An infusion pump system is described containing a valved cassette which is used as a pumping chamber for conducting fluid from an upstream portion to a downstream portion of the system. The removable cassette contains magnetically biased valves at both ends. Externally mounted magnets bias the valves...http://www.google.com.hk/patents/US4519792?utm_source=gb-gplus-share專利 US4519792 - Infusion pump system
