Graded particle-size retention filter medium for cell-type filter unit

摘要

A cell-type filter unit having two or more filter media layers and/or zones, at least one of the layers/zones having a different particle retention capability disposed on each side of a non-filtering separator element. The filter media are preferably positioned such that each succeedingly distal filter layer or zone from the separator has a decreased particle retention capability than each proceeding filter layer or zone. The filter media layer most proximal to the separator element may be separated from the separator by a support material for supporting such filter media element and preventing collapsing of the media into any separator conduit.