A pump having an improved fluid passage has an inner casing which houses at least one impeller and an outer casing which houses the inner casing. The pump also has a communicating pipe disposed outside of the outer casing for guiding a main flow of a fluid being handled from a space defined in the outer...http://www.google.de/patents/US5888053?utm_source=gb-gplus-sharePatent US5888053 - Pump having first and second outer casing members
