Zero leakage valveless positive fluid displacement device

Abstract

A Positive Fluid Displacement Device (PFDD) with a removable Fluid Displacement Module (FDM) having two opposing pistons connected to a drive block. The drive block slides over a crankpin bearing in assembly to provide orbital piston motion. Opposing cylinders are held within a carriage for reciprocating motion. An opening in the reciprocating cylinder head allows fluid communication to the displacement chamber through inlet and outlet ports in a floating port plate. The flat surfaces of the port plate and cylinder head wipe across each other during cylinder head movement. The piston head carries a protrusion sized to fill the cylinder head opening. Micro-adjustment mechanisms for the position of the cylinder head together with compliant piston and compliant cylinder mechanisms can provide near zero dead volume. Different sized opposing cylinders enable the delivery of pumped fluids in precise ratios. By connecting the outlet of each cylinder to the inlet of the opposing cylinder, the differential displacement of the two cylinders can be pumped, enabling the delivery of very small quantities of fluid. High vacuum may be delivered by series connection of cylinders. The device may incorporate a dual lip piston seal which is wear compensated over the life of the seal. The PFDD is leakage free and can be driven by stepper motors to deliver a precise fluid amount at low speed even to an exact portion of a piston stroke. A sensor is provided for sensing cylinder head position.