An electronically controlled, pneumatically actuated pumping system is provided that is especially designed for the precision dispensing of liquids. The system includes a positively actuated inlet valve, and a small-diameter, long-stroke pumping piston that is physically stopped at each end of its stroke....http://www.google.es/patents/US4648533?utm_source=gb-gplus-sharePatente US4648533 - Fluid dispensing system
