Filter cartridge with wall surface deformations extending into the medium

Abstract From the Canadian patent

A fluid filter cartridge having spaced inner and outer perforated walls forming concentric chambers. End plates cap the ends of the walls with one of the end plates being centrally apertured to provide a passageway in communication with the inner wall chamber. A filtering media, preferably of cotton and wood fibers is, packed in the chamber between the inner and outer walls. The improvement comprises a plurality of surface deformations in one of the walls preferably the, outer wall, extending into the filtering media toward the other wall. The surface deformations engage and compress the filtering media contiguous thereto to provide filter flow paths from the one wall to the other of a …