An air operated pump and motor unit with a rotor head assembly, an impeller head assembly, and a spacer tube unit disposed between these assemblies. The impeller head includes a pumping chamber and a liquid impeller assembly, and the rotor head includes a rotor housing, a cover assembly, and a rotor...http://www.google.fr/patents/US4732537?utm_source=gb-gplus-shareBrevet US4732537 - Air operated pump and motor
