Graded particle-size retention filter medium for fluid filtration unit with improved edge seal

摘要

A fluid filtration unit having two or more filter medium 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 medium are presently 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 medium layer most proximal to the separator element may be separated from the separator by a support material for supporting such filter medium element and preventing collapsing of the medium into any separator conduit. At least one of the medium elements is formed from a material which swells in size due to fluid absorption with the various zones and the separator being operatively connected by a new and innovative edge seal. The new and innovative edge seal is presently preferably formed from a thermoplastic material having a modulus of elasticity which is sufficient to permit radial expansion of the edge seal when the unit medium swells in size.