby drawn into the chamber and expelled. The pump can be employed in a dialysate circuit or other fluidic circuits containing crystal or other residue-forming fluids, obviating the need for pump wash ports.