A filtration unit comprising a filtration media sub-unit secured in an outer frame. The sub-unit comprises a fibrous filtration media enclosed in an inner frame having an upstream frame element and a downstream frame element. Each frame element has longitudinal and transverse struts and the intersections...http://www.google.com.au/patents/US4668394?utm_source=gb-gplus-sharePatent US4668394 - Filtration media and supporting frame
