Multi-level, pleated filter array

TLDR: In this article, a multi-level, resin-impregnated, pleated, paper product filter assembly has spaced annular arrays of normally stable, pleats resiliently flexible circumferentially, a helical spring circumjacent between adjacent apices of the pleated arrays to resist collapse of paper product filters due to radial forces between adjacent filter levels and providing two-stage filtration.

Abstract: A multi-level, resin-impregnated, pleated, paper product filter assembly having spaced annular arrays of normally stable, pleats resiliently flexible circumferentially, a helical spring circumjacent between adjacent apices of the pleated arrays to resist collapse of paper product filters due to radial forces between adjacent filter levels and providing two-stage filtration in which the outer filter array comprises a filter pore size effecting first stage filtration of generally larger solids foreign matter, and the second or inner filter array provides second stage filtration of relatively finer foreign particles; in which perforated inner and outer cylindrical shells stabilize the filter cartridge or assembly in which the outer shell includes a plurality of spaced circumferentially disposed series of perforations to equalize pressure over the outer surface of the outer filter element; and in which an end cap and resilient seal combine with the outer and inner shells to coaxially clamp and insure against short-circuiting of the liquid being filtered.